SPECIAL SENSOR MICROWAVE IMAGER/SOUNDER (SSMIS) FUNDAMENTAL DATA REOCRD FOR C3S

R. Huckle¹, T. Hanschmann¹, V. John¹, J. Schulz¹

¹EUMETSAT

The Special Sensor Microwave Imager/Sounder (SSMIS) has been flying on Defence Meteorological Satellite Program satellites since 2003. SSMIS is the successor to the Special Sensor Microwave/Imager (SSM/I), continuing the measurements in the same imager channels and adding additional sounding capabilities. The sounding channels add important information to numerical weather prediction (NWP) and climate re-analysis models. Especially the upper atmospheric sounding channels provide valuable information on the upper stratosphere and mesosphere up to 100 km altitude, which are not well represented in these models. Consequently, those channels, peaking in the mesosphere, are sensitive to the magnetic field via the Zeeman splitting effect. Therefore, it is essential to have access to the magnetic field in those altitudes to utilise the data for NWP. However, the magnetic field information was not provided for all measurements.

Within the framework of the Copernicus Climate Change Service (C3S2), EUMETSAT has created a Level 1c Fundamental Data Record (FDR) for SSMIS, based on data used at the European Centre for Medium Range Weather forecast (ECMWF) and adding relevant magnetic field data. Further, noise equivalent delta temperature (NEdT) of the measurements based on warm and cold calibration target measurements have been computed and added to the FDR. We will present this new FDR, show comparisons against ERA5 data and Microwave Limbs Sounding (MLS) measurements. We will discuss the influence of the Zeeman splitting and the use of different magnetic field sources. Our results show the importance of utilising the magnetic field information. Radiance simulations improve significantly when including the Zeeman splitting effect. This new FDR will help to understand upper atmospheric biases in pre-satellite aera re-analysis.