Using radiosonde measurements from 26 July to 30 July 2014 at Baiqi over the Inner Mongolia grassland of China, the vertical structure of shallow cumulus （SCu） clouds and associated environmental conditions were inv...Using radiosonde measurements from 26 July to 30 July 2014 at Baiqi over the Inner Mongolia grassland of China, the vertical structure of shallow cumulus （SCu） clouds and associated environmental conditions were investigated. The cloud base height and the cloud top height of SCu was 3.4 km and 5 km, respectively. The temperature of the SCu layer was less than 0℃. The horizontal advection of specific humidity was smaller than the vertical transport in the atmosphere below 5 km. Above 5 km, the thermodynamic structure of the atmosphere remained stable. At the interface of the cloud layer and free air atmosphere, there was obvious wind shear and a temperature inversion （-2.9~C）. Comparisons of environmental parameters associated with cumulus congestus, rain and clear days, showed that the formation of SCu was characterized by a higher Bowen ratio （high sensible heat flux and low latent heat flux）, which indicated intensive turbulence in the boundary layer. The formation of SCu was associated with the boundary layer height exceeding the lifting condensation level. The maintenance of SCu was likely associated with the lower convective available potential energy, weak wind shear, and weak subsidence of the synoptic system, which did not favor the dramatic vertical development of SCu and thereby the transformation of SCu to cumulus congestus.展开更多
基金funded by National Science Foundation of China (Grant No. 40975001 and 61327810)the State Key Project of Research and Development Plan (Grant No. 2016YFC0200403)
文摘Using radiosonde measurements from 26 July to 30 July 2014 at Baiqi over the Inner Mongolia grassland of China, the vertical structure of shallow cumulus （SCu） clouds and associated environmental conditions were investigated. The cloud base height and the cloud top height of SCu was 3.4 km and 5 km, respectively. The temperature of the SCu layer was less than 0℃. The horizontal advection of specific humidity was smaller than the vertical transport in the atmosphere below 5 km. Above 5 km, the thermodynamic structure of the atmosphere remained stable. At the interface of the cloud layer and free air atmosphere, there was obvious wind shear and a temperature inversion （-2.9~C）. Comparisons of environmental parameters associated with cumulus congestus, rain and clear days, showed that the formation of SCu was characterized by a higher Bowen ratio （high sensible heat flux and low latent heat flux）, which indicated intensive turbulence in the boundary layer. The formation of SCu was associated with the boundary layer height exceeding the lifting condensation level. The maintenance of SCu was likely associated with the lower convective available potential energy, weak wind shear, and weak subsidence of the synoptic system, which did not favor the dramatic vertical development of SCu and thereby the transformation of SCu to cumulus congestus.
基金supported by the USTC Research Funds of the Double First-Class Initiative(YD3420002004)the National Natural Science Foundation of China(42125402,41974174,42188101,41831071,42174183,and 41904135)+4 种基金the B-type Strategic Priority Program of CAS(XDB41000000)the Project of Stable Support for Youth Team in Basic Research Field,CAS(YSBR-018)the Fundamental Research Funds for the Central Universitiesthe Anhui Provincial Natural Science Foundation(2008085MD113)the Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO202209).
