中国干旱区温度带界线对气候变暖的响应

Responses of Temperature Zone Boundaries in the Arid Region of China to Climatic Warming

在全球气候变暖大背景下,热量资源的改变与温度带界线的动态变化将会影响到干旱区天然植被的生长与分布,而农业气候资源的变化将对干旱区农业生产的布局与种植制度的调整产生深刻影响。本文采用1961-2007年均一化气温数据与MPI_ECHAM5模式输出的21世纪上半叶A1B情景下的区域降尺度格点数据,选取保证率为80%的日均温≥10℃持续日数等值线和日均温≥10℃等积温线为干旱区温度带北界指标,探讨了过去近50年及21世纪上半叶气候变暖背景下中国干旱区温度带界线的动态变化。研究表明,(1)1961-2007年,干旱区夏、冬半年气温呈显著增加趋势,且冬半年较夏半年增温幅度要大;各年代日均温≥10℃积温与≥10℃持续日数的等值线动态变化一致,均表现为显著向北或向高海拔推移;(2)通过对温度带北界指标变化的判断,1961-2007年干旱区暖温带和中温带北界普遍北移,北移幅度最大者为阿拉善地区,超过1个纬度;21世纪上半叶,暖温带和中温带北界将继续北移,且暖温带移动趋势更为显著;无论是过去近50年,还是21世纪上半叶,干旱区暖温带和中温带北界均有向高海拔区域移动趋势;(3)与温度带北界的变动相对应,干旱区生长期起始日期和终霜日等气候指标显著提早,天然植被与作物种植北界向北向西推移,并呈现向高海拔区域扩展的态势。因此,综合考虑农业气候资源变化以及人类活动的影响,从而确定气候条件与农业生产种植之间的反馈关系,这将是下一步研究的重点。

Under the background of global climatic warming,the growth and distribution of natural vegetations will be influenced by the variation of heat resources and the dynamic changes of temperature zones.And the variation of agro-climatic resources will have great impacts on the distribution of agricultural production,and the adjustment of cropping systems as well.Therefore,the dynamic changes of the temperature zone boundaries in the arid region of China were explored during the past 50 years and under the scenarios in the first half of the 21st century.Here we adopted two kinds of data,i.e.,regional downscaling gridding data under the A1B scenarios in the first half of the 21st century simulated by the model of MPI_ECHAM5,and the homogenization temperature data during the period of 1961-2007,respectively.And the isolines for the duration and the accumulated temperatures of the daily mean temperature ≥ 10 ℃ with the guaranteed rate of 80% were selected as the index of the northern boundaries of temperature zones in the arid region of China.The main conclusions are summarized as follows.Firstly,the temperature increased apparently for both summer half-year and winter half-year during the period of 1961-2007,and the increasing amplitude of temperature was larger in the winter half-year than in the winter half-year.The dynamic changes of the isolines for the decadal accumulated temperatures and the duration of the daily mean temperature ≥ 10 ℃ were consistent,which demonstrated an obvious movement northward or upward to higher elevations.Secondly,judged by the changes of index for the northern boundaries of temperature zone,the northern boundaries of the warm and middle warm temperate zones moved northward generally,particularly for the Alxa League（prefecture） with a maximum movement of more than one latitude during 1961-2007.It is speculated that the northern boundaries of warm and middle temperate zones would move northward continually,among which the former would move much more remarkable in the first half of the 21st century.Moreover,the northern boundaries showed a tendency of moving upward to higher elevations not only for the warm temperate zone,but also for the middle temperate zone in the arid region of China in the first half of the 21st century.Thirdly,corresponding with the dynamic changes of temperature zones,several related climatic factors,e.g.,the first date of the growing season and the last frost date appeared earlier significantly,and the northern boundaries of natural vegetation and crop planting moved northward and westward,and extended upward in regions with higher elevations.