PERFORMANCE ASSESSMENT OF NEW MICROWAVE SOUNDERS WITH ALL-SKY NWP MONITORING

D. Duncan1, N. Bormann¹, C. Accadia², S. Di Michele²

¹ECMWF, ²EUMETSAT

Launched in August of 2024 and 2025 respectively, the Arctic Weather Satellite (AWS) and Metop-D each carry a new, state-of-the-art microwave sounder designed for assimilation in numerical weather prediction (NWP) models. By analysing observed radiances against the reference of an NWP model short-range forecast, the radiometric performance of newly launched microwave sounders can be quickly and accurately assessed. In this study, radiances from AWS and the MicroWave Sounder (MWS) on Metop-D are assessed using the ECMWF NWP model as a reference. Biases for AWS and MWS are compared to equivalent channels on heritage microwave sounders such as ATMS using the NWP model as the transfer standard; radiometric noise performance (NEDT) is also compared for temperature sounding channels. This method uses all-sky radiative transfer for the forward model simulations with RTTOV-SCATT v14, and applies a symmetric screening of heavily cloud-affected scenes to remove scenes with known systematic biases from the cal/val analysis. In contrast to other methods of assessing the performance of a newly launched radiometer, the NWP method allows millions of data points to be analysed in a matter of hours, covering a wide range of temperatures and atmospheric conditions. For newly observed spectral regions such as the 325 GHz sub-mm band on AWS, the NWP method provides an invaluable point of comparison due to the lack of other references.