Recent changes in the South America low-level jet
Recent changes in the South America low-level jet
复制标题
南美低空急流近期变化
DOI：
10.1038/s41612-019-0077-5
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发表时间：
2019
影响因子：
9
通讯作者：
Charles Jones
中科院分区：
文献类型：
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作者：
Charles Jones
南美低空急流(SALLJ)是一种气候学特征，对南美洲降水的时空分布起着至关重要的作用。虽然以前的研究侧重于安第斯山脉中部(即秘鲁东南部、玻利维亚和巴拉圭)的小范围低空急流的机制和变异性，但在安第斯山脉北部东部山坡(即秘鲁、哥伦比亚和委内瑞拉东北部)出现的低空急流及其与中部区域的联系以前从未被探索过。研究表明，9-2月期间，北部支流的小尺度低空急流超过10 m S−1，频率可达中部地区。此外，小岛屿发展中国家可以同时发生，也可以分别发生在两个区域。当小范围低空急流仅在北部分支活动时，从玻利维亚到南美洲东南部的风速很低，从气候学来看，降水量显著减少(1-4 mm Day−1)。相比之下，玻利维亚东部的降水量增加了2-4 mm day−1。合成结果表明，随着北大西洋副热带高压的增强，在安第斯山脉北部上空推动东北风的大尺度环流模式迫使玻利维亚北部支流增加。进一步的分析表明，在过去的39年里，安第斯山脉北部的SALLJ的频率和强度大大增加。大气科学：在安第斯山脉北部上空有明显的低空急流南美低空急流(SALLJ)在决定南美降水模式方面起着关键作用。此前的研究主要集中在安第斯山脉中部上空的低空急流。美国加州大学圣巴巴拉分校的查尔斯·琼斯表示，SALLJ的北部分支在委内瑞拉、哥伦比亚和秘鲁东北部形成，其频率与安第斯山脉中部的低空急流相似，但垂直风速分布不同，气候风特征明显，季节变化较大。当SALLJ在北部地区活跃时，玻利维亚东部安第斯山坡的降水量增加，但南美洲东南部的降水量减少。低层低空急流北支的形成与热带东太平洋的对流抑制和海面温度降低有关。对SALLJ的这种更好的理解可以帮助全球气候模型，这些模型传统上难以代表南美洲东南部的降水。
The South America Low-level Jet (SALLJ) is a climatological feature with a critical role in the spatiotemporal distribution of precipitation in South America. While previous studies have focused on the mechanisms and variability of the SALLJ in the central Andes (i.e., southeast Peru, Bolivia, and Paraguay), the occurrence of the low-level jet in the eastern slopes of the northern Andes (i.e., northeast Peru, Colombia, and Venezuela) and its linkages to the central region have not been previously explored. This study shows that the SALLJ in the northern branch exceeds 10 m s−1 during September–February and the frequency can be as high as in the central region. Moreover, the SALLJ can occur simultaneously or separately in both regions. When the SALLJ is active only in the northern branch, wind speeds are very low from Bolivia towards southeast South America (SESA) and precipitation is significantly reduced (1–4 mm day−1) from climatology. In contrast, precipitation increases over eastern Bolivia by 2–4 mm day−1. Composites suggest that the SALLJ northern branch is forced by a large-scale circulation pattern with the enhancement of the North Atlantic Subtropical High driving northeasterly winds over the northern Andes. Further analysis shows that the frequency and intensity of the SALLJ in the northern Andes has substantially increased in the last 39 years.Atmospheric science: Distinct low-level jet over northern AndesThe South American low-level jet (SALLJ) plays a key role in determining South American precipitation patterns. Previous research has focused primarily on the low-level jet over the central Andes. Charles Jones of the University of California, Santa Barbara, USA shows that a northern branch of SALLJ forms over Venezuela, Colombia and northeast Peru with similar frequency to the low-level jet in the central Andes, but with differing vertical wind speed profiles, distinct climatological wind features and larger seasonal variations. When SALLJ is active in the northern region, precipitation is enhanced in Bolivia on the eastern Andes slopes, but decreases over southeastern South America. The formation of the northern branch of the SALLJ is associated with suppressed convection and cold sea surface temperature in the tropical eastern Pacific. This improved understanding of SALLJ can aid global climate models that have traditionally struggled to represent precipitation over southeastern South America.