Correct Option
The correct option is (c) 2 and 3 only.
Explanation
The phenomenon where urban areas experience significantly higher temperatures than surrounding rural areas is known as the Urban Heat Island (UHI) effect. This thermal disparity is primarily driven by the physical properties of urban materials and the geometry of city structures, which alter the heat balance compared to vegetated rural landscapes.
Statement-wise Analysis
- Statement 1 is Incorrect: Concrete and metals used in buildings do not remain cool during the day. These materials have high thermal mass and conductivity, meaning they absorb and store significant heat from solar radiation during the day. This stored heat is released slowly at night, preventing the temperature from dropping as low as it does in rural areas.
- Statement 2 is Correct: Asphalt, used extensively in paving roads, is a dark material with a low albedo (reflectivity). It absorbs a large proportion of incoming solar radiation during the day. During the night, this absorbed energy is released as heat (terrestrial radiation), keeping the ambient temperature of the city higher than that of the countryside.
- Statement 3 is Correct: The arrangement of crowded high-rise buildings creates an "urban canyon" effect. These structures obstruct natural wind flow, which reduces cooling by convection. Additionally, the vertical surfaces reflect and re-radiate heat between buildings, effectively trapping warm air and preventing radiative cooling to the open sky.
Key Takeaway
Urban Heat Islands are caused by the replacement of natural vegetation with heat-absorbing materials (concrete, asphalt) and the complex geometry of buildings that traps heat and restricts air circulation.