A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

See hydrologic accounting.

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

Conditions to which a device is subjected, not including the variable measured by the device. See normal operating conditions, reference operating conditions.

A mercury barometer designed for use aboard ship. The instrument is of the fixed-cistern type (see Kew barometer). The mercury tube is constructed with a wide bore for its upper portion and with a capillary bore for its lower portion. This is done to incr ...

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

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.

An old nautical term for mercury barometer.

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

The lowest temperature that can be obtained on a wet-bulb thermometer in any given sample of air. Obtained by evaporation of water (or ice) from the muslin wick. Used in computing dew point and relative humidity.

The gravity flow of water within soil.

Electromagnetic radiation lying within the wavelength interval to which the human eye is sensitive, the spectral interval from approximately 0.4 to 0.7 microns (4000 to 7000 angstroms). Bounded on the short-wavelength end by ultraviolet radiation and on t ...

An estimate of the temperature of an incandescent body, determined by observing the wavelength at which it is emitting with peak intensity (its color) and using that wavelength in Wien's law.

In general, any object that reflects incident energy. Usually it is a device designed for specific reflection characteristics.

Difference between the temperatures of the dry-bulb and the wet-bulb thermometers of a psychrometer.

The nautical mile is closely related to the geographical mile which is defined as the length of one minute of arc on the earth's equator. By international agreement, the nautical mile is now defined as 1852 meters.

A scale with the ice point at zero degrees and the boiling point of water at 80 degrees, with pressure of one atmosphere.

A wave resulting from the action of wind on a water surface.

A measure of the attenuation due to scattering, of light as it traverses a medium containing scattering particles.