Effects of Blocking Anticyclones in Eurasia in the Rainy Season (Meiyu/Baiu Season)
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- Wang Yafei
- Institute of Geoscience University of Tsukuba
Bibliographic Information
- Other Title
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- ユーラシアのブロッキング高気圧の華中や日本の梅雨に対する影響
Abstract
Distribution of BAs in Eurasia during the Meiyu/Baiu season and some possible influences of BAs on the behavior of the MB frontal zone were examined through statistical analyses. Then detailed analyses were made for a case in late June 1982.<br>BAs appear with higher frequency in the regions of 31-60°E, 91-110°E and 131-150°E in the latitudes of 50-70°N. The maximum frequency is frond in the region of 131-150°E.<br>The appearance frequency of BAs in region of 50-70°N/81-120°E (Region B) showed a positive significant correlation with the persistency of the Baiu period in Japan. On the other hand, the appearance frequency of BAs in the region of 50-70°N/121-160°E (Region C) showed a positive correlation with both the persistency of the Meiyu period and the rainfall amount during that period in Central China.<br>A statistical analysis suggests that the existence of cold air in the lower layer in 32.5-35°N/112.5-117.5°E (corresponding to the area just to the north of the Meiyu front), largely associated with a BA in Region C, is an important factor in activating the Meiyu front in Central China, and in enhancing the lowlevel southerly wind component in South China. A case study for June 1982 showed that the cold air intrusion toward Central China in the situation of Type C occurs mainly in the lower layer, and is accompanied by the development of a baroclinic instability wave around 50°N/100-110°E. The formation of the Type C situation is a favorable condition for cold air coming southward to the Meiyu frontal zone.<br>On the other hand, there was a Rossby wave-like (height) anomaly pattern propagating from the Okhotsk Sea to the tropics through Japan shown by the presence of a BA in Region C in June. Although forcing processes have not been clarified yet, a case study in late June 1982 suggests that the wave was amplified around the Lake Baikal to the Okhotsk Sea area. The propagation might result in a negative anomaly of geopotential height at 500 mb level to the east of Japan, a southward shift of the Baiu front and weakening (or southward shift of) the sub-tropical high in nearby regions. The present paper shows the different effects of the Type C stiuation on climatological features of the Meiyu front from those of the Baiu front.
Journal
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- Journal of the Meteorological Society of Japan. Ser. II
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Journal of the Meteorological Society of Japan. Ser. II 70 (5), 929-951, 1992
Meteorological Society of Japan
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Details 詳細情報について
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- CRID
- 1390282681481657088
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- NII Article ID
- 130007345720
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- ISSN
- 21869057
- 00261165
- http://id.crossref.org/issn/00261165
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- Data Source
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- JaLC
- Crossref
- CiNii Articles
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- Abstract License Flag
- Disallowed