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

Iowa State University, Ames IA

Investigators

Abstract

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.