In today’s scenario, it’s imperative to know about Urban Heat Island Effect. With the fastening urbanization, this is the immediate threat we all are facing as a society. I stay in Gurgaon for the past 3 years and have witnessed such tremendous change in the infrastructure as well as climate. Less rainfall, more scorching summers are some of the prominent changes I have observed. There is a frivolous rise in pollution and population as well. As a result many new construction projects have come up prominently in Sohna road and nearby areas. Lot of corporate dwellings also states the glory of the city’s rising economical and social growth. But what many are missing out are the hidden hands of increasing environmental hazards, which are pulling the city backwards. One such hazard is UHI effect.
An 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. UHI is most noticeable during the summers and winters. The main cause of the urban heat island effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The less-used term heat island refers to any area, populated or not, which is consistently hotter than the surrounding area. Increase in heat within urban centers increases the length of growing seasons, and decreases the occurrence of weak tornadoes. The UHI decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems.
There are concerns raised about possible contribution from urban heat islands to global warming. Research on China and India indicates that urban heat island effect contributes to climate warming by about 30%. On the other hand, one 1999 comparison between urban and rural areas proposed that the urban heat island effects have little influence on global mean temperature trends. Wherein many studies reveal increases in the severity of the effect with the progress of climate change.
Luckily, since we know what causes the urban heat island effect, we can control it to a significant extent. Certain techniques reduce the demand for air conditioning and reduce energy bills. Because the dark surfaces and low albedo of urban structures heat the area, the logical solution would be to reverse this trend. Urban planners may do this by painting structures white, or other light colors. This basic technique goes a long way in reversing the urban heat island effect. However, some people don't like the idea of a glaring, all-white city. Low-reflectivity coating offers an alternative and comes in non-white colors. These kinds of coatings reflect invisible radiation without reflecting all light. So, they keep an object relatively cool without sacrificing its dark color.
One of the simplest ways includes trees, which in urban areas can help diminish heat, is shade. The Environmental Protection Agency (EPA) reports that shaded areas can be up to 20-45 degrees cooler than areas that lack shade. The extreme temperature discrepancy between shaded and non-shaded areas plays a huge part in the need for higher energy costs. Strategically planting trees around non-shaded buildings helps reduce the need for air conditioning. Lower energy costs also means fewer pollutants and greenhouse gas emissions, so shade plays a role in maintaining healthy air quality in addition to keeping people cool. Aside from shade and cooler temperatures, trees offer other ways to help clear the air of pollutants often found in abundance in urban areas. Trees absorb harmful pollutants like nitrogen oxide, nitrogen dioxide, and sulfur dioxide, while simultaneously releasing oxygen into the environment, says the N.Y. State Department of Environmental Conservation. Essentially, the leaves of trees "breathe in" the bad stuff and "breathe out" what we need, i.e. oxygen.
One fad that's gaining popularity is the installation of green roofs atop city buildings. This solution doesn't have anything to do with color. A "green roof" is simply a roof that includes plants and vegetation. Green roofs harness the same evaporative cooling effect that cities lose when they hack away vegetation. So a green roof not only prevents the building's roof from absorbing heat, but cools the air around it, offsetting the urban heat island effect to an extent. Many sustainable buildings use green roofs to reduce their reliance on energy consumption.
Several other methods help reduce the urban heat island effect as well. For instance, roofsprinkling is another evaporative cooling solution. Sprinklers on the roof wet the surface so that the air around it cools through evaporation. This system provides cooling by spraying water on the roof surface. The water evaporates and cools the surface. This is simple, and appear to be effective, but would not be a good choice in areas where water is in short supply. One study indicates that water use is around 100 gallons per day per 1000 sqft of roof area.
Installing some of these methods and also by being little cautious and conscious, we together can fight this UHI and can reduce the alarmingly raising temperatures in cities. It is very essential for our future as well as for our future generations. It’s all about just taking the first step right and then the saga will continue henceforth. So let’s start with our surroundings folk and make the nation follow.