This paper describes a newly designed Sun and Aureole Measurement (SAM) aureolegraph and the first results obtained with this instrument. SAM measurements of solar aureoles produced by cirrus and cumulus clouds were taken at the Atmospheric Radiation Measurement Program (ARM) Central Facility in Oklahoma during field experiments conducted in June 2007 and compared with simultaneous measurements from a variety of other ground-based instruments. A theoretical relationship between the slope of the aureole profile and the size distribution of spherical cloud particles is based on approximating scattering as due solely to diffraction, which in turn is approximated using a rectangle function. When the particle size distribution is expressed as a power-law function of radius, the aureole radiance as a function of angle from the center of the solar disk also follows a power law, with the sum of the two powers being 25. This result also holds if diffraction is modeled with an Airy function. The diffraction approximation is applied to SAM measurements with optical depths &2 to derive the effective radii of cloud particles and particle size distributions between ;2.5 and ;25 mm. The SAM results yielded information on cloud properties complementary to that obtained with ARM Central Facility instrumentation. A network of automated SAM units [similar to the Aerosol Robotic Network (AERONET) system] would provide a practical means to gain fundamental new information on the global statistical properties of thin (optical depth & 10) clouds, thereby providing unique information on the effects of such clouds upon the earth's energy budget.
The collision between the exhaust from the Primary Reaction Control System (PRCS) engines (870 pounds thrust) of the space shuttle and the ambient atmosphere has been observed from the Air Force Maui Optical Station (AMOS). Spectra have been obtained in the wavelength region near 630 nm. The temporal, spatial, and spectral distribution of the emission in this region has been recorded. The results reported here indicate that when the exhaust of the space shuttle interacts with the atmosphere in the ram direction, an intense, long-lasting emission at 630 nm due to O(1D --> 3p) is generated. A substantial amount of O(1D) is swept back onto the orbiter. Two processes are proposed for the formation of O(1D): (1) excitation of atmospheric O(3p) by collisions with the exhaust of the space shuttle engines; and (2) charge exchange between ambient O + and exhaust H20. Calculations using the SOCRATES code show excellent agreement with the data. 19,501
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