The South Atlantic Convergence Zone: intensity, form, persistence, relationships
The South Atlantic Convergence Zone: intensity, form, persistence, relationships
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南大西洋辐合区：强度、形式、持久性、关系
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
B. Liebmann
中科院分区：
文献类型：
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作者：
Leila M. V. Carvalho;B. Liebmann
研究了南部夏季南大西洋辐合带的强度、地理位置和持续性特征。通过对输出长波辐射（OLR）数据的结构特性进行因子分析，确定了SACZ的强度和空间特征。前两个主要因素解释了对流活动总方差的65%，并根据强度和位置（海洋与大陆）表征了SACZ。根据因子得分的大小构建了一个指数来识别强/弱和海洋/大陆的SACZ。强烈的SACZ类别与南美洲热带大片地区（从亚马逊西部延伸到大西洋）的负OLR异常有关。弱SACZ在南美洲热带为正OLR异常，在南美洲东南部为负OLR异常。SACZ的海洋和大陆方面与中纬度波列模式有关。麦登-朱利安振荡（MJO）调节强烈的SACZ事件，持续时间大于3天。持续强/弱事件的年际变率研究表明，强/弱SACZ的比值取决于El Niño/南方涛动（ENSO）的相位。在SACZ、MJO和ENSO变化的背景下讨论了巴西极端降雨的发生。强（弱）SACZ与巴西中部（南部和西北部）极端降水的高频率有关。大洋SACZ增加了巴西东南部极端事件的频率，而大陆SACZ则没有明显的信号。以抑制印度尼西亚上空对流活动和增强中太平洋上空为特征的MJO相增加了巴西东部极端降雨的频率。La Niña （El Niño）事件与巴西东部-东北部（南部）极端事件的高频率有关，对半干旱地区有重要影响。
The characteristics of intensity, geographical location and persistence of the South Atlantic convergence zone (SACZ) during the austral summer are investigated. Intensity and spatial features of the SACZ are identified by performing a factor analysis of structural properties of outgoing long-wave radiation (OLR) data. The first two leading factors explain 65% of the total variance of convective activity and characterize the SACZ according to intensity and location (oceanic versus continental). An index is constructed based on the magnitude of the factor scores to identify intense/weak and oceanic/continental SACZ. Intense SACZ category is associated with negative OLR anomalies over a large area of tropical South America, extending from the western Amazon to the Atlantic Ocean. Weak SACZ is observed with positive OLR anomalies over tropical South America and negative OLR anomalies over southeastern South America. Oceanic and continental aspects of the SACZ are related to a mid-latitude wave train pattern. Madden-Julian Oscillation (MJO) modulates intense SACZ events with persistence greater than 3 days. Investigation of interannual variability of persistent intense/weak events indicates that the ratio of intense to weak SACZ depends on the phase of El Niño/Southern Oscillation (ENSO). Occurrence of extreme rainfall in Brazil is discussed in the context of variations in the SACZ, MJO and ENSO. Intense (weak) SACZ are related to high frequency of extreme precipitation over central (southern and northwestern) Brazil. Oceanic SACZ increases the frequency of extremes over southeastern Brazil whereas continental has no clear signal. The MJO phase characterized by suppression of convective activity over Indonesia and enhancement over central Pacific increases the frequency of extreme rainfall over eastern Brazil. La Niña (El Niño) episodes are linked to high frequency of extremes over eastern-northeastern (southern) Brazil with important impact on the semi-arid region.