Cut-off low pressure systems over southern Australia: climatology and case study
Cut-off low pressure systems over southern Australia: climatology and case study
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DOI：
10.1002/(sici)1097-0088(199912)19:15
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发表时间：
1999-12
期刊：
影响因子：
--
通讯作者：
L. Qi;L. Leslie;Shuyun Zhao
中科院分区：
文献类型：
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作者：
L. Qi;L. Leslie;Shuyun Zhao
切断低压系统是影响澳大利亚南部最重要的天气系统之一。它们可以在大面积地区带来中到大雨，因此对澳大利亚农业极为重要。这项研究有两个组成部分。首先，对14年（1983-1996）的存档数据进行统计分析，以产生气候学。气候学的重点是澳大利亚南部截止低气压的频率、持续时间和路径（位置和移动）。第二个是对1997年8月下旬的截止低压的个案研究，其中突出了截止低压的显著特征。气候学结果表明：5 - 10月期间，南澳大利亚的截止低压出现频率最高;西南部地区是南澳大利亚截止低压发生最活跃的地区;绝大多数截止低压要么向东移动，要么向东南移动。该案例研究旨在揭示一个特定的“经典”截止低点的形成和结构的细节。结果表明，对流层中上部存在较强的斜压性，有利于低压的加强。天气学分析还表明，降水的水汽供应是由热带海洋（珊瑚海）通过低空急流（LLJ）输送到高纬度地区，形成一个狭窄的湿舌，与切断低压及其相关的冷锋相互作用。截止低压位于高空急流（ULJ）的右前象限，这是低层系统发展的有利位置。版权所有© 1999年皇家气象学会
Cut-off low-pressure systems are among the most important weather systems that affect southern Australia. They can bring moderate to heavy rainfall over large areas and as such are extremely important to the Australian agricultural industry. There are two components of this study. First, a statistical analysis is carried out on 14 years of archived data (1983–1996) to produce a climatology. The emphasis in the climatology is on the frequency, duration and tracks (location and movement) of cut-off lows in southern Australia. Second is a case study of the cut-off low of late August 1997, in which the distinctive features of cut-off lows are highlighted. The results from the climatology reveal the following: there is a maximum in the frequency of cut-off lows in southern Australia during May–October; the most active area for the genesis of cut-off lows in southern Australia is the southwestern region; and the vast majority of cut-off lows move either eastward or southeastward. The case study is aimed at revealing details of the formation and structure of one particular ‘classical’ example of a cut-off low. It is found that there is strong baroclinicity in the mid-upper troposphere, favourable for the intensification of the low. The synoptic analysis also shows that the moisture supply for the precipitation was transported from the tropical ocean (the Coral Sea) to higher latitude regions by a low level jet (LLJ), forming a narrow moist tongue which interacted with the cut-off low and its associated cold front. The cut-off low was located at the right-front quadrant of an upper level jet (ULJ), which is a favourable position for low system development. Copyright © 1999 Royal Meteorological Society