The requirements of a particular application should be used as a guide in determining how to make measurements of vertical temperature difference in complex terrain.

The height ranges of interest are from stack top to plume height and from plume height to the top of the terrain feature.

The direct measurement of the complete temperature profile is often desirable but not always practical.

The alternatives for measuring the vertical temperature gradients are:

Tower measurement: A tower measurement of temperature difference can be used as a representation of the temperature profile. The measurement should be taken between two elevated levels on the tower (e.g. 50 and 100 meters). A separation of 50 m between the two sensors is preferred. The tower itself could be located at stack base elevation or on elevated terrain: optimum location depends on the height of the plume.

Balloon-based temperature measurements: Temperature profiles taken by balloon-based systems can provide the necessary information but are often not practical for developing a long-term data base.