The impact of aerosol on MODIS cloud detection and property retrieval in seriously polluted East China

Previous researches proved that aerosols have a significant influence on the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud observation. In East China, this impact is much greater and special compared with other regions because of the frequent haze pollution. This study evaluated the impact of aerosols on cloud detection, cloud top height (CTH) and cloud optical thickness (COT) retrieval in East China primarily using the MODIS and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observation, combined with a cloud detection rectification algorithm. The results showed that, in haze weather, MODIS misjudged large-scale of dense aerosols as "clouds", which increased the observed cloud cover by 0.4 to 0.6 in the most seriously polluted regions. Compared with the clear condition, high aerosol loading with AOD >2 would increase the misjudgment possibility by 35%. Another influence is that MODIS has a 30% higher possibility to obtain an over low CTH of high and thin clouds, and overestimate the COT of thin ice clouds by 2.15 to 3.74 under serious air pollution. Further analyzes found that the cloud detection and COT retrieval was mainly influenced by the dense aerosols, while the CTH retrieval is vulnerable to both thin and dense aerosol. This study made a quantitative measurement of the aerosol influence on MODIS cloud observation, and first made a deep explanation for the effect of air pollution density.