Morphology of atmospheric transparent inhomogeneities

Abstract

Observations are presented displaying the evolution of transparent inhomogeneities in the natural atmosphere. All results are for horizontal paths in the first few meters above ground level. Measurements were taken using both a schlieren optical system capable of sensing fine scale gradients of refractive index and an optical system sensing the fine structure of intensity scintillation over various path lengths. Laser sources were utilized for both systems, and a full description of the two optical systems is included. The schlieren system employs two high quality 10-in-diameter mirrors to produce the illuminated working section. Trade-offs between this and other schlieren optical system configurations are discussed. The intensity scintillation measurements were taken with a collimated laser beam projected on a target board. System characteristics including the CCD camera, sampled frame rates, exposure times, and data processing are discussed.The central problem addressed in this study is to identify the conditions when C. Taylor's "frozen turbulence" hypothesis is justified. The optically derived results are compared to results from previous studies using tower, aircraft, and tethered balloon measurements. Analyses presented include histograms, threedimensional displays, contour maps of features, and frame subtraction schemes.Simultaneous measurements of integrated path and point measurements of the refractive index structure parameter (C2) , and wind , are included in the results.

Scintillometer Wind Measurements over Complex Terrain

“…The performance of the different techniques has been theoretically and experimentally tested before. The peak technique is reported to be less accurate than the slope technique because the scintillation pattern decorrelates as it drifts past the sensors (Wang et al 1981;Eaton et al 1990). Frequency techniques have also been reported to be more accurate than covariance techniques (Wang et al 1981).…”