Intensive Radiosonde Measurements of Summertime Shallow Cumulus over the Inner Mongolia Grassland (IMG) in 2014

The vertical structure and environmental conditions associated with the occurrence of shallow cumulus (SCu) clouds were investigated in this study using radiosonde measurements collected during an intensive experiment from 26 July to 30 July 2014 at BaiQi (BQ) over the Inner Mongolia Grassland (IMG) of China. The results showed that the cloud base height (CBH) of SCu was greater than 3 km because of the low moisture content and high Bowen ratio at this location. The formation of SCu clouds was mainly attributed to the vertical transport of the moisture, heat and momentum fluxes from the surface. The horizontal advection was very weak. The low Bowen ratios and high soil moisture content were unfavorable for SCu formation. Compared with weather conditions associated with cumulus congestus and rain, the formation and maintenance of SCu clouds was favored by the lower convective available potential energy (CAPE), which prevented the dramatic vertical development of SCu. SCu clouds form if the top of boundary layer height (BLH) exceeds the lifting condensation level (LCL). Strong wind shear generally resulted in cumulonimbus (Cb) clouds and precipitation. The weak subsidence of air flow was favorable for the maintenance of SCu, which prevented the transformation of SCu to Cb.

The vertical structure and environmental conditions associated with the occurrence of shallow cumulus (SCu) clouds were investigated in this study using radiosonde measurements collected during an intensive experiment from 26 July to 30 July 2014 at BaiQi (BQ) over the Inner Mongolia Grassland (IMG) of China. The results showed that the cloud base height (CBH) of SCu was greater than 3 km because of the low moisture content and high Bowen ratio at this location. The formation of SCu clouds was mainly attributed to the vertical transport of the moisture, heat and momentum fluxes from the surface. The horizontal advection was very weak. The low Bowen ratios and high soil moisture content were unfavorable for SCu formation. Compared with weather conditions associated with cumulus congestus and rain, the formation and maintenance of SCu clouds was favored by the lower convective available potential energy (CAPE), which prevented the dramatic vertical development of SCu. SCu clouds form if the top of boundary layer height (BLH) exceeds the lifting condensation level (LCL). Strong wind shear generally resulted in cumulonimbus (Cb) clouds and precipitation. The weak subsidence of air flow was favorable for the maintenance of SCu, which prevented the transformation of SCu to Cb.