Aeolus - ESA's Wind Lidar Mission: Overview and First Results

Kurzfassung

Launched on 22 August 2018, Aeolus is the first satellite mission to measure atmospheric wind profiles on a global scale. The wind observations contribute to the improvement in numerical weather prediction (NWP), as they help to close the gap in wind data coverage, especially over the oceans and in the tropics, which has been identified as one of the major deficiencies in the current Global Observing System. For this purpose, it provides profiles of one line-of-sight (LOS) component of the horizontal wind vector from ground throughout the troposphere up to the lower stratosphere with a vertical resolution of 0.25 km to 2 km depending on altitude and precision of 2 m/s to 4 m/s. The obtained near-real-time data allow for greater accuracy of the initial atmospheric state in NWP models and thus improve the quality of weather forecasts as well as the understanding of atmospheric dynamics and climate processes. At the heart of Aeolus is the Atmospheric Laser Doppler Instrument, ALADIN, which is composed of a frequency-stabilized, ultraviolet laser, a 1.5 m-diameter telescope and a highly sensitive receiver. The revolutionary instrument works by emitting short, powerful laser pulses through the atmosphere and collecting the backscattered light from air molecules, particles and hydrometeors which move with the ambient wind. The wind speed is then derived from the frequency difference between emitted and backscattered pulses, which is caused by the Doppler effect, while the travel time of the pulses contains the altitude information. The algorithms and processors needed to derive wind profiles from ALADIN's raw data were developed by a European team of DLR institutes, the software company DoRIT as well as several European meteorological services (ECMWF, Météo-France and the Dutch weather service KNMI). After a four-month commissioning phase dedicated to the initial in-orbit characterization and optimization of the instrument, its data processing, and as such the improvement of the wind data quality, the mission is currently in the transition to its operational phase. During this transition phase, data is released to an extended group of calibration/validation teams in order to receive important data quality assessments and further feedback, e.g. from co-located measurements. This allows for the necessary refinements of the data processing and mission operation in preparation of the official data release which is scheduled for 2019. This presentation provided an overview and status report of the Aeolus mission and presented first impressive results obtained with the first wind lidar in space.