Using nine years of Tropical Rainfall Measuring Mission (TRMM) 2A25 data, based on the probability density function of rainfall, a comparative analysis of the diurnal cycle and its seasonal and interannual variation for convective rain, stratiform rain, and total rain is made between the Tibetan Plateau and the downstream Yangtze River basin and East China Sea. The diurnal convective rain is stronger than the diurnal stratiform rain over the Yangtze River basin, and the convective rain peaks in the afternoon when the stratiform rain maximum happens in the early morning. Convective rain and stratiform rain both peak in the early morning over the East China Sea. The diurnal total rain over the Tibetan Plateau is stronger than its downstream regions. The diurnal cycle appears quite different among the four seasons over the Yangtze River basin, and the seasonal variation of diurnal convective rain is more apparent than diurnal stratiform rain. The seasonal variation of the diurnal cycle is weak over the East China Sea and Tibetan Plateau. The maximum of total rain happens in the afternoon during 1998–2002 over the Yangtze River basin, while it peaks in the early morning during 2003–2006, but no obvious phase differences can be found among years in the diurnal rain over the East China Sea and over the Tibetan Plateau.
本文利用9年的TRMM卫星降水资料，对青藏高原及其下游地区对流降水、层云降水和总降水日变化的季节变化和年际变化进行了对比分析，结果表明：长江流域降水日变化的季节变化非常明显，且对流降水日变化的季节变化比层云降水强。青藏高原和东海地区降水日变化的季节变化比较弱。长江流域降水日变化在2002年前后发生明显变化，之前降水最大值出现在午后，之后则出现在凌晨，而青藏高原和东海地区降水日变化的相位没有明显变化。