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UNIT 17 HEAT AND COLD WAVES

Structure 17.0 Learning Outcome 17.1 Introduction 17.2 and : Criteria f 7.3 Affected Regions 17.4 Causes and Impacts 17.4.1 Causes of Heat Wave 17.4.2 Causes of Cold Wave 17.4.3 Impacts 17.5 Prevention and Preparedness 17.5.1 Prevention 17.5.2 Preparedness: Advance Warnings 17.6 Rescue and Relief 17.7 Conclusion 17.8 Key Concepts 17.9 References and Further Reading 17.10 Activity

17.0 LEAWING OUTCOME ~fterstudying this Unit, you should be able to: m understand air temperature and other criteria associated with heat and cold waves; o leam about the regions susceptible io such events including the vulnerable areas in ; o discuss the causes and impacts af heat and cold waves; r explain the health hazards and other damages caused due to extreme tempe'ratures during heat and cold waves; and o describe preventive measures to minimise the sufferings.

Natural like , , and are of meteorological origin, that is associated with the situation. They wc&ionally leapcatastrophic situations heaping untoldmisery over the affected areaslregions. There are other weather situations as well which, though not disastrous by themselves, could linger on and create hazardous or even disastrous weather causing severe health problems leading to loss of lives, damages to seasonal crops and other related miseries. Among these are lingering spells of heat and cold waves. In the forty years i.e. from 1936 to 1975, nearly 20,000 people were killed in the by the effects of heat. In the disastrous heat wave of 1980 more than 1,250 people died in one single 204 Utzderstnizcli~zg Natural Disasters

year, and in 1901 the heat wave killed 9,508 people in the United States. In Australia, heat wave\ accounts for more deaths than any other natural , During 1939, severe heat wave took toll of 438 lives in South Australia and 400 of these were from Victoria province alone. In India too, casualties are no less significant. In theyear 1988, the severe heat wave killed nearly 900 persons in the states of Madhya Pradesh and Rajasthan during the months of May and June. In 1998, the casualties were still higher and according to a report, nearly 1,300 persons died in the heat wave over different parts of the country. The casualties from cold waves are no less. In extra-tropical countries, considerable casualties are due to low temperatures during a cold wave. In India and other countries in tropical areas, prolonged exposure to cold temperatures causes a number of deaths every year. Reports indicate that in India more than 600 persons dieddue to cold waves in the of 2001-02; and during the first fortnight of January 1983 the death toll was 452 in the two States of Bihar and Uttar Pradesh. In such extreme temperatureconditions, the worst affected are the economically weaker sections of the society who cannot afford to ensure protection against exposure to the extremes of weather, particularly the temperitures. Other victims are those who are in the susceptible age groups like the very young and the old or the infirm with fragile health conditions, chronic invalids and those with weight and alcoholic problems which for apparent reasons have little adaptability to extreme temperature variations. * 17.2 MEAT WAVE AND COLD WAVE: CRITERIA i) General Temperature conditions, which vary from extreme hot to chilly weather differ from place to place. In fact, people living at a place for long get acclimatized to the normal weathedclimate of that place/region. For instance, in the coldclimate region (extra tropical regions or high level stations), day temperature of more than 30° C may be a hot day for the locals whereas this temperature in the warm region may present the feeling of comfortable weather. In the equatorial and tropical regions, locals are accustomed to wandhot weather. Threshold temperature at which hot weather begins to cause discomfort and health problems for people in these regions is apparently much higher than. in the higher latitudes. Comfortable temperature range for inland and coastal stations of the same climate regimes may also differ substantially due to varying levels and the wind flow. In these cases, it is the va-iationof effective temperature (which takes into account wind speed and humidity along with ambient air temperature) from the normal climatic conditions, instead of the ambient air temperature alone, which influences the comfort level and related health risks. Similarly, people ipold clilnate conditions are acclimatized to rather low temperatures and threshold values for cold yave cohitions in those regibns are much lower than for people living in warm . Thus, health relatedproblerns due to cold waves in the extra-tropical countries are different, compared to those in the . Injuries due to extreme cold temperatuses and related problems are more common in the extratropics. Threshold values of prevailing air temperature and their departure froin normal for heat and cold wav&s,therefore, differ from one place to another and arepri~narilydependent on the following factors: e LocaI climatic conditions e Geographic and Topographic fe'eat~~resof the place Heat and Cold Waves 205

It should also be noted that heat wave is reckoned with reference to abnormal rise in the day temperature (the so called Maximum Temperature) whereas cold wave is reckoned with reference to an abno~~nalfall in the early morning temperature i.e. the Minimum Temperature. ii) Criteria in Extratropical Countries &at Wave In the extra tropical countries, heat wave is considered as the period of abnormally hot and dry . weather or when it is uncomfortably hot due to humidity. To be tenned heat wave, it should last atleast more than a day over the area. Howeve]; conventionally heat wave lastsfor several days to several weeks depending on the prevailing weather conditions. Cold Wave Weather fluctuations in the extra-tropical regions are rather rapid and related with fast movement of weather systems. Many a times, cold air Inass sweeps in rapidly in the rear of a weather disturbance, which causes the chill to be more effective. Criterion f'orcold wave includes not only the minimum temperature to which it may fall but also the rate of temperature fa11 within 24 hours. i iii) Criteria followed in India IndiaMeteorologicalDepartment uses a simple procedure to define heat and cold waves in relation with temperature departures from the nonnal day (Maximum) and night (Minimum) temperatures of the placelarea. Heat waves are termed as moderate or severe if the prevailing maxi~num temperatures are markedly C6-7O C) or 8O C or more above normal, respectively. In the same way, cold waves are tenned mode9 .ate or severe if the prevailing xninirnu~ntemperatures are markedly (6-7°C) below normal or Fall by 8OC or more below normal. This is now being revised to make tel-minologies more in confolmity with international practices by linking the temperature departures with local climatic conditions andco~nfoft.levelsinstead of basing them on temperature departure values alone. Concept of Hot Day and Cold Day has been also added to describe the temperature extremes which are rather border line cases prior to attaining heat and cold wave stage.

- - --- 17.3 AFFECTED REGIONS Sorne regions are more susceptible than others due to the following factors: a Solar heating and radiative cooIing effects are more over the land than over the sea. F~~rthermore,land and sea breeze tend to inhibit these effects over the and islands, Land locked areas are, therefore, more prone to the occurrence of extreme temperatures, e In the tropics, heat waves are rather common in the land-locked areas due to intense solar heating by the direct sun rays. a In the mid-latitudes, preferred regions for heat waves are where southwesterlylnorthwesterly winds bring willin tropical air to higher latitudes in n~~thernlso~rtliemhemisphere, In northern hemisphere, eastern parts of North America and east European countries experience such weather situations more frequently during the surn~nermonths. In the southern hemisphere, different parts of west and south Australiaexperience heat waves, which persist for number of weeks and account for more number of deaths than any other there, Urban areas experience greater effects of heat wave th~u~the rural regions, Asphalt and , used in abundance in urban areas, store heat longer and release it gradually during night, which produce signiticcantly higher day and ~~igl'lttime temperatures in urban weas. Built up large cities act as heat islands.

-. .-- ..- 206 U/tder.~tandingNaturril Disasters

e Cold waves are associated with the incursion of cold air-mass to warm places. It generally takes place in the rear of the passage of low pressure system which brings cold air from higher latitudes to regions of lower latitudes. o In India, heat and cold wave conditions are Inore frequent in the north, central and adjoining eastern parts of the countly. These occasionally extend southwards to Peninsular India. Heat waves occur in the coastal regions of the States of Orissa and AndhraPradesh on the east when the prevailing weather is hot and huinid under calm wind and cloudless sky conditions. CAUSES AND IMPACTS Heat and cold waves are caused by the extreme temperature, during the and winter months. 17.4.1 Causes of Heat Wave Progressive northwardsouthward march of the sun towards the tropic of cancer/capricorn (23O30' NIS latitude) brings summer to the northernlsoutherrt hemisphere, respectively. As the associated solar heating progl-esses with it, land areas in the interior of the continents consistently experience high temperatures during the summer season. Under favourable weather situations, which inhibit formation andlor facilitate inflow of warmer air, day temperatures may rise substantially above normal values and may Iead to heat wave conditions over the area/region. Weather features, found favourable, for heat waves in the ex%6%opical regions are: i) Inflow of wann tropical air to higher latitudes. It is caused by the south-westerly winds in the northern hemisphere, at sealevel and aloft. In the southern hemisphere, advection of warm tropical air to higher latitudes takes place with northwesterly wind flow. ii) Little or no moisture in the upper makes the sky cloud free and allows maximum solar heating. In the tropical regions, hot and dry spells generally prevail over land locked regions ofthe tropics during the summer mon ths. In the absence of any low pressure system, persistent heating due to intense sunshine under cloud free sky may Iead to favourable conditions for day temperatures to rise above normal, resulting in moderate to severe heat wave conditions. Heat wave over India CIimatologically, there is consistently high temperature during the months of April-June with May recording the highest value. Over some areas of central and northwest India, the peak is reached in June before the onset of the southwest . Occasionally, abnormally above normal day temperatures are reported in the months of March and July as well from some pasts of the country. Apart from solar heating, dry continental westerly wind prevails over northern and central parts of the country, which gives clear weather north of the 20"N latitude. Long trajectory of the wind flow over hot land areas provides favourable conditions for prolonged hot spel Is. This is occasionally disturbed by the low pressure systems moving west to east across north India, as a trough or closed cyclonic circulation which may give rise to convective activity, cloudiness andprecipitation and bring temporary break in theprevsliling hot weather. The favourable factors for heat wave are: Hot dry air, with history of long-land travel, prevailingovel-the region. Absence of weather generating low pressure systems moving acrossnorthwest India. Heat and Cold Waves

17.4.2 Causes of Cold Wave Cold wave conditions occur during the winter months when the cold air Inass from higher latitudes sweeps over the region. In the rear of well marked moving low/pressure system in the westerly wind flow of rnidlatitudes, which travel from west to eaqt, winds from nol-thwester~y/southwesterly direction in northernlsouthern hemisphere prevail and bring cold air mass from higher latitudes. Cold wave conditions develop if the temperature falls rapidly much below normal. Occasiondly, foggy weather develops during the day which inhibits day warming and provides favourable conditions for cold wave conditions to linger on. Clear sky conditions during the night, further facilitate lowering of ternperatuse by unobstmcted radiation cooling. The conditions favourable for cold wave are: i) Inflow of cold air mass from higher latitudes over the region in the rear of the passage of well markedlow pressure system in the westerly wind flow of mid-latitudes. r ii) Foggy weather during the day which inhibits day warming of the region. iii) Strong radiation cooling during th3 night under clear sky conditions. Cold wave over India Cold waves over the country are generally experienced during December -February. Rarely these may also occur in the northern parts of the country in the months of November and March as well. The frequency of occurrence of cold waves is inaximum over northwestern parts of India. It falls considerably towards the southern and eastern parts. Occurrence of cold wave is associated with the inflow of very cold air from extreme northwestern parts of the Indian-sub-continent or even beyond. The following weather situations are favourable: i) Passage of a well-marked low pressure system in the upper air westerlies andlor a low pressure system at sea-level and aloft across north India and/or adjoining regions. The system generally causes widespread rainfall activity over the plains andsnowfall over the hills. ii) In the rear of the rainfall/snowfall activity, northwesterly winds may set over the region and cause inflow of cold air mass from higher latitudes andlor mountain regions. iii) Occasionally, in the absence of western distu bances and persistent clear sky conditions, intense nocturnal radiation cooling may also cause night temperatures falling below normal and result in cold wave conditions. 17.4.3 Impacts

. . Thermal .' Human beings have great capacity to adapt themselves to the climate in which they live, but they are still vunerable to marked and rather sudden changes in ineteorologicsll conditions. Devastating impacts of extreme heat or cold temperatures on human health, live-stock as well as industrial and productions are experienced in most parts of the world. Temperate andforcold regions of mid latitudes have, however, greatereffect of heat wave compared to warm tropical regions, Same way, cold wave is more devastating in warm tropical regions than over the cold climate regions. Heat and cold waves cause extreme thermal stress to huinan body, which may lead to devastating impacts on human health and well-being. The probability and severity of health disorders increases progressively if the thermal stress is persistent. The impact of consecutive days of extreme hot or cold, say a week or more, will be quite significant on human health, live stock, agriculture and 208 Utlderstanding Natural Disasters

industrial production as well, compared to the same being spread over the period of amonth with intermittent breaks. i) Hyperthermic and Hypotherrnic Environment The human body maintains its normal temperature by losing the excess heat which is continuously generated within it by the metabolic processes. Nomally, this is done by dissipating the body heat into the cooler atmosphere through the skin surface. We feel comfortable when the heat load and the dissipation rate are equal and a thermal equilibrium is reached to maintain normal body temperature, without resorting to any of the feed back mechanisms such as sweating and shivering. Discomfort arises when the heat load exceeds the dissipation rate in the hyperthemic environment or when dissipation rate exceeds the heat load in hypothelmic environment. In hyperthesmic or hypothesmic environment, sweating or shivering is necessary to maintain thennai equilibrium. However, both feedback ~nechanismscan be effective for only a short period. Persistent thermal stress, therefore, leads to heat or cold related health hazards, , ii) gat Wave and Thermal Stress During heat wave conditions, environment temperature is much higher than the normal body temperature. Human body finds it difficult to get rid off its excess heat. It calls upon the millions of sweat glands, which perforate the outer layer of the skin. These tiny glands can shed great quantities of water as we perspire. The evaporation of perspiration has the effect of absorbing the heat energy in the fonn of latent heat of evapordtion, which cools the body and helps in m.aintaining the normal body temperature. Excessive perspiration can, however, cause and salt deficiency in the body. When the air is humid, evaporation process is retarded and the body has to make strenuous efforts to dissipate the extra body heat and this may result in heat related illnesses,'aq mentioned below:

0 Heat Rashes (PricW y Heat)

0 Heat Cramps e Heat ~yncope(~ajntin~)

0 Heat Exhaustion and

Q . It is an emergency situation and needs immediate medical attention. Apart from human stress, heat wave conditions lead to increased demand of water for public, industry and irrigation. iii) Cold Wave and Thermal Stress Similarly, by prolonged exposure to cold wave conditions, abnormally low body temperature may occur as the body loses heat faster than it can produce by muscle contractions, metabolism and shivering. Early syrnptoms are generally slow and may cause numbness and injuries to exposed parts of the body. Shallow breathing, decreased level of consciousness, clumsy movements, blurred speech and blue - grey skin may follow if exposure persists. If the heat loss continues, it can lead to unconsciousness and death. Cold wave related illnesses ase: e Frostnip, which cause numbness or may temporarily cause blue-white skin colour.

6 Chill blains

0 Frostbite Hypothemia - an emergency condition which needs immediate medical attention. Heat and Cold Waves 209

Apart from impacts on humans, cold wave conditions cause considerable damage to flora, fauna and agricultural activities.

17.5 PREVENTION AND PIREPAREDNESS

17.5.1 Prevention Best way to prevent illnesses due to heat and cold waves is to avoid prolonged exposure to the outdoor environment. The following precautions can, however, help to ininirnise ill effects due to exposure: i) ~eakwave: clothing e Wear light weight, light colouredcotton clothings whichcan absorb sweat from the skin as the evaporation of sweat decreases the body's temperature. e A pper body sweats more than the lower half, so wearing clothing of loose fittings which allows for more air circulation from the waist up is a good way to transfer heat away from the body. e While outdoor in hot sunny weather, cover the head with well ventilated hat or cap. It helps \ \ heat loss from the body and also protects it from direct exposure to sunshine. Avoid Dehydration e Drink plenty of water and fluids. Drink extra fluid if you sweat a lot and increase salt intake if not on salt restricted diet. Carry a bottle of water while going out and sip water frequently. e Avoid alcoholic beverages because alcohol can cause dehydration. ii) Cold waves Like heat waves, preventive measures are the best way to avoid inJuries/illnesses due to exposure during cold waves. Apart from humans, cattle and pets need td be saved from over exposure ta cold wave conditions. Clothing e Dress with clothes, which retain body warmth and help rninimise loss of body heat. e While outdoor, cover the body well and avoid exposure of body parts to outside cold temperature. Also protect eyes from cold and wind by wearing glasses or goggles. Other Tips I e Eat plenty of to maintain body heat. e Avoid touching metal, especially with wet hands. It can cause frost- bite in case of extreme cold temperatures. e Avoid over exertion and sweating. Sweating increases heat loss through evaporation. e Do not drink beverages that contain alcohol or caffeine and do not smoke tobacco while in the cold as it is harmful for lungs. 17.5.2 Preparedness: Advance Warnings Weather forecast issued by a number of countries includes day and night temperature forecasts with.specia1warnings for extreme temperature as and when likely to occur. Planning out-door activities, clothes, and other steps necessary to protect from likely extreme temperature conditions can help minirnise the thermal stress and adverse impacts on human health. In many countries Heat .- - 210 U~dcrstandirzgNatural Disasters

Index and Chill factors have been developed which are included in weather bulletins. These provide necessary guidelines to the locals on the extreme temperature conditions and related precautions. Weather bulletins for agriculturists include advance warnings for extreme ambient and ground temperatures, which may cause damage to crops. The parameters of the warnings or advisories vary as per the local climatic and geographic features. These, however, enable farmers to protect their crops from the intense cold and frost by initiating preventive measures to minimise the likely damages. Irrigating and making heating arrangements in-the field by burning dried leaves, tree branches and other wastes are generally resorted to. Prolonged heat wave may lead to severe damage to crops, parched land and other like situations and related disasters. With wirning for impendill/g heat waves, action needs to be initiated to conserve water, mulching and tilling of the soil for moisture retention, and irrigating the fields, which may help to minirnise the damages to the standingcrops. Similar action as per local needs should also be taken to protect livestock and poultry from the effects of extreme heat. Weather bulletins of some of the countries also cater to the specific industrial needs in respect of extreme temperatures which may affect their production and sales as well.

17.6 RESCUE AND RELIEF In case of illnesses due to exposure to heit or cold wave condition, the first effort should be aimed at restoring the normal body temperature of the victim. It helps to stabilise the condition of the patient and pxevent further complications. In case of life threatening conditions, immediate medical aid becomes necessary. Heat stroke or a condition of hypothenniaye emergency conditions and first aid should to be provided immediately till required medical aid is available. Heat Stroke e Move the victim to cool place, away fromgre'ct sunlight. * /' e Removeunnecessary clothing. .-- /I e Sponge the entire body of the victim with coo~(n6tcold) water and fan the person to lower body temperature through evaporation of water, ,,

9 Apply packs to groin, neck and armpits where large blood vessels lie close to the skin surface. e If breathing stops, start rescue breathing. o . Do not administer temperature lowering drugs like aspirin as these may cause complications. e If the patient is conscious and alert enough to swallow, give water or fluids to drink for dehydration.

The basic principle of the first aid in case of hypotherrnia and other injuries due to cold is to shift the patient to a warm area and wrap him well so as to conserve the body heat. Warm water or soup may be given every fifteen minutes or so. Small amounts of food may also be given if the patient is alert enough. It will help in generating heat in the body by the metabolic process. Caffeine and alcohol should be avoided. In case the victim starts losing alertness, immediate medical aid should be sought. The best thing to do during the extreme conditions is to avoid the thermal stress conditions by: Heat und Cold Waves 21 1

e Properly planning the outdoor activities during extreme temperature conditions. For instance, during heat wave, strenuous work should be avoided during the warmest part of the day. Much strenuous activity, which may cause sweating, needs also to be avoided during exposure to cold temperatures as evaporation of perspiration can further cool body and lower its temperature. Wear proper clothes to protect the body from exposure to extreme temperatures. e Avoid large and heavy meals during hot weather. Eat srnall meals at more number of times instead of full meals. During the cold, high energy may be preferred. e Alcohol and caffeine should be avoided during thel~nalstress conditions. e Drink plenty of water during heat wave.

17.7 CONCLUSION Heat and Cold waves conditions cause thermal stress to human body, which may lead to severe health problems andeven threat to life. These also have severe adverse impacts on agriculture and industrial productions. In many countries, heat and cold waves account for inore deaths than any other . In India, Orissa and Andhril Pradesh appear Inore vulnerable to heat waves apart from the plains of north India. Cold waves affect the northernmost parts of the country and the hilly areas. Many a times, cold wave conditions also prevail in the plains of north India. As human beings have great capacity to adapt the~nselvesto the climate in which they live, threshold value of extreme heat or cold wave temperatures, which rnay cause hazardous weather, are related to normal temperature values of the place and therefore vary from place to place. The frequency and severity of occurrence of heat and cold waves and their severity is dependent on factors like the geographical location and the c1im;ltic conditions of the areakegion. Many parts of the world are, however, affected every year with varying degrees of severity. Most vulnerable are those who are in the susceptible age groups like the very young and the old or the infirm with fragile health conditions, chronic invalids and those with weight and alcoholic problems which for apparent reasons have little adaptnbility to extreme temperature vuiritions. Weaker sectionsof the society who cannot afford to ensure protection against the extremes of weather are also among the

, easy targets of the conditions. The best way to prevent illnesses is, however, to avoid prolonged exposure to outdoor environment during heat and coid wave conditions.

17.8 KEY CONCEPTS : are high pressure areas on the weather charts. Chilblain : Localised i tchi ng, swelling and painful erythema caused due to exposure to cold and dampness. In some cases, it may cause blistering and ulceration. Basic cause of chilblains is sensitivity to cold. Other causes could be circulatory disturbances due to lack of physical activity and diet deficiency. Effective Temperature : The sensation of hotness of the air is dependent on the accompanying humidity present in the air, Very low humidity renders hot weather more bearable because evaporative cooling of the skin is more effective. High humidity makes hot weather unco~rifortnbleby inhibiting cooling. Effective Ulzderstanding Nut~rralDisasters

temperature, therefore, is based on the actual temperature and humidity level and is the temperahire of the saturated air which would provide the same sensation of comfort as the actual temperaare and humidity. Extra Tropics The region of higher latitudes on both sides of the Tropics. Frost bite Injury to the tissues under the skin due to exposure to cold. In seriouscases, the affected area becomes painfully inflamed and blistering lnay follow. It can cause death of inj~~redtissues and gangrene, which is a serious injury which may lead to amputation. Frostnip Numbness or blue-white skin colour temporarily caused by the exposure to cold temperat~lres.Usually skin surfaces of exposed areas, such as the face or fingertips, are affected. No~malfeeling andcolour rehlrn quickly with rewarming. Heat Cramps Muscular pain and spasm caused due to heavy exertion. Often this is the first signal indicating that the body is having trouble ' due to heat. Heat Exhaustion Typically occurs when body fl~lidsare lost by heavy sweating due to exercise or work in a hot place. Blood flow to the skin increases, causing blood flow to decrease to vital organs. Body temperature rises and the victim rnay suffer heat stroke if not treated urgently. In some countries the term Heat Index is used to define the relative effect of humidity on temperature. It provides the apparent temperature equivalent of the ambient air temperature under va~yinghumidity levels and are computed under light wind conditions. Heat Stroke A life threatening condi tion, which needs immediate medical assistance. In such condition the victim's temperature control system, which prod~~cessweating to cool the body, stops working. Body temperiturecan rise so high that brain damage and death may result if the body is not cooled quickly. Heat Syncope Mild form of heat illness when the blood flow to the-brain is ieduced, resultingin sylnptornsof fainting, dizziness, , increased pulse, restlessness, and voiniting. It is an elnergency condition caused by exposure to cold, which may lead to slow and shallow breathing, decreased level of conscio~~sness,confusion, aggressive behaviour, slurred speech and related conditions. Tropics Broadly the zone between the Tropic of cancer and the Tropic of Capricorn i.e. about 23% degree on either side of the equator. Wind Chill Bactor Like Heat Index or ~ffective'~ern~erahlrevalue for summer, common wjnter co~nfortindex is Wind Chill. It is obtained Heat and Cold Waves

by considering the effect on the temperature by the wind speed. It is a common experience that a windy winter day gives sensation of cold air temperature compared to actual ambient air temperature. It is actually the cooling power of a given combination of actual temperature and wind speed.

117.9 REFERENCES AND FLTRTHER READING Bhandari, S.G and R.R. Kelkar, Rai, "Effect of Cold Wave on Soil Temperture", Mausam, 35 (1 984). Goudie, Andrew S. and David J. Cuff (Eds.), 2002, Encyclopedia of Global Change Environmental Change and ~uman~ocidty (vol. I), Oxford University Press, USA.

McQueen, Henry R. and Cade~nanPope, "The Eastern States Heat Wave ofApril 20-28", 1957, , Jr., Monthly Weather Reviews, 85-4(1957). Posey, Carl A. Living Earth Book, Wind and Weather, Reader's Digest, 1994. Raghavan, K., "A Climatological Study of Severe Heat Waves in India", Indian Journal of and Geophysics, 1 7 (1 966). Raghavan, K., "A Climatological Study of Severe Heat Waves in India", Indian Journal of Meteorology and Geophysics, 18 (1967). ; Sarcar, N;C. Rai, and S.V. Datar, "Cold Waves in N.W. India", Indian Journal qfMeteorology and Geophysicr, 14 (1 963). ~ubbarama~ya,I. and D. A. Surya Rao, "Heat Wave and Cold Wave Days in Different States of India", Mausam, 27 (1 976).

17,10 ACTIVITY

1) Prepare a list of areas which are more prone to heat and cold waves in India, and explain why the land-locked areas experience extreme temperatures more frequently? 2) Explain the main preventive measures, which are mostly adopted by people in your area or as per your observation for protection fiom heat waves. 3) Visit a heat wave prone area and discuss the popular first-aid measures used by citizens for heat-stroke. 4) What are the symptoms of hypothemia?