Seasonal and interannual characteristics of atmospheric cloud radiative effect over South China and neighbouring ocean regions

Atmospheric cloud radiative effect (ACRE) is a critical heat source in the atmosphere, with pronounced regional distributions. Here, we investigate seasonal and interannual characteristics of ACRE over South China (SC) and neighbouring ocean regions using 2001-2020 satellite and reanalysis data. Annual mean net ACRE shows a warming role over most of SC, its eastern ocean (ESCO), and the South China Sea and western North Pacific (SWNP), with domain-mean values of 6.0, 14.9, and 32.8 W m(-2), respectively. Over SC, the shortwave ACRE warming dominates annual mean net ACRE, and considerable low-middle clouds with small particle size and large water content reflect shortwave radiation and enhance shortwave absorption, especially in spring. Notably, winter longwave ACRE over SC, with a cooling role, strongly offsets its summer counterpart's warming role. In contrast, longwave ACRE mainly accounts for net ACRE over ESCO and SWNP, especially the latter where high clouds prevail. The Asian summer monsoon enhances summer high clouds and longwave (net) ACRE. Cloud types and complex vertical distribution associated with continental environments and the Tibetan Plateau's topography forcing enable seasonal behaviours of ACRE over SC to be different from the other two regions. Longwave ACRE dominates the interannual variation of net ACRE, with a larger interannual variability over SWNP, while a larger annual variability of shortwave ACRE occurs over SC. There are no significant interannual trends of ACRE except for annual and spring mean longwave (net) ACRE over SC. Moreover, the interannual variation of longwave (net) ACRE relates well to 500-hPa vertical velocity, indicating the strong influence of large-scale circulation on regional ACRE.