Question

1. At what time of the day is the highest temperature recorded?
2. At what time of the day is the maximum insolation received?
3. The two time records are not the same. Explain the reason for the difference.

Answer 1

1. The highest temperature is recorded between 3 PM to 5 PM in the afternoon.
2. The maximum insolation is received at noon.
3. The two time records are not the same because insolation (incoming solar radiation) is maximum at noon when the Sun is highest in the sky. However, the Earth’s surface takes time to absorb the solar energy and then re-radiate heat (terrestrial radiation). This causes temperatures to keep rising even after noon, reaching the highest point later in the afternoon, between 3 PM to 5 PM, when outgoing terrestrial radiation is also at a peak. This lag between maximum insolation and the highest temperature explains the difference in timing.
   This effect also explains why the atmosphere stays warm even after the Sun begins to set, as the Earth continues to release heat absorbed during the day.