A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

See radar theodolite, radio direction-finder.

A particular pattern of snow sampler having an internal diameter of 1.485 inches so that each inch of water in the sample weighs one ounce.

A recording variometer.

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

A thin metal disc partially evacuated of air used to measure atmospheric pressure by measuring its expansion and contraction.

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

The change in the measured transducer output caused by changes in ambient temperature. Usually expressed a percentage of full scale.

The point (physical and/or electrical) where two distinct data processing elements meet.

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 ...

See bimetallic thermometer.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

A unit of energy equal to 1.356joules.

The wind speed and direction at various levels in the atmosphere above the level reached by surface weather observations.

In general, any self-recording instrument carried aloft by any means to obtain meteorological data.

A balloon-borne instrument for the simultaneous measurement and transmission of meteorological data. It includes transducers for the measurement of pressure, temperature, and humidity; a modulator for the conversion of the output of the transducers to a q ...

Instrument for measuring the depth of water from precipitation that is assumed to be distributed over a horizontal, impervious surface and not subject to evaporation.

Apparatus consisting of (a) standard radiosonde and radiosonde ground equipment to obtain upper-air data on pressure, temperature, and humidity, and (b) a self-tracking radio direction-finder to provide the elevation and azimuth angles of the radiosonde s ...

Water condensed onto objects at or near the ground, due to the fact that their temperatures have fallen below the dew point temperature of the surrounding air, but not below freezing.

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