Spatial features of rain frequency change induced by pollution and associated aerosols

Abstract. A spatial-temporal analysis has been conducted using satellite observed distributions of rain frequency, NO₂ concentration and aerosol, with focus on the spring season. As revealed by measurements from 1998–2009 over Shanghai, China, the suppression of rain is mainly attributed to the reduction of rain occurrence rather than changes in rain intensity. The overall features emerge from the region-by-region analyses that there is an inverse relationship between the rain frequency and the pollution and associated aerosols at continental scale in spring. The enhancement of pollution-produced CCN in addition to mineral dust from long-term transport suppresses the rain frequency, as favored by topography, wind, and other meteorological conditions.