THE THEORIES, ORIGIN AND EFFECTS OF HEAT WAVE
ABSTRACT
A heat wave is a prolonged period of excessively hot weather which may be accompanied by high humidity especially in oceanic climate countries while definitions vary, a heat wave is measured relative to the usual weather in the area and relative to normal temperatures for the season. Temperature that people from a hotter climate consider normal can be termed a heat wave in a cooler area. The term is applied both to routine weather variations and to extraordinary spells of heat which may occur only once a century. Severe heat wave have caused catastrophic crop failures, thousands of deaths from hyperthermia and widespread power outages due to increased sue of air conditioning. A heat wave is considered extreme weather and a danger because heat and sunlight may overheat the human body. A definition based on Frich et al : heat wave duration index is that a heat wave occurs when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5oc (9oc), the normal period of abnormally and uncomfortably hot and usually humid weather. To be a heat wave such a period should last at least one day, but conventionally it last from several days to several weeks. In 1960, A.T. Burrows more rigidly defined a “hot wave” as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90oF(32.2oc). More realistically, the comfort criteria for any one region are dependent upon the normal conditions of that region. In the Netherlands, a heat wave is defined as a period of at least 5 consecutive days in which the maximum temperature in De Bolt exceeds 25oc (77oF), provided that on at least 3 days in this period the maximum temperature in de Bolt exceeds this definition of heat wave is also used in Belgium and Luxembourg.
CHAPTER ONE
1.1 ORIGIN OF HEAT WAVES
Heat waves form when high pressure a lift (from 10,000 – 25,000 feet (3000 – 7600metres) strengthens and remains over a region for several days up to several weeks. This is common in summer (in both Northern and Southern hemispheres) as the jet stream “follows the sun”. on the equator side of side of the jet stream, in the middle layer of the atmosphere is the high pressure area. Summer time weather patterns are generally slower to change than in winter as a result, this mid level high pressure also moves slowly. Under high pressure, the air acts as a dome capping the atmosphere, this cap helps to trap heat instead of allowing it to lift. Without the lift there is little or no convection and therefore little or no convective clouds (cumules clouds) with minimal chance for rain. The end result is a continual build up of heat at the surface that people experience as heat waves.
In the Eastern United States, a heat wave can occur when a high pressure system originating from the Gulf of Mexico and the Caribbean sea while hot dry air masses form over the desert Southwest and North Mexico.
The SW winds on the backside of the high continue to pump hot, humid gulfair northwestward resulting in a spell of hot and humid weather for much of the Eastern states.
In the western cape province of south Africa, a heat wave can occur when a low pressure offshore and high pressure inland combine to form a Bergwind. The air warms as it descends from the Karoo interior, and the temperature will about 10oc from the interior to the costs. Humidities are usually very low and the temperature can be over 40oc in summer south (51.5oc) was recorded one summer during a Bergwind occurring along the Eastern cape coastline.
1.2 OBJECTIVES OF THE STUDY
The general objectives of this projects to undertake a study on the theories, origin and effect of heat waves. Increased human morbidity and mortality, particularly among the elderly and infirm
To know the stress for out door workers
To increased bush fire risk
To know the in animals
To know the damage to crops and vegetation
To increased energy demand, e.g greater demand for air conditioning
To know the stress on energy supply infrastructure,
To increase demand for water e.g human consumption, cooling in power stations
To shifts in tourism preferences due to higher temperatures
1.3 AIM OF THE STUDY
To understand the health impact of heat waves and its effects
To assess the state of and gaps in current knowledge
To comment on current research methodology
To make evidence-based recommendation for public health intervention programmes
To highlight or pinpoint the direction of further research
1.4 SCOPE OF THE STUDY
This project work analyzes the theories, origin and effect of heat waves. And how heat waves is measured to become widely accepted, also how it is easily understood and how people associate extreme values with their experience.
1.5 DEFINITION OF TERMS
The theories, origin and effect of heat waves can also be ascribe to the following
Excess heat factor the combined effect of excess heat and heat stress calculated as an index provides a comparative measure of intensity, load, duration and spatial distribution of a heat wave event. Heat wave conditions exist when the EHF is positive. Combining the measures of excess heat and heat stress provides a measure of heat wave which ahs a strong signal to noise ratio. Low-impact heat waves register as low amplitude EHf vents. As the excess heat and heat stress temperature abnormalities increase, their product increases as a quadratic response to increasing heat load.
Multiplying these two indices quadratic signal is detected in high impact data.
Heat stress: This arises from a period where temperature is warmer, on average, than the recent past. Maximum and subsequent minimum temperature averaged over a have-day period and the previous 30 days are compared to characterize this heat stress in a second index.
Severe heat wave: An event where EHF values exceed a threshold for severity that is specific to the climatology of each location.