Climax

CLIMAX (from Greek climax-ladder), climacteric, climacteric period, transition age, transition years, period of a woman's life when her reproductive capacity ceases, one of the manifestations of which is the presence of an ovarian-menstrual cycle. This period is not strictly limited. It does not occur suddenly, but gradually. Among age-related crises, climax is no less important than puberty. Time of onset. C. occurs in the fifth decade of life. Numerous statistics give conflicting figures. Schaffer found that C. occurs in 44% of cases between the ages of 45 and 49, and in 74% between 45 and 54 years. On average, the onset of menopause coincides with 47.26 years. According to Kleinwachter, the onset of C. between 45 and 50 years is observed in 54.15%, in 15% it occurs later, and in the rest before 45 years. Exceptions are cases of premature C. (C. praecox), when menstruation ceases before the age of 40. C. praecox occurs in 3.5% of cases. Much rarer are cases of late C.-C. tarda (1.5%). There are cases with normal menstrual function up to 55, even up to 60 years. The duration of C. varies greatly among individuals. While the process of transforming a child into a woman lasts for years, the climacteric period is shorter: it usually lasts for one, two years (according to Tilt, on average 1.11 years) and rarely extends for a longer time. Climax stands between the childbearing age of a woman and old age (senium), and therefore can be called pre-senile or presenile age crisis (see Age crises). The transition of C. into old age usually also occurs gradually. Factors influencing the onset of C. The basis of C. is the gradual fading of the function of the sex glands, occurring under the influence of a number of factors, both external and internal. The influence of climate at present is controversial. While some believe that a warm climate delays the onset of menopause (Mantegazza), others believe that in a warm climate menopause occurs earlier (Bruck, Oppenheim). There are authors who completely deny the influence of climate (Rouvier). More important is the role of racial characteristics. Generally speaking, in women who start menstruating earlier, C. also occurs earlier. C. occurs particularly early in women of black races. Women also enter the transition period early: Chinese women (not later than 40 years, often earlier), Japanese women (by 40 years). In women in the USSR, judging by numerous works by Russian authors (Rodziewicz, Grigoriev, Potapova, etc.), climax occurs between the ages of 43 and 49, most often at 45-46 years (Gruzdev). The influence of heredity is undeniable. If, for example, the mother menstruated unusually long, then in some daughters one can expect a late onset of C. Living conditions are also important: here the wear and tear of the body due to heavy physical labor, unhygienic conditions, etc., have an effect. Malnutrition also apparently accelerates the onset of menopause. According to Mayer, women of the privileged classes stop menstruating on average at 47.138 years, while women of the poorest layers at 46.976 years. Constitutional factors also influence the time of onset of C. In women of the infantile type, accelerated fading of menstrual function is observed. Intersex women (Mathes) are prone to an earlier onset of menopause. According to Aschner, menstruation persists particularly long in broad-boned, not very fat, dark-haired women. Certain diseases, such as diabetes, obesity, lead to premature C. Various exhausting factors and severe general diseases can also accelerate the onset of menopause. There are indications that severe psychological trauma can also lead to a sudden onset of C. Some diseases of the sexual sphere, accompanied by phenomena of stagnation in the pelvis or chronic irritation, lead to late C. Everyday observations show that patients with uterine fibroids menstruate for a very long time. Anatomical changes in the sexual organs during C. As long as there are menstrual bleeding, there are maturing or ovulating follicles and yellow bodies in the ovary in various stages of development. After the cessation of menstruation, the last yellow body also regresses. Follicles undergo atrophy and disappear. The parenchyma of the ovary is gradually replaced by dense connective tissue, in which hyaline masses are noticeable at the site of former yellow bodies. The entire ovary decreases in volume, shrinks, and becomes hard, flat, and bumpy. The surface of such ovaries externally somewhat resembles the surface of the cerebral hemispheres (ovarium gyratum). In the cortical layer and in the hilus, sharp changes in blood vessels are observed: hyaline degeneration and sclerosis predominate. In the remaining parts of the sexual apparatus, wrinkling processes occur. The tubes become thinner and shorter, phenomena of atrophy of muscle and elastic tissues are observed, the folds of the tube flatten, collapse, and fuse with each other. Dense connective tissue proliferates in the stroma of the folds. The epithelial covering loses cilia, the cells become cubic, even flat. Physiological obliteration of the lumen of the tube is also observed. The uterus gradually decreases in volume, all its layers become thinner, the cavity is narrower. Due to atrophy of the musculature and loss of tone, the small, flaccid, shrunken uterus often leaves the physiological anteversion-flexion and passes into retroversion. Histologically, progressive atrophy of muscle elements and their replacement by fibrous connective tissue are observed in the uterine musculature. In the blood vessels-phenomena of sclerosis and hyalinosis. The uterine mucosa at the beginning of C. is in a kind of indifferent state, soon after, increasingly severe atrophy develops. The entire mucosa becomes thinner, first in its functional, later in the basal layer. The gland cells become lower, more cubic, the stroma seems denser. To this picture later multiple cystic dilatations of the glands are added. The beating of cilia gradually ceases. The vaginal part sharply decreases in size and shortens, sometimes almost completely disappears, the cervical canal narrows, sometimes to complete impassability. In the latter case, the secret of the uterine glands accumulates in the uterine cavity in the amount of several cubic centimeters. This fluid is mucous-watery (hydrometra senilis, mucometra). If the fluid accumulated in the uterine cavity takes on the character of pus, then pyometra results. The parametria shorten and wrinkle. Significant changes are observed in the vagina. The vaults flatten, the upper part of the vagina narrows conically. The mucous membrane becomes smooth, the folds disappear; the narrowing of the vaginal lumen occurs later, in old age. The entrance to the vagina somewhat narrows already during C, its mucous membrane is easily injured due to atrophy. The external genital parts decrease in size, the large and small lips become flaccid; particularly noticeable is the flabbiness of the large lips, depending on the atrophy of adipose tissue. The hair on the pubis and lips becomes sparse and gray. Histologically, all elements of the vagina and external parts give a picture of atrophy. The papillae are smoothed, the muscularis thins out, the sebaceous glands and even Bartholin's glands atrophy. External changes. The anatomical changes characteristic of C. are not limited to the sexual organs, but to a greater or lesser extent cover the entire woman's body. In general, some features begin to appear in women, which, starting in C., imperceptibly pass into old age. The most striking are the changes in external forms due to the enhanced deposition of fat in the subcutaneous tissue with the simultaneous loss of the skin's turgor. The mentioned phenomena in women of different constitutional types are expressed far from uniformly. While in a woman of the pycnic type (Kretschmer; according to Mathes-youthful form) the climacteric period passes little noticeably and the deposition of fat occurs more or less uniformly, in women of asthenic and intersexual types the matter is different. In asthenic women, the unevenness of fat deposition is particularly pronounced, accumulating on the face, neck, chest, abdomen, thighs, and buttocks. This disrupts the harmony of forms. Often the woman's figure takes on a caricatured appearance. The roundness of forms disappears, the musculature becomes flaccid; the skin, especially on the extensor surfaces, becomes flabby and sags. The breasts sag, the nipples decrease, shifting downward and outward. Women of the intersexual type are little prone to obesity during C. In them, purely male signs often begin to appear, giving them a special appearance. The facial features begin to appear more sharply and become coarser. Abnormal hairiness appears; single hairs grow on the chin and under it, as well as on the cheeks. In rare cases, real beards and mustaches grow. Hair growth is also observed on the abdomen (according to the male type), on the thighs and calves. Instead of obesity, we see weight loss in them. The mammary glands almost disappear, the nipples protrude more, the areola pigments, a pigmentary belt appears around the waist. Clim. phenomena of C. are difficult to classify. The simplest division is Wiesel's into subjective disorders and objectively determinable changes.

Kehrer distinguishes vasomotor-sensitive, motor-sensitive, hypersecretory, and psychic disorders. Among the clinical phenomena, changes in menstrual function are in the first place. The cessation of menstrual bleeding occurs differently. In some cases, the menstrual function ceases immediately after a normal menstruation begins-

CLIMAX

A prolonged menopause may occur. More often, however, there is a gradual disturbance in the regularity of menstruation; the interval between them becomes shorter or longer, and often the menstruations first become more frequent, only to become less frequent in the near future. Often after a more or less prolonged menopause, menstruation appears one or more more times. During climax, blood loss is often unusually heavy, taking the form of menorrhagia or metrorrhagia. So-called 'falling phenomena' are very characteristic of climax. This includes a whole range of disorders depending on the cessation of ovarian function. The cause of the falling phenomena cannot be amenorrhea as such, nor the retention of toxic substances, as Ashner suggests, nor the cessation of ovulation, but is the cessation of the internal secretory function of the ovary. In different women, the falling phenomena are expressed differently. While some do not notice them at all, others suffer greatly from them. The more labile a woman's nervous system, the more she suffers from the falling phenomena. Women with a healthy nervous system go through climax, sometimes not noticing it at all, while women with some deficiency in it experience great suffering. When menopause sets in suddenly, the falling phenomena are more pronounced than when it occurs gradually. Among the falling phenomena, vascular motor disorders stand out. These include so-called 'hot flashes,' a sudden feeling of heat, sudden reddening of the face followed by pallor. Hot flashes appear without any apparent cause or in connection with physical work or emotional excitement, in attacks, several times a day, sometimes even at night. The woman feels a localized sensation of heat, her face reddens, her skin becomes hot, often followed by perspiration on the face or only on the forehead, cheeks, nose, scalp, back, palms. Perspiration is often observed not only in the areas of redness but also covers the upper part of the body or even the entire surface of the body. A hot flash is often accompanied by a feeling of dizziness, unpleasant dryness in the mouth, or, conversely, increased salivation. After a hot flash, a feeling of fatigue appears. Sometimes hot flashes are observed not in the head area, but there are hot flashes to the chest or abdomen, to the pelvis. Numbness of the extremities, a feeling of 'crawling ants,' cooling and blueness of the fingers of the hands and feet are also among the falling phenomena. At night, cramps in the muscles of the extremities, especially in the calves, are not uncommon. Dizziness, fainting, and flickering before the eyes are also frequently observed. Dizziness appears in the morning or during work, for example, when bending the body forward. Sometimes during dizziness, a feeling arises as if the ground is slipping from under one's feet. Sometimes women complain particularly of noise in the ears, appearing in attacks, in the form of buzzing, ringing, or lasting long and increasing toward the night. -From the heart side, heart palpitations, increased pulse rate, arrhythmia, pains in the heart area, precordial anxiety, and a feeling of fear should be included among the climax phenomena. The symptom complex can simulate angina pectoris. Zacherl considers 'vascular pains,' vasalgias, to be characteristic of climax suffering. These pains are localized in the temples, in the carotid artery, in the aorta, in the femoral, popliteal, and calf arteries. What is characteristic of these pains is that they are aggravated by pressure. Localized in the legs, they impede walking and lead to intermittent claudication. Sometimes women complain of shortness of breath, change of voice, and dryness in the nose. -From the digestive tract, changes in taste, loss of appetite, belching, bad taste in the mouth, and even vomiting are sometimes observed. Much more often - persistent constipation, atony of the intestines, accompanied by meteorism. Diarrhea with colicky pains in the abdomen are also observed. These diarrheas should be regarded as secretory neuroses of the intestine. It is interesting that these diarrheas can appear in attacks, sometimes at regular 4-week intervals (Tilt). These diarrheas are very persistent and do not respond to treatment. Perhaps they are equivalent to non-occurring menstruation. They can be accompanied by the discharge of blood from the intestine. -Complaints of pain in the sacrum, pelvis, frequent urges to urinate or incontinence of urine are also not uncommon. -From the nervous system, headaches are observed, localized in the forehead or occipital area, often taking the form of hemikrania with vomiting. Women often complain of persistent insomnia. Insomnia depends either on hot flashes, perspiration, meteorism, various pains, or is connected with a nervous state, depression, increased sexual feeling. In some cases, sleep is restless, often interrupted by waking, while in others women cannot fall asleep for a long time. -It is impossible to draw a strict line between the physiological phenomena of climax and definitely pathological phenomena. This applies especially to phenomena from the nervous system. The onset of the transitional period cannot but affect a woman's psyche. If, on the one hand, some women calm down and become more balanced with the onset of menopause, on the contrary, the majority shows increased nervousness, mild excitability, moodiness; often depression or groundless anxiety, fear of open spaces, loss of memory, obsessive ideas, apathy are observed. The pathology of climax. Climax is particularly severely endured by neurasthenic women. In them, severe phenomena of depression, hypochondriacal moods often occur. Finally, in some cases, true psychoses develop, called climacteric. Apparently, climax plays a provoking role in the occurrence of psychoses. Climacteric melancholia, involutional paranoia, involutional paraphrenia, and hysteria are distinguished. Melancholia lasts for years, and if it is cured, it still leaves behind a weakening of mental abilities. Climacteric paranoia affects women with a psychopathic predisposition. Climax is the heaviest blow for them. They consider life over, themselves as used-up, unnecessary. In the symptom complex of this form, ideas of persecution and affect of jealousy stand out. Cases of suicide of such patients are known. The phenomena of climax pass into clearly pathological not only in the psychic sphere, but somatic phenomena are often sharply pathological. It has already been indicated above that menstruations during climax often take the form of menorrhagia or metrorrhagia. Sometimes, while maintaining their periodicity, menstruations become prolonged and profuse, or the regular cyclicity is disturbed, and bleeding takes on a disorderly character. Due to such blood loss, severe anemia can develop, with the hemoglobin content in the blood decreasing to 20-15%. In the etiology of bleeding during climax, sclerotic changes in the blood vessels of the uterus, its poor contractile ability, excessive hyperemia of the sexual apparatus, which are also favored by enteroptosis and chronic constipation, may lie. However, there is no doubt that the most important cause of bleeding is the disturbance of the proper function of the ovaries. One should assume insufficient influence of the yellow bodies, premature ripening of follicles, persistence of the follicle without the formation of a yellow body; all this brings complete disorder into the cyclicity of life of the endometrium, and due to this, bleeding has either menorrhagic or metrorrhagic type. -It must be pointed out that uterine bleeding during climax is by no means always climacteric bleeding. Indeed, in this period of life in women, various new growths often develop. In the first place is fibroma of the uterus (myoma, fibromyoma), especially submucous, giving abundant menorrhagias, which can later pass into prolonged metrorrhagias, bringing patients to extreme degrees of anemia. It is also well known that in the transitional years, cancer of the uterus, especially cancer of the cervix, giving irregular type bleeding, is very often observed in women. Sarcoma of the uterus is much rarer. Besides new growths, other diseases of the uterus can be the cause of bleeding, such as retroflexion, prolapse, falling, catarrh of the cervix, erosion, mucous polyps, etc. -Separate are the bleeding that appear after a more or less long time after menopause has occurred. These bleedings should always be regarded as pathological phenomena. Whether the bleeding is abundant or slight, single or periodic - in its basis lies most often a malignant new growth of the cervix or body of the uterus. In recent years, observations have appeared that postclimacteric bleeding often indicates cancerous affection of the ovaries. In some cases, postclimacteric bleeding is a symptom of more innocent diseases, for example, simple erosions, mucous polyps, submucous myomas, senile colpitis. To the pathology of climax should also be attributed a number of diseases of the sexual organs. One of the most frequent complaints of women in the climacteric period is leucorrhea - from insignificant, colorless, mucous discharges that bother the patient little, to the profuse discharge of a corrosive purulent fluid leading to maceration of the skin of the external parts, to intertrigo, eczema.

Constant humidity, soiling of undergarments, and the sensation of burning and itching often drive women to despair. During and after the Climax, a special form of colpitis, colpitis senilis adhaesiva, is very frequently observed. The vaginal epithelium becomes wrinkled in places; the walls of the vagina, especially in its upper third, adhere and fuse, leading to narrowing of the vaginal canal and deformation of its lumen. Diseases of the Climax also include pruritus of the external genital organs-pruritus vulvae. The etiology of pruritus is not uniform. Symptomatic and 'essential' pruritus are distinguished. The first is often found in erosive discharges (in colpitis), in intertrigo, diabetes, etc. In 'essential' pruritus, it is impossible to discover the cause of the itching. Pruritus in the climacteric period is very persistent and can bring the patient to a state of extreme depression and even despair (in some cases of pruritus, a good therapeutic effect can be obtained from X-rays). Closely associated with pruritus is a special disease of the vulva-leukoplakia of it, manifested by white spots with thickened epidermis on the lips. The final stage of leukoplakia is kraurosis vulvae, which is sometimes accompanied by the development of carcinoma. Pruritus of the genital organs is quite common (according to Scheuer's data, out of 440 patients, 46 suffered from pruritus). Pruritus may be limited to the external genital organs or extend to the perineum and into the vagina. Often, along with pruritus of the genital organs, or independently of it, general pruritus of the entire body is also observed. Fairly often during the Climax, various changes occur in the skin, fluctuations in pigment deposition occur. For example, hyperpigmentation (similar to chloasma gravidarum) is found on the face, neck, and chest in the form of sharply defined and delimited light or dark brown spots. Some authors even believe that they are so frequently observed and appear so characteristic that one can even conclude from them that the Climax is approaching or has occurred. Along with the above-mentioned phenomenon of 'flying heat' (ardor fugax) on the face and upper part of the body, acne rosacea, various kinds of erythema, urticaria are often observed; purpura, prurigo, and herpes, eczema are less frequently observed. Among other diseases characteristic of the Climax, excessive obesity, gouty phenomena, neuralgic and rheumatic pains, and eye diseases (predisposition to cataracts, glaucoma, conjunctivitis) should be noted. Diseases of the joints are interesting: symmetrical thickenings on the fingers of the hands between the 1st and 2nd phalanges with decreased sensitivity and trophic III changes in the nails, as well as disfiguring arthritides. Menge (Menge) identified a special form of deforming arthritis, specific to the Climax, naming it arthropathia ovaripriva. Early stages of this disease can occur without morphological changes in the joints. A number of authors fully agree with Menge and see the etiology of these peculiar joint lesions in the disruption of the function of the endocrine glands, mainly the sexual and thyroid glands. In arthropathia ovaripriva, the knee joints or shoulder joints, finger joints are affected. A characteristic feature of the disease is the symmetry of the lesions. Finally, mention should be made of the so-called Heberden's nodules, which develop in women during the Climax in the form of thickenings of the terminal interphalangeal joints of the fingers of the hands (see Heberden's nodules). The pathogenesis of the phenomena characteristic of the Climax is far from fully understood. It is beyond doubt, however, that the cessation of ovarian function is not indifferent to other endocrine glands. The thyroid gland enlarges, and symptoms characteristic of either Basedow's disease or myxedema often appear. It has been experimentally established that after castration, the cortical layer and partly the medulla of the adrenal glands hypertrophy, that the islets of Langerhans in the pancreas increase, and that changes also occur in the pituitary gland. Therefore, it should be assumed that the phenomena of the Climax are caused not only by the loss of ovarian function but also by changes in the normal function of other glands of internal secretion. Thus, climacteric phenomena should be regarded as a polyglandular symptom-complex. For clinical practice, it is important whether the loss of the internal secretory function of the ovaries occurs suddenly or gradually; in the first case, severe clinical phenomena are inevitable, while in the second case, adequate compensation by other glands is achieved. Furthermore, it has been established that during the Climax, an increased sympathicotonia is observed. The latter is probably connected with the disruption of the balance of the endocrine system. The increased sympathicotonia explains the vasomotor phenomena. Schickele found elevated blood pressure in 50% of women suffering from phenomena of loss. He considers this hypertension a sign of increased tone of the sympathetic nervous system. On the other hand, in a number of cases, vagotonia rather is observed (Gobert, Schröder). Hot flashes are explained by the disruption of the activity of the vasomotor center. Blood in large quantities leaves the area of the p. splanchnici and flows to the periphery; after some time, the peripheral vessels constrict, and the blood moves back to the area of the p. splanchnici. Vizel notes a Climax proceeding with symptoms of hyperthyroidism, and a Climax proceeding with symptoms of hypothyroidism. The former is more characteristic of intersexual-type women, the latter of asthenic women. Artificial climax after surgical removal of the ovaries and exposure to X-ray rays-see Castration. Hygiene and therapy of the Climax. For the prevention and treatment of the numerous phenomena characteristic of the Climax, a certain regimen should be prescribed. Diet is especially important. Everything that has an exciting effect on the cardiovascular system should be prohibited: alcoholic beverages, coffee, strong tea, spices, strong broths. To prevent hot flashes, distracting remedies to the intestine in the form of mild laxatives are useful. Periodic intake of mineral waters regulates the stool, eliminates intestinal bloating and counteracts obesity. Prolonged stay in the fresh air, systematic, not too tiring walks, light gymnastic exercises in the morning and evening are recommended. Before sleep, rubbing of the body with cool water with the addition of vinegar or cologne is useful, especially in case of insomnia. In pronounced phenomena of loss, treatment is usually directed toward replacing the missing ovarian hormones. All kinds of ovarian preparations are prescribed (ovarin, etc.). There are many organotherapeutic preparations. At present, the best in the West is considered to be folliculin (Zon-clek). The effect of treatment with ovarian preparations is sometimes negligible or entirely absent. When taken internally, the active principle is probably destroyed in the gastrointestinal tract. With subcutaneous administration, an effect can rather be expected. Calcium in the form of calcium lactate is widely used, especially in vasomotor disorders; theobromine_g is prescribed, acting as a vasodilator. Halban recommends tablets 'climazan', containing theobromin, calcium lactate, and nitroglycerin. In cases of hyper- and hypothyroidism, it is useful to prescribe the corresponding preparations. Engelhorn proposed bloodletting, which Aschner warmly recommends, seeing the cause of all climacteric disorders in the accumulation of excess blood in the body (plethora). In cases of excitement, bromine, calcium with bromine, camphor bromide, valerian in various forms, as well as general warm baths are prescribed. For heart palpitations, Extr. fl. Cacti grandiflori works well. Persistent constipation requires the prescription of mild laxatives, enemas, a vegetable diet. In cases involving the urinary bladder, if cystitis and other diseases are excluded, bromine preparations, belladonna; even narcotics may be required. For the treatment of muscle and joint diseases, quinine, salicylate preparations-, atophan, adrenaline, baths, diathermy, mud therapy, protein therapy_g autogenous blood therapy, X-rays have been proposed. The latter were also proposed against phenomena of loss. A number of authors have successfully used X-ray irradiation of the pituitary gland as well as the thyroid gland. Psychotherapy is of enormous importance in the treatment of climacteric disorders. Often psychotherapeutic measures are sufficient to eliminate many phenomena of the Climax. In exceptional cases, hypnosis may be required.

G. Henter. Climax of men. If the Climax of women has a definite, universally recognized clinical picture, then the Climax of men is denied by most authors, because in reality it is extremely difficult to grasp the shifts that occur in the male organism in his transitional years, i.e., during the period of fading of sexual functions. This period in different individuals can occur at very different ages, usually between 50 and 70 years. Among metabolic disorders, a tendency to obesity and manifestations of gout are noted. Cardiovascular phenomena (flushes of blood to the head, palpitations, etc.) are also noted.

5 15 24 32 30 42 35 16 5 Solar energy, as has been said, is weakened in passing through the atmosphere due to absorption by its constituent parts (CO₂, water vapor) and due to scattering by air molecules, water particles, dust, fog, and clouds, and solar radiation is weakened to varying degrees. In general, it is considered that about ^x/_a% of the solar energy sent by the sun at the zenith reaches the earth's surface. The absorption of solar energy by the atmosphere depends on the degree of transparency of the atmosphere. The transparency coefficient varies with the time of year; on average it is 0.786. In summer the air is less transparent due to dust and increased absolute humidity. From the eruption of enormous quantities of volcanic dust into the atmosphere (e.g. during the eruptions of Krakatoa, Mont Pelée), solar radiation was weakened by 15-20%. Sometimes the weakening of solar radiation reaches 50%. Cloudiness can reduce solar radiation during the year by 36% or more. - The lower the sun stands above the horizon, the longer the path solar radiation travels within the atmosphere and the greater part of it is absorbed by the atmosphere (closer to the poles, at sunrise and sunset). Part of the heat from solar radiation absorbed by the atmosphere is transferred to the earth in the form of diffuse (scattered) radiation from the atmosphere. The latter determines the daily fluctuations in temperature on cloudy days when the sun is completely invisible. The loss of heat by the earth through radiation under clear skies has a significant influence on the climax, especially at night. With height up to 3,000 m radiation increases. At sea level, the earth's night radiation under cloudless sky is determined at 0.14 calories per 1 cm² of horizontal surface per minute, and at an altitude of 3,100 m - at 0.2 calories. Cloudiness and dustiness reduce diffuse radiation. - On the basis of the above general review of the elements of climate and the factors affecting it, a specific description of individual climates can be given in the following specific grouping: 1) by temperature - a) polar climate, b) temperate climate, c) tropical climate; 2) by geographical location - a) maritime, b) continental, c) mountain, d) climate of high plateaus. Polar climate. Around the poles, marked by the polar circle (66¹/₂° latitude), are polar regions, one in each hemisphere; they together occupy about 8% of the earth's surface. At the poles, day lasts for half a year, and night for half a year. Within the polar regions, toward the polar circle, the duration of the polar night gradually decreases. The polar region is characterized by very large annual temperature fluctuations and small diurnal ones (e.g. in Greenland the diurnal amplitude averages 1.4°, while the annual one reaches 43.5°). The summer temperature is low, since solar heat is spent on melting the polar ice. The air contains little water vapor; precipitation is scarce. The soil thaws for only a few centimeters during the summer, and deeper down it is in a state of "permafrost". Polar vegetation appears only in the zone bordering the temperate climate. The landscape is highly monotonous - an ocean covered with ice, and land covered with snow. Within the polar circle two zones are distinguished: 1) climate of eternal frost, where even in summer the temperature is below 0° and there is no vegetation at all (such is the climate of the central part of Greenland and the northern part of Novaya Zemlya), and 2) tundra climate - with an average temperature of the warmest month not higher than 10-12°, but not below 0°. Temperate climate occupies in both hemispheres the space from the polar circles (66¹/₂° latitude) to the tropics (23¹/₂° latitude), approximately about 52% of all land. The height of the sun at noon in the temperate climate at the polar circles varies throughout the year between 0° and 47°, and at the tropics - from 43° to 90°; the duration of the day at the polar circles - between 0 and 24 hours, and at the tropics - between 10.4 and 13.4 hours. The temperate climate is characterized by average insolation and large amplitudes of fluctuations of all meteorological factors, representing transitions from polar to tropical: thus, in the northern part of the belt (in northeastern Siberia, in the city of Verkhoyansk, located somewhat south of the polar circle) the lowest temperature on earth is observed at -70°, with an average January temperature of -50.5°, while in the southern part of the belt the highest is recorded - with the highest temperature up to +57° and with an average July temperature of +38.9°. Since the temperate belt has a very long coastline and is washed by oceans, the influence of land and water on the climate is very clearly observed within its limits, and in particular the influence of warm and cold ocean currents. The direction of winds is not constant; western winds prevail; cyclones and anticylones move from west to east and bring with them either clear or rainy weather. The temperate climate is divided into 7 subgroups: taiga climate, deciduous forest climate, steppe climate, Mediterranean climate, subtropical forest climate, temperate desert climate, subtropical desert climate. -1. Taiga climate, or Siberian climate, extends from the polar circles to 60° N. lat., i.e. it covers the northern part of the European part of the USSR up to the line Leningrad-Nizhny Novgorod, almost all of Siberia up to 57° N. lat., almost all of Finland, Sweden, and North America up to the Great Lakes. It is characterized by a warm short summer with an average summer temperature from 10° to 20° and a severe winter. The annual amplitude is not less than 10°, which indicates the continental nature of the climate. Moderate precipitation (300-600 mm per year) and moderate humidity. The Siberian climate is divided into a) West Siberian - from the Urals to the Yenisei River, differing in cloudiness and significant precipitation in winter (snow), and b) East Siberian - with little cloudiness and a large number of hours of sunshine, with a severe, dry, and little snowy winter with weak winds. In Transbaikalia the Siberian climate turns into steppe climate, and taiga into steppe. -2. Deciduous forest climate of the temperate zone, or oak climate, is less continental than the Siberian one: winter here is also snowy but milder; summer is warmer, with an average temperature of the four warmest months above +10° but below +22°; summer is rainy but not frequently. Soils are podzolic loams and in the south chernozem (rye and wheat are cultivated). Forests are predominantly deciduous with falling leaves, among which oaks are often found, and in Western Europe - beeches, which require more moisture. The oak climate is found in the forest part of the USSR south of the line Leningrad-Nizhny Novgorod to the southern border of the forest-steppe and in the east - to the Urals, in southwestern Siberia, the Minusinsk steppes, along the middle course of the Amur, in the Ussuri region, Manchuria, North China, southern Sakhalin, northern Japan, in America - in the Great Lakes region - and in Western Europe. In the southern hemisphere it is similar to the climate of southern Chile and the South Island of New Zealand, but here it is much milder and with abundant precipitation. - 3. Steppe climate. In temperate latitudes, steppe climate is found in the southern steppes of the European part of the USSR, in the northern part of Kazakhstan, in Transbaikalia, Mongolia, in the western states of America, etc. The steppe climate of temperate latitudes is characterized by a cold winter and a warm and dry summer with temperatures not below +20° and not above +23¹/₂°, with 200-450 mm of annual precipitation, with a maximum of rainfall in June and July. In the southern Russian steppes, dry southeast and east winds, so-called dry winds, often blow, during which the relative humidity drops to 15%. These winds sometimes reach a speed of 16 m per second. Soils in the steppes consist mainly of chernozem (in the northern zone) and of chestnut chernozem (in the dry southern steppes). Soils impregnated with salt are often found: solonchaks (surface) and solonetz (deeper). 4. Mediterranean climate already belongs to the subtropical. It is characterized by a warm and humid winter, and a hot and dry summer. In the northern hemisphere, dry northeast trade winds blow in summer, and in winter - western winds with precipitation. This climate is characteristic of the Mediterranean coast and also of the Black Sea coast (from Novorossiysk to Dzhubga), the southern coast of Crimea, California, and Southern Australia. It is characterized by forest and shrub vegetation, among which there are many evergreen species. In addition to these main forms, varieties are distinguished in the Mediterranean climate: a) subtropical steppe climate along the northern coast of Africa (northern part of the Sahara), in Arabia, Mesopotamia, inside Asia Minor, in southern Persia, and in the southern part of Australia; here the places are dry and hot, moderate rains in winter; the steppes are covered with shrubs; b) Mediterranean climate with cool summer - found along the coast of California (San Francisco), in Oregon, in central Chile, in Southern Australia, and at the Cape of Good Hope. 5. Subtropical forest climate with hot (up to 23-24°) and very rainy summer, with dry winter - average temperature above +2°; rich subtropical vegetation: hornbeams, ashes, chestnuts, yews, etc., cultivation of tea (Chakva station near Batumi), corn, rice, and cotton. Soils are insufficiently studied: many alluvial, semi-boggy, and boggy soils (valley of the Rion, Poti, etc.), relict red soils (laterites) are found. In the USSR, the zone of subtropical forests includes: the southern part of the Black Sea coast of the Caucasus (from Tuapse to Batum), the southern part of the western coast of the Caspian Sea (Lankaran).

The warmest place on the Black Sea coast is Gagra (average annual temperature +15.1°), and the rainiest is Batumi (2,529 mm of precipitation per year); the maximum precipitation in Batumi falls in November (327 mm) and the minimum in May (37 mm); the average annual temperature in Batumi is +14.5°, July +23.1° and January +6.4°. The water temperature in the Black Sea near Batumi is +10° in January and +24.5° in August. Greenery does not disappear year-round. Mandarins, oranges, and lemons ripen in the open air. In the Batumi region, snow falls only as an exception in winter. In Lenkoran on the southwestern coast of the Caspian Sea, the climate is even hotter: July +25.6°, January +2.8°, but somewhat drier than in western Transcaucasia; nevertheless, about 1,200 mm of precipitation falls here per year, mainly in September and October. The winds are of the monsoon type. The vegetation consists mainly of oak, chestnut, ironwood (Parrotia persica), maple, alder, and others. 6. Climate of the interior deserts of the temperate zone. This type of desert includes: the southern Kazakh steppes, the deserts of western Turkestan, the semi-deserts (transition from steppes to deserts) of the Astrakhan region, the Terko-Kumskaya (along the Kuma River), the American desert along the middle course of the Colorado, and some others. The climate is dry, with little precipitation (300 mm per year or less); summer is sunny, hot (up to 35°), without rain; winter is cool - January below +2.0°, snow falls but does not last long. There are many winds (which is why the climate of these deserts is called the 'climate of blizzards', as well as the Aral climate and the saxaul climate); cyclones bring moisture in winter and spring; occasionally heavy rains fall (100 mm). The soils of deserts and semi-deserts are brown and gray, covered with black wormwood (Artemisia pauciflora), fescue (Festuca ovina), and other sparse vegetation, which changes seasonally. 7. Climate of subtropical deserts in the trade wind regions (climate of the simoom, Sahara, or date palm). These include the Sahara, the Arabian Desert, the desert of the southwestern coast of Africa between 18° and 30° south latitude, the desert of India, Australia, Colorado, Atacama. The climate is dry, hot. Winter is warm, with temperatures not below +10°; daily temperature amplitudes are very large. There is little vegetation, and it covers the deserts only in places (oases). In the central parts of the Sahara, the average temperature in July is 32-36.5°, reaching up to 50° and higher, but frosts down to -5° and snow occur. In some parts of the Sahara, there are no rains for several years. The southern border of the Sahara runs along 18-20° north latitude and coincides with the northern border of tropical rains. The subtropical deserts of America (Peru, Chile) and the western coast of Africa are characterized by frequent winter fogs. The climate of the American prairies with their relatively cold winter also belongs here. Tropical climate is characterized by the high position of the sun: on the tropics, on the shortest day, the sun rises above the horizon at 43°, and at the equator at noon it never falls below 66.5°. The temperature, like the length of the day, is distributed evenly throughout the year and does not characterize the seasons; therefore, the amplitude of temperature fluctuations is very small. The year is divided into two periods: rainy (winter) and dry (summer). In the tropics, not only the climate but also the weather is so stable that these two concepts coincide. The soil in the tropics, at shallow depths, has a constant temperature of 22-29° and, together with the high content of water vapor in the air, prevents air cooling. The tropical climate has a maritime character, since under the tropics land occupies about 1/4 and oceans about 3/4 of the area. A good example of tropical climate is the climate of the Congo under 6° south latitude; the annual temperature amplitude here is less than 1° (February 24.3°, December 25.1°), but the daily amplitude is quite significant: in July more than 16°, and in April-October - 12°. On the Marshall Islands, the daily amplitude averages 7.5°. Barometric annual fluctuations are less than 1 mm (Batavia), daily ones are regular and significant. The winds are trade winds and monsoons. The cessation of trade winds or the beginning of monsoons coincides with the beginning of the rainy season of the year. Near the equator, two rainy periods with thunderstorms are observed. In equatorial latitudes, zones of calm are also observed. The tropical climate is divided into 1) climate of tropical forest-steppe, or savannas, and 2) climate of humid tropical forests. 1. In the climate of savannas lie: Venezuela, part of Guiana, part of the coast of Central America, Brazil (south of the Amazon River), most of tropical Africa, the western part of the island of Madagascar, most of Siam, the Deccan, the northern part of Australia, the Hawaiian Islands. The climate is tropical, with the temperature of the coldest month above 18°, precipitation is abundant (2,000-2,500 mm); there are dry and rainy periods of the year. The vegetation is steppe with groves of low trees that shed their leaves in the dry season. Only in Africa do giant baobabs grow in this zone. The winds are tropical cyclones, sometimes with enormous destructive force. 2. Climate of humid tropical forests. The region of the Amazon River and a few degrees north and south of it, the eastern coast of Brazil, the eastern part of Central America, the Greater Antilles, southern Florida, tropical central and western Africa, the eastern coast of Madagascar, the Malabar coast, southern Ceylon, Malacca, the Indo-Malay archipelago, most of the Philippine Islands and Guinea. The temperature of the coldest month is not below +18°, with small annual amplitudes from 1° to 6°. Rains fall year-round (up to 1,500 mm per year). The vegetation is evergreen virgin forests, entangled with lianas. Maritime and continental climate. The distance of a place from the oceans has a huge influence on the character of the climate. The difference between maritime and continental climate is visible from the following table. Location Average annual temperature January temperature July temperature Iceland Moscow Dublin Astrakhan 4.12° 4.46° 9.46° 0.01° -1.21° -10.24° -3.60° -10.75° 13.44° 19.11° 15.95° 24.98° 14.65° 29.35° 19.15° 35.73° Maritime Continental Maritime Continental Maritime climate is characterized by mildness: winter is warmer, and summer is colder than continental climate. The difference between January and July temperatures is less than on the continent. On continents, summer is hot, winter is severe, and the amplitude of annual temperature fluctuations is very large. In the same direction, large lakes, e.g. Baikal, also influence the climate. The features of maritime climate depend on the higher heat capacity of water compared to land (almost twice); therefore, the soil cools twice as fast in winter as water, and the latter plays a warming role relative to land and air. Warm ocean currents make the countries they wash warmer, e.g. the Gulf Stream - England and Norway, while cold currents, in winter - from land to ocean, and in summer - from ocean to land. The monsoons of the eastern coasts of Asia go far north from the south to the Sea of Okhotsk and Kamchatka. Monsoon-type winds are also observed on the Black Sea coast of the Caucasus: in winter from land - NE and E, and in summer from the sea - SW, which is explained by the increased barometric pressure in winter on the Central Caucasus and in Armenia (anticyclone) and a decrease - on the Black Sea (cyclone), and in summer by the fact that the pressure over the sea is generally higher than over land. Maritime climate has a special effect on forest vegetation: in coastal areas, the July isotherm at +10°, running around 62° north latitude, is the limiting line for the latitudinal spread of the forest, whereas in the continental climate, e.g. in northern Siberia, forest vegetation reaches 67.5° north latitude (Verkhoyansk), because here the July temperature is +15°; similarly far north in Siberia go the zones of steppes and deserts. The reasons for these differences are seen in the hot summer on the continents and the relatively low summer temperature at the corresponding latitudes of the maritime climate. Countries with maritime climate, e.g. England, Ireland, are mostly covered with meadows. Seeds, tubers, and roots of plants in maritime climates are richer in starch. Continental cereals are richer in protein (nitrogen). Mountain climate. The altitude of a place above sea level creates special climatic conditions, which are summarized in the concept of mountain climate, or vertical climatic zones. As one ascends into the mountains, the temperature decreases, and on the tops of high mountains there is eternal snow. The decrease in temperature with ascent into high mountains is evident from the following example. Conversely, they are colder, for example Kamchatka, Sakhalin, the eastern part of North America, etc. The relative humidity in summer gradually decreases as one moves away from the oceans inland. For example, near the oceans the annual relative humidity is 86-90% (mouth of the Amazon), while in deserts it decreases to 5% (Nukus on the Amu-Darya) and even to 1% (southeastern Mongolia). Cloudiness and the number of cloudy days also distinguish maritime climate from continental. The smallest number of clear days per year is observed on the Kola Peninsula (only 9-15), and the largest (260) - on the Amu-Darya (Termiz). In Central Asia and in Transbaikalia, the largest number of hours of sunshine per day is 7.1 hours (in Chita), while in northern Scotland only 3.1 hours. In the distribution of precipitation, the same regularity is not always observed as with humidity and cloudiness, because the influence of the terrain's relief and the general circulation of the atmosphere is added to the influence of water and land. For example, from the Black Sea northward, and from the Arctic Ocean southward, the amount of precipitation increases rather than decreases.

In the latter case, the influence of continental swamps and forests, which enrich the atmosphere with moisture, is evident. The annual distribution of precipitation in maritime and continental climates is not the same: in the oceans at middle and high latitudes and on the coasts, autumn and winter rains prevail, while on continents they are summer (mostly daily). On coasts with flat shores, less precipitation falls, and thunderstorms and downpours are rarer and weaker. Land and water have a great influence on the speed, constancy, or variability of winds, i.e., generally on atmospheric circulation. An uneven surface of the land reduces wind speed; therefore, over oceans and seas, wind speeds are greater than over continents. Wind speeds decrease from the coasts inland, and in some places they completely die down (for example, the Verkhoyansk district in northeastern Siberia, where in winter complete calm and silence are observed). In continental climates, the wind intensifies toward noon and subsides by evening (until morning), especially in steppes and deserts (Central Asia, Tibet, etc.). On the shores of seas and oceans, coastal winds—breezes—periodically blow: during the day from sea to land, and at night from land to sea; breezes are particularly distinct in the tropics, but are also noticeable in temperate latitudes, for example, on the Baltic, Caspian, Black seas, on Ladoga, Onega and other large lakes. In Batumi and Novorossiysk, breezes blow from April to September, while in Sukhumi they blow year-round. The cause of breezes is the uneven heating of land and water and the different cooling rates of the latter: during the day, the air over the shore heats up faster and more strongly than over the sea, rises upward, and therefore colder air from the sea moves toward the land; at night, the same factors act in the opposite direction: the air over the land cools down faster than over the sea, and as it were, slides from the land to the sea, displacing the warmer and lighter sea air. For the same reason, on the shores of the Indian Ocean and in eastern Asia up to 60° N latitude, monsoons blow: One of the volcanoes in the Cordilleras under 5° north latitude. Height in meters...... 1,050 2,861 4,070 4,500 Temperature.....27.05° 23.70° 15.50° 3.40° 1.60° Depending on the latitude of the area, air currents, time of year, and some other local conditions, the rate of temperature decrease with ascent per 100 m varies within 0.5°-0.7°. For the same reasons, the snow line on mountains lies at different altitudes: in Norway—at 720 m, in the Alps—2,400 m, in the southern Cordilleras—4,500 m. The decrease in mountain air temperature with ascent is influenced by the slight heating of the air by passing sun rays, distance from the warming effect of the earth's mass, the presence of snow and glaciers, winds, and the absorption of heat by ascending air currents. The daily and annual temperature amplitudes in the mountains are very significant due to strong insolation of rocks during the day and their rapid cooling due to radiation*—by evening and night; therefore, the mountain climate is quite severe and requires the organism to have a certain reserve of strength for adaptation. Then, a feature of the mountain climate is the decrease in barometric pressure with altitude, as seen in the following table. Heights in meters 0 500 1,000 2,000 3,000 4,000 Pressure at 0° C in mm...... 760 716 671 590 517 452 Pressure at 25° C in mm-. ... . 762 720 679 604 536 475' With decreasing pressure, the content of O₂ in the atmosphere also decreases: from 20.7% at sea level to 12.4% at 4,000 m altitude, to 9.3% at 6,000 m, and to 6.9% at 8,000 m (the latter altitude corresponds to a pressure of 278.8 mm mercury). The effect of decreased pressure and lack of O₂ when ascending a mountain in the Alps begins to manifest itself already at an altitude of 3,000 m in the form of a pathological symptom complex known as 'mountain sickness,' but under the influence of training and acclimatization, tourists and mountain dwellers do not suffer from this disease and ascend to the highest peaks at 5,000-6,000 m. Pilots without oxygen apparatus can ascend and fly at altitudes not exceeding 5,000 m, i.e., at a pressure of about 406 mm and oxygen content of about 12%. Cities and villages are sometimes located very high, for example, at altitudes of 4,165 m (city of Potosi), 4,760 m (pass through the Andes—barometric pressure equals 420 mm) and even 5,210 m (southern Peru—pressure 390 mm). In the Alps, permanent settlements do not rise higher than 2,000-2,500 m, i.e., up to the upper limit of grain cultivation. In the Caucasus, the highest-located settlement (Kurush in Dagestan) is at an altitude of 2,480 m. As for absolute humidity, it decreases with altitude faster than pressure, and mountain air is characterized by dryness. Relative humidity changes irregularly with altitude and reaches its greatest value at the cloud formation level. The amount of precipitation in the mountains only partially increases with altitude and largely depends on local conditions, for example, on winds, orientation relative to the cardinal points, etc. Due to differences in relief (ravines, peaks, convex slopes, hollows) and in position relative to the sun, in the mountains, sunny and shaded areas alternate very frequently, and with this, climatic conditions change over relatively small distances. Northern and southern mountain slopes differ particularly sharply in climate. Vegetation changes with ascent in the same order as when moving from the equator toward the poles, as seen in the following example: the western slope of the Fergan Range in the former Andijan district (Central Asia, 40° N lat.). The foot of the range is in the desert zone. 1. At an altitude of 500-700 m lie wormwood-solonchak lowlands—deserts; with intensive artificial irrigation, cotton, rice, barley, millet, and wheat are cultivated. 2. At an altitude from 700 to 1,100 m (1,200)—uplands (adyrs), semi-desert; the soil is plowed without artificial irrigation, but not always with a harvest; vegetation is wormwood-grass, spring and summer; soil—sierozem; thickets—pistachios. 3. From 1,100 to 1,600 m—grass steppe with dark sierozem; wheat and other grains grow; in ravines, trees appear: apple, walnut, etc.; this zone corresponds to the chernozem belt of the USSR. 4. From 1,500 to 1,700 m—forest-steppe: plums, walnuts, apples; in clearings—grass steppe and meadows; soils are similar to loam; watermelons and wheat grow without artificial irrigation. 5. From 1,700 to 2,500-2,700 m—meadow steppe; soil resembles chernozem; vegetation: feather grass (Stipa capillata), wormwood (Artemisia maritiraa); in the upper zone of the steppe—small groves of spruce (PiceaSchrenkiana), thickets of arborvitae (Juniperus), and in valleys—maple, poplar, birch. 6. From 2,700 to 3,000 m and higher—high-mountain meadows ('alpine meadows'); at altitudes above 3,000 m, feather grass is found; soils are mountain-meadow. 7. Above 4,000 m on the Fergan Range lies the snow line.—Thus, depending on the decrease in temperature and precipitation with ascent, the same change of zones occurs as on plains when moving from south to north: desert, semi-desert, grass steppe, meadow steppe, spruce and arborvitae groves, and high-mountain meadows. The zone of agriculture reaches here an altitude of 2,500 m, and loess soil rises to 3,000 m. In mountain valleys, the air heated during the day rises to the mountains, while at night cold air flows down. In addition to these daily changes in winds, in mountainous areas a peculiar dry and warm wind is observed, known in the Alps as 'foehn.' Foehns are frequent in the Caucasus Mountains: in Gagra, Kutaisi (up to 114 days a year), Tiflis, etc. During a foehn in Gagra, the temperature rises to +28°, and relative humidity decreases to 15-10%; the direction of the foehn is southeast; foehns make the atmosphere suffocating. They are known on the southern coast of Crimea (from the northeast and east) and on the southern coast of the Caspian Sea. In contrast to the foehn, on steep coasts of the Black Sea (Novorossiysk) and the Adriatic (Dalmatia and Istria), a cold northeast wind 'nordost,' or 'bora' blows (in Baku—'nord,' in the Rion Valley—'mistral' from the southwest, on Baikal—'sarma' from the southwest and northwest). Climate of high plateaus. High plateaus (plateaus) are flat elevations lying not lower than 1,000 m above sea level. Their climate is similar to the climate of surrounding lowlands, but with a correction for the corresponding altitude of the area. The climate of plateaus is unstable, has large temperature amplitude fluctuations, and depends on the latitude at which the plateau is located. Examples of polar ice plateaus can be Greenland and Novaya Zemlya—near the North Pole, Antarctica—near the South Pole. In the temperate zone lies the vast plateau of northwestern Mongolia with an altitude of up to 1,370 m. This plateau belongs to the type of steppes and deserts of the temperate climate. The Armenian Highland (1,400-2,100 m) also belongs to this type. Eastern Turkmenistan to the east of Pamir, lying on average at an altitude above 1,000 m, is an example of a plateau-plain with the type of deserts of temperate latitudes, enclosed on all sides (except the east) by mountains. The climate is dry with negligible precipitation. Examples of very high plateaus are Tibet and Pamir, located at altitudes of 3,500-4,000 m. Their climate is characterized by cool summers and large daily and annual amplitudes.

High plateaus in the tropical climate exist in America (Chile, Peru, Ecuador, Mexico) and in Africa (Abyssinia and southwestern Africa). Their climate is characterized by tropical uniformity and alternation of rainy and dry periods during the year: they lie at an altitude of 3,000 m and higher. Daily temperature fluctuations are very great. The vegetation ranges from desert to savanna vegetation, i.e., forest-steppes. Climate and human activity. Human cultural activity has a noticeable influence on the climate through the construction of large settlements and cities, the destruction of the natural forest and grass cover of the soil, artificial irrigation of deserts and drainage of swamps. Forest fires and 'burnings' (deliberate burnings) in Siberia for the preparation of forest plots for plowing create masses of black smoke, which sometimes covers areas of several million km² and remains in the air for weeks. The smoke weakens solar radiation by 35-50% and thereby extends the growing season of cereals by 10-15 days. Over forest fires with significant air humidity, clouds form, from which rain eventually falls, sometimes with strong wind and thunderstorms (in savannas). The destruction of forests followed by plowing with little snow cover (less than 10 cm) increases the amplitude of soil temperature by 30%. In summer, the temperature on plowed fields is higher than on virgin land; in winter, on virgin land it is higher than on plowed fields, since the natural vegetation cover prevents the free circulation of cold air in the soil. Further, the loosening of the upper layer of soil by cultural cultivation contributes to the formation of black dust and dust storms in the chernozem zone of the European USSR and in Central Asia. The dust formed in large cities and the fine soot and smoke emitted by factories and factories contribute to the formation of fogs over industrial cities and entire districts and weaken the intensity of solar radiation. Artificial irrigation, on the contrary, creates a special humid climate in the deserts, corresponding to precipitation of 400-600 mm per year. Often, in this case, the development of severe forms of malaria is observed (Tashkent and other areas). Finally, one can speak of an urban climate, which differs from the climate of the surroundings in many respects: temperatures in large cities in summer and winter are 0.5° higher (in Moscow, Vienna, Berlin) and 0.75° higher (in Paris), especially in the evening, because the buildings heated during the day radiate heat in the evening and at night. The relative humidity in cities is less. The urban climate has apparently warmed by 1-3.5° over the last 100 years. There are more foggy days in cities than in the surroundings, because dust promotes the condensation of water vapor into fog. Finally, urban structures moderate the force and change the direction of winds. If man influences the climate, then the climate even more strongly influences man, his health, morals, and customs. Thanks to the great adaptability of the human race, man can live both at +70° (Africa) and at -63° (northern Siberia), i.e., with a temperature amplitude of up to 133° with daily fluctuations of 20-26° (Tibet, Siberia) and with relative humidity from a few percent (Sahara) to 100%. In adapting to temperature changes, man's cultural acquisitions have helped him greatly: clothing and housing. Nevertheless, different climates are not equally well tolerated by people. Especially poorly tolerated by Europeans are the tropical and partly subtropical climates, if in them high temperature, high humidity, and calm are combined at the same time, as is the case, for example, on the southeastern coast of Africa, in the tropical forests of America, in India and some other countries. In these climates, Europeans, due to the difficulty of heat dissipation by the body, lose their ability to work and during physical exertion are easily subjected to heat and sunstroke. In the extreme north, the severe winter is relatively easily tolerated because during frosts the air is dry and there is no wind; these conditions reduce heat loss from our body. In all latitudes, people more easily tolerate a moderate climate: mild, even with minimal amplitudes of daily and annual fluctuations of temperatures and other climatic factors (see Acclimatization).