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.

Amount of solar radiation incident, per unit area and time, on a surface which is perpendicular to the radiation and is situated at the outer limit of the atmosphere, the earth being at its mean distance from the sun. It equals approximately 2.00 ly/ min ...

A rainbow seen in the spray of the ocean. It is optically the same phenomenon as the ordinary rainbow.

An anemometer in which the sensor rotation is transmitted to a mechanical counter which directly integrates the air movement past the sensor. Used to determine total air passage (wind run). Average wind speed can be calculated from the difference between ...

The amount of moisture which, if available, would be removed from a given land area by evapotranspiration. Expressed in units of water depth.

An element that can control current without moving parts, heated filaments, or vacuum gaps.

That part of snow melt that reaches stream channels as runoff.

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifteenth contact of the commutator, up to a number determined by the design of the commutator, and each fifth contact thereafter. This signal is t ...

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

An instrument for measuring the extinction coefficient in water.

A type of cooling-power anemometer based upon the principle that the time constant of a thermometer is a function of its ventilation.

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.

To free something from the binding action of ice by warming it to a temperature above the melting point of ice. Also, a warm spell when ice and snow melt.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

A measure of the amount of "spin" (or rotation) in the atmosphere.

The process in which incident radiation is retained by a substance. A further process always results from absorption.

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

Same as an upper air observation, but commonly used to refer to a single complete radiosonde observation.

Physical equipment used in data processing. Compare to firmware, software.

An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.