1

Introduction

Around the world, the growth of cities seems likely to continue for the foreseeable future. It is expected that today’s urban population of 3.2 billion will increase to nearly 5 billion by 2030, resulting in three out of five people living in cities worldwide (UN, 2008). Urbanization of the world population occurred earlier in developed nations such as the United States compared to less developed nations in Asia, Africa, and Central America. (Figure 1.1).

Urban areas are evident along the U.S. East and West coasts, where long, largely urban corridors house tens of millions of people, as well as at major interior cities such as Atlanta; the Texas triangle of San Antonio, Houston, and Dallas-Ft. Worth; Chicago; Phoenix, and Denver (Figure 1.2 and Box 1.1).

The trend toward such urbanization arises naturally from individual and corporate desires to maximize opportunities and improve efficiency by having jobs, education, housing, and transportation in close proximity. Cities are places where commerce, industry, finance, human services, and culture are centralized. Diversity and social mobility are often enhanced in urban settings.

In addition to these benefits, the growth of cities comes with some environmental costs and challenges that affect the functioning of urban infrastructure, the quality of life of the individuals who live in the cities, and the vulnerability of both to disruption. Many of these costs and challenges have a significant meteorological component that arises from the very nature of cities. The infrastructure that is characteristic of urban settings—large areas covered by buildings of a variety of heights; paved streets and parking areas; means to supply electricity, natural gas, water, and raw materials; generation of waste heat and materials; means to remove sewage and waste/storm water—combine in various ways to create a very distinct local weather environment. This environment is characterized by meso- and microscale urban heat island effects, urban flooding, changes in precipitation patterns,



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1 Introduction Around the world, the growth of cities seems likely to continue for the foreseeable future. It is expected that today’s urban population of 3.2 billion will increase to nearly 5 billion by 2030, resulting in three out of five people living in cities worldwide (UN, 2008). Urbanization of the world population occurred earlier in developed nations such as the United States compared to less developed nations in Asia, Africa, and Central America. (Figure 1.1). Urban areas are evident along the U.S. East and West coasts, where long, largely urban corridors house tens of millions of people, as well as at major interior cities such as Atlanta; the Texas triangle of San Antonio, Houston, and Dallas-Ft. Worth; Chicago; Phoenix, and Denver (Figure 1.2 and Box 1.1). The trend toward such urbanization arises naturally from individual and corporate desires to maximize opportunities and improve efficiency by having jobs, education, housing, and transportation in close proximity. Cities are places where commerce, industry, finance, human services, and culture are centralized. Diversity and social mobility are often enhanced in urban settings. In addition to these benefits, the growth of cities comes with some en- vironmental costs and challenges that affect the functioning of urban infra- structure, the quality of life of the individuals who live in the cities, and the vulnerability of both to disruption. Many of these costs and challenges have a significant meteorological component that arises from the very nature of cities. The infrastructure that is characteristic of urban settings—large areas covered by buildings of a variety of heights; paved streets and parking areas; means to supply electricity, natural gas, water, and raw materials; genera- tion of waste heat and materials; means to remove sewage and waste/storm water—combine in various ways to create a very distinct local weather environment. This environment is characterized by meso- and microscale urban heat island effects, urban flooding, changes in precipitation patterns, 15

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16 16 URBAN METEOROLOGY FIGURE 1.1 Change in world urban and rural population from 1950 to 2030 (projected). Inset shows change in world urban and rural population for the United States from 1790 to 1990. SOURCE: Grimm, N. B., S. H. Faeth, N. E. Golubiewski, C. L. Redman, J. Wu, X. Bai, and J. M. Briggs. 2008. Global Change and the Ecology of Cities. Science 319(756):756-760. Reprinted with permission from AAAS. R02149 Urban Meteorology Figure 1-1 elevated concentration levels for gaseous pollutants and aerosols, and street canyon winds. bitmapped raster image In addition, the high density of population results in enhanced vul- nerability to not only traditional hazardous weather phenomena such as severe thunderstorms and blizzards, but also to heat and cold waves, air pollution, and the rapid spread of airborne disease through a concentrated, susceptible population. Indeed, many of the major weather disasters in the last three decades have been in urban settings. Ranging from tornadoes, major ice and snow events, to floods (often triggered by spring melting of winter snow), to land falling hurricanes, to runaway wild fires, these “Billion

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INTRODUCTION 17 FIGURE 1.2 Human-made lights highlight developed or populated areas of Earth. SOURCE: NASA/ oddard G Space Flight Center Scientific Visualization Studio, http://visibleearth.nasa.gov/view_rec.php?id=11795. Dollar” weather events have taken a serious toll on our nation’s economy (NCDC, 2011; Figure 1.3). Responding to these weather needs has led to the development of the field of urban meteorology. For many years, this specialty consisted of simply observing and forecasting the general weather for cities and surrounding metropolitan areas. However, scientific and technological advances of the past 50 years now allow us to predict a wide set of environmental parameters at relatively fine temporal and spatial scales, for times ranging from the next hour to the next several days and for small regions such as street canyons, individual buildings, and small parks. As these capabilities have improved, the uses for urban weather in- formation and its value to decision makers have increased. The challenge

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18 18 URBAN METEOROLOGY BOX 1.1 Definitions of Key Terms Urban area—To define “urban area,” the U.S. federal government has formally defined Metropolitan Statistical Areas (MSAs) which are composed of counties or equivalent. MSAs are delineated on the basis of a central urbanized area, which is a contiguous area of relatively high population density with a population greater than 50,000 (NRC, 2010a) Urban meteorology—The study of the physics, dynamics, and chemistry of the interactions of the Earth’s atmosphere and the urban built environment, and the provision of meteorological services to the populations and institutions of metro- politan areas (NRC 2010a) Urban meteorologist—Denotes a specialist within the broader meteorological community. The urban meteorologist has both the standard background of a me- teorologist, but specialized training in boundary layer and microscale meteorol- ogy, aerodynamics of airflow around structures, air quality, and human health as impacted by the atmosphere. User of urban meteorology information—Individuals or organizations who use information directly in their operational decisions or strategic planning; and orga- nizations or institutions (e.g. media, government entities, and weather services) that act as translators between the raw data (observations and models) and the public (adapted from NRC 2006). to the urban meteorologist has become not only producing high quality meteorological information, but also delivering it to a wide variety of users in formats that foster its use, within time constraints set by users’ decision processes. Given the extent of U.S. urbanization, a stronger leadership role of the United States in understanding and responding to urban meteorology would better serve the needs of its citizens, as well as developing nations that are undergoing rapid urbanization. EXPLORING OPPORTUNITIES TO IMPROVE URBAN WEATHER INFORMATION The growing demand for urban meteorological products and services has spurred a number of studies and reports that identify opportunities to improve those products and services. Three such reports were produced by Prospectus Development Teams of the U.S. Weather Research Program (US- WRP), which convened a few panels of experts to identify critical research needs in different problem areas.

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INTRODUCTION 19 FIGURE 1.3 A synoptic mapping prepared by the National Oceanic and Atmospheric Administration’s National Climatic Data Center (NOAA NCDC) showing weather-caused disasters with at least one billion dollars in losses to property and infrastructure in the last three decades. SOURCE: NOAA, http://www.ncdc. noaa.gov/img/reports/billion/billion2010.pdf. R02149 Urban Meteorology Among the most influential of the USWRP 1-3 Figure reports has been Forecast Issues in the Urban Zone: ReportbitmappedProspectus Development Team of the 10th raster image of the U.S. Weather Research Program (Dabberdt et al., 2000), which identi- fies research needs and opportunities related to the short-term prediction of weather and air quality in urban forecast zones. It points out that weather has significant impacts on the many people who live in major urban areas and argues that urban users have different weather information needs than rural users. Further, it identifies needs for “improved access to real-time weather information, improved tailoring of weather data to the specific needs of individual user groups, and more user-specific forecasts of weather and air quality.”

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20 20 URBAN METEOROLOGY A subsequent 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., 2004) focuses on the identification and delineation of critical meteorological research issues related to the prediction of air quality. The report has a strong emphasis on urban areas and points out that forecasting air quality is quite different from severe weather forecasting. The latter is often focused on prediction of particular precursor conditions, while the former is typically associated with calm weather associated with large scale weather patterns. Meteorological observing systems, which are essential to effective air quality prediction, are designed to support prediction of severe weather on the mesoscale, not the microscale subtleties of adverse air quality such as daily evolution of the surface boundary layer (from inversion to unstable/convective, and then a shift back to inversion) and the photochemistry that modifies emissions to produce dangerous pollutants. A third influential study from the U.S. Weather Research Program has been Multifunctional Mesoscale Observing Networks (Dabberdt et al., 2005) which explores the need for enhanced three-dimensional mesoscale ob- serving networks. These networks are important to advancing numerical and empirical modeling for various mesoscale applications which could be utilized by many users of urban meteorological information. These applica- tions include severe weather warnings and forecasts, hydrology, air-quality forecasting, chemical emergency response, transportation safety, energy management. It is essential that the public, private, and academic sectors actively participate in mesoscale observing networks’ design and implemen- tation. The creation and delivery of products should serve multiple applica- tions to help address end user needs. Motivated in part by Dabberdt et al. (2000), in 2004, the Office of the Federal Coordinator for Meteorological Services and Supporting Research produced a report, Urban Meteorology: Meeting Weather Needs in the Urban Community (OFCM, 2004). This report describes roles to be played by fed- eral government agencies in providing urban meteorological services, while emphasizing the need for partnerships between federal agencies, state and local entities, the academic community, and the residents and businesses of the urban community to provide the full ranges of services that are required. The report goes on to present a discussion framework that outlines the concept of urban meteorology, the principal application areas, and the roles of the principal partners. It notes that urban meteorology is an evolving field and that a broad dialogue among all interested parties should be fostered to share values and objectives, resulting in the recognition of common

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INTRODUCTION 21 problems through which the combined efforts to improve urban meteorol- ogy could be coordinated and made more productive. Partially in response to the above reports, the National Research Coun- cil (NRC) has in recent years produced several reports that emphasize the importance of and the need for more attention to aspects of operational meteorology in general and urban meteorology in particular. Particularly relevant studies include the following: Completing the Forecast: Characterizing and Communicating Uncer- tainty for Better Decisions Using Weather and Climate Forecasts (NRC, 2006). This report concludes that “uncertainty is a fundamental characteristic of weather, seasonal climate, and hydrological prediction, and no forecast is complete without a description of its uncertainty.” Effectively communi- cating uncertainty gives users a better understanding of the likelihood of a particular event which in turn improves their ability to make decisions. Successful incorporation of uncertainty information into predictions can be facilitated through a better understanding of user needs, the creation of relevant and rich informational products, and the utilization of effective communication mechanisms. Observing Weather and Climate from the Ground Up: A Nationwide Network of Networks (NRC, 2008). This report demonstrated that a pleth- demonstrated that a pleth- ora of surface monitoring sites often exist in urban areas, but metadata are typically lacking for these sites, data access is not easily available, and data quality may be questionable. It is important that the suitability of these sites is assessed to provide appropriate urban climate data and metadata is col- lected and documented. When Weather Matters: Science and Service to Meet Critical Societal Needs (NRC, 2010a). This report concludes that the United States is not mitigating weather impacts to the extent possible and it has fallen behind other nations in operational numerical weather prediction. The report identi- fies urban meteorology as one important issue that has not been sufficiently recognized or emphasized in previous studies. From the Ground Up (NRC, 2008) and When Weather Matters (NRC, 2010a) both call for the establishment of testbeds to try out new observ- ing concepts and, in concert with users and stakeholders, develop new meteorological products and services for particular user communities, such as urban dwellers. Canadians have provided an example of such an effort with their Environmental Prediction in Canadian Cities (EPiCC) Network. This has an overall objective of providing “…Canadian urban residents with better weather and air quality forecasts through development of an urban- atmosphere modeling system evaluated for Canadian urban climates. This

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22 22 URBAN METEOROLOGY enhanced forecasting capability will contribute to the safety, health, and well being of Canadians through better understanding of the dispersion of smog and particulate precursors in urban environments, accidental and terrorist releases, heat stress and wind chill, and dispersion of air pollutants in urban environments. The research will also contribute knowledge to the better conservation of urban resources (energy and water utilities) …”1 In the United States, an example of such an emerging urban testbed is to be found in the Dallas-Ft. Worth, Texas area, where a regional govern- ment agency is working with a group of universities to install a high-density network of small radars and other observing systems. This effort is described in Appendix B. Other efforts, such as the modeling and forecasting group at the University of Washington in Seattle, have demonstrated the importance of the testbed concept in reaching out to stakeholders at the earliest stages of designing new, urban-oriented products and services. CHARGE AND APPROACH As evidenced by the above reports and the appearance of the first urban testbeds, the field of urban meteorology has grown considerably in the past few decades, and, as discussed above, a number of publications have helped pinpoint pressing needs for scientific advances. To date, how- ever, most assessments of research and development priorities have come from discussions within the scientific research community. There is a need for more direct interaction with key end user communities, who can help identify their information needs. In the spring of 2011, the NRC’s Board on Atmospheric Sciences and Climate (BASC) worked with its core agency sponsors to design a summer study that would open and facilitate a dialog between the research community and the users of urban meteorology information. The BASC Committee on Urban Meteorology: Scoping the Problem, Defining the Needs was tasked to write a report, based largely on the information provided at a workshop, on urban-level weather forecasting and monitoring capabilities and the informa- tion needs of specific end user communities. The committee was asked to describe current and emerging meteorological forecasting/monitoring that have had and will likely have the most impact on urban areas. They were also tasked to describe the needs for the end user communities that are not being met by current urban-level forecasting/monitoring and any forecasting/ monitoring capabilities that are not being utilized by the relevant end user communities, either due to lack of awareness that such capabilities exist, or 1 ttp://www.epicc.uwo.ca/. h

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INTRODUCTION 23 failure to provide such information in a usable form (see full Statement of Task in Appendix D). The committee was also asked to plan and convene this workshop with the goal of bringing together scientific experts with a wide array of represen- tatives from the end user stakeholder community. The committee developed the workshop agenda and selected and invited participants who contributed presentations and took part in plenary and small group discussions. The workshop not only included a wide spectrum of representation from the meteorology research community, but close to half of the participants repre- sented a range of end user stakeholder groups. Participants from federal and local government, national laboratories, academia, and the private sector brought expertise in areas such as urban vulnerability, transportation, public health, urban planning, emergency management, security, utilities, urban modeling, and observations (Box 1.2). There was also some international participation (see Appendix C for a participant list). BOX 1.2 Perspectives from the End User Stakeholder Community at the Workshop “…when you’re on the operational side and you hear [the terms] urban meteorol- ogy, turbulent intensity, morphology, dispersion, forcing fluxes, anthropogenic, spatial…that is not our language. Our language is about evacuation, survivors, first responders, preparedness, recovery, mitigation.” Sandra Knight, Federal Emergency Management Agency (FEMA) “… if we want a very fine spatial resolution [in a model] to look for variations in temperature, pretty much all we have …is land surface temperature, and that is not the temperature in which people experience. Unless we’re laying on the ground, we’re not experiencing that temperature.” George Luber, Centers for Disease Control (CDC) “Nothing is worse during an event than getting a piece of measurement data that you think is very important, but you don’t understand what instrument it came from, what’s the threshold, what’s the sensitivity, what did it actually measure…? What was actually the quantity that was there, and what QA [quality assessment] was performed on it?” Gayle Sugiyama, National Atmospheric Release Advisory Center (NARAC) “… essentially we are looking for just better, more transparent documentation of those basic products that the Weather Service and others put out.” James Rufo Hill, Seattle Public Utilities

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24 24 URBAN METEOROLOGY The workshop consisted of keynote talks (see Appendix A for speaker abstracts), panel sessions on user needs and emerging technologies in urban meteorology, and working group sessions (see workshop agenda in Appendix C). The Committee charged workshop speakers, panelists, and participants to address questions drawn from the Statement of Task (see Appendix D) in working groups and to summarize their discussions in plenary session at the end of the workshop. What follows in this report draws largely from insights and information from the workshop, in addition to previously published works. This report captures the main points of the presentations and discussions at the work- shop and identifies the specific, in some cases unique, needs of the urban setting for weather support, as well as opportunities for academic research and operational practice to work with users to address those needs. Given the reliance on a workshop for most of its input and relatively short tenure for deliberations and analysis, the report does not make recommendations. It is also not intended to be a definitive study of the research and develop- ment needs for advancing weather monitoring and forecasting in an urban environment. However, the information gathered here is intended to be use- ful to government agencies, the academic research community, and urban governments in planning for weather services in the future and developing new initiatives to provide those services ORGANIZATION OF THE REPORT This report covers two broad areas related to urban meteorology: end user needs and current and emerging technologies. Chapter 2 identifies a range of users of urban meteorology information and their information needs. It goes on to discuss why these needs are not being met by current urban-level forecasting and monitoring capabilities and offers some sugges- tions to better address user needs. Chapter 3 provides a brief review of current urban meteorological knowledge to provide context for issues laid out in the report, examines the current state of urban meteorological monitoring and forecasting, and discusses emerging technologies. Chapter 3 also identifies several key needs, challenges, and opportunities. Finally, Chapter 4 builds on the discussions in Chapters 2 and 3 and suggests possible future directions for the field of urban meteorology. This includes short-term priorities where relatively small investments will be required, as well as future challenges which require significant efforts and investments.