Extreme Daily Rainfall in Pakistan and North India: Scale Interactions, Mechanisms, and Precursors
Extreme Daily Rainfall in Pakistan and North India: Scale Interactions, Mechanisms, and Precursors
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DOI：
10.1175/mwr-d-17-0258.1
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发表时间：
2018-04-01
影响因子：
3.2
通讯作者：
Shaffrey, Len C.
中科院分区：
文献类型：
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作者：
Hunt, Kieran M. R.;Turner, Andrew G.;Shaffrey, Len C.
虽然印度大部分地区在夏季季风期间习惯于强降水和频繁的低压系统，但向西北方向和巴基斯坦，这种事件并不常见。在这里，多达三分之一的年降雨量是在冬季季风期间由西部扰动零星提供的。这一地区北部通常是多山的山谷，南部通常是沙漠，如果出现这种稀少但强降水的情况，可能是灾难性的，2010年7月巴基斯坦洪水就是一个例子。在这项研究中，极端降水事件（EPEs）在一个盒子大约覆盖这个地区（25度-38度N，65度-78度E）确定使用APHRODITE规范为基础的降水产品。的大规模流通中造成EPEs的作用进行了研究：它被发现，在冬季，它往往与上层对流层Rossby波列，有显着的异常南风感兴趣的区域。这些冬季EPEs也被发现强烈搭配事件西方的干扰，而那些发生在夏季被发现有一个不太直接的关系。相反，夏季EPEs被发现与热带低压有很强的关系。一个详细的拉格朗日方法被用来探索可能的水分来源，这样的事件，并建议，在冬季，水分主要是从阿拉伯海，而在夏季，它来自沿着非洲海岸和印度季风槽地区。
While much of India is used to heavy precipitation and frequent low pressure systems during the summer monsoon, toward the northwest and into Pakistan, such events are uncommon. Here, as much as a third of the annual rainfall is delivered sporadically during the winter monsoon by western disturbances. Such events of sparse but heavy precipitation in this region of typically mountainous valleys in the north and desert in the south can be catastrophic, as in the case of the Pakistan floods of July 2010. In this study, extreme precipitation events (EPEs) in a box approximately covering this region (25 degrees-38 degrees N, 65 degrees-78 degrees E) are identified using the APHRODITE gauge-based precipitation product. The role of the large-scale circulation in causing EPEs is investigated: it is found that, during winter, it often coexists with an upper-tropospheric Rossby wave train that has prominent anomalous southerlies over the region of interest. These winter EPEs are also found to be strongly collocated with incident western disturbances whereas those occurring during the summer are found to have a less direct relationship. Conversely, summer EPEs are found to have a strong relationship with tropical lows. A detailed Lagrangian method is used to explore possible sources of moisture for such events and suggests that, in winter, the moisture is mostly drawn from the Arabian Sea, whereas during the summer, it comes from along the African coast and the Indian monsoon trough region.