Same as parhelion.

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.

See mote.

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.

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

The atmospheric pressure computed using station elevation as the reference datum level. Station pressure is usually the base value from which sea level pressure and altimeter setting are determined.

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

A line of equal or constant temperature.

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

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

A unit of energy equal to 1.356joules.

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

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.

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

Same as water year.

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

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

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

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal forms.

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.