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タカヤ コウタロウ
TAKAYA KOTARO
高谷 康太郎 所属 京都産業大学 理学部 宇宙物理・気象学科 職種 教授 |
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| 言語種別 | 英語 |
| 発行・発表の年月 | 2014/12 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | An Isentropic Analysis of the Temporal Evolution of East Asian Cold Air Outbreaks |
| 執筆形態 | その他 |
| 掲載誌名 | JOURNAL OF CLIMATE |
| 出版社・発行元 | AMER METEOROLOGICAL SOC |
| 巻・号・頁 | 27(24),pp.9337-9348 |
| 著者・共著者 | Takamichi Shoji,Yuki Kanno,Toshiki Iwasaki,Koutarou Takaya |
| 概要 | The equatorward cold airmass flux below potential temperature theta(T) = 280K across 45 degrees N integrated from 90 degrees E to 180 degrees is used as an index to quantitatively measure cold air outbreaks (CAOs) in the East Asian winter monsoon. Intermittent CAOs over East Asia significantly contribute to the global equatorward cold airmass flux. An autocorrelation analysis indicates that CAO events persist for approximately 5 days. The geographical distributions of lagged correlations/regressions with the CAO index (CAOI) clarify the temporal evolution of synoptic conditions associated with CAOs. The developing Siberian high located northwest of Lake Baikal (65 degrees N, 100 degrees E) on day -4 slowly moves southeastward, reaches maximum intensity over Siberia (50 degrees N, 110 degrees E) on day 0, and then decays while moving rapidly southward. By contrast, the Aleutian low is almost stagnant and maintains a strong intensity. The eastward pressure gradient geostrophically induces the equatorward cold airmass flux. After day -2, the cold air mass significantly decreases over Siberia, but increases over East Asia and the western North Pacific Ocean. The cold air mass continues to migrate southward while spreading eastward, and disappears mainly over the ocean. The leading edge of the high pressure anomaly moves southward at 13 ms(-1) and reaches the equator simultaneously with the equatorward wind anomaly on about day 14. An additional analysis of separating the equatorward flux into 90 degrees-135 degrees E and 135 degrees E-180 degrees suggests that CAOs are, to some extent, caused by the Siberian high and the Aleutian low acting separately. |
| DOI | 10.1175/JCLI-D-14-00307.1 |
| ISSN | 0894-8755/1520-0442 |