Effects of Surface Wetness and Snow Cover on Frontal Evolution and Precipitation

了解当地和区域物理强迫对锋面系统的影响对于改善与这些锋面有关的天气预报非常重要。根据该合同，首席研究员将评估地表强迫对美国中部冷锋和降水演变的影响，研究重点将集中在春夏期间地表湿度对冷锋结构和降水的影响，以及冬春后期积雪的影响。该项目将利用观察到的案例研究为三维模拟提供基础，以评估地表条件变化对热力学和动力学过程的影响。通过对锋生条件和其他参数的诊断，将评估锋面结构和降水变化的机制。在锋面环境中，地表条件对条件对称不稳定性的影响也将被研究。利用观察到的条件作为对照实验，首席研究员将进行数值模型敏感性模拟，以评估变化的地表特征对锋面和降水的影响。虽然先前的研究已经评估了具体的案例或进行了理想化的二维敏感性研究，但利用现实世界的案例和三维建模来评估正面对地表条件的响应在研究文献中很少受到关注。这项研究的完成将提高对地表-大气相互作用对冷锋和降水影响的认识。

Understanding the impact of local and regional phyical forcing on frontal systems is important to improving prediction of the weather associated with these fronts. Under this award, the Principal Investigator will evaluate the impact of surface forcing on the evolution of cold fronts and precipitation over the central U.S. The research will focus on the influence of surface wetness on cold frontal structure and precipitation during spring-summer, and the influence of snow cover during late winter-spring. The project will use observed case studies to provide a basis for three-dimensional simulations that will evaluate the modification of thermodynamical and dynamical processes by changes in surface conditions. Mechanisms responsible for modifications in the frontal structure and precipitation will be evaluated through diagnosis of frontogenesis terms and other parameters. The impact of surface conditions on conditional symmetric instability in the frontal environment also will be examined. Using the observed conditions as control experiments, the Principal Investigator will perform numerical model sensitivity simulations to assess the impacts of altered surface characteristics on fronts and precipitation for a representative sample of cases. Although prior studies have evaluated specific cases or have performed idealized two-dimensional sensitivity studies, evaluations of frontal response to surface conditions using real-world cases and three-dimensional modeling have received little attention in the research literature. Accomplishment of the research will improve understanding of the effects of surface-atmosphere interactions on cold fronts and precipitation.