Abstract
Based on the hourly gauge-satellite merged precipitation product with the horizontal resolution of 0.1° latitude/longitude during 2008–2014, diurnal variations of the summer precipitation amount (PA), frequency (PF), and intensity (PI) with different duration time over the regions east to Tibetan Plateau have been systematically revealed in this study. Results indicate that the eight typical precipitation diurnal patterns identified by the cluster analysis display pronounced regional features among the plateaus, basins, plains, hilly and coastal areas. The precipitation diurnal cycles are significantly affected by the sub-grid terrain fluctuations. The PA, PF and PI of the total rainfall show much more pronounced double diurnal peaks with the sub-grid topography standard deviation (SD) decreased. Meanwhile, the diurnal peaks of PA and PF (PI) strengthen (weaken) with the sub-grid topography SD enhanced. Over the elevated mountain ranges, southeastern hilly and coastal regions, the PA and PF diurnal patterns of the total rainfall generally show predominant late-afternoon peaks, which are closely associated with the short-duration (leqslant , 3 h) rainfall. Along the Tibetan Plateau to its downstream, the diurnal peaks of PA, PF and PI for the total rainfall all exhibit obvious eastward phase time delay mainly due to the diurnal evolutions of long-duration (> 6 h) rainfall. However, the 4–6 h rainfall leads to the eastward phase time delay of the total rainfall along the Taihang Mountains to its downstream. Further mechanism analysis suggests that the midnight to morning diurnal evolution of the long-duration rainfall is closely associated with the diurnal variations of the upward branches of thermally driven mountain-plain solenoids and the water vapor transport associated with the accelerated nocturnal southwesterly winds. The late-afternoon peak of the short-duration PA over the southeastern hilly and coastal regions is ascribed to the strong local thermal convections due to the solar heating in afternoon, while the early-evening peak of the short-duration PA over the elevated mountain ranges is significantly contributed by the upward warm-moist wind from the surrounding low-lying basins or plains.
Highlights
IntroductionAs a response to the evolution of synoptic and climatic systems and local forcing, is an important aspect of the local climate and takes a significant feedback on certain thermal and dynamical conditions (Sorooshain et al 2002)
Diurnal variation of precipitation, as a response to the evolution of synoptic and climatic systems and local forcing, is an important aspect of the local climate and takes a significant feedback on certain thermal and dynamical conditions (Sorooshain et al 2002)
Over the southeastern hilly and coastal regions, the precipitation amount (PA) and PF of the total rainfall show coherent late-afternoon peaks (Fig. 2a, d), while they usually occur during midnight to early morning over the eastern peripheries of Tibetan Plateau to Sichuan Basin and some sub-regions in the North China Plain
Summary
As a response to the evolution of synoptic and climatic systems and local forcing, is an important aspect of the local climate and takes a significant feedback on certain thermal and dynamical conditions (Sorooshain et al 2002). Short-duration rainfall peaks in the late afternoon, which is closely related to the thermally driven convection induced by surface solar heating (Dai et al 1999; Yuan et al 2012), while long-duration rainfall usually peaks during the period from midnight to early morning This may be explained by the interactions between the local atmospheric conditions and the large-scale background circulations (Zhuo et al 2014; Yin et al 2009), e.g. nocturnal radiative cooling at cloud top (Lin et al 2000; Li et al 2004, 2008), the evolution of mesoscale convective systems (Carbone et al 2002; Nesbitt and Zipser 2003; Jiang et al 2006), and the largescale monsoon circulations (Chen et al 2009b, 2010; Yuan et al 2010). This close diurnal-scale correlation between precipitation and wind fields was further validated by Chen et al (2012a, b) and Yuan et al (2014a)
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