Cold Fog Amongst Complex Terrain (CFACT)

该项目名为“复杂地形中的冷雾”（CFACT），目的是调查山谷中冷雾的形成。雾由悬浮在地球表面或附近空气中的微小水滴或冰晶组成，被认为是一种低云。雾在高海拔复杂地形中形成的频率与水体一样高，但了解得较少。由于其对能见度的影响，雾是与天气有关的航空事故的第二大常见原因，仅次于强风事件。雾的预报对人类活动、交通、空气质量、人类健康和农业有着重要的影响。尽管雾的影响和历史雾的研究，雾的预测仍然是一个挑战，天气预报，因为复杂的相互作用之间的土地，水和大气条件的雾形成。雾的形成、发展和消散是研究的重点，而雾的预报能力差反映了对雾的形成、发展和消散缺乏了解。这项研究预计将有助于改善山区雾预报，提高公众对雾天气条件的认识，并为决策提供信息。CFACT项目的总体目标是：1）利用最新的观测技术研究复杂地形下冷雾的发展和环境条件; 2）改进数值天气预报（NWP）模式中的微物理参数化和能见度算法; 3）利用数值天气预报（NWP）模式中的微物理参数化和能见度算法;以及3）开发用于当前和下一代的数据同化和分析方法（例如，亚公里尺度）NWP模型。该实地项目将于2022年1月和2月在犹他州的希伯谷进行，部署地面原位仪器和遥感平台网络，以获得热力学剖面，云微物理，气溶胶的物理和化学特性以及环境动力学的全面测量。将使用具有各种物理参数化和耦合陆-气资料同化能力的天气研究和预报（WRF）模式，以促进利用数值预报模式改进雾预报的研究。预计这些努力将导致：1）改善对复杂地形中冷雾过程的理解，2）评估影响与能见度预测相关的冷雾微物理学的体成核条件，3）识别与异质复杂地形中冷雾生命周期相关的微观到天气尺度运动学和热力学过程的知识缺口，4）理解物理之间的相互作用（例如，颗粒生长、成核、冷凝、辐射）和动态机制（例如，湍流、垂直空气速度和波动），5）评估陆面条件，特别是地面积雪，如何影响近地表和边界层大气过程，包括冷雾形成和演变中地表辐射平衡的关键作用，6）微尺度数值预报向中尺度数值预报的改进-该奖项反映了美国国家科学基金会的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查进行评估的支持的搜索.

The project, Cold Fog Amongst Complex Terrain (CFACT), is to investigate cold fog formation in mountain valleys. Fog consists of tiny water droplets or ice crystals suspended in the air at or near the Earth’s surface and is considered as a type of low-lying cloud. Fog forms in high-elevation complex terrain as frequently as over water bodies but is less understood. Because of its impacts on visibility, fog is the second most common cause of weather-related aviation accidents after strong wind events. Fog forecasts have significant impacts on human activities, transportation, air quality, human health, and agriculture. Despite the impacts of fog and historical fog research, fog prediction remains a challenge for weather prediction because of complex interactions between land, water, and atmospheric conditions in fog formation. Poor fog forecasting skills reflect a lack of understanding of fog formation, development, and dissipation, which is the focus of the research. This study is expected to contribute to improving fog forecasting in mountainous regions, enhancing public awareness of fog-weather conditions, and information for decision-making. The project involves the participation of multiple institutions nationally and internationally with graduate and undergraduate training in both classrooms and the field.The overarching goals of the CFACT project are to 1) investigate cold fog development and environment conditions in complex terrain with latest observation technology, 2) improve microphysical parameterizations and visibility algorithms used in numerical weather prediction (NWP) models, and 3) develop data-assimilation and analysis methods for current and next-generation (e.g., sub-kilometer scale) NWP models. The field project will be conducted in Heber Valley, Utah, during January and February 2022 with deployment of a network of ground-based in-situ instruments and remote sensing platforms to obtain comprehensive measurements of thermodynamic profiling, cloud microphysics, physical and chemical properties of aerosols, and dynamics of the environment. The Weather Research and Forecasting (WRF) model with various physical parameterizations and coupled land-atmosphere data assimilation capabilities will be used to facilitate the studies for improved fog prediction with NWP models. It is anticipated that the efforts will result in 1) improved understanding of cold-fog processes in complex terrain, 2) an evaluation of the bulk nucleation conditions that affect cold-fog microphysics related to visibility prediction, 3) identification of knowledge gaps in the micro- to synoptic- scale kinematic and thermodynamic processes associated with cold-fog life cycles in heterogeneous complex terrain, 4) understanding of interactions between physical (e.g., particle growth, nucleation, condensation, radiation) and dynamic mechanisms (e.g., turbulence, vertical air velocities, and wave motions) during the lifecycle of a fog event, 5) an evaluation of how land-surface conditions, especially snow on the ground, affect near-surface and boundary-layer atmospheric processes including the critical role of the surface radiative balance in cold-fog formation and evolution, and 6) improvement of microscales to mesoscales NWP-model simulations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.