This study examined the Inter‐decadal modulations of interannual El Niño‐Southern Oscillation (ENSO)‐Indian Summer Monsoon (ISM) rainfall regional teleconnection patterns in the observations and Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Observations show strong epochal changes of the relationship between ENSO and all‐India summer rainfall (AISR) with weak teleconnections in epoch‐1 (centred around 1915) and epoch‐4 (recent epoch) and strong teleconnections in epoch‐2 (centred around 1940) and epoch‐3 (centred around 1970) during the study period of 1901–2014. While on the regional point of view, it is found that epochal/decadal ENSO teleconnections to rainfall over northern central India and southern peninsular India are stronger and stable in all epochs. Whereas the rainfalls over the regions like Central India and Eastern Central India (ECI) displayed strong epochal changes in teleconnections, similar to that of AISR. This suggests that changes in ENSO‐ISM rainfall teleconnections are highly influenced by regional rainfall response. Anomalous upward motion over the head Bay of Bengal (BOB) and ECI regions related to Indian Ocean Dipole (IOD) and the westward extension of low‐level cyclonic circulation from the Western‐North Pacific (WNP) region are mainly responsible for the epochal changes in regional rainfall patterns over India associated with ENSO. We have assessed the fidelity of 29 CMIP6 models in representing the epochal changes in ENSO‐monsoon teleconnections. Nearly, 35% of models simulate epochal changes in teleconnections reasonably well. In most of the models, epochal changes in teleconnections are influenced by the strength and location of large‐scale subsidence coupled to the strength of Walker circulation associated with ENSO. It is noted that the drivers of epochal changes in ENSO‐monsoon teleconnections vary from model to model. Whereas, in the observations, the variance of ENSO itself in summer could influence modulations in the ENSO‐ISM teleconnections apart from IOD and WNP forcing.

中文翻译：

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观测和CMIP6模型年际ENSO-印度夏季风降雨遥相关的年代际调制：区域模式

这项研究在观测和耦合模型比较项目第六阶段（CMIP6）模型中研究了厄尔尼诺-南方涛动（ENSO）-印度夏季风（ISM）降雨区域遥相关模式的年代际调制。观测结果显示ENSO与全印度夏季降水（AISR）之间的关系发生了强烈的时代变化，第1个时期（集中在1915年左右）和第4个时期（最近一个时期）的遥相关性弱，而第2个时期（在1940年附近的集中性）强的遥相关性）和epoch‐3（以1970年为中心）在1901–2014年的研究期间。从区域角度来看，发现在印度中北部和印度南部半岛上与降雨的年代际/年代际ENSO遥相关在所有时期都更强和稳定。而印度中部和印度中部东部（ECI）等地区的降雨量显示出与AISR类似的强烈的远距变化。这表明ENSO‐ISM降雨远程连接的变化在很大程度上受到区域降雨响应的影响。与印度洋偶极子（IOD）有关的孟加拉湾（BOB）和ECI区域上空异常向上运动以及西太平洋-北太平洋（WNP）地区低空气旋环流向西扩展是造成时代变化的主要原因印度与ENSO相关的区域降雨模式的变化。我们评估了29种CMIP6模型的保真度，以表示ENSO-季风远程连接的时代变化。几乎有35％的模型可以很好地模拟远距连接的时代变化。在大多数模型中 远距连接的时代变化受大规模沉陷的强度和位置以及与ENSO相关的沃克环流强度的影响。需要注意的是，ENSO-季风遥相关的时代变化的动因因模型而异。然而，在观测中，除了IOD和WNP强迫外，夏季ENSO本身的变化可能会影响ENSO-ISM远程连接中的调制。