Thermal - Definition and Overview

This article is about the atmospheric phenomenon. For other uses of the term thermal, see thermal (disambiguation).

A thermal column (or thermal) is a column of rising warm air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection.

The size and strength of thermals are influenced greatly by the properties of the lower atmosphere (the troposphere). The most important factor is the amount of atmospheric stability. Generally, when the atmosphere is less stable thermal formation is more likely.

Thermals are often indicated by the presence of visible cumulus clouds. The rising air in a thermal cools as it ascends, until the water vapor in the air begins to condense into visible droplets.