Precipitation characteristics in large cities and their suburbs under different terrains in 30°N zone of China in recent 49 years

Based on daily precipitation data from 1969 to 2017, topographical data and residential population data in 2017, by using a num-ber of statistical analysis methods such as probability density function (PDF) method, least square method, Mann-Kendall method and cumu-lative anomaly method, the precipitation characteristics in large cities and their suburbs under different terrains in 30°N latitude zone of Chi-na in recent 49 years are analyzed from the PDF characteristics, the trend of precipitation and the characteristics of extreme precipitation combining with the terrain diversity of China. The results show that:(1) The precipitation of 30°N latitude zone of China has obvious regional and extreme characteristics. The annual precipitation PDFs at the Yangtze River estuary stations are the closest to normal distribution. The extreme precipitation threshold and extreme precipitation intensity generally increase from west to east and are inversely related to the ter-rain height. For extreme precipitation in rainstorm and above, the probability of precipitation is low while the precipitation proportion is high. (2) The urbanization effect of precipitation is obvious, as represented by the facts that the PDFs of the daily, monthly, seasonal and annual precipitation at the representative stations generally have urban and suburban differences, and the difference at daily or annual scales is more obvious than that at monthly or seasonal scales. Annual precipitation at representative stations in large cities generally increases faster than that in their suburbs, and the minimum value is greater. Extreme precipitation threshold, extreme precipitation intensity and the maxi-mum value of annual maximum daily precipitation are generally larger, and the probability and the proportion of moderate and above-class heavy rain of the former is larger than the latter. (3) Precipitation has obvious interannual and seasonal variations, and has certain weekly variation. The annual precipitation mutations occur concentrated in the mid-late 1980s, the 1990s and the beginning of 2000s. The seasonal variation characteristics of precipitation is the most in summer and the least in winter. The urbanization effect of summer precipitation is obvi-ous under the terrains of Jianghan Plain, the middle and lower reaches of the Yangtze River and the Yangtze River estuary. The urbanization effect of precipitation in working days is more obvious than the rest days under most terrains.