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<br />OO1l19C' <br /> <br />Convection. - <br /> <br />(1) In general, mass motions within a fluid resulting in transport and <br />mixing of the properties of that fluid. <br /> <br />(2) As specialized in meteorology, atmospheric motions that are pre- <br />dominantly vertical, resulting in vertical transport and mixing of atmos- <br />pheric properties. <br /> <br />Correlation. - The mutual relationship between variables or other entities. <br /> <br />Covariance. - The expected value of a product (see correlation). <br /> <br />Diffusion. - In meteorology, the exchange of fluid parcels (and, hence, the <br />transport of conservative properties between regions in space, in the appar- <br />ently random motions of a scale too small to be treated by the equations of <br />motion). <br /> <br />Downwind effects. - See extra-area effects. <br /> <br />Dry ice seeding. - The dispensing of dry ice pellets into supercooled clouds <br />for the purpose of transforming the supercooled droplets into ice crystals, <br />which then grow and fallout. Dry ice creates a sufficiently cold environ- <br />ment for droplets to undergo spontaneous nucleation. <br /> <br />Extra-area effects. - Any effects on response variable, such as precipitation, <br />in areas other than the primary experimental or target area. <br /> <br />Ground ~enerator. - In weather modification, almost invariably referring to <br />silver lodide smoke generators that are operated on the ground (as opposed to <br />airborne equipment). <br /> <br />Ice crystal. - Anyone of a number of macroscopic crystalline forms in which <br />ice appears, including hexogonal columns, hexogonal platelets, dendritic <br />crystals, ice needles, and combinations of these forms. <br /> <br />LWC (liquid water content). - The amount of liquid water (that is, not <br />counting water vapor) in a cloud, usually expressed as grams of water per <br />cubic meter of cloud volume. <br /> <br />Mesoscale. - In meteorology: having characteristic spatial dimensions <br />somewhere between 1 and 160 kilometers, usually implying between 8 and <br />80 k i 1 ometers . <br /> <br />Nucleating agent (or nucleant). - In cloud physics, any substance that serves <br />to accelerate the nucleation of cloud particles. Nucleating agents may <br />themselves be nuclei (silver iodide, salt, sulfur dioxide, dust) or they may <br />enhance the nucleation environment (dry ice, propane spray). <br /> <br />Nucleation. - Any process by which the phase change of a substance to a more <br />condensed state (condensation, sublimation, freezing) is initiated at certain <br />loci (see nucleus) within the less condensed state. <br /> <br />52 <br />