A device for measuring the frequency of occurrence of atmospherics whose intensity is greater than a predetermined level.

A form of psychrometer with wet-bulb and dry-bulb thermometers mounted on opposite sides of a specialty designed graph of the psychrometric tables. It is so arranged that the intersections of two curves determined by the wet-bulb and dry-bulb readings -yi ...

A thermometer whose sensitive element has been made to resemble a black body by covering it with lamp black. The thermometer is placed in an evacuated transparent chamber which is maintained at a constant temperature. The instrument responds to insolation ...

A c.g.s. (centimeter-gram-second) unit of mass. Originally defined as the mass of 1 cubic centimeter of water at 4

Anemometer which measures wind speed by the speed of rotation of 3 or 4 hemispherical or conical cups, each fixed to the end of a horizontal arm projecting from a vertical axis. See condenser-discharge anemometer, contact anemometer. Compare to bridled-cu ...

A line of equal or constant temperature.

Generic term for rapid variations in apparent position, brightness, or color of a distant luminous. object viewed through the atmosphere.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

An instrument for the measurement of both solar and terrestrial radiation.

Same as humidity strip.

A pressure-plate anemometer consisting of a plate which is free to swing about a horizontal axis in its own plane above its center of gravity. The angular deflection of the plate is a function of the wind speed. This instrument is not used for station mea ...

An instrument for measuring the extinction coefficient in water.

Same as constant-level balloon.

Amount of solar radiation incident, per unit area and time, on a surface which is perpendicular to the radiation and is situated at the outer limit of the atmosphere, the earth being at its mean distance from the sun. It equals approximately 2.00 ly/ min ...

A self-recording instrument used on aircraft for the simultaneous recording of atmospheric pressure, temperature, and humidity.

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal forms.

An optical instrument which consists of a sighting telescope mounted so that it is free to rotate around horizontal and vertical axes, with graduated scales so that the angles of rotation may be measured. Used to observe the motion of a pilot balloon.

In folklore, a name for wind.

A decrease in the central pressure of a pressure system. Usually applied to a low rather than to a high.

Solar and terrestrial radiation directed downwards (towards the earth's surface); incoming radiation.