Effects of Corrugated Temperature Sheets on Optical Propagation along Quasi-Horizontal Paths in the Stably Stratified Atmosphere
Abstract
Optical propagation through the clear atmosphere is affected by small-scale refractive-index fluctuations which are caused mainly by temperature fluctuations. In the stably stratified atmosphere, these temperature fluctuations are the result of a combination of (1) more or less homogeneous and isotropic turbulence and(2) non-turbulent, quasi-horizontal interfaces, or ``sheets''. Collocated in-situ and optical field measurements conducted in the atmospheric surface layer confirmed that angle-of-arrival fluctuations and irradiance fluctuations observed with large-aperture telescopes (36 cm aperture diameter) are consistent with theoretical predictions based on Taylor's frozen-turbulence hypothesis and the geometrical-optics approximation. Short-term (less than a few seconds) fluctuations are dominated by turbulence while longer-term fluctuations are dominated by horizontally extended sheets. Direct numerical simulations of isotropic turbulence showed very good agreement with the turbulence spectrum predicted by Hill's 1978model. A theoretical model of corrugated sheets was developed and analyzed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 11, 2015
- Accession Number
- AD1001853
Entities
People
- Andreas Muschinski
Organizations
- Northwest Research Associates