Global warming and 21st century drying
Global warming and 21st century drying
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DOI：
10.1007/s00382-014-2075-y
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发表时间：
2014-11-01
期刊：
影响因子：
4.6
通讯作者：
Coats, Sloan
中科院分区：
文献类型：
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作者：
Cook, Benjamin I.;Smerdon, Jason E.;Coats, Sloan
全球变暖预计将增加二十一世纪干旱的频率和强度，但水分供应（降水）变化与蒸发需求（潜在蒸散量；PET）的相对贡献尚未得到全面评估。利用耦合模型比对项目第五阶段的一套大气环流模型 (GCM) 模拟的输出，使用两个离线的地表水分平衡指数：帕尔默干旱严重度指数 (PDSI) 和标准化降水蒸散指数 (SPEI)，对预测的二十一世纪干燥和湿润趋势进行了研究。 PDSI 和 SPEI 使用来自 GCM 的降水和基于 Penman-Monteith 的 PET 变化进行的预测基本一致，显示北美西部、中美洲、地中海、非洲南部和亚马逊地区出现强烈的跨模型干燥，而北半球高纬度地区和东非则出现强烈的湿润（仅 PDSI）。 SPEI 对 PET 变化比 PDSI 更敏感，尤其是在撒哈拉和中东等干旱地区。尽管 PDSI 和 SPEI 计算中的干燥范围超出了降水减少的区域，但区域干燥和湿润模式在很大程度上反映了模型中降水的空间异质响应。干燥区域的扩大归因于全球范围内 PET 的广泛增加，这是由表面净辐射和蒸气压不足的增加引起的。 PET 的增加不仅会加剧降水量已经减少的地区的干燥，还会使原本仅因降水趋势而几乎不会出现干燥甚至湿润的地区陷入干旱。这种PET放大效应在北半球中纬度地区最大，在北美西部、欧洲和中国东南部尤为明显。与仅使用降水变化的 PDSI 预测相比，结合降水和 PET 变化的预测将预计到 21 世纪末经历至少中度干燥（PDSI 标准差 B-1）的全球陆地面积百分比从 12% 增加到 30%。在 SPEI 预测中，PET 引起的中度干燥甚至更为严重（SPEI 标准差为
Global warming is expected to increase the frequency and intensity of droughts in the twenty-first century, but the relative contributions from changes in moisture supply (precipitation) versus evaporative demand (potential evapotranspiration; PET) have not been comprehensively assessed. Using output from a suite of general circulation model (GCM) simulations from phase 5 of the Coupled Model Intercomparison Project, projected twenty-first century drying and wetting trends are investigated using two offline indices of surface moisture balance: the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Evapotranspiration Index (SPEI). PDSI and SPEI projections using precipitation and Penman-Monteith based PET changes from the GCMs generally agree, showing robust cross-model drying in western North America, Central America, the Mediterranean, southern Africa, and the Amazon and robust wetting occurring in the Northern Hemisphere high latitudes and east Africa (PDSI only). The SPEI is more sensitive to PET changes than the PDSI, especially in arid regions such as the Sahara and Middle East. Regional drying and wetting patterns largely mirror the spatially heterogeneous response of precipitation in the models, although drying in the PDSI and SPEI calculations extends beyond the regions of reduced precipitation. This expansion of drying areas is attributed to globally widespread increases in PET, caused by increases in surface net radiation and the vapor pressure deficit. Increased PET not only intensifies drying in areas where precipitation is already reduced, it also drives areas into drought that would otherwise experience little drying or even wetting from precipitation trends alone. This PET amplification effect is largest in the Northern Hemisphere mid-latitudes, and is especially pronounced in western North America, Europe, and southeast China. Compared to PDSI projections using precipitation changes only, the projections incorporating both precipitation and PET changes increase the percentage of global land area projected to experience at least moderate drying (PDSI standard deviation of B-1) by the end of the twenty-first century from 12 to 30 %. PET induced moderate drying is even more severe in the SPEI projections (SPEI standard deviation of