Long-lived mesoscale convective systems over eastern South Africa
Long-lived mesoscale convective systems over eastern South Africa
复制标题
南非东部长寿命中尺度对流系统
DOI：
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
C. Reason
中科院分区：
文献类型：
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作者：
D. M. Morake;R. Blamey;C. Reason
本文介绍了1985-2008年南方夏季（9 - 4月）期间南非东部大型、长寿命中尺度对流系统的气候学。夏季平均发生63次mcs，但频率有相当大的年际变化。该系统主要发生在11月至3月之间，12月为高峰。MCS活动的季节性周期与有利的CAPE和垂直切变剖面一致。大多数系统倾向于沿东部悬崖和北部阿古拉斯流的邻近温暖水域发生，具有夜间生命周期。通常，开始于下午早些时候，MCS状态达到下午三点左右，最大程度在晚上早些时候，并在午夜左右或之后不久终止。研究发现，大多数mcs在陆地上启动，但在海洋上启动的系统往往比在陆地上发展的系统持续时间更长。大陆和海洋MCSs的季节周期存在差异，海洋系统存在两个季节内高峰（12月和4月）。南环模（SAM）与初夏MCSs频率存在较强的正相关。在夏末，MCSs的频率似乎与Mascarene高压和莫桑比克海峡槽的强度有关，它们调节了南非东部的水汽流入和该地区低层大气的稳定性。
A climatology of large, long-lived mesoscale convective systems (MCSs) over eastern South Africa for the extended austral summer (September-April) from 1985-2008 is presented. On average, 63 MCSs occur here in summer, but with considerable interannual variability in frequency. The systems mainly occur between November and March, with a December peak. This seasonal cycle in MCS activity is shown to coincide with favorable CAPE and vertical shear profiles across the domain. Most systems tend to occur along the eastern escarpment and adjacent warm waters of the northern Agulhas Current with a nocturnal life cycle. Typically, initiation begins in the early afternoon, MCS status is reached mid-afternoon, maximum extent early in the night and termination around midnight or shortly thereafter. It is found that most MCSs initiate over land, but systems that initiate over the ocean tend to last longer than those that develop over land. The results also show that there are differences in the seasonal cycle between continental and oceanic MCSs, with oceanic systems containing two intraseasonal peaks (December and April). There is a relatively strong positive relationship between the Southern Annular Mode (SAM) and early summer MCSs frequency. For the late summer, the frequency of MCSs appears related to the strength of the Mascarene High and Mozambique Channel Trough which modulate the inflow of moisture into eastern South Africa and the stability of the lower atmosphere over the region.