Abstract: Based on monthly average air temperature and ground temperature data from 54 meteorological stations during 1965-2014,and air temperature and ground temperature data observed manually and automatically from 45 meteorological stations in 2003 in Liaoning province,the variation characteristics of air temperature,ground temperature and the differences between ground and air temperatures (GATD) in Liaoning province over the past 50 years and their causes were analyzed.Results show that the air and ground temperatures are linearly correlated each other and both demonstrate an increasing trend,while GATD varies little during 1965-2003.Since 2004,air temperature has slightly changed and ground temperature has continued to rise as well as GATD has increased relative to the last 10 years.However,the above-mentioned conditions most significantly occur in winter in the northeast area of Liaoning province.Manual observation has been entirely replaced by automatic one in meteorological stations of Liaoning province since 2004.Under snowfall weather,the ground temperature is respectively represented by the snow surface temperature for manual observation and with the temperature below the snow for automatic observation.The difference of the ground temperature caused by different observation ways plays a dominant role for ground temperature continuously increasing during 2004-2014.Therefore,the northeast of Liaoning province with the longest duration of the snow cover becomes the region where GATD increases most significantly.Thus this suggests that the increases in ground temperature and GATD during 2004-2014 attribute mainly to the change of observation ways.

Key words: Air temperature, Ground temperature, Ground-air temperature difference, Manual observation, Automatic observation