Impact of urbanization on low-temperature precipitation in Beijing during 1960-2008

Daily precipitation and temperature records at 13 stations for the period 1960-2008 were analyzed to identify climatic change and possible effects of urbanization on low-temperature precipitation [LTP, precipitation of a (c) 3/4 0.1 mm d(-1) occurring under a daily minimum temperature (Tmin) of a (c) 1/2 0A degrees C] 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 0.66A degrees C (10 yr)(-1). Correspondingly, the frequency of LTP decreases with increasing Tmin by -0.67 times per A degrees 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 about (-1)5.74% (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).