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 variation of summertime precipitation over the Tibetan Plateau and its neighboring areas using the TMPA (TRMM Multi-satellite Precipitation Analysis) data during 2002-2006. The TMPA precipitation product is compared with rain gauge observations from 643 meteorological sites in China to confirm its applicability and fidelity. Both composite and harmonic analyses are applied to quantify the diurnal cycles of precipitation intensity and frequency. The harmonic amplitude indicates pronounced daily variability over the Tibetan Plateau and its nearby regions, with the strongest diurnal signal over the central Plateau and Indian Peninsula southwest of the Plateau. The harmonic phase displays that the timing of the maximum precipitation amount and frequency has considerably geographical dependence. Overall, a late-afternoon-evening maximum and a morning minimum are dominant in the central Plateau, whereas a late-night maximum is prevalent around the Plateau and in the 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 maximum away from the Plateau. The significant nocturnal rainfall in the Sichuan Basin is likely associated with eastward-propagating convective systems originated over the Tibetan Plateau.