中文摘要：

采用1960-2009年112个地面观测站和21个探空站气象资料,分析中国西北地区近50年夏季0℃层高度和平均气温变化趋势。结果表明：西北地区近50年来夏季0℃层高度平均值为4675.7m,在1987年以前表现为下降趋势,平均每年下降5.6m,而1987年以后表现为显著的上升趋势,平均每年上升2.6m;夏季平均气温与0℃层高度变化趋势大致相同,西北气候显著转型前后表现出相反的变化趋势,且1987年以来夏季平均气温增加急剧,平均每10年上升0.53℃。1960年以来夏季0℃层高度在北京时间08时该区大部分地区表现出显著的上升趋势,而在20时大部分地区表现出相反的变化趋势,1987年以来在08时和20时大部分地区夏季0℃层高度都为上升趋势;50年来大部分地区夏季平均气温都表现为上升趋势,乌鲁木齐和秦巴山地则表现为显著的下降趋势。西北不同气候区的夏季0℃层高度和平均气温变化也有一定的差异。西北地区夏季0℃层高度和平均气温具有较好相关性,东部季风区相关性最差,青藏高寒区最好。

英文摘要：

Based on the data of 112 meteorological stations and 21 aerological stations in Northwest China from 1960 to 2009,the variation of 0 ℃ isotherm height and mean temperature in summer was analyzed.The result indicated that the mean height of 0 ℃ isotherm in summer was 4675.7 m during 1960-2009,with an annual decrease of 5.6 m before 1987 and an annual increase of 2.6 m after 1987.The ground temperature showed a similar annual trend at the 0 ℃ isotherm height,which was converse around the climatic mutation in Northwest China,with a considerable increase rate of 0.53 ℃ per decade after 1987.During 1960-2009,in most parts of Northwest China,the 0 ℃ isotherm height at Beijing Time 8：00 in summer increased significantly,and the height at Beijing Time 20：00 decreased.However,during 1987-2009,the 0 ℃ isotherm height in most parts of Northwest China increased at Beijing Time 8：00 and 20：00.A marked increasing trend of mean temperature in summer was observed in most parts of Northwest China,but the trend was opposite in Urumqi and Qinling-Daba Mountains.For the different climatic zones,the main trend and correlation between 0 ℃ isotherm height and mean temperature in summer varied spatially.The correlation was significant in the Cold Region on the Qinghai-Tibet Plateau,less significant in the Arid Region in Northwest China,and not significant in Monsoon Region in eastern China.