Using Idealized Large-Eddy Simulations to Understand the Impact of Downstream Terrain on Lake-Effect Snowfall

Lake-effect storms over Lake Ontario and the Sea of Japan are frequently impacted by terrain where they produce prolific climatological snowfall maxima. 700 cm of annual snowfall is observed over the Tug Hill Plateau, which rises 500 m downstream of Lake Ontario, while mean annual snowfall of more than 1700 cm is observed over the mountains of northwest Japan, which rise to 1500 m downstream of the Sea of Japan. The impact of downstream terrain on lake-effect snowfall distribution is poorly understood due to the influence complex coastal geometry, upstream terrain, and boundary layer circulations on lake-effect storms. In this study, we seek to isolate and determine the impact of downstream terrain on lake-effect precipitation using idealized large-eddy simulations. Simulations are run with 100- to 200-m horizontal grid spacings using Cloud Model 1 (CM1) and consist of a simplified lake and downstream mountain, such that boundary layer circulations are resolved and complexities affecting lake-effect storms are removed. In each simulation we vary terrain height and environmental wind speed, which has been shown to be a strong predictor of lake-effect snowfall distribution. Results from this study will help to improve the prediction of lake-effect snowfall and our understanding of shallow, intense orographic precipitation.