中国干湿区变化与预估

本文采用干湿指数对1962~2011年中国干湿区范围变化进行了集中分析，并利用CMIP5（Coupled Model Intercomparison Project Phase 5）模式对其变化趋势开展了预估研究。结果表明，1962~2011年平均极端干旱区、干旱区、半干旱区、半湿润区和湿润区分别占中国陆地总面积的2.8%、11.7%、22.4%、32.6%和30.5%。期间，中国区域年干湿指数总体上呈现下降趋势，空间上表现为西部湿润化和东部干旱化的特征。显著缩小的是湿润区和极端干旱区，半湿润区、半干旱区和干旱区则显著扩大，这表明中国气候敏感区域在扩张。春季和秋季干湿指数变化趋势的空间分布与年平均的较为一致，冬季西北呈干旱化，夏季东南部地区为湿润化。相对于参考时段1986~2005年，在RCP4.5（Representative Concentration Pathway 4.5）情景下18个气候模式中位数的预估结果中，降水仅在东南南部减少，而潜在蒸散发在全区域增加，由于潜在蒸散发的增量超过了降水的增幅，中国区域将整体趋于干旱化，仅在西北地区呈湿润化特征；未来湿润区、干旱区和极端干旱区缩小，气候敏感性高的半湿润区和半干旱区仍将扩大。

Changes and Projection of Dry/Wet Areas over China

Based on the dry/wet index, the authors analyzed changes in dry/wet regions over China and projected their future change scenarios using CMIP5 (Coupled Model Intercomparison Project Phase 5) models. For the period of 1962-2011, the results show that the averages of extreme arid, arid, semi-arid, semi-humid, and humid regions account for 2.8%, 11.7%, 22.4%, 32.6%, and 30.5% of the land area of the country, respectively. The dry/wet index decreases overall and tends to become wet in the west and dry in the east. There is a significant contraction of humid and extreme arid regions but a significant expansion of semi-humid, semi-arid, and arid regions, indicating an increase in the climatically sensitive regions. The distribution of the change trend of dry/wet index during the spring and autumn resembles that of the annual mean, and the northwest tends to become dry during the winter while the southeast is becoming wet during the summer. Under the RCP4.5 (Representative Concentration Pathway 4.5) scenario, the median of the 18 CMIP5 models shows that, relative to the period of 1986-2005, annual precipitation would decrease only in the southeast, and the potential evapotranspiration would increase over the entire country, leading to dry/wet index decreases in most regions except the western part. The humid, arid, and extreme arid regions would reduce, while the opposite is true for the semi-arid and semi-humid regions.