The frequency of a carrier wave.

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

Liquid water at temperatures colder than freezing.

Apparatus designed to measure the amount of precipitation falling in the form of snow. The device determines the weight of the snow or the volume of water after the snow melts.

Solar radiation of selected wavelengths.

An instrument for the measurement of the rate of ice accretion on an unheated body.

Same as pitot tube.

A vent used with pressure sensors to reduce the effect of wind on the pressure inlet. It is normally mounted remotely and connected to the sensor using airtight tubing.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

A unit of pressure used principally in oceanography. One decibar (10' dynes/cm2) equals 0.1 bar. In the ocean, hydrostatic pressure in decibars very nearly equals the corresponding depth in meters.

A small balloon whose ascent is followed by a theodolite in order to obtain data for the computation of winds aloft.

An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine by the action of the sun's rays upon blueprint paper. A type of sunshine recorder.

A basic equation in daytime visual range theory, relating the apparent luminance of a distant black object, the apparent luminance of the background sky above the horizon, and the extinction coefficient of the atmosphere, or the air layer near the ground. ...

The portion of the strearnflow during any month or year derived from precipitation in previous months or years.

Same as rain gauge.

The maximum distance, usually horizontally, at which a given object or light source is just visible under particular conditions of transmittance and background luminance.

An air-launched balloon designed to be released in the eye of a tropical cyclone, float within the eye at predetermined levels, and transmit radio signals for RDF positioning.

An instrument for studying, or examining substances in, polarized light. See Savant polariscope.

A decrease in the central pressure of a pressure system. Usually applied to a low rather than to a high.

Same as water year.