著者

Masatake E. Hori Kazuhiro Oshima

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.14, pp.69-73, 2018 (Released:2018-06-26)

参考文献数

15

被引用文献数

3

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We use two groups of 100-member ensemble AGCM experiment to investigate the robustness and probabilistic nature of the Warm Arctic/Cold Eurasian (WACE) pattern with or without strong warming SST trend and sea-ice reduction. Model ensembles successfully simulate a distribution of trend coefficients close to that of observation. Results show that the recent trend in WACE pattern is driven by the warming of the Arctic SST, but the pattern itself is not amplified between the warming and non-warming experiment and cannot explain the current cooling trend of the mid-latitudes. We argue that the difference in sea-ice condition regulates the more extreme cases of the pattern thereby contributing to the positive trend in WACE pattern similar to that of observation.

著者

Masatake E. Hori Jun Inoue Takashi Kikuchi Meiji Honda Yoshihiro Tachibana

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.7, pp.25-28, 2011 (Released:2011-02-10)

参考文献数

12

被引用文献数

16 36

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In the winter of 2009/2010, Japan and the East Asian region experienced a frequent occurrence of cold air outbreaks. Although the winter average temperature in the Japan main islands was slightly positive (+0.81°C for DJF average and +0.71°C for NDJFM average), repeated decline in temperature was notable throughout the season. One explanation for this abnormal winter season is the extremely negative condition of the Arctic Oscillation (AO) that persisted from December to mid-January. However, AO alone does not provide sufficient explanation for the cold air outbreak during November or its intraseasonal periodicity. A case study of the cold air outbreak that reached Japan on Dec. 18 reveals an anomalous ridge forming over the Barents-Kara Sea, which leads to the cold air accumulation over western Siberia. The pressure anomaly subsequently shifted westward to mature into a blocking high which created a wave-train pattern downstream, advecting the cold air eastward towards East Asia and Japan. The sequence of events was also apparent in multiple cases throughout the season. This study suggests that there is a strong and systematic linkage in the intraseasonal timescale between the atmospheric condition over the Barents-Kara Sea and the cold air accumulation over the Eurasian continent, leading to the anomalous cold air outbreak over East Asia and Japan. The mechanism may also provide explanation to extreme winter conditions such as those observed during the winter of 2010/2011.