Statistical validation of Aeolus L2A particle backscatter coefficient retrievals over ACTRIS/EARLINET stations on the Iberian Peninsula
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AuthorAbril Gago, Jesús; Guerrero Rascado, Juan Luis; Bravo Aranda, Juan Antonio; Bermejo Pantaleón, Diego; Granados Muñoz, María José; Ortiz Amezcua, Pablo; Jiménez Martín, Marta María; Alados Arboledas, Lucas
Abril-Gago, J... [et al.]: Statistical validation of Aeolus L2A particle backscatter coefficient retrievals over ACTRIS/EARLINET stations on the Iberian Peninsula, Atmos. Chem. Phys., 22, 1425–1451, [https://doi.org/10.5194/acp-22-1425-2022], 2022.
SponsorshipESA project "Aeolus L2A aerosol and cloud product validation using the European Aerosol Research Lidar Network EARLINET" 5166; European Commission 654109 871115 796539; GRASP-ACE 778349; Spanish Government CGL2015-73250-JIN CGL2016-81092-R CGL2017-83538-C3-1R CGL2017-90884-REDT PID2019-103886RB-I00 PID2020117825GB-C21 PID2020-120015RB-I00; Unity of Excellence "Maria de Maeztu" - Spanish State Research Agency (AEI) MDM-2016-0600; national Portuguese funds, through FCT -Fundacao para a Ciencia e Tecnologia, I.P. UIDB/04683/2020 UIDP/04683/2020 PTDC/CTAMET/29678/2017 0753_CILIFO_5_E; Junta de Andalucia P18-RT-3820; Marie Sklodowska-Curie Action Cofund 2016 EU project - Athenea3i grant 754446; National Science Centre, Poland DEC2021/40/C/ST10/00023
The Global Observing System (GOS) has encountered some limitations due to a lack of worldwide real-time wind measurements. In this context, the European Space Agency (ESA) has developed the Aeolus satellite mission, based on the ALADIN (Atmospheric Laser Doppler Instrument) Doppler wind lidar; this mission aims to obtain near-real-time wind retrievals at the global scale. As spin-off products, the instrument retrieves aerosol optical properties such as particle backscatter and extinction coefficients. In this work, a validation of Aeolus reprocessed (baseline 10) co-polar backscatter coefficients (beta(part)(Aeolus)) is presented through an intercomparison with analogous ground-based measurements taken at the ACTRIS (Aerosols, Clouds and Trace gases Research InfraStructure Network)/EARLINET (European Aerosol Research Lidar Network) stations of Granada (Spain), Evora (Portugal) and Barcelona (Spain) over the period from July 2019 until October 2020. Case studies are first presented, followed by a statistical analysis. The stations are located in a hot spot between Africa and the rest of Europe, which guarantees a variety of aerosol types, from mineral dust layers to continental/anthropogenic aerosol, and allows us to test Aeolus performance under different scenarios. The so called Aeolus-like profiles (beta(part)(Aeolus) (like, 355)) are obtained from total particle backscatter coefficient and linear particle depolarization art ratio (delta(part)(linear)) profiles at 355 and 532 nm measured from the surface, through a thorough bibliographic review of dual-polarization measurements for relevant aerosol types. Finally, the study proposes a relation for the spectral conversion of delta(part)(linear), which is implemented in the Aeolus-like profile calculation. The statistical results show the ability of the satellite to detect and characterize significant aerosol layers under cloud-free conditions, along with the surface effect on the lowermost measurements, which causes the satellite to largely overestimate copolar backscatter coefficients. Finally, the Aeolus standard correct algorithm middle bin (SCAmb) shows a better agreement with ground-based measurements than the standard correct algorithm (SCA), which tends to retrieve negative and meaningless coefficients in the clear troposphere. The implementation of Aeolus quality flags entails a vast reduction in the number of measurements available for comparison, which affects the statistical significance of the results.