This study aims to provide instantaneous retrievals of aerosol content from SEVIRI observations.
Satellite remote sensing is a unique tool to study atmospheric aerosols and their impacts. The AERUS-GEO (Aerosol and surface albEdo Retrieval Using a directional Splitting method-application to GEOstationary data) approach developed by the Centre National de Recherches Météorologiques (CNRM – Météo France) efficiently processes SEVIRI/MSG observations for the estimation of aerosol properties.
The retrieval strategy is based on the directional and temporal inspection of the satellite signal in order to separate aerosol and surface contributions. The aerosol and surface associated medium is represented by a kernel driven model. A Kalman filter approach is used for the mathematical inversion of this model and for the propagation in time of the retrievals and the associated uncertainties.
The AERUS-GEO products include a daily-averaged Aerosol Optical Thickness (d-AOT) at 0.63 micrometers and the corresponding Angström exponent.
Although a wealth of information is provided by the AERUS-GEO products, studies suggest that a 30% departure is possible between daily-averaged AOT values and the instantaneous aerosol content along the day.
Furthermore, instantaneous estimates of aerosol properties are demanded by the climate and weather communities. In this context, efforts are currently made by the CNRM laboratory towards the retrieval of instantaneous AOT (i-AOT) from SEVIRI data. With this purpose, the AERUS-GEO algorithm is being adapted to retrieve the aerosol content corresponding to each SEVIRI acquisition, which will in turn provide the diurnal cycle of aerosols.
This work is also intended to serve as a basis for the future evolution of AERUS-GEO to process data from the FCI instrument on board MTG.
The goal of this study is to provide instantaneous retrievals of aerosol content from SEVIRI observations. A new version of the AERUS-GEO algorithm, named i-AERUS-GEO, will be developed to provide i-AOT based on the prototype that was developed in an earlier EUMETSAT Federated Activity (LSA-SAF_2015-02).
The Kalman filter within the inversion approach will also provide reliable uncertainties related to the aerosol retrievals. These uncertainties will depend on the appropriateness of SEVIRI observations for aerosol retrieval in terms of solar and view geometries, surface albedo and other parameters.
The evaluation of i-AERUS-GEO will be done through the comparison of the retrieved i-AOT values with ground measurements from the AERONET network. The consistency between daily and instantaneous retrievals, as well as the meaningfulness of the estimated Angström Exponent, will also be evaluated. For this exercise, 10 years of SEVIRI data will be processed along with the required ancillary inputs. Results will be evaluated over the AERONET stations enclosed in the MSG full disk according to data availability. The evaluation will also be extended to other satellite aerosol products such as the GRASP retrievals that are obtained from PARASOL data.
In summary, the objective of this study is to develop an algorithm prototype for the estimation of i-AOT based on MSG/SEVIRI observations. The advantages and limitations of this new approach will be detailed at the end of the project. Furthermore, recommendations will be made for the future adaptation of AERUS-GEO for the retrieval of aerosol properties from the future FCI instrument on board MTG.
|WP1||Method improvement for an instantaneous version of AERUS-GEO.|
|WP2||Processing of a long period of SEVIRI data with the daily and instantaneous version of AERUS-GEO.|
|WP3||Evaluation of the results.|
|WP4||Preparation of the final report and recommendations.|
|Phase||Date and location|