LARGE, SYNOPTIC AND MESO SCALE VARIATIONS OF THE BAIU FRONT, DURING JULY 1982 .3. SPACE-TIME SCALE AND STRUCTURE OF FRONTAL DISTURBANCES

被引：22

作者：

AKIYAMA, T

机构：

[1] Meteorological Research Institute, Tsukuba

来源：

JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN | 1990年 / 68卷 / 06期

关键词：

D O I：

10.2151/jmsj1965.68.6_705

中图分类号：

P4 [大气科学（气象学）];

学科分类号：

0706 ; 070601 ;

摘要：

Part I of this study examined the large-scale situations and cloud variations of the Baiu front during July 1982, and showed that the large-scale increases of baroclinicity around the front and the low-level southerly wind toward the front contributed to the increase of cloud amounts in the frontal zone (the active phase). The regional difference in the cloud variations of mesoscale periods was also described. In Part II, the vertical structure of the Baiu front, features of disturbances in/around the Baiu frontal zone were studied for the six 5-day subperiods of July 1982, based on the relative vorticity fields. The results showed that during the active phases the Baiu frontal mesoscale disturbances tend to develop at approximately 120-degrees-E, under the influence of the disturbances in the upper westerly jet. In Part III, the space-time scale and structure of the disturbances in/around the Baiu front are examined by spectral analysis mainly on the relative vorticity fields. The interaction between the disturbances in the Baiu front and in the upper westerly jet is also examined. The results of Part III are summarized as follows. From spectral analysis, the disturbances of a synoptic-scale (approximately 6-day) and three mesoscale (approximately 3.5-, approximately 2.5-, 1-day) periods are found in/around the Baiu front. These disturbances developed through interaction between them, and showed a complicated evolution process. Many shallow-weak vortices were generated around the Quinghai-Xizang Plateau with 1-day period. Some of them in the Baiu front (30-degrees-N approximately 40-degrees-N) propagated east along the low-level Baiu jet (B-jet) and began to develop into the long-lived mesoscale disturbances around the east coast (approximately 120-degrees-E) of the continent. In the period when a synoptic-scale disturbance in the upper westerly jet (W-jet; in 40-degrees-N approximately 50-degrees-N) developed around 120-degrees-E (the active-shallow Baiu front), the aforementioned weak vortices developed into the Baiu frontal shallow mesoscale (approximately 2.5-day period) disturbances, making pairs with the deep mesoscale (approximately 2.5-day period) disturbances propagated from the west in the W-jet. Some of the shallow and the deep mesoscale disturbances developed as subsystems of one synoptic-scale disturbance. In the period when the Baiu front east of approximately 120-degrees-E showed a baroclinic structure (the active-deep Baiu front), the aforementioned shallow-weak vortices in the B-jet developed into the Baiu frontal deep mesoscale disturbances with a period of approximately 3.5 days, coupling with the upper-level mesoscale (approximately 3.5-day period) disturbances propagated from Central Asia in the W-jet. Although the period, vertical structure and evolution process of these mesoscale frontal disturbances differed from each other in accordance with the large-scale and/or synoptic-scale frontal situations, they caused the cloud variations of mesoscale periods in the frontal zone.

引用

页码：705 / 727

页数：23

共 20 条

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