Robert DeCourcy Ward

“ Is there any relation between the velocity of the wind and the hour of the day, i.e., does the wind seem stronger or weaker at noon than in the morning or at night? Is it a common occurrence to have a wind from the same direction for several successive days, or are we apt to have different winds almost every day? ”

“ The great areas of high and low pressure control our weather. On land, where daily weather maps are so easily accessible, a glance at the map serves in most cases to give a fairly accurate idea of the position and extent of cyclones and anticyclones, and hence also of the distribution of weather. At sea, on the other hand, the navigator has no daily weather maps to refer to, and his knowledge of the weather conditions which he may expect must be gained from his own observations alone. ”

“ The greater part of the Temperate Zone, in which we live, is peculiar in having frequent and rapid changes of temperature, not only from season to season, but from day to day, and during a single day. In winter, we are apt to have a warm wind immediately after a spell of crisp cold weather. In summer, cloudy, cool days come as a sudden relief when we have been suffering from intense heat, with brilliant sunshine. ”

“ Have you discovered any rule as to the time of day when rainstorms or snowstorms begin? When thunderstorms begin and end? Is it common or uncommon for us to have a storm lasting three or four days? How long does a thunderstorm usually last? Do we have most hail in winter or in summer? In what ways does a rainy day affect people? How are you yourself affected? How does a heavy snowstorm affect travel and transportation? In what ways does a snowstorm differ from a rainstorm as to the character of the precipitation and its effects? ”

“ These changes give a variety to our climate which is, on the whole, very beneficial to man. The North Temperate Zone, with strong seasonal changes in temperature and weather, is the zone of the highest civilization and of the greatest energy of man. In the Torrid Zone the changes of temperature are, as a whole, small. There is no harsh winter. The climate is monotonous and deadening, rather than enlivening. Man finds it easy to live without much work, and the inhabitants of the Torrid Zone have not, as a rule, advanced far in the scale of civilization. ”

“ The marked contrasts in temperature between the Northwest and the Pacific and Gulf Coasts at once suggest a reason why Florida and Southern California are favorite winter resorts. To these favored districts great numbers of people who wish to escape the severe cold of winter in the Northern States travel every year, and here they enjoy mild temperature and prevailingly sunny weather. To the cold Northwest, on the other hand, far from the warm waters of the Pacific, where the days are short and the sun stands low in the sky, no seekers after health travel. ”

“ One whole year of the grammar school course may well be given to the observations suggested in Chapter I, provided that there is no need of hastening on to the more advanced work. The advantage of extending the course over a whole school year is great, because such extension gives opportunity for becoming familiar with late summer, autumn, winter, spring, and early summer weather types, and this is far better than attempting to crowd all the work into one short season. The interest of a class can easily be kept up throughout a school year by means of a progressive system of observations. ”

“ What is the greatest difference in pressure which you have observed in a day? What is the least? Does the pressure seem to vary more or less in the colder months than in the warmer? Has the height of the mercury column any relation to the weather? Are we likely to have rainy weather with rising barometer? Is the velocity of the wind related to the pressure in any way? How? Can you make any general rules for weather prediction based on the action of the barometer? ”

“ In dealing with these temperature changes, we adopt a similar scheme. We say: The rate of temperature decrease is so many degrees Fahrenheit in a distance of one latitude degree (about 70 miles) . In order to make our measurements, we use a scale of latitude degrees, just as, in calculating railroad grades, we must have a way to measure the miles of track in which the ascent or descent of the roadbed is so many feet. Take a strip of paper 6 inches long, with a straight edge, and lay this edge north and south at the middle of the weather map, along a longitudinal or meridian line. ”

“ The chief interest and value of the instrumental work in meteorology are to be found not only in the taking of the daily observations at stated hours, but in the working out of numerous simple problems, such as may readily be undertaken with the help of the instruments already described. Thus, the temperature of the air (obtained by the sling thermometer, supplemented by maximum and minimum thermometers, and by the thermograph if available) can be determined under a variety of conditions, e.g., close to the ground, and at different heights above the ground; at different hours, by day and night ”

“ Land and sea breezes, although an unimportant climatic feature in these northern latitudes, are often of the highest importance in the Torrid Zone. The fresh pure sea breeze from over the ocean makes it possible for Europeans to live in many tropical climates where otherwise they would not keep their health. The land breeze, on the other hand, is apt to be an unhealthy wind in the tropics, especially when it blows off of swampy land. ”

“ A proper amount of bright sunshine is essential for the ripening of crops, but too much sunshine may parch soil and vegetation, and become injurious. Clouds bring rain; hence a sufficient amount of cloudiness is just as necessary as a sufficient amount of sunshine. The drift of clouds shows us the direction of movement of the air above us, and is of considerable help in forecasting the weather. ”

“ Our Weather Bureau takes special pains to study the movements of cold waves and to make forecasts of them, and so well are the warnings distributed over the country that the fruit growers and the transportation companies, and the dealers in farm produce, are able every winter to save thousands of dollars’ worth of fruit and vegetables which would otherwise be lost. Cold-wave warnings are heeded by many persons besides those who are directly interested in fruits and farm products. ”

“ But cyclones are not all alike—far from it. Some are well developed, with strong gradients, high winds, extended cloud areas, heavy precipitation, and decided temperature contrasts. Others are but poorly developed, with weak gradients, light winds, small temperature differences, and it may be without any precipitation whatever. Some cover immense districts of country; others are small and affect only a limited area. It therefore becomes necessary to examine the characteristics of each approaching cyclone, as shown on the daily weather map, very carefully. ”

“ The continuous procession of cyclones and anticyclones across the United States involves continuous shifts of wind. Over much of the earth’s surface, however, the regularity and constancy of the winds are the distinguishing feature of the climate. Over a considerable part of the belts blown over by the northeast and southeast trades, roughly between latitude 30° N. and S. and the equator, the winds keep very nearly the same direction and the same velocity day after day and month after month. Thus the trades are of great benefit to commerce. ”

“ For this reason a hot day in summer, when the air is comparatively dry, that is, not saturated with moisture, is cooler, other things being equal, than a hot day when the air is very moist. Over deserts the air is often so hot and dry that evaporation from the face and hands is very great, and the skin is burned and blistered. Over the oceans, near the equator, the air is hot and excessively damp, so that there is hardly any cooling of the body by evaporation, and the conditions are very uncomfortable. ”

“ In summer, the sirocco is usually dry, and during the prevalence of such winds we have our hottest spells, when sunstrokes are not uncommon. In southern Italy the sirocco has the same position with134 reference to the controlling cyclone. There the wind is often so dry as seriously to injure vegetation. The cold wave, on the rear of our winter cyclones, with its low temperature and dry air, often comes as a refreshing change after the enervating warmth of the preceding sirocco. ”

“ Districts which have a rainfall too small for successful agriculture, but are not by any means deserts, are often excellent grazing lands, as in the case of parts of Texas, Nebraska, and Kansas in the United States, and the Argentine Republic in South America. Where there is very little rainfall deserts are found. Cities are not built in deserts, because there are no occupations to attract large numbers of men. The inhabitants of the desert are wandering tribes, which move from place to place in search of water and food for themselves and their animals. ”

“ Another weather type, often noted during our winter in the central and eastern United States, and strongly contrasted with both of the preceding conditions, is that which brings us a warm, damp, southerly wind, frequently accompanied by heavy rains. As these damp winds blow over snow-covered surfaces they become foggy and the ground is said to “smoke”; the heavy rain rapidly melts the snow; slush and mud make bad walking; rivers and brooks rise rapidly, perhaps overflowing their banks; low-lying places become filled with standing water. ”

“ It was there learned that atmospheric pressure is measured by the number of inches of mercury which the weight of the air will hold up in the glass tube of the barometer. Our sensation of heat or cold gives us some general idea as to the air temperature. We can tell the wind direction when we know the points of the compass, and can roughly estimate its velocity. No instrumental aid is necessary to enable us to decide whether a day is clear, fair or cloudy, or whether it is raining or snowing. ”

“ The dependence of wind velocities on the pressure gradient is a fact of great importance in meteorology. The ship captain at sea knows that a rapid fall of his barometer means a rapid rate of pressure change, and foretells high winds. He therefore makes his preparations accordingly, by shortening sail and by making everything fast. The isobaric charts of the globe for January and July show that the pressure gradients are stronger (i.e., the rate of pressure change is more rapid) over the Northern Hemisphere in January than in July. ”

“ 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. ”

“ During the winter season, in all regions where snow forms the chief part of the precipitation, the only portion of the rain gauge that need be exposed is the overflow attachment. The snow which falls into the gauge may be measured by first melting the snow and then measuring the water as rainfall. About 10 inches of snow give, on the average, 1 inch of water, but the ratio varies very greatly according to the density of the snow. ”

“ C. The Occurrence and Characteristics of Local Winds, such as Mountain and Valley and Land and Sea Breezes.—If the observer happens to be living in or near the mouth of a valley or on a mountain side, opportunity may be given for the observation of the local winds down the mountain sides and down the valley at night, and up the valley and the mountain sides by day, known as mountain and valley breezes. Keep a record of wind direction and velocity during the day, and especially during the morning and evening hours. ”

“ At the end of each day the blackboard data should be entered in a permanent record book by some one of the scholars, and some ingenuity can be exercised in devising the best scheme for keeping this record. The record book should be carefully preserved in the schoolroom, where it may be referred to by the scholars of future years when any unusually severe storm, or a spell of excessively hot or dry weather, or a remarkable cold wave occurs, in order that comparison with past occurrences of a similar kind may be made. ”

“ It is evident, from even the most general observation of the weather elements, that the temperature experienced at any place is very largely dependent upon the direction of the wind. Thus, for instance, in the United States, a wind from some northerly point is likely to bring a lower temperature than a southerly wind. ”

“ Fahrenheit was a manufacturer of all sorts of physical apparatus, and it has been thought probable that he had some special facilities for dividing his thermometer tubes into 180 parts. Mercury is most commonly used as the liquid in thermometers, because it readily indicates changes of temperature, and because over most of the world the winter cold is not sufficient to freeze it. ”

“ Our sense of comfort in hot weather depends on the sensible temperatures. These sensible temperatures are not the same as the readings of the ordinary (dry-bulb) thermometer, because our sensation of heat or cold depends very largely on the amount of evaporation from the surface of the body, and the temperature of evaporation is obtained by means of the wet-bulb thermometer. Wet-bulb readings at the various stations of the Weather Bureau are entered on30 all our daily weather maps. ”

“ These cyclones which come up the eastern coast of the United States at certain seasons are usually violent, and often do considerable damage to shipping. The Weather Bureau gives all the warning possible of the coming of these hurricanes, as they are called, by displaying hurricane signals along the coast, and by issuing telegraphic warnings to newspapers. In this way ship captains, knowing of the approach of gales dangerous to navigation, may keep their vessels in port until all danger is past. Millions of dollars’ worth of property and hundreds of lives have thus been saved. ”