Urban heat islands

Published on 31 Jan 2025

An urban heat island (UHI) refers to the phenomenon where urban areas experience higher temperatures than their surrounding rural areas.

Causes of formation of urban heat island

Impervious surfaces: Urban materials like asphalt absorb and retain heat, causing elevated temperatures compared to natural surfaces.
Reduced vegetation: Urbanization diminishes greenery, reducing shade and cooling effects from transpiring plants.
Buildings and infrastructure: Tall structures obstruct airflow, trapping heat, and construction materials like concrete absorb and radiate warmth.
Heat from human activities: Industry, transportation, and energy release heat, contributing to urban warming.
Waste heat: Energy use for heating, cooling, and industry produces excess heat, elevating temperatures in urban areas.
Urban design and layout: City planning affects heat absorption and distribution; green spaces and street orientation impact urban temperature patterns.
Albedo effect: Dark surfaces absorb sunlight, while lighter ones reflect it. Urban areas with low albedo contribute to increased heat absorption.
Urban canyon effect: Tall buildings close together create canyons that trap heat, limiting ventilation and raising temperatures in enclosed spaces.

Mitigating urban island effect

Increase green spaces: Plant trees and create parks to provide shade and enhance evapotranspiration, cooling the environment.
Cool roofs: Use reflective or cool roofing materials to reduce solar heat absorption and minimize rooftop temperatures.
Permeable surfaces: Use permeable materials for pavements to allow water absorption, reducing surface temperatures.
Energy-efficient buildings: Design sustainable buildings with insulation and energy-efficient technologies.
Cool pavements: Utilize cool or permeable pavements to reflect sunlight and absorb less heat.

Green Infrastructure: Integrate bio swales and green corridors for storm water management and cooling

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