1961—2010年桂林气温和地温的变化特征

Analysis on variation characteristics of air temperature and ground temperature in Guilin from 1961 to 2010

关于气温变化特征已有大量研究,但是关于地温变化及其与气温的关系研究还较少。以亚热带湿润地区的广西桂林气象站为研究对象,分析了1961—2010年桂林气温和0—80 cm各层地温的年代和季节变化趋势、地气温差变化、气候突变和异常年份以及气温和地温关系。结果表明:气温与各层地温有很好的相关性。各年、季平均气温和各层平均地温大部分呈显著的升高趋势,但气温和地温的增温速率不一致,即升温存在非对称性;年均气温低于各层地温1.3—2.1℃,气温的增温速率和增温幅度分别为0.184℃/10 a和0.8℃,高于除0 cm外其它各层地温的变化;气温、5—40 cm地温在冬季的增温最多,0 cm和80cm地温分别在秋季和夏季的增温最多;春、夏季,随着土壤深度的增加,地温呈减小趋势,春季气温小于0—15 cm而大于20—80 cm地温,夏季气温小于0—40 cm而大于80 cm地温;秋、冬季,随着土壤深度的增加,地温呈增加趋势,秋、冬季气温小于各层地温;气候变暖背景下,年平均、四季气温比除0 cm外其它各层地温的响应更快。近50年来,各层地温和气温的温差减小了0.1—0.4℃(0 cm地温和气温温差除外),这主要是因为气温的增加幅度要大于地温,且随着土壤深度的增加,地气温差的减小幅度加大。桂林年均地温和四季气温、地温大多无气候突变现象,仅有年均气温和夏季80 cm地温分别在1997和1977年出现气候突变。春季气温和5—80 cm各层地温的异常偏低年较一致;秋季气温和40、80 cm地温的异常偏低年相同;夏、冬季气温和地温的异常年份对应性较差;而年均气温和各层地温的异常偏高年较一致。

Lots of studies on characteristics of air temperature have been done, however, few studies on characteristics of ground temperature and its relationship with air temperature have been done yet. Based on the data of monthly mean air temperature and monthly mean ground temperature at 0--80cm soil depths in Guilin weather station from 1961 to 2010, variation trend, abrupt change, anomalous years of annual and seasonal mean air and ground temperatures were investigated in this paper. The difference and relationship between annual mean ground and air temperatures were also analyzed. The results showed that there were close correlations between ground temperature at different depths and air temperature. Annual and seasonal mean air and ground temperatures mainly displayed significant increasing trends in past 50 years, but the rise of mean air temperature and mean ground temperature was asymmetric. The annual mean air temperature was lower than annual mean ground temperature at different layers by 1.3--2. 1 °C. The ascending rate and range of annual mean air temperature were O. 184 °C/10a and 0.8 °C respectively, which were higher than changes of annual mean ground temperatureat 5--80cm depths. The ascending rates of air temperature and ground temperature at 5--40cm were the most obvious in winter, and the most significant increase of 0cm and 80cm ground temperature happened in autumn and summer respectively. The mean ground temperature had a decreasing trend with the increase of the soil depth in both spring and summer. The air temperature was lower than 0--15cm ground temperature and higher than 20--80cm ground temperature in spring, and air temperature was lower than 0--dOcm ground temperature and higher than 80cm ground temperature in summer. The mean ground temperature had a rising trend with the increase of soil depth in autumn and winter. The air temperature was lower than ground temperature at different depths in autumn and winter. Under global warming, the response of annual and seasonal air temperature to climate change was more significant than ground temperature at 5--80cm depths. The difference between annual ground temperature at 5--80cm depths and annual air temperature was reduced by 0.1--0.4°C in past 50 years, since the ascending rate of air temperature was larger than ground temperature, and the reducing amplitude of difference between annual mean ground temperature at 5--80cm depths and annual mean air temperature was increased with the increase of soil depth. The abrupt changes of annual mean air temperature and ground temperature at 80cm depth in summer occurred in 1997 and 1977 respectively. The anomalous lower years of air temperature and ground temperature at 5--80cm depths were relatively consistent in spring. There were the same anomalous lower years between air temperature and ground temperature at 40--80cm depths. The anomalous years of air and ground temperatures were less consistent in summer and winter. There were good consistent of anomalous warm years between annual air and ground temperatures.