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<p>In October 2023, northern China experienced a record-breaking extreme high temperature event (EHTE), with monthly mean surface air temperature (SAT) 3℃ above normal, posing a grand threat to crop production and ecological environment. The primary driver of the EHTE was an anomalous large-scale barotropic high-pressure (anticyclone) centered over Lake Baikal. The lower to middle levels northerlies over the southeastern flank of the anomalous anticyclone suppressed air moisture and cloud cover over northern China, which increased downward shortwave radiation and consequently elevated SAT in the region. A comparison of global circulation and sea surface temperature (SST) anomalies in October 2023 with historical anomalies associated with SAT over northern China during 1979–2022 suggests that abnormal North Atlantic tripole (NAT) SST anomalies and the Indo-Pacific zonal SST gradient (IPG) were potential origins of the record-breaking EHTE. Further observations and numerical simulations demonstrated both the NAT and IPG triggered downstream- and poleward-propagating Rossby wave trains. These wave trains contributed to the formation of the anomalous high-pressure over Lake Baikal, leading to reduced cloudiness and elevated SAT over northern China. A physical-based prediction model, utilizing the precursors from the two oceanic origins, outperformed two dynamical models with lead times from zero to three months. It successfully predicted the record-breaking EHTE in 2023, a feat that the dynamical models failed to achieve.</p>

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Two oceanic origins for the record-breaking extreme high temperature event over northern China in October 2023

  • 期刊论文

  • 发表日期：

    2025年3月25日

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  • Hongjie Huang,
  • Zhiwei Zhu,
  • Qianrong Ma,
  • Shujuan Hu,
  • Lijuan Wang

摘要

In October 2023, northern China experienced a record-breaking extreme high temperature event (EHTE), with monthly mean surface air temperature (SAT) 3℃ above normal, posing a grand threat to crop production and ecological environment. The primary driver of the EHTE was an anomalous large-scale barotropic high-pressure (anticyclone) centered over Lake Baikal. The lower to middle levels northerlies over the southeastern flank of the anomalous anticyclone suppressed air moisture and cloud cover over northern China, which increased downward shortwave radiation and consequently elevated SAT in the region. A comparison of global circulation and sea surface temperature (SST) anomalies in October 2023 with historical anomalies associated with SAT over northern China during 1979–2022 suggests that abnormal North Atlantic tripole (NAT) SST anomalies and the Indo-Pacific zonal SST gradient (IPG) were potential origins of the record-breaking EHTE. Further observations and numerical simulations demonstrated both the NAT and IPG triggered downstream- and poleward-propagating Rossby wave trains. These wave trains contributed to the formation of the anomalous high-pressure over Lake Baikal, leading to reduced cloudiness and elevated SAT over northern China. A physical-based prediction model, utilizing the precursors from the two oceanic origins, outperformed two dynamical models with lead times from zero to three months. It successfully predicted the record-breaking EHTE in 2023, a feat that the dynamical models failed to achieve.