Marine Glossary

|| || || || ||

dew point

The temperature to which air must be cooled at constant pressure and constant water vapor content to reach saturation. Any further cooling usually results in the formation of dew or frost. See related discussion with further explanations and examples ART-13 on humidity. See also humidity.

A dew point "computer" is available in RES-10. Tables of dew point data are shown in G195 and G196. A sample graph of dew point and temperature changes with time, which can help predict fog, as shown in G160.

Note that for a given sample of air with a fixed percentage of water vapor, the dew point does not change when the temperature of that air changes, although the relative humidity does change. The fixed percentages of water vapor that correspond to specific dew points are shown in G179.

See also fog.