Chapter 31, Problem 5TE

To determine

The reason for the formation of dew on the ground during clear, calm summer nights.

Answer to Problem 5TE

During clear and quiet evenings, the temperature at the ground or some surface close to the ground can turn out to be a lot cooler than the "surface temperature".

Explanation of Solution

The radiation of warmth away, starting from the earliest stage, is the reason for the dew. The cold air structures close to the ground, and being heavier than the air above, it stays above the ground. Temperatures at night are simply cooler than day temperatures. When the temperature decreases, it reduces the capacity of air particles to clutch water vapor.

This water vapor consolidates and falls on the closest surface. Since cold air is substantial air, without wind, the coldest air will remain closest to the ground, accordingly permitting surface temperature to keep on falling. Hence, under clear and quiet evenings, the ground temperature may fall beneath the point of solidification while the temperature estimated formally at was as yet above freezing.

Conclusion:

Therefore, during clear and quiet evenings, the temperature at the ground or some surface close to the ground can turn out to be a lot cooler than the "surface temperature".