Impact of Urbanization on Low-Temperature Precipitation in Beijing during 19602008

Daily precipitation and temperature records at 13 stations for the period 19602008 were analyzed to identify climatic change and possible effects of urbanization on low-temperature precipitation LTP, precipitation of 0.1 mm d-1 occurring under a daily minimum temperature (Tmin) of 0C in the greater Beijing region (BJR), where a rapid process of urbanization has taken place over the last few decades. The paper provides a climatological overview of LTP in BJR. LTP contributes 61.7% to the total amount of precipitation in BJR in the cold season (November-March). There is a slight increasing trend 1.22 mm (10 yr) -1 in the amount of total precipitation for the cold season during 1960-2008. In contrast, the amount of LTP decreases by 0.6 mm (10 yr) -1. The warming rate of Tmin in BJR is 0.66C (10 yr) -1. Correspondingly, the frequency of LTP decreases with increasing Tmin by -0.67 times per C. The seasonal frequency and amount of LTP in southeast BJR (mostly urban sites) are 17%20% less than those in the northwestern (rural and montane sites). The intensity of LTP for the urban sites and northeastern BJR exhibited significant enhancing trends 0.18 and 0.15 mm d-1 (10 yr) -1, respectively. The frequency of slight LTP (0.2 mm d-1) significantly decreased throughout BJR by about15.74% (10 yr) -1 in the urban area and northeast BJR, while the contribution of the two heaviest LTP events to total LTP amount significantly increased by 3.2% (10 yr) -1.