Determine the rates of temperature decrease in the following cases:—
A. For a considerable number of stations in different parts of the same map, as for each of the six days of the series.
And, using the school file of weather maps,
B. For one station during a winter month and during a summer month, measuring the rate on each map throughout the month and obtaining an average rate for the month.
C. For a station on the Pacific Coast, and one on the Atlantic Coast during the same months.
D. For a station on the Gulf of Mexico, or in Florida, and one in the Northwest during a winter month.
E. For a station in the central United States, and one on the Pacific Coast, the Gulf Coast, and the Atlantic Coast, respectively, during different months of the winter and summer.
The determination of the rates of temperature decrease under these different conditions over the United States prepares us for an appreciation of the larger facts, of a similar kind, to be found on the mean annual and mean monthly isothermal charts of various countries, and also of the whole world.
Temperature Gradients on Isothermal Charts of the Globe.—The mean annual isothermal charts of the globe (see page [63]) bring out some very marked contrasts in rates of temperature decrease. Thus, along the eastern side of the North American continent the isotherms are crowded close together, while on the western coast of Europe they are spread far apart. Between southern Florida and Maine there is the same change in mean annual temperature as is found between the Atlantic coast of the Sahara and central England. The latter is a considerably longer distance, and this means that the decrease of temperature is much slower on the European Atlantic coast than on the North American Atlantic coast. In fact, the rate of temperature decrease with latitude in the latter case is the most rapid anywhere in the world, in the same distance. These
great contrasts in temperature which occur within short distances along the eastern coast of North America have had great influence upon the development of this region, as has been pointed out by Woeikof, an eminent Russian meteorologist. The products of the tropics and of the Arctic are here brought very near together; and at the same time intercommunication between these two regions of widely differing climates is very easy. Labrador is climatically an Arctic land, and man is there forced to seek his food chiefly in the sea, for nature supplies him with little on shore, while southern Florida is quite tropical in its temperature conditions and in the abundance of its vegetation. Between the Pacific coasts of Asia and of North America there is a similar but less pronounced contrast, the isotherms being crowded together on the eastern coast of China and Siberia, and being spread apart as they cross the Pacific Ocean and reach our Pacific Coast.