Urbanization reduces frequency of light rain: an example from Beijing City

摘要

An hour precipitation dataset of 42 automatic weather stations is developed and applied to analyze the temporal and spatial characteristics of light precipitation in urban areas of Beijing City during 2007-2017. The stations are classified into three groups, including 18 sites in central urban area (4th Ring-Road, RR), 10 sites in peri-urban area (4th-5th RR), and 14 sites in suburban area (5th-6th RR). Light precipitation is defined as hourly rainfall of 0.1-0.3 mm. Analysis shows that light precipitation occurred in urban area the whole day, with the peak value in 0600 LST and minimum value in 1600 LST; monthly variation of light precipitation frequency (LPF) was characterized by the highest value in summer and the lowest value in winter; remarkable differences are found for the various urbanized areas, with the annual and seasonal mean LPF being generally small in central urban area and gradually increasing toward suburban area; the hourly mean LPFs during morning and nighttime are higher in summer than those in other seasons in each of the urban areas; relative humidity, aerosol, and wind speed might have been the major influential factors for the observed temporal and spatial pattern of light precipitation.