The atmospheric sciences have developed an impressive capability over the past century to help society anticipate atmospheric phenomena and events. Progress continues today as improved observational and remote sensing capabilities provide more accurate resolution of atmospheric processes. In addition, enhanced physical understanding, new modeling strategies, and powerful computers combine to provide improved atmospheric simulations and predictions. This progress leads the Board on Atmospheric Sciences and Climate (BASC) to the following vision for the atmospheric sciences entering the twenty-first century:
Improvements in atmospheric observations, further understanding of atmospheric processes, and advances in technology will continue to enhance the accuracy and resolution of atmospheric analysis and prediction. As a consequence, society will enjoy greater confidence in atmospheric information and forecasts and will be able to act more decisively and effectively.
The Atmospheric Sciences and Other Disciplines
This report, by design, focuses on the atmosphere, but recognizes that the atmosphere interacts intimately with other parts of the Earth and its environment. The fluxes of materials and energy between the atmosphere and the oceans, the Earth's surface, the ecosystems of the planet, and the near-space environment shape the structure and evolution of atmospheric processes and events. The report emphasizes atmospheric research, but it also focuses on the societal impli-
cations of atmospheric science, including the benefits of improved knowledge of atmospheric processes for the health and welfare of the environment and society.
Opportunities and Imperatives for the Atmospheric Sciences
As BASC studied the progress and future of the atmospheric sciences, it became evident that a critical contemporary theme involves the increasing importance of integrated observation systems and new observations of critical variables; thus, these constitute the subject of the Board's two highest-priority recommendations, designated as ''Imperatives.''
Atmospheric Science Imperative
Improve Observation Capabilities
The atmospheric science community and relevant federal agencies should develop a specific plan for optimizing global observations of the atmosphere, oceans, and land. This plan should take into account requirements for monitoring weather, climate, and air quality and for providing the information needed to improve predictive numerical models used for weather, climate, atmospheric chemistry, air quality, and near-Earth space physics activities. The process should involve a continuous interaction between the research and operational communities and should delineate critical scientific and engineering issues. Proposed configurations of the national and international observing systems should be examined with the aid of observing system simulation experiments.
In addition, new opportunities for advances in research and services lead to the second imperative:
Atmospheric Science Imperative
Develop New Observation Capabilities
The federal agencies involved in atmospheric science should commit to a strategy, priorities, and a program for developing new capabilities for observing critical variables, including water in all its phases, wind, aerosols, and chemical constituents and variables related to phenomena in near-Earth space, all on spatial and temporal scales relevant to forecasts and applications. The possibilities for obtaining such observations should be considered in studying the optimum observing systems of Imperative 1.
Contemporary numerical computer models of the atmosphere are sufficiently varied and powerful that they can predict or simulate a range of phenomena such as climate change and air pollution episodes, as well as forecasting the weather. However, observations of critical variables on time and space scales relevant to forecasts are essential to improving such numerical simulations and predictions.
Atmospheic Research Recommendations
Common themes in the five Disciplinary Assessments presented in Part II of this report lead to two quite different sets of recommendations: one concerned directly with atmospheric research and related issues and a second with leadership and management.
Atmospheric Research Recommendation
Resolve Interactions at Atmospheric Boundaries and Among Different
Scales of Flow
The major weather, climate, and global observation programs supported by the federal government and international agencies should put high priority on improved understanding of interactions of the atmosphere with other components of the Earth system and of interactions between atmospheric phenomena of different scales. These programs, including the U.S. Weather Research Program, the U.S. Global Change Research Program, and other mechanisms for supporting atmospheric research, require observational, theoretical, and modeling studies of such interactions.
Atmospheric studies are shaped today by the recognition that contemporary approaches must seek to understand, model, and predict the components of the Earth's environment as coupled systems. Critical scientific questions focus on the exchanges of energy, momentum, and chemical constituents between the troposphere and the surface below, as well as with the layers above.
Atmospheric Research Recommendation
Extend a Disciplined Forecast Process to New Areas
A strategy and implementation plan for initiating experimental forecasts and taking advantage of a disciplined forecasting process should be developed by appropriate agencies and the scientific community for climate variations, key chemical constituents, air quality, and space weather events.
The impact of a disciplined process of forecasting (observe, predict, assess accuracy, improve methods) has intensified with the advent of numerical simulation of atmospheric processes because precise quantitative comparisons between forecasts and actual observations can be made easily and because proposed modifications in computer models can be applied to difficult cases retrospectively. Several of the atmospheric sciences are developing capabilities for making quantitative forecasts and improving capabilities by applying the discipline of forecasting. The opportunities include climate forecasting, atmospheric chemistry, and space weather.
Atmospheric Research Recommendation
Initiate Studies of Emerging Issues
The research community and appropriate federal agencies should institute interdisciplinary studies of emerging issues related to (1) climate, weather, and health; (2) management of water resources in a changing climate; and (3) rapidly increasing emissions to the atmosphere.
The emerging issues identified in the recommendation require the attention of atmospheric scientists in a wide range of disciplines and collaborators concerned with human dimensions.
Recommendations for Leadership and Management in the Atmospheric Sciences
BASC recommends that leadership and management issues related to planning and priorities should be addressed forthrightly by the entire atmospheric science community, including federal agencies, professional societies, and the academic and private sectors.
Leadership and Management
Develop a Strategy for Providing Atmospheric Information
The Federal Coordinator for Meteorological Services and Supporting Research should lead a thorough examination of the issues that arise as the national system for providing atmospheric information becomes more distributed. Key federal organizations, the private sector, academe, and professional organizations should all be represented in such a study and should help develop a strategic plan.
Rapid changes in the national weather information system are occurring because of the following:
1. Quantitative information on global weather and climate data, visualizations, and predictions are readily available on global information networks.
2. Computer-to-computer communication enables weather-dependent enterprises to incorporate atmospheric information more readily in their decision making.
Leadership and Management
Ensure Access to Atmospheric Information
The federal government should move forthrightly and aggressively to protect the advance of atmospheric research and services by maintaining the free and open exchange of atmospheric observations among all countries and by preserving the free and open exchange of data among scientists.
The increasing dependence on distributed capabilities has significant implications for access to atmospheric data and information, especially since some nations and some industries advocate schemes for limiting access to electronic data. Two principles have long governed the traditional U.S. view of international atmospheric data:
1. Data acquired for public purposes with public funds should be publicly available.
2. The free and open exchange of atmospheric observations will enhance atmospheric research, understanding, and services for all nations.
Leadership and Management
Assess Benefits and Costs
The atmospheric science community, through the collaboration of appropriate federal agencies and advisory and professional organizations, should initiate interdisciplinary studies of the benefits and costs of weather, climate, and environmental information services.
Reasons for examining the benefits and costs of maintaining the atmospheric enterprise are to ensure that funds invested in atmospheric research and services are highly leveraged in serving national interests and to help determine which new directions in atmospheric research and services will provide the most benefit to the public and private sectors.
Leadership and Management Planning
BASC believes that a national research environment requires a strong disciplinary planning mechanism. This view is reinforced by an obvious contemporary reality: opportunities for progress and service in the atmospheric sciences are far more plentiful than resources. Thus, the efforts of the discipline must be guided by an overall vision and by reasoned priorities. All partners in the atmospheric science enterprisethose in government, universities, and a wide range of private endeavorsmust join together as an effective team focused on the future. For this to come to pass. there must be clear responsibilities for priorities and progress, for resources and results.
To assess the state of the science and look to the future, BASC asked three of its continuing committees and two ad hoc groups of experts to prepare separate assessments that analyze critical scientific issues. identify major opportunities and initiatives for each discipline, and recommend a scientific and programmatic agenda for the decade or two ahead.
These assessments focus both on improvements in fundamental science and on service to society. For the near future, they emphasize forecasts of atmospheric phenomena with significant societal impacts and propose efforts to predict important aspects of seasonal climate variability, chemical processes, and space weather phenomena. For the longer term, they emphasize the resolution of climate variability on the scale of decades to centuries and the possibilities of projecting climate variations.
Atmospheric Physics Research
Atmospheric physics seeks to understand physical processes in the atmosphere, including atmospheric radiation, the physics of clouds, atmospheric electricity, boundary layer processes, and small-scale atmospheric dynamics. The complexity and interactive nature of the physical processes in the atmosphere will usually defy prediction unless supplementary and organizing principles can be found.
Three scientific strategies are recommended:
1. Develop and verify a capability to predict the influence of small-scale atmospheric physical processes on large-scale atmospheric phenomena.
2. Develop a quantitative description of the processes and interactions that determine the observed distribution of water substance in the atmosphere.
3. Improve capabilities for making critical measurements in support of studies of atmospheric physics.
Pursuing these strategies requires specific research efforts related to the interactions among a variety of processes, including those of atmospheric radiation, clouds and other components of the hydrological cycle, aerosols, atmospheric electricity, boundary layer meteorology, and small-scale dynamics. Such studies will require new measurement and analysis techniques based on contemporary concepts and technology.
Atmospheric Chemistry Research
The "Environmentally Important Atmospheric (chemical) Species," by virtue of their radiative and chemical properties, affect climate, key ecosystems, and all living organisms. The challenge for atmospheric chemistry research in the coming decades is to develop the tools and scientific infrastructure necessary to document and predict the concentrations and effects of these species on local, regional, and global spatial scales and on daily to decadal time scales. These Environmentally Important Atmospheric species are stratospheric ozone. greenhouse gases, photochemical oxidants, atmospheric aerosols, toxics, and nutrients.
The recommended strategies for atmospheric chemistry research include the following:
1. Document the chemical climatology and meteorology of the atmosphere through the development of monitoring networks.
2. Develop and evaluate predictive models for atmospheric chemistry and air quality.
3. Provide assessments of the efficacy of environmental management activities by gathering and assessing air quality data.
4. Develop holistic and integrated understanding of the environmentally important atmospheric species and the chemical, physical, and biological interactions that couple them.
The infrastructure necessary to advance atmospheric chemistry research and applications includes:
• global observing systems,
• surface exchange measurement and ecological exposure systems,
• environmental management systems,
• instrument development and technology transfer programs, and
• facilities for studying condensed-phase and heterogeneous chemistry.
Atmospheric Dynamics and Weather Forecasting Research
Progress in the study of atmospheric interactions that shape weather phenomena has created opportunities to make major advances that will lead directly
to improved weather warnings and predictions. The recommended research includes the following efforts:
1. Optimize observing systems, by better collection and utilization of data over the oceans and determination of optimal combinations of available and new observations.
2. Develop adjoint techniques, that target specific regions of the atmosphere for special observations that will lead to greatly reduced forecast error.
3. Maintain in situ observations, especially by halting deterioration of the global rawinsonde network and other in situ measurements.
4. Emphasize land-atmosphere interactions, for which better observations and understanding may be the key to improved forecasts of convection, precipitation, and seasonal climate.
5. Improve water vapor observations, including more accurate and higher-resolution measurements to improve a wide variety of forecasts.
6. Emphasize seasonal forecasts, which require deeper understanding of the relative importance of internal atmospheric variability and interactions with longer-scale phenomena in the oceans and land.
7. Emphasize tropical cyclone motion and intensity, especially research on the physics of tropical cyclone motion and changes in intensity, research on interactions with the upper ocean layers, and research to delineate optimal combinations of measurement systems for hurricane forecasting.
Upper-Atmosphere and Near-Earth Space Research
Human-induced and natural changes in the upper atmosphere and near-Earth space now portend increasing impacts on the global environment and societal activities. Four areas of scientific research are essential for understanding and mitigating these impacts; thus, upper-atmosphere and near-Earth space research should emphasize the following:
1. Stratospheric processes that affect climate and the biosphere, including the effects of stratospheric aircraft, ozone-depleting chemicals, volcanic emissions, and solar variability.
2. Space "weather," the short-term variability of the near-Earth space environment that has important effects on satellite performance, human health in space, and communication systems and power grid operation.
3. Global changes in the middle and upper atmosphere in response to natural and anthropogenic influences that have significant effects on the lower atmosphere.
4. The effects of solar variability on the global climate system, which may be significant but must be differentiated from other natural influences and from climate effects associated with human activity.
Research to enable operational prediction of space weather should be given high priority and should emphasize the causes of solar variability and models of the solar-terrestrial system.
Climate and Climate Change Research
Climate research aims to understand the physical and chemical basis of climate and climate change in order to predict climate variability on seasonal to decadal and longer time scales, to assess the role of human activities in affecting climate, and to determine the role of climate change in affecting human activities and the environment. The three dominant scientific goals in climate change are:
1. Understand the mechanisms of natural climate variability on time scales of seasons to centuries, and assess their relative significance.
2. Develop climate change prediction, application, and evaluation capabilities, 3. Project changes in the climate system and relate them to human activities.
The highest priority strategies for pursuing these goals are the following:
• Create a permanent climate observing system.
• Extend the observational climate record through the development of integrated historical and proxy data sets.
• Continue and expand diagnostic efforts and process study research to elucidate key climate variability and change processes.
• Construct and evaluate models that are increasingly comprehensive, incorporating all the major components of the climate system.