Effects of the Great Lakes' thermal influence on freeze-free dates in spring and fall as determined by Hopkins' bioclimatic law

Abstract

In this paper, an attempt is made to show that Hopkins' (1938) bioclimatic law, in the form of an isophanic model, makes possible a quantitative declaration and examination of the thermal effects of the Great Lakes in advancing the beginning of the freeze-free season in the spring, and retarding its departure in the fall. For the first time, the number of days that the frost-free period is lengthened due primarily to the lakes' effect is determined. Similarly, the application of bioclimatic law has made possible a quantitative comparison of the degree of influence expressed by these water bodies on daily minimum temperatures at the start and end of the freeze-free season.