ABSTRACT: Mesoscale convective complexes (MCCs) are meteorological events that result in severe storms, hail, flood, and tornadoes, but they are difficult to forecast. In South America (SA), MCCs are usually larger and last longer than those in the USA. Southern Brazil (SB) is one of their preferred regions of occurrence. This study’s objective was to contribute to the identification of the main physical characteristics and atmospheric environment that favors the occurrence of MCCs in SB and determine how these events are unique relative to other subtropical SA (OSSA) regions. Results indicate that SB MCCs last longer (+3 h) and their average maximum extent is at least 50000 km² larger than OSSA MCCs. The atmospheric environment of SB MCCs meets the criteria already indicated in previous studies, with the northerly low-level jet (LLJ), which brings humidity from the Amazon Basin to the SB MCCs genesis area, coupling with the upper-level jet (ULJ). Moreover, SB MCCs have the South Atlantic as their second source of moisture, which is advected by anticyclonic circulation in the southwestern South Atlantic. This indicates that SB MCCs have unique characteristics compared to OSSA MCCs, including 2 main atmospheric circulation systems responsible for moisture advection to the SB genesis region. For comparison, OSSA MCCs are more dependent on the South Atlantic Convergence Zone (SACZ) and the advection of moisture by the LLJ from the Amazon Basin to north-central Argentina and west-central and southeast Brazil.

中文翻译：

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有利于巴西南部中尺度对流复合体发展的大气特征

摘要：中尺度对流复合体（MCC）是导致严重风暴，冰雹，洪水和龙卷风的气象事件，但很难预测。在南美（SA），MCC通常比美国的更大且寿命更长。巴西南部（SB）是他们偏爱的发生地之一。这项研究的目的是有助于识别有利于SB中MCC发生的主要物理特征和大气环境，并确定这些事件相对于其他亚热带SA（OSSA）地区如何独特。结果表明，SB MCC持续时间更长（+3小时），其平均最大范围至少为50000 km ²比OSSA MCC大。SB MCC的大气环境符合先前研究中已经表明的标准，北低空急流（LLJ）将湿度从亚马逊河盆地带入SB MCC的发生区域，再加上高空急流（ULJ） 。此外，SB MCCs以南大西洋为第二湿源，这是由于西南大西洋西南部的反气旋环流所致。这表明与OSSA MCC相比，SB MCC具有独特的特征，包括2个主要的大气循环系统，负责将水分平流到SB成因区。为了进行比较，OSSA MCC更加依赖南大西洋收敛带（SACZ）以及LLJ从亚马逊盆地到阿根廷中北部和巴西中西部和东南部对流。