西安城市地温与气温变化初步分析

地下浅层地温和近地表空气温度存在着必然的内在联系，地面温度变化的信息随着时间推移向下传播并叠加到稳态地温场上，因此通过对现今地温剖面的分析可以重建过去地面温度变化的历史。为了研究西安地区地下和地上的温度变化，本文在西安开展了钻孔温度测量，获得了16个钻孔的地温剖面，同时收集整理了西安气象站1951～2010年气温数据。对1951～2010年气温数据进行回归分析得到西安地区年平均气温、年平均最高气温和最低气温增温率分别为3.71 ℃/100a、2.03 ℃/100a和5.14 ℃/100a，均高于全国和全球平均水平，其中1986～2010年间平均气温增温更是显著，达到9.01 ℃/100a。从钻孔测温曲线中筛选出西安城郊6个传导型地温剖面进行分析，结果表明西安地区钻孔温度记录的地面温度变化趋势与气象台记录的气温变化趋势基本吻合。根据利用钻孔温度剖面下段回归分析得到的地表稳态温度和地温梯度以及25年间西安地区平均气温增温率推算得到钻孔理论地温剖面与实测地温数据总体上具有较好的一致性。对实测地温数据的进一步精确拟合分析显示，西安城郊6个选定的钻孔所在区域地面温度变暖分别起始于20年、24年、26年、28年、30年和30年前，对应的地表增温幅度分别为0.4 ℃、0.72 ℃、2.18 ℃、4.2 ℃、2.4 ℃和2.4 ℃。市区和周边郊区钻孔所在区域在增温幅度上存在明显的差异，市区增温强度明显高于郊区，而城郊结合部介于两者之间。

Preliminary analysis of the subsurface temperature and air temperature changes in Xi’an,China

It has been well recognized in the earth science community that subsurface ground temperatures and surface air temperatures are related. A present-day subsurface temperature versus depth profile can be used for a reconstruction of a climate history,because the effect of air temperature fluctuations will propagate downward into the earth. In this paper,instrumental records from the Xi'an Meteorological Station from 1951 and subsurface temperature measurements from 16 boreholes are analyzed for an understanding of thermal environmental changes across the ground surface in Xi'an,Shaanxi Province,central China. Linear-regression analysis of meteorological data from 1951 to 2010 shows warming trends of 3.71℃/100a in the annual mean,2.03 ℃/100a in the annual maximum,and 5.14 ℃/100a in the annual minimum air temperatures,all substantially greater than the national and global rates. The warming trend in the annual mean surface air temperature (SAT) was even more stronger,at 9.01 ℃/100a,for the 25-year period from 1986 to 2010 in Xi'an. This warming trend is well preserved in the subsurface temperature records. Six conductive temperature profiles located in both ruraland urban areas were selected for the derivation of the geothermal gradient,the steady state ground surface temperature(GST),and the reduced transient temperatures. Synthetic borehole temperature profiles based on the inferred steady state components and the 25-year SAT warming trend are in general consistent with the observed temperature profiles. A refined analysis of the borehole temperature data further suggests that the onsets and the magnitudes of the GST warming at the six selected borehole sites were respectively 20 years ago at 0.4 ℃,24 years ago at 0.72 ℃,26 years ago at 2.18 ℃,28 years ago at 4.2 ℃,30 years ago at 2.4 ℃,and 30 years ago at 2.4 ℃. Moreover,there is a pattern in the GST warming,least in the rural areas and greatest in the urbanized areas in Xi'an.