Contrasting effects of land and marine aerosols on warm clouds in South China based on satellite observations

Different aerosol types influence cloud properties in distinct ways due to their unique physical and chemical characteristics. While many studies have examined aerosol–cloud interactions, comparative analysis of how specific aerosol types affect warm clouds over land and ocean remain limited. Using MODIS cloud products and MERRA-2 aerosol data from 2014, this study reveals that warm clouds over the ocean exhibit greater sensitivity to increases in aerosol optical depth (AOD) compared to those over land. Specifically, with increasing total AOD, cloud fraction (CF) increases at a rate 3 times greater, while cloud top temperature (CTT) and cloud droplet effective radius (CER) decrease 2.5 and 6.5 times faster, respectively. Liquid water path (LWP) shows contrasting trends: over land, it initially increases and then decreases with rising AOD, whereas over the ocean, it shows a consistent negative correlation with AOD. Under fixed LWP, CF over land is more sensitive to AOD under low LWP conditions, while oceanic CF responds more strongly under high LWP. Under the influence of dust aerosols over land, cloud properties initially change significantly and then tend to stabilize. Over the ocean, particularly under high LWP conditions, cloud properties exhibit a stronger response to sea salt aerosols. Fine aerosols show similar effects to total aerosols in both land and ocean environments. These findings highlight the necessity of distinguishing different aerosol types, which contributes to a better understanding of the aerosol-cloud interactions.