Development and Verification of Experimental Databases for Pancakes Structures in Geophysical Flows

摘要

This research program aims toward investigating optical turbulence in stable stratified fluids. Optical turbulence arises during the propagation of electromagnetic waves through a random medium enduring refractive-index fluctuations, and is characterized by phase modulations (scattering) at wave fronts and diffraction-generated wave intensity fluctuations along the beam path. Electromagnetic transmissions in the atmosphere, such as the propagation of laser-beams or microwaves, are severely distorted by optical turbulence. Distortion is most profound in regions with high density gradients (stratification) and turbulence, such as the lower stratosphere and upper troposphere. Although the dynamics of stratified turbulence has been extensively studied in relation to such middle-atmospheric flows, very little attention has been paid to the properties of concomitant optical turbulence. On the contrary, optical turbulence in isotropic turbulent flows has been extensively studied but the practical utility of such studies to atmospheric electromagnetic transmissions is severely limited due to the strong anisotropy of stratified turbulence. This research addresses a number of key issues on optical turbulence in stratified turbulent flows by employing laboratory experiments and associated theoretical/numerical analysis. The proposed work is expected to contribute significantly to the USAF efforts to develop prediction schemes for laser-beam propagation in middle atmospheric layers via its Airborne Laser (ABL) Program.