To study the influence of convective momentum transport (CMT) on wind, boundary layer and cloud evolution in a marine cold air outbreak (CAO) we use large‐eddy simulations subject to different baroclinicity (wind shear) but similar surface forcing. The simulated domain is large enough,  km²), to develop typical mesoscale cellular convective structures. We find that a maximum friction induced by momentum transport (MT) locates in the cloud layer for an increase of geostrophic wind with height (forward shear, FW) and near the surface for a decrease of wind with height (backward shear, BW). Although the total MT always acts as a friction, the interaction of friction‐induced cross‐isobaric flow with the Coriolis force can develop supergeostrophic winds near the surface (FW) or in the cloud layer (BW). The contribution of convection to MT is evaluated by decomposing the momentum flux by column water vapor and eddy size, revealing that CMT acts to accelerate subcloud layer winds under FW shear and that mesoscale circulations contribute significantly to MT for this horizontal resolution (250 m), even if small‐scale eddies are nonnegligible and likely more important as resolution increases. Under FW shear, a deeper boundary layer and faster cloud transition are simulated, because MT acts to increase surface fluxes and wind shear enhances turbulent mixing across cloud tops. Our results show that the coupling between winds and convection is crucial for a range of problems, from CAO lifetime and cloud transitions to ocean heat loss and near‐surface wind variability.

中文翻译：

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对流动量传输和垂直风切变对冷空气爆发演变的影响

为了研究对流动量输运（CMT）对海洋冷空气暴发（CAO）中风，边界层和云的演变的影响，我们使用了大涡模拟，其受不同斜压（风切变）但具有相似的表面强迫作用。模拟域足够大， km ²），以开发典型的中尺度细胞对流结构。我们发现，由动量传输（MT）引起的最大摩擦力位于云层中，随着高度（正向剪切力，FW）的增加，地转风增大；而随着高度的减小（向后剪切力，BW）的减小，地表风附近的摩擦增大。尽管总MT始终是摩擦，但摩擦诱导的等压横流与科里奥利力的相互作用会在地表（FW）或云层（BW）附近形成超地转风。对流对MT的贡献是通过用柱水蒸气和涡流大小分解动量通量来评估的，揭示了CMT在FW剪切作用下起到加速亚云层风的作用，并且在这种水平分辨率（250 m）下，中尺度循环对MT的贡献很大，即使小规模的涡旋不可忽略，并且随着分辨率的提高可能更重要。在FW剪切作用下，模拟了更深的边界层和更快的云层过渡，因为MT起到增加表面通量的作用，而风切变作用则增强了整个云层顶部的湍流混合。我们的结果表明，风与对流之间的耦合对于一系列问题至关重要，从CAO寿命和云过渡到海洋热损失和近地表风的可变性。