Question

The Earth cools off at night much more quickly when the weather is clear than when cloudy. Why?

Short answer

In clear weather, there is a loss of radiation energy of the Earth, and during daytime, the Sun warms the Earth's surface. However, at night, the clouds act as an insulator and reduce radiation energy loss.

Step-by-step solution

Understanding the radiation cooling of the Earth

The Earth radiates energy, due to which the surrounding air near the surface of the Earth gets cooler. In the daytime, the surface of the Earth is hotter, and during nighttime, its surface becomes colder.

In radiation cooling, the Earth's surface loses heat by the process of thermal radiation.

Explanation for the Earth cooling more quickly at night during cloudy weather in comparison to the clear sky

The Earth emits radiation continuously and gets colder by radiating heat. When the weather is cloudy, the clouds behave as an insulator. It absorbs an amount of energy from the Earth’s surface, radiating the electromagnetic waves continuously from it.

The clouds then reflect some of the energy of radiation to the surface of the Earth. As a result, the radiation energy loss of the Earth is decreased during cloudy weather.

In contrast, during clear weather, the Earth radiates its energy without anything acting as an insulator. As a result, there is a greater loss of radiation energy.

So, the Earth cools more quickly at night during clear weather than cloudy weather.