Evaluating Radiometric Stability of SNPP/ATMS for Climate Change Monitoring

Observations from the satellite microwave sounders play a vital role in measuring the long-term temperature trends for climate change monitoring. The longest satellite observations of the atmospheric temperature were from the Microwave Sounding Unit (MSU) on board the historical NOAA TIROS-N polar-orbiting satellite series during 1978–2006. Since 1998 until the present, the Advanced Microwave Sounding Unit-A (AMSU-A) on board the NOAA-KLM series, NASA Aqua, and European MetOp series have replaced MSU to provide temperature observations with higher vertical and horizontal resolutions. The Advanced Technology Microwave Sounder (ATMS) being flown on the current Suomi National Polar-orbiting Partnership (SNPP) and NOAA-20 and to be flown on future NOAA Joint Polar Satellite System (JPSS) is the new generation of the microwave sounders. ATMS as the new microwave sensor, a fundamental requirement is to understand and characterize its radiometric accuracy and stability for its subsequent applications in numerical weather prediction and climate change monitoring. This study compares ATMS with AMSU-A onboard Aqua and MetOp-A satellites which have stable orbits as the SNPP. The similar overpass timing between SNPP and Aqua naturally removes most of the diurnal differences between SNPP/ATMS and Aqua/AMSU-A. Direct comparisons between the two instruments provide information on their radiometric stability. On the other hand, comparisons between SNPP and MetOp-A with different stable orbits provide information on asymmetric temperature trends between day and night observations. This study provides radiometric stability for most atmospheric channels for the SNPP/ATMS and Aqua/AMSU-A based on their comparisons. We also provide trend results in the diurnal temperature range in the lower and middle troposphere during 2012-2018 based on the SNPP and MetOp-A comparisons. These results suggest new capabilities for the ATMS in climate change monitoring. Based on the results, a perspective to merge the ATMS with the AMSU-A for long-term trend monitoring will be provided.