The circumglobal teleconnection (CGT) is an important mode of circulation variability, with an influence across many parts of the northern hemisphere. Here, we examine the excitation mechanisms of the CGT in the ECMWF seasonal forecast model, and the relationship between the Indian summer monsoon (ISM), the CGT and the extratropical northern hemisphere circulation. Results from relaxation experiments, in which the model is corrected to reanalysis in specific regions, suggest that errors over northwest Europe are more important in inhibiting the model skill at representing the CGT, in addition to northern hemisphere skill more widely, than west-central Asia and the ISM region, although the link between ISM precipitation and the extratropical circulation is weak in all experiments. Thermal forcing experiments in the ECMWF model, in which a heating is applied over India, suggest that the ISM does force an extratropical Rossby wave train, with upper tropospheric anticyclonic anomalies over east Asia, the North Pacific and North America associated with increased ISM heating. However, this eastward-propagating branch of the wave train does not project into Europe, and the response there occurs largely through westward-propagating Rossby waves. Results from barotropic model experiments show a response that is highly consistent with the seasonal forecast model, with similar eastward- and westward-propagating Rossby waves. This westward-propagating response is shown to be important in the downstream reinforcement of the wave train between Asia and North America.

环地球遥相关 (CGT) 是环流变率的一种重要模式，对北半球的许多地区都有影响。在这里，我们研究了 ECMWF 季节性预测模型中 CGT 的激发机制，以及印度夏季风 (ISM)、CGT 和温带北半球环流之间的关系。松弛实验的结果，其中模型被修正为在特定区域的再分析，表明欧洲西北部的错误在抑制代表 CGT 的模型技能方面更重要，除了北半球技能更广泛，比中西亚和 ISM 地区，尽管 ISM 降水与温带环流之间的联系在所有实验中都很弱。ECMWF 模型中的热强迫实验，其中印度上空加热，表明 ISM 确实迫使温带罗斯比波列，东亚、北太平洋和北美的对流层上层反气旋异常与 ISM 加热增加有关。然而，波列的这个向东传播的分支并没有投射到欧洲，那里的响应主要通过向西传播的罗斯比波发生。正压模型实验的结果显示了与季节性预测模型高度一致的响应，具有类似的向东和向西传播的罗斯比波。这种向西传播的响应被证明在亚洲和北美之间波列的下游增强中很重要。东亚、北太平洋和北美的对流层上层反气旋异常与 ISM 加热增加有关。然而，波列的这个向东传播的分支并没有投射到欧洲，那里的响应主要通过向西传播的罗斯比波发生。正压模型实验的结果显示了与季节性预测模型高度一致的响应，具有类似的向东和向西传播的罗斯比波。这种向西传播的响应被证明在亚洲和北美之间波列的下游增强中很重要。东亚、北太平洋和北美的对流层上层反气旋异常与 ISM 加热增加有关。然而，波列的这个向东传播的分支并没有投射到欧洲，那里的响应主要通过向西传播的罗斯比波发生。正压模型实验的结果显示了与季节性预测模型高度一致的响应，具有类似的向东和向西传播的罗斯比波。这种向西传播的响应被证明在亚洲和北美之间波列的下游增强中很重要。那里的响应主要通过向西传播的罗斯比波发生。正压模型实验的结果显示了与季节性预测模型高度一致的响应，具有类似的向东和向西传播的罗斯比波。这种向西传播的响应被证明在亚洲和北美之间波列的下游增强中很重要。那里的响应主要通过向西传播的罗斯比波发生。正压模型实验的结果显示了与季节性预测模型高度一致的响应，具有类似的向东和向西传播的罗斯比波。这种向西传播的响应被证明在亚洲和北美之间波列的下游增强中很重要。