Diurnal variation of summer rainfall over the Tibetan Plateau and its neighboring regions revealed by TRMM multi-satellite precipitation analysis

This paper investigates the diurnal variations of summertime precipitation over the Tibetan Plateau and its neighboring regions using the TRMM Multi-satellite Precipitation Analysis (TMPA) product during 2002-2006. We first compare the TMPA data with rain-gauge observations to demonstrate their applicability and fidelity. Both diurnal composite and harmonic analyses are employed to examine the diurnal cycles of precipitation intensity and frequency. Results show remarkable daily variability in summer precipitation over the Tibetan Plateau and nearby areas. The strongest diurnal oscillation occurs in the central Plateau, and other significant diurnal signal is present in the Indian Peninsula, to southwest of the Plateau. The occurrence of the maximum/minimum rainfall intensity and frequency has salient geographical dependence. On the whole, a late-afternoon-evening maximum is dominant in the central Plateau, whereas a late-night maximum is prevalent around the Plateau periphery and in Sichuan Basin, and a morning and afternoon maximum appear in the upper and mid-lower reaches of the Yangtze River, respectively. There is a coherent diurnal variation pattern east of the Plateau, characterized by systematically delayed precipitation away from the Plateau. The significant nocturnal rainfall in Sichuan Basin is likely associated with eastward-propagating convective systems originated over the Tibetan Plateau.