A liquid-in-glass or liquid-in-metal thermometer using mercury as the liquid.

The actual time during which physical events take place.

An instrument which measures combined direct solar radiation and diffuse sky radiation. See pyrheliometer, Robitzsch actinograph. solarimeter. See also albedometer.

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

(1) The ratio of the speeds of a chemical reaction at two temperatures differing by 10

Either of two colored luminous spots that appear at points 22

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

To free something from the binding action of ice by warming it to a temperature above the melting point of ice. Also, a warm spell when ice and snow melt.

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.

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

A metallic element of atomic weight 200.6 1, unique (for metals) in that it remains liquid under all but very extreme temperatures.

in folklore, a name for fire.

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.

Wind with a speed between 22 and 27 knots (25 and 31 mph); Beaufort scale number 6.

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

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

A precipitation gauge consisting of a receiver in the shape of a funnel which empties into a bucket mounted upon a weighing mechanism. The weight of the catch is recorded as inches of precipitation.

Balance of the water resources of a region, comparing precipitation and inflow with outflow, evaporation, and accumulation.

Dihydrogen oxide, molecular formula H2O.

See gust and peak gust.