A counterclockwise change in wind direction. Backing winds with height are indicative of cold air advection (CAA).

A type of cooling-power anemometer based upon the principle that the time constant of a thermometer is a function of its ventilation.

An instrument for taking photographs of an image of the sun in monochromatic light.

A unit that represents one degree of deviation from a reference point in the mean daily outdoor temperature (usually 65

A reversing thermometer (for seawater temperature) which is not protected against hydrostatic pressure. The mercury bulb is therefore squeezed, and the amount of mercury broken off on reversal is a function of both temperature and of hydrostatic pressure.

A graphical aid used in the reduction of data from a winds aloft observation.

Solar and terrestrial radiation directed upward (away From the earth's surface); outgoing radiation.

A hydrometeor consisting of a visible aggregate of minute water droplets suspended in the atmosphere near the earth's surface. Fog differs from cloud only in that the base of fog is at the earth's surface while clouds are above the surface.

An instrument used to determine atmospheric pressure or elevation by observing the boiling point of water or both liquids. The sensitivity of the hypsometer increases with decreasing pressure, making it more useful for high altitude work.

A component of the wind (often using Cartesian coordinates. i.e. X and Y wind vectors). Also, an arrow representing wind velocity, drawn to point in the direction of the wind and with a length proportional to wind speed.

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

Federal Aviation Administration.

A direct-vision nephoscope which is constructed in the following manner: a comb consisting of a crosspiece containing equispaced vertical rods is attached to one end of a column eight to ten feet long and is supported on a mounting that is free to rotate ...

Name applied to a class of instruments which measure the liquid content of the atmosphere.

A small, limited-capacity central processing unit contained entirely on one semiconductor chip.

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

The distance or length of flow of the air past a point during a given interval of time.

Old snow that has become granular and compacted as a result of melting and refreezing.

See hurricane beacon.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.