Dynamical mechanisms linking Indian monsoon precipitation and the circumglobal teleconnection
Dynamical mechanisms linking Indian monsoon precipitation and the circumglobal teleconnection
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DOI：
10.1007/s00382-021-05825-6
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发表时间：
2021-06
期刊：
影响因子：
4.6
通讯作者：
J. Beverley;S. Woolnough;L. Baker;Stephanie J. Johnson;A. Weisheimer;C. O’Reilly
中科院分区：
文献类型：
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作者：
J. Beverley;S. Woolnough;L. Baker;Stephanie J. Johnson;A. Weisheimer;C. O’Reilly
环全球遥相关（CGT）是一种重要的环流变率模态，其影响遍及北方的许多地区。本文研究了ECMWF季节预报模式中CGT的激发机制，以及印度夏季风（ISM）、CGT和北方半球外环流之间的关系。从松弛实验，在该模型被纠正到再分析在特定地区的结果表明，在欧洲西北部的错误是更重要的抑制模型的技能，在代表CGT，除了北方半球的技能更广泛，比中西部亚洲和ISM地区，虽然ISM降水和对流层外环流之间的联系是弱的，在所有的实验。在ECMWF模式，其中加热是适用于印度的热强迫实验表明，ISM确实迫使一个extratrophic Rossby波列，与东亚，北太平洋和北美的对流层上部反气旋异常与ISM加热增加。然而，波列向东传播的分支并没有投射到欧洲，那里的响应主要是通过向西传播的罗斯贝波发生的。正压模式实验的结果表明，响应是高度一致的季节性预报模型，类似的向东和向西传播的罗斯贝波。这种向西传播的响应被证明是重要的亚洲和北美之间的波列的下游加强。
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.