Potential Underestimation of Future Mei-Yu Rainfall with Coarse-Resolution Climate Models
Potential Underestimation of Future Mei-Yu Rainfall with Coarse-Resolution Climate Models
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DOI：
10.1175/jcli-d-17-0741.1
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发表时间：
2018-07
影响因子：
4.9
通讯作者：
Xiaolong Chen;P. Wu;M. Roberts;Tianjun Zhou
中科院分区：
文献类型：
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作者：
Xiaolong Chen;P. Wu;M. Roberts;Tianjun Zhou
梅雨锋6-7月降雨量占长江流域夏季总降水量的45%左右。由于其特殊的社会经济意义，它将如何在全球变暖下发生变化是中国人民非常关心的，但来自耦合模式比较项目(CMIP5)第五阶段的气候模式预测显示出很大的不确定性。本文研究了模式分辨率敏感性，并报告了Hadley中心最新气候模式HadGEM3全球耦合配置2.0(HadGEM3-GC2)的低分辨率(GaussN96网格，~1.5°经纬度)和高分辨率(N216，~0.7°)版本之间未来梅雨锋夏季降水预测的巨大差异。高分辨率模式在两个典型的浓度路径情景(RCP8.5和RCP4.5)下，夏季降水显著增加，而低分辨率模式则表现为减少。在高分辨率模式中，预计梅雨降雨量的较大增加也在整个CMIP5集合中观察到。这些差异可以用高分辨率模式中定常涡旋增强的湿静力能量平流和水汽辐合来解释。西北太平洋副热带高压对同一增温情景的大尺度反差表现为西北太平洋副热带高压对同一增温情景的反差响应，它在N216几乎没有变化，但在N96明显向东撤退，减少了西南风气流，从而减少了对梅雨锋的水汽供应。进一步提高模式分辨率以解决参数化过程和详细的地形特征，有望减少未来气候预测中的扩散。
The amount of rainfall during June and July along the mei-yu front contributes about 45% to the total summer precipitation over the Yangtze River valley. How it will change under global warming is of great concern to the people of China because of its particular socioeconomic importance, but climate model projections from phase 5 of the Coupled Model Intercomparison Project (CMIP5) show large uncertainties. This paper examines model resolution sensitivity and reports large differences in projected future summer rainfall along the mei-yu front between a low-resolution (Gaussian N96 grid, ~1.5° latitude–longitude) and a high-resolution (N216, ~0.7°) version of the Hadley Centre’s latest climate model, the HadGEM3 Global Coupled Configuration 2.0 (HadGEM3-GC2). The high-resolution model projects large increases of summer rainfall under two representative concentration pathway scenarios (RCP8.5 and RCP4.5) whereas the low-resolution model shows a decrease. A larger increase of projected mei-yu rainfall in higher-resolution models is also observed across the CMIP5 ensemble. These differences can be explained in terms of enhanced moist static energy advection and moisture convergence by stationary eddies in the high-resolution model. A large-scale manifestation of the anomalous stationary eddies is the contrasting response to the same warming scenario by the western North Pacific subtropical high, which is almost unchanged in N216 but retreats evidently eastward in N96, reducing the southwesterly flow and consequently moisture supply to the mei-yu front. Further increases in model resolution to resolve parameterized processes and detailed orographic features will hopefully reduce the spread in future climate projections.