Diurnal evolution and distribution of warm-season convective storms in different prevailing wind regimes over contiguous North China

The diurnal evolution and distribution of warm-season convective storms in different prevailing wind regimes at the 925 hPa and 500 hPa levels over contiguous North China have been studied using a climatology based on radar reflectivity mosaics, soundings, and reanalysis data from 15 May to 15 September, in 2008-2011. In the wind regimes at the 925 hPa level, the frequency of occurrence of convection is highest for south-southwesterly flows, followed by that for south-southeasterly flows. The low-level southerly warm and moist flow over the foothills and plains favors initiation and intensification of convection resulting from topographic forcing. Among the wind regimes at the 500 hPa level, the frequency of occurrence of convection shows a pronounced maximum for west-southwesterly flows, and most of these storms initiate and develop over the foothills and plains. Convection in the wind regime shows the morphology and slowly east-southeastward moving characteristics of well-organized, longer-lived systems, with environmental conditions conducive to vertical wind shear and instability. At the 500 hPa level, the high frequency of occurrence of convection for west-southwesterly flows is followed by that for west-northwesterly flows. Under west-northwesterly flows, convective storms initiated over mountains located to the northwest in the early afternoon move rapidly to the plains in the southeast of the study region. These storms show the primary formation characteristics of shorter-lived convection and intensify noticeably as they move from the mountains to the foothills and plains.