西藏高原农业界限温度的变化特征

Climatic Change of Agriculture Critical Temperature over Tibetan Plateau from 1971 to 2000

根据西藏1971～2000年≥0℃、10℃界限温度资料,建立了小网格推算模式,应用GIS推算出500m×500m网格点上的农业界限温度值,分析了界限温度的空间分布特征、趋势变化、年代际变化和气候异常。结果表明:界限温度持续日数及积温总的分布趋势自东南向西北减小,并随着海拔高度的升高、纬度的增大而减小。过去30年,西藏大部分站点≥0℃表现为初日提早、终日推迟、持续日数延长、积温增加的趋势。20世纪70年代,各站点≥0℃积温偏少,持续日数较短;主要农区≥10℃积温呈逐年代增加趋势,90年代热量最充足。前20年西藏各站点≥0℃的积温未出现过异常偏高年,90年代后期大部分站点发生了异常偏高年。

Based on the data of critical temperature (0oC, 10oC) over the Tibetan Plateau from 1971 to 2000, we established the small grid reckon model and calculated the critical temperature values of 500 m × 500 m grid node by GIS. The spatial distributions, linear trend, inter-decadal variations and climatic anomalous year of the critical temperature were analyzed. The results show that the duration of the critical temperature and the distribution trend of accumulated temperature decrease from southeast to northwest and also decrease with the increase of altitude and latitude. During the last 30 years, the variations trend of the critical temperature ≥0 oC present the characteristics of first day becoming earlier, terminal day postponing, duration prolonging and the accumulated temperature increasing. In the 1970s, the phenomena of the accumulated temperature ≥0 oC decreasing and duration shortening ocurred in most of the weather stations in Tibet. It was also found that the inter-decadal variations trend of the accumulated temperature ≥10 oC increased in main agricultural zones during the 30 years, the phase of thermal abundance appeared in the 1990s. There were less anomalous higher years with the accumulated temperature ≥0 oC at all weather stations in Tibet from 1971 to 1990, whereas anomalous higher years occurred in most part of Tibet during the period of the late 1990s.