Introduction

The skew-T/log-P thermodynamic diagram used to plot vertical profiles of atmospheric temperature, moisture, and wind. (See an example blank skew-T, which opens in a separate window.) It has been used for many decades to assess a variety of meteorological conditions, most notably atmospheric stability.
Data for the vertical atmospheric profiles, also known as sounding plots, come from numerous sources such as radiosondes, dropsondes, pibals, aircraft, NWP model output, and satellite sounders. To decode data messages generated from a particular data source, one should refer to the appropriate reference manual. While most soundings today are plotted electronically, the instructions in this module are also relevant for manually plotting data on a skew-T diagram.
Since pressure decreases logarithmically with increasing height in the atmosphere, the skew-T diagram has lines of constant pressure (isobars) spaced logarithmically. This leads to the skewed appearance of lines of constant temperature (isotherms). Thus the diagram is called a skew-T/log-P diagram and is frequently referenced (including hereafter in this module) as a skew-T diagram.
This section describes the various lines on the skew-T/log-P diagram and how data are plotted on it.