| 13 Oct 2026
Assessment of the PACE/SPEXone Aerosol Layer Height (ALH) Retrievals and Intercomparison with EarthCARE/ATLID Observations
Abstract. Here, we present the first evaluation of the PACE/SPEXone aerosol layer height (ALH) products over oceanic regions, assessing retrievals from the two independent algorithms and their products, RemoTAP and FastMAPOL, against aerosol layer heights derived from EarthCARE/ATLID. The ATLID aerosol layer heights are calculated using a center-of-mass (COM) approach applied to aerosol extinction profiles. The selected oceanic regions provide insight on the PACE/SPEXone ALH retrieval performance, highlighting its sensitivity to the aerosol optical depth (AOD) loading and the aerosol vertical structure. Better agreement is observed over the Mediterranean region, where dust and mixed-dust aerosol types dominate. The RemoTAP and FastMAPOL retrievals show correlation coefficients of R = 0.30 and R = 0.60, with corresponding mean absolute errors of 1.12 and 1.07 km, respectively. Conversely, weaker correlations are found over the South Atlantic and Indian Ocean regions. Overall, global statistics indicate moderate agreement between SPEXone and ATLID ALH products, showing the dependence on the aerosol vertical distribution. We conclude that improved consistency is found for cases with strong agreement between SPEXone and EarthCARE AOD retrievals, particularly under higher aerosol loading conditions (AOD > 0.1). We further examine the impact of different ALH definitions by applying alternative Gaussian-fit approaches to the ATLID profiles, which leads to a slight improvement in the agreement between active and passive ALH estimates.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Measurement Techniques.
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