Robust Hadley Circulation changes and increasing global dryness due to CO2 warming from CMIP5 model projections
Robust Hadley Circulation changes and increasing global dryness due to CO2 warming from CMIP5 model projections
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DOI：
10.1073/pnas.1418682112
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发表时间：
2015-03-24
影响因子：
11.1
通讯作者：
Kim, Kyu-Myong
中科院分区：
文献类型：
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作者：
Lau, William K. M.;Kim, Kyu-Myong
本文从耦合模式对比计划第五阶段(CMIP5)模式投影出发，研究了在CO2变暖的情况下，Hadley环流(HC)的变化及其与全球干旱(降雨量减少和对流层相对湿度减少)的关系。我们发现，HC的加强表现为“深热带挤压”(DTS)，即对流层加深和变窄，上升增强，高云增多，低云被抑制，深热带对流层上部(200-100百帕)最大经向质量流出水平上升。DTS导致热带和亚热带地区的大气水汽辐散和对流层相对湿度降低，同时HC的下沉分支扩大，导致世界各地首选地理位置的干旱事件频率增加。在所考察的各种水循环参数中，全球干旱被发现具有最高的信噪比。我们的结果为推断温室气体变暖可能导致近几十年来观察到的全球持续干旱提供了物理基础。
In this paper, we investigate changes in the Hadley Circulation (HC) and their connections to increased global dryness (suppressed rainfall and reduced tropospheric relative humidity) under CO2 warming from Coupled Model Intercomparison Project Phase 5 (CMIP5) model projections. We find a strengthening of the HC manifested in a "deep-tropics squeeze" (DTS), i.e., a deepening and narrowing of the convective zone, enhanced ascent, increased high clouds, suppressed low clouds, and a rise of the level of maximum meridional mass outflowin the upper troposphere (200-100 hPa) of the deep tropics. The DTS induces atmospheric moisture divergence and reduces tropospheric relative humidity in the tropics and subtropics, in conjunction with a widening of the subsiding branches of the HC, resulting in increased frequency of dry events in preferred geographic locations worldwide. Among various water-cycle parameters examined, global dryness is found to have the highest signal-to-noise ratio. Our results provide a physical basis for inferring that greenhouse warming is likely to contribute to the observed prolonged droughts worldwide in recent decades.