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.

An instrument for recording global solar radiation.

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

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

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 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.

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

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

An instrument for measuring differences of electric potential.

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

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

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

An instrument which measures the effective terrestrial radiation. See Angstrom pyrgeometer.

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.

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

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

Same as fogbow.

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

The distance that an observer can see vertically into a surface-based obscuring phenomenon such as fog, rain, or snow. The distance estimate must be based upon ceiling balloon ascensions or ceiling light projector measurements.