Operational DMSP SSMIS Sounding Products at FNMOC

The Defense Meteorological Satellite Program (DMSP) has launched three SSMIS (Special Sensor Microwave Imager/Sounder) sensors onboard F-16, F-17, and F-18. The most recent one, F-18, was launched on Oct.18, 2009. The SSMIS employs a conical scan geometry for temperature soundings of the lower and upper atmosphere at 50-59GHz and 60~63GHz respectively. The humidity sounding channels for lower atmosphere are at 150~183GHz with surface image channels between 19-91GHz. As one of the major operational DMSP data ingest centers, the US Navy's Fleet Numerical Meteorology and Oceanography Center (FNMOC) processes, generates and distributes SSMIS sounding and surface Environment Data Records (EDRs) from the SSMIS Ground Processing System (GPS). Two major calibration anomalies, solar intrusion into the warm load and large reflector thermal emission, have been discovered during the post-launch SSMIS calibration and validation (Cal/Val) analysis. To mitigate the calibration anomalies, the SSMIS Unified Pre-Processor (UPP) was developed as part of a joint effort between the Naval Research Laboratory (NRL) and the UK Met Office. The UPP was operationally implemented at FNMOC in April, 2008 and has been updated several times since then. The current operational version of SSMIS UPP performs many functions and corrections: warm-load intrusion to the radiometer gain, scan non-uniformity, reflector emission, Gaussian scene averaging, and residual Doppler scan bias removal. The Gaussian scene averaging reduces the scene noise to a level of suitable for radiance assimilation. The ASCII and BUFR output files generated by the SSMIS UPP are distributed to major operational numerical weather prediction (NWP) centers for data assimilation. The corrected SSMIS temperature data record (TDR) observations from F-16, F-17, and F-18 lower atmospheric sounding channels have been assimilated into the Navy Operational Global Atmospheric Prediction System (NOGAPS) model. The assimilation of SSMIS data has increased the forecast skill of NOGAPS significantly. These results, as well as the specifics of the SSMIS UPP, will be presented.