The National Oceanic and Atmospheric Administration (NOAA) uses precipitation data in many applications including hurricane forecasting. Currently, NOAA uses data collected from the Tropical Rainfall Measuring Mission (TRMM) satellite that was launched in 1997 by NASA in cooperation with the Japan Aerospace Exploration Agency. NASA is now making plans to launch the Global Precipitation Measurement (GPM) mission in 2013 to succeed TRMM, which was originally intended as a 3 to 5 year mission but has enough fuel to orbit until 2012. The GPM mission consists of a "core" research satellite flying with other "constellation" satellites to provide global precipitation data products at three-hour intervals. This book is the second in a 2-part series from the National Research Council on the future of rainfall measuring missions. The book recommends that NOAA begin its GPM mission preparations as soon as possible and that NOAA develop a strategic plan for the mission using TRMM experience as a guide. The first book in the series, Assessment of the Benefits of Extending the Tropical Rainfall Measuring Mission (December 2004), recommended that the TRMM mission be extended as long as possible because of the quality, uniqueness, and many uses of its data. NASA has officially extended the TRMM mission until 2009.

Preliminary models are developed relating 1-minute precipitation rates to commonly available monthly climatology. Regression equations are provided for precipitation rates equal or exceeded 0.1, 0.5, 1.0, and 2.0 percent of the time during a month. Models are developed using a precipitation index (monthly precipitation/number of days per month with precipitation) alone, and the index and monthly mean temperature as estimators. Separate models are presented for tropical and extratropical regimes, with some gain in precision of estimate offset by loss of confidence due to the small amount of data and fewer locations in each subset. The models and regressions are regarded as preliminary, since only 36 months of data are available for four stations. Data for additional stations are being prepared and will be used to refine these models. (Author).

A search for information on short-duration precipitation rates uncovered several sources of data, primarily for North America and Europe. However, the data available, especially for 1-min rainfall rates, are insufficient to permit direct calculation of precipitation-rate frequency distributions for all but a few locations in the world. Since these statistics are needed for a variety of applications, researchers developed models that can be used to estimate 1-min rainfall-rate distributions. Some require climatic data, while others divide the globe into regions, each of which is associated with a representative distribution. A survey of the available data and a comparison of models for determining short-duration precipitation rate distributions is presented, with particular emphasis on 1-min rates. (Author).

Using preliminary statistical relationships between precipitation intensities averaged over 1-min durations and commonly available monthly climatological tabulations of precipitation, rainfall rates for 1.0, 0.5, and 0.1 percent exceedances were computed for weather stations over Europe and Asia for which monthly totals and frequency of daily precipitation were available for the months of January, April, July, and October. Isolines of intensities were drawn delineating regions of low and high rates for each precipitation frequency. These rates may be used for obtaining calculated-risk design criteria for military equipment and for the evaluation of the probability of operational problems when the intensity of precipitation equalled or exceeded with various low probabilities may be critical. (Author).