An instrument that shows changes in humidity.

An instrument used to determine atmospheric pressure or elevation by observing the boiling point of water or both liquids. The sensitivity of the hypsometer increases with decreasing pressure, making it more useful for high altitude work.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

Literally "not wet", containing no liquid.

The frequency of a carrier wave.

A unit of luminance or brightness equal to 1/d candles per foot'.