ADM-Aeolus, ESA's Wind Lidar Mission
Straume-Lindner, A.G.; Ingmann, P.; Elfving, A.

The European Space Agency is developing a direct detection Doppler Wind Lidar for the measuring of wind from space. The pulsed UV Lidar, with high spectral resolution capability, shall deliver horizontally projected single line-of-sight wind measurements at 24 vertical layers (0 to 30 km) from each of its two channels; one molecular (clear air) and one particle (aerosol and cloud backscatter) channel. Spin-off products are profiles of atmospheric optical properties.
The instrument will measure the zonal component of the wind field in clear and particle-rich air (aerosol layers and transparent clouds), and down to the top of optically dense clouds. The required accuracy of the wind measurements is 2 m/s in the planetary boundary layer, 2-3 m/s in the free atmosphere, and 3 m/s in the lower stratosphere. The wind observations will be spatially averaged, continuously sampled along the satellite track.
ADM-Aeolus will also deliver height profiles of backscatter and extinction coefficients, scattering ratios and lidar ratios. From these parameters it is possible to retrieve cloud and aerosol information such as cloud-top height, multi-layer clouds and aerosol stratification, cloud and aerosol optical depths (integrated light-extinction profiles), and some information on cloud/aerosol type (lidar ratio). The satellite will fly in a polar dusk/dawn orbit, providing a global coverage of ~16 orbits per day. The wind measurements will be delivered near-real-time (NRT) for direct ingestion into operational numerical weather prediction (NWP) models. Optical properties products will be provided off-line.
During the technical development of the ALADIN laser, changes to a.o. the mission measurement strategy had to be implemented in order to meet the user requirements on stability and measurement accuracy. This has lead to changes in the spatial representativity of the data. As a result of changes to the mission, new impact studies were initiated to consolidate an optimized the on-ground data processing and make best use of the Aeolus data in NWP assimilation systems. Results from these investigations will be shown.
Impact studies have shown that the largest impact of Aeolus is expected in regions with few other direct wind profile observations, e.g. over the oceans, in the Tropics and in the Southern Hemisphere. Climate monitoring based on reanalysis data are expected to benefit from Aeolus observations through improvements of NWP analyses. One example is the detection of wind driven circulation changes in Arctic regions. Climate model processes involving wind dynamics, such as convectively coupled tropical waves, El Niño circulations and Monsoons, could be validated with tropical wind profiles from Aeolus.
The status of the Aeolus mission and its data products will be presented together with results from impact studies, results from campaigns with the Aeolus Airborne Demonstrator (A2D) and the potential for assimilation of Aeolus's spin-off products.