Define Urban Heat Island and list out its causative factors and impacts. Suggest your solutions for evading urban heat islands.
Urban Heat Island:
- UHI is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities.
- The temperature difference usually is larger at night than during the day, and is most apparent when winds are weak.
- Excess heat arising from various sources like industries, home, agricultural burning in surrounding areas.
- Increased absorption of sunlight by the bricks and concrete materials of the city.
- The atmospheric pollution in the cities acts as a blanket in preventing outgoing radiation.
- Lack of vegetation in urban areas reduces the natural cooling effect.
- The tall buildings provides multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated (Urban Canyon Effect)
- Increased temperatures amplify energy demand for cooling systems contributing to higher electricity consumption.
- Increased energy demand results in huge emissions of greenhouse gases.
- Health is impacted due to general exhaustion, heat strokes, heat cramps, headaches and respiratory problems.
- It creates secondary impacts like changes in local wind patterns, precipitation rates and humidity, and formation of clouds and fog.
- It negatively impacts the fauna and flora present in urban areas.
- Using light coloured concrete, white roofs increase the albedo.
- Using green roofs (partially or complete vegetation over the roofs of buildings) results in insulation thereby reducing the air temperatures.
- Construction of resource-efficient and environmentally sustainable green buildings.
- Promoting urban forestry which results in a cooling effect.
- Promoting fuel efficiency to reduce greenhouse gas emissions.
- Urban heat islands should be cooled off with immediate effect for ensuring a healthy as well as productive climate.