A reflecting type telescope with a 45

The direction, with respect to true north, from which the wind is blowing. Distinguish from magnetic wind direction. In all standard upper-air and surface weather observations, it is true wind direction that is reported.

See gain.

Apparatus designed to measure the amount of precipitation falling in the form of snow. The device determines the weight of the snow or the volume of water after the snow melts.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

An instrument for collecting liquid water from the atmosphere.

An instrument of the aspiration condenser type which measures the concentration and mobility of small ions.

An instrument used to measure the water vapor content of the air. A type of hygrometer. It consists of a wet-bulb and a dry-bulb thermometer. See aspiration psychrometer, Assmann psychrometer. hygrodeik, sling psychrometer.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.

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

A semiconductor which exhibits rapid and extremely large changes in resistance for relatively small changes in temperature.

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 ...

Literally "not wet", containing no liquid.

A transducer for converting thermal energy directly into electrical energy. It is composed of pairs of thermocouples which are connected either in series or in parallel. Thermopiles are used in thermoelectric radiation instruments when the output of a sin ...

An instrument for the measurement of the net flux of downward and upward total (solar and terrestrial) radiation through a horizontal surface.

Same as precipitation- effectiveness index.

The actual lifting force of an inflated balloon, usually expressed in grams.

The maximum difference in output for any given input (within the specified range) when the value is approached first with increasing, and then with decreasing, input signals. Caused by energy absorption in the elements of the measuring instrument. Usually ...