The committee’s conclusions and recommendations regarding these missions are presented in the sections that follow.


Global Precipitation Measurement

In spite of steady advances in weather predictions and warnings, society is increasingly vulnerable to costly floods and droughts.2 Accurate measurement and prediction of precipitation are essential to reduce this vulnerability and improve the management of water resources. Such measurements can be obtained from spaceborne active microwave sensing (radar), which provides direct, fine-scale observations of the three-dimensional structure of precipitation systems.

The first spaceborne precipitation radar, on the Tropical Rainfall Measuring Mission (TRMM), was launched in 1997 and provided insights into the microphysical dynamics of the formation of precipitation. These measurements led to improved operational forecasts of precipitation and estimates of hurricane storm tracks, which in turn have almost certainly reduced economic losses and saved lives.3 TRMM has already exceeded its planned lifespan, and a replacement, the Global Precipitation Measurement (GPM) mission, will be built in partnership with Japan, Europe, and possibly France and India. GPM will consist of a core satellite with a precipitation radar and an advanced radiometer, accompanied by approximately seven satellites with passive radiometers. The GPM constellation will provide global coverage at 3-hour intervals over most land and ocean areas (latitude 65° S to 65° N).

GPM was originally planned to be launched in 2007, which would have minimized the gap in global precipitation coverage after TRMM ended. However, the current estimated launch date is 2010. The committee is pleased to see that GPM is in NASA’s proposed FY 2006 budget but is concerned that the planned launch date has slipped 3 years since initial planning.

The committee recommends that the Global Precipitation Measurement mission be launched without further delays.

Atmospheric Soundings from Geostationary Orbit

Atmospheric soundings of temperature and water vapor are routinely made from polar-orbiting satellites, and they contribute essential observations for weather forecasting. However, the time between soundings from a single polar-orbiting satellite is approximately 12 hours, and this sampling frequency is too low for observing the development of and the rapid changes associated with severe weather, including tornadoes, flash floods, and hurricanes. High-frequency soundings over the United States are being made from geostationary orbit, and there is a plan to upgrade these and other capabilities in 2012 with the launch of the next-generation operational GOES sounder, GOES-R. The Geostationary Imaging Fourier Transform Spectrometer (GIFTS) is a new technology that is designed to obtain 80,000 closely spaced


For instance, the 1988 central U.S. drought is estimated to have cost $40 billion to $60 billion. See information compiled by NOAA’s National Climatic Data Center at <>. Global flood losses over the last decade have exceeded $200 billion, according to the Munich Reinsurance Company, World Map of Natural Hazards, Munich, Germany, 1998.


Although TRMM data contribute to El Niño predictions, the socioeconomic effects of TRMM-improved forecasts have not yet been quantified. See National Research Council, Assessment of the Benefits of Extending the Tropical Rainfall Measuring Mission: A Perspective from the Research and Operations Communities, Interim Report, The National Academies Press, Washington, D.C., 2005, in press.

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