Comparative Analysis on Cloud Evolution Features and Weather of Two MCCs
By using satellite images, weather radar data, combined with the environmental situation and physical characteristics, two mesoscale convective complex (MCC) events in northern Shandong and southern Hebei in 15-16 August 2011 (“0815MCC”), and central and southern regions of Shandong in 30-31 July 2015 (“0730MCC”) are analyzed. Comparisons show that (1) the distribution of heavy rainfall is asymmetric, mainly in the center of TBB and its west and south side. The precipitation is concentrated in the stage from formation to mature stage of MCC. The intensity and moving direction of surface mesoscale convergence system are closely related to the development of new cells. (2) The overlapping area of the high vorticity, divergence and vertical velocity is favorable for the development of MCC, which is the main factor for its movement toward southwest. (3) Radar VWP product shows that the establishment of the ultra-lower-level jet helps the happening of severe precipitation and maintenance of MCC. When the ultra-low-level jet velocity difference increases to a certain extent, the heavy rainfall begins. (4) The low-level convergence and high-level divergence of “0815 MCC” offer dynamic conditions, causing higher development, lower cloud top temperature, larger area of cold cloud than “0730 MCC”; meanwhile, the strong vertical wind shear brings the ice crystals to the thunder head, which may reduce the precipitation efficiency, so the 0815 MCC’s rainstorm range and maximum precipitation intensity are less than those of “0730 MCC”.