Organizational Modes and Environmental Conditions of the Severe Convective Weathers Produced by the Mesoscale Convective Systems in South China

Composite radar reflectivity data during April-September 2011-2015 are used to investigate and classify storms in south China(18-27°N; 105-120°E). The storms appear most frequently in May. They are either linear; cellular or nonlinear systems, taking up 29.45%, 24.51% and 46.04%, respectively, in terms of morphology. Linear systems are subdivided into six morphologies: trailing stratiform precipitation（TS）, bow echoes（BE）, leading stratiform precipitation（LS）, embedded line（EL）, no stratiform precipitation（NS） and parallel stratiform precipitation（PS）. The TS and NS modes have the highest frequencies but there are only small samples of LS（0.61%） and PS（0.79%） modes.Severe convective wind(≥17m s-1at surface level) accounts for the highest percentage（35%） of severe convective weather events produced by cellular systems including individual cells（IC） and clusters of cells（CC）. Short-duration heavy rainfall(≥50 mm h-1) and severe convective wind are the most common severe weather associated with TS and BE modes. Comparison of environmental physical parameters shows that cellular convection systems tend to occur in the environment with favorable thermal condition, substantial unstable energy and low precipitable water from the surface to300 hPa（PWAT）. However, the environmental conditions favoring the initiation of linear systems feature strong vertical wind shear, high PWAT, and intense convective inhibition. The environmental parameters favoring the initiation of nonlinear systems are between those of the other two types of morphology.