What is Thermodynamic Diagram?
Thermodynamic Diagram meaning Used interchangably with Thermodynamic Chart; a chart containing contours of pressure, temperature, moisture, and potential temperature, all drawn relative to each other such that basic thermodynamic laws are satisfied. Such a chart typically is used to plot atmospheric soundings, and to estimate potential changes in temperature, moisture, etc. if air were displaced vertically from a given level. A thermodynamic chart thus is a useful tool in diagnosing atmospheric instability.
reference: National Weather Service Glossary