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Example of Aeolus Rayleigh-clear Level-2B HLOS winds |
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Introduction to Aeolus
ADM-Aeolus is the second of ESA’s Earth Explorer core missions. The 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 30 kmthe 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 track'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 leading the project contracted by ESA to develop (, in close 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 also generate the L2B products in an operational fashion at ECMWF (and provide the products to ESA) and we intend to assimilate the L2B winds in our global NWP model. Aeolus will also provide information on the optical properties of cloud and aerosol (via the L2A product), with ALADIN being a High Spectral Resolution Lidar; the L2A product may be useful for atmospheric composition modelling. ECMWF has contributed to a number of ESA funded data impact studies to assess the potential impact of the Aeolus data. We expect the Aeolus mission to have a positive impact on analysis and forecast quality, in particular for winds in the tropics.
More information on Aeolus can be found at ESA's website.
The L2B processing software
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:
- See ESA's website 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 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
- Aeolus CAL/VAL and Science workshop 2019
- Aeolus CAL/VAL and Science workshop 2020
- Aeolus 3rd anniversary conference in 2022
- Aeolus Science Conference 2023
- 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/
- Documents 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 develop the Aeolus Level-2B wind retrieval software, the main output of which are HLOS wind observations, which are ECMWF and KNMI develop the ADM-Aeolus Level-2B wind retrieval software which produces Horizontal Line of Sight (HLOS) winds suitable for use in NWP and meteorological research. The algorithms are described in Tan et al. ( Tellus, A, 2008, 60, 2, 191-205), however note that there have been many modifications to the software since the reference was writtenRefer to the Algorithm Theoretical Basis document for information about the algorithms (see documentation links below).
Downloading the L2B processing software and documentation
- The ADM- Aeolus Level-2B/C processing documentation (including the Software Release Note, the Algorithm Theoretical Baseline Basis and the Input/Output Data Definitions Interface Control documents) and associated datasets (needed to test the success of the installation) can be freely downloaded from hereis available for download:
Button Hyperlink title Download Aeolus L2B/C documentation and datasets type standard url L2B processor documentation and datasets - The source code can be freely downloaded for free 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 - Any news News on updates to the software, e.g. new planned deliveries, will be is provided here
- Technical Notes prepared for ESA which are related to the L2B/C processing can be downloaded here (they are useful to help understand more about the L2B products)
An artist's impression of the ADM-Aeolus satellite in orbit (courtesy of ESA).
An example of Aeolus L2B Rayleigh-clear wind observations, generated via operating the genuine ground processing upon a realistic simulation of the raw data.
- Aeolus L2B winds have a WMO approved BUFR template:
- 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:
