The Global Precipitation Measurement (GPM) mission is an international partnership led by NASA and the Japan Aerospace Exploration Agency (JAXA). The mission centers on the GPM Core Observatory satellite. This satellite is now 253 miles above earth traveling at 4.3 miles a second in a circular non-sun-synchronous orbit. The GPM satellite will make 16 orbits a day carrying two instruments: the GPM Microwave Imager and the (GMI) and Dual-frequency Precipitation Radar (DPR), an advanced radar/radiometer system that can measure the amount, size, intensity and type of precipitation, from heavy-to-moderate rain to light rain and snowfall. The DPR will return three-dimensional images of precipitation, revealing the internal structure of storms within and below clouds. The Microwave Imager will serve as a calibration tool.
The GPM mission builds on the success of the Tropical Rainfall Measuring Mission (TRMM), a joint NASA and JAXA satellite launched in 1997 that measures precipitation over tropical and subtropical regions of the earth. During World War II scientists developed the ability to use ground-based radar to measure precipitation over land. The TRMM was the first utilization of spaceborn precipitation radar and this has resulted in the advances we’ve seen in the last 20 year in tropical storm monitoring and forecasting.
With its higher orbit and more advanced instruments the GPM Core Observatory satellite will provide even greater coverage of the earth-from the Arctic Circle to Antarctica. GPM Core Observatory will carry the next generation precipitation radar, the Duel-frequency Precipitation Radar (DPR). One of the major advancements of the DPR is the second radar frequency. In addition to the DPR’s Ku-band radar that will measure moderate-to-heavy rain at 13.6 gigahertz, its Ka-band radar will measure frozen precipitation and light rain at 35.5 gigahertz. These measurements, combined with those from other satellites in the constellation, will provide global precipitation observations approximately every three hours.
Measurements from the GMI will also serve as a reference standard for cross-calibration of the other satellites in the GPM constellation that have sensors to provide data. You can read about the transfer of and coordination of all the satellite data in the NASA mission brochure.
The calibrated GPM constellation will provide measurements on the:
• Intensity and variability of precipitation;
• Structure of cloud and storm systems;
• Microphysics of the ice and liquid particles within clouds; and
• Amount of water falling to Earth’s surface.
Observations from the GPM constellation, combined with land-surface data, will improve our knowledge and understanding of our planet’s allowing for the creation of better:
• Weather forecast models;
• Climate models;
• integrated hydrologic models of watersheds; and
• Forecasts of hurricanes, landslides, floods and droughts.
Rainfall and snowfall vary greatly from place to place and over time as weather and climates change. Satellites can provide more uniform observations of rain and snow around the globe than ground instruments, especially in areas where surface measurements are difficult to take, for example over the oceans and in extreme altitudes. The GPM mission will help scientists understand how local, regional and global precipitation patterns change over time. The GPM Core Observatory satellite is designed to serve for 3 years and carries 5 years of fuel.
The distribution of water in the atmosphere and how it moves, changing between its solid, liquid and gaseous forms, is a powerful vehicle for redistributing Earth’s energy and influences the behavior of the planet’s weather, climate and other environmental systems. Lack of full data and understanding of the water cycle has hindered the ability of scientists to develop accurate models to forecast weather and climate. We cannot predict weather accurately more than a few days out and all the climate models have failed to demonstrate any ability to forecast the future. Now, there is hope of using the collected data to develop a better understanding of our planet and to ultimately build predictive models of our weather and climate. Mission Video
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