The Atmospheric Sciences: Entering the Twenty-First Century (1998)

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Contributions of the Atmospheric Sciences to the National Well-Being

The responsibilities of the atmospheric sciences include the advance of fundamental understanding, the prediction of weather and climate change, and the identification of environmental threats. This section examines four ways in which the atmospheric sciences contribute to national well-being and the achievement of national goals through protection of life and property, maintaining environmental quality, enhancing economic vitality, and strengthening fundamental understanding. Today, they contribute to a broad range of decisions concerning individual actions, business and economic strategies, and public policy.

Atmospheric information is valuable when it helps to clarify the advantages and risks of alternative courses of action for private and public decision makers, but assessing the influence of atmospheric information on public safety and economic activities is not straightforward. Atmospheric information is usually only one of many factors that influence a decision, and the value of a forecast often depends on such factors as lead time, forecast resolution, and expected accuracy and on user constraints such as the ability to respond or to assess realistically the costs versus benefits of various courses of action.

Protection of Life and Property

The United States experiences a great diversity of weather, some of it the most severe in the world. As a consequence, this nation has been a leader in developing the understanding and technological capability to provide forecasts of the continually changing weather and warnings of severe weather events such as floods, tornadoes, and hurricanes. Atmospheric information and forecasts are provided in the United States through a four-way partnership:

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1. The government acquires and analyzes observations and issues forecasts and warnings.

2. The government, newspapers, radio, and television all participate in dissemination of weather forecasts and severe weather warnings.

3. Private-sector meteorological firms use government data and products to provide weather information for the media and special weather services for a variety of industries and activities.

4. Government, university, and private-sector scientists develop improved understanding of atmospheric behavior and help to turn this advancing understanding into new capabilities and technology for observing and predicting atmospheric events. This four-way partnership has served the nation well; it could be nurtured to generate even greater benefit.

Although we can do little to change the atmosphere or the weather, we can do much to anticipate atmospheric events such as severe weather and thus provide opportunities for protecting lives and property. These capabilities are expanding rapidly, for both traditional weather impacts and new ones, including applications to environmental quality, to solar events that affect satellites in Earth orbit, communications, to power transmission and changes in weather patterns associated with El Niño events. Today, the nation is reaping significant benefits from its investments in atmospheric observations and prediction capabilities.

Need for Forecasts and Warnings

The benefits of weather forecasts and warnings as measured by lives saved, injuries avoided, or property that has not been damaged cannot be estimated easily. Determining the economic benefits of long-term forecasts, such as those associated with El Niño, is even more difficult. Nevertheless, casualties produced by unusual weather events are substantial, both in an absolute sense and relative to other natural disasters.

Long-term fatality statistics for tornadoes and hurricanes are shown in Tables I.2.1 and I.2.2, using data that go back to the 1930s and 1900s. The data show remarkable progress. More detailed information on weather-related fatalities and damage in the United States for 1991-1995 is given in Table I.2.3. The number of fatalities attributable to weather is typically 300-400 per year. However, one large event, such as the extreme temperatures of 1995, can add as many as 1,000 fatalities to that total. Similarly, Hurricane Andrew (1992) and the floods in 1993 each caused more damage than is attributable to all weather events in some other years. Changnon et al. (1997) present an analysis of the effects of recent weather events on the U.S. insurance industry.

Table I.2.4 provides worldwide statistics on deaths owing to civil strife, natural disasters, and other environmental causes. It shows that more than 25 percent of deaths are due to drought, famine, and severe weather and that these

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events account for more than 92 percent of all people affected by all the disasters combined.

Weather fatalities and damage could be mitigated by improved design and construction standards for buildings and critical systems; relocation of residents from hazard prone locations; and earlier, more accurate, and more focused warnings of severe weather. Although it is difficult to estimate accurately the relative effectiveness of implementing these three strategies, it seems that improving severe weather warnings, despite requiring investments in observational technology and forecast capabilities, might be the least expensive and most feasible of

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the three options and might generate the increased public confidence that would lead to even greater response to warnings. It is noteworthy that early warnings appear to have been effective in limiting to 23 the number of deaths attributed to Hurricane Andrew in 1992, even though the direct damage reached a record total of more than $25 billion (Hebert et al., 1996).

Progress in Weather Services

In the United States, daily weather maps and forecasts were first provided by the Army Signal Corps, starting in the 1870s. Radiosonde networks established over much of the world in the late 1940s and 1950s, practical numerical weather prediction initiated in the late 1950s, radar data networks also established in the 1950s, and weather satellites deployed in the 1960s all led to measurable improvements in forecasts.

The National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service (NWS) are now completing a historically unique technological development cycle. New facilities include a national Doppler weather radar network, major weather satellite improvements, the enhanced Automated Surface Observation System (ASOS) surface network, and a computerized network of weather display and prediction systems (Automated Weather Interactive Processing System—AWIPS) to be distributed at forecast centers around the country. In addition to improving weather forecasts, these new capabilities will be used for the study of climate and of atmospheric chemistry and physics, and for a variety of applications and special purposes. However, the full benefits of these new technological systems will be realized only if there is a sustained and substantial commitment by the government to support research efforts such as the U.S. Global Change Research Program (USGCRP) and the U.S. Weather Research Program.

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Maintaining Environmental Quality

The human habitability of the Earth depends on certain basic prerequisites, including the availability of clean air and water, food, shelter, and security from natural hazards. Natural processes sometimes create adverse environments, and local anthropogenic activities sometimes create life-threatening conditions. Examples include the lethal episodes of smog in London and in Pennsylvania valleys apparently caused by coal burning during the nineteenth and early twentieth centuries. Local anthropogenic influences on air quality and other aspects of the environment continue to be major problems for individual cities, states, and countries. When the pollution caused by one jurisdiction interferes with the economic interests of another, governments become involved in complex issues.

Chlorofluorocarbons and Ozone

Recent concerns have focused on threats posed by certain trace gases that are long-lived and mix throughout the entire global atmosphere. Important examples are the manufactured chlorofluorocarbon (CFC) gases that were widely used in spray cans and refrigeration systems in the middle to late twentieth century. These gases have lifetimes of years because they have no natural removal mechanisms in the lower atmosphere. CFCs released at the Earth's surface diffuse in a few years to the upper atmosphere where they are exposed to energetic solar radiation. After a series of chemical transformations, CFCs lead to a decrease in the ozone concentration in the stratosphere, which in turn permits an increase in dangerous ultraviolet radiation at the Earth's surface. As described later, scientific research produced an explanation of the processes involved. When the cause-and-effect relationship became known and accepted, the governments of many nations developed and signed agreements (the "Montreal Protocol") to limit products deemed harmful to the ozone layer.

Greenhouse Gases and Global Change

A more complex problem is posed by the increasing concentrations of so-called greenhouse gases, primarily carbon dioxide released by the combustion of coal, natural gas, and petroleum. Some of the carbon dioxide is absorbed in the terrestrial system, but a globally dispersed residual has been accumulating in the atmosphere at a rate of about 0.5 percent per year.

Theory suggests that increasing concentrations of greenhouse gases will result in a warming of the planetary surface and that the direct effects may be amplified by feedback mechanisms, including absorption and re-emission of infrared radiation by atmospheric water vapor, itself a greenhouse gas. The observed concentrations of carbon dioxide (and other greenhouse gases such as methane) have increased since the beginning of the industrial revolution in the

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eighteenth century in parallel with the consumption of fossil fuels. Moreover, there appears to have been an increase in the Earth's surface temperature over the last century. Although all of the complex interactions are not fully understood, there is enough evidence that the climate research community has accelerated efforts to understand the links and interactions among components of the climate system. The federal government has responded to these concerns with the U.S. Global Change Research Program that brings together the efforts of many agencies in a coordinated and comprehensive study (see USGCRP, 1997). Other governments are also concerned and have turned to the international scientific community for advice. In its most recent report, the Intergovernmental Panel on Climate Change (IPCC, 1996) has stated, "The balance of evidence suggests that there is a discernible human influence on global climate."

Understanding and taking action on the effects of greenhouse gases are each challenging because of the difficulty of modeling the entire climate system and the complexity of assessing economic, social, and political implications. Atmospheric scientists will have to collaborate with disciplines that can delineate other dimensions of these issues to develop an understanding that may be useful to governments and society. Moreover, the level of public confidence in climate change predictions will directly influence the urgency with which the nation undertakes measures to mitigate, or adapt to, the predicted change.

Aerosols

Anthropogenic aerosols created by the burning of some fossil fuels are another example of environmental consequences of human activities. These tiny particles can limit visibility, cause lung problems, foul delicate machinery, reduce the intensity of the sunlight reaching the Earth's surface, and contribute to acid rain. Aerosols influence the formation of clouds and hazes. Screening of sunlight and changes in cloud properties have potential climate effects since they could disturb the energy balance of the Earth-atmosphere system. An important question is the extent to which anthropogenically produced aerosols are offsetting, delaying, or altering the nature of global warming attributed to increasing concentrations of greenhouse gases. Years of research will be required in order to develop the quantitative understanding necessary to advise policy makers about the consequences of increasing concentrations of aerosols (see NRC, 1996a).

Role of the Atmospheric Sciences in Environmental Issues

Atmospheric scientists often respond to an emerging environmental problem with dynamical and chemical studies and with analyses of the associated scientific issues. Sometimes such studies reveal that scientific advances are required to explore and then understand the new problem and its relation to atmospheric processes or events.

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Studies focused solely on the scientific aspects of an environmental issue are rarely either sufficient or satisfactory. Environmental issues and their potential consequences must be addressed in the context of their human implications, including economic, social, and political aspects. Thus, the atmospheric sciences become most effective as partners in interdisciplinary collaborations aimed at resolving the intertwined scientific and human aspects of an environmental issue.

To maintain the confidence of society, atmospheric researchers must maintain high standards of scientific integrity and, in either purely scientific or applied efforts, must concentrate on scientific questions and rigorous analysis of causes and effects. They must remain neutral with respect to the economic and political considerations that swirl around all issues related to maintaining environmental quality. Through this strategy, atmospheric scientists will help clarify for society the consequences of a range of alternative actions and policy options.

Enhancing National Economic Vitality

A wide range of activities that contribute to national economic vitality are sensitive to weather and climate variations. The atmospheric sciences have a long and successful history of assisting these activities in two ways:

1. The public and private weather information sectors provide predictions of weather and its consequences—some focused on specific activities—that allow government and industry to reduce the economic loss and disruption of activities owing to adverse weather or to take advantage of favorable conditions for action.

2. The atmospheric sciences develop and disseminate a wealth of information that contributes to reducing long-term vulnerability or sensitivity to atmospheric conditions and climate variations and, in some cases, specifies envelopes of opportunity for certain activities.

The atmospheric sciences thus contribute to decision making in both public and private domains and help lubricate the national economic engine. A more effective contribution to enhancing national economic vitality will require improved collaboration between providers and users of atmospheric and environmental information to ensure that needs, decision processes, capabilities, and constraints on alternative actions are fully explored.

Benefits of Weather and Climate Information

Contributions to the gross domestic product (GDP) of activities that are weather sensitive to some extent are shown in Table I.2.5. Other specific examples are available, including the estimate in Table I.2.3 that damage by adverse weather averaged $17.7 billion per year in 1991-1995. As another example, the Federal Aviation Administration assesses the economic cost of weather-related

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delays of U.S. airline traffic at $1 billion per year; improved forecasts of winds aloft would lead to substantial savings in airline costs for fuel (see NRC, 1994a). Governments spend considerable sums on removing snow from highways and repairing highway damage from weathering. Agricultural activities are sensitive to weather events and air quality. The benefits of weather information to the construction, retail, or tourism industries are large but would be difficult to specify precisely.

In attempting to estimate the benefits of weather, climate, and air quality information, it is essential to distinguish those effects that can be mitigated with timely, accurate information from those that cannot. Although the accurate warnings of hurricanes can reduce the loss of life, they provide little protection against the destruction of buildings by hurricane winds or tidal surges. Even though forecasts of precipitation rates can assist in managing flood control facilities, the damage from severe and widespread floods is largely independent of forecast accuracy. Agricultural damage from an extended drought may be severe, even though both long-term outlooks and short-term forecasts were accurate. However, forecasts of severe winter storms allow individuals and industries to make

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suitable advance preparations. Accurate measurements and forecasts of air pollution could be used to mitigate pollution through temporary decreases in emission rates. Improved understanding, modeling, and prediction of the interactions between solar phenomena and near-Earth space will help reduce damage to satellites in orbit and perhaps reduce disruptions of communications and electrical power networks.

Although weather and climate forecasts may not provide for mitigation of all harmful effects, the use of climate data and extreme-value statistics, along with impact assessments, design studies, and possibly appropriate codes or standards, can significantly reduce the adverse consequences of severe weather events. Moreover, long-term climate records provide information critical to urban planning, land-use planning, agricultural strategies, and air quality standards. As skill develops in seasonal climate forecasting on a regional scale, both governments and industry can begin to realize further benefits in shaping strategies to expected weather conditions. Forecasts of El Niño are proving useful in agricultural planning in several Latin American countries (NRC, 1996b).

Strengthening Fundamental Understanding

The following examples illustrate how enhanced fundamental understanding of the atmosphere leads to practical benefits and can stimulate progress.

In the 1930s, Professor Carl-Gustav Rossby was trying to understand the large-scale patterns of the middle and upper troposphere being observed from 3 to 10 km above the surface by newly developed balloon-borne instrument packages. He developed a highly simplified version of the equations of atmospheric motion and predicted a periodic wave structure (now known as Rossby waves) that corresponds to some of the observations. A fundamental aspect of large-scale, midlatitude flow was described by just a few symbols. This work fore-shadowed and contributed to more detailed understanding of large-scale atmospheric flow and was also a significant stimulus for the development of numerical weather prediction and thus for the increased success of contemporary weather forecasts and climate models.

Evidence that state-of-the-art numerical models can reproduce complex atmospheric processes was provided by Joseph Klemp and Robert Wilhelmson in the mid-1970s. Their numerical simulation successfully modeled the three-dimensional structure and dynamics of the powerful thunderstorms common to the Great Plains and other U.S. locations. Their work provided a foundation for the present understanding of severe storm dynamics and perhaps for a method of numerically predicting such events in the future.

The discovery in the last decade of the processes by which the release of the manufactured chlorofluorocarbon gases used in spray cans and refrigeration can damage the protective ozone layer of the stratosphere involved laboratory experiments, theoretical process analysis, ground-based and satellite observations, and

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for verification, instrumented aircraft measurements over the South Pole. The success of the endeavor, and its importance to human life and safety, was recognized by award of the 1995 Nobel Prize in Chemistry to Sherwood Rowland, Mario Molina, and Paul Crutzen.

A widely recognized contribution to fundamental understanding by a meteorologist is chaos theory, pioneered by Edward N. Lorenz beginning in the 1960s. Professor Lorenz explored the properties of a simplified system of equations describing convection. He discovered, through numerical experimentation, that the evolving solutions of these equations were aperiodic and ultimately unpredictable, even though they were clearly deterministic in the sense that they were governed by the equations of the system. Such chaotic behavior of nonlinear systems is now known to be common rather than rare, and this discovery has resulted in a new paradigm for phenomena occurring in almost every field of science. It has also resulted in a widely accepted theory of atmospheric predictability and has led to a deeper understanding of the mathematical structure of atmospheric motion and the nature of strategies required to predict the statistics that describe climate. Of even greater significance, perhaps, is the fact that the understanding of chaos and nonlinear dynamics that stemmed from basic research in meteorology has now illuminated phenomena studied in many scientific disciplines.