Natural Disaster. (1) See: correlation. (2) A measure of the persistence of eddy velocity as a function of time and space. Two types are distinguished. In the Eulerian correlation coefficient the time difference is zero, Vu,-2(yi) V *2(v2) where u is the eddy velocity. For homogeneous and homologous turbulence this correlation tensor depends only on the difference (y2 - y^ and when the turbulence this correlation tensor depends only on the difference (y2 -y^; and when the turbulence is isotropic, the tensor is spherically symmetric and Rg*. = R^u. In the Lagrangian correlation coefficient time and space are varied together in such a way that the same fluid parcel is being followed. Rl* (t) = "'(yiti) u'fob). VUi'2 (yiti) Vuk'2 (y2t2) When the flow is one-dimensional and the mean velocity much greater than the eddy velocity, then a fixed point experiences approximately the same sequence of fluctuations that a fluid parcel does. The Lagrangian correlation coefficient can then be converted into the Eulerian by a proper scaling. These correlation coefficients have the same form and meaning when any other fluctuating quantity is used, e.g., temperature or pressure. N.B. Refer to source to verify equation(s)