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>A Lagrangian Identification of the Main Sources of Moisture Affecting Northeastern Brazil during Its Pre-Rainy and Rainy Seasons
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A Lagrangian Identification of the Main Sources of Moisture Affecting Northeastern Brazil during Its Pre-Rainy and Rainy Seasons
This work examines the sources of moisture affecting the semi-arid Brazilian Northeast (NEB) during its pre-rainy and rainy season (JFMAM) through a Lagrangian diagnosis method. The FLEXPART model identifies the humidity contributions to the moisture budget over a region through the continuous computation of changes in the specific humidity along back or forward trajectories up to 10 days period. The numerical experiments were done for the period that spans between 2000 and 2004 and results were aggregated on a monthly basis. Results show that besides a minor local recycling component, the vast majority of moisture reaching NEB area is originated in the south Atlantic basin and that the nearby wet Amazon basin bears almost no impact. Moreover, although the maximum precipitation in the “Poligono das Secas” region (PS) occurs in March and the maximum precipitation associated with air parcels emanating from the South Atlantic towards PS is observed along January to March, the highest moisture contribution from this oceanic region occurs slightly later (April). A dynamical analysis suggests that the maximum precipitation observed in the PS sector does not coincide with the maximum moisture supply probably due to the combined effect of the Walker and Hadley cells in inhibiting the rising motions over the region in the months following April.
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机译：这项工作通过拉格朗日诊断方法检查了半干旱巴西东北部（NEB）在雨前和雨季（JFMAM）期间的水分来源。 FLEXPART模型通过连续计算沿长达10天的后退或前进轨迹的特定湿度变化来确定某个区域中湿度对湿度预算的贡献。在2000年到2004年之间进行了数值实验，并每月汇总结果。结果表明，除了少量的本地回收成分外，到达NEB地区的绝大部分水分都起源于南大西洋盆地，附近的亚马逊湿盆地几乎没有影响。此外，尽管“ Poligono das Secas”地区（PS）的最大降水发生在3月，并且从南大西洋到PS的空气包裹相关的最大降水在1月至3月观察到，但是该海洋区域的水分贡献最大发生的时间稍晚一些（4月）。动力学分析表明，在PS部门观测到的最大降水量与最大水分供应量不一致，这可能是由于Walker和Hadley细胞在四月之后的几个月内抑制了该地区上升运动的综合作用。
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