Research Report 111 VISUAL RESOLUTION AND OPTICAL SCINTILLATION OVER SNOW, ICE AND FROZEN GROUND PART II

摘要

The effects of turbulent fluctuations of atmospheric density are seen as rapid changes in the brightness of a distant light source (scintillation) and in the apparent position, size, and shape of distant objects (shimmer). An investigation of these effects in horizontal optical paths was conducted by measuring visual resolution, optical scintillation intensity and frequency, and wind and temperature pro¬files over snow, ice and ground surfaces. The data obtained over the various surfaces were analyzed to determine relationships between (1) visual resolution and meteorological conditions and (2) scintillation (intensity and frequency) and meteorological and surface conditions.nPrincipal results of the analysis of the resolution data obtained over snow and frozen ground showed that, for turbulent flow in stable stratification, visual resolution (1) deteriorated systematically as the vertical temperature gradient increased, (2) deteriorated with clear skies as the wind speed increased up to about 5 mph and then improved at higher wind speeds, and (3) was optimum and nearly independent of wind speed during low overcast cloudiness.