06 Apr 2022
06 Apr 2022
Status: this preprint is currently under review for the journal ACP.

Monitoring multiple satellite Aerosol Optical Depth (AOD) products within the Copernicus Atmosphere Monitoring Service (CAMS) data assimilation system

Sebastien Garrigues1, Samuel Remy2, Julien Chimot3, Melanie Ades1, Antje Inness1, Johannes Flemming1, Zak Kipling1, Istvan laszlo4, Angela Benedetti1, Roberto Ribas1, Soheila Jafariserajehlou3, Bertrand Fougnie3, Shobha Kondragunta4, Richard Engelen1, Vincent-Henri Peuch1, Mark Parrington1, Nicolas Bousserez1, Margarita Vazquez Navarro3, and Anna Agusti-Panareda1 Sebastien Garrigues et al.
  • 1ECMWF, Reading, RG2 9AX, UK
  • 2HYGEOS, Lille, France
  • 3EUMETSAT, Darmstadt, 64295, Germany
  • 4Center for Satellite Applications and Research, NOAA/NESDIS, College Park, USA

Abstract. The Copernicus Atmosphere Monitoring Service (CAMS) provides near real time forecast and reanalysis of aerosols using the ECMWF Integrated Forecasting System with atmospheric composition extension, constrained by the assimilation of MODIS and PMAp Aerosol Optical Depth (AOD). The objective of this work is to evaluate two new near real time AOD products to prepare their assimilation in CAMS, namely the Copernicus AOD from SLSTR (collection 1) on board Sentinel 3-A&B over ocean and the NOAA EPS AOD (v2.r1) from VIIRS on board S-NPP and NOAA-20 over both land and ocean. The differences between MODIS (C6.1), PMAp (v2.1), VIIRS (v2.r1) and SLSTR (C1) AOD as well as their departure with the modelled AOD were assessed at the model grid resolution (i.e. level-3), using 3-month AOD average (December 2019–February 2020 and March–May 2020).

VIIRS and MODIS show the best consistency across the products, which is explained by instrument and retrieval algorithm similarities. VIIRS AOD is frequently lower over the ocean background and higher over biomass burning and dust source land regions compared to MODIS. VIIRS shows larger spatial coverage over land and resolves finer spatial structures such as the transport of Australian biomass burning smoke over the Pacific which can be explained by the higher spatial resolution of the VIIRS level-2 product and the use of a heavy aerosol detection test in the retrieval algorithm. Our results confirm the positive offset over ocean i) between TERRA/MODIS and AQUA/MODIS due to the non-corrected radiometric calibration degradation of TERRA/MODIS in the dark target algorithm and ii) between SNPP/VIIRS and NOAA20/VIIRS due to the positive bias in the solar reflective bands of SNPP/VIIRS. SLSTR AOD shows much smaller level-3 values than the rest of the products which is mainly related to differences in spatial representativity at the IFS grid spatial resolution due to the stringent cloud filtering applied to the SLSTR radiances. Finally, the geometry characteristics of the instrument, which drive the range of scattering angles sampled by the instrument, can explain a large part of the differences between retrievals such as the positive offset between PMAp data sets from METOP-B and METOP-A.

Sebastien Garrigues et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-176', Anonymous Referee #1, 20 Apr 2022 reply
    • AC1: 'Reply on RC1', Sebastien Garrigues, 17 May 2022 reply

Sebastien Garrigues et al.

Sebastien Garrigues et al.


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Short summary
The Copernicus Atmosphere Monitoring Service (CAMS) provides global monitoring of aerosols using the ECMWF forecast model constrained by the assimilation of satellite Aerosol Optical Depth (AOD). This work aims at evaluating two new satellite AOD to enhance the CAMS aerosol global forecast. It highlights the spatial and temporal differences between the satellite AOD products at the model spatial resolution which is an essential information to design multi-satellite AOD data assimilation schemes.