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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 U U index 21-29 of 135 terms
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uncertaintyThe standard deviation of a sufficiently large number of measurements of the same quantity by the same instrument or method. Hence, the noncorrectable part of the inaccuracy of an instrument; it represents the limit of measurement precision. The uncertainty of an instrument is caused by the unpredictable effects upon its performance of such factors as friction, backlash, and electronic noise.
uncinusA cloud species unique to the genus cirrus. See cloud classification, cirrus uncinus.
unconfined aquifer(Also known as water table aquifer.) Aquifer with an upper boundary defined by the water table and the surface at atmospheric pressure.
undamped oscillationSee oscillation, damping.
undercastA cloud layer of ten-tenths (1.0) coverage as viewed from an observation point above the layer. The term is most generally used in pilot reporting of in-flight weather conditions.
undercoolingSame as supercooling.
undercurrentA current flowing underneath another current at a different speed or in the opposite direction.
underground iceSame as ground ice.
undermeltingThe melting from below of any floating ice.
undertowSee rip current.
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