The actual time during which physical events take place.

See bimetallic thermometer.

The general term for anemometers operating on the principle that the heat transfer to air from an object at an elevated temperature is a function of the air speed. Examples are the hot-wire anemometer and the katathermometer.

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 ...

A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

An instrument designed to record the duration of sunshine at a given location without regard to intensity. See Campbell- Stokes recorder, Jordan sunshine recorder, Marvin sunshine recorder, Pers sunshine recorder.

An evaporation pan in which the evaporation is measured from water in a pan floating in a larger body of water.

In Jeffreys' classification, a wind for which the pressure force exactly balances the viscous force, in which the vertical transfers of momentum predominate.

An instrument used to measure the water vapor content of the air.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

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.

An instrument for recording global solar radiation.

Eluding precise prediction, completely irregular.

A point (or line) on a scale used for reference or comparison purposes. In calibration of meteorological thermometers, for example, the fiducial points are 100

Of equal or constant pressure, with respect to either space or time.

The level at which ice crystals and snowflakes melt as they descend through the atmosphere.

The difference between the outgoing infrared terrestrial radiation of the earth's surface and the downcoming infrared counterradiation from the atmosphere.

Area of a computer or other device where various logic and control elements are interconnected. Often a printed circuit board into which other circuit boards plug at right angles.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.