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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年问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。
There is a necessary internal relationship between the shallow ground surface temperature and the near surface air temperature. The information about the surface temperature change propagates downwards and overlaps with the steady-state temperature field over time, so the analysis of present geothermal profile can reconstruct the past ground temperature History of change. In order to study the underground temperature and ground temperature in Xi’an, this paper carried out borehole temperature measurement in Xi’an, obtained the geothermal profile of 16 boreholes, and collected the temperature data of Xi’an meteorological station from 1951 to 2010. Regression analysis of the temperature data from 1951 to 2010 showed that the annual average temperature in Xi’an was 3.71 ℃ / 100a, 2.03 ℃ / 100a and 5.14 ℃ / 100a respectively, both higher than the national average and the global average The average level of which the average temperature in 1986 ~ 2010 warming is even more significant, reaching 9.01 ℃ / 100a. From the borehole temperature measurement curve, six conductive ground-temperature profiles in suburbs of Xi’an were selected and analyzed. The results showed that the trend of ground temperature recorded by borehole temperature in Xi’an basically coincided with the temperature trend recorded by the meteorological observatory. According to the steady-state surface temperature and the geothermal gradient obtained from the regression analysis of the lower part of the borehole temperature profile and the average temperature increase rate in Xi’an over the 25-year period, the theoretical geothermographic data of the borehole are generally in good agreement with the measured geothermal data. Further precise fitting analysis of the measured geothermal data shows that the surface temperature warming of the six selected borehole areas in the suburbs of Xi’an starts at 20, 24, 26, 28, 30 and 30 years respectively, Correspondingly, the warming rates of the surface are 0.4 ℃, 0.72 ℃, 2.18 ℃, 4.2 ℃, 2.4 ℃ and 2.4 ℃ respectively. There is a clear difference in the rate of temperature increase between the urban area and the surrounding suburbs where the borehole is located. The warming intensity in the urban area is obviously higher than that in the suburbs, while the suburban area is between the two.