open access

https://hdl.handle.net/2115/20452

Low frequent variability of the Siberian high and East Asian winter monsoon

日本語

2007-03-23

北海道大学低温科学研究所

Low Temperature Science

65

31-42

1章 10年～100年スケールの気候変動の観測, 気候復元とモニタリング

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.

紀要論文

Version of Record

1880-7593

AA12122962