GPM is a science mission with broad social applications. Globally distributed, continuous, and high-quality measurements of precipitation accumulation, intensity, and duration will benefit a wide range of basic- and applications-oriented research. This research will have international interest and consequence. GPM makes a significant contribution to theme areas that have been identified by the National Academy of Science's Decadal Study and the international Global Earth Observing System of Systems (GEOSS) effort. If GPM science objectives are met, advances in the following areas (in addition to improved weather, climate, and hydrological prediction) are possible.

World Health. GPM will provide useful precipitation information needed for the health community to

• Identify weather and climate patterns associated with disease outbreaks and
• Advance warnings of outbreaks thereby enabling preventative measures such as vaccination and vector control. Some recent studies have established relationships between environmental factors like precipitation/excess water and outbreaks of diseases such as malaria and yellow fever.
• GPM's global coverage frequency of observations may enable monitoring of short time scale events like hurricane-induced flooding (which causes sewage and waste-related health issues), or disease outbreaks such as the U.S. East Coast West Nile Outbreak of 2001 in regions outside of the tropics.

Homeland Security. GPM can contribute to homeland security activities. Current numerical models are adequate for predicting some aspects of the chemical / biological / nuclear (C/B/N) agent dispersal, but there are still critical gaps. One potential gap is the ability of these models to assess removal of C/B/N agents from the air by rainfall, which is important for quantifying contaminant doses. This would be of particular value in

• Coastal regions, where 60-80% of the U.S. population will be located by 2025;
• Open ocean or lake waters (e.g. Great Lakes region);
• Mountainous or inaccessible terrain regions;
• Urban central business districts; or
• Other countries (e.g. Iraq or Kosovo) where rainfall data are not readily accessible.

Agriculture. The world agriculture community is highly dependent upon accurate precipitation measurements, as well as weather/climate diagnosis and prediction. Such factors as crop growth, health, and yield are directly related to weather, particularly precipitation. Adequate estimates of precipitation amount are important for crop growth assessments. Timing of precipitation is also critical for assessing crop productivity. Organizations like the United States Department of Agriculture (USDA) World Agriculture Outlook Board rely on a myriad of precipitation data sources such as rain gauge networks, radar-derived estimates, and satellite measurements. From these sources, variables like seasonal total rainfall, percentage of normal precipitation, and soil moisture are extracted. GPM will provide an accurate source of precipitation data over regions that have inadequate gauge or radar coverage but are essentially agriculturally-based nations (e.g. in Africa and Asia).

Land Use Change. Land-use change has been identified by U.S. Climate Change Science Program (CCSP), Global Energy and Water Cycle Experiment (GEWEX) Continental ÐScale International Project, and the U.S. Weather Research Program (USWRP) as a factor that determines the amount and distribution of rainfall. Recent publications have shown that short- and long-term precipitation variability, in part, may be linked to land-use change (e.g. urbanization, deforestation) or the presence of atmospheric aerosols (e.g. dust and smoke particles). Additionally, other recent studies have discussed the implications of urban surfaces on surface water runoff and vulnerability of regions to floods. GPM will advance scientific understanding of

• The role of the land-atmosphere interface on controlling rainfall;
• Our ability to study the linkages between cycling of radiation, energy, and atmospheric carbon; and
• Identify precipitation variability linked to aerosols.

Science Education. GPM will stimulate a vibrant public outreach and education effort composed of

• Broadcast and display of real-time global precipitation maps,
• K-12 and college-level Internet-based precipitation data access and educational display-analysis tools,
• Involvement of schools and churches in raingauge-based data collection for micrometeorological verification studies, and
• Creation and distribution of media products.