Same as constant-level balloon.

Automated Weather Observing Station. A self-contained weather station designed to make aviation weather observations without operator involvement.

An instrument for measuring the pressure of the atmosphere. The two principle types are aneroid and mercurial.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

Any sudden and heavy rain, almost always of the shower type.

A hygrometer in which the sensitive element is a strand or strands of human hair, the length of which is a function of the relative humidity of the air.

Precipitation from a cumuliform cloud. Characterized by the suddenness of beginning and ending, by the rapid change in intensity, and usually by a rapid change in the condition of the sky. The solid or liquid water particles are usually bigger than the co ...

The upper surface of a column of liquid.

A mercury barometer designed for use aboard ship. The instrument is of the fixed-cistern type (see Kew barometer). The mercury tube is constructed with a wide bore for its upper portion and with a capillary bore for its lower portion. This is done to incr ...

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

A hypothetical temperature characterized by a complete absence of heat and defined as 0 K, -273.15 C, or -459.67 F.

A set of weekly colored rainbow arcs sometimes discernable inside a primary rainbow.

A measure of the intensity of gusts given by the ratio of the total range of wind speed between gusts and the intermediate periods of lighter wind to the mean wind speed, averaged over both gusts and lulls.

Same as parhelion.

The process in which incident radiation is retained by a substance. A further process always results from absorption.

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 Sunshine recorder of the type in which the time scale is supplied by the motion of the sun. The instrument, which is pointed at the celestial pole, consists of a hemispherical mirror mounted externally on the optical axis of a camera. The lens of the ca ...

A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

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

Physical equipment used in data processing. Compare to firmware, software.