Upgrade of LSA-SAF Meteosat Second Generation daily surface albedo (MDAL) retrieval algorithm incorporating aerosol correction and other improvements

Abstract

Abstract. MDAL is the operational Meteosat Second Generation (MSG)-derived daily surface albedo product that has been generated and disseminated in near real time by EUMETSAT Satellite Application Facility for Land Surface Analysis (LSA-SAF) since 2005. We propose and evaluate an update to the MDAL retrieval algorithm which introduces the accounting for aerosol effects as well as other scientific developments: pre-processing recalibration of radiances acquired by the SEVIRI instrument aboard MSG and improved coefficients for atmospheric correction as well as for albedo conversion from narrow- to broadband. We compare the performance of MDAL broadband albedos pre- and post-upgrade with respect to three types of reference data: the EPS Ten-Day Albedo product ETAL is used as the primary reference, while albedo derived from in situ flux measurements acquired by ground stations and MODIS MCD43D albedo data are used to complete the validation. For the comparison to ETAL – conducted over the whole coverage area of SEVIRI – we see a reduction in average white-sky albedo mean bias error (MBE) from −0.02 to negligible levels (<0.001) and a reduction in average mean absolute error (MAE) from 0.034 to 0.026 (−24 %). Improvements can be seen for black-sky albedo as well, albeit less pronounced (14 % reduction in MAE). Further analysis distinguishing individual seasons, regions and land covers show that performance changes have spatial and temporal dependence: for white-sky albedo we see improvements over almost all regions and seasons relative to ETAL, except for Eurasia in winter; resolved by land cover we see a similar effect with improvements for all types for all seasons except winter, where some types exhibit slightly worse results (crop-, grass- and shrublands). For black-sky albedo we similarly see improvements for all seasons when averaged over the full data set, although sub-regions exhibit clear seasonal dependence: the performance of the upgraded MDAL version is generally diminished in local winter but better in local summer. The comparison with in situ observations is less conclusive due to the well-known problem of the spatial representativeness of near-ground observations with respect to satellite pixel footprint sizes. Comparison with MODIS at the same locations shows mixed results in terms of change in performance following the proposed upgrade but proves the good quality of the MDAL products in general. Based on the evidence presented in this study, we consider the updated algorithm version to be able to deliver a valuable improvement of the operational MDAL product. This improvement is two-fold: primarily, there is the refinement of the albedo values themselves; secondarily, the increased alignment with the ETAL product is beneficial for those who wish to exploit synergies between EUMETSAT's geostationary and polar satellites to generate data sets based on the LSA-SAF albedo products from the two different missions.

Quantitative assessment of the potential of optimal estimation for aerosol retrieval from geostationary weather satellites in the frame of the iAERUS‐GEO algorithm

“…FCI will provide Earth images from the GEO orbit with additional spectral channels in the visible and near infrared ranges compared to SEVIRI, including a channel sensing the blue wavelength that is of particular interest for aerosol retrieval (Aoun, 2016;Hsu et al, 2013). The simultaneous processing of these new channels, and others already existing on SEVIRI, for inversion may offer new possibilities in aerosol characterization, including the improved estimation of AOD but also the retrieval of additional parameters related to the nature of particles, as well as land surface properties such as albedo (Juncu et al, 2022). In this context, the advanced features of OE that have been evaluated in this paper, mainly the possibility of estimating several variables simultaneously, may become great interest in the future evolution of iAERUS-GEO.…”

Development of a HAMSTER: Hyperspectral Albedo Maps dataset with high Spatial and TEmporal Resolution

“…The SEVIRI land surface albedo product MDAL (Geiger et al, 2008;Juncu et al, 2022, product identifier LSA-101) is offered daily by the Land Surface Analysis (LSA) Satellite Application Facility (SAF) on the native SEVIRI grid with a spatial resolution of 3 km at the sub-satellite point, and is similar to the MODIS-based MCD43C3 product, against which it has been evaluated (Carrer et al, 2010). As for MCD43C3, both the bi-hemispherical (white-sky) and directional-hemispherical (black- We compare the three solar satellite channels offered by SEVIRI with the reconstructed channels from the HAMSTER clima- tology and HAMSTER single day (first three columns in Figs.…”