| Section D | D index | 151-159 of 573 terms |
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deposit gaugeThe general name for instruments used in air pollution studies for determining the amount of material deposited on a given area during a given time.
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deposition velocityIn dry deposition, the quotient of the flux of a particular species to the surface (in units of concentration per unit area per unit time) and the concentration of the species at a specified reference height, typically 1 m. Typical deposition velocities for common gas phase pollutants (e.g., ozone, nitric acid) are of order 0.01–5 cm s−1.
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depositionProcesses by which traces gases or particles are transferred from the atmosphere to the surface of the earth. Atmospheric deposition is usually divided into two categories, wet deposition and dry deposition, depending on the phase of the material during the deposition process. Thus, in wet deposition, the gas or particle is first incorporated into a droplet and is then transferred to the surface via precipitation. In dry deposition, the gas or particle is transported to ground level, where it is adsorbed onto a surface. The surface can be the ocean, soil, vegetation, buildings, etc. Note that the surface involved in the dry deposition may be wet or dry—the “dry” in dry deposition refers only to the phase of the material being deposited.
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depression angle(Also called depression.) The angle between the horizon and a point below, measured along the arc that passes through the point in question and is perpendicular to the horizon. The depression angle is the zenith distance of the point in question minus 90°. Compare azimuth, elevation angle, zenith distance.
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depression storageWater temporarily retained in puddles, ditches, and other depressions in the surface of the ground, and eventually evaporated or infiltrated; the small-scale counterpart of closed drainage.
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