The flow and moisture fluxes associated with ridging South Atlantic Ocean anticyclones during the subtropical southern African summer
The flow and moisture fluxes associated with ridging South Atlantic Ocean anticyclones during the subtropical southern African summer
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非洲南部副热带夏季与南大西洋反气旋脊相关的流量和水分通量
DOI：
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
H. Chikoore
中科院分区：
文献类型：
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作者：
T. Ndarana;Siyabonga Mpati;Mary;F. Engelbrecht;H. Chikoore
本研究利用 38 年的 ERA-中期重新分析，研究了南非上空的南大西洋反气旋脊引起的水流和相关的水分通量。流量和水分通量分为地转分量和地转分量。综合分析表明，脊高压系统是由罗斯贝波列调制的，罗斯贝波列在南美洲附近的中纬度地区和格林威治子午线附近的南大西洋上游发展。波列与热带温带槽 (TTT) 相关的波列类似，几乎所有 TTT 后都会发生脊化，而 20% 的脊化事件与 TTT 相关。综合分析还表明，影响南非的脊引起的水汽通量源自脊高演化过程中不同时间的周围海洋的不同区域。在早期阶段，水分通过地转过程从邻近海岸的水分散度区域沿东南海岸进入该国，并且大部分保持在南纬 30° 线以南。陆地上的水分通量遵循东海岸的几何形状，呈东北方向。这些地转通量导致莱索托和斯威士兰之间地区的山脊过程中出现降雨。南部非洲夏季降雨日数中约 60% 与起脊事件有关，而 TTT 则约占夏季降雨日数的 21%。在脊演化的后期阶段，地转通量进入莫桑比克南部地区，并导致该地区的水分积累。相关的水汽发散区域总是位于其地转对应区域之前，局部最大值最终在莫桑比克海峡形成。
Using 38 years of ERA‐Interim reanalyses, this study examines the flow and associated moisture fluxes induced by ridging South Atlantic Ocean anticyclones over South Africa. The flow and moisture fluxes are divided into their geostrophic and ageostrophic components. Composite analysis reveals that ridging high pressure systems are modulated by Rossby wave trains that develop upstream in the middle latitudes near South America and the South Atlantic Ocean near the Greenwich Meridian. The wave trains are similar to those that are associated with tropical temperate troughs (TTTs) and nearly all TTTs are followed by ridging, whilst 20% of the ridging events are linked to TTTs. Composite analysis also shows that ridging‐induced moisture fluxes affecting South Africa originate from different areas of the surrounding oceans at different times during the evolution of ridging highs. In the early stages, moisture enters the country along the southeastern coast through ageostrophic processes from a moisture divergence region located adjacent to the coast and remains largely south of 30°S latitude line. The moisture fluxes have a northeastern orientation on land, following the geometry of the eastern coast. These ageostrophic fluxes contribute to the occurrence of rainfall during the ridging process in the region located between Lesotho and Swaziland. Ridging events are associated with about 60% of rainfall days in summer over southern Africa whilst TTTs contribute about 21% summer rainfall days. During the later stages of the evolution of ridging, geostrophic fluxes enter the southern parts of Mozambique and contribute the accumulation of moisture in that region. The associated moisture divergence region is always located ahead of its ageostrophic counterpart, with a local maximum eventually forming in the Mozambique Channel.
南非开普省西南部初冬降雨变化背后的机制
影响因子：
4.6
作者：
Mahlalela P
通讯作者：
Mahlalela P
莫桑比克海峡槽的变化及其对东南非降雨量的影响
影响因子：
4.9
作者：
Barimalala R
通讯作者：
Barimalala R