The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. In terms of the hydrologic cycle, the ...

The general term for dry atmospheric suspensoids, including dust, haze, smoke. and sand. Compare to hydrometeor.

A buoyant balloon rising freely in the atmosphere, as opposed to a captive balloon.

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

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 time required for an instrument to registe 63.2% of a step change in the variable being measured.

A line of equal or constant pressure.

An anemometer which derives wind speed from measurements of dynamic wind pressures. Wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static. This pressure dif ...

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

An instrument for measuring the ultraviolet in solar and sky radiation.

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

A type of anemometer in which the rotation of an element serves to measure the wind. Rotation anemometers are divided into two classes; those in which the axis of rotation is horizontal, such as the windmill anemometer, and those in which the axis of rota ...

Board that holds graph paper on which is plotted information obtained from a pilot-balloon observation.

The actual lifting force of an inflated balloon, usually expressed in grams.

See constant-level balloon.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.

A line drawn through geographical points having the same duration of sunshine (or other function of solar radiation) during a given interval of time.