Calibration/Validation of NOAA-18 AMSU-A and MHS for the Microwave Surface and Precipitation Products System (MSPPS)

The Microwave Surface and Precipitation Products System (MSPPS) project is dedicated to the retrieval of near-real-time operational surface hydrological products using brightness temperatures from the microwave instruments (AMSU-A, AMSU-B and MHS) on board of NOAA's polar orbiting satellites. The launch of the newest NOAA satellite, NOAA-18 on May 20, 2005, presented a new challenge to the MSPPS project due to a new instrument, the Microwave Humidity Sounder (MHS), which replaced the AMSU-B on board of the previous 3 NOAA satellites. The NOAA-18 post-launch work for MSPPS also includes cal/val of the radiances and products.

A major difference between MHS and AMSU-B is the channel lineup with channel 2 and channel 5 for MHS being 157 GHz and 190 GHz vs. for AMSU-B 150 GHz and 183 +/- 7 GHz. In order to generate MSPPS products from MHS data, synthetic AMSU-B data are generated based on MHS at the above two channels. The equations for the conversion were derived pre-launch and were later adjusted based on the match-up data from NOAA-16 AMSU-B and NOAA-18 MHS measurements.

As was the case for the previous AMSU-A sensors placed into operation, a cross-track asymmetry is observed in NOAA-18 AMSU-A radiances and products. The asymmetries in radiances were characterized using forward model calculations and were then corrected. The impacts of the asymmetry on the MSPPS products will be analyzed in the presentation. The NOAA-18 MSPPS products are also validated against other satellites before their operational implementation.