Inconsistent urbanization effects on summer precipitation over the typical climate regions in central and eastern China

Abstract

Using a 30-year data (1983–2012) from 428 stations, we study summer precipitation differences between urban and rural areas in 5 Chinese climate regions: the Pearl River Delta (PRD), the Middle and Upper reaches of the Yangtze River (MUYR), the Yangtze River Delta (YRD), the North China Plain (NCP), and Northeast China (NEC). By analyzing heavy rain (HR) (24-h precipitation ≥ 100 mm) and light rain (LR) (0.1 mm ≤ 24 h precipitation ≤ 25 mm), we find that urbanization has had inconsistent effects on precipitation. Higher HR occurs over urban areas of the PRD and YRD than rural areas, and lower HR occurs over urban areas of the MUYR, NCP and NEC than rural areas. The urban LR is less than the rural LR in all climate regions. The correlation between precipitation and the convective available potential energy (CAPE) or humidity explains the regional differences in urbanization effects on HR. HR is greatly affected by the CAPE in the PRD and YRD, where the CAPE is high (> 600 J/kg at 14:00 LT), water vapor is abundant (> 45 kg/m2 at 14:00 LT), and the urban heat island increases the urban HR. However, HR is greatly affected by humidity in the MUYR, NCP, and NEC, where the CAPE and water vapor are less (≤ 500 J/kg and ≤ 40 kg/m2 at 14:00 LT) and the urban HR is mainly suppressed by the urban dry island. Our results indicate that urbanization promotes HR in wet climates but suppresses HR in dry climates during summer in central and eastern China.