Definition - What does Thermal Plume mean?
A plume is a substance which moves from a source into its surrounding area, such as a plume of smoke. A thermal plume is a plume that is specific to temperature alone. Therefore, a thermal plume involves a part of a particular substance such as water or atmosphere which is of a different temperature, usually an elevated temperature which is proceeding from a source and has not yet dissipated into the surrounding substance and equalized temperature.
Safeopedia explains Thermal Plume
An example of a thermal plume may include hot water moving upward from a heat source in a body of water, such as an underwater volcano. The heated water has yet to cool and dissipate into the cooler, surrounding water. Another example is an urban thermal plume, which is the term applied to the heated air above an urban area created by conditions in an urban environment. London, for example, is 3-9 degrees celsius hotter than the Home Counties.