Remote influence of the interannual variability of the Australian summer monsoon on wintertime climate in East Asia and the western North Pacific
Remote influence of the interannual variability of the Australian summer monsoon on wintertime climate in East Asia and the western North Pacific
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DOI：
10.1175/jcli-d-21-0202.1
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发表时间：
2021-09
影响因子：
4.9
通讯作者：
Shion Sekizawa;H. Nakamura;Y. Kosaka
中科院分区：
文献类型：
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作者：
Shion Sekizawa;H. Nakamura;Y. Kosaka
海面温度（SST）变化所导致的热带地区异常对流活动产生了显着的远程影响，为温带地区的季节预测提供了基础。在澳大利亚夏季，对流活动在澳大利亚北部（NAUS）表现出明显的年际变化，然而，这不太可能是由于海温异常造成的，而是本质上是澳大利亚夏季风（AUSM）系统内部变化的表现。基于观测数据，本研究揭示了其对东亚和北太平洋西部冬季气候的重大远程影响。通过大气环流模型实验证实，异常AUSM激发了西太平洋（WP）模式。通过这种跨赤道遥相关，增强的AUSM导致东亚冬季风加强，朝鲜半岛和日本西部的冬季变冷，中国南部的降水减少。在温暖异常和近海风力减弱的情况下，鄂霍茨克海冰范围缩小。减弱的 AUSM 会导致相同的异常，但极性相反。我们的观测数据分析和数值实验表明，类似 WP 的异常是由 NAUS 延伸到北半球副热带急流的异常高空发散风产生的静止罗斯贝波的传播激发的。气候哈德利环流在此过程中至关重要。东亚上空随之而来的异常非绝热加热和太平洋风暴路径上瞬态涡流的反馈强迫进一步放大了类似WP的响应。
Anomalous convective activity in the Tropics forced by sea surface temperature (SST) variability exerts significant remote influence that provides a basis for seasonal prediction in the extratropics. In austral summer convective activity exhibits pronounced interannual variability over northern Australia (NAUS), which is, however, unlikely forced by SST anomalies but essentially a manifestation of internal variability of the Australian summer monsoon (AUSM) system. Based on observational data, the present study reveals its significant remote impacts on the wintertime climate in East Asia and the western North Pacific. The anomalous AUSM excites the Western Pacific (WP) pattern, as confirmed through an atmospheric general circulation model experiment. Through this cross-equatorial teleconnection, the enhanced AUSM leads to the strengthening of the East Asian winter monsoon with a colder winter over the Korean Peninsula and western Japan and reduced precipitation over southern China. The Okhotsk sea-ice extent decreases under warm anomalies and weakened offshore winds. The weakened AUSM leads to the same anomalies but with the opposite polarities. Our observational data analysis and numerical experiments reveal that the WP-like anomalies are excited by the propagation of stationary Rossby waves generated by anomalous upper-level divergent wind from NAUS that extends into the Northern Hemisphere subtropical jet. The climatological Hadley circulation is essential in this process. The concomitant anomalous diabatic heating over East Asia and feedback forcing by transient eddies along the Pacific stormtrack act to further amplify the WP-like response.