Consider the following statements about temperature inversion: I. This happens when normal lapse rate gets inverted. II. Winter nights with cloudy skies are conducive for temperature inversion. III. Polar areas experience inversion throughout the year. Which of the statements given above are correct?

I is correct: temperature inversion is the reversal of the normal lapse rate, with temperature increasing (instead of decreasing) with height. II is incorrect: temperature inversion is favoured by CLEAR (cloudless) winter nights, because clouds trap outgoing terrestrial radiation and prevent rapid surface cooling, which is needed for inversion. Long, calm, dry, snow-covered conditions also help. III is correct: polar regions, owing to perpetually cold surfaces and weak insolation, experience temperature inversion almost throughout the year. Hence I and III are correct.