Empirical–Statistical Downscaling of Austral Summer Precipitation over South America, with a Focus on the Central Peruvian Andes and the Equatorial Amazon Basin
Empirical–Statistical Downscaling of Austral Summer Precipitation over South America, with a Focus on the Central Peruvian Andes and the Equatorial Amazon Basin
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DOI：
10.1175/jamc-d-20-0066.1
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发表时间：
2021-01
影响因子：
3
通讯作者：
Juan C. Sulca;M. Vuille;O. Timm;B. Dong;Ricardo Zubieta
中科院分区：
文献类型：
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作者：
Juan C. Sulca;M. Vuille;O. Timm;B. Dong;Ricardo Zubieta
降水是使用大尺度预测因子最难估计的变量之一。在南美洲，鉴于安第斯山脉复杂的地形，这一任务更具挑战性。经验 - 统计降尺度（ESD）模型可用于此目的，但适用于整个南美洲的此类模型尚未开发出来。为了解决这一问题，我们利用多元线性回归技术构建了一个1982 - 2016年期间的ESD模型，该模型基于代表热带太平洋、大西洋和南美洲气候变率的大尺度环流指数，以估计南美洲的南半球夏季[12月 - 2月（DJF）]降水。统计分析表明，ESD模型能够重现热带安第斯山脉（厄瓜多尔、哥伦比亚、秘鲁和玻利维亚）、赤道东亚马逊流域以及阿根廷西部安第斯山脉中部观测到的降水异常。在更小的尺度上，ESD模型在秘鲁安第斯山脉的西科迪勒拉山脉也显示出良好的结果。ESD模型重现了三次极端厄尔尼诺事件（1982/83、1997/98和2015/16）期间赤道东亚马逊地区异常干燥的条件以及南美洲东南部（SESA）的湿润条件。然而，它高估了南美洲东南部观测到的强度。以秘鲁中部安第斯山脉作为案例研究，结果进一步表明，ESD模型能够正确重现三次极端厄尔尼诺事件期间整个曼塔罗盆地的DJF降水异常。此外，对ESD模型的不同预测因子组合进行的多次实验证实了南大西洋辐合带和赤道大西洋之间的相互作用导致了2015/16年亚马逊干旱这一假设。
Precipitation is one of the most difficult variables to estimate using large-scale predictors. Over South America (SA), this task is even more challenging, given the complex topography of the Andes. Empirical–statistical downscaling (ESD) models can be used for this purpose, but such models, applicable for all of SA, have not yet been developed. To address this issue, we construct an ESD model using multiple-linear-regression techniques for the period 1982–2016 that is based on large-scale circulation indices representing tropical Pacific Ocean, Atlantic Ocean, and South American climate variability, to estimate austral summer [December–February (DJF)] precipitation over SA. Statistical analyses show that the ESD model can reproduce observed precipitation anomalies over the tropical Andes (Ecuador, Colombia, Peru, and Bolivia), the eastern equatorial Amazon basin, and the central part of the western Argentinian Andes. On a smaller scale, the ESD model also shows good results over the Western Cordillera of the Peruvian Andes. The ESD model reproduces anomalously dry conditions over the eastern equatorial Amazon and the wet conditions over southeastern South America (SESA) during the three extreme El Niños: 1982/83, 1997/98, and 2015/16. However, it overestimates the observed intensities over SESA. For the central Peruvian Andes as a case study, results further show that the ESD model can correctly reproduce DJF precipitation anomalies over the entire Mantaro basin during the three extreme El Niño episodes. Moreover, multiple experiments with varying predictor combinations of the ESD model corroborate the hypothesis that the interaction between the South Atlantic convergence zone and the equatorial Atlantic Ocean provoked the Amazon drought in 2015/16.