Diurnal Cycle of Convective Features over Pearl River Delta during Mei-Yu season Observed by Ground-based Radar

Using the operational Doppler radar data during 2007-2009, the Mei-Yu convective diurnal cycle and propagation in Pearl River Delta are investigated in this study. Results show that convection occurs most frequently along the southern coast and on the windward slope of the northeastern mountain area. Convection in both frequency centers exhibit bimodal diurnal cycle feature. The afternoon frequency peaks are obviously due to the solar heating effect and the early morning peaks are closely related to the nocturnal acceleration of boundary layer southwesterly flow and land-breeze. The convection occurred on the windward slope of the northeastern mountainous area is locally while convection initiated along coastline can propagate to inland area from early morning to early afternoon. Low-level jet (LLJ) can also influence convective diurnal cycle. A robust change of convective diurnal cycle and propagation can be found between LLJ and no-LLJ days.