Introduction
- Simply stating, Urban Heat Island (UHI) is defined as drastic increase of urban temperature compared to their rural surroundings.
- It is a metropolitan area whose temperature is significantly warmer/hot compared to its surrounding areas
- Moreover, the name itself implies that it is a condition where the urban area turns to a heat island due to different factors
- This concept of UHI can be considered as one of the most unambiguous and flawless example of climate change due to anthropogenic sources
- It is estimated that approximately three billion people in the world are suffering from the consequences of UHI every day and this number is going to increase significantly in the coming days
Variation in magnitude of Urban Heat Island (UHI)
- The magnitude of UHI varies as per the time and season
- Hotness is more in the urban areas after 3-4 hours of sunset and during the monsoon period. However, discrepancy can be seen even in the urban areas as those areas which have more green space and less anthropogenic heat are less hot compared to those areas with lesser green spaces and more anthropogenic heat.
- The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings
- Temperature difference in urban heat island is larger at night than during the day and larger in winter than in summer days
Some major factors contributing to Urban Heat Island
- Physical properties of building materials, building geometry and design
- Increased and uncontrolled industrialization
- Anthropogenic heat sources
- Decreased Evo transpiration
- High population
- Urban cityscape
- 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
Impacts/effects of Urban Heat Island
Health Effects:
- Emergence of infectious diseases
- Extensive heat causing dehydration, heat exhaustion and heat syncope
- Respiratory difficulties, heat cramps and heat related mortality
- Circulatory and cerebrovascular effects like heat exhaustion, heat collapse and heat stroke
- Increase in morbidity and fatality, especially for those working in outdoor conditions
Other effects:
- 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
- Depleted water quality
- 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
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
- Eco-roofing
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