Meteorological environment lecture ppt
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This document discusses various elements of the meteorological environment including atmospheric pressure, air temperature, and humidity. It describes how these factors are measured and influenced. The effects of high and low atmospheric pressures on health are explained, such as acute mountain sickness and decompression sickness. Various heat stress indices are defined that take into account factors like temperature, humidity and air movement. The potential health impacts of heat stress like heat stroke, heat exhaustion and heat cramps are outlined. Preventive measures for hot working conditions like water replacement, work regulation and protective clothing are recommended.
Meteorological environment lecture ppt
- 2. Meteorological Environment Meteorology is the branch of science concerned with the processes and phenomena of the atmosphere, especially as a means of forecasting the weather. The elements which comprise the meteorological environment are: (1) Atmospheric pressure (2) Air temperature (3) Humidity (4) Rainfall (5) Direction and speed of wind and (6) Movement of clouds and character of weather
- 3. Climate The term "climate" is a geographical concept representing a summation of the whole range of meteorological phenomena.
- 5. Atmospheric pressure The atmospheric pressure at earth's surface close to the sea level averages 760 mm of Hg. -This is called "one atmosphere of pressure". -Man is physiologically adapted to live at 760 mm of Hg pressure or close to it. -The atmospheric pressure falls as altitude increases, and rises as altitude decreases. Thus, at an altitude of 100,000 feet above mean sea level, the atmospheric pressure is less than 10 mm. of Hg. -The pressure increases at the rate of "one atmosphere" for each 33 feet depth below sea level.
- 6. Measurement of atmospheric pressure The instruments used for measuring atmospheric pressure are known as barometers of which there are three well known kinds : 1) Fortin' s Barometer; 2) The Kew Pattern Station Barometer and 3) the Barograph. #The 'Kew Pattern' Station Barometer is widely used by the Indian Meteorological Department for measuring the atmospheric pressure. #Barograph is an instrument for obtaining a continuous record of atmospheric pressure
- 8. Effects of atmospheric pressure on health HIGH ALTITUDES-The air is less dense at higher altitudes, and consequently the partial pressure of oxygen is also less. Man cannot survive at an altitude of 25,000 feet without breathing equipment. When man is exposed to low pressures, the physiological effects are : ( 1) increase in respiration . ( 2)increase in the concentration of haemoglobin . (3) increase in cardiac output.
- 9. CONTD.
- 10. CONTD. Two conditions have been described as a result of sudden exposure to high altitude : (1) Acute Mountain Sickness- This is a relatively common, harmless, and transient condition characterised by headache, insomnia, breathlessness, nausea, vomiting and impaired vision. It has not been conclusively proved whether all these symptoms are due to the effect of hypoxia or due to the various intricate biochemical and hormonal disturbances in the body..
- 11. CONTD. (2) High Altitude Pulmonary Oedema : The symptoms generally appear on about the third day at high altitude and are indistinguishable from those of ordinary mountain sickness. But as pulmonary oedema develops, the patient develops a cough, and may experience irregular or Cheyne Stokes breathing, oligurea, mental confusion and hallucinations, stupor, seizures and coma. -The condition is rare below 12,000 ft. (3,600 m.). The condition does not respond to antibiotics. The patient should be carried to lower altitudes as soon as possible
- 13. SUDDEN EXPOSURE TO LOW ALTITUDES The atmospheric pressure increases by one atmosphere for every 33 feet depth below sea level. The greatest depth so far reached are the equivalent of 10 atmospheres. When man is exposed to high pressure, the gases in the air namely oxygen, carbon dioxide and nitrogen are dissolved in the blood and tissues proportionately to the partial pressure of these gases. 1)Excess concentration of nitrogen excerts a narcotic action leading to loss of mental functions and consciousness; 2)Excess of carbon dioxide increases the narcotic action of nitrogen; 3)Excess of oxygen can lead to convulsions and death.
- 16. CONTD. When the person comes up to the surface, the gases which are dissolved in the blood under pressure are released and cause air embolism, the effects of which are fatal. The effects of increased pressure are best observed in persons working in diving bells and compressed air chambers (Caisson disease).
- 18. AIR TEMPERATURE
- 19. AIR TEMPERATURE The temperature of air varies in different parts of the day and also in the different seasons. The factors which influence the temperature are latitude of the place, altitude, direction of wind and proximity to sea. The temperature of the ground surface is always higher than that of the air.
- 20. MEASUREMENT Thermometers are instruments used for measuring temperature. Mercury thermometers are widely used, as mercury boils at a high temperature, has a regular expansion and its level can be easily seen. Alcohol thermometers are also used. Alcohol has the advantage of not solidifying even at the lowest known temperature. The essential conditions for the use of the thermometers are that:- (1) the air should have free access to the bulbs of the thermometers and (2) the thermometer should be protected against radiant heat. These conditions are fulfilled by mounting the thermometers on a special approved screen called the "Stevenson Screen“.
- 28. Heat stress indices Heat stress is the burden or load· of heat that must be dissipated if the body is to remain in thermal equilibrium. The factors which influence heat stress are metabolic rate,air temperature, humidity, air movement and radiant temperature. The amount of heat gained by the body must be equalled by the amount of heat lost from it.
- 29. CONTD. Heat stress indices include – Equatorial Comfort Index, Heat Stress Index, and Predicted Four Hour Sweat Rate (P4SR). (a) Equatorial comfort index: This denotes the temperature of still and saturated air which is equivalent physiologically to the climate under consideration. (b) Heat stress index : This takes into consideration the metabolic rate and the principal channels of heat exchange between the human body and the environment. The heat stress index represents the percentage of the heat storage capacity of an average man
- 30. CONTD. The rate at which a man sweats is a good index of the heat stress to which he is subjected. A sweat rate of 4.5 litres in 4 hours is the upper limit of tolerance in health for work in hot environment. A sweat rate of 2.5 litres in 4 hours is considered optimal for a working man.
- 31. CONTD. 0--------------------- No thermal stress 10-30 ----------------Moderate to mild heat strain 40-60 --------------Severe heat strain 70-90---------------Very severe heat strain 100------------------- Upper limit of heat tolerance
- 33. Effects of heat stress (1) HEAT STROKE: This is attributed to failure of the heat regulating mechanism. It is characterized by very high body temperature which may rise to 110°F (43.3°C) and profound disturbances including delirium, convulsions and partial or complete loss of consciousness. The skin is dry and hot. Classically, sweating is absent or diminished. (2) HEAT HYPERPYREXIA : This is attributed to impaired functioning of the heat-regulating mechanism but without characteristic features of heat stroke. It is arbitrarily defined as a temperature above 106°F . It may proceed to heat stroke.
- 34. Effects of heat stress (3) HEAT EXHAUSTION : Heat exhaustion is not because of failure of thermo-regulation. It is a milder illness than heat stroke and is caused primarily by the imbalance or inadequate replacement of water and salts lost in perspiration due to thermal stress. Heat exhaustion typically occurs after several days of high temperature. Body temperature may be normal or moderately elevated, but it is uncommon to exceed 102°F (38.9°C). The symptoms, primarily dizziness, weakness and fatigue, are those of circulatory distress.
- 35. Effects of heat stress (4) HEAT CRAMPS: Heat cramps occur in persons who are doing heavy muscular work in high temperature and humidity. There are painful and spasmodic contractions of the skeletal muscles. The cause of heat cramps is loss of sodium and chlorides in the blood.
- 36. Effects of heat stress (5) HEAT SYNCOPE-The condition results from pooling of blood in lower limbs due to dilatation of blood vessels, with the result that the amount of blood returning to the heart is reduced, which in turn is responsible for lowering of blood pressure and lack of blood supply to the brain. -This condition is quite common among soldiers when they are standing for parades in the sun .
- 37. PREVENTIVE MEASURES (1) REPLACEMENT OF WATER- Persons working under conditions of high temperature and humidity should be encouraged to drink cool water. About one litre of water per hour for hard worker man. For a sedentary worker, the requirement is nearly half this quantity. (2) REGULATION OF WORK (3) CLOTHING (4) PROTECTIVE DEVICES (5) WORK ENVIRONMENT