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GCOS Atmospheric Surface ECV: Precipitation Information on liquid water and precipitation rate is used for initialising Numerical weather prediction (NWP) models. A variety of satellites provide complete global NWP coverage, but they present two major challenges. Firstly, the satellite sensors (such as visible/IR imagers on geostationary weather satellites) typically observe quantities (such as cloud height and cloud top temperature) related to precipitation, so algorithms must be developed to get the best estimates from each particular sensor. Secondly, the mix of available data is constantly changing in space and time. The new generation of geostationary imagers, available since the start of EUMETSAT’s Meteosat Second Generation, also allows for the observation of cloud liquid water path and particle size at high temporal resolution (15 min). Microwave imagers and sounders (e.g. AMSR-E) offer information on precipitation of marginal horizontal and temporal resolution, acceptable to marginal accuracy (though validation is difficult). Satellite-borne rain radars (e.g. on TRMM and CloudSat), together with plans for constellations of microwave imagers, offer most potential for improved observations. For regional NWP, no satisfactory precipitation estimates are available from satellites at present, although they are the only potential source of information over the oceans. Geostationary satellites do provide vital information on the location of tropical cyclones. Increasing amounts of useful microwave data – such as those from the TRMM mission – are becoming available. TRMM was dedicated to studying tropical and sub-tropical rainfall and carried the first spaceborne precipitation radar, JAXA’s PR instrument, and NASA’s TMI microwave imager. Data from PR and TMI have provided new insights into the internal composition of tropical thunderstorms associated with hurricanes. NASA, JAXA and partner agencies plan to continue this collaboration in future to develop the Global Precipitation Measurement (GPM) constellation of satellites that will launch from 2013 onwards. The GPM series will provide global observations of precipitation every three hours to help develop the understanding of the global structure of rainfall and its impact on climate. The CNES-ISRO Megha-Tropiques mission will provide further measurements of tropical rainfall; MADRAS, a passive multi-frequency radiometer, will collect data on rain over the oceans. The 94 GHz cloud radars on CloudSat and (from 2013) EarthCARE provide complimentary information on light precipitation. EarthCARE’s Doppler capability will provide additional detail on sedimentation velocities.The CMIS microwave imager/sounder on NOAA's NPOESS missions will be sensitive to various forms of water and moisture in the atmosphere and clouds, and will provide an all weather measurement capability. Future coordination of these satellite programmes, as well as the efforts of the in situ measurement community, was addressed by the Integrated Global Water Cycle Observations Theme (IGWCO) of the IGOS Partnership. The first element of IGWCO is a ‘Coordinated Enhanced Observing Period (CEOP)’ which is taking the opportunity of the simultaneous operation of key satellites of Europe, Japan and USA to generate new data sets of the water cycle. The IGWCO Theme report is available from www.igospartners.org. (Source: CEOS) Satellite Missions, Current and Planned [ECV Matrix Main Page] [About the ECV Matrix] [Reference Documents] [Contact] [Updated December 14, 2010] |
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