. Carnegie Institution of Washington publication. 266 AGRICULTURAL INDICATORS. duction may ultimately be forecasted with something of the accuracy of daily weather forecasts at present. The excess-deficit balance.—The fact has already been emphasized that an excess of rainfall in one year is almost certain to be balanced by a deficit in the next year, while a great excess is often followed by two or rarely three years of deficit. As a rule, an excess is an amount above the normal rainfall and a deficit is an amount below it. Moreover, an excess in one region is often counterbalanced by a defic
. Carnegie Institution of Washington publication. 266 AGRICULTURAL INDICATORS. duction may ultimately be forecasted with something of the accuracy of daily weather forecasts at present. The excess-deficit balance.—The fact has already been emphasized that an excess of rainfall in one year is almost certain to be balanced by a deficit in the next year, while a great excess is often followed by two or rarely three years of deficit. As a rule, an excess is an amount above the normal rainfall and a deficit is an amount below it. Moreover, an excess in one region is often counterbalanced by a deficit in another, or an increase or decrease in one region is not met by a corresponding change in an adjacent one. When the balance operates from one year to another, it produces a cycle of 2 to 3 years. This cycle exhibits marked variations in rainfall, so much so that it may obscure the normal effect of the 11-year cycle at its maximum or minimum, though apparently not that of the 22-year cycle. In order to illustrate the operation of the excess-deficit cycle, use has been made of columnar graphs of the rainfall at widely separated points in the grassland climax. The points selected are Williston (North Dakota), Cheyenne (Wyoming), Akron (Colo- rado), and Amarillo (Texas). In the case of the first three places, the graphs have been adapted from those prepared respectively by Babcock (1915:5,) Jones (1916:4), and McMurdo (1916:4). The graph of Williston rainfall. 10 Mflll l I M 1900 1905 1910 1915 Fig. 18.—Graph of total and seasonal rainfall at Akron, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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