Advances in Suomi NPP ATMS SDR Life Cycle Reprocessing

The Suomi National Polar-orbiting Partnership (SNPP) satellite was launched on October 28, 2011 and carries the Advanced Technology Microwave Sounder (ATMS) on board. ATMS is a cross-track scanning instrument observing in 22 channels at frequencies ranging from 23 to 183 GHz, permitting the measurements of the atmospheric temperature and moisture under most weather conditions. During the past nearly five years of SNPP on-orbit operations, ATMS SDR teams has submitted several major updates on operational processing of ATMS TDR and SDR products include full radiance calibration, radiance destriping, correction of the flat reflector emission and noise characterization from Allan variance. These updates have been made into JPSS Interface Data Processing Segment (IDPS) ground processing system as well as NOAA/STAR offline processing system. It is found that the ATMS SDR brightness temperatures have smaller biases in upper air sounding channels after the calibration process is switched to the full radiance calibration with the corrected non-linearity sign. It is also found that the ATMS antenna brightness temperature displays a distinct scan angle dependent bias in the NWP O-B field, especially at the window channels. The scan-angle dependence in brightness temperature is directly observed when the ATMS was pitched over to scan the deep space where the radiation is uniform across the scan. The scan angle dependent radiance in cold space may be mostly related to the ATMS flat reflector emission. Thus, a physical model is developed to characterize the flat reflector emission and then retrieve the emissivity from ATMS pitch-over maneuver data. It is shown that ATMS reflector emissivity from K, V, W and G bands is within a range of 0.002 to 0.007. This model allows for reducing the ATMS scan angle dependent bias when it observes the earth scene. To make the lifetime ATMS SDR consistent and provide stable mean status for weather event analysis, ATMS SDR team has planned to perform ATMS lifecycle SDR reprocessing recently. Meanwhile, reprocessed SDR data can help the NWP reanalysis processing for additional global and regional weather event analysis. Both scientific and systematic preparation has been carefully planned and tested to ensure data can be processed in a timely manner. Preliminary analysis on testing data approves that SNPP ATMS SDR life cycle reprocessing data greatly improves the data quality and effectively reduces the O-B bias.