Characteristics Of Cloud Radiative Effects And TOA Energy Budget In The South China Sea And South China Before And After The Onset Of South China Sea Summer Monsoon

Clouds and top-of-atmospheric?TOA?radiation budget are strongly influenced by abrupt circulation variations.This study uses satellite and ERA-Interim reanalysis data to investigate characteristics of TOA cloud radiative effects and radiation budget over South China?SC?with the South China Sea monsoon?SCSM?onset.Before the SCSM onset,the descending motion prevails over the South China Sea?SCS?and the shortwave radiative effect?SWCRE?dominates cloud radiative effects over SC.After the SCSM onset,the low-level southwesterly wind,ascending motion and high clouds abruptly occur over SCS,causing an increase in the strong convection and warming longwave cloud radiative effect,which partially offsets the cooling effect of the SWCRE.Consequently,the net cloud radiative effect and TOA upward shortwave radiation weaken,but the TOA radiation budget increases over southern SC and most of SCS.Meanwhile,low-middle clouds and large SWCRE still stay over northern SC and the middle and lower reaches of the Yangtze River,where the TOA radiation budget is weaker than before the SCSM onset.Due to these rapid subseasonal variations of circulation conditions and cloud radiative effects after the SCSM onset,the differences in the whole atmospheric heat source and TOA radiation budget increase separately by 78.9 W m^-2and 17.2 W m^-2averaged over northern SCS and southern SC,and the counterparts are 5.1 W m^-2and-3.7 W m^-2over northern SC and the middle and lower reaches of the Yangtze River.These abrupt cloud-radiation changes caused by the SCSM onset lead to a TOA energy gradient,with a value of 20.8 W m^-2,from northern SCS and southern SC to their northern regions,which is likely as a manifestation for the summer monsoon precipitation belt advancing northward over eastern China.Before and after the onset of the SCSM,the changes of the circulation,cloud radiation effect and TOA energy budget in the earlier and later years are consistent with the climate conditions,but the intensity varies.The NCRE in the earlier years of SC is weaker than that in the later years,so the TOA energy budget in the earlier years is larger than that in the later years.In the later years,the SCS region is greatly affected by the solar short-wave radiation effect and sea temperature,resulting in a difference in the energy budget of the atmosphere between the two places in the later years than in the earlier years.Consistent with the largest difference in NCRE between the two places,the largest difference in TOA energy difference is 74.60 W m^-2(85.07 W m^-2)at the 25?29?pentad in the earlier?later?years.