与2003年梅雨期西太副高东西向运动有关的热带上空东风带扰动的结构和演变特征
STRUCTURAL AND EVOLUTION CHARACTERISTICS OF THE EASTERLIES VORTEX OVER THE TROPICAL REGION RELATING TO THE EAST-WEST SHIFT OF THE SUBTROPICAL ANTICYCLONE OVER THE WESTERN PACIFIC OCEAN IN THE MEIYU PERIOD 2003
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摘要: 利用NCEP/NCAR 1 000~10 hPa 2.5°×2.5°的再分析资料,分析了与西太平洋副热带高压(简称西太副高)东西进退相关系的热带对流层上空东风带扰动(简称EV)的结构和演变特征。结果表明:西太副高与其南侧的东风带扰动存在同时西进的过程,当西太副高南、北两侧的东、西风带上的扰动在相向运动中抵达同一经度上时,西太副高出现异常东退。热带对流层上空东风带扰动为中高层天气系统,它从对流层中层伸展到50 hPa高度附近,在200 hPa上表现得最为明显,在热力场上表现出"上暖强下冷弱"的垂直分布特征;在西太副高东退时,东风带扰动东西侧的辐散效应和垂直运动的性质发生了显著变化,东风带扰动中心附近的垂直速度场出现从上升运动到向下下沉运动转化的过程。Abstract: By employing the NCEP/NCAR reanalysis data sets(1 000~10 hPa,2.5 °×2.5 °),the characteristics of structure and evolution of the easterlies vortex(shortened as EV) over the tropical upper troposphere relating to the east-west direction shift of the subtropical anticyclone over the Western Pacific Ocean(shortened as WPSA) are analyzed in this paper.It is shown that there exists a shift westward synchronously between WPSA and the EV locating in the south of the WPSA.And the WPSA retreats eastward anomalously while the EV and the westerly vortex encountering around the same longitude as they move from the opposite directions.The EV is the upper weather system,extending from mid-troposphere to the height of 50 hPa with the center locating on 200 hPa.The vertical thermal distribution illustrates the characteristics of being "warmer in the upper layer and colder in the lower layer".The divergence effect and the vertical motion change largely within the east and west sides of the EV.And the ascending branch transforms to a descending branch near the center of the EV.
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