Aerosol layer height (ALH) retrievals from oxygen absorption bands: intercomparison and validation among different satellite platforms, GEMS, EPIC, and TROPOMI

• Published in: Atmospheric Measurement Techniques
• Main Authors: H. Kim, X. Chen, J. Wang, Z. Lu, M. Zhou, G. R. Carmichael, S. S. Park, J. Kim
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2025
• Subjects: Environmental engineering; TA170-171; Earthwork. Foundations; TA715-787; Aerosol Robotic Network
• Online Access: https://doi.org/10.5194/amt-18-327-2025; https://doaj.org/article/d75caeba10a14db69853294eeac3932e

The vertical distribution of aerosols is crucial for assessing surface air quality and its impact on the climate. Although aerosol vertical structures can be complex, assuming a certain shape for the aerosol vertical profile allows for the retrieval of a single parameter – aerosol layer height (ALH) – from passive remote sensing measurements. In this study, we evaluate ALH products retrieved using oxygen absorption measurements from multiple satellite platforms: the Geostationary Environment Monitoring Spectrometer (GEMS) focusing on Asia, the Earth Polychromatic Imaging Camera (EPIC) in deep space, and the polar-orbiting TROPOspheric Monitoring Instrument (TROPOMI). We use the extinction-weighted aerosol optical centroid height (AOCH) derived from aerosol extinction profiles of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) as the ground truth. The differences due to the inconsistent definitions of ALH in various retrieval algorithms are investigated and eliminated before comparison. We select multiple dust and smoke cases under ideal observational conditions, referred to as “golden days”, for the evaluation. Given the significant role of aerosol optical depth (AOD) in ALH retrieval, we first evaluate the AOD from these retrievals against the ground-based AErosol RObotic NETwork (AERONET). Results show that the GEMS AOD at 440 nm has better agreement with the AERONET AOD of the ∼ 0.9 correlation coefficient ( R ) than that at 680 nm, both of which underestimate with a negative bias. In contrast, EPIC and TROPOMI tend to overestimate AOD by 0.33 and 0.23 for dust cases, while the bias for smoke plumes is small. Evaluation of ALH against CALIOP demonstrates that the EPIC/TROPOMI ALH has good consistency ( R > 0.7) with CALIOP but is overestimated by approximately 0.8 km. The GEMS ALH displays minimal bias (0.1 km) but a slightly lower correlation ( R = 0.64). Intercomparisons between three passive retrievals indicate that GEMS retrievals have a limited consistency with EPIC and TROPOMI of 0.3–0.4 R ...