The change in a performance characteristic caused by a change in a specified operating condition from reference operating condition, all other conditions being held within the limits of reference operating conditions.

The ratio of the existing amount of water vapor in the air at a given temperature to the maximum amount that could exist at that temperature. Usually expressed in percent.

in folklore, a name for fire.

The element directly responsive to the value of the measured variable.

A wave disturbance in airflow due to some barrier in the flow. i.e. a hill or mountain.

Any meteorological instrument, such as a radiosonde, in which the recording apparatus is located at some distance from the measuring apparatus.

The actual time during which physical events take place.

The depth below which the ground is saturated with water. No water table exists if the ground water is confined by an overlying impermeable stratum, as in the case of artesian ground water.

Same as mercury barometer.

The total infrared radiation emitted from the earth's surface. To be carefully distinguished from atmospheric radiation, effective terrestrial radiation, and insolation.

Either of two colored luminous spots that appear at points 22

A mercury barometer which measures atmospheric pressure by weighing the mercury in the column or cistern.

The maximum distance, usually horizontally, at which a given object or light source is just visible under particular conditions of transmittance and background luminance.

Dihydrogen oxide, molecular formula H2O.

See gust and peak gust.

See gain.

In general, the transformation of data from a "raw" form to some useable form. In meteorology, this often refers to the conversion of the observed value of an element to the value which it would theoretically have at some selected or standard level. The m ...

An apparatus, used in studying soil temperatures, for measuring the total supply of heat during a given period.

A weakly colored lunar halo identical in form and optical origin to the solar parhelion.

Rate of wind movement in distance per unit time.