Companion to the wet-bulb thermometer in a psychrometer. Used to measure ambient air temperature.

meter-An instrument for measuring the transmissivity of the atmosphere; a type of transmissometer. It consists of a constant- intensity collimated light source located at a suitable distance from a photoelectric cell. Variation in the turbidity of the atm ...

A hygrometer which includes an arrangement for the time recording of atmospheric humidity.

Same as atmometer.

A c.g.s. (centimeter-gram-second) unit of mass. Originally defined as the mass of 1 cubic centimeter of water at 4

A type of atmometer. It is a pan used in the measurement of the evaporation of water into the atmosphere. The NWS Class A pan is a cylindrical container 48 inches in diameter and 10 inches deep.

Thermometer in which the difference in the rates of expansion with temperature of a liquid and its receptacle is used as a measure of the temperature. The liquid used may be ethyl alcohol, toluene, petroleum, or mercury.

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

Thermometer used for measuring the lowest temperature attained during a given interval of time, for example, a day.

A class of rain gauge in which the level of the collected rain water is measured by the position of a float resting on the surface of the water.

The meteorological visual range, which can be estimated from the average extinction coefficient using the Koschmieder equation.

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.

A fixed support for mounting maximum and minimum thermometers of the liquid-in-glass type. The support holds the thermometers at the correct operating attitude and also permits their rotation for resetting when desired.

Solar and terrestrial radiation directed downwards (towards the earth's surface); incoming radiation.

An instrument for measuring the frost point of the atmosphere.

Wind with a speed between 17 and 21 knots (19 and 24 mph); Beaufort scale number 5.

The value of the quantity measured, as indicated or otherwise provided by a measuring instrument.

Rain gauge which registers precipitation that is too light to be registered by ordinary recording of the depth of water from precipitation. Same as ombrometer.

Thermodynamic change of state of a system in which there is transfer of heat across the boundaries of the system. Compare to adiabatic process.

A term used to describe a sensor (or sensors), the associated transducer(s), and the data readout or recording device.