Section 4 HYDROMETEOROLOGY: CLIMATE AND HYDROLOGY OF THE GREAT LAKES

The climate of the Great Lakes Region is determined by the general westerly atmospheric circulation, the latitude, and the local modifying influence of the lakes. Due to the lake effect, the regional climate alternates between continental and semi-marine. The semi-marine climate is more consistent contiguous to the lakes, but with favorable meterological conditions, it may penetrate deeply inland. The Great Lakes climate and hydrology are closely related. Variations in mean lake levels, and consequently lake outflows, are controlled by the imbalance between precipitation and evaporation. The Great Lakes drainage basin is discussed in other appendixes and a brief summary of the climatic and hydrologic elements of the drainage basin is given in Section 1 of this appendix. The major storm tracks affecting the Great Lakes Region are indicated in Figure 4-13. Distributions of mean annual values for air temperature, precipitation, runoff, and water losses over the land areas of the Basin, showing latitudinal and lake-effect variations, are indicated in Figures 4-15, 17, 19, and 20, respectively. The average monthly means, highs, and lows of overland air temperature for the individual lake basins and for the total Great Lakes Basin are shown in Figure 4-16.