Urban heat islands concept, causes and effects

Urban heat islands concept, causes and effects

1. Module – 4 UNIT- IV – URBANIZATION & ENVIRONMENT 4.1 Urbanization 4.2 Problems of Migration in Urban Areas 4.3 Urbanization and pollution (Air and water) 4.4 Problems of soil and biodiversity in urban areas 4.5 Urbanization in relation to changing land use pattern 4.6 Urban heat islands 4.7 ‘smart cities’ in India

2. Concept of Urban Heat Island The climatic conditions of city areas are always different from their surroundings . Landsberg (1981) introduced the concept of ‘urban heat islands.’ An urban heat island, or UHI , is a  metropolitan area  that's a lot warmer than the rural areas surrounding it – National Geographic Urban heat island is the situation where built up areas, burning of fossil fuels (cooking, transportation) commercial activities, industrial processing etc . cause heating of the lower atmosphere in urban areas. As a result of above factors, the average temperature of the lower atmosphere in urban areas increases rapidly . The effect of this rise in temperature is strongly observed during day time .

3. Factors contributing heat islands The concentration of high rise buildings and roads are made up of cement and tar which releases high amount of radiation energy . Lack of dense vegetation in urban areas. High amount of air pollution . Burning of fossil fuels in industries, commercial areas and slums. Heavy traffic and atmospheric pollution cause by it. Cemented roads and paver blocks radiate more energy leading to temperature rise. Large amount of evaporation from water bodies in the city.

4. Increased and uncontrolled industrialization Anthropogenic heat sources Decreased Evapo -transpiration High population Energy consumption and lifestyle Enormous production of energy from sources like industry, vehicles and houses Built environment and concrete buildings as building materials are good insulators and can hold more heat

5. Urban Heat Islands in India (Source: The Hindu, 7/2/2020) Most cities in the country are turning into “urban heat islands” in all seasons during both day and night Mean daytime temperature of Surface Urban Heat Island (UHI Intensity) going up to 2 ° C for most cities. Kolkata, Pune and Guwahati where the urban areas are surrounded by large green cover in suburban regions, there is “ an enhanced cooling effect on surface.”

6. Effects of Urban Heat Islands Emergence of infectious diseases Extensive heat causing dehydration, heat exhaustion Respiratory difficulties , heat cramps and heat related mortality Circulatory effects like heat exhaustion , heat collapse and heat stroke Increase in fatality , especially for those working in outdoor conditions.  

7. Reduced labor capacity (Water loss of 1–2% of body weight can reduce labor capacity by 6–7% ) Reduced productivity Lower air quality as pollutants produced from vehicles, industries and people are trapped by the urban landscape Change in weather and climatic conditions Increased energy demand and consumption due to high demand of Air conditioners and fans Amplified emission of air pollutants and greenhouse gases Alter in ecosystem affecting the lives of animals and plants

8.  Strategies to decrease Urban Heat Island Use of light colored roofs and walls Afforestation and plantation in city areas Rooftop farming and agriculture Green parking lots Implementation of heat reduction strategies Lesser use of vehicles Car pooling Promotion of greener lands and parks in urban areas Grassy lands promotion

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