We investigate the synoptic precursors to the Harmattan wind and dust frontogenesis during the high impact Saharan dust outbreak over the Cape Verde Islands on 13 November 2017. We employ multiscale observations and the Weather Research and Forecasting model Coupled with Chemistry simulations. The analyses indicate that the dust storm was initiated on the lee side of the Saharan Atlas Mountains (SAM) in Algeria on 10 November 2017. This dust storm was associated with a double Rossby wave break linked through nonlinear wave reflection. Two successive Rossby wave breaks contributed to the wave amplification over the Eastern North Atlantic Ocean which transported large magnitude potential vorticity air into the North African continent. The resulting coupled pressure surge was associated with cold air advected equatorward over the SAM which organized the strong near‐surface wind that ablated the dust. The simulation results indicate that the dust front was initially related to a density current‐like cold front which formed due to the downslope transport of cold airflow over the SAM and then triggered undular bores on the lee side. Each bore perturbed the dust loading and then the subsequent diurnal heating generated differential planetary boundary layer turbulence kinetic energy strengthening the dust frontogenesis. Dust became confined behind the cold surge and interacted with the daytime Saharan planetary boundary layer leading to increased dust loading, while the dust front propagated equatorward. Two distinct dust plumes arrived successively at low levels at Mindelo, Cape Verde Islands: (1) from the coasts of Mauritania and Senegal and (2) from the SAM southern flank.

中文翻译：

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罗斯比海浪爆发之前佛得角群岛明德洛撒哈拉尘暴的大气动力学：多尺度观测分析和模拟

我们在2017年11月13日对佛得角群岛发生的高冲击撒哈拉沙尘暴爆发期间，调查了Harmattan风沙尘暴前兆的天气前兆。我们采用多尺度观测以及天气研究和预报模型与化学模拟相结合。分析表明，沙尘暴始于2017年11月10日在阿尔及利亚撒哈拉阿特拉斯山脉（SAM）的后风侧。该沙尘暴与通过非线性波反射引起的双重Rossby波折断有关。两次连续的Rossby海浪中断导致北大西洋东部海浪放大，从而将大量潜在的涡旋空气输送到北非大陆。由此产生的耦合压力激增与冷空气在赤道上方平流到赤道仪上有关，后者组织了强烈的近地表风，从而消除了灰尘。模拟结果表明，尘埃前沿最初与像密度流一样的冷锋有关，该冷锋是由于冷气流在SAM上的向下坡度传输而形成的，然后在背风侧触发了成孔的孔洞。每个孔都扰动了粉尘负荷，随后的昼夜加热产生了不同的行星边界层湍流动能，从而增强了粉尘的产生。尘埃被限制在冷潮之后，并与白天的撒哈拉行星边界层相互作用，导致尘埃负荷增加，而尘埃前沿则向赤道传播。两条明显的尘埃流依次低空到达明德洛，