The rising of cold water from the deeper areas of the ocean to the surface. This phenomena often occurs along the California coast during the spring and summer.

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

Emission or transfer of energy in the form of electromagnetic waves or particles.

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

Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

Quantitative Precipitation Forecast.

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

A measure, proposed by Angstrom, of the precipitation effectiveness of a region.

Pertaining to measurements or devices in which the output vanes in discrete steps, i.e. on-off or pulse signals. Compare to analog.

Transistor-Transistor Logic.

General term for an instrument which records the vertical electric current in the atmosphere.

See captive balloon, ceiling balloon, constant-level balloon, free balloon, hurricane beacon, kytoon, Moby Dick balloon, pilot balloon, radiosonde balloon, rockoon, skyhook balloon, transosonde.

The process of modifying some characteristic of a wave (the carrier) so that it varies in step with the instantaneous value of another wave (the modulating wave) in order to transmit a message. The modified characteristic may be frequency, phase, and/or a ...

A component of a radiosonde consisting of a series of alternate electrically conducting and insulating strips. As these are scanned by a contact the radiosonde transmits temperature and humidity signals alternately. The contact may be a baroswitch as in t ...

The level at which ice crystals and snowflakes melt as they descend through the atmosphere.

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

Same as dew-point hygrometer.

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

The record of a barograph.

Eluding precise prediction, completely irregular.