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<p>Cold blobs are colder-than-normal seawaters persistently over the mid-latitude Northeast Pacific (NEP). As the sea surface temperature anomaly (SSTA) during cold season exhibits the largest variability in November, this study selects 17 blob-like cold events in the NEP based on the criteria that the SSTA averaged over the area (160°&#xa0;W–135°&#xa0;W, 40°&#xa0;N–50°&#xa0;N) in November falls below − 1.0 standard deviation. Previous literature reported that an anomalous low-pressure system to the north of the cold blobs plays a predominant role in forming and maintaining the cold blobs. We further reveal the barotropic structure of this anomalous low-pressure system, which is linked to a circumglobal Rossby wave train. Furthermore, the Rossby wave train, generated by anomalous rainfall in the mid-latitude (North Atlantic and Arabian Peninsula) and tropical (Arabian Sea, western-central equatorial Pacific, and south of the Indochinese Peninsula) regions, can transport wave energy to the NEP and thus contribute to maintaining the anomalous low-pressure system. The Linear Baroclinic Model experiments reasonably reproduce the low-pressure anomalies over the NEP, further confirming the above sources in triggering the teleconnections. Our findings can potentially increase the predictability for the atmospheric circulation anomalies and the blob-like cold SSTA events over the NEP.</p>

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Teleconnections and drivers of Northeast Pacific blob-like cooling in November

  • 期刊论文

  • 发表日期：

    2025年4月7日

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  • Jian Shi,
  • Yichuan Lu,
  • Jiajie Chen,
  • Zhongxian Li

摘要

Cold blobs are colder-than-normal seawaters persistently over the mid-latitude Northeast Pacific (NEP). As the sea surface temperature anomaly (SSTA) during cold season exhibits the largest variability in November, this study selects 17 blob-like cold events in the NEP based on the criteria that the SSTA averaged over the area (160° W–135° W, 40° N–50° N) in November falls below − 1.0 standard deviation. Previous literature reported that an anomalous low-pressure system to the north of the cold blobs plays a predominant role in forming and maintaining the cold blobs. We further reveal the barotropic structure of this anomalous low-pressure system, which is linked to a circumglobal Rossby wave train. Furthermore, the Rossby wave train, generated by anomalous rainfall in the mid-latitude (North Atlantic and Arabian Peninsula) and tropical (Arabian Sea, western-central equatorial Pacific, and south of the Indochinese Peninsula) regions, can transport wave energy to the NEP and thus contribute to maintaining the anomalous low-pressure system. The Linear Baroclinic Model experiments reasonably reproduce the low-pressure anomalies over the NEP, further confirming the above sources in triggering the teleconnections. Our findings can potentially increase the predictability for the atmospheric circulation anomalies and the blob-like cold SSTA events over the NEP.