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3 Opportunities for Advancing Mesoscale Meteorological Research and Its Applications The foregoing chapter has documented the extensive efforts being carried on within federal agencies, national laboratories, and universities in the area of mesoscale meteorological research. It is apparent from the survey that impres- sive advances have been and are being made in developing new techniques for observing mesoscale phenomena; in gathering, analyzing, and interpreting specially acquired data sets; and in constructing theoretical and numerical models of the phenomena. It is also apparent that technological advances in data processing, display, and communications have reached the point where the benefits of research can be put to practical use in making improved warnings and predictions of mesoscale events of great economic significance. Despite the steady progress that has taken place in recent years, the meso- scale research effort, like many areas of scientific research, has tended to be fragmented, to be guided more by agency missions and the interests of in- dividual investigators than by a common goal of overriding importance. How- ever, in mesoscale meteorology, such a goal is now emerging as a consequence of the advances outlined above, namely, the goal of improved understanding and prediction of mesoscale phenomena by application of dynamical and numerical methods. Improved prediction and warning of severe thunder- storms, tornadoes, flash floods, and a variety of freezing precipitation events associated with winter storms would pay dividends in agriculture, transporta- tion, construction, and other industries as well as reduce the number of in- juries and deaths associated with these mesoscale weather phenomena. We do not underestimate the difficulties that stand in the way of achieving this goal. They are indeed more formidable than those that confronted the meteorolo- gists of the 1950's as they embarked on their quest for numerical prediction of large-scale weather. But it is precisely because of the difficulties involved 24

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Opportunities for Advancing Mesoscale Meteorological Research and Its Applications 25 that the establishment of a more vigorous and concerted effort, focused on the goal of improved short-range weather prediction and communication sys- tems, is warranted at this time. Not all mesoscale research would be included in such an effort. Agencies may well have specialized tasks that are best handled individually. However, for the achievement of the central objective, it is evident that there would be significant advantages to a pooling of resources and talents. Progress would al- most surely be accelerated by proceeding according to a well-conceived plan of coordinated research. Moreover, several federal agencies are now involved in a program (NEXRAD) to upgrade the national weather radar network, which is nearly 40 years old, with modern, quantitative reflectivity and Doppler radars. Similar improve- ments are under way for satellite and surface measuring systems. A coordi- nated national mesoscale research effort would provide the scientific basis for these hardware programs and for the interpretation of the vast quantities of data that they will provide, and it would enable the training of the generation of meteorologists and engineers that will be responsible for the operational use of these new systems in the future. In view of the difficulties that stand in the way of achieving the long-term goal and the urgent need for short-term progress, it is envisaged that a coor- dinated program of mesoscale research would entail two components: a basic research arm and an applied arm. The basic research arm would be concerned with increasing fundamental knowledge and understanding of mesoscale phenomena and developing an enhanced capability for numerical modeling. The applied component would serve as liaison between the basic research com- ponent and the operational branches of the federal agencies. It would be de- voted to transferring to operations the scientific and technological advances as they become available and to the development of improved systems of communicating weather information to the public. An important part of the basic research component, requiring early imple- mentation, would be the conduct of well-chosen field programs designed to provide the data needed for developing a deeper understanding of mesoscale systems and for testing and improving numerical models. Because of the mani- fold nature of the phenomena embraced by the term mesoscale meteorology, only a limited number of problems could be selected for initial investigation. In establishing priorities among the various possible mesoscale experiments, highest consideration should be given to the depth and breadth of the sci- entific advances that are likely to stem from the choice of a particular phe- nomenon and the second highest consideration to the practical or economic importance of the experiment. Among the topics for field experimentation that have been singled out as deserving special attention by participants in recent workshops related to mesoscale meteorology are the following:

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26 CURRENT MESOSCALE METEOROLOGICAL RESEARCH • Mesoscale aspects of extratropical cyclones in all seasons. Extra tropical cyclones dominate day-to-day weather throughout midlatitudes. Although the sizes and lifetimes of extratropical cyclones are synoptic scale, the important weather (clouds, precipitation, squall lines, convective systems, freezing rain areas) belong to the mesoscale. Carefully coordinated theoretical and observa- tional studies of the mesoscale aspects of extratropical cyclones in all seasons and in different regions of the country are required, with particular emphasis on precipitation processes. • Convective storms and severe local storms. Convective storms provide essential, beneficial rain to the United States. However, under special condi- tions, they produce flash floods, hail, damaging winds, and tornadoes. There is evidence that, far from being random, unpredictable phenomena, the loca- tion and timing of these convective systems is determined by a combination of large-scale processes that are predictable several days in advance and smaller- scale physical processes associated with energy sources at the surface. Con- tinued, vigorous investigation of mesoscale convective systems by observa- tional and numerical simulation methods is essential in view of the importance of severe storms. • Meteorology over complex terrain. Because of its relevance to energy development, air quality, water conservation, and agricultural meteorology, the flow of air and precipitation patterns over mountainous terrain and coastal areas is a crucial problem. Comprehensive data sets and model validation studies are required. There is evidence that this problem is technologically solvable, but increased resources and much closer interagency cooperation are needed. A fourth important area of mesoscale meteorological research is concerned with the understanding and prediction of tropical cyclones. Although the en- tire circulation of tropical cyclones belongs to the synoptic scale, the high- energy portion of these storms and the rainfall, which has both beneficial and destructive properties, are mesoscale features. In addition, the primary energy source, the release of latent heat of condensation, occurs in mesoscale con- vection. In contrast to the three areas of mesoscale research emphasized above, tropical cyclone research is well coordinated and is proceeding satisfactorily. In view of the potential for catastrophic destruction and loss of life associ- ated with a major hurricane, continued extensive research efforts are well justified. For the purpose of facilitating the practical application of scientific and technological advances, it is envisaged that prototype experiments would also be carried out in the applied research area. The Prototype Regional Observa- tion and Forecasting Service (PROFS) being conducted by NOAA is an ex- ample of such an experiment.

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Opportunities for Advancing Mesoscale Meteorological Research and Its Applications 27 As stated above, we view an effective national program in mesoscale re- search to entail both basic and applied components. To the degree possible, these two arms of the program should be mutually reinforcing. When feasible, basic field research programs should have applied components that will take advantage of the special observations to test emerging technologies and meth- ods. By the same token, experiments or pilot studies that are primarily applied or semioperational in nature may also include some basic research elements, particularly in the area of instrument development.