Impact study of DMSP F-16 SSMIS radiances in the NCEP global data assimilation system

Masahiro Kazumori


The Special Sensor Microwave Imager Sounder (SSMIS) was launched on October 18, 2003 on board the Defense Meteorological Satellite Program (DMSP) F-16 spacecraft and has been observing radiances from atmosphere and surface of the Earth. The SSMIS instrument is a successor to the DMSP/Special Sensor Microwave Imager (SSMI) series and planned to be onboard DMSP F-16 to F-20 in the transition period from POES and NPOESS. In addition to SSMI surface sensitive channels ranging from 19-37GHz, SSMIS has atmospheric temperature sounding channels in 50- 60GHz range. The atmospheric temperature information from SSMIS is hoped to be as valuable for Numerical Weather Prediction (NWP) as AMSU-A.

However, calibration and validation of DMSP-F16/SSMIS revealed sensor problems in the SSMIS measurements after the launch. The main reasons for the problems are reflector emission and/or scattering and solar contamination of the warm calibration target. The problems cause systematic biases and noise for the temperature sounding channels and make it difficult to use the data in NWP. In order to overcome the problem, the UK Met Office developed a pre-processing for the SSMIS data and has been distributing the pre-processed data to the NWP community since July 2006.

The purpose of this study is to investigate the quality of the pre-processed SSMIS data and the impact on analyses and forecasts in NCEP global data assimilation system. Results show that quality of the temperature sounding channels of the pre-processed SSMIS data are comparable with those of AMSU-A and the assimilation experiments with the SSMIS data brought small improvements in 500 hPa height anomaly correlations when the data were added to the full NCEP global operational observation data set. The improvements were significant in improving forecast busts events during 2006 summer period.