An absolute temperature scale with the degree of the Fahrenheit scale and the zero point of the Kelvin scale. The freezing point of water equals 491.69

Precipitation caused by the ascent of moist air over an orographic barrier such as a Mountain range.

A device, similar to a potometer, for measuring transpiration, consisting of a vessel containing soil in which one or more plants are rooted and sealed so that water can escape only by transpiration from the plant.

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.

A motorlike device containing a rotor and a stator and capable of converting an angular position into an electrical signal, or an electrical signal into an angular position. When several synchros are correctly connected, all of the rotors will align thems ...

The level at which ice crystals and snowflakes melt as they descend through the atmosphere.

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

The stage on a fixed river gauge at which it is necessary to begin issuing warnings or river forecasts if adequate precautionary measures are to be taken before flood stage is reached.

See standard atmosphere.

An instrument for measuring differences of electric potential.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

Same as fogbow.

The statement that the viscosity of air is independent of the density of air.

Defect in the action of an aneroid barometer resulting in a sluggish adjustment of the index toward the correct reading when the barometer is subjected to a large and rapid change in pressure.

That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

Electromagnetic radiation of shorter wavelength than visible radiation but longer than x-rays, between 0.02 and 0.4 micron (200 and 4000 angstrom).

A common type of liquid-inglass thermometer, used, in meteorology, in psychrometers and as a maximum thermometer.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

A special type of radar target, usually a comer reflector, tied beneath a free balloon and designed to be an efficient reflector of radio energy.