Many large orchards have their “warm spots” and their “cold islands” or “north poles,” well known to the orchardist; due in some cases to the nature of the soil rather than to topography. Certain mountain regions in North Carolina are famous for their “thermal belts” or “verdant zones”; i. e., areas part way up the slopes that escape the frosts occurring both above and below them. These frostless belts, which have been the subject of numerous investigations for three-quarters of a century, seem to mark the upper level of the pool of cold air that collects in the valley by drainage from the mountainsides. A detailed temperature survey of the thermal belt region of North Carolina was made during the years 1912–1916 by the United States Weather Bureau and the North Carolina State Board of Agriculture. In some places the minimum temperature at night was found to be 15 or 20 degrees higher in the thermal belt than at the bottom of the valley, a few hundred feet below.
Clouds, by checking radiation from the earth, and wind, by mixing the colder and warmer layers of air together, both prevent frosts that would otherwise occur. Artificial methods of protection include covering plants with screens of wood, paper, or cloth, building smudge fires to provide a blanket of smoke (a method of doubtful value), and, above all, heating by means of wood fires or various types of “orchard heater,” burning either oil or coal. An elaborate technique of orchard heating has been developed, having in view especially the most economical use of fuel and labor consistent with the object to be attained. In many cases orchards are provided with alarm thermometers, which ring a bell when the temperature approaches the danger point in the orchard.
The local prediction of frost from the readings of meteorological instruments is a problem that has not been fully solved. The idea formerly prevailed that the temperature of the dew point, as determined from readings of the dry-bulb and wet-bulb thermometers in the early evening, was a safe guide to the fall of temperature to be expected during the night, but this belief has not stood the test of accurate observations. At the present writing certain formulas involving data of both temperature and humidity are being used experimentally by Weather Bureau specialists for predicting the lowest temperature of the night when the general conditions indicate that frost is possible. A comprehensive discussion of this subject has been published by the Bureau as Supplement No. 16 of the “Monthly Weather Review.” (Washington, 1920.)
CHAPTER XVI
COMMERCIAL METEOROLOGY
It is a significant fact that the American Meteorological Society, which was organized in 1919, has a Committee on Commercial Meteorology. The appointment of this committee was one of the earliest tokens of the fact that the applications of meteorology to business, always recognized to be important and far-reaching, had at last been segregated as a distinct field of inquiry. The time is near at hand when this field will have its corps of specialists and its textbooks. Courses in commercial meteorology will be given in business colleges, and meteorologists will be attached to the staffs of large business enterprises. The chamber of commerce of a wide-awake western city already maintains a Department of Meteorology, with a former Weather Bureau official at its head, and “consulting meteorologists,” now practicing their novel profession in other parts of the country, find their principal clientele among business concerns.
Weather not only influences most kinds of business, but is the foundation of many of them. Plenty of illustrations of the latter fact will be found in every large department store. Umbrellas, rubbers, and mackintoshes are made and sold because of rain; their best market is in countries with rainy climates, and their sale from day to day fluctuates with the state of the sky. Electric and palm-leaf fans are a drug on the market or the reverse, according to the readings of the thermometer. Sleds and ice skates are sold where and when the weather is cold. This list may be prolonged ad lib. If we leave the department store and walk along any business thoroughfare, we shall discover other striking examples of commercial undertakings that owe their existence chiefly or entirely to the weather. Abolish cold weather and you abolish the dealer in furnaces and heating stoves, besides reducing the rank of the coal-dealer considerably below the “baronial” level. Eliminate hot weather from the meteorological program and the ice dealer will likewise tumble from his high estate.
All this is so obvious that it seems hardly worth while setting down; and yet the paradox must somehow be explained that business men have not, in general, paid much attention to meteorology, and that they have made only fragmentary use of the official meteorological establishments that were created, in part, for their benefit. Probably this paradoxical situation is merely a case of mental inertia. During the long ages of traffic before there were any weather maps, scientific weather forecasts, or climatic statistics, the weather was necessarily an unknown quantity in the mathematics of buying and selling. That it is not so to-day is a fact to which the business mind has been very slow in adjusting itself.
We have mentioned some of the obvious relations of weather to commerce, but there are others that are not so obvious. Many of these are indirect. Thus the effects of the weather on agriculture are nearly always reflected in the commercial world. It is not the farmer alone who suffers from a prolonged drought, for example. It has been asserted that every severe financial panic in our history has been closely associated with a protracted period of deficient rainfall, and that there has been no period of protracted drought without a severe financial panic except one that occurred during the Civil War. Mr. H. H. Clayton, who published this assertion in 1901, has cited the case of the wheat crop as illustrating the magnitude of the effect that rainfall exercises on economic conditions in general through its effects on agriculture.