A rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.

A line drawn through points of equal humidity on given surface.

A line of equal or constant temperature.

Same as humidity strip.

A measure of the relative power, or of the relative values of two flux densities, especially of sound intensities and radar power densities. The decibel is derived from the less frequently used unit, the bel, named in honor of Alexander Graham Bell.

Federal Aviation Administration.

Occupational Safety and Health Administration. A regulatory office of the U.S. Department of Labor.

An atmometer consisting of a porous porcelain or ceramic container connected to a calibrated reservoir filled with distilled water. Evaporation is determined by the depletion of water in the reservoir.

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.

Hygrometer in which the dew (frost) point is determined by observing the temperature of an artificially cooled surface at the moment at which dew (frost) first appears on it.

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

An instrument for the measurement of the radon content of the atmosphere.

The meteorological visual range, which can be estimated from the average extinction coefficient using the Koschmieder equation.

The nautical mile is closely related to the geographical mile which is defined as the length of one minute of arc on the earth's equator. By international agreement, the nautical mile is now defined as 1852 meters.

Automated Local Evaluation in Real Time. Network of automatic rain gauges that transmit via VHF radio link when precipitation occurs. Some sites are also equipped with other sensors such as temperature, wind, pressure, river stage or tide level. More info ...

An instrument, dropped from high attitude and carried by a stable parachute. used to measure the vertical component of turbulence aloft.

The total of direct solar radiation and diffuse sky radiation received by a unit horizontal surface. Global radiation is measured by pyranometers.

An evaluation, according to set procedures, of those weather elements which are most important for aircraft operations. Always includes cloud height or vertical visibility, sky cover, visibility, obstructions to vision, certain atmospheric phenomena, and ...

A graphical representation of stage or discharge at a point on a stream as a function of time.

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.