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3 National Needs for Mesoscale Observations in Five Economic Sectors Chapter 2, along with Appendix A, developed a rationale for spacing and frequency of observations that is appropriate for nationwide weather prediction, climate monitoring, and supporting research. This is the most fundamental application of mesoscale observations in that it seraves many other applications of huge economic import, either directly or indirectly. This chapter exposes the needs for mesoscale observations in five areas vital to the nationâs well-being: (1) energy security, (2) public health and safety, (3) transportation, (4) water resources, and (5) food production. Other areas could have been examined, for example, outdoor recreation or construction, but these five are representative of both the astounding diversity of need and the tremendous value of well-placed and timely observations. For each sector, we note its importance to the national economy, list current assets and operational requirements for mesoscale observations, and highlight the more critical future needs. ENERGY SECURITY Importance to the National Economy Sufficient and reliable supplies of energy are critical to the security of the nation and for sustained, uninterrupted economic growth. To address the meteorological observations needed to support energy security, we first identify the stages comprising the transition from the primary energy source to final consumption. For example, the use of fossil fuels for energy 42
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 43 consumption involves extraction, refinement, transport, conversion, trans- mission (for electricity), and final end use. Meteorological measurements may or may not be needed for decision making during each of these stages. For instance, the use of coal for generating electricity for residential con- sumption is relatively weather insensitive (except for disruption by extreme events) at the extraction, refinement, and transport stages, but is weather sensitive for conversion (load planning), transmission (routing and line exposure to weather), and final end use (weather-driven demand). Recent trends to replace fossil fuels with renewable primary energy sourcesâparticularly biomass, direct solar, wind, and hydroelectricâÂcreate somewhat different transition stages from primary source to final con- sumption and hence somewhat different environmental monitoring needs. Biomass has perhaps the highest vulnerability to weather and therefore the greatest need for weather monitoring, starting with the seasonal weather outlook that favors the planting of one biomass crop over another. Planting, growth, harvest, and transport to consolidation point or conversion Âfacility all present weather-related vulnerabilities not applicable to fossil fuels and call for reliable meteorological measurements and the best-available weather forecasts and seasonal climate outlooks. Direct solar, wind, and hydroelectric power have somewhat different but less complex weather data requirements. In total, renewable primary energy sources call for a wider range of measurements (e.g., soil moisture, direct and diffuse radiation, vertical profiles of wind, snow depth, stream flow, reservoir temperature) at more locations and advances in short-term and seasonal forecasts. In addition, renewable primary energy sources are more vulnerable to extreme events, particularly drought, hail, flood, extreme heat and cold, tornados and hurricanes, than are fossil energy sources. The emerging wind power industry has meteorological observing needs that are similar to other currently unmet needs discussed elsewhere in this report, particularly observations in the lower part of the atmospheric boundary layer above the surface. Wind resource characterization and fore- casting, like chemical weather monitoring and forecasting, requires infor- mation about vertical structure of mean and turbulent wind characteristics and temperature throughout the atmospheric boundary layer, including boundary-layer depth. A 1 percent error in wind speed characterization has an estimated $12 million impact on projected output of a 100 MW wind-power plant over its lifetime. Variability and uncertainty of near-term (diurnal cycle) and long-term future power deliverable from wind farms underscores the need for vertical profiles of relevant variables at a frequency exceeding twice-daily raob schedules. In the energy sector, weather information translates directly into Âprofits and losses on short time scales (minutes to days). Sensitivity of energy demand to climate fluctuations is illustrated by the fact that a fraction of a degree in
44 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Vignette: Duke Power Background Duke Energy-Carolinas generates, transmits, and distributes electrical Âenergy to customers throughout western North and South Carolina. Damaging ice storms in 1996, 2002, and 2005 cost Duke millions in restoration dollars. The most severe ice storm in December 2002 affected a large section of the Carolinas Service Area, caused 1,375,000 customers to lose power, and cost the company $77 million in repairs. That storm resulted in the mobilization of over 11,000 workers from Duke Energy and external companies to repair 3,200 damaged poles, 2,300 transformers, and 549 miles of wire. Because of the huge economic impact of damaging ice storms, power companies take a proactive approach to forecasting, planning, and scheduling resources ahead of such events. Millions of dollars in resource decisions are made before and during an ice storm. Since ice storms are exceptionally damaging and difficult to forecast, real- time mesoscale observations are critical. Two factors affect ice accumulation on trees and power lines: total rainfall and surface temperature (i.e., how far below freezing). Spatial patterns of rainfall and subfreezing temperatures are important in estimating the ice thickness and areal coverage and affect resource decisions for utility management. One recent event underscores the importance of real-time mesoscale observations in making quick resource decisions. 3-1.eps December 2002 ice storm in the Western Carolinas. SOURCE: Nick Keener, Duke Energy. bitmap image
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 45 The Event Numerical forecast guidance from the National Centers for Environmental Prediction (NCEP) indicated the potential for a significant ice storm on February 1, 2007, across portions of the Duke Energy-Carolinas Service Area. Forecast Âmodels indicated the potential of 3/8 to 1/2 inches of ice accumulation beginning in the early morning hours and continuing into the afternoon of February 1. As early as January 29 Duke Energy mobilized its internal workforce and began contacting neighboring utilities and contractors for additional resources in anticipation of sigÂ nificant outages across the service area. During the pre-dawn hours of February 1, freezing rain begin to fall across the area. By mid-morning a light glaze of ice approachÂing 1/8 inch had accumulated. Radar and forecast guidance indicated that freezing rain would continue well into the afternoon and, if temperatures remained below freezing, would result in ice accumulations approaching Â½ inch on trees and power lines before ending. By 10 am on the morning of February 1, Automated Surface Observing System (ASOS) observations showed temperatures rising to near the freezing point. By 11 am the surface temperatures in most affected areas were 32Â°F. Although the latest numerical guidance at that time and the official forecast from the National Weather Service (NWS) still indicated a continuation of freezing rain, it was apparent that milder air was mixing to the surface from aloft and was eroding the shallow wedge of sub-freezing temperatures. Given the real-time ASOS observations supplemented by other surface reports, Duke Energyâs meteorology staff recommended that preparations for significant outages be discontinued, resulting in a significant savings to the company. Real-time mesoscale observations of temperature, dewpoint, wind, pressure, and precipitation are critical to decision making when a temperature change of a few degrees can mark the difference between a cold rain and an ice storm. The former is a nuisance; the latter causes major disruptions. An increase in the spatial coverage of the mesoscale observational network and the availability of 15-minute reports would enable electric utilities, municipalities, and public transportation entities to make better resource decisions, thereby saving money and possibly mitigating impacts from adverse weather conditions.
46 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP mean temperature for planning over a heating season can have huge impacts on profitability. Also, a particular electrical power company will do a daily market analysis for the entire nation (i.e., outside its own service area) and so will need reliable observations and forecasts outside its service area. Current Assets and Operational Requirements for Mesoscale Observations The power-generation industry uses a combination of National Oceanic and Atmospheric Administration (NOAA) products and services together with company-managed observations and in-house forecasting. Company- managed observations generally are intended to increase spatial resolution or timely access rather than to introduce new sensing technologies or to observe different meteorological variables. Below are some examples of measurements and forecast time horizons appropriate for national energy security. Stationary Power Generation â¢ Current observations and short-term forecasts for meeting daily load demand, hourly pricing, and risk analysis for load obligation; â¢ Current observations and short-term forecasts of extreme condi- tions leading to possible interruptions and storm response; â¢ Current observations and short-term forecasts of high concentra- tions of pollutants near the ground as a reason for curtailing operations at coal-fired power plants; â¢ Climatological databases and seasonal forecasts for monthly and seasonal planning for fuel inventories and revenue projections; â¢ Climatological databases, and seasonal and interannual to inter- decadal projections of climate variability and change. Long-term planning for urban and rural development, and industrial and commercial needs (climate scales). Biomass Primary Energy Production â¢ Seasonal climate forecast or outlook for biomass crop choice; â¢ Current observations and short-term forecasts for planting condi- tions (soil moisture, soil temperature); â¢ Seasonal forecasts for projecting crop growth and harvested biomass. Renewable Energy Generation â¢ One-to-three-day estimates of atmospheric turbidity and cloudiness for projections of solar power generation;
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 47 â¢ One-to-three-day estimates of wind speed for estimates of power generation by wind turbines. In the same time frame, icing on the props must be anticipated; â¢ Very short-term forecasts of sudden wind shifts or changes in speed. Turbines must be shut down to avoid damage if wind speeds become too high. Air density forecasts are useful in that density affects the force exerted on props when the wind blows. Needs for the Future Enhanced observations to meet the needs of the power-generation industry would lead to more accurate initial conditions in model forecasts. Similarly, high-resolution observations needed by the Department of Home- land Security (DHS) for running plume models and coordinating emergency response in urban environments would find profitable use on a 24/7 basis in the energy industry. Increased attention to energy security under conditions when foreign sources of primary energy are supplanted by national sources, especially more weather-vulnerable sources such as biomass, will call for more inten- sive weather monitoring and forecasting (short-term and seasonal). At the same time more energy-related measurement platforms may be available for providing new measurements (e.g., wind farm towers, instrumented agricultural machinery, or âsmartâ power transmission line poles in remote areas). More fine-scale information is needed in urban centers. Distinguishing the meteorological factors (temperature, humidity, wind, solar radiation) that influence energy send-out by urban divisions (e.g., residential, indus- trial, commercial, recreational) would facilitate estimation of short-term demand. Real-time surface data should be available from NOAA Port or its equivalent every 15 minutes. Sites that are able to operate and transmit data through outlier events such as hurricanes and severe thunderstorms are critical for damage assess- ments prior to restoration of power, normal communications, and safe travel in the affected areas. Multiple options for communicating the data to a central facility often mark the difference between the loss of vital informa- tion or continued reception. More detail about the spatial distribution of total rainfall over indi- vidual watersheds is needed to manage reservoir storage. In winter and spring, basin-by-basin data on snowpack and the rate of melting enable decisions about reservoir storage and clarify the potential for flooding on large rivers, which affects inland marine traffic. Both remote sensing systems and in-situ observations are needed to characterize the planetary boundary layer over the diurnal cycle. Knowledge
48 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP of the depth of the atmospheric boundary layer is needed to operate con- ventional power generation facilities and wind parks. Detailed observations aloft of temperature, humidity, wind, and suspended Âhydrometeors help to inform resource estimates (wind parks), emergency operations (power out- ages), and curtailment of operations (because of air pollution). Any observations that would improve extended range (seasonal) fore- casts (sea-surface temperatures, temperatures within the thermocline, soil moisture, snowmelt) would immensely benefit the power-generation indus- try, particularly in the production of biomass fuel. A national network of soil-moisture measurements (need not be spa- tially uniform) would benefit several participants in the energy sector. The role of soil moisture as a climate memory for short-term and seasonal fore- casts is well known. Such a network would have a multiplicative Âbenefit, since better observations of soil moisture would improve short-term pre- cipitation (and hence short-term soil moisture) forecasts, which, in turn, would improve seasonal precipitation and soil-moisture climate forecasts. In addition, a network of soil-moisture measurements would benefit stream- flow forecasts, snow-depth forecasts, biomass production estimates, and r Â eservoir-level estimates. When seasonal forecasts achieve a level of accu- racy and quantifiable uncertainty such that they are used routinely in eco- nomic projection models, they have the potential to substantially mitigate negative economic impacts of extreme weather events. One variable not measured by NOAA or other standard networks is the temperature of water discharged from power plants and of adjacent lakes and downstream rivers. Human-caused alterations in natural water temperatures have strong effects on downstream ecology. Influences of weather on the power-generation industry are event driven. Building upon the analysis provided by Schlatter et al. (2005) and follow- ing the methodology we used develop Appendix A, we can summarize the spatial and temporal scales of influences of weather on the power industry (Table 3.1). We can also estimate the measurement resolution (instrument accuracy, spatial resolution, and temporal resolution) needed to meet the needs of the power industry. PUBLIC HEALTH AND SAFETY Importance to the National Economy Safety and health concerns extend beyond the traditional weather issues related to transportation, severe storms, and energy to the important issue of air quality. The chemical composition of the atmosphere has been (and is being) significantly perturbed by emissions of trace gases and aerosols associated with a variety of anthropogenic activities. This changing of
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 49 TABLE 3.1â Spatial and temporal scales of several meteorological phenomena of consequence for the power-generation industry, and the measurement resolution (instrument accuracy, spatial resolution, and temporal resolution) required to adequately observe those phenomena Event Space Time Measurement Resolution Heat wave (temp) 500-1500 km 2 days-1 week 0.5Â°C, 10 km, 1 hr Winda 1-2000 km 1 min-4 days 1 m sâ1, 1 km, 1 min Wind (for wind 100 m-1000 km; 10 min-1 week 0.5 m sâ1, 100 m, 10 min; power) to 1 kmb (1 m sâ1, 30 m, 10min)b Snow and ice 50-1000 km minutes-2 days 1 mm snow water equiv. storms 1 cm snow, 1 km, 30 min Lightning region minutes to hours location to 0.5 km Precipitationc basin to regional Hours-days, 1 mm, 1 km, 1 hr. seasonal to interannual Cloudinessc local to regional daytime hourly 0.1 sky, 10 km, 20 min to monthly Waste heat impact 10 km, lakes and 1 hour-4 days 0.5Â°C, 100 m, 1 h rivers Normal weather urban (2 km) rural 20 min-climate (30 km) aCould be associated with a Norâeaster (4 days), icing conditions, hurricanes or tornadoes (1 min), straight-line winds, or fire weather. bMeasurements in the vertical direction. cCould be from short-term (management) or long-term (planning) for hydropower production. SOURCE: Derived from Schlatter et al. (2005). the chemical composition of the atmosphere has important implications for urban, regional, and global air quality, and for climate change. In the United States, 104 counties are currently in non-attainment with respect to the 8-hour National Ambient Air Quality Standards (NAAQS) standard for ground-level ozone (Figure 3.1). The situation is expected to worsen as we move towards even more stringent standards. Safety and health concerns also extend beyond traditional air quality issues to encompass the effects of heat waves, severe cold, and high pollen levels, and to emergency response to release of hazardous substances, bioterrorism, and fires/smoke.
50 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP FIGURE 3.1â U.S. counties in non-attainment of the NAAQS 8-hour ozone stan- 3-2.eps dards. SOURCE: Scheffe (2007). bitmap image Dealing with public health and safety issues requires an ability to char- acterize and predict chemical weather. By chemical weather we mean âlocal, regional, and global distributions of important trace gases and aerosols and their variability on time scales from minutes to days, particularly in light of their various impacts, such as on human healthâ (Lawrence et al., 2005). As in the field of meteorology, prediction involves both observations and models, and their close integration. The use of chemical weather forecasts in Public Health and Safety (PHS) management has become a new application area and provides important information to the public, decision-makers, and researchers. Many cities in the United States are providing real-time air quality/chemical weather forecasts and various organizations are broaden- ing their services to include prediction of other environmental phenomena (e.g., plumes from biomass burning, volcanic eruptions, dust storms, and urban air pollution) that could potentially affect the health and welfare of their inhabitants. For example, the National Weather Service (NWS) has
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 51 recently started to provide mesoscale numerical model forecast guidance for short-term air quality predictions, beginning with next-day ozone forecasts (available at www.weather.gov/aq), and plans to expand this air quality capability by extending the forecast period and adding fine particulate m Â atter (PM2.5) to the forecasts. Borrowing lessons learned from the evolution of numerical weather prediction (NWP), chemical weather prediction through the assimilation of chemical data holds significant promise. Careful design and use of observa- tions will produce an expanded capability in chemical weather prediction, which in turn will offer benefits in the following areas: â¢ Public health: Accurate time- and location-specific health alerts will help the public reduce acute exposure when high pollution levels are expected. Routine daily forecasts will enable the public to make healthier choices (e.g., exercising outside only on low-pollution days). â¢ Planning: Chemical weather forecasts will allow organizations to plan business activities more effectively. For example, the U.S. Forest Ser- vice and other land management agencies will need these forecasts to ensure their planned ten-fold increase in prescribed burning will not result in viola- tions of the NAAQS. Forecasts can be used by government and industry to reduce emissions on predicted high-pollution days, thus avoiding the high cost of continuous emission controls. â¢ Emergency response and risk management: Effective emergency- response forecasting will help organizations better understand and manage the consequences of accidental or intentional releases of hazardous material into the atmosphere. With that information, they can reduce exposure, both by effective responses (e.g., sheltering-in-place, evacuating) and by planning remedial actions. â¢ Forensics: Identifying the type and quantity of hazardous Âmaterials released into the atmosphere will require not only measurements but also accurate dispersion modeling of plume concentrations and ground deposition. â¢ Wildfires and smoke: Improved prediction of chemical weather will assist air quality agencies in planning controlled burns, as well as aiding firefighters in setting up command posts, managing or fighting fires, and protecting themselves from exposure to smoke. Additionally, the public will benefit from evacuation guidance and protective measures. â¢ Assessments: Chemical forecasting simulations and their Âreanalysis will provide valuable continuous records of air quality and deposition estimates that will inform numerous retrospective assessments such as epi- demiological studies, the progress of air program rules, and delineation of meteorological and emissions influences on air quality.
52 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Current Assets and Operational Requirements for Mesoscale Observations Meteorological Parameters Air quality and related issues depend strongly on the meteorological conditions that effect dispersion and emissions (e.g., wind-blown soil fluxes depend on surface winds, and evaporative emissions depend on tempera- ture). Thus a better characterization of meteorological conditions directly benefits air quality prediction and management. However, there are some important differences in the spatial and temporal requirements for air q Â uality mesoscale observations. Many PHS problems are associated with benign weather (stagnant conditions) and particular phenomena such as urban heat islands, nocturnal jets, local circulations (e.g., sea-land breezes), which have not been the primary focus of observing systems nor NWP efforts (which have been slanted more toward severe storm conditions). Boundary-layer information, including mixing layer height and clouds, is of particular importance. Key meteorological parameters for PHS applications include temperature, wind speed and direction, boundary-layer character- ization, relative humidity, and solar radiation, often at scales of less than a kilometer horizontal spacing (i.e., city-block scale). Pollutant Parameters There are observational needs beyond those of meteorology. Measure- ments of key trace gases and aerosols are required in PHS applications. Many observational networks focus on air quality and related issues and are too numerous to list here. A sampling of air quality networks is pre- sented in the second table of Appendix B Table B.2. Many are operated by the Environmental Protection Agency (EPA). The National Park Service (NPS), NOAA, the Department of Energy (DOE), and the U.S. Forest Service (USFS), state agencies, and tribal governments are involved in the operation of air monitoring networks, and some networks are privately operated by interested industry or research groups (Scheffe, 2007). In addition to the networks summarized in Appendix Table B.2, there are a number of environmental networks comprised of monitors deployed at power and industrial facilities for compliance and other purposes. Examples include those operated by the Tennessee Valley Authority and the Electric Power Research Institute. These networks are developed to meet fairly specific objectives along programmatic lines. Examples include tracking trends of acidity and acid-neutralizing capacity through the surface water Temporally Integrated Monitoring of Ecosystems /Long-Term Monitoring (TIME/LTM) networks, determining compliance with the (NAAQS) in the State and Local Air Monitoring Networks (SLAMs), and establishing vis-
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 53 Vignette: AIRNow Each year in the United States, people with asthma experience more than 100 million days of restricted activity, costs for asthma exceed $4 billion, and approximately 4,000 people die of asthma. (National Center for Health Statistics, 2002). An excellent example of network integration and application is AIRNow, a national air quality notification and forecasting system. AIRNow provides the pubÂ lic with easy access to national air quality information, including air pollution data and maps, air quality forecasts, information about the effects of air pollution on public health and the environment, and actions that people can take to protect their own health and reduce pollution-forming emissions. AIRNow is operated by the Environmental Protection Agency in partnership with over 130 organizations including NOAA, NPS, NASA, National Forest Service, and state, local, and tribal air quality agencies across the United States, Canada, and parts of Mexico. From its humble start 10 years ago in the Northeast as a regional data collection and dissemination system, AIRNow has grown into the âgo-toâ resource for current air quality information by providing daily Air Quality Index (AQI) forecasts and real- time conditions. This voluntary program has grown organically with the integration of air quality and meteorological data from over 2000 monitoring sites operated by more than 130 air quality agencies to provide air quality information in near real time (within 30 minutes of data collection). The AIRNow system receives and quality-checks the data and provides a single access point for health-based information by distributing it via the Internet (www.AIRNow.gov) and e-mails (www.EnviroFlash. info) and to commercial weather service providers who feed media organizations (television, radio, and newspapers) with weather-related information. AIRNow is more than just a system; it is a community working together to protect public health. The management dynamics that evolved and continue to sustain this program and community were recently studied by researchers funded by the National Science Foundation. They evaluated the management and leaderÂ ship characteristics that make some government programs succeed beyond all expectations (Linder, 2007). AIRNow continues to expand its services by distributÂ ing raw data to many other operational and research systems and universities that need access to real-time air quality data. ibility baselines and associated progress in the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. Networks such as UV-Net are focused on solar radiation (ultraviolet [UV], photoÂsynthetically and photochemically active radiation) and provide information on the geographical distribution and temporal trends of radiation for studying the
54 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP effects of UV on biota and materials. Radioactivity is the focus of RadNet, which has stations in each state and is used to track environmental releases of radioactivity from nuclear weapons tests and nuclear accidents. The BioWatch monitoring program, set up by the Department of Homeland Security, is designed to detect the release of pathogens into the air, providing warning to the government and the public health community of a potential bioterror event. The geographical distribution of these sites is shown in Figure 3.2. What emerges from Appendix Table B.2 and Figure 3.2 is that in aggregate there are significant numbers of chemical parameters being observed and used to support a wide variety of important health and safety issues. These observing systems have evolved over the years to reflect national needs. The 1970 Clean Air Act established a framework for the NAAQS and drove the design and implementation of the NAMS and SLAMS net- works in the late 1970s. These networks were intended primarily to estab- lish non-attainment areas with respect to the NAAQS for ozone, sulfur dioxide, nitrogen dioxide, carbon dioxide, lead, and particulate matter (PM). The NAMS/SLAMS networks have evolved over time (Figure 3.3) as a result of cyclical NAAQS review and promulgation efforts leading to changes in the measurement requirements related to averaging times, loca- tions, and the various size cuts associated with particulate matter. Contribution of Satellites Satellite data support various services, including public health adviso- ries, and assist the community by providing data that cover broad spatial regimes in areas lacking ground-based monitors and information in the ver- tical. Satellite products complement existing observational platforms by â¢ detecting fire and smoke plumes, â¢ providing GOES meteorological data and aerosol optical depth retrievals, â¢ providing direct observational evidence of regional and long range intercontinental transport, â¢ enabling emission inventory improvements through inverse modeling, â¢ assisting in the evaluation of air quality models, â¢ tracking emissions trends (accountability), â¢ complementing surface networks through filling of spatial gaps, â¢ supporting development of wildfire and prescribed burning emis- sion inventories.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 55 FIGURE 3.2â The current state of the U.S. air monitoring networks. 3-3.eps Shown are the locations of the sites within various programs, as well as the national bitmap image Appendix Table B.2 for details coverage of specific air pollution parameters. See regarding the NATTS, PAMS, CASTNet, and IMPROVE networks. SOURCE: Draft National Air Monitoring Strategy, EPA Office of Air Quality Planning and Standards, Research Triangle Park, NC, December 2005, available at http://www. epa.gov/particles/pdfs/naam_strategy_20051222.pdf. Needs for the Future General Considerations National needs continue to evolve, and the spectrum of current health and safety concerns bring emerging challenges for observing systems (NRC 2004b). Examples include â¢ developing multiple pollutant integrated management strategies, â¢ assessing and protecting ecosystem health,
56 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP FIGURE 3.3â Evolution of the U.S air network growth. NOTES: TSP = total sus- 3-4.eps pended particulates, PM10 and PM 2.5 refer to particle with diameters less than bitmap image National Air Monitoring Strat- 10 and 2.5 microns, respectively. SOURCE: Draft egy, EPA Office of Air Quality Planning and Standards, Research Triangle Park, NC, December 2005, available at http://www.epa.gov/particles/pdfs/naam_strat- egy_20051222.pdf. â¢ observing multiple spatial scales of interest, from street canyons to intercontinental transport, â¢ adapting air quality management to changing climate, â¢ mitigating pollution effects that may disproportionately affect minority and low-income communities, â¢ growing needs for chemical weather forecast capabilities and emer- gency response applications, which place additional demands for (near) real-time access to data. In general, these PHS applications need access to a broader spectrum of data and more quickly than is currently possible in existing networks. In addition, the need for rapid assessment of PHS impacts from an incident that might occur anywhere in the United States requires data from more locations than are currently monitored. Enhanced Meteorological Measurements to Support PHS Table 3.2 summarizes the major meteorological parameters and the capabilities of current measurement systems that are necessary to meet
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 57 TABLE 3.2â Summary of key capabilities of key meteorological observations to meet public health and safety applications; significant gaps exist in aloft, over-water, and hourly data Measurement Issue Horizontal Vertical Temporal Parameter Resolution Resolution Resolution Air Quality â Surface Fair Good â Aloft Poor Poor Poor PBL Depth â NBL Poor Poor Poor â CBL Fair Fair Poor â MBL Poor Poor Poor Winds â Surface Good Good â Aloft Fair Fair Poor Temperature â Surface Good Good â Aloft Fair Fair Poor Relative Humidity â Surface Good Good â Aloft Fair Good Poor Clouds Good Good Good Precipitation Good Good Pressure â Surface Good Good â Aloft Good Good Good Note: NBL, CBL, and MBL refer to the nocturnal, continental and marine boundary layers, respectively. SOURCE: Tim Dye, Sonoma Technologies, Air Quality Communityâs Meteorological Data Needs, presentation to the Committee. spatial and temporal requirements. The major deficiencies are related to measurements aloft, in urban environments, over water, and in temporal resolution. The design of the mesoscale observing network should reflect the PHS needs for better characterization of planetary boundary layer (PBL) dynam-
58 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP ics and other factors influencing transport and dispersion. Chemical weather predictions play a critical role in PHS management, where they are used by local agencies to issue public health warnings and alerts, and by police and fire departments to respond to hazardous releases. Since the 9/11 attacks, there has been an increased emphasis on developing urban- and building- scale dispersion modeling capabilities and on predicting flows within street canyons at time scales of minutes and distances up to a few kilometers. Recently, an expert working group met to identify and delineate criti- cal meteorological research issues related to the prediction of air quality. In this context, âpredictionâ is denoted as âforecastingâ and includes the d Â epiction and communication of the present chemical state of the atmo- sphere, extrapolation or nowcasting, and numerical prediction and chemi- cal evolution on time scales up to several days. The group emphasized the meteorological aspects of air quality. The resultant report, Meteorological Research Needs for Improved Air Quality Forecasting: Report of the 11th Prospectus Development Team of the U.S. Weather Research Program, (Dabberdt et al., 2004a), identified the needs for enhancing meteorological observations and predictive capabilities that support PHS. These include â¢ improved estimation of the temporal and spatial variability and uncertainty of the height of the PBL; â¢ better parameterization of winds and turbulence above the shallow, surface-based stable layer, and remote sensing of this deeper layer in key areas; â¢ a nationwide observing network to routinely monitor (with high resolution) the diurnal variation of the height and structure of the PBL that exploits and supplements existing measurement systems; â¢ enhancements to numerical modeling of the PBL. Associated meteo- rological observations must be linked with chemical measurements; â¢ improved depiction of seasonal and interannual vegetation varia- tions that are important for dry deposition; and â¢ more realistic model treatment of spatial and temporal variations in soil moisture and better soil moisture initializations. Observations to Better Characterize the Chemical Nature of the Atmosphere Although Figure 3.2 shows many sites that measure the chemical com- position of the atmosphere, there is poorer network coverage in rural areas, in part because the measurements were designed mainly to test for compliance with regulatory standards of concentration, not to increase predictability of air quality or to respond to emergencies. The latter two functions require broad spatial coverage to initialize models and to assess
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 59 contributions from long-range transport. That the instruments used to measure a given parameter are often different compounds the problem. For example, while the North American networks have deployed over 1000 routinely operating continuous PM2.5 mass samplers, the use of dif- ferent instruments with different errors and sensitivities makes it difficult to combine the datasets. Major gaps exist in terms of spatial, temporal, and parameter coverage. For example, while greater than 95 percent of air pollutant mass is located above 100 m, 95 percent of the measurements are made near the surface. Observations of pollutant levels above the surface are important because significant amounts of material are transported above the surface before being brought near the surface to impact human and ecosystem health. The vertical measurements generally focus on the meteorological parameters that affect the mixing and transport of pollutants, not on the concentra- tion of polutants. A main source of vertical information, the radiosonde network (with an ozone monitoring component at a few sites), lacks the necessary temporal resolution to adequately characterize diurnal develop- ment and collapse of the PBL. The Photochemical Assessment Measurement Stations (PAMS) program and other air agency efforts support a network of radar profilers that provide highly resolved wind profiles, but the national coverage is very limited. Details regarding vertical measurement capabilities are discussed in Chapter 4. The above facts severely limit our ability to characterize and predict chemical weather. Recommendation: To meet national needs related to public health and safety, including the growing need for chemical weather forecasts, a core set of atmospheric pollutant composition parameters should be part of the mesoscale observing system. The core set should include carbon monoxide, sulfur dioxide, ozone, and particulate matter less than 2.5 microns in size at approximately 200 urban and rural sites (~175 km spacing). These observations would constitute a national backbone of urban and rural sites and should be especially effective in enabling chemical weather prediction when collocated with surface meteorological observations and related vertical profiles (as discussed in Chapter 4). The identified param- eters play important roles in chemical weather forecasting applications, can be measured effectively at the scale and locations of the mesoscale network, and can be measured or inferred (e.g., PM2.5 and aerosol optical depth) from satellites. For these species, the satellite observations can be used to provide additional information regarding the spatial distributions of the pollutants. Additional important parameters (e.g. NO2) should be added
60 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP as soon as appropriate and as affordable technology is developed for the applications envisioned. This aspect of the mesoscale network could build upon EPAâs proposed National Core Monitoring Network (NCore). NCore was developed in response to the National Research Councilâs (NRCâs) Air Quality Manage- ment in the United States (NRC, 2004b). The NCore framework, as shown in Figure 3.4, is a tiered system consisting of three different levels of obser- vations. Level 3 is designed to provide broad spatial coverage of a single pollutant. The Level 2 design includes deployment of 75 surface stations in a ârepresentativeâ mix of urban and regional areas with a spectrum of measurements to meet multiple needs, including constrain regional model evaluation, link to satellites, and service accountability and epidemiological studies (not compliance sites). Level 1 consists of a small set of advanced sites where new measurements are needed to serve science and technology transfer objectives. The network design addresses many of the shortcomings identified earlier in this section for near surface observations, including the identification of key meteorological and pollutant information. It is impor- tant to note that the 75 Level 2 NCore sites are not adequate from a spatial coverage perspective, but are intended to foster additional deployment of collocated measurements as their utility is demonstrated. A national net- work designed to meet the spectrum of PHS applications requires compo- sitional capabilities at 200 sites with a core set of parameters that should include carbon monoxide, sulfur dioxide, ozone, and particulate matter less than 2.5 microns in size. These compositional observations should be especially effective in enabling chemical weather prediction when collocated with surface meteo- rological observations and related vertical profiles. Currently, the NCore plan does not map out a strategy for the inclusion of profiling information from lidars or aircraft. In the national mesoscale network these observa- tions should be collocated with the vertical profile observations, as covered in detail in Chapter 4. Integrating Surface- and Space-Based Chemical Observations Gaps exist in mesoscale observing networks that limit the ability to integrate surface- and satellite-based systems for the mutual improvement and leveraging of both systems in characterizing boundary-layer air Âquality. In order to enable the integration of satellite observations with surface v Â alues, the surface-based network must contain surface and Âboundary-layer information on the same species that is observed from satellites. Emphasis should be placed on providing precision surface measurements of the satel- lite column species that are well retrieved (ozone, PM optical depth, sulfur dioxide, nitrogen dioxide, carbon monoxide, Âformaldehyde, and glyoxal),
Level 1 . 3 - 10 Master NCore Measurements Sites Comprehensive Measurements, Level 2: ~ 75 Multi - Advance Methods pollutant (MP) Serving Science and Sites, âCore Speciesâ Technology Transfer Plus Leveraging From L1 Needs PAMS, Speciation Program, L2 Air Toxics Level 3 : Minimum Single Pollutant Sites (e.g.> 500 Level 3 sites each for O3 and PM2.5 and related spatial Minimum âCoreâ Level 2 Measurements Mapping Support Continuous NO,NOy,SO2,CO, PM2.5, PM10/PMc,O 3, Meteorology (T,RH,WS,WD); Integrated PM2.5 FRM, HNO3, NH3, FIGURE 3.4â The NCore network design. NOTE: PAMS refers to the Photochemical Assessment Monitoring Stations Program, PMc to the coarse size fraction of particulate matter, and FRM to the federal reference method for fine particle measurements. SOURCE: Scheffe (2007). 3-5.eps map is bitmap image remainder is vector BROADSIDE 61
62 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP in order to provide validation for the Âsatellite-derived data (Tinkle et al., 2007). Presently only the first three species have broad coverage in the sur- face observations. Thus there is a need for expansion of key ground-based measurement systems that offer leveraging of satellite data. Some but not all of these species are included in the planned NCore sites discussed above. Space-based observations of chemical constituents in the lower tropo- sphere are hampered due to the opacity of the atmosphere in the ultraviolet from Rayleigh scattering, and the limited vertical resolution of infrared retrievals near the surface. Thus mesoscale observations are essential in characterizing the composition of the lower atmosphere. Observations in Urban Areas: A Special Case Based on current census data, over 75 percent of the U.S. population lives in urban environments (in cities with more than 200,000 people). The hazards of pollution and terrorism make the requirements for mesoscale observing in urban environments more demanding than those discussed elsewhere in this chapter. The needs for observations at the street canyon level are obvious for some of the agencies that sponsored this report, but review of the cross-cutting nature of the other societal benefit areas has not made urban-scale observing an obvious candidate for enhanced network development. Recommendations from an NRC report on homeland secu- rity (NRC, 2003a) identified the need for increased observations, designed to systematically characterize local-scale wind flow patterns (over the full diurnal cycle) in areas deemed to be potential terrorist targets, with the goals of optimizing fixed observations and educating those involved in developing dispersion forecasts about local flows and model strengths and weaknesses. Committee discussions with DHS revealed that improved modelÂing of airflows at rooftops (i.e. better prediction of the external forcing of weather on the urban area) was the most demanding require- ment from a mesoscale observing system. With such boundary condition information available, DHS would rely on separate models of street canyon airflow and street canyon deployable instruments (many of which could not be discussed with the Committee). The required number of observa- tions in an urban environment could be so large that the network models that are being considered for other mesonet structures would most likely be insufficient and would drive responsibility for such observations into the federal realm, where significant resources and directed programs could best manage these needs. In a similar vein, transportation accidents (air crashes, train derail- ments, hazardous cargo spills, port spills) also require inputs of weather information at the finest spatial and temporal scales, as addressed by the
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 63 NRC in its report on dispersion of hazardous wastes (NRC, 2003a). Con- founding these important PHS applications is the fact that the source function is a key driver, yet its location and intensity are often poorly constrained. This places additional requirements on the observing systems. The agencies that are required to respond to such events have indicated that rapidly deployable sensors that could be mobilized to provide additional transient information are a major need. The prototype RAWS observations, deployed around wildfires or special events where public safety could be threatened, serve as one example. Further discussions of the specific chal- lenges and needs for urban applications are presented in Chapter 4. Integration across Networks for Enhanced Applications Meeting the multiple needs of health and safety requires increased efforts to integrate the observations, with the primary objective of provid- ing more timely and effective access to ambient monitoring data. Observa- tions from air quality networks serve multiple purposes. For example, data from these networks are used for characterizing the current environmental state, parameterizing physical/chemical processes, tracking changes (trends) in environmental conditions, developing causality associations between observations and responses, issuing public alerts, and providing inputs to and evaluation data for models. These applications often require the data user community to weave together information from disparate networks, despite recognized spatial, temporal, and compositional gaps. However, there are barriers and challenges to integration across net- works. They include accessibility issues, including the emerging need for near real-time data to support forecasting and emergency response; quality issues, including the need for metadata and quality assessment; and human issues, including concerns and incentives to share data. Integration can occur by a number of actions, including adjustments in quality assurance protocols and harmonization of platforms through a combination of instru- ment modifications and correlation techniques. TRANSPORTATION Importance to the National Economy This section focuses on three major modes of transportation: (1) land transportation, which includes highways (passenger traffic and trucking) and rail; (2) air transportation, which includes commercial airlines (pas- senger and cargo) and general aviation; and (3) marine transportation (large ships, port operations, and recreational boating).
64 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Highway Transportation The impact of weather on land transportation is enormous. More than 230 million commercial and passenger vehicles on U.S. roads are driven nearly 3 trillion miles annually. Statistics from the Federal Highway Admin- istration indicate that â¢ 1.57 million weather-related crashes occur per year, resulting in 7,400 fatalities (more than 10 times the death toll directly associated with lightning, tornadoes, floods, hurricanes, heat, cold, and winter storms com- bined) and 690,000 injuries; â¢ weather accounts for 24 percent of all crashes; â¢ weather causes 25 percent of non-recurrent delays on freeways and 1 billion hours per year of system delay; â¢ weather-related delays add $3.4 billion to freight costs annually; â¢ âjust-in-timeâ manufacturing and warehousing means that trans- portation delays propagate quickly into industrial losses; â¢ emissions add substantially to greenhouse gases; â¢ chemical anti-icing and de-icing materials for snow and ice control affect watersheds, air quality, and infrastructure. Rail Transportation The effect of weather on rail transportation is also significant. Freight railroads are overwhelmingly privately owned and are only minimally sub- sidized by the government, but they move about 40 percent of the nationâs freight as measured in ton-miles. Their major competitors in moving freight are trucks and barges. Railroads moved about 12.3 million truck trailers or containers in 2006. U.S. freight railroads employed 187,000 workers at the end of 2006 and generated revenues of $48 billion. The weather impacts on rail transportation are as follows: â¢ The most serious and costly impact centers on track washouts. Just minor washouts can cause several million dollars in damage. â¢ The greatest rail losses in U.S. history were caused in 1993 by â Paul Pisano, Road Weather Manager, Federal Highway Administration, Washington, DC, 2007. â Average number of fatalities from 1988 through 2003 from the indicated weather hazards as tabulated at http://www.hprcc.unl.edu/nebraska/weather-related-fatalities1940-2003.html. Ultimate source: NOAAâs National Climate Data Center and the National Weather Service. Does not include Hurricane Katrina in 2005. â Association of American Railroads, âOverview of U.S. Freight Railroads,â January 2007. The document is available at http://www.aar.org/PubCommon/Documents/ÂAboutTheIndustry/ Overview.pdf.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 65 main-stem flooding along the Missouri, Mississippi, and other large rivers. Many miles of track lie within the floods plains of these and other rivers. The railroads spent $4.8 billion for repairs. â¢ The direct cost of a derailment from any cause, track failure being the most common, is approximately $400,000, but the indirect costs of loss of lading, train delays, or train rerouting can double that amount. â¢ Delays due to weather-related problems have significant impact. Railroad revenues are influenced by the demand for energy and the yield of agricultural productsâboth have a high correlation to the weather. The Association of American Railroads reported in 2000 that coal and agricul- tural products contributed 21 percent and 8 percent, respectively, to total rail industry revenues. Due to this commodity exposure, railroad revenues often move up and down with the market for these products. Delivery delays are costly. â¢ Unexpected low visibility caused by fog, smoke, dust, rain, snow, or other atmospheric obscurants along railways and roadways is respon- sible for many accidents annually. Air Transportation The impact of weather on the air transportation sector is perhaps more obvious than the other sectors. U.S. airlines employ over 600,000 people. Commercial aviation helps create and sustain more than 10 million jobs and supports approximately 8 percent of the U.S. gross domestic product through its connection with other industries, particularly travel and tour- ism. Passenger-miles flown on U.S. carriers surpassed 500 billion in 2003. Passengers boarded a plane over 740 million times in 2006. Air freight amounted to nearly 40 billion ton-miles in the same year. The primary impact of weather on air transportation is delays. Weather and air traffic control delays, which are highly correlated accounted for about 66 percent of all delays in 2006, according to Federal Aviation Administra- tion data. Nearly half a million delays in 2006 cost the airlines approximately $6 billion and passengers approximately $10 billion. (The Department of Transportation estimates that each minute of delay costs $62 per aircraft.) Aircraft accidents for which weather is a contributory cause account for roughly $42 million in annual losses from aircraft damage and personal injury. This figure is inferred from examination of the accident database of â Stan Changnon, Illinois Water Survey, University of Illinois, Champaign, Illinois, 2007. â Burlington Northern Santa Fe Railroad, 2007. See http://www.zetatech.com/bnsf_rts.htm. âWeather Information for Surface Transportation Report, FCM-R18-2002, Appendix E, Office of the Federal Coordinator for Meteorology, Washington, DC, 2002. âU.S. Department of Transportation Bureau of Transportation Statistics, 2007
66 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP the National Transportation Safety Board. However, the potential losses, even from a single major accident, can be much greater, over $1 billion, due to insurance claims. Marine Transportation Nearly 80 percent of freight tons in U.S. foreign trade are moved by ship. Ships moved 1.49 billion tons in 2005, of which 0.39 billion were for exports and 1.10 billion were for imports. The total value of these goods was $1.12 trillion. Nearly half the international cargo can be considered hazardous, notably when spilled over water. Marine weather claims encompass a wide spectrum of offshore and littoral weather-related mishaps, ranging from a salvage operation gone wrong, to cargo loss/damage, and even the injured crew member. The common thread governing many marine claims is the exact role weather or sea played in the alleged loss. No other industry emphasizes safety quite like those with marine concerns. There is a complex interdependency of vessels, waterways, terminals, support services, and intermodal connecting infrastructure that moves people and freight in a safe, efficient, and envi- ronmentally sound manner. Weather impacts just-in-time delivery. The weather affects route con- ditions, times of departure or arrival, and ports of refuge. Tropical storm avoidance is critical for marine transportation. Other areas that are vulner- able to weather are coastal trade (shipping over short routes near the coast); commercial port operations; the fishing industry; recreational boating; NOAA fisheries management; US Coast Guard Search and Rescue (SAR) and port security operations; and emergency response (e.g., oil spills). Port operations present a unique set of challenges. A large vessel usu- ally holds position a few miles from breakwater. A pilot boards the ship, calls in tugs, and directs the ship to a safe berth, whether it is a breakwater anchorage or a dock. The width and depth of the channels and the height of any bridges across the channels dictates the size of the ship that can be brought to port. Any sharp bends in the channel and the length of the dock limit the length of the ship that can be accommodated. Very large ships such as 300,000-ton, 1,200 feet long tankers have a very large draft (>60 feet) and are more affected by current than wind. Delays in docking are costly. Even if weather unexpectedly prevents transit to the dock, long- shoremen still have to be paid for showing up (typically tens of thousands â Source: U.S. Department of Transportation, Research and Innovative Technology Admin- istration, Bureau of Transportation Statistics, August 2006. Available at http://ops.fhwa.dot. gov/freight/freight_analysis/nat_freight_stats/docs/06factsfigures/fig2_6.htm. â Interview with Vic Schisler of Jacobsen Pilot Services, Inc., Long Beach, California.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 67 of dollars); the shipper may lose $100 thousand for each day the ship must spend offshore. Current Assets and Operational Requirements for Mesoscale Observations In the highway environment, most road-specific information is avail- able because of collaborations between state departments of transportation (DOTs) and service providers in the private sector. Most roadside meteo- rological observing stations measure temperature, wind, precipitation, and humidity. Many states also use sensors embedded in the road surface that measure temperature and detect ice, chemicals, or water on the road, and subsurface sensors that determine heat flux. Roadside cameras show how weather is affecting traffic and either substitute for automated observations or give visual confirmation that the pavement measurements are valid. New technology provides remote sensing capabilities from the roadside for road conditions and surface temperature. Some sites also have visibility sensors.10 Both the DOTs and their weather service providers use data from these sources to monitor current road conditions and as the basis for web-based products. Roadway forecasts are much more demanding of observations than the monitoring function; they rely upon not only roadway sensors but also all other types of observations, surface and aloft, from an area that grows with the length of the forecast. State DOTs operate the Road Weather Information System (RWIS).11 The RWIS relies on a great majority of 2500 state-owned Environmental Sensor Stations (ESS) that collect one or more types of data along road- ways: atmospheric (usually temperature, pressure, wind, humidity, and precipitation), road surface (pavement temperature, presence of water or ice, whether the pavement wet or dry, and sometimes the concentration of chemicals on the pavement), and water depth (measurements in streams or culverts that cross under the highway). Communications for the collection of roadway data and a central processing and dissemination center are integral parts of the RWIS. As with many mesonets, the reliability of state DOT data is variable with regard to documentation (metadata), adherence to siting standards, and regular maintenance and repair of sensors. Proposed standards for siting and communications are in a Federal Highway Administration pub- lication (Manfredi et al., 2005).12 Some agencies do not share road sensor 10â More information on all these sensors is available at http://ops.fhwa.dot.gov/Weather/ best_practices/EnvironmentalSensors.pdf 11â See http://ops.fhwa.dot.gov/Weather/faq.htm. 12â Available at http://ops.fhwa.dot.gov/publications/ess05/ess05.pdf.
68 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Vignette: Ice Storm in the Columbia River Gorge The most severe snow/ice event in recent years in northwest Oregon and southwest Washington occurred early January 2004. Portland International Airport closed for nearly 3 days, as did all major highways into and out of Portland. This included north-south Interstate 5 in southwest Washington and Northwest Oregon, Interstate 84 east of Portland along the Columbia River Gorge, and Interstate 205, which runs north-south just east of Portland International Airport. The numerical weather prediction models continually tried to dislodge the cold air trapped in the low-lying Willamette Valley and between the coastal mountains and the Cascades in southwest Washington. Scouring of the cold air never happened; therefore liquid precipitation falling into the entrenched cold air near the surface either froze to ice pellets or froze upon contact with the ground. Ice storms are not uncommon in the Portland area, and forecasters usually expect the cold air to remain in place longer than the models predict, but sometimes even forecasters underestimate the staying power of the cold air. Because of the complex terrain in the Pacific Northwest and the immense impact of cold low-level flow out of the Columbia River Gorge on winter weather, a denser observation network would be a great help, especially if forecasters could get more information in the vertical. Frequent vertical temperature profiles near the mouth of the Gorge would show how cold air domes erode during cold easterly surface flow. With accurate forecasts of ice storms, crews could treat the roads in timely fashion, and ordinary drivers could plan in advance to stay at home. Winter-weather-affected traffic in the Portland, Oregon, area, January 6, 2004. 3-6.eps SOURCE: National Weather Service, Portland, Oregon. bitmap image
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 69 information with the traveling public because of liability concerns; this is especially true with road surface temperature and surface condition data. In an effort to coordinate the collection of roadway meteorological information nationwide and to gather comprehensive metadata about the roadway sensors, the U.S. Department of Transportation has established the Clarus system.13 Not an acronym, clarus is the Latin word for âclear,â a road condition universally hoped for. During the next few years, the Department of Transportation intends to develop and demonstrate Clarus as an integrated observation and data management system for the improve- ment of surface transportation. The success of Clarus will depend upon the involvement and cooperation of state DOTs and the private sector. Clarus should lead to more accurate assessments of weather and pavement condi- tions and could improve short-term forecasts of road weather, thereby alert- ing drivers to near-term hazards, whether from winter storms or summer flooding. State DOTs will benefit in that road-clearing operations will not be launched unnecessarily. Railroads have specific observational needs. These include â¢ precipitation (frozen and liquid) for rails or overhead power lines. Any accumulation of ice on tracks seriously affects braking and makes it impossible for trains to start moving; â¢ thunderstorms and lightning; â¢ high or low temperatures (85Â°F or above, 32Â° or below). High tem- peratures cause rails to bend and trains to derail; low temperatures cause switches to freeze and stick; â¢ visibility less than 3 miles. Poor visibility from any cause (heavy rain or snow, fog, blowing dust) is a problem. Engineers depend upon see- ing the tracks and signals ahead; â¢ high winds (for blown debris and crosswinds in excess of 60 mph). Railroads or their service providers have installed sensors along the tracks to monitor weather conditions and warn of the above hazards. The Federal Railroad Administration (FRA) believes that new moni- toring technologies will prevent collisions and accidents involving exces- sive speed, provide greater security, increase railroad capacity and asset utilization, improve service to railroad customers, improve railroad energy efficiency and emissions, enable railroads to measure and manage costs, and increase railroad economic viability and profits.14 13â See http://www.clarusinitiative.org/background.htm. 14â Steven R. Ditmeyer, Weather Information and Intelligent Railroad Systems, NCAR-FRA- ARA Symposium on Enhanced Weather Information for Improved Railroad Safety and Pro- ductivity, Boulder, CO, October 2001.
70 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Many costly aircraft delays result from poor weather at the terminal. Standard instrumentation, typically the NWS ASOS and the FAA Auto- mated Weather Observing Systems, provides the local observations used in decision-making and terminal forecasting. Most airports that experience substantial winter snowfall employ instrumentation similar to roadway sensors to monitor runway conditions. Specialized observing systems such as radar (WSR-88D and the Ter- minal Doppler Weather Radar) provide detailed observations of the atmo- sphere, especially for severe weather that can affect air transportation at or near airports. Major airports benefit from the Low Level Wind Shear Analysis Sys- tem, which provides critical wind information when downbursts (strong, sudden gusts of wind from convective showers) pose a hazard for departing and arriving aircraft. Sudden drops in airspeed caused by downbursts can cause aircraft on final approach to land short of the runway, and aircraft accelerating for takeoff to roll off the end of the runway without becoming airborne. Systems such as the Aircraft Icing Weather Support to De-icing Deci- sion Making (WSDDM) are being deployed at airports to provide aircraft de-icing decision support. Developed by scientists at the National Center for Atmospheric Research, the WSDDM system is based on a complex system of temperature and weather prediction sensors and radar that are controlled and monitored by state-of-the-art software. The sensors for the system are usually installed up to 30 km from the airport in all directions. The WSDDM systemâs sensors measure temperature, atmospheric pressure, dew point, and wind speed and direction. A hot-plate snow gauge measures the liquid equivalent of snowfall, the most important parameter for decid- ing which de-icing fluid to use and how much time pilots have between leaving the de-icing station and takeoff. Marine transportation typically requires information about wind speed and direction, swell/wave heights and direction, and tropical weather. Except for ship reports, few surface observations are available for opera- tional decision-making. Automated reports from marine buoys provide input to forecasts, and satellite observations of sea state and surface winds (inferred from scatterometer data) have been widely used in the near-shore environment. However, recent cancellation of satellite missions calls into question the continuity of such offshore satellite measurements until new missions are launched. Port operations require good information about water depth (increas- ing ship draft over the years), tidal current, salinity, wind velocity, sea state, wave heights and direction, and the air gap between structures over water and the water itself in order to avert collisions between vessels and structures.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 71 NOAAâs Physical Oceanographic Real-Time System (PORTS) provides critical information for shipping operations at 15 major U.S. ports. PORTS has three major objectives: first, ensure safe navigation in the vicinity of ports, that is, prevent collisions among vessels and between vessels and fixed objects. Second, conduct maneuvers and docking as efficiently as pos- sible, given the constraints of channel width, water depth, bridge heights, and weather. Third, protect the coastal environment, mainly through the prevention of accidents. Coastal waters provide habitat for diverse biological resources, includ- ing the spawning ground for 70 percent of commercial and recreational fisheries in the United States. Maritime accidents involving oil spills stifle biological life forms for years. Clearly, weather and water sensors are an integral part of PORTS.15 Needs for the Future In the mountainous West, avalanches are a significant wintertime threat to highway users, as well as to recreational activities on backcountry trails. Better snowfall, temperature, and wind data in the high mountains would lead to more effective warnings, enhance avalanche control capabilities, and reduce the number of unexpected highway closures. Snowfall measurements along highways leave much to be desired. Precipitation gauges have known deficiencies in measuring the water con- tent of snow, because of losses from evaporation at low snowfall rates, and because wind reduces the capture of snow within the gauge orifice. The character of the snowfall is usually unknown. Heavy, wet snow is less prone to drifting, but wind can easily clear fluffy, low-density snow from the roadway or deposit it in huge drifts, making for huge variations in road conditions in very short distances. The difficulty in measuring the character of snow and its accumulation rate in terms of liquid equivalent (relevant to salting operations) is often the greatest reason why the predic- tion of future pavement conditions, even an hour or two in advance, fails. Quite apart from the wind, mesoscale variability in snowfall rates due to convection embedded within larger-scale snowstorms, banded lake-effect snowfalls, and proximity to rain-snow boundaries argues for more closely spaced measurements along roadways and more innovative measurement technologies for measuring snow. Certain observations such as soil moisture and soil temperature are rarely available; yet they are critical in forecasting pavement temperature, frost heaving of roadways, and the potential for load restrictions. 15â For further information, see http://tidesandcurrents.noaa.gov/ports.html.
72 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Solar radiation data, rarely measured in the operational environment, are especially important for road surface and rail track temperature forecast- ing. Sky view information also aids in forecasting pavement temperature. Pavement temperature reacts markedly to variations in the sky view, whether due to road cuts, buildings, mountains, or vegetation. Some agencies have removed vegetation along rights of way or in interstate highway medians in order to increase the absorption of solar radiation by the pavement. For highway, rail, and air transportation, additional data are needed for improved fog forecasting, including: â¢ the vertical distribution of humidity in the potential fog layer (Âsurface-200 meters) â¢ winds in the stable boundary layer â¢ the ground temperature of the surface beneath the potential fog layer â¢ cloud cover, precipitation, surface dampness, and temperature Strong winds affect ground transportation directly. High-sided vehicles and rail cars with double-stacked containers are susceptible to blow-overs. Trucks have been blown off of bridges. More accurate local forecasts of high winds are needed along with more effective methods of alerting truck drivers. Just automated signage based on a local observation can provide sufficient warning. Finding: Many existing surface observing platforms are in place to enhance the safety of road and rail transportation. Some of these s Â tations are installed in locations prone to hazards, for example, early icing on bridges, early morning fog in low spots, blowing dust in the vicinity of bare ground and fine-grained, loose soil. Other stations are in more broadly representative locations. In both cases, such data are valuable to the mesoscale forecast and warning enterprise. Lower troposphere and boundary layer data, such as vertical profiles of wind and temperature, are needed by all transportation sectors. Relatively few data are currently available from the standpoint of resolving mesoscale features. Temperature profiles have been shown to be extremely valuable in detecting the melting level in the lower atmosphere. This information is especially useful in deciding how much snow and ice might accumulate on roads. While continuing to satisfy the fundamental needs of the transporta- tion sector, some existing roadway and railway observing stations could easily be integrated into the network of networks to provide a broader complement of meteorological and soil measurements at minimal cost.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 73 The addition of another measurement or two at existing sites avoids the major expense of establishing a new station altogether, and wireless com- munication gives the flexibility to locate individual instruments optimally. Likewise, meteorological stations near roads and railroad tracks could have sensors added that would benefit transportation, for example, water depth measurements near culverts. Recommendation: Existing surface observations and observing plat- forms associated with road and rail transportation, as appropriate, should be augmented to include World Meteorological Organization (WMO)-standard meteorological parameters. Conversely, existing WMO-standard meteorological observing stations near highways and railways should be augmented, as appropriate, to meet special needs of the transportation sector. In the coastal boundary layer, energy and momentum exchanges are occurring that need to be measured in order to understand, monitor, and predict mesoscale atmospheric and related environmental processes. Sea-surface temperature must be more effectively measured in order to improve forecasts. Near-shore water surface temperatures often dis- play strong spatial and temporal variations due to multiple processes such as tidal perturbations, upwelling, wave action, runoff, and diurnal heat- ing. Latent and sensible heat exchanges are critical for gauging mesoscale hydrologic processes, such as coastal convection and stratiform precipita- tion, fog development, sea breeze occurrence and intensity, tropical storm intensity, and the rain/snow line in coastal winter storms. Satellite Âretrievals are improving the measurement capabilities, but the quickly fluctuating processes, intricate coastal boundaries, and near constant cloud cover in some near-shore environments still require the need for more in-situ observations. Other parameters besides sea-surface temperature should be measured within the littoral zone water column, for example, water quality, turbidity, sediment transport, salinity, and nutrient production. The measurement of wave action is complex and very much governed by mesoscale features within the coastal zone. Many end users require the measurement of wave heights, often broken into dominant and sub- dominant values based on wave period. Longer period waves, often termed swells, are generated by offshore storms, whereas locally wind-driven waves are often termed chop and have much shorter periods. Wave direction is a much desired parameter but more difficult to measure. A subset of buoys along the U.S. coastline collects this information. Many stakeholders in the coastal zone request measurements from tide gauges, water-level gauges, and current meters. The U.S. tidal gauge net-
74 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP work is comprised of over 500 stations, many of which also collect some meteorological information. Buoys have been and continue to be the cornerstone platform of littoral and open ocean observing, with satellites becoming more and more of use due to the large spatial expanses they are able to sense. Cloud cover and temporal and spatial resolution continue to be the main limiting factors in an otherwise highly effective method of collecting oceanic information. Other observing systems, some relatively new, are augmenting the data provided by buoys and satellites: gliders, drifters, CODARS (active remote sensors used to measure currents), over-water stationary platforms such as navigational aids and oil rigs for deploying a myriad of in-situ sensors, and t in-situ sensors that are fit on various vessels such a tankers, cruise ships, tug boats, and ferries. The stakeholders for physical measurements within the littoral zone are numerous and include recreation (tourist industry, fishing, sailing, surfing, etc.), commercial fishing, maritime transit, port security, national defense, energy demands, terrestrial transportation (coastal rain/snow line, fog, etc.), emergency management (hurricane evacuations, etc.), and oil spill tracking. Future aviation requirements for mesoscale observations will be dictated primarily by the Next Generation Air Transportation System (NGATS). NGATS responds to an expected doubling or even tripling in air passenger and freight traffic by 2025 along with a proliferation of light jets. Planning is coordinated by the Joint Planning and Development Office (JPDO), with representatives from the Departments of Transportation, Defense, Home- land Security, and Commerce, the FAA, NASA, and the White House Office of Science and Technology Policy. A wide range of aviation experts from the private sector advise the JPDO. A satellite-based technology that broadcasts aircraft identification, posi- tion, and speed with once-per-second updates is the backbone of NGATS. Through mutual sharing of flight information among controllers, pilots, and aircraft navigation systems, flight routing will be transformed from the âhigh- ways in the skyâ paradigm of today to more direct and efficient routing. It is too early to say in detail what new requirements for weather obser- vations will be, consistent with greater efficiency and improved safety of flight operations, but huge potential exists for smaller commercial carriers and general aviation to supply in-situ observations. Thousands of general aviation aircraft are in the air most of the time, and they generally fly lower than passenger airlines, often in or not far above the boundary layer, where observations are most sorely needed. Most new automobiles come off the assembly line with temperature sensors and an interior readout. In partnership with automobile manufac- turers, the Federal Highway Administration is conducting a Vehicle Infra-
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 75 structure Integration (VII; Pisano, 2007) to investigate how these millions of temperature measurements might be collected and shared more widely. A crude measure of rain rate is also possible through monitoring windshield wiper speed. Methods for communicating this information from individual vehicles to a processing center are being studied. Additional development of nanosensor technologies should realize âmeasurements on a chip,â which would replace the 20th-century sensor paradigm. Recommendation: The Department of Transportation should assess and eventually facilitate the deployment of high-density observations through the Vehicle Infrastructure Integration initiative. Similar con- cepts should be considered for general aviation and marine transporta- tion vehicles. WATER RESOURCES Importance to the National Economy Monitoring water availability and movement in the broadly considered environment (i.e., the atmosphere, land surface and subsurface, and coastal waters) is of utmost importance. Domestic, municipal, industrial, agricul- tural, and recreational activities all require access to water of adequate quantity and quality. Yet water availability is not evenly distributed over the country, nor is it always available when needed over periods ranging from years to days and often even hours. This variability results from the intricate interplay of many natural processes and human activities. It is manifested by the common observation that we often have too much water or not enough. Everyone is aware of the multi-year drought in the Southeast and the continuing battle among Western states over water rights. The main stem floods along the Missouri and Mississippi Rivers and their tributaries in the summer of 1993 caused $21 billion in damage, and the catastrophic flooding of New Orleans from Hurricane Katrina in 2005 was the worst natural disaster in U.S. history with losses of $125 billion.16 The distribution of water resources across the country is a combination of nature-controlled supply and human-controlled storage and consump- tion. On the supply side we have precipitation in the form of rainfall and snowfall ranging from as little as 200 mm in large parts of the western United States to over 1500 mm in Florida and the coast of the Gulf of M Â exico and the Northwest. A portion of the fallen water finds its way to short-term storage in rivers and lakes and long-term storage through 16â NationalClimate Data Center, NOAA, Billion Dollar Weather Disasters, NOAA, http:// www.ncdc.noaa.gov/oa/reports/billionz.html#chron. Figures not adjusted for inflation.
76 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP recharge of the groundwater. The time scale of the short-term storage ranges from hours to weeks in rivers and months to seasons in lakes. The long-term storage is replenished at very slow rates but results in residence time on the order of years. On the consumption side, the distribution of the population density, industrial and agricultural activities, and the tradeoffs between the needs for flood control, energy production, and recreation con- trol water availability or shortage. While certain activities (e.g., municipal, industrial) result in little water loss, others, such as agriculture, require large quantities with significant losses to the atmosphere. The âbig pictureâ of water quality is even more complicated. Indus- trial and municipal activities result in water pollution, and the need for water treatment. This treatment is never complete, and natural processes are counted on to assist in the treatment. The plethora of chemicals used in industrial processes prevents comprehensive and complete addressing of their environmental impact. As a result, surface and ground waters contain heavy metals, toxins, pharmaceuticals, and deadly bacteria. As water is a major transport agent, the effects extend thousands of miles in spatial scales and persist in the environment for many years if not biodegradable. Rainfall and agricultural practices result in soil erosion, and the displaced particles carry with them both fertilizers and pollutants. Over time these travel to streams and rivers and affect environments thousands of kilometers away. A prime example here is the problem of hypoxia in the Gulf of Mexico, which traced back to nutrients used in the Midwest for crop production. This brief overview of national water resources should be sufficient to illustrate the extremely complicated nature of the problem. The processes of water supply, storage, and consumption span a tremendous range of scales both in time (from seconds to decades), and in space from (sub-Âmillimeters to thousands of kilometers). The data and other information about these processes are scattered across many organizations and are difficult to access in a comprehensive fashion despite efforts such as the National Integrated Drought Information System (Western Governorsâ Association, 2004). Sig- nificant gaps exist in our knowledge about the functioning of the natural water systems. Current Assets and Operational Requirements for Mesoscale Observations Addressing the problems of âtoo much water or not enoughâ requires careful monitoring, skillful prediction, and rational control. Federal respon- sibilities are organized along those lines with some degree of overlap. For example, the United States Geological Survey and the Bureau of Reclama- tion monitor surface and groundwater status in terms of quantity and q Â uality using information from some 1.5 million sites, EPA enforces compli- ance with environmental standards and regulations, and NOAA focuses on
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 77 the coastal waters and the atmosphere. The National Weather Service has the mandate to routinely forecast stream flow at some 20,000 points across the country. Toward this end, it has established the HydroÂmeteorological Automated Data System (HADS)17 to collect raw hydrological and meteo- rological data from sites operated by a variety of agencies, using the Data Collection Platforms aboard GOES satellites. The U.S. Army Corps of Engi- neers develops, monitors, and operates engineering structures such as reser- voirs, and dams and locks on major rivers. In many regions of the country these responsibilities are shared with state and other local agencies. For example, Floridaâs water resources are managed by four water management districts that are responsible for providing water for municipal and rural consumption, agricultural use, and ensuring protection of life and property. The Tennessee Valley Authority operates numerous water storage reservoirs for water supply, flood control, and electric energy production in the South- east. Comprehensive discussion of all the federal, state, and local agencies and their activities related to the nationâs water resources is prohibitively complex and beyond the scope of this report. These complexities are also emphasized by an American Meteorological Society policy statement on water resources (AMS, 2008). Since there is no single agency responsible for management of water resources, and there is no national water policy (Galloway, 2006), our discussion will focus on the major mechanism of observational capabilities that we consider critical for addressing multiple national needs. Serving multiple national needs requires decision-making regarding water apportioning and restricting. These decisions often address the con- flicting objectives of different users and are made using incomplete informa- tion regarding the current and future state of water resources of interest. To support this decision-making, responsible parties use predictive models that interpolate and extrapolate the available data into the variables of inter- est that are often not observed directly. Examples of such models include rainfall-runoff transformations, flash-flood forecasting, flood routing along main rivers, groundwater recharge and flow, land-atmosphere interaction with estimates of evapotranspiration, sediment transport and sediment yield, snowmelt, and water storage, just to name a few. These models are highly uncertain because they describe complicated nonlinear processes that are difficult to observe and that are the result of multiscale interactions of other processes. The predictive skill of these models varies, but uncertainty is an inherent part of any of them. This uncertainty, which is hard to quantify, can be attributed to (1) the lack of complete understanding of the processes involved, (2) suboptimal parameters of the mathematical representations that constitute the models, (3) errors 17See â http://www.nws.noaa.gov/oh/hads/
78 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP in the initial conditions, and (4) errors in the main input (e.g., rainfall in the flash-flood forecasting models). Much of the above uncertainty can be ascribed to the limitations of our observing systems, both for opera- tions and for research, that is, for learning about the processes of interest. These observing systems provide the empirical information that is used to express formally our understanding of the natural processes, calibrate (i.e., adjust the parameters of) our models, and provide the initial condition and the driving inputs. Therefore, the uncertainty due to the limited scope (spatial and temporal sampling resolution and accuracy) of our observ- ing systems propagates all the way to decision-making on the use of our national water resources. For example, Welles et al. (2007) report a lack of significant progress in the skill of stream-flow forecasting models over the past 20 years. Improving the forecast quality by replacing the currently used models with a new-generation of spatially distributed representation of hydrologic processes requires adequate observational input. Studies of the âforecast worthâ in the context of reservoir operation clearly show significant economic benefits if reservoir inflows are known more accurately (e.g., Georgakakos et al., 2000). The inflows taken in combination with the current storage determine water availability. This, combined with predictions of water demand, or the demand for energy that can be produced by releasing water through a turbine system, and subject to environmental constraints (e.g., to satisfy the minimum required discharge to sustain ecology downstream), results in a decision on how to operate the reservoir. Needs for the Future The question arises, âWhat hydrologic model requirements are needed to realize improved prediction relevant to the problem we are discussing?â The answer is not straightforward, and it depends on the spatial and tem- poral scales involved. Consider first a large river. To make a prediction of the discharge at an arbitrary point downstream, we need to know the discharge upstream and an estimate of the inflow into the main channel between the two points. For this we need channel routing models based on the principles of fluid flow in an open channel. The hydraulic characteristics such as slope, width, bottom and bank roughness, and water height deter- mine the answer. When the river basin is large enough, a convective storm, even one with high rainfall intensity, hardly matters, because what happens at the point of interest downstream is mainly affected by the water flow already in the channel. At the opposite end of the spectrum is flash flooding in a small basin. Here, what happens in the channel is largely irrelevant for the forecasting of discharge at the basin outlet, because it will change quickly (within 10-30 minutes, depending on the location and basin size) if
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 79 enough rainfall occurs. The amount of rainfall and the physical-topographic characteristics of the basin matter most. Among those characteristics it is the level of water storage in the upper zone of the soil that determines the partitioning of rainfall into runoff. This storage can be estimated if mea- surements of the soil-moisture profile are known. Soil moisture plays a major role in several hydrologic processes that affect water resources at many spatial and temporal scales. It controls parti- tioning of rainfall water into surface runoff and the infiltrated water. Surface runoff constitutes the fast-response component by a basin, with water flow- ing through the channel network to the basin outlet. The infiltrated water is either consumed by plants or percolates to deeper storage, recharging groundwater aquifers. Soil moisture also controls the partitioning of energy incident on the land surface. Water availability for consumption by plants leads to evapotranspiration, a major component of the surface energy bud- get. Prolonged water deficit in the root zone affects the life cycle of plants and eventually leads to changes in the surface albedo. Water transported to the atmosphere by evapotranspiration affects thermodynamic processes and, under the right circumstances, precipitates, usually at locations far removed from its origin. Through these processes, moisture in the top layers of soil acts on shorter time scales, to influence day-to-day weather, whereas the amount of soil moisture at deeper levels impacts slower processes at regional scales and acts as a source for water that deep-rooting plants bring to the atmosphere during extended periods without precipitation. Clearly, knowledge of actual soil moisture from a network of stations can help forecast stream flow, evapotranspiration, groundwater discharge, and precipitation. But measurements of the soil-moisture profile some 2 m deep are needed. Moisture in the near-surface layer controls the infiltration capacity and changes rather quickly. The lower layer includes most of the soil and provides moisture for certain class of plants (e.g., grasses). Water is transported between these two layers by gravity, root suction, and capillary suction. The water content in that layer fluctuates more slowly than in the top layer. A still deeper layer extends beneath the soil and provides water for larger plants (e.g., trees). It fluctuates slowly, and its depletion is a sign of a major drought. Spatial variability of soil moisture is high and not very well understood. It is controlled by the variability of rainfall, elevation, slope exposure, land use, land cover, and the hydraulic characteristics of the soil. All these characteristics vary, the last one perhaps the most significantly, because it depends on the pore size distribution and the structure and composition of the soil particles. In the absence of a comprehensive national network of soil moisture observations, our understanding of this variable is based on experimental in-situ data (Illston et al., 2008), focused remote sensing campaigns, and modeling studies.
80 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP Currently available remote sensing technologies cannot provide moisture observations for the entire soil column. The signal measured by Âradiometers deployed on aircraft or spacecraft originates from roughly the top 5 cm of the soil and is often obstructed by the water content in and on the plants. The spatial resolution of microwave observations of soil moisture is a func- tion of the frequency, antenna size, and the antenna range. While aircraft- mounted radiometers can provide data with the resolution of about 1 km or better, national coverage requires satellite-based sensors. This translates into resolution on the order of 5 km (Entekhabi et al., 2004). Methods of in-situ measurement of soil moisture take advantage of various physical phenomena (Raats, 2001). Perhaps the most practical method is Time Domain Reflectometry, in which the propagation velocity of an electromagnetic pulse, which depends on the water content, is mea- sured. While these probes require careful calibration, they are inexpensive, safe, and easy to install. Any soil-moisture measurement network should also include soil-temperature sensors. These easy to make measurements would help predict surface runoff when rain falls on frozen soil, helping to mitigate effects of frequent spring flooding in parts of the country. Recommendation: A national, real-time network of soil moisture and soil temperature observations should be deployed nationwide at approximately 3000 sites. This number corresponds to a characteristic spacing of approximately 50 km for a network that is spatially distributed across the continental United States. Although this spacing is insufficient to capture the full spectrum of short-term spatial variability of surface soil wetness, it is small enough to represent seasonal variations and regional gradients, thereby supporting numerous important applications such as land data assimilation systems in support of numerical weather prediction, water resources management, flood control and forecasting, and forestry, rangeland, cropland, and ecosystems management. This characteristic spacing would also provide data at a resolu- tion that complements historical and relevant datasets. Site selection should be biased toward existing networks, provided that the instrument exposure is acceptable and real-time communication is possible. Although we argue for the deployment of a national network of soil moisture measurements to improve the prediction of water movement on the surface and below, precipitation remains the most significant variable that determines runoff. Currently two major sensors are used to monitor precipitation: rain gauge networks and weather radars. In principle, the combined use of these two systems should provide detailed and accurate depiction of rainfall across the country. Unfortunately, this is not the case, especially at the short time scale relevant to flash-flood prediction. Partly
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 81 due to very high spatial and temporal variability of precipitation, and rain- fall in particular, the accuracy of rainfall maps is not very high. Ciach et al. (2007) report random errors approaching 50 percent for hourly rainfall maps produced by the national network of WSR-88D weather radars, also known as NEXRAD. As the temporal scale of rainfall accumulation increases, the random errors decrease, and, as a result, seasonal maps of precipitation depict correct pictures of the process. The major problem is sampling. Rain gauges are distributed too sparsely to capture the variability of rainfall patterns, in particular those of convec- tive origin. Radar beams âlookâ slightly upwards and tend to overshoot clouds at a certain distance. Radars located on mountaintops in the West consistently miss precipitation originating in clouds at lower elevations. A solution is to place small, inexpensive radars that survey relatively small domains (~1000 km2), such as urban areas or sections of mountainous t Â errain. We discuss such systems further in Chapter 4. Another variable that is not observed as densely as it should be is the stream flow. The USGS monitors the nationâs rivers in real time at some 1700 sites. Other agencies complement this at the sites they operate. This is not sufficient coverage, considering the complexity of water movement though the landscape and the primary role that water transport plays in other biogeochemical processes. Continuous observations of stream and river discharge provide a dual benefit for the general problem of forecasting and control of water resources. On the one hand they are directly relevant to flood forecasting and reservoir inflow prediction, and on the other hand they provide a constraint on the models used to forecast other elements of the water cycle that are critical for numerous applications. These include groundwater discharge, pollution transport in surface and ground water, and evapotranspiration. Accurate monitoring of the major fluxes and storages of the water cycle is a prerequisite to improved prediction of many environmental problems affecting the nation. Transport of sediment originating in soil erosion is a result of agricultural practices and vegetation, erosive power of rain- drops and wind, concentrated surface runoff, and transport along the river channel network. Sediment carries both nutrients and pollutants that are attached through cohesion and undergoes transformations while traveling. It affects many other quality aspects of the surface waters and their biologi- cal environment by changing the turbidity and acidity. Current techniques for stream-flow estimation are expensive and labor intensive. Building the structure that houses the sensor that measures stage (depth) is the major expense. The relationship between stage and discharge is developed empirically by periodic and more direct measuring of the discharge, as a product of water velocity and channel cross-section. The empirical data collection has to be repeated over time so that a full range
82 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP of variability is represented. For high flows this presents practical difficulties and risk to the crew. Recent developments include advanced contactless technologies, and several are being tested and researched. The techniques range from optical sensors to active remote sensing using low-power radars. Other approaches involve computational fluid mechanics models to develop the rating curve and an inexpensive stage sensor for converting to discharge. Some of these techniques are inexpensive and could complement the core networks oper- ated by the USGS and other agencies. The observational limits of various aspects of our nationâs water resources have been recognized by the research community. Hydrologists and environ- mental engineers argue for the development of a network of well-instrumented natural observatories to further our understanding of water movement in the environment. Comprehensive observations of water quantity and quality are required to improve our predictive capabilities to benefit society. Details of the arguments are provided in CUAHSI (2007) and WATERS (2008). FOOD PRODUCTION Importance to the National Economy Food is grown in all regions of the United States, with each region tak- ing advantage of local climate and soils to exploit its competitive advantage for specific food-related products. The relatively inexpensive transporta- tion of the 20th century has reduced the incentive to raise a wide range of food crops, including some that are only marginally adapted to local soils and climate, in every region. With inevitable rises in transportation costs and increased interest in locally grown food, future weather and climate information needs for food production may be more extensive than in the past. Fruits and vegetables grown at the margins of their optimal ranges are more vulnerable to influences of drought, flood, water-logged soils, heat stress, cold stress, cloudiness, too high or too low humidity, diseases, insects, herbivores, growing season length, or other factors relating directly or indirectly to climate. The commodity crops of corn, soybean, wheat, oats, barley, rye, etc. are grown on vast areas as monocultures. Food consumed by humans in the categories of fresh fruits, nuts, and vegetables, by contrast, are con- sidered relatively high-value crops and are grown in smaller plots with higher income per unit area, more intense use of labor, more frequent use of irrigation, and higher costs of production per unit area. For various rea- sons, monitoring meteorological conditions on smaller spatial and temporal scales may be more important in regions growing specialty crops than those growing commodity crops. This will become increasingly so as specialty
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 83 crops are raised more widely in climatically marginal regions or regions commonly devoted to commodity crops. Animals are raised in every region of the United States for meat, milk, and egg production. But like commodity grains, commodity meat produc- tion (beef, pork, poultry, fish) tends to concentrate in certain areas where there is access to feed grains, abundant water, optimal temperature or pre- cipitation regimes, and access to transportation or markets. Animals used for meat, milk, and egg production may be raised in confined spaces (either indoor or outdoor) or in âfree-rangeâ environments. Confinement operations present additional environmental issues, such as high volumes of odor dust and waste, that call for additional environÂ mental monitoring. Free-range (i.e., grazing) operations typically cover large areas where growth and productivity of grazing materials are factors to be monitored. Extreme events such as heat waves, freezing rain, extreme cold, severe storms, excessive rain or snow, or high humidity can have serious impacts on animal productivity or even mortality. Weight gain in meat animals, egg production, milk production, and the success of animal breeding are all negatively impacted by extreme high temperatures. Cold rain followed by sub-freezing temperatures leads to sickness in beef animals raised with- out shelter. The monitoring of current conditions and access to reliable short-term forecasts would allow pre-emptive actions to minimize adverse weather effects on animals raised under confined conditions. U.S. food production feeds a population of over 300 million people. In 2007, the United States exported about $82 billion in commodity crops, livestock, and horticultural products. In 2008, the total is expected to be $114 billion.18 Current Assets and Operational Requirements for Mesoscale Observations Environmental conditions monitored for agricultural crops usually include standard surface meteorological variables but also include photoÂ synthetically active radiation (PAR), evapotranspiration, soil temperature, and soil moisture. For some crops, leaf wetness (as a measured variable) is a critical factor for management decisions relating to pests and pathogens. Of these variables, the one least likely to be observed, and yet of critical impor- tance for many regions, is soil moisture. The heterogeneity of soils and land- scapes make representative observations of soil moisture a major challenge. The increased education and sophistication of agricultural producers, coupled with the increased availability of weather and climate information 18â U.S.Department of Agriculture, available at http://www.fas.usda.gov/cmp/outlook/2008/ Aug-08/AES-08-28-2008.pdf.
84 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP over the Internet, has intensified use of such information by producers and by agribusiness service providers for near-term management decisions, long- term plans for marketing, investments in conservation practices, and water management (irrigation, tile drainage, grass waterways). Modern farm machinery comes equipped with devices for measuring and recording plant- ing rates, chemical application, and grain harvest yield, all as a function of the (high-resolution) position in the field. This high spatial detail, along with the high spatial detail of weather and soil conditions begins to reveal previously unavailable opportunities for maximizing yield and reducing adverse environmental impacts. Agribusiness service providers also must be knowledgeable of current and future weather conditions for maintaining material inventories, managing storage facilities, and generally anticipat- ing weather-driven demands by producers for their goods and services. The crop insurance industry has a major interest in reliable and accurate weather and climate information, especially under potentially changing climate, and in extreme events such as high wind, tornadoes, drought, hail, and freeze occurrences. Needs for the Future Weather Data for Driving Decision-Support Tools The increased use of decision-support tools in agriculture based on current or projected future conditions calls for a wider range of measure- ments, higher density of sensors, and higher frequency of observations. High-density surface wind observations go into the formula for estimating evapotranspiration and determine when conditions are favorable for apply- ing pesticides or starting controlled burns in the fields. Models of growth for commodity crops use past, current, and future predicted weather and allow producers to plan management and marketing activities. Decision- support tools can be designed to alert producers of impending disease or insect outbreaks when future conditions favor such events. Examples of methods used to increase profitability or environmentally sustainable agri- culture include decision-support tools and models for predicting soil ero- sion, nitrate leaching, soil moisture, soil temperature, irrigation scheduling, forage quality, sub-surface drainage tile flow, stream-flow, water quality, insect migration or infestation, fungal growth, milk production, and weight gain in meat animals. The storage of grain and transport of both grain and animals to market are vulnerable to weather-induced hazards or reduction in product quality.
NATIONAL NEEDS FOR MESOSCALE OBSERVATIONS 85 Bio-Economy and Increased Needs for Weather Information National mandates for the increased use of biomaterials to replace f Â ossil fuels for mobile transportation have intensified the need for enhanced biomass production from agricultural lands. Future needs to raise increased amounts of both food crops and fuel crops from the same land area will heighten the role of weather and weather forecastingâespecially seasonal forecastingâin decision making in the bio-economy. A wider variety of crops in regions now commonly dominated by monocultures of commod- ity crops will experience changed surface-atmosphere interactions, such as changed evapotranspiration, which in turn could alter the precipitation recycling ratio. Interannual variability in cropping choices therefore could contribute an anthropogenic component to the interannual variability in regional climate. Bringing marginal land into production because of the profit incentive of higher commodity prices for feed grains and biofuels may require special monitoring; such lands are marginal because they are highly erosive or are located at the margins of cropping regions due to their soil or climate conditions. Soil storage of carbon is emerging as a method of sequestering carbon from the atmosphere. Microbial processes in soil that regulate the conversion of labile carbon to carbon dioxide are highly temperature and moisture dependent, suggesting a need to monitor these conditions as a means of monitoring carbon storage. All these factors raise the urgency for higher density meteorological and soil measurements for the bio-economy. Water Quality Observations Related to Food Production Emerging issues of surface water quality (with negative contributions by chemical-laden runoff from agricultural lands), long-term Âsustainability of agricultural practices, and soil sequestration of carbon to meet the goals of reducing concentrations of atmospheric carbon dioxide likely will increase the demand for additional environmental measurements. Surface- water-based measurements of temperature, stream flow, dissolved oxygen, particulate loading, nitrate and phosphate concentrations, and pesticide concentrations are of most interest. By following the analysis provided by Schlatter et al. (2005), we can estimate the spatial and temporal scales of influences of weather on food production (Table 3.3). We can also estimate the measurement resolution (instrument accuracy, spatial resolution, and temporal resolution) needed to meet the needs of the various food production areas (some are speculative and require validation).
86 OBSERVING WEATHER AND CLIMATE FROM THE GROUND UP TABLE 3.3â Spatial and temporal scales of several meteorological phenomena of consequence for agricultural industries, and the measurement resolution (instrument accuracy, spatial resolution, and temporal resolution) required to adequately observe those phenomena Measurement Event/variable Space Time Resolution Heat wave 500-1500 km 2 days-1 week 1Â°C , 10 km, 1 h (temperature) Drought (soil 500-1500 km 2 weeks to 2 mm moisture) interannual Wind 1 km-2000 km 1 min-4 days 1 m sâ1, 1 km, 1 min Precipitation 10 km-regional hours to days 1 mm, 1 km, 1 h seasonal to interannual Cloudiness local to regional daytime hrly to 1.1 sky, 10 km, 20 min clim Temperature 500-1500 km seasonal 1Â°F, 10 km, 1 h Flood 0.1 km-100 km 2 days-2 weeks sub-basin Hail 0.1 km-20 km 5 min-5 h 100 m Source: Derived from an analysis provided by Schlatter et al. (2005).