A metropolitan area that is significantly warmer than its surroundings is referred to as an urban heat island (UHI).When cities replace natural land cover with dense clusters of pavement, buildings, and other surfaces that absorb and retain heat, urban heat islands are created. This has the effect of raising energy costs (for air conditioning, for instance), air pollution levels, and chronic conditions and mortalities brought on by the heat.
Heat is created by energy from dense population, cars, buses, and trains in big cities like New Delhi , Mumbai and Banglore.Urban heat islands develop in places with high activity levels and high population densities.
There are numerous causes of UHIs. A UHI is created when homes, businesses, and industrial structures are built close to one another. Generally speaking, building materials are excellent heat insulators. The areas close to buildings become warmer thanks to this insulation.
Heat islands form as vegetation is replaced by asphalt and concrete for roads, buildings, and other structures required to support growing populations. These surfaces absorb heat from the sun rather than reflecting it, causing surface temperatures and overall ambient temperatures to rise.The removal of trees and vegetation reduces the natural cooling effects of shade and water evaporation from soil and leaves (evapotranspiration)
Urban areas are densely populated, which means that many people are crammed into a small area. Buildings are built very closely together in urban areas. Engineers construct skyscrapers when there is no more space for an urban area to expand. Waste heat results from all the construction, and heat that escapes insulation has nowhere to go. In the UHI, it lingers inside and between structures. Nighttime temperatures in UHIs remain high. This is because buildings, sidewalks, and parking lots block heat coming from the ground from rising into the cold night sky. The temperature is warmer because heat is trapped at lowland areas.
Scientists are investigating how urban heat islands may contribute to global warming, the most recent pattern of climate change that includes the gradual warming of the Earth's temperature. When it's extremely hot, many of us rush to the fan or air conditioning. This is especially true in urban areas where urban heat islands exist. UHIs contribute to greater energy demands, putting a strain on energy resources. Rolling blackouts, or power outages, are common in UHIs. When utility companies do not have enough energy to meet their customers' demands, they initiate rolling blackouts. Urban Heat Islands act as a positive feedback mechanism.
Heat islands contribute to higher daytime temperatures, less nighttime cooling, and higher levels of air pollution. Heat-related deaths and illnesses such as general discomfort, respiratory difficulties, heat cramps, heat exhaustion, and non-fatal heat stroke are all caused by these factors.
How to Reduce effects of Urban Heat Island
Build green infrastructure improvements into regular street upgrades and capital improvement projects to ensure that your community continues to invest in heat-reducing practises.
Plant trees and other vegetation—Although space in cities is limited, small green infrastructure practises can be easily integrated into grassy or barren areas, vacant lots, and street rights-of-way.
Build green roofs—Green roofs are an excellent heat island reduction strategy because they provide both direct and ambient cooling. Green roofs also improve air quality by reducing heat island effects and absorbing pollutants.