1961-2010年桂林气温和地温的变化特征

Abstract

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℃.The ascending rate and range of annual mean air temperature were 0.184℃/10a and 0.8℃ respectively,which were higher than changes of annual mean ground temperature at 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—40cm 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℃ 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.