The South Atlantic convergence zone: Intensity, form, persistence, and relationships with intraseasonal to interannual activity and extreme rainfall
The South Atlantic convergence zone: Intensity, form, persistence, and relationships with intraseasonal to interannual activity and extreme rainfall
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DOI：
10.1175/1520-0442(2004)017
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发表时间：
2004-01-01
影响因子：
4.9
通讯作者：
Liebmann, B
中科院分区：
文献类型：
--
作者：
Carvalho, LMV;Jones, C;Liebmann, B
本文研究了南大西洋辐合带（SACZ）在南半球夏季的强度、地理位置和持续性特征。强度和空间特征的SACZ进行因子分析的结构特性的出射长波辐射（OLR）数据确定。前两个主导因素解释了65%的结构特性的总方差，并根据强度和位置（海洋与大陆）来表征SACZ。一个指数的基础上构建的因素得分的大小，以确定激烈（弱）和海洋（大陆）SACZ。强烈的SACZ类别与负OLR异常在热带南美洲的大面积，从亚马逊西部延伸到大西洋。在南美洲热带地区OLR正异常和南美洲东南部OLR负异常的情况下，观察到弱SACZ类。SACZ的海洋和大陆方面与中纬度波列模式有关。Madden-Julian振荡（MJO）调制持续时间超过3天的强烈SACZ事件。持续事件的年际变化表明，海洋与大陆SACZ的比例及其频率取决于厄尔尼诺-南方涛动（ENSO）的相位。发生在巴西的极端降雨的变化在SACZ和MJO的背景下进行了讨论。强（弱）SACZ增加（减少）95 th日降雨百分位数在巴西中东部相比，气候。海洋（大陆）SACZ增加（减少）95日降雨百分位在巴西东南部。MJO阶段的特点是抑制印尼和增强在太平洋中部的对流活动增加了第95个日降雨百分位在巴西东北部北部，而相反的功能观察到的MJO阶段的特点是增强印尼和抑制在太平洋中部的对流。
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 longwave radiation (OLR) data. The first two leading factors explain 65% of the total variance of structural properties 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. The 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. The weak SACZ category 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 midlatitude wave train pattern. The Madden - Julian oscillation (MJO) modulates intense SACZ events with persistence longer than 3 days. Interannual variability of persistent events indicates that the ratio of oceanic to continental SACZ as well as their frequency depends on the phase of El Nino-Southern Oscillation (ENSO). Occurrence of extreme rainfall in Brazil is discussed in the context of variations in the SACZ and MJO. Intense ( weak) SACZ increases ( decreases) the 95th daily rainfall percentile over central-eastern Brazil compared to the climatology. Oceanic ( continental) SACZ increases ( decreases) the 95th daily rainfall percentile over southeastern Brazil. The MJO phase characterized by suppression of convective activity over Indonesia and enhancement over the central Pacific increases the 95th daily rainfall percentile over north-northeastern Brazil, whereas opposite features are observed for the phase of the MJO characterized by the enhancement of convection over Indonesia and suppression over the central Pacific.