A hygrometer which determines the amount of precipitable moisture in a given region of the atmosphere by measuring attenuation of radiant energy caused by the absorption bands of water vapor.

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.

Name given to the unit of pressure in the International System of Units (SI). Equal to 1 newton/meter2 or 0.01 millibar.

An increase or amplification. There are two general usages of the term in radar meteorology: (a) antenna gain (or gain factor) is the ratio of the power transmitted along the beam axis to that of an isotropic radiator transmitting the same total power; an ...

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern

A wind blowing in a direction perpendicular to the course of a moving object.

General name for an instrument designed to measure the vertical component of the wind speed. See anemoclinometer.

A system in which radar techniques are used to determine the range, elevation, and azimuth of a radar target carried a!oft by a radiosonde, so that wind data may be obtained along with the other meteorological data.

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

Tables prepared from the psychrometric formula and used to obtain vapor pressure, relative humidity, and dew point from values of wet-bulb and dry-bulb temperatures.

Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

A recording siphon barometer.

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.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

General term for any device that measures precipitation: principally a rain gauge or snow gauge.

A thermometer. the sensitive element of which consists of two metal strips which have different coefficients of expansion and are brazed together. The distortions of the system in response to temperature variations are used as a measure of temperature. It ...

Atmospheric layer throughout which there is no change of temperature with height, i.e. a zero lapse rate.

A line drawn through geographical points having the same pluvial index.

in folklore, a name for fire.

The intensity (flux per unit solid angle) of visible radiation weighted to take into account the variable response of the human eye as a function of the wavelength of light. Usually expressed in candles.