A type of hygrometer which measures the water vapor content of the atmosphere by means of the absorption of vapor by a hygroscopic chemical.

That part of an audio-modulated radiosonde consisting of the baroswitch, the sensing elements, the reference elements, and the relay.

Instrument for measuring the depth of water from precipitation that is assumed to be distributed over a horizontal, impervious surface and not subject to evaporation.

Of equal or constant pressure, with respect to either space or time.

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

A small, moveable graduated scale adjacent and parallel to the main scale of an instrument. It provides a means for interpolating between the graduations of the main scale.

A small balloon used to determine the height of the cloud base. The height can be computed from the ascent velocity of the balloon and the time required for its disappearance into the cloud.

In a system of moist air, the ratio of the mass of water vapor to the total volume of the system. Usually expressed as grams per cubic meter (g/m3).

Same as precipitation-evaporation ratio.

Radio Direction Finder.

Apparatus using the combined simultaneous action of a bimetallic thermometer and a hair hygrometer to move a needle in front of a divided scale. fts construction permits dew point variations to be indicated approximately.

The wind speed and direction at various levels in the atmosphere above the level reached by surface weather observations.

A radiosonde which transmits the indication of the meteorological sensing elements in the form of a code consisting of combinations of dots and dashes.

A current meter consisting of six conical cups, mounted around a vertical axis, which rotate and generate a signal with each rotation. Tail vanes and a heavy weight stabilize the instrument.

A general term for instruments designed to measure the amount of cloudiness.

Wind with a speed between 41 and 47 knots (47 and 54 mph); Beaufort scale number 9.

An instrument for recording ocean waves. Most recorders are designed for recording wind waves, that is waves of periods up to about 25 seconds, but some are designed to record waves of longer periods such as tsunamis or tides.

The line-of-sight distance between two objects.

Determined by weighing a special type of wooden stick that has been exposed in the woods, its weight being proportional to its contained water.

Same as recording rain gauge.