The late spring Caribbean rain‐belt: climatology and dynamics
The late spring Caribbean rain‐belt: climatology and dynamics
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晚春加勒比雨带：气候学和动力学
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
B. Mapes
中科院分区：
文献类型：
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作者：
T. Allen;B. Mapes
本研究考察了加勒比地区晚春降雨（早期雨季，ERS）的动态，希望确定系统低频气候调制的基于机制的预测因子。随着季节性变暖的进行，亚热带加勒比雨带在5月发展。到了7月，雨带明显地随着西风带及其强烈的天气扰动向北撤退。每日气候学数据表明加勒比ERS的物理定义为5月中旬至6月中下旬。基于对几个季节的日循环的检查，我们假设降雨在具有足够高（高于45-50 mm）可降水量（PW）的空气舌中准随机发生。这些潮湿的空气团被低层南风从热带深处带到北方，并通常被西风带的纬向切变弯曲成西南-东北带。输送PW舌的低层气流部分是由西风带的高层天气扰动引起的，但也涉及地理上固定的巴拿马低压周围的温和持续气流。虽然强迫上升有时在这些高层槽之前活跃，但对流和中尺度过程可以在PW足够的地方产生降雨。总之，我们假设降雨主要取决于湿空气舌的拉格朗日统计。比较了加勒比雨带和东亚对应的梅雨带，并讨论了文献中的其他机制和诊断。根据机械选择的预测因素进行统计预测，既可以检验假设，又可以帮助该区域的地方农业利益。
This study examines the dynamics of late spring rainfall (the Early Rainy Season, ERS) in the Caribbean region, in hopes of identifying mechanistic‐based predictors for low‐frequency climate modulations of the system. The subtropical Caribbean rain‐belt develops in May as seasonal warming proceeds. By July, the rain‐belt retreats north apparently following the westerlies and their vigorous synoptic disturbances. Daily climatology data suggest a physical definition of the Caribbean ERS as mid‐May to mid‐late June. Based on an examination of daily loops for several seasons, we hypothesize that rainfall occurs quasi‐randomly throughout tongues of air with sufficiently high (above 45–50 mm) precipitable water (PW). These moist airmasses are brought north from the deep tropics by low‐level southerlies, and typically bent over into SW‐NE bands by latitudinal shear of the westerlies. The low‐level flow that transports PW tongues is partly induced by upper‐level synoptic disturbances in the westerlies, but also involves the gentle persistent flow around a geographically anchored Panama Low. While forced ascent is sometimes active ahead of these upper‐level troughs, convective and mesoscale processes can produce rain wherever PW is sufficient. In summary, we hypothesize that rainfall hinges largely on the Lagrangian statistics of moist air tongues. Comparison is drawn between the Caribbean rain‐belt and its East Asian counterpart (Meiyu‐Baiu), and other mechanisms and diagnostics from that literature are discussed. Statistical prediction exercises, based on mechanistically chosen predictors, could both test hypotheses and aid local agricultural interests in the region.