21世纪中蒙干旱-半干旱地区干旱化趋势的模拟研究

利用区域气候模式RegCM3与公用气候系统模式CCSM3单向嵌套技术，进行未来不同情景下（高排放SRES A2、中等排放SRES A1B和低排放SRES B1）高分辨率数值试验，分析21世纪中国和蒙古国干旱-半干旱地区干旱化特征及其可能发展趋势。结果表明：不同排放情景下，未来中蒙干旱-半干旱地区降水量均呈增加趋势，地表温度也持续增加。仅从降水变化来看，未来干旱-半干旱地区干旱化程度变化不大，甚至有所减弱。但综合考虑降水和温度计算的Palmer干旱指数（PDSI）来看，研究区内干旱地区面积均持续扩张。极端、严重及中等干旱面积比例扩张趋势明显，达到95%显著性水平。相对21世纪中期、后期极端干旱面积在3种情景下均将扩张3%以上。相对21世纪中期和当代，21世纪后期A2情景下总的干旱面积分别将增加8%和11.51%，A1B情景下12.48%和18.34%，B1情景下9.73%和10.82%。对比降水与PDSI可见，在进行干旱-半干旱区气候变化预估研究中，必须综合考虑降水和温度的变化，才能更准确地反映干旱-半干旱地区干旱化特征及其干旱化趋势。

A Modeling Study on Drought Trend in the Sino-Mongolian Arid and Semiarid Regions in the 21st Century

Using a regional climate model(RegCM3) nested in one-way mode within the Community Climate System Model(CCSM3),some high-resolution numerical experiments were conducted under the SRES A2,A1B and B1 scenarios for the 21st century,and the drought characteristics and their possible trends in the Sino-Mongolian arid and semiarid regions were analyzed.The results show that the precipitation and surface temperature have an obvious increasing trend under all scenarios.There is no clear drying trend in the 21st century based on the analyzed results of precipitation.Considering from the Palmer Drought Severity Index(PDSI),however,the signals of precipitation and temperature reveal that the drought area may be expanded continuously.The proportions of extremely severe,severe and moderate drought areas are increased,which are all significant at significance level of 95%.The extremely severe drought area was expanded by higher than 3% under all the scenarios in the late-21st century compared with that in the mid-21st century.Compared with mid-21st century and modern time,the drought areas will be enlarged by 8% and 11.51% under A2,12.48% and 18.34% under A1B,and 9.73% and 10.82% under B1 in the late-21st century,respectively.The change of both precipitation and temperature must be taken into account in predicting climate change in arid and semiarid regions so as to more accurately reflect the characteristics of drought and drying trend.