## Left Skew L Probability Distribution Function (LS-LPDF) and a New Meteorological Drought Index 左偏型L概率分布函数与一种新的气象干旱指数

Unique standard random variable, t=(x- xL )/ x or t=(x- xA )/ x , for left skew L probability distribution function(LS-LPDF), is totally decided by the boundary condition of standard L probability distribution function, f(+1) being equal to zero, or f(+1)=0 , on which left skew property of LS-LPDF entirely and completely is dependent, the meticulous and detailed variation and information in “dry area” is as fully and comprehensively delineated as possible using left skew characteristics of LS-LPDF , because x is real variable , xA or xL is averaged value of real variable in a temporal and spatial context, x is changes to +**∞** from 0,(x- xL )/ x or (x- xA )/ x is equal to-**∞ **when x is zero, however, (x- xL )/ x or (x- xA )/ x is equal to +1 ** **when x is +**∞ **.finally, theoretical 12-levels of meteorological drought index is deduced.