Marine Glossary

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air

1. The mixture of gases comprising the earth's atmosphere. Dry clean air is composed of about 78% nitrogen, 21% oxygen, and about 1% argon. Carbon dioxide makes up about 1/30th of 1%, and there are traces of other gases.

A typical sample of air will include variable amounts of impurities such as water vapor, suspended dust particles, smoke, pollen, etc.

The amount of water vapor in the air is between 0% in dry or frigid air and 4% in warm moist air, measured by volume. The amount of water vapor in the air is a key factor in the weather associated with that air. Typical water vapor concentration is about 1%. See also atmosphere and WXT ART-13 on humidity.

2. Often used by mariners to refer to the wind, i.e. wind of force 1 on the Beaufort scale (1-3 knots) is called light air. See WXT RES-21 for the Beaufort scale.