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

The combined processes by which water is transferred from the earth's surface to the atmosphere: evaporation of liquid or solid water plus transpiration from plants.

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

Same as dew-point hygrometer.

Ice crystal deposits formed by sublimation (conversion of water vapor directly to ice) when temperature and dew point are below freezing.

Wind with a speed between 41 and 47 knots (47 and 54 mph); Beaufort scale number 9.

A vent used with pressure sensors to reduce the effect of wind on the pressure inlet. It is normally mounted remotely and connected to the sensor using airtight tubing.

bucket rain gauge-A rain gauge where the precipitation collected by the receiver empties into one side of a chamber which is partioned transversely at its center and is balanced bistably upon a horizontal axis. When a predetermined amount of water has bee ...

A protocol similar to RS232 which makes use of differential transmission to provide high speed data transmission over significantly longer distances.

The water portion of the earth as distinguished from the solid part, called the lithosphere, and from the gaseous outer envelope, called the atmosphere.

The rate of decrease of temperature with height when unsaturated air is lifted adiabatically (without exchange of heat with its surroundings). The decrease is due to expansion as the air is lifted to a lower pressure.

Overflowing by water of the normal confines of a stream or other body of water, or accumulation of water by drainage over areas which are not normally submerged.

Liquid water at temperatures colder than freezing.

A hygrometer which determines the amount of precipitable moisture in a given region of the atmosphere by measuring attenuation of radiant energy caused by the absorption bands of water vapor.

An instrument for measuring radiant energy. It consists of an ether differential thermometer with blackened bulbs. One of the bulbs is exposed to the unknown radiation and the other to a black body source whose temperature can be varied. Equality of radia ...

An instrument used to measure changes in the level of the water in an evaporation pan. The gauge is normally placed in a Stillwell and adjusted so that the point of the hook just breaks the water surface. The change in water level is read on the attached ...

Downward scattered and reflected solar radiation, coming from the whole hemisphere with the exception of the solid angle of the sun's disc on a surface perpendicular to the axis of this cone.

See calorie.

A hypothetical body which absorbs some constant fraction, between zero and one, of all electromagnetic radiation incident upon it, which fraction is the absorptivity and is independent of wavelength. Compare to black body, white body.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the mass of dry air. For many purposes, the mixing ratio may be approximated by the specific humidity.