A thermopile used in some types of radiation instruments. See solarimeter.

A line of equal or constant temperature.

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

Solar radiation of selected wavelengths.

Same as parhelion.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

A unit of energy equal to 1.356joules.

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

The standard deviation (positive square-root of the variation) of the errors associated with physical measurements of an unknown quantity, or statistical estimates of an unknown parameter or of a random variable.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

The humidity transducinu element in a Diamond-Hinman radiosonde. Also called electrolytic strip.

A large plastic constant-level balloon for duration flying (in excess of 24 hours) at altitudes above 40,000 feet, used for the determination of wind fields and the measurement of upper atmospheric parameters.

See mote.

In aviation terminology, route or terminal weather conditions of sufficiently low visibility to require the operation of aircraft under instrument flight rules.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

The temperature at which the liquid and solid forms of a substance may exist in equilibrium at a given pressure (usually one standard atmosphere). The true freezing point of water is known as the ice point.

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

A system of physical units based upon the use of the meter, the metric ton (106 grams), and the second as elementary quantities of length, mass, and time, respectively.

A polarimeter utilizing a Wollaston prism as a polarizer and a Nicol prism as an analyzer.