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.

A system of physical units based on the use of the centimeter, gram. and the second as elementary quantities of length. mass. and time.

The effect upon the measurement of rainfall caused by the presence of the rain gauge.

A device attached to a meteorological instrument to provide ventilation; usually a suction fan.

A unit of energy equal to 101 ergs or to 0.2389 calories.

Readily taking up and retaining moisture.

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

A clockwise change in wind direction. Veering winds with height are indicative of warm air advection (WAA).

The record obtained from a bolometer.

A barometer which measures atmospheric pressure using one or a series of aneroid capsules. Also called holosteric barometer.

A relatively small-scale, upward moving current of air.

A definite portion of a stream channel, commonly taken between two gauging stations, but may be taken between any two specified points.

An instrument for the measurement of both solar and terrestrial radiation.

The value of atmospheric pressure to which the scale of a pressure altimeter is set so as to indicate airport elevation. The altimeter setting is included as part of an aviation weather observation.

A numbering system using a base number of 2 and having only two digits: 0 and 1. The fundamental system of representing information with electrical pulses.

An instrument whose calibration is determined by comparison with an absolute instrument.

In meteorology, a deflecting force acting on a body in motion and resulting from the earth's rotation. It deflects air currents to the right in the northern hemisphere and to the left in the southern hemisphere, thus having an effect on wind direction.

The direction from which the wind is blowing, measured in points of the compass or in azimuth degrees.

A reversing thermometer (for seawater temperature) which is not protected against hydrostatic pressure. The mercury bulb is therefore squeezed, and the amount of mercury broken off on reversal is a function of both temperature and of hydrostatic pressure.

An instrument for photographing the corona and prominences of the sun at times other than at solar eclipse.