The Aeolus wind lidar satellite was launched in 2018 with the aim to mitigate the lack of global wind profile observations for NWP models. The satellite provided unprecedented direct wind profile observations for a period of nearly 5 years. By now various NWP centers conducted data denial experiments that demonstrate a remarkable impact of Aeolus on forecast skill and according to ECMWF the satellite has the largest impact per satellite.

While the overall beneficial impact has now been proven by various studies, the mechanisms leading to forecast improvements still remain to be investigated as the satellite only adds a comparably low number of observations to the global observing system and the observations were associated with relatively high errors (~ 5 m/s for most observations) and low spatial resolution (~100 km for most observations).

Largest improvements were found in the tropics and studies indicate that the improvements are associated with a better representation of tropical waves as well as the correction of systematic structural errors in current NWP models.  This is likely related to the ability of Aeolus to provide wind profile observations in contrast to most other tropical wind observations that are restricted to a single layer as e.g. atmospheric motion vectors. In midlatitudes, there is indication that the largest forecast improvements were associated with the excitation of Rossby wave packets, but details on if and how Aeolus can constrain divergent upper-level winds are still under investigation.

The talk summarizes the status of impact studies with the Aeolus satellite with a particular focus on gaps in our understanding that need to be resolved in view of a planned follow-on European wind lidar satellite mission.