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In Search of Better ForecastsLike ripples from a stone thrown in a pond, a single weather system can influence the atmosphere in far-off places days later. To help chart these effects, NCAR scientists join others to canvass data-sparse areas, such as the central Pacific Ocean, using aircraft, ships, satellites, and other tools. NCAR also participates in field work on a wide range of other weather topics, ranging from winter highway safety to rainfall enhancement. Some of NCAR’s largest field programs are those aimed at improving day-to-day weather prediction. Especially in the wintertime, weather across the United States and other midlatitude nations accompanies a parade of storms known as extratropical cyclones. These swirls of low pressure can bring rain, snow, ice, and wind as they sweep from west to east, pushed by strong jet stream winds aloft. Extratropical cyclones often intensify rapidly offshore, but the limited amount of data at sea hinders the ability of forecasters to accurately predict the movement and strength of the systems. Since the mid-1990s, a series of field projects has examined extratropical cyclones as they approach the U.S. West Coast. NCAR is now part of an international team planning a major field project called THORPEX. The team will study extratropical cyclones and other weather systems in several related experiments throughout North America, especially across the Atlantic and Pacific Oceans. The ultimate goal is to improve weather forecasts in the 1- to 14-day time frame. To help understand and predict hazardous weather—from wind shear to aircraft icing—researchers from NCAR’s applied science groups take specialized instruments to airports, mountaintops, interstate highways, and other at-risk locations throughout the world. Once analyzed, the data help scientists build software to guide decision makers in weather-sensitive arenas. These decision-making tools often return to the field for evaluation and improvement through NCAR's technology transfer process. Much of this work is supported by the Federal Aviation and Federal Highway Administrations. NCAR led a series of landmark field studies in the 1980s on wind shear in and near airports. These studies led to the development of a wind-shear detection and warning system that now guards many U.S. and international airports. More recently, NCAR has played a lead role in field work on turbulence detection at airports in Hong Kong, Colorado Springs, and Juneau, Alaska.
A new program focuses on highway safety, particularly in wintertime. A prototype system, tested in Iowa and Colorado, helps highway maintenance teams determine the most effective timing, materials, and strategies for treating roads. Among the most challenging of weather-related field studies are those that try to determine whether it’s possible to modify the weather through cloud seeding. Despite more than 50 years of effort—and widespread use of cloud seeding by ski resorts, agricultural firms, and others—researchers have struggled to prove that weather modification works well enough to justify its cost. In order to prove the case scientifically, many weather events have to be examined in detail, a task that requires expensive, multiyear field studies. In the National Hail Research Experiment, based at NCAR in the 1970s, scientists found little evidence that cloud seeding affected hail formation in a dependable way. A newer technique for enhancing rainfall, using hygroscopic (water-attracting) nuclei, has been studied since the mid-1990s by NCAR scientists. They have tested this new seeding technology in multiyear randomized cloud seeding programs in Mexico and in the United Arab Emirates. Data from those efforts are still being analyzed, but the initial results appear to be promising. On the flip side, studies by NCAR researchers and colleagues reveal that human activities may be changing snowfall. At Colorado's Steamboat Springs ski area, the Inhibition of Snowfall by Pollution Aerosols (ISPA) team found that pollution could be reducing the size of snow flakes, leading to lower snow accumulations there. < previous | index | next >
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For other kinds of hazardous weather, NCAR scientists have worked
to develop better short-term predictions of unfolding events from
the present to two hours hence for a specific location. Field programs
in the Denver area, the Midwest, Florida, and the Northeast have
improved our understanding of how thunderstorms develop and grow.
That work guided development of an 
