THE LECTURE by liaoqinmei

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									 THE HYGIENE OF HOT COUNTRIES. CLIMATES AND ACCLIMATIZATION

Odessa State Medical University
Vorokhta Y.
.
Human organism exists constantly interacting with the environment, one of the most important
componrnts of which is a climate. Tropic Hygiene is marked out as a special field of Hygiene
owing to the fact, the climate of tropics has a great influence upon the hygienic life conditions and
the conditions of human health.
The climate is a long-term weather regime, corresponding to the geographical country and
repeating appropriately.
The weather is a complex of physical features of the nearland atmospheric layer during a relatively
short period of time (hours, days, weeks). The weather is characterized by the complex of
meteorological elements: solar irradiation, temperature, humidity, air speed and direction,
atmospheric pressure, electrical condition of the atmosphere, cloudiness and the presence of
precipitations.
Consequently, the weather is a changeable process, as the climate is stable one and it has a
prolonged influence upon human organism.
Main climate-forming factors are: the latitude of the country and the intensity of solar irradiation,
depended on it, the appropriateness of atmospheric circulation, the type of land surface (dry land,
relief, water and so on), the closeness of seas and oceans.
Climate-weather conditions have a direct or mediated influence upon people. The examples of
direct influence are: the action of weather conditions upon human heat exchange, ultra-violet rays
of solar tadiation - upon the exchange of calcium. The last is a very important thing for the
prophylaxis of rachitis.
Mediated action of climate is connected with the influence upon the character of human household
and working activity, upon the pathological agents of infectious diseases and their carriers. The last
fact conditions the geographical specificity of spread of different diseases. That's why, region's
climatic conditions must be taken into consideration during the working out of hygienic
recommendations for the civil (living houses, hospitals) and industrial building, rational
nourishment and way of life, for the choice of adequate clothes and footwear, work and rest
regimen, prevention of diseases and education of the future generations. In his "Aphorisms"
Hyppocratus said, that the diseases proceeded differently in different climatic conditions. He
offered climate therapy for the treatment and health improving, which was widely practiced at
present.
Usually certain climate is spread over the large area about hundreds and even thousands kilometres.
However, some regions of this large area can differ by their climate-weather conditions from other
ones. That's why, such a notion as microclimate was approved in climatology (the science about the
Earth's climate). It means the features of physical condition of the nearland layer above relatively
small plot of land. So, we can say about the microclimate of the wood, field, sea-coast, mountain
slopes, oriented to the parts of the world differently, about the microclimate of vale, town, street
and so on.
Now, many sciences, adjoining to the climatology, are developed. Medical climatology learns the
influence of climate-weather conditions upon the human organism and works out the methods of
use of climatic factors with the treatment and prophylactical aim. Medical geography learns the
appropriatnesses of influence of climatic and social-economic conditions upon hygienic life
conditions, health conditions and the features of infectious and non-infectious diseases' spread in
different geographical regions. The materials of investigations are widely used in the working out
and planning of corresponding programs and prophylaxis.
From the medico-geographical point of view tropics are the part of earth's surface, placed in the
equatorial (from latitude 10 degrees North to latitude 20 degrees South), torrid (from latitude 10 to
20 degrees North and from latitude 10 to 20 degrees South) and subtorrid zones (from latitude 20 to
30 degrees North and from latitude 20 to 30 degrees South).
Medical climatology considers the climate of these zones as tropical. Tropics contain a
considerable part of dry land, almost whole Africa, Southern Asia and the south of East Asia, a
large part of Latin America, Oceania. More than a half of people live in this part of Earth. The
transitional zone adjoins to the torrid zone (Mediterranean region, Front and Middle Asia, the south
of USA, some regions of the Far East). They are characterized by the features of torrid and
temperate zones.
                                Tropical Rainforest (Af)




Lat/Long = 3.39o S, 73.18o W
Average Annual Temperature (oC) = 26.1
Annual Temperature Range (oC) = 1.4               Bromelias with emerging crown
Total Annual Precipitation (mm) = 2879.2          (Peru)
Summer Precipitation (mm) =1583
Winter Precipitation (mm) = 1294.7
Geographic Distribution
     Amazon Basin,
     Congo River Basin,
     East coast of Central America,
     East coast and interior of Brazil,
     East coast of Madagascar,
     Malaysia,
     Indonesia,
     Philippines.
Controlling Factors
High year-round insolation and precipitation of ITCZ.
Rising air along trade wind coasts.
mE air masses.
Tropical Monsoon Climate (Am)




Lat/Long = 12.53o N, 74.52o E
Average Annual Temperature (oC) = 27.05         Farmer cutting eucalyptus in wood lot, Myanma
Annual Temperature Range (oC) = 3.6
Total Annual Precipitation (mm) = 3409.2
Summer Precipitation (mm) = 3115.9
Winter Precipitation (mm) = 293.3
Geographic Distribution
     Coastal areas of southwest India,
     Sri Lanka, Bangladesh, Mynamar (Burma),
     Southwestern Africa,
     French Guiana,
     northeast and southeast Brazil.
Controlling Factors
Summer onshore/winter offshore air movement related to shifting ITCZ or monsoon circulation.
mE air masses during high-sun; stable mT or cT -> low-sun
                           Wet Dry Tropical Climate (Aw)




Latitude/Longitude = 14o N; 17o W
Average Annual Temperature (oC) = 24.5
Annual Temperature Range (oC) = 7.1
Total Annual Precipitation (mm) = 578
Summer Precipitation (mm) = 516                  A Baobab tree, with its thick
Winter Precipitation (mm) = 62                   trunk and large edible fruit,
                                                 Dakar, Senegal.
Geographic Distribution
    Northern and eastern India, interior Myanmar (Burma) and Indo-Chinese
        Peninsula;
    northern Australia; south central Africa; Ilanos of Venezuela, Campos of
        Brazil;
    Western Central America; south Florida, and Caribbean Islands.
Controlling Factors
Shifting influence of high-sun ITCZ and low sun STH influence.
High sun mE air masses; low-sun cT air masses
                             Tropical Desert Climate (BWh)




                                                         Caravan of camels in the Grand Erg Desert of
                         o      o
Latitude/Longitude: 27.7 N; 8.1 W                        Algeria.
Average Annual Temperature (oC) = 22.8
Annual Temperature Range (oC) = 21.2
Total Annual Precipitation (mm) = 43.8
Summer Precipitation (mm) =11.8
Winter Precipitation (mm) = 32
Geographic Distribution
     coastal Chile and Peru
     southern Argentina                            Characteristics
     southwest Africa                              Among the driest places on earth
     north Africa                                  Mean annual temperature above 64.4o F (18oC)
     Arabia, Iran                                  Low relative humidity
     Pakistan, and western India;                  Irregular and unreliable rainfall
     Baja California and interior Mexico           Highest percentage of sunshine of any climate
Controlling Factors                                 Large diurnal temperature range
Descending, diverging, circulation of subtropical   Highest daytime temperature of any climate
highs                                               Annual precipitation less than half the annual
Continentality linked often with rain shadow        potential evapotranspiration
location.
cT air masses
                             Tropical Steppe Climate (BSh)




Latitude/Longitude: 16.25oS N; 133.3oE
Average Annual Temperature (C) = 26.5o            Cattle drinking from a river bank in the tropical steppe of
Annual Temperature Range (C) = 10o                Ethiopia.
Total Annual Precipitation (mm) = 536.2
Summer Precipitation (mm) =500
Winter Precipitation (mm) = 36.2
Geographic Distribution                            Characteristics
Peripheral to deserts especially in:               Semiarid
     Australia                                    Annual rainfall distribution similar to nearest
     northern and southern Africa                 humid climate
     southwest Asia                               Annual precipitation more than half, but less than
     Argentina                                    annual potential evapotranspiration
     western United States                        Mean annual temperatures above 64.4oC (18oC)
Controlling Factors
Descending, diverging, circulation of subtropical
highs
Continentality linked often with rainshadow
location.
cT;mT
                         Humid Subtropical Climate (Cfa)




Latitude/Longitude = 35o N; 90o W
Average Annual Temperature (oC) = 17
Annual Temperature Range (oC) = 22
Total Annual Precipitation (mm) = 1222            The Sinks. Great Smokey Mountains, TN.
Summer Precipitation (mm) = 536                   The ample precipitation and generally mild
Winter Precipitation (mm) = 686                   temperatures of the humid subtropical climate
                                                  support a lush environment of temperate
                                                  deciduous to temperate evergreen forests.
Geographic Distribution
    Southeastern U.S.
    southeastern South America;
    coastal southeast South Africa;
    eastern Australia;
    eastern Asia from northern India through south China to Japan.
Controlling Factors
East coast location between 20o and 40o N anl S latitudes.
Humid (mTu air masses) onshore air movement in summer.
Cyclonic storms in winter (cP air masses)
     Mediterranean or Dry Summer Subtropical Climate (Csa, Csb)




Latitude/Longitude = 37.45o N; 122.26o W                      Small, thick evergreen leaves of the schlerophyll
Average Annual Temperature (oC) = 13.75                       forest combats water loss during the drought
Annual Temperature Range (oC) = 9                             conditions of the dry summer found in the
Total Annual Precipitation (mm) = 475                         Mediterranean climate. The picture depicts a
Summer Precipitation (mm) = 54                                schlerophyll scrub forest in the subalpine zone in
Winter Precipitation (mm) = 421                               New Zealand.
Geographic Distribution                                     Characteristics
      Central California                                   Mild, moist winters, hot dry summers inland
      central Chile                                        Cool, often foggy coasts
      Mediterranean Sea borderlands                        High percentage of sunshine
      Iranian Highlands                                    High summer diurnal temperature range
      Capetown area of South Africa                        Frost danger during winter
      southwestern Australia
Controlling Factors
West coast location between 30o and 40o N and S
latitude.
Alternating between Subtropical High in summer
and Polar Front/Westerlies in winter.
Cyclonic precipitation during the winter.
Summer air masses: mTs, cT
Winter air masses: mT,mP, cP
 Köppen Climate Classification System
The Köppen Climate Classification System is the most widely used for classifying the world's climates. Most
classification systems used today are based on the one introduced in 1900 by the Russian-German climatologist
Wladimir Köppen. Köppen divided the Earth's surface into climatic regions that generally coincided with world
patterns of vegetation and soils.
The Köppen system recognizes five major climate types based on the annual and monthly averages of temperature and
precipitation. Each type is designated by a capital letter.
A - Moist Tropical Climates are known for their high temperatures year round and for their large amount of year round
rain.
B - Dry Climates are characterized by little rain and a huge daily temperature range. Two subgroups, S - semiarid or
steppe, and W - arid or desert, are used with the B climates.
C - In Humid Middle Latitude Climates land/water differences play a large part. These climates have warm,dry
summers and cool, wet winters.
D - Continental Climates can be found in the interior regions of large land masses. Total precipitation is not very high
and seasonal temperatures vary widely.
E - Cold Climates describe this climate type perfectly. These climates are part of areas where permanent ice and tundra
are always present. Only about four months of the year have above freezing temperatures.
Further subgroups are designated by a second, lower case letter which distinguish specific seasonal characteristics of
temperature and precipitation.
f - Moist with adequate precipitation in all months and no dry season. This letter usually accompanies the A, C, and D
climates.
m - Rainforest climate in spite of short, dry season in monsoon type cycle. This letter only applies to A climates.
s - There is a dry season in the summer of the respective hemisphere (high-sun season).
w - There is a dry season in the winter of the respective hemisphere (low-sun season).
To further denote variations in climate, a third letter was added to the code.
a - Hot summers where the warmest month is over 22°C (72°F). These can be found in C and D climates.
b - Warm summer with the warmest month below 22°C (72°F). These can also be found in C and D climates.
c - Cool, short summers with less than four months over 10°C (50°F) in the C and D climates.
d - Very cold winters with the coldest month below -38°C (-36°F) in the D climate only.
h - Dry-hot with a mean annual temperature over 18°C (64°F) in B climates only.
k - Dry-cold with a mean annual temperature under 18°C (64°F) in B climates only.




                             HIGHEST TEMPERATURE EXTREMES
                  Continent        Highes Place          Elevatio Date
                                   t Temp                n (Feet)
                                   (°F)
                                          El Azizia,              September
                  Africa           136                   367
                                          Libya                   13, 1922
                                          Greenland
                  North America    134    Ranch, Death -178       July 10, 1913
                                          Valley, CA
                                          Tirat Tsvi,
                  Asia             129                   -722     June 21, 1942
                                          Isreal
                                          Cloncurry,              January 16,
                  Australia        128                   622
                                          Queensland              1889
                                                                  August 4,
                  Europe           122    Seville, Spain 26
                                                                  1881
                                          Rivadavia,              December 11,
                  South America    120                   676
                                          Argentina               1905
                                          Vanda
                                                                  January 5,
                  Antarctica       59     Station, Scott 49
                                                                  1974
                                          Coast
      HIGHEST ANNUAL PRECIPITATION EXTREMES
     Continent       Highest Place         Elevatio Years
                     Average               n (Feet) Of
                     (Inches                         Recor
                     )                               d
                              Lloro,
                     524                   520       29
                              Columbia
     South America
                              Quibdo,
                     352                   120       16
                              Columbia
                              Mawsynram
     Asia            467                   4,597     38
                              , India
                              Mt.
     Ocean           460      Waialeale, 5,148       30
                              Kauai, HI
                              Debundscha,
     Africa          405                   30        32
                              Cameroon
                              Bellenden
     Australia       340      Ker,         5,102     9
                              Queensland
                              Henderson
                              Lake,
     North America 256                     12        14
                              British
                              Columbia
                              Crkvica,
     Europe          183      Bosnia-      3,337     22
                              Hercegovina
       LOWEST ANNUAL PRECIPITATION EXTREMES
Continent       Highest Place           Elevatio Years Of
                Average                 n (Feet) Record
                (Inches
                )
South America 0.03       Arica, Chile 95          59
                         Wadi Halfa,
Africa          0.10                    410       39
                         Sudan
                         Amundsen-
Antarctica      0.8      Scott South 9,186        10
                         Pole Station
                         Batagues,
North America 1.2                       16        14
                         Mexico
Asia            1.8      Aden, Yemen 22          50
                         Mulka, South
Australia       4.05                  160        42
                         Australia
                         Astrakhan,
Europe          6.4                   45         25
                         Russia
                         Puako,
Ocean           8.93                  5          13
                         Hawaii, HI
We must comprehend the hygienic meaning of separate meteorological elements (climate-weather
factors) to understand the many-sided influence of tropical conditions upon the human life activity
and health.
HYGIENIC MEANING OF CLIMATE-WEATHER FACTORS IN HOT COUNTRIES
  Hygienic meaning of solar radiation in tropical conditions.
The sun is the origin of heat, light and power for the biosphere. Solar power forms air currents and
the change of weather, connected with them. It determines the climate of the country and makes the
existence of organic life possible. Food contains the power of sun, at the expense of which we live.
Besides, people live in the environment full of sun rays for many thousands of years. They adapted
to use sun power through the skin, which became necessary for the optimal life activity.
  Physiological and bactericidal action of solar irradiation.
    Solar irradiation is one of the types of electromagnetic irradiation (EMI). By the low of Stephan-
Boltsman, specific capacity of irradiation (E) of every physical body is proportional to the 4-th
degree of its absolute temperature (T), i.e. E=K*T^4, where K - is a constant, equal to 5.77*10^-12
J/s. By the Vin's low of displacement, if the temperature of irradiating body increases, the length of
wave of its irradiation decreases. So, the spectrum of irradiation comes to the side of shorter
waves. By Plank's low, if the wave of EMI is shorter, the energy of ist quantum is larger.
    The biological action of every EMI depends on the quantum's power, the depth of penetration to
the organism's tissues, the intensity, regime and square of irradiation, the conditions of irradiation
and the initial condition of the organism.
    The action of EMI upon the organism has some stages. The first stage is represented as the
primary physical power interaction between the quanta of EMI and molecules of irradiated tissues.
As a result we can observe a heat effect, the excitation and ionization of atoms and molecules. The
second stage is a link of biochemical reactions and accompanying physiological processes (the
dilation of capillaries and so on). Then, the third stage is going on. It is a generalized reaction of the
whole organism with the previous role of neuro-endocrine mechanisms. Such mechanism of EMI
explains the occurance of the expressed local inflammatory process (erythema) and organism's
general reaction, provoked by ultra-violet radiation, which penetrates through the skin only for
some millimetres. The scheme of this process is shown in the next way: the action of EMI - the
primary power interaction - the link of biochemical reactions - physiological processes in the
irradiated tissue - physiological reaction of the whole organism.
    Solar irradiation, reaching the surface of the earth, consists of 59% infra-red irradiation, 40%
visible one and 1% ultra-violet rays. Ultra-violet irradiation is divided into 3 parts: A (the length of
the wave is 400-315 nm), B (315-290 nm), C (290-180 nm). The irradiation from part C doesn't
reach the surface of the earth, as it is absorbed by ozone, placed at a height of 20-30 km.
    Infra-red irradiation penetrates deeply through the skin and provokes heat effect (at the expense
of increased oscillating and rotating movements of molecules), the next increase of tissue
temperature, hyperaemia and the increased metabolism in the skin. It strengthens biological action
of ultra-violet irradiation. This feature is used in medicine.
    Visible solar irradiation makes the same biological action as infra-red one. Besides, it has
photochemical effect. This effect is weaker than ultra-violet one, as the power of its quanta is
enough for the molecules of some matters only. These matters are optic pigments. Under the
influence of visible irradiation the biochemical reactions, generating electical impulses, proceed in
retina. They form light sensation. The level of lighting by visible solar irradiation exceeds that one
by the artificial lighting (from 15000 to 80000 luxes and more).
    The light is an important physiological irritant, which activates the processes of excitation in
brain cortex. That's why, by the good lighting the activity of the visual and other analyzers is
improved. The matters, formed in retina during photochemical action, stimulate the function of
hypophysis and the cells of central nervous system. That's why, the light has a positive influence
upon the emotional sphere, improves organism's condition and metabolism. They mean, that visible
irradiation stimulates the organism not only by visual analyzer, but also by the skin, as we can find
some protoporfirine in blood, which is a photosensibilisator. By pellagra, porfirin's quantity in
blood is increased, that's why photodermatitis and the next pigmentation are developed in the parts
of the skin, irradiated intensively (skin, face). Sulphanile amides and some other medicines are also
photosesibilisators. During the cure by these medicines we must avoid intensive solar irradiation.
    Ultra-violet irradiation, in particular of part B, is characterized by the strong photochemical
action. It provokes the decay of albuminous molecules (whites' photolysis), as a result
physiologically active compaunds are formed (choline, acetyl choline and so on). They activate
sypathetico-adrenal system, metabolitic and atrophic processes. UV-rays stimulate tissue growth
and regeneration (including postoperational measures), blood produacion, immunogenesis,
organism's resistance against infectious, toxic and carcinogenic agents. They improve physical and
mental working ability.
    So, certain doses of ultra-violet irradiation are strong adaptagenic factor, which increases health
level. Stimulated diseases (hypertension, atherosclerosis, cancer, nephritis) are developed in the
irradiated animals more slowly. Besides, ultra-violet rays of part B have an anti-rachitic action, as
vitamin D3 is formed from 7,8-dehydrocholesterol under their action.
    The thickening and the hardening of epidermis and the forming of melanin (sunburn) are very
important protective reactions, which condition the adaptation of organism to the solar irradiation.
The thickened horny layer of epidermis protects from the most active ultra-violet irradiation.
Melanin is formed in the cells of the deepest layer of epidermis, it protects the cells of derma,
vessels and nerves from visible and infra-red rays, which can provoke their over-heating. Melanin
is accumulated in the lowest layers of the skin in the people with the white skin. The people with
the dark skin have more melanin and it is placed in the more surfacisl layers too. During the
contemporary investigations they found out, that melanin wasn't only a passive screen. Owing to its
chemical structure it extinguishes the surplus of free radicals, formed during solar irradiation in the
skin. This protective function isn't less important than the absorption of heat rays for the people,
who live in tropics. Skin cancer is occurred more seldom in people with dark skin than in people
with white skin in tropics.
    Ultra-violet rays (part B) have bactericidal feature, connected with its photochemical action,
which damages nucleic compounds of the bacterial cell. Vegetative forms of bacteria, viruses,
worms' eggs die under the direct sun rays in 10-15 min., spores - in 40-60 min. It is of great
importance for the sanation of the environment in the conditions of hot climate. Short-wave ultra-
violet irradiation (part C) has the most expressed bactericidal action. It is generated by mercury-
quartz lamps and special bactericidal (luminescent) lamps. They are used for the desinfection of
water, air, rooms, surgical instruments and so on.
    Last times it was found out, that very toxic compounds could be formed during the irradiation of
matters, polluting air and ground. So, the complex of compounds, called photooxidators, is formed
as a result of solar irradiation's action upon the components of exhaust gases in the atmosphere of
towns. They provoke strong irritation of mucous membranes of the eyes and upper respiratory
ways (epiphora, unbearable cough), the death of plants, accumulating in the streets of towns in
sunny weather. The poisonous photochemical mists are observed in towns with the expressed solar
irradiation (Los Angeles, Mexico, Tokyo). Hard poisonings of country-men, who worked in the
fields, had been treated by polychlorpinen, in sunny weather were observed in Iran and some other
countries. Very poisonous compounds, formed from polychlorpinen, were found out in the near-
land layer of atmosphere. The photochemical activity of solar irradiation is 2-9 times more in
tropical countries than in European ones. That's why we must always take this fact into
consideration.
    The biological method is widely used to measure the intensity of ultra-violet irradiation. The
unit of measurement is biodose. It is the smallest quantity of ultra-violet irradiation, provoking
hardly visible hyperaemia of untanned skin in 6-20 hours after the irradiation. The minimal daily
prophylactical dose, preventing rachitis in men with the white skin, is 1/8 of biodose. The optimal
dose with the adaptagenic meaning is 1/4 - 1/2 of biodose. The minimal and optimal dose in
aboriginals of hot countries is 2.5 - 5 times more and it depends on the colour of the skin. Ultra-
violetmeter is a special device, used in medicine. Ultra-violet irradiation is absorbed by
photoelement and the generated electrical current is registered by galvanometer. The scale of galve-
nometer is graduated by mcW/sm2. 1 biodose is equal to 600-800 mcW/sm2. Consequently,
minimal physiological request of white man is 100 mcW/sm2, optimal - 200-400 mcW/sm2. These
indices make 250-500 and 500-2000 mcW/sm2 correspondingly for black man. The intensity of
UV-irradiation makes 15-20 mcW/sm2 per min. at a noon in a bright sunny day in tropics. So,
white man will get his prophylactical dose in 5-10 min., and the black man - in 15-20 min.
    The biochemical activity of ultra-violet irradiation in the Western Europe is 2.5-3 times less than
in tropics even in bright sunny days.
    The total flow of solar irradiation consists of the direct radiation, coming directly from the sun,
and the dispersed one from the whole sky. If the sky is clear, the intensity of the dispersed radiation
isn't considerable, but it contains a large per cent of UV-rays. So, if the total intensity of UV-
irradiation is 20 mcW per min. in a bright sunny day, than the direct irradiation makes 12 mcW per
min. and the dispersed one - 8 mcW per min. (40%). This fact is used in medicine. People, whom
the long stay in the sun is contra-indicated, can get their prophylactic dose of ultra-violet irradiation
by the dispersed radiation in the shade. When cloudy sky, the part of the dispersed radiation makes
0.4-0.5 cal/sm2 per min., but it is poor of UV-rays (in particular part B).
    Due to the air pollution by the dust and smoke in the settlements we loose 20-40% UV-
radiation. Owing to the admixture of iron and titanium window glass keeps about 80-90% valuable
UV-radiation of part B. The glass free of this admixture makes way for the most part of UV-rays
and it can be used in hospitals and children's institutions.
        Hypo and hyperirradiation and its influence upon human organism. The deficient irradiation
of the organism by necessary UV-radiation ("sun starvation") is observed in the north latitudes and
in winter - in the middle latitudes. It is connected with the increased number of cloudy days, short
stay in the open air, warm clothing. It decreases organism's adaptation, leads to anaemia, worsens
tissue regeneration, resistance for the toxic, cancerogenic, mutagenic, infectious agents. The
deficient synthesys of vitamin D3 and accompanying breach of calcium and phosphorous
exchanche provokes rachitis in children and osteoporosis, bad regeneration of bones after the
fracture, the growth of caries's rate in adults. In the north latitudes the prophylactic irradiation by
UV-rays is widely used to prevent "sun starvation" (pregnant, miners). These measures are carried
with a help of erythemal-luminescent lamps, their spectrum is 20% visual irradiation, 45% UV-
irradiation of part A and 35% part B.
    But, endemic rachitis between young children was found out even in the country place of
Greece and Mohammedan countries (of the Mediterranean). It is connected with the traditions.
Pregnant women, nursing mothers and young children don't leave the rooms. Woman's body is
clothed, the skin is irradiated weakly and their milk almost hasn't cholecalciferol. The resistance of
the diseased children for the action of harmful factors is decreased. When the children become
older, they stay in the open air more often and become cured from rachitis. The food, containing
enough calcium is necessary for the quick recovery.
    Naturally, the pathology, connected with the hyperirradiation, is more actual for the tropics. The
stay in the open sun with the uncovered head leads to heat stroke. This affection is observed by the
local irradiation of the head and neck. Hyperthermia promotes it. The cause of the local over-
heating is infra-red and partially visible irradiation, heating cranial bones. The temterature between
cranial bones and brain membranes increases until 41 C and provokes the inflammation of brain
membranes. The clinic: headache, the breach of cardio-vascular activity, the lost of consciousness,
convulsions and in hard cases the death. Heat stroke is the most dangerous for the children. The
prophylaxis: the covering of the head and the prevention of total hyperthermia. Besides, solar
irradiation can increase hyperthermal action of high temperature of air and can promote the
appearance of heat stroke. The stay in the open sun is equivalent to the increase of air temperature
for 5-6 C.
    The prolonged stay of unclothed man in the open sun can provoke skin inflammatory reaction -
photoerythema. If the most part of the skin is irradiated, photoerythema is accompanied by the
increase of body's temperature and total indisposition. The cause of photoerythema is a surplus
irradiation by UV-rays. Infra-red and visible irradiation increase ultra-violet's action. The latent
period proceeds some hours. Then, in the place of irradiation we can observe the dilation of vessels,
the swelling of epidermal cells, the appearance of infiltration, the increased pigmentation. The skin
becomes less sensitive to UV-rays.
    The experiments showed, that chronic large doses of UV-radiation provoked the decrease of
organism's resistance for the harmful factors in laboratory animals (the doses exceed 1/2-1
biodose). It is confirmed by the experiments with people. We can observe the worsening of self-
condition, the decrease of resistance for the harmful agents, the progression of cardio-vascular
diseases and chronic inflammations (tuberculosis), the inclination to the allergic reactions.
    It is known, that the surplus solar irradiation provokes the growth of rate of face and lips skins
cancer. So, the morbidity of cancer increases from the north to the south in USA. It doubles every
4-6 degrees of latitude. By O.Chaklin (1986), skin cancer makes 20-22% from other forms of
cancer in the hot regions of UIC and only 4-7% in the north. The newly arrived are diseased by the
cancer of the facial skin 10-12 times more than inhabitants, who defend their face better. The
aboriginals of the Southern Africa are affected by skin cancer 27 times less than white people.
    It is not difficult to prevent hyperirradiation . It is necessary to carry out medical
recommendations relatively sun-bath and work in the open atmosphere. Young children, old men,
people, diseased by cardio-vascular, chronic inflammatory, allergic diseases should get their
prophylactical dose in the shade, to avoid hyperirradiation and the progression of chronic
pathology.
    Most of people gradually adapt to every climate. The adaptational physiological reactions are
based on reflexes, which are mobilized under the action of heat or cold.          The development of
human pathological conditions under the influence of hot tropical climate can be caused by some
interconnected factors:
  1) the breach of thermoregulation;
  2) the breach of regulation of water-electrolyte balance;
  3) the breach of cardio-vascular regulation.
    We should remember, that the breach of thermoregulation and water-electrolyte balance can
accompany any fever in tropical conditions. That's why, during the treatment of such patients we
must act upon the mechanisms of thermoregulation and the reagulation of water-electrolyte
balance.
           The regulation of body's temperature and water-electrolyte balance in human.
    Human body's temperature is determined by the correlation between the heat-production and
heat emission. The centre of thermoregulation is placed in hypothalamus. Body's temperature is
supported nearly 36-37 C owing to the neuro-humoral regulation of heat-production and heat-
emission. The breach of heat adaptation can be caused by some factors:
  1) the intensification of heat factor's action;
  2) organism's unsuitability, in consequence of adaptation to another climate;
  3) the breach of acclimatization by the disease;
  4) physical over-exertion, prolonged drive in a closed car without a conditioner, unrational
clothes, house and so on.
    Under the influence of heat, mainly physical and partially chemical phases of thermoregulation
are activated. Heat emission increases and heat-production decreases. Both processes act in the
same time. But, in hot conditions the chemical thermoregulation isn't as powerlul
as the physical one.
    In dry hot climate the evaporation proceeds easily. By 29 C heat emission increases from 12% to
70%. But, if the humidity grows on, the air cannot absorb water and heat. The thermoregulation
becomes broken and the over-heating is developed. In such conditions the air movement is very
important for the comfort.
    The acclimatization for the hot climate is a process of adaptation to the increased heat loads. It
is shown as the lowering of muscular tone, the intensification of thermoregulation, the ability to
make much sweat in proportion to heat load and to lower salt concentration in sweat, by the
inadequate liquid entrance for the organism.
    It is found out, that the acclimatization has some phases:
      Stage of “alarm” (the first hours in new environment)
      Replacing of the old dynamic stereotype
      Incomplete acclimatization
      Complete acclimatization
 Physiological changes can turn into pathological ones by certain conditions. Human psychical
conditions are of great importance for the acclimatization.
    Most of people, being in tropical countries, are able to acclimatizate completely in 3 weeks.
Some people with the good thermoregulatory abilities can acclimatizate in 5-7 days. But, there are
some people very sensitive for the heat stress, who cannot acclimatizate at all.
    There are some clinical and experimental dates, which testify to the advisability of human's
preliminary training to the action of high temperature to get quick acclimatization. It is realized
by the daily staying in a heat chamber, where we can model different types of hot climate.
Muscular work fascilitates the adaptation to the hot.
    The clothes, the forming of artificial microclimate with a help of different devices are of great
importance for the organism's protection from surplus heat and solar irradiation.
        Heat's influence upon water-salt exchange.
    Under the influence of heat, water-salt exchange is affected in the first place. It is regulated by
the adrenal hormone - aldosteron. This hormone promotes the reabsorption of 99% sodium,
filtrated by renal canals. In the same time it is a regulator of liquid's volume in the organism,
depended on the concentration of sodium in the extracellular liquid. As it has been already known,
the ions of sodium were placed in the extracellular liquid and ions of potassium - inside the cell.
Normally, the correlation of extra and intracellular liquid is a constant value for the individual.
Electrolyte balance (in particular the correlation of sodium and potassium) is supported at a
constant level too, promoting normal functioning of nervous and muscular systems.
    We loose about 20-25 gr of sodium chloride by sweat during a middle muscular work and about
30-35 gr during the intensive one. However, owing to the considerable reserves of chlorides (140-
170gr) and the entrance of about 30 gr of sodium chloride by food, we avoid the breaches of water-
salt balance. The expresses breach of this balance is observed only by use of deminiralized water
(desalinated water and the water of glaciers) and by salt deficit in food.
    The breach of water-salt exchange under the influence of surplus heat is characterized by the
next syndromes:
  1) hyposodiumaemia (the syndrom of salt insufficiency) and
  2) simple dehydration without salt lost.
    In hot climate we usually meet dehydration, but sometimes we can observe both syndromes.
The diseases, provoked by the action of surplus heat.
    There is no one complete classification of these diseases. Most of authors mark out the next
basic forms:
  1) Heat fever - hyperpyrexy (including heat stroke);
  2) Heat exhaustion with the variants:
a) mainly salt insufficiency
b) mainly water insufficiency.
Heat fever. Hyperpyrexy - is an acute overheating of the organism, caused by the breach of
thermoregulation in hot climate, in hot period of year, during stay in over-heated rooms (hot shops).
Usually it is observed in untrained newly arrived in tropics or hot countries. Under the influence of
heat, their thermoregulatory system becomes exhaused. Hyperthermal diseases (malaria, tropical
jungle), alcohol intoxication, vegetative dystony and oths. have an influence upon the occurance of
heat hyperpyrexy.
The clinic is variable. The symptoms of heat stroke occur during the maximal insolation and
sometimes after the patient has come from the zone of insolation to the shade. If we bring the
patient out of hyperthermal zone in prodromal period of the disease, help him quickly, the reaction
is limited by the faint, the feeling of closeness, weakness, a little increase of temperature, the
dilation of pupil, the breach of breathing. In hard cases, the symptoms grow quickly. After the
repeated faints with the sharp adynamy, a strong headache, the stunning, weakness in legs,
tachycardia, sleepiness, sickness, frequent, surfacial breathing, the scqueezing in the chest are
developed. The skin is dry. The next symptoms are oliguria, photophobia, the hyperaemia of the
face and conjunctives, nerrow pupils. Salt insufficiency is occured not always. Then, we can
observe a hard neurological condition: the increasing headache, the excitement. Muscular
fibrillations, epileptoid convulsions are often occur. The breathing is surfacial, frequent, irregular.
Body's temperature grows on till 41-43 C. The patient looses consciousness, his pupils are dilated
and don't react upon the light, the puls is small, filiform, the peripheral blood supply is decreased.
The skin is dry, hot or covered with sticky sweat. The face is pail, cyanotic. The defecation is
irregular. Abdominal reflexes are lowered or absent. Usually we can reveal albuminuria. The shock
is developed.      The treatment. If the cure is right the recovery proceeds quickly (in some days)
and completely. We must put the patient into the shade and undress him. The measures to lower
body's temperature are used. However, we should avoid its sharp fall (lower than 37 C). An ice-
bag, cold water or wet towel are used to cool head, neck and spine. To restore cardiac activity we
make injections of caffeine, camphor, strophanthine (0.5 ml of 0.05% solution intramuscularly),
give oxygen together with carbonic acid's admixture, inject glucose intravenously, give small doses
of physiological solution (200-400 ml) as a hypodermic injection. By the breach of breathing we
use lobelin.
We must thoroughly look for the water-electrolyte balance and correct it if necessary. By malaria
we make intramuscular injections of chlorochine. The prognosis depends on the stages and forms
of the disease and the timely treatment. The mortality is about 5-15% and in some regions - 20-
30%.
The prophylaxix. It is necessary to avoid the prolonged stay in the open sun with the uncovered
head. The next measures are: rational work conditions, clothes, right water regimen, the training of
acclimatization.
   Heat exhaustion.
    1) with mainly salt insufficiency.
 The most considerable predisposing factors are abundant perspiration with the unsupplied water
and salt loss, gastro-intestinal disorders with vomiting and diarrhea. This type of heat exhaustion is
usually met during hard physical work in hot conditions. The breach of water-salt balance
(hyposodiumaemia) and vascular insufficiency are in the first place.
The clinic. The patient complains of headache, the absence of appetite, sickness, vomiting.
Gradually, painful muscular spasms mainly in the gastroknemial muscle and the muscles of the foot
are developed. It is typical for the patients with the repeated vomiting. The next symptoms are
oliguria, vertigo, ataxy, hallucinations. In hard cases the excitement, turning to the sharp inhibition
of mental activity and even coma, is developed. We can observe the signs of organism's
dehydration, orthostatic unsteadiness, vascular insufficiency with the decrease of circulating blood's
volume, the increase of its viscidity, heamatocrite, the number of erythrocytes. In this case an
anuria and necrosis of renal canals can be adjoined. Chlorides' concentration in urine is lowered.
Hyposodiumaemia and hypochlorideaemia are found out in blood. Fantus's test with potassium
chromate is carried on.
The treatment. The main task is to restore water-electrolyte balance and the volume of circulating
blood (by the precautions). In-patient treatment. The cure begins from the entrance of water and
salt per os (5-6 l of water and 30-40 gr of salt during the first day).
By the significant dehydration and collapsus we use the parenteral introducing of liquid (plasm,
physiological solution). During the first hour we inject about 1l of physiological solution and then
about 0.5l for every 4 hours. We should not give more than 3-5 l of liquid in the first day.
    2) heat exhaustion with mainly water insufficiency.
   Easy cases are met in the everyday life in tropics (when water loss isn't supplied). The expressed
forms occur seldom (for example, when man stays in a desert for a long time). In easy cases the
patient complains of headahce, vertigo, weakness, oliguria, a little increase of body's temperature.
In hard cases, the complaints are: the thirst, the concentration of blood, vascular collapsus, difficult
swallowing. The tongue and the mucose membranes of the oral cavity are dry. Body weight is
lowered. The next symptoms are psychical disorders, the breach of co-ordination, coma, quickly
leading to the death. Sometimes, the fit of hyperpyrexy precedes the death. We must make a
differentiation with a salt insufficiency.
The treatment: the patient must be placed in a ward with a cooled air and must be given an
abundant cooled drinking (about 8 l daily). The salt must be given in usual quantity. In hard cases,
we must inject physiological solution, 5% solution of glucose. Hyperpyrexy is treated as usual.
The prophylaxix of breaches in water-salt exchahge.
   The regulation of water regimen during the whole hot season. Daily quantity of water is
determined by the conditions of environment, the intensity of muscular work, the features of
metabolism, the quantity and quality of food. The surplus and irregular drinking leads to the
uneffective perspiration.
Food and drinking regimen. It is nice to use: 0.5% solution of sodium chloride, green tea, iced
acidulated tea, mineral water, fizzy water, dried, curds. It is nice to add some condensed milk to
drinking water. Cold bread kvass (Russian soft beverage), tomato juice with the table salt, the broth
from dried fruit, fruit, fruit juice, water-melon, melon, grape-fruit, lemon, orange juice, tamarind
juice, soft mineral drinks slake the thirst. The douche by fresh water, bathing promote the
prophylaxix of over-heating. It is necessary not to use alcohol and it is very important to keep the
rules of personal hygiene and day regime.
                                  Climate change and health
Climate influences many of the key determinants of health: temperature extremes and violent
weather events; the geographical range of disease organisms and vectors; the quantity of air, food,
and water; and the stability of the ecosystems on which we depend.
Because climate affects us in so many ways and because the details of how the global climate may
change are so uncertain, predicting the health effects of climate change is an inexact science at best.
But given what is already known about the connection between climate and health and the
magnitude of the global warming that scientists project, future health effects could be substantial.
These effects are likely to vary widely from region to region, because climate itself is predicted to
change differently in various regions. For instance, temperatures are expected to rise more in some
areas than others; some places likely will get drier, while others will get more rain than they do
today.
Likely health impacts of climate change include direct effects from temperature and weather
extremes and from sea-level rise. A number of indirect impacts are also likely to arise from changes
in precipitation and temperature patterns, which may disturb natural ecosystems, change the
ecology of infectious diseases, harm agriculture and freshwater supplies, exacerbate air pollution
levels, and cause large-scale reorganization of plant and animal communities These indirect effects
may, in the long run, have greater cumulative impacts on human health than the direct effects.
Climate Change Could Profoundly Affect
Health
Direct and Indirect Health Impacts of Climate
Change
Source: Adapted from: World Health
Organization (WHO), Climate Change and
Human Health, A.J. McMichael, et al., eds.
(WHO, Geneva, 1996), Figures 1.1, p. 12.


Direct Impacts
One of the most easily imagined impacts of global warming is an increase in the number and
severity of heat waves. Heat stress is a well-known danger during prolonged bouts of hot weather,
especially in cities, which tend to trap heat. In both New York and Shanghai, for instance, records
show that daily mortality rates increase sharply once temperatures exceed a certain threshold.
During intense heat waves, the death toll attributed to heat stress can be surprisingly high, as
occurred in Chicago in July 1995, when heat stress killed 726 people during a 4-day heat wave.
Midlatitude cities including Washington, D.C., Athens, and Shanghai seem to be at greatest risk for
deadly heat waves. In these cities, residents (especially the elderly, the very young, and the poor)
are not acclimatized to extremely hot weather and are thus more vulnerable to heat stress. Among
these vulnerable groups, the existence of previous health problems, greater heat exposure due to
substandard housing, and lack of access to air conditioning are all factors leading to higher heat-
related mortality. By the middle of the next century, climate change could increase the frequency of
very hot days several fold in a city similar to Washington, D.C. The normally hotter average
temperatures in tropical and subtropical cities seem to help residents accommodate heat waves
better, so they suffer fewer heat-stress problems, although heat-related deaths during a 1995 heat
wave in New Delhi indicate that even residents in the tropics can be susceptible to extreme
temperatures.
Conversely, a potential health benefit of warmer global temperatures could be fewer cold-related
deaths as winters become milder. A recent British study estimated that by 2050, an increase in the
average wintertime temperature by 2.0° C to 2.5° C, as predicted by some climate models, might
result in as many as 9,000 fewer cold-related deaths per year in England and Wales. Yet, this
decrease in winter mortality would probably only partially offset additional heat-related deaths;
studies indicate that higher mortality is generally associated with heat waves than cold spells.
In addition to more frequent heat waves, global climate change is expected to result in greater
weather variability overall. In particular, climatologists believe that relatively small changes in the
average global climate in the future could produce large changes in the frequency of extreme
weather events, such as hurricanes (cyclones), violent thunderstorms, and windstorms. Through
flood and wind damage, these natural disasters already exact a heavy burden in the destruction of
lives and property.
Rising sea levels, another expected consequence of global warming, could adversely affect the
health and well-being of coastal inhabitants. Sixteen of the world's largest cities with populations of
more than 10 million are located in coast al zones, and coastal populations are increasing rapidly
worldwide. The IPCC projects that sea level will rise between 0.3 and 1.0 meter by 2100, with a
best-guess estimate of 0.5 meter.




The most immediate threat from such a rise would be to those who live directly on the coast, in
low-lying areas such as river deltas, or on small island nations such as the Maldives, the Marshall
Islands, Kiribati, and Tonga, where land is virtually all within a few meters of sea level already.
Rising seas would inundate many of these islands, increase storm damage to the remaining land,
and contaminate the freshwater supplies found in island aquifers.
Delta regions such as the Ganges-Bramaputra delta in Bangladesh, the Nile delta in Egypt, or the
Niger delta in Nigeria could also suffer a similar fate. The situation in Bangladesh's densely settled
Ganges-Bramaputra delta is probably the most serious. A recent study projects that a 1-meter sea
rise could inundate 17 percent of Bangladesh's total land area and displace some 11 million people
(at current population densities). In the Nile delta, a 1-meter rise would displace around 6 million
people unless costly protection efforts were mounted; and in the Niger delta, a similar rise would
inundate 15,000 square kilometers of land and force about one half million people to relocate.
According to the United Nations' Intergovernmental Panel on Climate Change (IPCC),
anthropogenic greenhouse gas emissions are significantly altering the earth's climate. By the year
2100, average global temperatures are projected to rise by 2.0-2.5°C (range 1.5-4.0°C). This
projected rise in temperature represents a five-fold faster rate of warming than that observed over
the past century. These IPCC figures even assume a reduction in global economic growth rate,
slowed population growth over the next half century and improved conservation measures. These
projections are consistent with climate sensitivity to atmospheric CO2 concentrations observed from
ice core data extending over 158,000 years. Sea level also is expected to rise by about 34-52 cm. by
the year 2100 as a result of ocean thermoexpansion and by melting of glaciers.
Summary. While uncertainties always will accompany predictive climate modeling, there is
increasing agreement between climate projections arising from varying methodologies in multiple
climate centers internationally. The medical community is beginning to examine the consequences
that these projections may portend for public health, and the World Health Organization considers
global warming as a serious public health challenge for the future.
Under the conditions of global warming, direct hazards to human health (e.g., urban heat-island
effect and harmful air pollution) may become significant public health problems given current
trends in urbanization. Warmer temperatures combined with increased ambient UV radiation could
worsen photochemical smog, especially over urban areas. Elevated night-time temperature readings
are the most significant meteorological variable contributing to heat-related mortality; the
greenhouse effect is predicted to especially affect these minimum temperatures, and studies
estimate a 3 to 4-fold increase in heat-mortality in large temperate US cities under a doubled
atmospheric CO2 scenario (which could occur by the year 2040 if current fossil fuel emission trends
continue).
Infectious agents which cycle through cold-blooded insect vectors to complete their development
are quite susceptible to subtle climate variations. In temperate regions, climate change would affect
vector-borne diseases by altering the vector's range, reproductive and biting rates, as well as
pathogen development rate within the vector host.
Malaria and dengue fever serve as prime examples of climate sensitive diseases. The geographic
range of malaria is generally limited to the tropics and subtropics because the Plasmodium parasite
requires an average temperature above 16° C to develop. Malaria has been observed in non-
endemic high elevations in Africa during unseasonably warm conditions.
Freezing temperatures kill overwintering eggs of Aedes aegypti, the mosquito carrier of dengue and
yellow fever. Warming trends, therefore, can shift vector and disease distribution to higher latitudes
or altitudes, as was observed in Mexico when dengue reached an altitude of 1,700 meters during an
unseasonably warm summer in 1988. In an earlier study in Mexico, the most important predictor of
dengue prevalence in communities was found to be the median temperature during the rainy
season.
Temperature also drives epidemic dynamics of dengue transmission. Warmer water temperatures in
breeding vessels reduces the size of emerging adults that subsequently must feed more frequently to
develop an egg batch. Viral development time inside the mosquito also shortens with higher
temperatures, increasing the proportion of mosquitoes that become infectious at a given time. Thus,
mosquitoes bite more frequently and are potentially more infectious at warmer temperatures.
Climate-related increases in sea surface temperature can lead to higher incidence of water-borne
cholera and shellfish poisoning. Marine phytoplankton blooms include red tides that cause diarrheal
and paralytic diseases. Vibrio cholera has been found to be associated with marine zooplankton,
and blooms from warmer sea surface temperatures could expand this important reservoir from
which cholera epidemics may arise.
Human migration and damage to health infrastructures from the projected increase in climate
variability and severity of storms could threaten human shelters and public health infrastructures
and indirectly contribute to disease transmission. Human susceptibility to disease might be further
compounded by malnutrition due to climate impacts on agriculture.
As experts in the field of Occupational and Environmental Medicine, we need to better understand
the linkages between climatological and ecological change as determinants of public health. Our
field of medicine must begin to grapple with some of these "ecologically-based" environmental
health hazards. Addressing this newly recognized threat will require interdisciplinary cooperation
among health professionals, climatologists, biologists and social scientists, and will necessitate
research beyond conventional dose-response linear relationships to address complex systems-based
ecological processes.
The long-term insideous nature of the "exposure" of climate change also requires shifting attention
to the health of future generations. Sustainable public health means promoting health for people
today, without compromising on resources needed by future generations to achieve the same level
of health. No less priority should be given to current health crises, however, the scope of
Occupational and Environmental Medicine needs a broader focus to begin to anticipate
intergenerational health challenges, already requiring preventive measures. In planning adaptive
measures (e.g., air conditioning and vector control strategies) long-term impacts must therefore be
considered. For example, increased energy demand for air conditioning will exacerbate greenhouse
gas emissions and widespread pesticide applications can promote insect resistance, as well as
impact human health directly through toxic exposures.
New understanding of linkages between public health and "global life-support systems" is
emerging in the literature. Prime examples are those of stratospheric ozone depletion, climate
change, and threatened fisheries which have enormous implications for public health, but may not
be immediately perceptible. Through new collaborative efforts we can begin to confront these
tough challenges and advance that much further in the practice of true preventive medicine.
Glossary:
Climatology The scientific study of climate. Part of meteorology which studies processes of
climate formation, distribution of climates over the globe, analysis of the causes of differences of
climate (physical climatology), and the application of climatic data to the solution of specific
design or operational problems (applied climatology). Climatology may be further subdivided
according to purpose or point of view: agricultural climatology, air-mass climatology, aviation
climatology, bioclimatology, dynamic climatology, medical climatology, macroclimatology,
mesoclimatology, microclimatology, paleoclimatology, synoptic climatology and others.
Marine climate Climate of regions adjacent to the sea characterized by small diurnal or
annual, or both, amplitudes of temperature, and by high relative humidities.
Medical climatology Study of the influence of climate on the health of human beings
Class I area: geographic areas designated by the Clean Air Act where only a small amount or
increment of air quality deterioration is permissible.
Clear ice: a thin coating of ice on terrestrial objects, caused by rain that freezes on impact. The ice
is relatively transparent, as opposed to rime ice, because of large drop size, rapid accretion of liquid
water, or slow dissipation of latent heat of fusion.
Climate: the composite or generally prevailing weather conditions of a region, throughout the year,
averaged over a series of years.
Climatology: the science that deals with the phenomena of climates or climatic conditions.
Cyclone: a large-scale circulation of winds around a central region of low atmospheric pressure,
counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere.
El Niño: literally, the Christ child, a name given to an extensive ocean warming in the equatorial
eastern Pacific along the coast of Peru and Ecuador that often begins around Christmas (hence, the
name). The warming brings nutrient-poor tropical water southward along the west coast of South
America in major events that recur at intervals of 3-7 years. El Niño is associated with atmospheric
circulations that produce wide ranging effects on global weather and climate.
Equinox: the time when the sun crosses the earth's equator, making night and day of approximately
equal length all over the earth and occurring about March 21 (the spring or vernal equinox) and
September 22 (autumnal equinox).
Gap winds: strong winds channeled through gaps in the Pacific coastal ranges, blowing out into the
Pacific Ocean or into the waterways of the Inside Passage. The winds blow through low passes
where major river valleys issue onto the seaways when strong east-west pressure gradients exist
between the coast and the inland areas, with low pressure over the ocean.
Greenhouse effect: atmospheric heating caused by solar radiation being readily transmitted inward
through the earth's atmosphere but longwave radiation less readily transmitted outward, due to
absorption by certain gases in the atmosphere
Low-level jet: a regular, strong, nighttime, northward flow of maritime tropical air over the sloping
Great Plains of the central United States, in which the wind increases to a peak in the lowest
kilometer and then decreases above
Troposphere: The portion of the earth's atmosphere from the surface to the tropopause; that is, the
lowest 10-20 km of the atmosphere. The troposphere is characterized by decreasing temperature
with height, and is the layer of the atmosphere containing most clouds and other common weather
phenomena
Wind chill equivalent temperature: the apparent temperature felt on the exposed human body
owing to the combination of temperature and wind speed.

								
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