Diurnal variations of summertime precipitation over the Tibetan Plateau and their relationship with orographically-induced atmospheric circulations

Both hourly precipitation amount and precipitation frequency exhibit pronounced daily variability with an overall late-afternoon-evening maximum and a dominant morning minimum. A notable exception is the prevalent nocturnal maximum around the periphery of the Plateau.

In terms of the normalized harmonic amplitude, the diurnal signal shows significant regional contrast with the strongest manifestation over the central Plateau and the weakest near the periphery. This remarkable spatial dependence in daily rainfall cycles is clear evidence of orographic and heterogeneous land-surface impacts on convective development. Using six-hourly NCEP FNL data, we then examined the diurnal variability in the atmospheric circulation and thermodynamics in this region.