First assessment of Aeolus Standard Correct Algorithm particle backscatter coefficient retrievals in the eastern Mediterranean

Abstract. Since 2018, the Aeolus satellite of European Space Agency (ESA) has acquired wind HLOS (horizontal line-of-sight) profiles throughout troposphere and up to lower stratosphere, filling a critical gap in Global Observing System (GOS). Aeolus, carrying ALADIN (Atmospheric LAser Doppler INstrument), first UV HSRL (High Spectral Resolution Lidar) lidar ever placed space, provides also vertically resolved optical properties particulates (aerosols clouds). The present study focuses on assessment L2A particulate backscatter coefficient (baseline 2A11), retrieved by Standard Correct Algorithm (SCA), eastern Mediterranean, region hosting variety aerosol species. Ground-based retrievals instruments operating Athens (central Greece), Thessaloniki (northern Greece) Antikythera (southwestern serve as reference. All stations provide routine measurements PANACEA (PANhellenic infrastructure for Atmospheric Composition climatE chAnge) network. A set ancillary data, including sun-photometric observations (AERONET), reanalysis products (CAMS MERRA-2), (MSG-SEVIRI MODIS Aqua) backward-trajectories modelling (FLEXPART), is utilized towards an optimum characterization probed atmospheric conditions under absence classification scheme SCA profiles. First, emphasis given specific scenarios over island. Due misdetection cross-polar component backscattered signal, underestimates 33 % when non-spherical mineral particles are recorded (10 July 2019). good performance revealed 3 2019, horizontally homogeneous loads fine spherical confined below 4 km. For other two cases (8 2020 5 August 2020), due noise issues, degrades terms depicting stratification layers composed different origin. According statistical analysis 43 identified cases, poor-to-moderate unfiltered plus clouds) profiles, which improves substantially cloud-contaminated excluded from collocated sample. This improvement evident at both vertical scales (regular have 24 bins mid-bin 23 bins), it justified drastic reduction bias (from 0.45 0.27 Mm−1 sr−1 0.69 0.37 mid-bin) root mean square error 2.00 1.65 1.88 1.00 scores. In vertical, lowermost either contamination surface signals or increased levels retrievals. Among three stations, best agreement found remote site with respect urban sites Thessaloniki. Finally, all key Cal/Val (calibration validation) aspects necessary future relevant studies, recommendations possible follow-on mission overview ongoing related activities thoroughly discussed.