In this paper,the continuity and thermodynamic equations including moisture forcings were derived.Using these two equations and the basic momentum equation of local Cartesian coordinates,the budget equation of generalized moist potential vorticity(GMPV) was derived.The GMPV equation is a good generalization of the Ertel potential vorticity(PV) and moist potential vorticity(MPV) equations.The GMPV equation is conserved under adiabatic,frictionless,barotropic,or saturated atmospheric conditions,and it is closely associated with the horizontal frontogenesis and stability of the real atmosphere.A real case study indicates that term diabatic heating could be a useful diagnostic tool for heavy rainfall events.
Using data collected at 517 weather stations in contiguous China over the period 1980-2008,characteristics of thunder events have been investigated.These characteristics include geographical distribution,interdecadal variation,annual variation,and seasonal variation.The areas with the highest frequencies of thunder events are located in the central Tibetan Plateau,Yunnan,Guangxi,and Guangdong.The annual number of thunder days increases from northern to southern China.But the frequency of thunder events over mountains and plateaus is much higher than the frequency of events over plains in the same latitude.The interdecadal variation of events shows that the frequency of thunder occurrences was highest during the 1980s,decreased during the 1990s,and increased slightly afterwards.Thunder occurrences vary with the season,northward in May and retreating southward in September.
