Pre-operational testing and results from direct assimilation of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager Sounder (SSMIS)

On October 18th, 2003, the Defense Meteorological Satellite Program (DMSP) successfully launched a satellite with the first Special Sensor Microwave Imager Sounder (SSMIS) instrument aboard. The SSMIS is a conically scanning passive microwave radiometer that includes seven temperature sounding channels peaking below 30 Km, and seven peaking between 30Km and 80 Km. Two calibration anomalies were discovered. The first was due to nonzero reflector emission contaminating the scene temperatures. The second was due to a solar intrusion onto the warm load calibration target. Both of these anomalies must be corrected before the radiance data can meet the stringent requirements of NWP data assimilation systems.

Several pre-operational tests have been performed at NRL. Control runs consisting of the current operational system (3DVar + 3 AMSU + geostationary winds) set the baseline performance. In the first experiment, data from SSMIS channels sensitive to the tropospheric and stratospheric temperature are added to the operational systems, and evaluated after one month of assimilation. In the second month-long experiment, the data from NOAA-15 AMSU-A is removed from the system, and replaced by SSMIS. This scenario is a risk-reduction test, and will tell us whether SSMIS can substitute for a failed AMSU instrument. Performance of the SSMIS instrument may prove crucial to NWP efforts, given the gap between the expected end of life of the NOAA operational satellites and the launch of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project (NPP) satellite systems. Detailed descriptions and forecast impacts of these experiments will be presented.