Pattern-based statistical downscaling of East Asian Summer Monsoon precipitation
Pattern-based statistical downscaling of East Asian Summer Monsoon precipitation
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DOI：
10.3402/tellusa.v65i0.19749
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
T. Simon;A. Hense;Buda Su;T. Jiang;C. Simmer;C. Ohlwein
中科院分区：
文献类型：
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作者：
T. Simon;A. Hense;Buda Su;T. Jiang;C. Simmer;C. Ohlwein
摘要本研究确定了与鄱阳湖流域降水观测相关的每日梅雨型东亚夏季风模式。这种分析提供了深入了解强，局部降水事件的动态，并有可能提高预测的降水从粗网格数值模拟。1960年至1999年的降水观测来自13个雨量计位于鄱阳湖流域，这是长江流域的子流域。分析表明，这些观测结果与ERA-40再分析资料中850 hPa相对涡度（Vo 850）和500 hPa垂直速度（W500）的日型有关。这些模式是通过两种方法得到的：（a）经验正交函数（ERF）分析和（B）旋转ERF分析。Vo 850和W500分别代表地转和非地转过程。一个逻辑回归连接的大规模动态的本地观测，其中一个正向回归选择的模式最适合作为预测超过阈值的24小时累计降雨量的概率在仪表。通过交叉验证对回归模型进行了验证。探测到的模式的空间结构可以用著名的中α尺度扰动（称为西南涡）来解释。总的来说，建议的垂直和旋转的垂直模式都与物理过程有关，并有可能作为鄱阳流域局部降水的垂直率的预测。
ABSTRACT This study identifies daily Meiyu-like East Asian Summer Monsoon patterns that are linked to precipitation observations in the Poyang lake catchment. This analysis provides insight into the dynamics of strong, local precipitation events and has the potential to improve projections of precipitation from coarse-grid numerical simulations. Precipitation observations between 1960 and 1999 are taken from 13 rain gauges located in the Poyang lake catchment, which is a sub-catchment of the Yangtze River. The analysis shows that the observations are linked to daily patterns of relative vorticity at 850 hPa (Vo850) and vertical velocity at 500 hPa (W500) taken from the ERA-40 re-analysis data set. The patterns are derived by two approaches: (a) empirical orthogonal function (EOF) analysis and (b) rotated EOF analysis. Vo850 and W500 refer to geostrophic and ageostrophic processes, respectively. A logistic regression connects the large-scale dynamics to the local observations, whereby a forward regression selects the patterns best suited as predictors for the probability of exceeding thresholds of 24 h accumulated rainfall at the gauges. The regression model is verified by cross-validation. The spatial structure of the detected patterns can be interpreted in terms of well-known meso-α-scale disturbances called Southwest vortices. Overall, the proposed EOF and rotated EOF patterns are both related to physical processes and have the potential to work as predictors for exceedance rates of local precipitation in the Poyang catchment.