During the Hydrological cycle in the Mediterranean Experiment (HyMeX) in autumn 2012 intensive measurements were conducted in the Tavignano Valley, which extends from the centre to the coast of the island of Corsica. On the investigated day, the atmospheric boundary layer (ABL) in the valley showed a distinctive spatio-temporal variability, which resulted from the interaction and superposition of mesoscale dynamically- and thermally-driven processes and dry convection. Based on the observations, not all of the observed ABL characteristics could be explained and hypotheses on the involved processes were formulated in a previous study. To close the observational gaps and to test the hypotheses, high-resolution simulations with the COSMO (Consortium for Small-scale Modeling) model were now performed. The model was able to reproduce the main ABL characteristics and could hence be used to address the processes affecting the ABL. The main features were: in the upper part of the valley, the stable nocturnal ABL was eroded from top and bottom alike by shear-generated turbulent mixing in the vicinity of a mountain wave and buoyancy- and shear-driven surface-based turbulent mixing, leading to a very abrupt increase of the daytime ABL depth. In the lower part of the valley, the ABL remained rather shallow and was dominated by a superimposed thermally-driven sea breeze and upvalley wind. In the afternoon, the formerly deep ABL in the upper part of the valley rapidly decreased when the combined sea breeze and upvalley wind moved up the valley. While the ABL depth was rather horizontally homogeneous in the lower part of the valley and near the coast, it showed a considerable variability in the valley's upper part on scales of a few kilometres due to the varying dominance of the different processes. The local ABL depth also varied considerably in time depending on which influence dominated, i.e. of surface heating, mountain wave or sea breeze and upvalley wind. As the simulated sea breeze strongly depended on the sea-surface temperature, the results were sensitive to the chosen value in the model.

中文翻译：

---

山波冲击下边界层时空结构

在 2012 年秋季地中海实验 (HyMeX) 的水文循环期间，在从科西嘉岛中心延伸到海岸的塔维尼亚诺山谷进行了密集测量。在调查当天，山谷中的大气边界层（ABL）表现出独特的时空变化，这是中尺度动力和热驱动过程以及干对流相互作用和叠加的结果。根据观察，并非所有观察到的 ABL 特征都可以解释，并且在先前的研究中制定了有关相关过程的假设。为了缩小观测差距并检验假设，现在使用 COSMO（小规模建模联盟）模型进行了高分辨率模拟。该模型能够重现主要的 ABL 特征，因此可用于解决影响 ABL 的过程。主要特征是：在山谷的上部，稳定的夜间 ABL 被山波附近剪切产生的湍流混合和浮力和剪切驱动的基于表面的湍流混合从顶部和底部侵蚀，导致白天 ABL 深度的急剧增加。在山谷的下部，ABL 仍然相当浅，并以叠加的热驱动海风和上谷风为主。下午，随着海风和谷上风的联合向上移动，谷上部原深的ABL迅速下降。虽然山谷下部和海岸附近的 ABL 深度在水平方向上相当均匀，由于不同过程的主导地位不同，它在几公里的尺度上显示了山谷上部的相当大的变化。局部 ABL 深度也随时间变化很大，这取决于哪种影响占主导地位，即地表加热、山波或海风和山谷风。由于模拟海风强烈依赖于海面温度，因此结果对模型中选择的值很敏感。