On the relationship between Iran surface temperature and northwest India summer monsoon rainfall
On the relationship between Iran surface temperature and northwest India summer monsoon rainfall
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伊朗地表温度与印度西北部夏季季风降雨量的关系
DOI：
10.1002/joc.4648
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
R. Yadav
中科院分区：
文献类型：
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作者：
R. Yadav
本研究考察了伊朗地表温度在印度西北部（NW）夏季（6月至9月）降雨调节中的作用。分析基于趋势分析、相关性和回归，使用ERA - Interim数据和印度气象部门基于1979年至2013年站点数据的降雨记录。夏季伊朗和印度西北部地表温度和降雨量分别呈上升趋势。伊朗地面温度的升高是由大西洋东北部/欧洲西北部传播的中纬度波列穿过欧亚地区到达伊朗的结果。这增加了伊朗上空对流层中高层的位势高度（GPH）异常，从而增加了沿大气柱垂直截面的对流层温度，由于对流层中层的强烈下降，对流层低层的升温最大。地表温度的升高分别增强了伊朗上空的地面低压区以及波斯湾和阿拉伯海北部的北风带和西风带的异常气旋环流。这些风汇聚向水汽供应充足的印度西北部，有利于深层对流。在大多数情况下，它动态地发展成东亚和西亚上空的阻塞脊，以及侵入印度西北部的异常高振幅中纬度槽，有利于强降雨事件。
This study examines the role of Iran surface temperature in modulating rainfall over northwest (NW) India during summer season spanning from June through September. The analysis is based on trend analysis, correlations and regressions performed using ERA‐Interim data and India Meteorological Department rainfall records based on station data from 1979 to 2013. The summer season shows increasing trends in surface temperature and rainfall over Iran and NW India, respectively. The increase of surface temperature over Iran is the consequence of mid‐latitude wave train that propagates from the northeastern Atlantic/NW Europe and traverses through Eurasian region to Iran. This increases the geopotential height (GPH) anomaly at upper to middle troposphere over Iran, which increases the tropospheric temperature along the vertical cross‐section of atmospheric column with maximum warming at the lower troposphere due to the strong descent at the middle tropospheric level. This increase in surface temperature intensifies the surface low‐pressure area over Iran and anomalous cyclonic circulation with northerlies and westerlies over Persian Gulf and north Arabian Sea, respectively. These winds converge towards NW India with abundant of moisture supply, favouring deep convection. The increase of GPH anomaly at upper to middle troposphere over Iran also intensifies the Tibetan High westward, accordingly shifting the monsoon rainfall westward. In most of the cases, it dynamically develops into blocking ridges over East and West Asia and an anomalous high‐amplitude mid‐latitude trough intrusion into NW India favouring very heavy rainfall events.