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 ...

The center of an area of high pressure, usually accompanied by anticyclonic and outward wind flow. Also known as an anticyclone.

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.

An aviation weather forecast for a specific flight.

A momentary decrease in the speed of the wind.

A vent used with pressure sensors to reduce the effect of wind on the pressure inlet. It is normally mounted remotely and connected to the sensor using airtight tubing.

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.

An early and once universal name for the mercury barometer.

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

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

The direction toward which the wind is blowing; with the wind.

Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. However, it is identical with the temperature of the air and may also be used in that sense.

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.

The change in barometric pressure within a specified period of time (typically 3 hours for meteorological observations).

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

The closeness of agreement among a number of consecutive output values measuring the same input value under the same operating conditions, approaching from the same direction. Usually measured as nonrepeatability but expressed as repeatability, a percenta ...

Same as dew-point hygrometer.

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

Similar to the spectroheliograph, but used for visual instead of photographic purposes.

Radiation coming from the solid angle of the sun's disc, as opposed to diffuse sky radiation, effective terrestrial radiation, or radiation from any other source. Direct solar radiation is measured by pyrheliometers.