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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 41-49 of 917 terms
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absolute stability—The state of a column of air in the atmosphere when its lapse rate of temperature is less than the saturation-adiabatic lapse rate. An air parcel displaced upward by an adiabatic process would then be more dense than its environment and would tend to sink back to its level of origin. Compare absolute instability.
absolute standard barometer—Barometer that provides absolute measurements of pressure without having to be calibrated. For example, large sylphon barometers with optical reading have been a preferred type of primary or absolute standard barometer.
absolute temperature extremes—Highest or lowest temperature observed over a specified period of observation used as a climatological record. See temperature extremes
absolute temperature scale—(Abbreviated A.) Same as Kelvin temperature scale.
absolute velocity—Velocity as measured in an absolute coordinate system; hence, in meteorology, the (vector) sum of the velocity of a fluid parcel relative to the earth and the velocity of the parcel due to the earth's rotation. The east–west component is the only one affected: where u and ua are the relative and absolute eastward speeds, Ω the angular speed of the earth's rotation, r the radial distance of the parcel from the center of the earth, and φ the latitude of the parcel.
absolute vorticity—1. The vorticity of a fluid particle determined with respect to an absolute coordinate system. The absolute vorticity vector is defined by 2Ω + ∇ × u, where Ω is the earth's angular velocity vector and u is the three-dimensional relative velocity vector. 2. The vertical component η of the absolute vorticity vector (as defined above) given by the sum of the vertical component of the vorticity with respect to the earth (the relative vorticity) ζ and the vorticity of the earth (equal to the Coriolis parameter) f:
absolute zero—The zero point of the Kelvin temperature scale, of fundamental significance in thermodynamics and statistical mechanics. It is the linearly extrapolated temperature at which the volume of an ideal gas at constant pressure would vanish. All real gases become liquid or solid at sufficiently low temperatures and maintain a finite volume. Absolute zero on the Kelvin scale corresponds to −273.15°C.
absolute—1. With respect to atmospheric motions, refers to an absolute coordinate system; for example, absolute vorticity as distinguished from relative vorticity. 2. In climatology, the highest or lowest recorded value of a meteorological element, whether at a single station or over an area, during a given period. It is most frequently applied to extremes of temperature: absolute maximum is the highest recorded shade temperature; absolute minimum is the lowest recorded. 3. See Kelvin temperature scale.
absorbance—Used mostly by chemists, the negative logarithm (base 10) of the transmittance of an absorbing sample, often corrected for reflection by its container. Despite its name, absorbance is a consequence of both scattering and absorption, although scattering is usually assumed to be negligible. To within a constant multiplier, absorbance is absorption optical thickness and depends on the physical thickness of the sample. Compare absorptance.
absorbed solar radiation—Solar radiation absorbed by the atmosphere's constituent gases, suspended material, clouds, or by the earth's surface.
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