Final answer:
Clouds play a dual role, reflecting incoming solar radiation and trapping terrestrial infrared radiation—their presence results in cooler days but warmer nights compared to clear sky conditions.
Step-by-step explanation:
The temperature difference (T differ) between cloudy and clear conditions can be understood by considering the greenhouse effect. On a cloudy day, clouds reflect incoming solar radiation, leading to cooler surface temperatures. However, they also trap terrestrial infrared radiation emitted by Earth, which generally keeps surface temperatures warmer than they would be on a clear day.
Conversely, on a cloudy night, the clouds continue to act as a barrier for the Earth's infrared radiation going into space, thereby maintaining warmer night temperatures. On a clear night, the lack of cloud cover allows more of this infrared radiation to escape into space, resulting in cooler surface temperatures. This effect is so significant that clear summer evenings can lead to frost due to the rapid rate of heat transfer from the Earth's surface into the cold dark space.