The GATE Grind

GATE 2025 ES – Question 32

Global and Regional Environmental Issues · Global Effects of Air Pollution · 1 mark · Multiple select

Which statements about urban environments are correct?

  1. Urban heat islands can worsen urban flooding by intensifying rainfall.
  2. Urban canyons increase ventilation by trapping heat, enhancing heat islands.
  3. PERT is always used to estimate economic impacts of heat-island mitigation.
  4. Urban surfaces generally emit more longwave radiation than rural surfaces, contributing to higher nighttime temperatures.

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Show answer and explanation

Correct answer: (A) Urban heat islands can worsen urban flooding by intensifying rainfall.; (D) Urban surfaces generally emit more longwave radiation than rural surfaces, contributing to higher nighttime temperatures.

Explanation

Urban heating can strengthen convection and rainfall under suitable conditions, so A is possible. Heat stored by urban materials is released at night; warmer surfaces emit more longwave radiation, consistent with the intended D. Canyons often restrict ventilation, so B’s causal statement is wrong. PERT is a project-scheduling method, not a mandatory economic appraisal tool. Select **A, D**; D summarizes nighttime heat release rather than identifying radiation as a net energy source.

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