Nocturnal boundary-layer phenomena in regions of complex topography are extremely diverse and respond to a multiplicity of forcing factors, acting primarily at the mesoscale and microscale. The interaction between different physical processes, e.g., drainage promoted by near-surface cooling and ambient flow over topography in a statically stable environment, may give rise to special flow patterns, uncommon over flat terrain. Here we present a climatography of boundary-layer flows, based on a 2-year archive of simulations from a high-resolution operational mesoscale weather modelling system, 4DWX. The geographical context is Dugway Proving Ground, in north-western Utah, USA, target area of the field campaigns of the MATERHORN (Mountain Terrain Atmospheric Modeling and Observations Program) project. The comparison between model fields and available observations in 2012–2014 shows that the 4DWX model system provides a realistic representation of wind speed and direction in the area, at least in an average sense. Regions displaying strong spatial gradients in the field variables, thought to be responsible for enhanced nocturnal mixing, are typically located in transition areas from mountain sidewalls to adjacent plains. A key dynamical process in this respect is the separation of dynamically accelerated downslope flows from the surface.

中文翻译：

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基于中尺度模式的犹他州西北部复杂地形夜间边界层特征的气候学

复杂地形区域的夜间边界层现象极其多样，对多种强迫因素有反应，主要作用于中尺度和微观尺度。不同物理过程之间的相互作用，例如在静态稳定环境中由近地表冷却和周围流过地形促进的排水，可能会产生特殊的流动模式，这在平坦地形上并不常见。在这里，我们根据高分辨率操作中尺度天气建模系统 4DWX 的 2 年模拟存档，展示了边界层流的气候学。地理环境是美国犹他州西北部的 Dugway 试验场，是 MATERHORN（山地地形大气建模和观测计划）项目实地活动的目标区域。模型场与 2012-2014 年可用观测值之间的比较表明，4DWX 模型系统至少在平均意义上提供了该地区风速和风向的真实表示。在场变量中显示出强烈空间梯度的区域，被认为是增强夜间混合的原因，通常位于从山侧壁到相邻平原的过渡区域。在这方面的一个关键动态过程是将动态加速的下坡流与地表分离。通常位于从山壁到相邻平原的过渡区。在这方面的一个关键动态过程是将动态加速的下坡流与地表分离。通常位于从山壁到相邻平原的过渡区。在这方面的一个关键动态过程是将动态加速的下坡流与地表分离。