Simulating halos and coronas in their atmospheric environment.
Models are developed that simulate the light and color of the sky and of circular halos and coronas as a function of atmospheric pressure, cloud height, width, and optical depth, solar zenith angle, aerosol concentration and size, and ozone content. Halos, coronas, and skylight are treated as singly scattered sunbeams that are depleted in their passage through the atmosphere and cloud. Multiple scattering is included only for background cloud light. Halos produced by hexagonal crystal prisms and coronas produced by monodisperse droplets are visible for cloud optical depths in the range 0.0003 <or= tau(cld) <or= 7 and are brightest and most colorful when tau(cld) is somewhat less than the cosine of the observer's zenith angle. When the Sun is low in the sky, halos and coronas can be bright only at smaller cloud optical depths and tend to be faint at their bottoms when produced in high cloud layers but can be bright at the horizon when produced by narrow cloud cells near ground level.
David Gedzelman
Stanley
S
Department of Earth and Atmospheric Sciences and NOAA CREST Center, City College of New York New York, New York 10031, USA. stan@sci.ccny.cuny.edu
D055580:Astronomical Phenomena; D001256:Astronomy / Q000379:methods*; D001272:Atmosphere; D018534:Earth, Planet; D008027:Light; D008962:Models, Theoretical; D010126:Ozone; D012542:Scattering, Radiation; D019445:Solar Activity; D016082:Solar System; D013472:Sunlight
D010126:Ozone