A hydrometeor consisting of an aggregate of microscopic and more-or-less hygroscopic water droplets suspended in the atmosphere. It reduces visibility to a lesser extent than fog. The relative humidity of mist is often less than 95 percent.

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

See hydrologic accounting.

Graduated fixed stake used in regions of abundant snowfall to facilitate the measurement of snow depth.

A device for measuring the river stage. Also called stream gauge.

Ragged low clouds, usually stratus fractus. Most often applied when such clouds are moving rapidly beneath a layer of nimbostratus.

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

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

A recording siphon barometer.

An aneroid barometer with a scale graduated in altitude instead of pressure units.

Operation mode of a communication circuit in which one end can only transmit and the other end can only receive.

An instrument, dropped from high attitude and carried by a stable parachute. used to measure the vertical component of turbulence aloft.

A systematic summary of the terms (inflow, outflow, and storage) of the storage equation as applied to the computation of soil-moisture changes, ground-water changes, etc. An evaluation of the hydrologic balance of an area. Also called basin accounting, w ...

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

The direction toward which the wind is blowing; with the wind.

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

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

A conically shaped, copper rain gauge shield.

A thermometer based upon the principle that the velocity of a sound wave is a function of the temperature of the medium through which it passes. Sonic thermometers possess very short time-constants and eliminate radiation error.

Random Access Memory. The memory of a computer which can be read and written into at any location without passing through preceding locations.