An instrument which measures the rate of evapotranspiration. It consists of a vegetation soil tank so designed that all water added to the tank and all water left after evapotranspiration can be measured.

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

An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.

A transducer which converts electromagnetic radiation in the infrared, visible, and ultraviolet regions into electrical quantities such as voltage, current, or resistance. Also called photo cell.

A momentary decrease in the speed of the wind.

In meteorology, an area of low pressure; a low or trough.

Wind with a speed between 41 and 47 knots (47 and 54 mph); Beaufort scale number 9.

An instrument consisting of a series of graduated cylinders possessing selective collection efficiencies. It is used for the measurement of quantities relating to the size distribution of cloud droplets.

The elevation of the water surface in a stream as measured by a river gauge with reference to some arbitrarily selected zero datum.

Same as dew-point hygrometer.

The rate of decrease of temperature with height when unsaturated air is lifted adiabatically (without exchange of heat with its surroundings). The decrease is due to expansion as the air is lifted to a lower pressure.

An aviation weather forecast for a specific flight.

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifteenth contact of the commutator, up to a number determined by the design of the commutator, and each fifth contact thereafter. This signal is t ...

check chamber-A chamber use to check the sensing elements of radiosonde equipment.

Any emission of light at temperatures below that required for incandescence.

An anemometer in which the sensor rotation is transmitted to a mechanical counter which directly integrates the air movement past the sensor. Used to determine total air passage (wind run). Average wind speed can be calculated from the difference between ...

The volume of liquid water evaporated per unit area in unit time. usually measured as the depth of liquid water lost per unit time from the whole area.

The maximum deviation of any points from a straight line drawn as a "best fit" through the calibration points of an instrument with a linear response curve. Usually expressed as a percentage of full- scale range.

An anemometer which measures wind speed in terms of the drag which the wind exerts on a solid body. See bridled-cup anemometer, normal-plate anemometer, pendulum anemometer.