An instrument designed to measure quantities of heat. Sometimes used in meteorology to measure solar radiation.

Integrated Flood Observing and Warning System. National Weather Service flood warning program.

A transducer which converts electromagnetic radiation in the infrared, visible, and ultraviolet regions into electrical quantities such as voltage, current, or resistance. Also called photo cell.

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.

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 ...

An anemometer utilizing the principle that the pitch of the aeolian tones generated by air moving past an obstacle is a function of the speed of the air. Largely a curiosity and has been put to no practical application in modem meteorology.

A unit of energy per unit area commonly employed in radiation theory. Equal to one gram-calorie per square centimeter.

Precipitation from a cumuliform cloud. Characterized by the suddenness of beginning and ending, by the rapid change in intensity, and usually by a rapid change in the condition of the sky. The solid or liquid water particles are usually bigger than the co ...

A reflecting type telescope with a 45

See standard atmosphere.

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.

A photometric unit of illuminance or illumination equal to one lumen per square meter

A recording weight barometer.

A measure of the intrinsic luminous intensity emitted by a source in a given direction. Luminance is a measure only of light. The comparable term for electromagnetic radiation in general is radiance.

A mercury-in-glass thermometer which records the temperature upon being inverted and retains its reading until being returned to the first position.

Precipitation composed of liquid water drops more than 0.5 mm in diameter, failing in relatively straight, but not necessarily vertical, paths. Compare to drizzle.

A thermometer, invented by James Six in 1782, which simultaneously indicates the maximum and minimum temperatures attained during a given interval of time. A U-tube min/max thermometer

Growth of a cloud or precipitation particle by the collision and union of a frozen particle with a super-cooled water drop.

A device that combines several separate communications signals into one and outputs them on a single line.

Wind with a speed between 11 and 16 knots (13 and 18 mph); Beaufort scale number 4.