Abstract:Assimilation of microwave radiance data has been a significant contributor to the ECMWF atmospheric analysis since the late 1990s. The following two decades have seen a proliferation of microwave radiances assimilated, as the number of sensors and frequencies used have increased. In addition, the gradual move to ‘all-sky’ assimilation has permitted usage of microwave data in meteorologically active areas of the troposphere; these radiances fill in gaps left by other observation types and can significantly improve forecast skill.
First, we quantify the impact of microwave sounders (ATMS, AMSU-A, MHS) on forecast skill by comparing observing systems experiments (OSEs) with different sounders actively assimilated. Then the additional benefit of moving from clear-sky to all-sky assimilation is demonstrated for the case of AMSU-A temperature sounding radiances. Lastly, we consider the future of all-sky sounder assimilation, including the potential use of smaller platforms like TROPICS and the possibility of using even more information from heritage sensors.
