National Academies Press: OpenBook

Weather and Climate: The Report (1975)

Chapter: SPACE APPLICATIONS TO METEOROLOGY

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Suggested Citation:"SPACE APPLICATIONS TO METEOROLOGY." National Research Council. 1975. Weather and Climate: The Report. Washington, DC: The National Academies Press. doi: 10.17226/18685.
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Suggested Citation:"SPACE APPLICATIONS TO METEOROLOGY." National Research Council. 1975. Weather and Climate: The Report. Washington, DC: The National Academies Press. doi: 10.17226/18685.
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Page 6
Suggested Citation:"SPACE APPLICATIONS TO METEOROLOGY." National Research Council. 1975. Weather and Climate: The Report. Washington, DC: The National Academies Press. doi: 10.17226/18685.
×
Page 7
Suggested Citation:"SPACE APPLICATIONS TO METEOROLOGY." National Research Council. 1975. Weather and Climate: The Report. Washington, DC: The National Academies Press. doi: 10.17226/18685.
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SPACE APPLICATIONS TO METEOROLOGY Space and time scales of motion in operational meteorology range over a wide spectrum from local, transitory weather phenomena to global, climatic changes, as outlined in Table I. Table I Range of Meteorological Scales Approximate Area Scale Approximate Time Scale of Influence Local present weather 0 to 2 hours l50 km Short range (mesoscale) 2 to l2 hours l000 km Synoptic l day to l week Hemispheric Long range and climate 2 weeks or more Global The observational methods and the prediction techniques vary markedly throughout the range from the smallest to the largest scale. PRESENT-WEATHER DISPLAY In its l97l report, the Committee on Atmospheric Sciences of the National Academy of Sciences placed a high priority on the development of comprehensive systems for monitoring present weather, with the information being made continu- ously available to broad categories of users. Input data might be derived from satellite and radar observations and from a network of low-cost, unmanned weather stations interrogated by computer. The combined output could be dis- tributed to the general public and other users by television or other communica- tion systems. Information on localized weather for periods of up to 2 hours is becoming increasingly important to the decision-making processes of a wide variety of users. Additionally, the display of local present weather is vital in alerting

the public to hazardous weather. Space platforms offer a practical source of data for the timely display of present-weather information and a possible vehicle for the rapid dissemination of warnings. The wide demand for present-weather data has been demonstrated by the extensive use of the Automatic Picture Transmission (APT) system, now part of the NOAA satellite series. Over l,000 users purchased or constructed specialized ground equipment in order to receive these pictures. This represents a voluntary expenditure of approximately $l0 million. Since this weather data is obtained from low-altitude satellites, it is available only twice daily. The continuous flow of data from geostationary satellite systems would increase manyfold the utility of present-weather information. RECOMMENDATION - The Panel on Weather and Climate reconmends the develop- ment of a low-cost readout system from three-axis-stabilized geostationary satellites for the display of local present weather in real time. This could be part of a broad present-weather information network. To teat the effective- ness of such a system, the Panel recommends that a present-weather pilot project be undertaken in a region that includes both urban and rural areas. SHORT-RANGE FORECASTS A simple extrapolation of the movement of small-scale weather systems, such as thunderstorms, will usually provide a successful weather forecast for only a short period of time, generally l to 2 hours. Beyond this, it will be necessary for meteorologists to devise forecasting methods to modify extrapola- tion. The result will be to change in an appropriate way projections of the direction of motion, the speed, and the rate of development of existing weather systems. With the addition of new forecasting techniques, it is probable that forecasts can be effectively extended to a range of from 3 to 6 hours. In developing these forecasting techniques, it will be important to have information about the vertical structure of the atmosphere in particular local areas where short-term forecasts are to be prepared. An IR-sounding capability from a geostationary platform would be an effective way of obtaining such data. The additional provision of three-axis-stabilization would improve by one order of magnitude the time available for observation and therefore would greatly enhance the capability of the system. Extending forecasts into the 6-hour to l2-hour range will be a more difficult problem and will require increasingly sophisticated models and more extensive observations, especially in the planetary boundary layer. Various experimental studies on this time scale will need to be undertaken. NOAA has recently begun to develop plans for a Severe Environmental Storm and Mesoscale Experiment (SESAME) to be carried out over a 3-year period beginning in l977 or l978. Satellite support of such experimental programs is, of course, highly desirable. RECOMMENDATION - The Panel recommends that NASA develop IR-sounding capabil- ity from the geostationary Synchronous Meteorological Satellite in order to support the development of short-range forecasts of local weather. The develop- ment of a three-axis-stabilized geostationary platform will substantially improve the value of this system.

SYNOPTIC FORECASTS The synoptic-scale dynamics of the atmosphere are becoming better under- stood through international efforts such as GARP. These and similar efforts have made it possible to simulate the general characteristics of the global circulation of the atmosphere by numerical models for periods of l week or longer. Hemispheric operational versions of such models, which have more demand- ing data requirements, have led over the last l5 years to an extension of the effective predictability of synoptic-scale weather from 2 days to 3 days and have permitted the National Weather Service to provide general outlooks of the weather 4 and 5 days in advance. To extend synoptic forecasting capabilities to 5 days or beyond within the next decade, a world-wide atmosphere-ocean observing system is an absolute necessity. By the early l980's GARP results should give better insight into the possibilities of extending synoptic-scale forecasts beyond 5 days and will also provide a critical assessment of the observational requirements necessary to support such extended forecasts. The costs associated with operating a global land-ocean-based synoptic observation network are prohibitively high, on the order of $l billion or more per year. It is obvious that a more effective alternative is a mix of existing land-ocean-based observations and those from a satellite system; this mixed observing system should be capable of monitoring the atmosphere to measure the vertical temperature and humidity structure, the distribution and motion of clouds (from which atmospheric winds can be determined), and sea-surface tempera- ture. An extensive data-relay capability for remote, earth-based automatic stations is also required. RECOMMENDATION - The Panel on Weather and Climate recommends (l) continued support for GARP in order to assess the possibilities of extending synoptic- scale forecasts; (2) continued R&D effort to improve temperature and humidity soundings, measurements of sea-surface temperatures3 measurements of winds using cloud displacements in order to meet the accuracy and resolution requirements set forth for FGGE in l978-79; and (3) continued R&D efforts toward the use of space techniques to provide wind profiles in the equatorial zone with better vertical resolution than is now possible by cloud-tracking methods, inasmuch as the mixed balloon and satellite observing subsystem planned for FGGE may not lend itself to operational use. LONG-RANGE WEATHER AND CLIMATE PREDICTION It now appears that the ability to predict determinately the state of the atmosphere cannot be extended beyond approximately 2 weeks. Hence, the ability to make longer-range forecasts, if possible, may have to be handled in a statis- tical manner. This implies that meteorology will have to develop a different set of mathematical and descriptive tools if it is to attack the problem of long- range weather and climate prediction. This effort is now in its infancy. A treatise is not undertaken here concerning the vital importance of the ability to predict weather on the time scales of months, seasons, and years. Suffice it to say, the consensus of the Panel is that this capability is desper- ately needed by a growing civilization that has seriously strained its food

supplies, natural resources, and distribution systems. Substantial efforts in long-range weather and climate prediction must now begin in order to aid man in coping with the consequences of climatological vagaries (e.g., failure of food and fiber crops). The development and application of a method of long-range weather and climate prediction require a comprehensive understanding of the interactions of the land-air-ocean system. In order to elucidate these interactions, a capability must be developed to observe all important aspects of this complex system. Fortunately, many of the necessary observations are now or will soon be taken on a routine, operational basis (e.g., atmospheric temperature pro- files, water-vapor content, snow-ice cover, and cloud cover). This fortuitous circumstance is a direct result of satellite capabilities developed for GARP. However, some necessary observations are not now being obtained. For instance, there is a need to monitor the energy budget of the earth, for it is the net energy (incoming minus outgoing) that is available to drive the system. For the same reason, the surveillance of the world's oceans must be greatly im- proved, for their great heat capacity and inertia have an importance influence on the atmosphere. Thus, it is important to know the heat content and field of motion of the mixed layer and of the surface winds. The parameters that characterize the climate of the land-air-ocean system must be observed on a global basis over time periods ranging from years to decades. Such observations are perhaps the key to development and verification of predictions of climate. Satellites and related systems offer the only cost- effective hope of obtaining these data but, because of the requirements for longtime records, stringent demands will be imposed on sensor stability, reli- ability, and calibration. The huge amount of data to be collected requires a data-management capability that is not now in existence. (See section entitled "DATA MANAGEMENT," page l7.) Finally, it must be noted that effective pursuit of a climate prediction capability will require an explicit management commit- ment at the highest level of government. RECOMMENDATIONS - The Panel recommends that (Da program of measuring the global radiation budget must be instituted as soon as possible; this must include long-term measurements of solar radiation, albedot and terrestrial IE emission^ (2) ocean-^nonitoring capability must be greatly improved; highest priority should be given to measurement of the heat content and field of motion of the mixed layer and of surface wind; and (3) quantitative surveillance of the atmospheric constituents that play a role in the global radiation balance must be instituted.

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