The other day I went to the house of one of my relatives in a metropolitan city. Those were summer days and the outside cityscape was melting down by the scorching heat. I was one of the braves who decided to move out of their comfort zones and travel through the heat radiating concretes. Until when the driver started the bus, I was completely drenched in sweat. Even the moving bus didn’t help much, as the wind coming inside through the window was hot enough to dehydrate me all up.
As we crossed the concrete jungles and passed through the big trees and green fields, I felt much better, as if someone lowered the temperature setting. All the way through I observed that temperature increased around city area and slightly decreased in plantation portions. I remembered the concept of Urban Heat Island that was taught during my masters. And the other day I was experiencing it.
I observed the variations of temperatures in an open area, around the buses at the bus stand, in a small street, besides higher buildings and in a high traffic area. Indeed there was a variation. Many of us have observed this but very few of us know the exact reasons and effects of Heat Island Effect. So, let’s discuss it.
Heat Island Effect
Heat Island Effect or Urban Heat Island (UHI) is a phenomenon where there is an increase in temperature of the surrounding in a concrete city as compared to the areas with same climatic conditions but lesser human settlements. This can more readily be experienced than read about. Many people don’t even realize the phenomenon created by their buildings, roads, vehicles and population unless and until they are told about.
The main concept of UHI is the reflection of light or albedo. More the reflection of light or albedo, lesser will be the retention of heat and vice versa. The reflection of light from a substance depends upon its colour, darker an object more light it would absorb and more heat it would emit out. So, we can easily say that the darker colours of roads, pavements, buildings and their roofs readily absorbs more light and radiates more heat.
According to US Environment Protection Agency, the temperature a city can be 10℉ higher than the adjoining rural areas. Also, cars and air-conditioners contribute to the heating effect making the cities an island of heat.
The Urban Heat Island Effect is prominent during the night hours, when the atmospheric temperature decreases but the concrete cities radiate the heat they have absorbed the whole day, making the surroundings warmer. According to Roland Pellenq, Senior Research Scientist in MIT, the gridding pattern, density and layout of a city plays an important role in defining the temperature of that place. He suggested that if a city has a loose layout like a liquid molecule, then there are chances of less heat retention as compared to the tightly or orderly structured layouts which can absorb and radiate more heat. Also, there is a free movement of air in un-patterned cities as compared to disrupted air flows because of perpendicular gridding layouts of streets in an organised city.
There are many effects of Heat Island Effect that includes increase in air pollution, health problems, adverse impacts on other living beings and psychological discomforts.
How can we reduce Heat Island Effect
- Trees help to reduce the temperature by the phenomenon of evaporative cooling, in which the unused water vapours get evaporated into the atmosphere, reducing the surrounding temperatures. So, definitely planting more and more trees can help a lot in this scenario.
- Painting the roads, pavements, buildings and their roofs in lighter colours which absorbs less light can help in reducing UHI effect.
- Growing of plants and gardens atop of a building’s roof as a ‘Green Roof’ can also help in reducing Heat Island Effect.
- Using appliances with a good Energy Star rating will help in reducing the heat and pollution contributions from the appliance side.
- Reducing the use of air conditioners and cars can reduce the emissions of greenhouse gases such as carbon dioxide and nitrous oxides into the atmosphere, thereby reducing the temperature.
- Installation of a water body around or in-between a city can help in reducing the air temperature considerably, also keeping the city cooler than before.
The present and future of most of the living beings on earth is in the hand of humans. We have the potential to escalate the productivity of the mother earth or to demolish what she has already given us. We all have the power within us to change and create a better world for everyone around.