Orographic Influences on Lake-Effect Storms

University Of Utah, Salt Lake City UT

Investigators

Abstract

The Ontario Winter (OW) Lake-effect Systems (LeS) field campaign will involve multiple university and non-profit organizational groups who week to better understand mechanisms controlling the timing and location of heavy snowfall and associated cloud structures over and around the U.S. Great Lakes region. Observational assets to be deployed during OWLeS include the University of Wyoming King Air, the CSWR Doppler on Wheels mobile radars, multiple sounding systems, the Millersville University Profiling System, the UAH Mobile Integrated Profiling System, and a variety of other surface in-situ instruments. The focus of this particular research team's activities is on the intersection of LeS and influences of higher terrain, e.g. as represented by the Tug Hill Plateau region of upstate New York. They will make use of climatological analysis, field research, real-data numerical modeling and idealized large-eddy simulations to address two overarching questions related to LeS: 1) How does the interplay between environmental conditions, cloud processes, lake shape and size, and terrain scale and geometry affect orographic precipitation enhancement during lake-effect storms?; and 2) Under what conditions does orography modify the morphology of LeS and the generation, distribution, and intensity of precipitation over surrounding lowland areas? The main regions of study will be areas around the Great Salt Lake and the Tug Hill Plateau downwind of Lake Ontario. This team plans to contribute two snow observation stations and a deployable rawinsounding system to OWLeS field effort. The intellectual merit of this effort is centered on evaluation of the following three main hypotheses: 1) The height of the capping inversion or stable layer relative to the downstream barrier crest regulates orographic precipitation enhancement and the lowland to mountain precipitation ratio; 2) Ice particle growth and fallout from the lake-effect system and boundary layer turbulence are important contributors to orographic precipitation in unblocked lake-effect events; and 3) Large lake-land temperature contrasts and associated land-breeze convergence yield lake-dominated events, whereas terrain-dominated events occur during periods with weaker lake-land temperature contrasts. Broader impacts of the project will include the participation of undergraduate students in data collection, education and training of two graduate students, one of which is drawn from an underrepresented group in atmospheric sciences, and various outreach activities. This research has the potential to contribute to improved prediction of lake-effect heavy snow storm events, which would in turn support both societal and economic benefits.