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シベリア高気圧の活動とその長周期の変動について
高谷, 康太郎;中村, 尚
Permalink : http://hdl.handle.net/2115/20452
Abstract
シベリア高気圧の季節内長周期変動及び年々変動の力学を明らかにする。シベリア高気圧の季節内変動の増幅過程には、ブロッキング高気圧の形成が対流圏上層に見られ、それらは2つの典型的なタイプに類別される。両タイプとも、シベリア高気圧の増幅には、対流圏上層のブロッキングを伴う循環偏差と、シベリア高気圧に伴う地表付近の循環偏差との相互作用が重要であることが渦位反転法によって示される。年々変動に関しても、対流圏上層にはやはり2つの典型的な循環変動のパターンが観測されること、さらにそれらの循環変動が惑星波活動の変調として解釈できることが示される。
The Siberian high is a cold, semi-permanent surface anticyclone residing over the Asian continent in winter. The high is known as one of the crucial factors for wintertime climate over the Fat East and Northwestern Pacific, as it influences the strength of the East Asian winter monsoon. Intraseasonal amplification events of the surface Siberian high in winter are generally associated with blocking ridge formation in the upper troposphere. Composite analysis applied to the 20 strongest intraseasonal events over Siberia on the basis of the circulation data observed over the 40 recent years reveals that the blocking formation differs fundamentally between the east and west of the climatological upper-level trough over the Far East. To the west, what may be called "wave-train (Atlantic-origin) type" is common, white what may be called "Pacific-origin type" dominates to the east of the trough. Regardless of a particular type of blocking formation in the upper troposphere, a cold-air outbreak tends to occur once anomalously cold air reaches the northeastern slope of the Tibetan Plateau. We have shown through "potential vorticity (PV) inversion" technique that an interaction of the upper-level height anomalies with surface temperature anomalies is essential for amplification of the Siberian high of the both types. Interannual variability of the East Asian winter monsoon has also been examined. Two distinct height anomaly patterns in the upper troposphere associated with the interannual variability are found; that is, wavetrain pattern and WP-like patterns. Both types can be interpreted as modulations of activities of planetary waves. The difference of the planetary wave formation from early winter to midwinter is apparent between cold and warm winter in the mid-latitude East Asia.
The Siberian high is a cold, semi-permanent surface anticyclone residing over the Asian continent in winter. The high is known as one of the crucial factors for wintertime climate over the Fat East and Northwestern Pacific, as it influences the strength of the East Asian winter monsoon. Intraseasonal amplification events of the surface Siberian high in winter are generally associated with blocking ridge formation in the upper troposphere. Composite analysis applied to the 20 strongest intraseasonal events over Siberia on the basis of the circulation data observed over the 40 recent years reveals that the blocking formation differs fundamentally between the east and west of the climatological upper-level trough over the Far East. To the west, what may be called "wave-train (Atlantic-origin) type" is common, white what may be called "Pacific-origin type" dominates to the east of the trough. Regardless of a particular type of blocking formation in the upper troposphere, a cold-air outbreak tends to occur once anomalously cold air reaches the northeastern slope of the Tibetan Plateau. We have shown through "potential vorticity (PV) inversion" technique that an interaction of the upper-level height anomalies with surface temperature anomalies is essential for amplification of the Siberian high of the both types. Interannual variability of the East Asian winter monsoon has also been examined. Two distinct height anomaly patterns in the upper troposphere associated with the interannual variability are found; that is, wavetrain pattern and WP-like patterns. Both types can be interpreted as modulations of activities of planetary waves. The difference of the planetary wave formation from early winter to midwinter is apparent between cold and warm winter in the mid-latitude East Asia.
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