Example of Aeolus Rayleigh-clear Level-2B HLOS winds

Aeolus was the fifth satellite in the Living Planet Programme of the European Space Agency after being launched on 22 August 2018. The mission's objective is to provide profiles of high-quality wind observations from the surface to the lower stratosphere, using a Doppler wind lidar (DWL) instrument (known as ALADIN) in a near-polar sun-synchronous, dawn-dusk orbit at around 320 km altitude. The wind information is the horizontal line-of-sight (HLOS) component, in the direction perpendicular to the satellite's velocity. The mission surpassed its minimum lifetime of three years (lasting nearly five years) after de-orbiting on 28 July 2023.

ECMWF is contracted by ESA to develop, in collaboration with KNMI, DLR and other partners of the Aeolus DISC the Aeolus Level 2B/C (L2B/C) processing software i.e. the wind retrieval. ECMWF generated the NRT L2B products during the mission lifetime via the L2/Met PF (Level-2/Meteorological Processing Facility; a part of the mission's Ground Segment). The products were disseminated to ESA for further distribution to users. ECMWF also convert the L2B Earth Explorer format products to a WMO approved BUFR format and forwarded them to EUMETSAT for further distribution to the NWP/research community via the GTS and EUMETCast.

ECMWF operationally assimilated the Aeolus L2B wind observations in ECMWF's global NWP (Numerical Weather Prediction) model from 9 January 2020 to 30 April 2023. The L2B winds were proven to improve forecast skill and operational assimilation was justified, despite being a demonstration mission. Aeolus winds have a positive impact on analysis and forecast quality, particularly in the tropics and polar areas, particularly where conventional wind profiles are absent. The intention is to hopefully use reprocessed datasets in future ECMWF produced reanalyses.

Given that ALADIN is a High Spectral Resolution Lidar, it is also possible to derive information on atmospheric composition: cloud and aerosol optical properties (particle backscatter and extinction coefficients, via the Level-2A product). This is also being researched at ECMWF for the benefit of the CAMS model.

Further information and publications on Aeolus:

The L2B processing software

KNMI and ECMWF develop the Aeolus Level-2B wind retrieval software, the main output of which are HLOS wind observations, which are suitable for use in NWP and meteorological research. Refer to the Algorithm Theoretical Basis document for information about the algorithms (see documentation links below).

Downloading the L2B processing software and documentation

  • The Aeolus Level-2B/C processing documentation (including the Software Release Note, the Algorithm Theoretical Basis and the Input/Output Data Definitions Interface Control documents) and associated datasets (needed to test the success of the installation) is available for download: Download Aeolus L2B/C documentation and datasets
  • The source code can be freely downloaded from from our website (upon acceptance of the licence terms):  Download Aeolus L2B processor package
  • News on updates to the software, e.g. planned deliveries, is provided here
  • Aeolus L2B winds have a WMO approved BUFR template:
    • See here for the BUFR template. Search for "Atmospheric Laser Doppler Instrument (ALADIN) L2b data", table reference = 3 40 013. 
    • The satellite identifier number is 48 for AEOLUS (see here)
    • The satellite instrument number is 130 for the ESA Lidar ALADIN Atmospheric laser Doppler instrument (see here)
  • Some guidance for NWP users on the L2B BUFR data

An example of real Aeolus L2B HLOS winds, from an orbit just to the west of hurricane Dorian on 1 September 2019: