a) Simulator input: "truth" HLOS winds (output of the ECMWF forecast model)
b) A simulation of Aeolus L2B Rayleigh-clear HLOS winds
c) A simulation of Aeolus L2B Mie-cloudy HLOS winds
Example of Aeolus Rayleigh-clear Level-2B HLOS winds |
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Introduction to Aeolus
Aeolus is was the fifth planned 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 around 30 km altitudethe 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 is intended to have a 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. The L2B wind retrieval algorithms have also been developed in the past in collaboration with Météo-France, DLR and LMD/IPSL. ECMWF will generate generated the NRT L2B products operationally and in NRT in during the mission lifetime via the L2/Met PF (Level-2/Meteorological Processing Facility; a part of the mission's Ground Segment), and will disseminate the products . The products were disseminated to ESA for further distribution to users. ECMWF will also convert the L2B Earth Explorer format products to a WMO approved BUFR format and will provide these forwarded them to EUMETSAT for further distribution to the NWP/research community via the GTS and EUMETCast.
ECMWF intend to assimilate operationally assimilated the Aeolus L2B wind observations in ECMWF's global NWP (Numerical Weather Prediction) model if they are able from 9 January 2020 to 30 April 2023. The L2B winds were proven to improve forecast skill. ECMWF has contributed to ESA funded observation impact studies to assess the potential impact of the Aeolus data. We expect the Aeolus mission to and operational assimilation was justified, despite being a demonstration mission. Aeolus winds have a positive impact on analysis and forecast quality, particularly tropical winds, 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 useful for on atmospheric composition modelling. Aeolus will also provide information on the atmosphere's : 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:
- See ESA's website
- An introductory presentation about Aeolus L2B winds: Aeolus_L2B_winds.pptx
- on Aeolus
- Aeolus on twitter
- QJRMS article about the NWP impact of Aeolus at ECMWF: https://doi.org/10.1002/qj.4142
- A conference proceedings article on some of the demonstrated scientific benefits of Aeolus: https://ieeexplore.ieee.org/abstract/document/9554267
- ECMWF web articles about ECMWF operationally assimilating Aeolus winds:
- An ECMWF Technical Memorandum on Aeolus: https://www.ecmwf.int/en/elibrary/19538-nwp-impact-aeolus-level-2b-winds-ecmwf
- An ECMWF newsletter article about the impact of reprocessed wind data:https://www.ecmwf.int/en/newsletter/173/earth-system-science/aeolus-positive-impact-forecasts-second-reprocessed-dataset
- Aeolus was launched on 22 August 2018; this website provided Aeolus is expected to be launched in May 2018; this website provides a log of progress on the satellite up until launch: https://aeolusweb.wordpress.com/
- Aeolus-specific conferences:
- A CAL/VAL rehearsal workshop took place in March 2017
- and the presentations can be found via this web page: http://www.aeolus-calval-2017.org/
- CAL/VAL rehearsal L2B and L2C datasets are available here
- Documents Technical Notes prepared for ESA regarding the L2B/C processing are available here (; which might be useful to help understand the L2B products
- Browse the available Aeolus data from ESA's ground segment
- Automated Aeolus L2B data quality monitoring at ECMWF (no longer useful after the end of mission)
- Monthly Aeolus L2B quality reports by ECMWF (search for Aeolus)
- An introductory talk on Aeolus winds from the EUMETSAT/ECMWF NWP-SAF Satellite data assimilation training course: 03_SAT_TC_Aeolus_winds_MR_v2023.pdf
- An introductory talk about Aeolus L2B winds (possibly now obsolete): Aeolus_L2B_winds.pptx
- A talk on Aeolus NWP impact from the Aeolus Science conference 2023: ECMWF_NWP_impact_Aeol_winds_Rennie_Rhodes_sci_conf.pdf
The L2B processing software
KNMI and ECMWF and KNMI 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. Read 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 v3.00 (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:
Button Hyperlink title Download Aeolus L2B/C documentation and datasets type standard url L2B processor documentation and datasets - The source code (v3.00) can be freely downloaded from from our website (upon acceptance of the licence terms):
Button Hyperlink title Download Aeolus L2B processor package type standard url http://www.ecmwf.int/en/forecasts/software-and-tools/software/aeolus - 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 : 048 48 48 for AEOLUS (see here)
- The satellite instrument ID number is : 130 for the ESA Lidar ALADIN Atmospheric laser Doppler instrument (see here)
An artist's impression of the Aeolus satellite in orbit (courtesy of ESA).
An example of realistically simulated real Aeolus L2B HLOS wind observations, generated by running the actual Ground Segment processing chain (i.e. L0/L1A/L1B/L2B processing) from realistically simulated satellite telemetry data (via the E2S simulator). The simulation runs south through the Indian ocean and considers the attenuation due to clouds (but not aerosol).
winds, from an orbit just to the west of hurricane Dorian on 1 September 2019: