The primary drivers of the UHI effect stem from the fundamental changes humans make to the natural landscape during urbanization:

• Low Albedo Materials (Heat Absorption): Cities are built with vast amounts of dark surfaces like asphalt, concrete, and conventional dark roofing materials. These materials have low albedo (low reflectivity), meaning they absorb and store solar radiation (heat) during the day rather than reflecting it. This stored heat is then slowly released back into the air at night, which is why the UHI effect is often most noticeable after sunset.

• Lack of Vegetation and Evapotranspiration: Rural areas benefit from natural cooling mechanisms provided by trees and vegetation. Plants cool the air through evapotranspiration, a process where they release water vapor from their leaves, which consumes energy and cools the surrounding air (similar to human sweating). Cities replace these natural coolers with impervious surfaces, eliminating this cooling effect.

• Urban Geometry (The “Urban Canyon”): Tall buildings lining narrow streets create what is known as the urban canyon effect. These vertical walls absorb heat and then re-radiate it onto the street and sidewalks. Furthermore, the buildings and their concentration can block wind flow, preventing the hot air from being ventilated and replaced with cooler air from outlying areas.

• Waste Heat (Anthropogenic Heat): All human activities generate heat. In densely populated cities, this anthropogenic heat from sources like vehicle exhaust, industrial processes, and especially the exhaust from air conditioning (HVAC) systems is concentrated, further increasing the local ambient temperature.