Large-scale wind fields always are a result of large convergence or divergence hybridized with cold or warm advection,so four sorts of mixed wind fields are abstracted:(1) warm advection combined with large scale convergence;(2) cold,with convergence;(3)warm,with divergence;(4)cold,with divergence.Different fields lead to unlike zero velocity lines characteristics,which have indicated effect to estimate divergence of large-scale wind fields.By means of the curve degree and the inter-angle between zero points in a distance ring and radar center,a quantificational arithmetic to calculate air divergence is deduced by mathematics approach at firstly,and then a method of one by one adjustment is introduced to identity zero velocity points.United with zero identified,a principle of pattern recognition and its approach are documented,whereby,air average divergences can be extracted from Doppler radar base data,the divergences of different levels are quantificationally received,and furthermore,an idea of divergence plan position indicator(div PPI) is advanced.On basis of two cases,the effect of picture identification is analyzed by contrasting div PPI with velocity PPI,divergences extracted by identification are compared with EVAD.