A Simulation of Lake Michigan's Winter Land Breeze on 7 November 1978

Abstract

A two-dimensional mesometerological model was originally constructed by Alpert et a.. to simulate the summer air circulation in the area between the eastern Mediterranean waters and the Golan Heights involving en route Lake Kinneret (the Sea of Galilee). In this study the same model is applied to the case of the nocturnal circulation across southern Lake Michigan. The case simulated is for a wintry day in November 1978, the data for which were documented in a recent article by Passarelli and Braham. The results of the simulation are very encouraging. Particular mention should be made of the fact that the predicted location of the maximum upward velocities close to the Wisconsin shore of Lake Michigan and the associated lake-breeze front at the convergence zone of the lake breezes of the opposite shores are well predicted by the model. The observed land-breeze front was accompanied by the development of snow bands. The main purpose of this study is to demonstrate that a computationally inexpensive two-dimensional model can adequately simulate coastal flows like that of Lake Michigan in the present study, making it a potentially useful forecasting and diagnostic tool. It was our intention as well to test the same model (physics and numerics) with a different lake-circulation problem. Despite the great differences in the physical characteristics of topography, size and meteorological conditions of the two lakes to which the model was applied (in the lake Kinneret case, it is the lake which is cooler than the surrounding hot summer air of the Jordan Valley while in the Lake Michigan case it is the relatively warm lake which contrasts the polar air mass). However, in both cases the forcing is similar (10–15°C); it was found to do reasonably well. On the more theoretical side, this numerical study presents the first example of a strongly developed land-breeze front.