The role of multiple scattering in twilight zenith sky observations of atmospheric absorbers: Diurnal photochemistry and airmass factors
The ability to properly interpret UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or airmass factor, of light collected by the spectrometer is understood. In the case of direct light measurement, the airmass factor may be calculated from simple geometrical considerations for a spherical atmosphere. In the case of scattered light, a spherical radiative transfer model must be used. A simple single scattering model and a Monte Carlo radiative transfer scheme were developed to study the effects of multiple scattering, aerosol scattering, albedo and refraction on scattered light airmass factors. Stratospheric airmass factors are found to be relatively insensitive to multiple scattering, albedo, refraction and aerosol scattering by background aerosols at fairly short visible wavelengths (about 450 nm). Tropospheric airmass factors, on the other hand, are very sensitive to these processes. Ground albedo, refraction, multiple scattering and aerosol scattering are also important in determining photolysis rates of atmospheric species. It is found that one-dimensional photochemical model calculations of vertical column abundances of several stratospheric chemical constituents are relatively insensitive to changes in photolysis rates due to albedo, refraction and background aerosol scattering, although they are sensitive to multiple scattering. Following the June 1991 eruption of Mt. Pinatubo, OClO and BrO were observed at Fritz Peak Observatory for the first time ever. The radiative and photochemical effects of the presence of Pinatubo volcanic aerosols are examined using a one-dimensional photochemical model coupled to a spherical matrix inversion radiative transfer model. Although the heterogeneous removal of NO(x) is not explicitly considered in the photochemical model, the photochemical effects of NO(x) removal may be studied by prescribing the amount of NO(x) removed by heterogeneous chemistry.
- Research Organization:
- Colorado Univ., Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences
- OSTI ID:
- 6453639
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AEROSOLS
MULTIPLE SCATTERING
EARTH ATMOSPHERE
LIGHT SCATTERING
OPTICAL PROPERTIES
ALBEDO
BROMINE OXIDES
DAILY VARIATIONS
MATHEMATICAL MODELS
MONTE CARLO METHOD
NITROGEN OXIDES
OXYCHLORIDES
PHOTOLYSIS
REFRACTION
STRATOSPHERE
TROPOSPHERE
VOLCANIC GASES
VOLCANOES
BROMINE COMPOUNDS
CALCULATION METHODS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLORINE COMPOUNDS
COLLOIDS
DECOMPOSITION
DISPERSIONS
FLUIDS
GASES
HALOGEN COMPOUNDS
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
OXYHALIDES
PHOTOCHEMICAL REACTIONS
PHYSICAL PROPERTIES
SCATTERING
SOLS
VARIATIONS
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