A line of equal or constant temperature.

A device for obtaining a continuous record of stage at a point on a stream. The most common recorders consist of a float-actuated pen which traces a record on a clock driven chart.

See constant-level balloon.

Central Processing Unit. The part of a computer which controls and directs all functions.

A plastic molding component formed by the reaction of phenol and formaldehyde. It can be heavily reinforced or "filled" with glass fibers or other materials. Phenolics are known for their high impact strength, excellent wear characteristics, and dimension ...

A synoptic code approved by the World Meteorological Organization in which the observable meteorological elements are encoded and transmitted in "words" of five numerical digits length. Often abbreviated synoptic code.

A local variation of the wind vector or any of its components in a given direction.

A halo phenomenon consisting of a horizontal circle passing through the moon, corresponding to the parhelic circle through the sun. Produced by reflection of moonlight from ice crystals.

A liquid-in-glass thermometer which uses an organic substance such as alcohol as the thermometer liquid. This type of thermometer has a low freezing point and a high coefficient of expansion. It is less accurate, however, than a mercury thermometer.

The record or trace made by a microbarograph.

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

An increase in the central pressure of a pressure system; opposite of a deepening. More commonly applied to a low rather than a high.

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 an object gives out as much radiation as it receives from its surroundings.

The height at which the maximum wind speed occurs, determined in a winds-aloft observation.

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.

Abbreviation for precipitation-evaporation quotient.

A small balloon whose ascent is followed by a theodolite in order to obtain data for the computation of winds aloft.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

Determined by weighing a special type of wooden stick that has been exposed in the woods, its weight being proportional to its contained water.