资源环境科技发展态势分析平台

This study examines the relationships between marine stratocumulus clouds (MSC) coupling state with the ocean surface, their precipitation rate and fractional cloud cover (CF). This was possible by developing a novel methodology for satellite retrieval of the clouds coupling state. Decks of overcast MSC were reported in previous studies to break up often as their precipitation rate increases significantly, thus reducing CF and cloud radiative effect substantially. Here we show that decks of precipitating decoupled MSC have larger CF compared to similarly precipitating coupled MSC. The difference in CF between decoupled and coupled clouds was found to increase with precipitation rate, up to nearly doubling the CF of the heaviest precipitating decoupled MSC. This suggests that decoupling is a feature related to higher cloud radiative effect in precipitating MSC.

Plain Language Summary Marine stratocumulus are oceanic clouds that are often observed to exist in two main cloud regimes that differ by their cloud cover. The large cloud cover regime reflects back to space a significant amount of solar energy, in comparison to the low cloud cover regime. Past studies have shown that these cloud cover regimes are related to precipitation rate, so that heavily precipitating clouds often have lower cloud cover than lightly precipitating clouds. In this study we present a novel satellite-based methodology for retrieving the coupling degree (a measure of the interaction between the cloud layer and the ocean's surface) of marine stratocumulus clouds. Such retrievals extend the physical understanding that can be inferred from satellites. We found that heavy precipitation coexists with large cloud cover more often in clouds that are not coupled to the ocean surface. This adds another dimension to the relationship between precipitation rate and cloud cover, and the subsequent effect on the Earth's climate.