Optical Turbulence at Kitt Peak National Observatory, Fred Whipple Observatory,Apache Point Observatory, Horace Mesa, and the Atmospheric Profiler Research Facility

摘要

The transverse coherence length r sub o derived from differential image emotionof stellar sources, was measured at three astronomical sites (Kin Peak National Observatory, Fred Whipple Observatory, and Apache Point Observatory), a high mesa (Horace Mesa), and in a desert basin (Atmospheric Profiler Research Facility) at White Sands Missile Range. Composite results of r sub o on the order of a few minutes are seen under convectively unstable conditions. The quiescent periods, neutral events, when local near surface adiabatic conditions occur, show substantial reductions in the fluctuations of the same quantity. Image motion results for night (stable) conditions display slowing and varying patterns with reduced short term (few minutes) variations. Measurements were taken using a suite of instrumentation probing the same volume of atmosphere. The instrumentation includes the Atmospheric Turbulence Measurement and Observation System, a sodar, a scintillometer, and tower mounted sensors. A time height display of sodar data, calibrated for the refractive index structure parameter, (C sub n)2 coupled with scintillometer measurements show the diurnal evolution of the boundary layer responding to the local heating cooling cycle and drainage flows from surrounding mountains. Several atmospheric features are seen and discussed in the results because they affect the nature of the patterns of r sub o. Of particular interest are the development of convection, changes in the capping inversion, thermal plume structures, neutral events, and wave turbulence interactions. Sinusoidal oscillations, identified as internal gravity waves, are seen in the night laminated structures.