Effect of Sensible Heat on Convective Activities in North China and Its Surrounding Areas

This paper represents statistical analysis of the convective activities and surface sensible heat fluxes from May to August in North China and its surrounding areas based on meteorological satellite and reanalysis data from 2006 to 2017. The results show that the daytime average sensible heat flux is closely related to the topography in North China and its surrounding areas. The sensible heat flux is stronger in the central and southeastern Inner Mongolia and the northern and the western mountainous areas of North China. The strongest sensible heat flux occurs in May and June whereas it obviously weakens in July and August. The higher convection frequency corresponding to the intensity of the sensible heat flux also occurs in May and June. In May, most of the convections are weak. The deep convections are most active in the north-central part of North China in June and are relatively frequent in the area around the Bohai Sea from June to July. The trend of the corresponding relationship between the daily average sensible heat flux and convection frequency shows consistent weakening from May to August. In the morning, sensible heat causes various degrees of convergence and warming in the lower troposphere below 700 hPa in the Western and Northern Hebei Province. The ascending motion reaches the middle troposphere, and the compensating descending motions occur in the eastern plains. The warming up and ascending motion trigger convection, which can develop rapidly when it moves eastward under favorable conditions. The diurnal variation in convection frequencies in different months and regions obviously differs. In June, the diurnal variation in the convection frequencies is significant, whereas it is the weakest in August. Regionally, the diurnal variation in the convection frequencies in mountainous areas is significant, whereas it is the weakest in the eastern Bohai Sea and its surrounding areas. Both the monthly mean distribution and diurnal variation in the convection frequency have a close relationship with the surface sensible heat flux generated by the topography.