Humid climate

“ The waters of lakes, therefore, and rivers, would be much hotter in winter, and would be never chilled in summer by melted snow and ice. A remarkable uniformity of climate would prevail amid the archipelagoes of the temperate and polar oceans, where the tepid waters of equatorial currents would freely circulate. The general humidity of the atmosphere would far exceed that of the present period, for increased heat would promote evaporation in all parts of the globe. ”

“ Towards the margins of the zone, with increasing annual ranges of temperature, seasons in the extra-tropical sense gradually appear.
Physiological Effects of Heat and Humidity.—Tropical heat is associated with high relative humidity except over deserts and in dry seasons. The air is therefore muggy and oppressive. The high temperatures are disagreeable and hard to bear. The “hot-house air” has an enervating effect. Energetic physical and mental action are often difficult or even impossible. The tonic effect of a cold winter is lacking. ”

“ Yet even in the arid continental interiors in summer the absolute vapour content is surprisingly large, and in the hottest months the percentages of relative humidity may reach 20% or 30%. At the low temperatures which prevail in the winter of the higher latitudes the absolute humidity is very low, but, owing to the cold, the air is often damp. ”

“ Relative humidity varies greatly, and very low readings have often been recorded. Cloudiness seems to decrease somewhat towards the inner polar areas, after passing the belt of high cloudiness in the higher latitudes of the temperate zones. In the marine climates of high latitudes the summer, which is the calmest season, has the maximum cloudiness; the winter, with more active wind movement, is clearer. ”

“ The variation of temperature between day and night is considerable, but if the new-comer exercises a little care, he will not be unpleasantly affected by it. There are coast fogs, but these are not chilling and raw. Why it is that with the hydrometer showing a considerable humidity in the air the general effect of the climate is that of dryness, scientists must explain. The constant exchange of desert airs with the ocean air may account for the anomaly, and the actual dryness of the soil, even on the coast, is put forward as another explanation. ”

“ The absolute humidity as a whole decreases as the temperature falls. The relative humidity averages 90%, more or less, over the oceans, and is high under the clouds and rain of cyclonic storms, but depends, on land, upon the wind direction, winds from an ocean or from a lower latitude being damper, and those from a continent or from a colder latitude being drier. ”

“ Steppes, devoid of sand, and therefore less readily acquiring heat; impenetrable forests, which, protecting the earth from the sun’s rays, or radiating heat from the surface of their leaves, cover the richly-watered plains of the Equator, and exhale into the interior of the country, most remote from mountains and the 8Ocean, prodigious quantities of moisture, partly absorbed and partly generated—all these causes produce in the flat portions of America a climate which presents a most striking contrast in point of humidity and coolness with that of Africa. ”

“ The air was laden with carbon, which is the principal food for plants; so laden, indeed, that man, who is eminently an oxygen-breathing animal, could not have lived in it. The great humidity of the atmosphere was another element favorable to growth. Vegetation never lacked for an abundance of moisture either at root or leaf. Then, too, the climate was universally warm. Over the entire surface of the earth the heat was greater than it is to-day at the torrid zone. ”

“ Except near the United States the coast lands are tropical or semi-tropical; and the products of the soil, which in many quarters is extraordinarily deep and rich, are those which naturally result from extreme humidity and heat. Next comes an intermediate zone varying in general height from about 2000 to about 4000 feet, where the rainfall, though less abundant than on the coast, is ample, and the climate far more salubrious than below. ”

“ The elements—temperature, sunshine, wind, humidity, and rainfall—are recognized as having importance and should be known for every part of our country. The latest movement is for facts in local climate, even that of the farm or certain parts of it, and of the soil. ”

“ While the true basis on which to establish climatic areas or provinces is the resultant of all the weather elements which go to make up the atmospheric conditions recognised under the broader term climate, so many factors have to 185 be considered that it is extremely difficult to arrive at a general acceptable conclusion. The principal elements of the weather to be considered are, approximately, in the order of their importance, beginning with the one which exerts almost universal control—temperature, precipitation, the winds, absolute and relative humidity of the air, and evaporation. ”

“ As the south-west winds are always attended with a light atmosphere, an incipient vacancy, or a great diminution of air must have taken place to the northward of them in all parts of the earth wherever they exist, and a deposition of their moisture succeeds their being cooled by the climate they arrive at, and not by a contrary current of cold air over them, since in that case the barometer would not sink. ”

“ The polar limits of the temperate zones are fixed by the isotherm of 50° for the warmest month. Summer heat is more important for vegetation than winter cold, and where the warmest month has a temperature below 50°, cereals and forest trees do not grow, and man has to adjust himself to the peculiar climatic conditions in a very special way. ”

“ It is, upon the whole, not probable that so small an extent of forest, so situated, could produce a sensible influence on the general climate of the globe, though it might appreciably affect the local action of all climatic elements. The total annual amount of solar heat absorbed and radiated by the earth, and the sum of terrestrial evaporation and atmospheric precipitation, must be supposed constant; but the distribution of heat and of humidity is exposed to disturbance in both time and place by a multitude of local causes, among which the presence or absence of the forest is doubtless one. ”

“ Although the changes of temperature are very sudden and great, yet with proper care little harm is done, as the excessive dryness of the soil and atmosphere enables the residents to withstand with but little inconvenience a heat which would be quite unbearable in a moist climate. ”

“ It falls with the south and south-west, and rises with the north and north-west winds.
The quantity of water which falls in rain and snow, one year with another, amounts to from 24 to 36 inches. But to complete the account of variable qualities in the climate, it will be necessary to add, that our summers and autumns are sometimes marked by a deficiency, and sometimes by an excessive quantity of rain. The summer and autumn of 1782 were uncommonly dry. ”

“ No general law governs the variations of relative humidity with altitude, but on the mountains of Europe the winter is the driest season, and the summer the dampest. At well-exposed stations there is a rapid increase in the vapour content soon after noon, especially in summer. The same is true of cloudiness, which is often greater on mountains than at lower levels, and is usually at a maximum in summer, while the opposite is true of the lowlands in the temperate latitudes. One of the great advantages of the higher Alpine valleys in winter is their small amount of cloud. ”

“ With the exception of contributing to the formation of occasional fogs over their surfaces and the adjacent low lands, through the rising of warm water vapor into the cold air that often collects at the bottom of valleys during nighttime, rivers exercise little influence on climate. Lakes exert a modifying influence on the temperature of places near their shores but only for a few miles therefrom, and they are too small to exert any appreciable influence on rainfall. ”

“ The vapours from the rivers and the ocean produce in the upper regions clouds saturated with moisture which induce vegetation belonging to a colder climate. During the rainy seasons there is such an accumulation of these vapours as to cause a general coolness and occasion sudden heavy showers, and sometimes destructive floods. ”

“ Characteristic, also, of marine climates is a prevailingly higher relative humidity, a larger amount of cloudiness, and a heavier rainfall than is found over continental interiors. All of these features have their explanation in the abundant evaporation from the ocean surfaces. In the middle latitudes the oceans have distinctly rainy winters, while over the continental interiors the colder months have a minimum of precipitation. Ocean air is cleaner and purer than land air, and is generally in more active motion. ”

“ Again, there is the moist climate by the sea, or the quality of soil, the periodic torrential [Pg 9] rainfall of one section, and elsewhere the long months of drought.
Generally speaking, our country is, in most parts, a land of sunshine, with usually sufficient rain and moisture to benefit plant life, and while we grumble at our sudden changes in temperature, how few of us realize the blessing of an abundant sunshine pervading the "great outdoors" and incidentally the gardens! ”

“ Perhaps the immense quantity of drift ice which accumulates on the eastern shores, and which extends for so many miles out to sea, may have some influence on the temperature of the climate. The summer, on the other hand, during the short time that it lasts, is proportionally warmer, the thermometer rising from 70° to 80° above 0. Vegetation then proceeds with uncommon rapidity; the shrubs and plants expand as if by enchantment ”

“ The humidity of the atmosphere, although invisible, has a special and strong influence in absorbing radiant energy, whether from the sun or from the earth. It therefore converts the dry air into a powerful obstructor to the passage of radiant heat, and by this means the humid atmosphere is made to act as a blanket, keeping the earth and the lower air much warmer than it would otherwise be. ”

“ And this relation of cause and effect, manifest in individuals, is one which we may suspect holds in races—other things being equal. In temperate regions, differences of constitutional activity due to differences of atmospheric humidity, are less traceable than in torrid regions, the reason being, that the inhabitants are subject to a tolerably rapid escape of water from their surfaces, since the air, though well charged with water, will take up more when its temperature, previously low, is raised by contact with the body. ”

“ Cold humidity is the normal trait of the winter climate; catarrh is almost permanently epidemic; many of the inhabitants can echo the declaration of one their frank fellow-citizens, who says: 'Depuis que je me connais, je suis enrhumée. ”

“ The point of first importance concerns the distribution of heat and moisture over the surface of the land; for on these features depends the fitness of the land for all forms of life. The influences which principally determine the climate of a continent come to it from the neighboring seas. The moisture arises there, and finds its way thence to the land; and the heat or coolness which modifies the land climate comes with it. ”

“ The humidity is about 77 per cent. In the rainy season the mean temperature is 85°, and the humidity varies from 86 per cent to complete saturation. The annual rainfall is seldom less than 125 inches. A man six feet in stature standing on the shoulders of another man of equal height, would just about be able to keep his shoulders above water if the two were placed in a reservoir which would catch and hold the entire rainfall of the year. But in spite of heat and humidity and precipitated moisture, existence can be made passably comfortable. ”

“ By moistening the air woodlands also moderate the extremes of heat and cold. It is seen on the sea-shore how beneficently humidity operates in allaying the severity of winter, and in summer the evaporation of dew and rain gives us cool breezes when they are most needed. ”

“ The best climate is, therefore, one where the temperature ranges from not much below the freezing-point at night in winter to about 80 degrees F. by day in summer, and where the storms which bring daily changes are frequent at all seasons. ”

“ The chief effect of a varied relief is a varied climate. This changes with altitude in much the same way as with latitude. Heat and absolute humidity diminish, generally speaking, as height increases, while rainfall becomes greater up to a certain level. The effect of ascending and descending currents of air is to diminish the range of temperature on mountain slopes and produce rather an oceanic type of climate. The larger and more uniform a climatic district, the more conspicuously do even slight elevations form climatic islands, like the Harz Mountains in the North German lowlands. ”

“ Any alteration in the temperature of a climate or its degree of humidity, is unlikely to affect simultaneously the whole area occupied by a species; and further, it can scarcely fail to happen that the addition or subtraction of heat or moisture, will give to a part of some adjacent area, a climate like that to which the species has been habituated. ”

“ The position of the mountains also affects the rainfall of the interior. Since a large proportion of the moisture is condensed upon their ocean slopes, the climate of each succeeding range toward the interior becomes more dry and desert-like. While in some of the lowlands thus cut off from the ocean the climate is extremely arid, yet the country is relieved from utter barrenness through the presence of mountain peaks and ranges, which often condense considerable moisture. ”