气候变化背景下秦岭气候分界线的变化

 依据秦岭南北地区80个站点1980-2009年气象数据，主要应用空间分析方法对半干旱与湿润区、暖温带与亚热带界限的位置变动特征进行了分析。结果表明：（1）近30 a来，秦岭南北地区的气候干燥度呈明显的纬向分布，由北向南湿度依次增加，其线性趋势除商洛东北部，和西安中部地区呈增加变湿的趋势外，其余部分呈减少趋势；≥10 ℃积温天数呈纬向分布，由北向南依次增加，其线性趋势均为增加趋势，空间分布特征呈同心分布；（2）半干旱与湿润界限在20世纪80年代位置最北，在90年代最南，21世纪前10 a次之；暖温带与亚热带界限在20世纪80年代的位置最南、 90年代略有北移，且在21世纪前10 a位置最北；（3）秦岭南北地区的半干旱与湿润、暖温带与亚热带界限最大波动分别为1.2、0.5 个纬度，且两者30 a平均位置均在34 °N附近；（4）秦岭南北地区近30 a气候暖干化趋势明显，该区的半干旱与湿润区、暖温带与亚热带界限的北移可能会对该地区的种植制度产生较大影响。

Climatic boundary variation of Qinling Mountains areas under the background of climate change

Based on the meteorological data of 80 stations in the south and north areas of the Qingling Mountains over 1980-2009, and by applying spatial analysis method to analyze the boundaries’position variation between semiarid and humid areas, warm temperate and subtropical zones. Results indicate:(1) In the recent 30 a, the climate aridity index of the south and north areas of the Qinling Mountains showed an obvious latitudinal distribution, namely the humidity increased from the south to the north, and showed a linearly decreased tendency except the northeast of Shangluo City and the center of Xi’an City; the days of daily mean temperature ≥10 ℃ showed a latitudinal distribution, namely increased in turn from the north to the south, and showed a linearly increased tendency; the spatial distribution showed a concentric characteristic. (2) The position of semiarid and humid region’s boundary was at the northmost in the 1980s, and at the southmost in the 1990s, and in the middle position during the first decade of 21 st century; the position of warm temperate and subtropical zones’ boundary was at the southmost in the 1980s, and moved to the north in the 1990s, and at the northmost during the first decade of 21 st century. (3) The maximum position fluctuations of the boundaries between semiarid and humid areas, and warm temperate and subtropical zones were 1.2 degrees and 0.5 degree of latitude, respectively, in the study area; and the mean position of both boundaries was near the 34 °N. (4) In the recent 30 a, the warming and drying tendency was very prominent; the northward movement of the boundaries between semiarid and humid areas, and warm temperate and subtropical zones may have a great influence to the cropping system in the study area.