Uncertainties in Kelvin Waves in ECMWF Analyses and Forecasts: Insights From Aeolus Observing System Experiments

Abstract

The European Space Agency Earth Explorer mission Aeolus with the first spaceborne Doppler Wind Lidar onboard provides global coverage of wind profiles twice per day. This paper discusses the impact of assimilating Aeolus winds on the quality of tropical analyses and forecasts using the observing system experiments of the European Centre for Medium-Range Weather (ECMWF). Presented examples show that Aeolus wind profiles bring changes to the Kelvin wave structure in the layers with a significant vertical shear during the easterly phase of the quasi-biennial oscillation in the period May to September 2020. Comparing Kelvin waves in analyses and forecasts with and without Aeolus winds, it is argued that improved ECMWF forecasts in the tropical tropopause layer are due to vertically propagating Kelvin waves.