It shows that when %A% is more than 2.1, a stable vortex formed within the urban street canyon become two vortexes.

• 各类型街谷内污染物扩散水平从强到弱依次为迎风面建筑物高度大于背风面建筑物高度的街道峡谷,迎风面建筑物高度小于背风面建筑物高度的街道峡谷;