Event Attribution of 2017/18 Cold Winter in Central Eurasia: Insights on Model Bias Effects

DOI Web Site 38 References
  • Mori Masato
    Research Institute for Applied Mechanics, Kyushu University
  • Imada Yukiko
    Atmosphere and Ocean Research Institute, The University of Tokyo
  • Shiogama Hideo
    Earth System Division, National Institute for Environmental Studies
  • Kosaka Yu
    Research Center for Advanced Science and Technology, The University of Tokyo
  • Takahashi Chiharu
    Atmosphere and Ocean Research Institute, The University of Tokyo
  • Arai Miki
    Atmosphere and Ocean Research Institute, The University of Tokyo
  • Kamae Youichi
    Institute of Life and Environmental Sciences, University of Tsukuba
  • Hasegawa Akira
    Atmosphere and Ocean Research Institute, The University of Tokyo
  • Watanabe Masahiro
    Atmosphere and Ocean Research Institute, The University of Tokyo
  • Tokinaga Hiroki
    Research Institute for Applied Mechanics, Kyushu University

Description

<p>In 2017/18 winter, the Siberian High intensified significantly, leading to a severe cold winter in central Eurasia. Here, we apply the event attribution methods using two types of historical large-ensemble simulations from an atmospheric general circulation model to quantify the influence of human activities on this event. The 2017/18 winter was dominated by a circulation regime known as the Warm-Arctic Cold-Eurasia (WACE) pattern, and both observation and model showed high WACE indices. However, the models exhibited a bias characterized by weak magnitudes of the cold Eurasian anomalies associated with the WACE, attributed to an underrepresentation of externally driven components. Anthropogenic climate change has increased the probability of the positive WACE regime year by year, significantly enhancing its occurrence in the 2017/18 winter. However, influences of this modulation of WACE occurrence did not significantly alter the probability of cold events in central Eurasia due to the model bias characterized by the muted cold lobe associated with the WACE. While a simple bias correction resolved this issue, it was demonstrated that the presence or absence of such corrections led to vastly different attribution results. Elucidating the mechanisms behind the WACE and accurately representing them in models is essential for more reliable attribution.</p>

Journal

  • SOLA

    SOLA 21 (0), 117-123, 2025

    Meteorological Society of Japan

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