Enhanced spring convective barrier for monsoons in a warmer world?
Enhanced spring convective barrier for monsoons in a warmer world?
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DOI：
10.1007/s10584-010-9973-8
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发表时间：
2011
期刊：
影响因子：
4.8
通讯作者：
A. Seth;S. Rauscher;M. Rojas;A. Giannini;S. Camargo
中科院分区：
文献类型：
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作者：
A. Seth;S. Rauscher;M. Rojas;A. Giannini;S. Camargo
21世纪气候模型的预测显示，热带降水的年度循环在雨季和旱季都有所增强，但不确定性很大，很少有研究对过渡季节进行审查。在这里，我们分析了全球陆地季风的耦合气候模式预测，并显示了北部(北美、西非和东南亚)和南部(南美、南部非洲)地区从春季到夏季的降水重新分配。年度周期变化是全球性的。通过年度循环评估了两种机制，即远程机制(基于对流层稳定性)和本地机制(基于低层和地面湿度)。对流层稳定性的增加从冬季持续到春季，并因地面湿度条件的减少而得到加强，这表明在春季，远程和本地机制都起到了抑制对流的作用。这种增强的春季对流屏障导致早期降雨量减少；然而，一旦获得足够的水分增加(通过输送)，对流层稳定性的降低导致雨季后期降雨量增加。需要在观察和模型中进一步研究这一机制，因为预计的变化将对农业、水管理和备灾产生重大影响。
Twenty-first century climate model projections show an amplification of the annual cycle in tropical precipitation with increased strength in both wet and dry seasons, but uncertainty is large and few studies have examined transition seasons. Here we analyze coupled climate model projections of global land monsoons and show a redistribution of precipitation from spring to summer in northern (North America, West Africa and Southeast Asia) and southern (South America, Southern Africa) regions. The annual cycle changes are global in scale. Two mechanisms, remote (based on tropospheric stability) and local (based on low level and surface moisture), are evaluated through the annual cycle. Increases in tropospheric stability persist from winter into spring and are reinforced by a reduction in surface moisture conditions, suggesting that in spring both remote and local mechanisms act to inhibit convection. This enhanced spring convective barrier leads to reduced early season rainfall; however, once sufficient increases in moisture (by transport) are achieved, decreases in tropospheric stability result in increased precipitation during the late rainy season. Further examination of this mechanism is needed in observations and models, as the projected changes would have substantial implications for agriculture, water management, and disaster preparedness.