Formation of a single water drop by the union of two or more colliding drops.

A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

Liquid water at temperatures colder than freezing.

A small anemometer with flat vanes which indicates the number of linear feet or meters of air which have passed the instrument during its exposure.

An instrument, for the recording of two or more meteorological parameters, in which the ventilation is provided by a suction fan.

The volume of liquid water evaporated per unit area in unit time. usually measured as the depth of liquid water lost per unit time from the whole area.

The general term for dry atmospheric suspensoids, including dust, haze, smoke. and sand. Compare to hydrometeor.

Navy Operational Global Atmospheric Prediction System. A global meteorological model operated by the Department of Defense.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

The record of an aneroid barograph.

A type of cooling-power anemometer based upon the principle that the time constant of a thermometer is a function of its ventilation.

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

Federal Aviation Administration.

An instrument used to reveal but not necessarily measure the presence of an electrical quantity. It is used to display the output of a sensing element after suitable amplification and modification. Sometimes called display.

A measure of the amount of "spin" (or rotation) in the atmosphere.

A type of atmometer. It is a pan used in the measurement of the evaporation of water into the atmosphere. The NWS Class A pan is a cylindrical container 48 inches in diameter and 10 inches deep.

Nested Grid Model generated every 12 hours by NCEP.

A device attached to a meteorological instrument to provide ventilation; usually a suction fan.

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

A device, similar to a potometer, for measuring transpiration, consisting of a vessel containing soil in which one or more plants are rooted and sealed so that water can escape only by transpiration from the plant.