In radiometry, a measure of the intrinsic radiant intensity emitted by a radiator in a given direction.

See aneroid capsule.

An instrument used for measuring the specific gravity of a liquid.

Eluding precise prediction, completely irregular.

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 ...

The boundary between the troposphere and stratosphere, usually characterized by an abrupt change in lapse rate. Its height varies from 10 to 20 km. Regions above the tropopause have greater atmospheric stability than regions below.

Any conventional barometer fitted with an extended scale so that atmospheric pressure measurements may be made at both high and low altitudes.

An atmometer consisting of a porous porcelain or ceramic container connected to a calibrated reservoir filled with distilled water. Evaporation is determined by the depletion of water in the reservoir.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

Temperature based on an absolute scale.

A hydrometeor consisting of a visible aggregate of minute water and/or ice particles in the atmosphere above the earth's surface. Cloud differs from fog only in that the latter is, by definition, in contact with the earth's surface.

The stage, on a fixed river gauge, corresponding to the top of the lowest banks within the reach for which the gauge is used as an index. Compare to flood stage.

Value of soil moisture, expressed as a percentage of the mass of dry soil, below which a plant living in the soil dies by wilting.

Same as an upper air observation, but commonly used to refer to a single complete radiosonde observation.

The value of atmospheric pressure to which the scale of a pressure altimeter is set so as to indicate airport elevation. The altimeter setting is included as part of an aviation weather observation.

An area of low atmospheric pressure which has a closed circulation that is cyclonic (counterclockwise in northern hemisphere and clockwise in southern hemisphere).

An instrument which automatically determines the size distribution of raindrops.

An instrument for rapidly obtaining samples of airborne dust; a type of dust counter. Particles pass through a cylindrical chamber, are drawn at high velocity through a narrow slit, and then impinge upon a microscope cover glass located a short distance f ...

A type of directional antenna used on some types of radar and radio equipment consisting of an array of elemental, single- wire dipole antennas and reflectors.

A psychrometer in which the ventilation is provided by a suction fan.