Variability in the characteristics of cut‐off low pressure systems over subtropical southern Africa
Variability in the characteristics of cut‐off low pressure systems over subtropical southern Africa
复制标题
南部非洲副热带地区截止低压系统特征的变化
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
C. Reason
中科院分区：
文献类型：
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作者：
A. Singleton;C. Reason
对1973-2002年期间非洲南部亚热带上空截止低压系统特征的变化进行了研究。这些特征包括其季节性、频率、持续时间、位置和规模。研究发现，非洲南部每年平均有11个截止低气压出现在20°S以南，最常见的是在3月至5月的季节。讨论了非洲南部截止低压的数量与厄尔尼诺南方涛动（ENSO）、南美洲太平洋型、3号波型和半年振荡（SAO）之间的潜在关系。拉尼娜年似乎与高于平均年频率的截止低点有关，但厄尔尼诺年的情况通常并非如此。20世纪80年代，截止低点的首选季节从3月至5月转变为6月至8月，这与SAO的减弱和纬向波数3的转变相吻合。这一时期也表明，这些系统的首选位置发生了变化，从西南亚热带南部非洲到该地区的东北部。结果表明，在非洲南部副热带上空的截止低压，南半球的波数3型和SAO之间可能有关系。版权所有© 2006年皇家气象学会。
Variability in the characteristics of cut‐off low pressure systems over subtropical southern Africa is examined for the 1973–2002 period. These characteristics include their seasonality, frequency, duration, location and size. It is found that on average 11 cut‐off lows occur over southern Africa south of 20°S per year and are most common in the March‐May season. Potential relationships between the number of cut‐off lows over southern Africa with the El Niño Southern Oscillation (ENSO), the Pacific South America pattern, the wave number 3 pattern and the semi‐annual oscillation (SAO) are discussed. La Niña years appear to be associated with above average annual frequencies of cut‐off lows but the reverse is generally not true for El Niño years. There was a shift in the preferred season for cut‐off lows from March–May to June–August in the 1980s, which coincided with a weakening of the SAO and a shift in zonal wave number 3. This period also showed a change in the preferred location of these systems from southwestern subtropical southern Africa to the northeast of the region. The results suggest that there may be a relationship between cut‐off lows over subtropical southern Africa, the wave number 3 pattern in the Southern Hemisphere and the SAO. Copyright © 2006 Royal Meteorological Society.