Fig. 15.—Deflection of wind due to earth’s rotation.
How Wind Velocity Increases with Altitude. [Figure 16] shows how the velocity of the wind increases with elevation in the free air up to five thousand meters (about three miles). The average for the year, for the summer and for the winter, is given. It increases most rapidly up to six hundred meters in summer and up to eight hundred meters in winter. From these two heights there is a steady and pronounced slowing down of the wind up to one thousand meters; after which it increases up to five thousand meters, and how far beyond we know not. In winter there is a singular acceleration of velocity in the stratum between two thousand and twenty-five hundred meters and then no increase for the next five hundred meters; after which there is a uniform and steady gain up to five thousand meters. Starting at two hundred and seventy meters, the average velocity for the year is 3½ meters per second, or about 7¼ miles per hour. At five thousand meters altitude the average for the year is 11¼ meters per second, or about 27 miles per hour.
Fig. 16.—Annual, summer, and winter wind velocities, with altitude. 1, 1850 feet; 2, 2467 feet; 3, 3083 feet; 4, 15,417 feet.
CHAPTER IX
HOW TO FORECAST FROM THE DAILY WEATHER MAP
IT IS NOT DIFFICULT TO BECOME WEATHERWISE AND THEREBY TO GAIN ADVANTAGES IN HEALTH, HAPPINESS, AND BUSINESS
The person who will take the time to learn to interpret the daily weather map has a decided advantage over those who are less progressive. The maps may be secured by applying to any Weather Bureau station. Many members of commercial associations, having the advantage of seeing the large glass weather map that is made each morning by an observer of the Weather Bureau and displayed on the floor of the association, have become expert weather forecasters. The value of the principal crops of the country is largely influenced by the weather, as are the prices of transportation and industrial stock; and there is hardly a business that directly or indirectly is not influenced by the prospects of coming weather.