They dissipate rapidly as the pressure in the vortex returns to normal behind the aircraft. We will not be concerned with this type of contrail. The second type of contrail is the engine exhaust contrail, formed by exhaust water vapor, a by-product of the combustion process, bringing the air to saturation. These are the conspicuous contrails you probably have seen crossing the sky, especially during the winter. Proper analysis of the temperature, humidity, and pressure will allow you to determine the heights at which contrails will form.
Contrails can make an otherwise inconspicuous high flying aircraft very noticeable.
Our aircraft may wish to avoid flight altitudes conducive to contrail formation to decrease the probability of their detection. Stealth technology aircraft will especially wish to avoid producing contrails. Shipboard, the CIC officer and the OOD can use your analysis of contrail formation altitudes to aid visual detection of high-flying hostile aircraft. We have already identified the contrail scales and their values on the Skew T diagram earlier in this lesson. Given a specific level, you can use these scales, the temperature, and the humidity to determine if contrails will form.