Interannual variability of winter precipitation over northwest India and adjoining region: impact of global forcings
Interannual variability of winter precipitation over northwest India and adjoining region: impact of global forcings
复制标题
DOI：
10.1007/s00704-013-0968-z
复制
发表时间：
2014-05
影响因子：
3.4
通讯作者：
S. Kar;Sapna Rana
中科院分区：
文献类型：
--
作者：
S. Kar;Sapna Rana
厄尔尼诺/南方涛动（ENSO）的作用以及ENSO影响印度西北部和邻近地区（NWIA）降水变化的机制已有很好的文献记载。本文通过对观测资料的分析，估计了北大西洋涛动（NAO）/北极涛动（AO）和ENSO对北方冬季亚洲急流的相对调制作用及其对该地区降水变率的相对影响。结果表明，西北亚热带降水的年际变化主要受ENSO的影响。本文利用经验正交函数分析了北方半球200 hPa纬向风年际变化的主要模态。热带地区的ENSO-1型与ENSO型相似，主成分时间序列与ENSO时间序列相对应。NAO/AO与PC时间序列的相关系数分别为0.74和0.62。与PC-1相比，感兴趣区域的降水异常时间序列与PC-2时间序列的相关性略高。降水和环流参数的回归分析表明，第二模态的风和降水的变化在西北工业区的贡献较大。在NAO/AO活动阶段，来自阿拉伯海的水汽输送和气旋异常的存在导致西北偏北地区降水偏多。
The role of El Niño/Southern Oscillation (ENSO) and the mechanism through which ENSO influences the precipitation variability over northwest India and the adjoining (NWIA) region is well documented. In this study, the relative role of North Atlantic Oscillation (NAO)/Arctic Oscillation (AO) and ENSO in modulating the Asian jet stream in the Northern Hemisphere winter and their relative impact on the precipitation variability over the region have been estimated through analysis of observed data. It is seen that interannual variations of NWIA precipitation are largely influenced by ENSO. An empirical orthogonal function (EOF) analysis has been carried out to understand dominant modes of interannual variability of zonal wind at 200 hPa of the Northern Hemisphere. The EOF-1 pattern in the tropical region is similar to that of an ENSO pattern, and the principal component (PC) time series corresponds to the ENSO time series. The EOF-2 spatial pattern resembles that of NAO/AO with correlation of PC time series with AO and NAO being 0.74 and 0.62, respectively. The precipitation anomaly time series over the region of interest has marginally higher correlation with the PC-2 time series as compared to that of PC-1. Regression analysis of precipitation and circulation parameters indicates a larger contribution of the second mode to variability of winds and precipitation over the NWIA. Moisture transport from the Arabian Sea during the active phase of NAO/AO and the presence of a cyclonic anomaly lead to higher precipitation over the NWIA region.