Integration of GEMS and MODIS AOD for enhanced long-term aerosol monitoring over East Asia

Abstract

Aerosols significantly affect the Earth’s climate system, yet large uncertainties remain in their long-term records. The Geostationary Environment Monitoring Spectrometer (GEMS) provides high-resolution aerosol data over East Asia, but current aerosol optical depth (AOD) retrievals display systematic biases. To improve data quality, we developed a GEMS–Moderate Resolution Imaging Spectroradiometer (MODIS) referenced AOD (GM-AOD) by processing GEMS Level 3 and applying aerosol type and surface-dependent correction functions derived from MODIS AOD. The algorithm incorporates temporal averaging, AMI-based cloud filtering, land/sea classification, and area-weighted gridding. GEMS initially underestimated MODIS with regression slopes of 0.52–0.54 in 2023–2024. After correction, the slopes improved to 0.82–0.84, with the largest improvement in highly-absorbing fine (HAF) and non-absorbing (NA) aerosols. Case studies of dust and biomass burning events confirmed improved consistency while retaining GEMS’ advantage in detecting localized plumes. Validation with the Aerosol Robotic Network (AERONET) yielded a slope of 0.89, demonstrating that GM-AOD provides a reliable, consistent dataset for long-term aerosol and climate studies in East Asia. © 2026 Informa UK Limited, trading as Taylor & Francis Group.