ON SOME WEATHER INFLUENCES DUE TO WARMING OF THE AIR BY THE GREAT LAKES IN WINTER

Abstract The effect of the Great Lakes on the motion and precipitation patterns during a cold spell (8 to 14 February 1958) is investigated. By calculating the rotational part of the motion and, also, by resolving the pressure field into orthogonal polynomials, measures of the intensity of the circulation systems associated with the Lakes were obtained. On occasions, separate effects of Lake Huron and Lake Superior could be identified. In general, the precipitation patterns caused by snow flurries from the Lakes revealed marked orographic influences. Well defined patterns, with a band of maximum precipitation about 15 to 25 mi from the shore, were found to occur persistently over the flat plains of northern Indiana and southwestern Michigan. Evidence is produced to show that these patterns are related to the nonadiabatic cooling and decrease in lapse rate of the air that moves from the open waters of Lake Michigan over the colder land.