中文摘要：

干旱是我国北方地区最为突出的环境问题。根据WCRP耦合模式输出的未来气候变化逐月资料,基于降水-蒸发力标准化干旱指数（SPEI）,分析了IPCC SRES A1B、A2和B1三种情景下,2011-2050年我国北方地区干旱状况的时空变化趋势。结果表明：中国北方地区未来40 a呈现干旱化倾向,其中轻度和中度季节性干旱发生频率降低,重度和极端季节性干旱发生频率增加,增温引起的地表蒸发增加是极端干旱频发的主要原因。A1B、B1和A2情景下,2040s整个北方地区极端干旱频率增加、强度增强、影响范围明显扩大。极端干旱的增加可能给农业生产带来风险,采取有效应对措施,将有利于区域农业的可持续发展。

英文摘要：

Drought is an insidious, slow-onset natural hazard that produces a complex web of impacts that ripple through many sectors of economy. As vulnerability to drought increase because of mounting pressure on water and other natural resources, it is clear that the scientific community faces a significant challenge to produce more timely and more comprehensive assessment of impacts. The development of drought projection is facilitated by the general circulation model （GCM）. Based on the monthly data under SRES A1B, A2 and B1 climate scenario （2011-2050） and the baseline （ 1971-2010） from the third phase of the coupled model intercomparsion proj ec- tion （CMIP3） multi-model datasets with resolution of 1 o~ 1 o, the standardized precipitation evapotranspiration in- dex （SPE1）, which is proved to be suited to detecting, monitoring and exploring the consequences of global warming on drought conditions, is used in the drought projection in the North China. The results indicate that the North China faces a drying trend for all scenarios in the next 40 years. The increases in precipitation are offset by increased evaporation. In general, changes under the higher emission scenarios, A2 and A1B are greater, and de- spite following a reduced emissions pathway relative to the present day, the B 1 scenario shows smaller but still substantial increase in drought. Under the future projections, the mild and moderate drought occurs less frequent- ly, while the severe and extreme drought occurs more frequently. Compared with the baseline of 1971-2010, the extreme drought frequency for 36%, 48% and 60% of the pixels increase greater than 2 times· （10 a） -1 in 2040s under B 1, A1B and A2 climate scenario, respectively. Regionally, the semi-arid regions show large increase most notably for extreme drought frequency, followed by the arid region, semi-humid region and humid region under three climate change scenarios. The spatial extent of extreme drought do not show significant increasing trend in the next 30 years