城市化对石家庄站日气温变化的影响

Urbanization effect on change of daily temperature at Shijiazhuang weather station

利用1962—2011年逐日平均、最低和最高气温资料,对比分析了石家庄站和藁城站平均、最低和最高气温的概率分布特征.石家庄站是我国少有的自建站以来从未迁址的城市气象站,而附近的藁城站可近似看作乡村气象站.结果表明:城市化致使石家庄站1962—2011年平均、最低和最高气温的概率密度分布向高温方向偏移,其中对最低气温分布的影响尤其明显,对最高气温分布的影响很小;受城市化影响,石家庄站最低气温概率密度分布的高温部分增温比低温部分增温更加明显,最低气温分布形状更加扁平;相对于1962—1986年,1987—2011年石家庄站平均、最低和最高气温概率密度分布均向高温方向偏移,其中最低气温偏移最为明显,并导致1962—2011年整个分析时期最低气温分布出现非正态性;城市化对石家庄站气温分布的影响在冬、春季比夏、秋季更显著,最显著的城市化影响出现在冬季最低气温上;石家庄站基于最低气温的极端气温指数趋势受城市化影响严重,冷夜日数和暖夜日数的城市化影响分别为-1.13d/10a、1.48d/10a,但基于最高气温的冷昼和暖昼日数等极端气温指数变化趋势受城市化影响不明显.出现这种现象的主要原因是城市化对最低、最高气温分布的影响存在差异.

With rapid growth of economy and expansion of cities,urbanization has become a significant factor in affecting the long-term changes of mean and extreme temperature and other key climatic variablesat most urban stations of China's Mainland.So far,this problem has aroused more and more attentions in urbanization effect on mean temperature trends,but the few analysis of urbanization effect on temperature probability density distribution has been done.This article analyzes the urbanization effect on daily temperature probability density distribution（PDF）,daily temperature cumulative probability density distribution（CDF）and the seasonal cycles of daily mean temperature for Shijiazhuang weather station without any relocation before 2011 as an example. This paper uses daily data of Tmean,Tminand Tmaxof an urban weather station,Shijiazhuang station,and a nearby rural weather station,Gaocheng station,from 1962 to 2011.Shijiazhuang station was never moved before 2011.Urbanization effect（ΔTur）is defined as the temperature trends or change in daily temperature PDF and CDF of urban station caused by the changing Urban Heat Island（UHI）intensity and/or the effect of other factors（such as aerosols）. The urbanization makes the distribution of annual Tmean,Tminand Tmaxat Shijiazhuang station during 1962—2011shift to high temperature side.Urbanization effect on the distribution of annual Tminis very obvious,but the effect on the distribution of annual Tmaxis small.Due to the urbanization effect,the increase in Tminis larger on high value side than on low value side at Shijiazhuang station,resulting in a flatter shape of annual TminPDF than that of the rural station;The PDF of Tmean,Tminand Tmaxat Shijiazhuang station all shifts to the higher value side during1987—2011compared to 1962—1986,with the largest shift occurring in Tmin.The PDF of Tminat Shijiazhuang station in the time period 1962—2011is characterized by a non-normal distribution due to the urbanization effect.The difference of PDF between Shijiazhuang station and Gaocheng station during 1962—2011is larger and more significant in winter and spring than in summer and autumn,and the largest difference is found for winter Tmin.The urbanization effect in the 1962—2011series of cold nights and warm nights are respectively-1.13d/10 aand 1.48d/10 a,and the urbanization contribution are respectively 28.32% and 37.76%.The urbanization effects in the Tmin-based extreme temperature indicesare larger for those in the Tmax-based extreme temperature indices at Shijiazhuang station.In each of the seasons of a year,the daily mean Tmindifference between the urban and rural stations is generally more than 1.0 ℃,with the daily urban heat island intensity,sometimes reaching above 1.5 ℃,being the largest from the beginning of December to the end of May,and the daily mean Tmax difference between the urban and rural stations is usually less than 0.5 ℃. The significant urbanization effect on urban station surface air temperature records exists not merely in the linear trends of mean temperature series and extreme temperature indices series,but also in the probability density distribution of daily Tminand Tmean.It is an important factor in forming the asymmetry changes of diurnal and seasonal temperature cycles for Shijiazhuang station.