Heat islands in urban habitats are a pressing environmental issue driven by a confluence of factors. Urbanization, with its sprawling concrete jungles and diminished green spaces, exacerbates the phenomenon. The extensive use of heat-absorbing materials such as asphalt and concrete, coupled with the proliferation of buildings and roads, traps heat and reduces natural cooling mechanisms. Furthermore, the dense concentration of human activities, industries, and vehicles generate excess heat, intensifying the urban heat island effect. Additionally, the lack of adequate vegetation and water bodies further amplifies the problem by impeding evaporative cooling. Together, these factors create an environment where temperatures soar, posing significant challenges to urban inhabitants.
Tags: Important Geophysical phenomena.
Decoding the Question:
- In Introduction, try to briefly define an urban heat island.
- In Body, mention the causes of Urban heat island.
- Conclude by mentioning the significance and some effects of urban heating.
Answer:
Urban heat island may be defined as the local and temporary phenomenon in which certain pockets within a city are experiencing higher heat load than its surrounding area.This rise of heat basically happens due to buildings and houses of cities made up of concrete where the heat is trapped and not able to dissipate easily. The temperature variation can range between 3 to 5 degrees Celsius.
Causes of Urban Heat Island:
- Low Albedo Materials: According to Bouyer, Albedo is the ratio of the reflected solar energy to the incident solar energy. If the albedo of the urban surface is low, it will store more solar energy, causing an increase of urban temperature.
- Paved and Impermeable Surfaces: Paved over surfaces, such as roads and parking lots, can absorb solar radiation as heat.
- Thermal Mass: Buildings and infrastructures contain a lot of thermal mass, which results in absorbing a lot of heat during the day and are slow to emit it at night.
- Dark Surfaces: Dark roofs absorb more energy into the building as heat, so they get hotter than lighter-coloured surfaces.
- Lack of Vegetation: Plants and trees provide shade and keep the temperature cool through evapotranspiration. But areas with paved surfaces do not have this luxury.
- Climate Change: Extreme heat waves in urban areas lead to urban heat island formation.
- Urban Canopy: The heat reflected by a building is trapped by the buildings, which is known as the urban canopy. UHI is also formed due to the factor of urban canopy as well.
How can Urban Heat Islands be Reduced?
- Increase Area Under Green Cover: Plantation and effort to increase the area under green cover are the primary requirement to cut heat load within urban areas.
- Passive Cooling to Reduce Urban Heat Islands: Passive cooling technology, a widely-used strategy to create naturally ventilated buildings, can be a vital alternative to address the urban heat island for residential and commercial buildings.
Several other factors such as, Wind Blocking, Increased Use of Air Conditioner, Air Pollutants, Human Gathering, etc., also contribute to the formation of the UHI. During winter and summer the temperature difference is often greater at night than in the daytime as an effect of the UHI. Increased temperatures as outcomes of UHI can adversely affect human health, hence, urban planning is the need of the hour.
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