Dynamical Emissivity for Microwave Radiance Assimilation in Regional NWP: Preparing for the Arctic Weather Satellite and EPS-Sterna

Radiance observations from microwave sounders have become one of the most valuable sources of information that is used in Numerical Weather Prediction (NWP). However, uncertainties in the land (and sea-ice) surface modelization do not permit optimal use of channels that receive a mixed contribution from the surface and the troposphere (i.e., low-peaking channels). In the context of the preparation of the Arctic Weather Satellite (AWS) mission, the HARMONIE-AROME model was run to evaluate the impact of assimilating the low-peaking channels of existing instruments using the so-called “dynamic emissivity method.” The aim of this work was also to build the best possible version of HARMONIE-AROME data assimilation system (3D-Var and 4D-Var) before the launch of the AWS instrument that happened in August 2024 and to be ready to assimilate the data as soon as the instrument was declared operational in June 2025.