HR: 1340h
AN: U43B-1135    [Abstracts]
TI: Distinguishing Two-Dimensional from Three-Dimensional Turbulence In the Near-Earth Atmosphere
AU: * Tofsted, D
EM: dtofsted@arl.army.mil
AF: U.S. Army Research Laboratory, White Sands Missile Range, Nevada, NM 88002-5501, United States
AU: Klipp, C
AF: U.S. Army Research Laboratory, White Sands Missile Range, Nevada, NM 88002-5501, United States
AU: O'Brien, S
AF: U.S. Army Research Laboratory, White Sands Missile Range, Nevada, NM 88002-5501, United States
AB: As is well known, atmospheric turbulence effects follow a fractal -5/3rds power law for fluctuations in the inertial subrange cascade region of the spectrum. Many meteorological models invoke closure techniques to simulate the dissipation of energy at scales smaller than are resolvable at the model cell size. However these closure methods generally assume fully developed (three-dimensional) turbulence. However, recent analysis of data suggests that these closure techniques should consider both 2-D and 3-D turbulence influences. It is possible to assess the relative degree of 2-D and 3-D turbulence for a data set in a given time window by evaluating a parameter that assesses the invariants of the turbulent kinetic energy stress tensor. Through a multi-scale analysis, a length scale can be evaluated that implies a cutoff boundary scale between 2-D and 3-D turbulence domains. Diurnal data sets of near-surface conditions analyzed for this parameter indicate a distinctive daily pattern commencing at dawn with a significant increase in this length scale, indicative of strong morning mixing. This is followed by a decreasing scale pattern throughout the day until the following morning. Could this pattern be used in modeling of surface coupling, and are there propagation problems involving angle-of-arrival fluctuations that are influenced by 2-D turbulence?
DE: 4440 Fractals and multifractals
SC: Union [U]
MN: 2007 Fall Meeting