Temperature to which absolutely dry air would have to be brought in order for it to have the same density as moist air, considered at the same pressure.

American Standard Code for Information Interchange. A standard code used to represent data using 8 bits (7 data bits and I parity bit) per character.

Balance of the water resources of a region, comparing precipitation and inflow with outflow, evaporation, and accumulation.

An instrument whose calibration can be determined by means of simple physical measurements on the instrument. Compare to secondary instrument.

Same as humidity strip.

A transducer which converts electromagnetic radiation in the infrared, visible, and ultraviolet regions into electrical quantities such as voltage, current, or resistance. Also called photo cell.

Instrument which measures and records the amount of evaporation over time.

The maximum rate at which precipitation can pass through the surface into the soil, for a given soil in a given condition.

The process in which incident radiation is retained by a substance. A further process always results from absorption.

A basic equation in night visual range theory, relating the illuminance of a point source of light to distance and the transmissivity of the atmosphere.

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.

Electromagnetic radiation lying in the wavelength interval between 0.8 micron and I millimeter. At the lower limit of this interval, the infrared radiation spectrum is bounded by visible radiation, while on its upper limit it is bounded by microwave radia ...

A temperature scale on which the freezing point of water equals 32

The pressure unit of the meter-ton-second system of physical units. equal to 10 millibars or 101 dynes per cm2.

General term for an instrument used to make direct measurements of visual range or measurements of the physical characteristics of the atmosphere which determine the visible range.

An optical instrument which consists of a sighting telescope mounted so that it is free to rotate around horizontal and vertical axes, with graduated scales so that the angles of rotation may be measured. Used to observe the motion of a pilot balloon.

A type of photoelectric photometer used to measure high-altitude winds on the assumption that stellar scintillation is caused by atmospheric inhomogeneities being carried along by wind near the tropopause level.

Small particle on which water vapor condenses.

An area of low atmospheric pressure which has a closed circulation that is cyclonic (counterclockwise in northern hemisphere and clockwise in southern hemisphere).

An instrument for taking photographs of an image of the sun in monochromatic light.