Orographic Forcing of the Coastal Atmospheric Boundary Layer

9526138 Rogers沿海山脉对风场形成屏障，可能同时影响当地气流的上游和下游演变。海岸带产生的局部高压或低压会被困住并沿海岸线传播。持续2到6天的高能扰动特别令人感兴趣。这些特征会使沿海地区的局部天气发生重大变化，例如，晴朗的天空被云和雾所取代，并引起风场的增强和逆转。这些系统都有很好的记录，但没有研究描述它们的动力结构、起源、与平均边界层的相互作用以及伴随这些事件的云顶层的发展。与海岸屏障相关的气流加速引起沿海海洋的强风强迫和低层气流速度的快速变化。这些地形强迫流对海洋和大气之间的热量、水分、动量和微量成分的交换有重要影响。由于这些流动受到地形的限制，它们通常是静止的和持久的，持续影响海岸线的特定区域。虽然这些特征的基本结构是已知的，但它们只在少数情况下被记录下来，并且没有专门针对确定这些特征的动力学及其与热环流的相互作用的系统研究，热环流也是夏季加利福尼亚沿海地区的重要中尺度特征。这项工作将侧重于利用飞机和地面测量对边界层沿岸和跨岸结构进行现场测量。飞机仪器将提供沿海大气的平均和湍流结构的直接测量，同时提供海洋边界层反演变形的激光雷达测量和沿海云和气溶胶的现场云微物理测量。一个重要的结果将是能够解析支配加利福尼亚海岸部分地区中尺度风场变化的时间和空间尺度，这可能对复杂地形的中尺度预报和数值模拟产生重大影响。＊＊＊

9526138 Rogers Coastal mountains form a barrier to the wind field that may affect both the downstream and upstream evolution of the local air flow. Local regions of high or low pressure generated by the coastal zone can become trapped and propagate along the coastline. Energetic, disturbances that exist for between two and six days are of particular interest. These features can cause significant changes in the local weather in the coastal zone, for example, replacing clear skies with clouds and fog, and causing intensification and reversals of the wind field. These systems are well documented, but no studies have characterized their dynamical structure, origin, interaction with the mean boundary layer and the development of the cloud-capped layer that accompanies these events. Accelerations of the flow associated with coastal barriers give rise to strong wind forcing of the coastal ocean and rapid variations in the speed of the low level air flow. These orographically-forced flows have a significant effect on the exchange of heat, moisture, momentum and trace constituents between the ocean and the atmosphere. Since these flows are constrained by the topography, they are often stationary and persistent, consistently affecting a particular area of the coastline. While the basic structure of these features is known, they have been documented on only a few occasions and no systematic study has been directed specifically to identifying the dynamics of these features and their interactions with the thermal circulation that is also a significant mesoscale feature of the summer-time California coastal zone. This work will focus on in situ measurements of the along shore and across shore structure of the boundary layer using aircraft and surface based measurements. Aircraft instruments will provide direct measurements of the mean and turbulent structure of the coastal atmosphere with coincident lidar measurements of the deformation of the marine bounda ry layer inversion and in situ cloud microphysical measurements of coastal clouds and aerosols. An important result will be the ability to resolve the temporal and spatial scales that dominate the variability of the mesoscale wind field along parts of the California coast, which may have a significant impact of mesoscale forecasting and numerical modeling in complex terrain. ***