Mass balance expressed per unit area, that is, with dimension [M L-2] or [M L-2 T-1]; see specific. The prefix 'specific' is not necessary in general. The units in which a quantity is reported make cl
ear whether or not it is specific. Specific mass balance may be reported for a point on the surface, a column of unit cross-section, or a larger volume such as an entire glacier or a collection of glaciers. In the latter two cases the term 'mean specific mass balance' has been used, although the adjective 'mean' is also not necessary. The definition of 'specific' apparently offered by Meier (1962) has led to some confusion. He wrote... Quantities measured at a point will first be discussed. [They] should all be prefaced by the word specific ...Specific budget terms have dimensions of [length] or [length]/[time]. The confusion arises because of the primacy given by Meier to water-equivalent dimensions ('[length]'). The adjective 'specific' indicates that the quantity has dimension [M L-2] or [M L-2 T-1], not that it is being measured at a point. The adjective 'point', as in point mass balance, should be used when clarity is needed. The unit of area lies in the horizontal plane, not a plane parallel to the glacier surface. For mass-balance purposes this rule applies even when the surface is vertical. For example, at a calving front the frontal ablation is equal to the mass of the entire volume lost by calving, melting and sublimation. If quoted as a specific quantity it is divided by the horizontal area over which the balance is to be stated, such as that of the entire glacier for a glacier-wide mass balance. The glaciological usage is not that which prevails in some other sciences, where often a specific quantity is either a dimensionless ratio of the value of a property of a given substance to the value of the same property of some reference substance, or is a quantity expressed per unit mass.
The ratio of the Volume of water which the porous medium, after being saturated, will retain against the pull of gravity to the volume of the porous medium.
1. The ratio of the mass of any substance to the volume occupied by it (usually expressed in kilograms per cubic meter, but any other unit system may be used); the reciprocal of specific volume.
An example of something such as a product or piece of work, regarded as typical of its class or group and used in the context of an experiment.
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A technique for generating a clear composite image of a celestial object blurred by atmospheric turbulence in which a large number of short-exposure photographs are mathematically correlated by a comp
uter. By comparing the behavior of the speckles in a series of images it is possible to approach the theoretical resolution of the telescope.
The measurement of surface velocity as the rate of displacement of correlated patterns of speckle, or noise, in successive radar-interferometric images of the glacier. See insar, radar. The speckle or
iginates from large numbers of statistically independent scatterers in the scene. Small 'chips' or windows from a later image are matched to a similar chip from an earlier image. Measured from the earlier chip, the distance to and bearing of the later chip that exhibits the greatest correlation with the earlier chip is taken to be the vector displacement that has accumulated between the dates of the images. Speckle tracking (e. G. Gray et al. 2001) is less precise than interferometric measurement of velocity but, relying only on image intensity rather than on both the intensity and the phase of the complex radar signal, is more robust. See feature tracking.