Diffuse solar radiation which has the same intensity in all directions.

Wind with a speed between 48 and 55 knots (55 and 63 mph), Beaufort scale number 10.

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

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

A current meter consisting of six conical cups, mounted around a vertical axis, which rotate and generate a signal with each rotation. Tail vanes and a heavy weight stabilize the instrument.

A local variation in the wind direction or speed. This condition can present danger to aircraft, especially at landing, when a sudden shift from headwind to tailwind can cause a rapid loss of airspeed and lift.

Formation of a single water drop by the union of two or more colliding drops.

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

Lacking a relationship to a time base or clock. In asynchronous communications, individual data characters are sent at an arbitrary rate.

The standard deviation (positive square-root of the variation) of the errors associated with physical measurements of an unknown quantity, or statistical estimates of an unknown parameter or of a random variable.

Any horizontal wind velocity tangent to the contour line of a constant pressure surface (or to the isobar of a geopotential surface) at the point in question.

A type of hygrometer which measures the water vapor content of the atmosphere by means of the absorption of vapor by a hygroscopic chemical.

The water volume within a specified portion of a stream channel.

Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

A psychrometer in which the ventilation is provided by a suction fan.

An evaluation of upper air temperature, pressure, and humidity from radio signals received from a balloon- borne radiosonde.

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern

The succession of stages through which water passes on the ground and in the atmosphere: evaporation from land or bodies of water, condensation to form clouds, precipitation, accumulation in the soil or in bodies of water, and re-evaporation.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

An instrument used to measure the water vapor content of the air.