Aeolus, HLOS wind

short overview

Aeolus was an ESA Earth Explorer mission, carrying a Doppler wind lidar that measured the vertical profile of winds. Aeolus was launched in August 2018 and safely re-entered over Antarctica in July 2023. The period of usable data is from 31 August 2018 to 30 April 2023

Aeolus winds come in two different versions, Mie and Rayleigh. The Mie winds are measured by observing the scattering by cloud droplets and aerosols and are only available in optically thin and medium-thin clouds. The horizontal resolution of Mie profiles is 10 km. Rayleigh winds are obtained by measuring the scattering by air molecules in clear air, and have a lower horizontal resolution of 80 km.

Since Aeolus was a non-operational mission, the data need to be downloaded manually from, e.g. ESA's Earth Observation portal, https://aeolus-ds.eo.esa.int/oads/access/ (a registration is needed to download the data).

The data from Aeolus is being processed by the Aeolus DISC team, and the processing has been continously improved throughout the mission lifetime. A final version, covering the full Aeolus data set, will be released in 2028 (using baseline 18, the operational baseline at the time of the satellite's reentry was baseline 13). More details can be found here.

Harmonie changes

To use Aeolus winds, activate them in scr/include.ass by setting LIDAR_OBS to 1

export LIDAR_OBS=1             # LIDAR aeolus hlos wind
[[  $LIDAR_OBS -eq 1  ]] && types_BASE="$types_BASE lidar"

The optimal settings to use for the observation errors of Aeolus data is still an open question. They are reported in the .bufr file which contain the L2B winds, and the limit of when to allow them can be adjusted in src/odb/pandor/module/bator_decodbufr_mod.F90

The main ones to be careful are the upper error limits. The recommended values at the time of writing are

  REAL, PARAMETER    :: error_est_threshold_Mie = 4.5  ! m/s
  REAL, PARAMETER    :: error_est_threshold_Ray = 8.  ! m/s

Future updates

When the follow-on mission, Aeolus-2 (ESA's name) or EPS-Aeolus (EUMETSAT''s name) launches in 2032, these settings will probably have to be revised. The Aeolus follow-on mission will carry a revised version of the previous instrument, providing observations with higher resolution.