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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | |
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First Edition Preface Second Edition Preface Acknowledgments
Section A A index 521-529 of 917 terms
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angle of incidence—The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) incident on a body and the local normal to that body (although this normal may not be well defined, as that for a cloud, e.g.). May also describe beams of particles in the broadest sense. Compare angle of arrival.
angle of minimum deviation—See minimum deviation.
angle of reflection—The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) reflected by a body and the local normal to that body (although this normal may not be well defined, as that for a cloud, e.g.). May also describe beams of particles in the broadest sense. See reflection.
angle of refraction—The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) refracted by an optically homogeneous body and the local normal to that body.
Angola–Benguela front—The boundary between the southward flowing Angola Current and the northward flowing Benguela Current. It is seen as a temperature front in the upper 50 m and as a salinity front to depths of at least 250 m.
Angola Current—A relatively strong southward current along the Angolan coast. The current forms the eastern side of a cyclonic gyre centered on 13°S, 4°E and is driven by the extension of the South Equatorial Countercurrent. It reaches to depths of at least 300 m and attains its maximum speed of 0.5 m s−1 just below the surface.
Ångström compensation pyrheliometer—An absolute instrument developed by K. Ångström for the measurement of direct solar radiation. The radiation receiver station consists of two identical manganin strips, the temperatures of which are measured by attached thermocouples. One of the strips is shaded, while the other is exposed to sunlight. An electrical heating current is passed through the shaded strip to raise its temperature to that of the exposed strip. The electric power required to accomplish this is a measure of the solar radiation. See actinometer, pyrheliometer; compare Ångström pyrgeometer.
Ångström pyrgeometer—An instrument developed by K. Ångström for measuring the effective terrestrial radiation. It consists of four manganin strips, of which two are blackened and two are polished. The blackened strips are allowed to radiate to the atmosphere while the polished strips are shielded. The electrical power required to equalize the temperature of the four strips is taken as a measure of the upwelling terrestrial radiation. See actinometer, pyrheliometer; compare Ångström compensation pyrheliometer.
Ångström turbidity coefficient—A measure of the turbidity of the atmosphere, equal to the aerosol optical depth at a wavelength of 1 μm.
angstrom—A unit of length equal to 0.1 nm, or 10−4 μm.
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