Abstract: In this paper,the net radiation heating(QRT)at top of the atmosphere(TOA), i.e. the net thermal forcing on the upper boundary of the earth atmosphere system,are derived from the satellite observed outgoing long wave radiation(OLR)and the TOA short wave net irradiance(SHT).Analyses focus on the climatic feature of the seasonal cycle of the QRT and its relationship with the Asian summer monsoon(ASM). Results show that the evolution of the QRTD(deviation of the QRT from latitudinal mean),which is controlled by the land/sea contrast,experiences rapid seasonal reversals between continents and oceans.From spring to summer,the reversal leads one month to the abrupt change in the atmospheric circulation,which may play a key role in the onset of the ASM.