Same as dropsonde.

General term for an instrument used to make direct measurements of visual range or measurements of the physical characteristics of the atmosphere which determine the visible range.

An increase or amplification. There are two general usages of the term in radar meteorology: (a) antenna gain (or gain factor) is the ratio of the power transmitted along the beam axis to that of an isotropic radiator transmitting the same total power; an ...

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

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

The algebraic difference between the upper and lower limits of the measuring range of an instrument, i.e. a thermometer with a range of -35 to 50

See feed.

A modification of the dew cell used in radiosonde equipment.

Cathode Ray Tube. A display element, consisting of a vacuum tube and screen, used with computers.

The energy of any type of electromagnetic radiation. Also called radiation.

The measurement and computation of wind speeds and directions at various levels above the surface of the earth. Methods include pilot balloon observations, rabals, rawin or rawinsonde observations, radar tracking, or acoustic sounding.

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern

The stage on a fixed river gauge at which it is necessary to begin issuing warnings or river forecasts if adequate precautionary measures are to be taken before flood stage is reached.

An instrument used to measure and record earthquake vibrations and other earth tremors.

Same as evaporative power.

National Centers for Environmental Prediction. Central computer and communications facility of the National Weather Service; located in Washington, DC.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

The elevation of the water surface in a stream as measured by a river gauge with reference to some arbitrarily selected zero datum.

The source of illumination for an antenna reflector. Also called antenna feed.

In meteorology, an area of low pressure; a low or trough.