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Spectraldiscrimination ofcoarse and fine modeoptical depth N. T. O’NeillT. F. EckA. Smirnov2003 год

Spectral discrimination of coarse and fine mode optical depth
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Аннотация: The recognition that the aerosol particle size distribution (PSD) is effectively bimodal permits the extraction of the fine and coarse mode optical depths (τ f and τ c ) from the spectral shape of the total aerosol optical depth (τ a = τ f + τ c ). This purely optical technique avoids intermediate computations of the PSD and yields a direct optical output that is commensurate in complexity with the spectral information content of τ a . The separation into τ f and τ c is a robust process and yields aerosol optical statistics, which are more intrinsic than those, obtained from a generic analysis of τ a . Partial (optical) validation is provided by (1) demonstrating the physical coherence of the simple model employed, (2) demonstrating that τ c variation is coherent with photographic evidence of thin cloud events and that τ f variation is coherent with photographic evidence of clear sky and haze events, and (3) showing that the retrieved values of τ f and τ c are well‐correlated, if weakly biased, relative to formal inversions of combined solar extinction and sky radiance data. The spectral inversion technique permitted a closer scrutiny of a standard (temporally based) cloud‐screening algorithm. Perturbations of monthly or longer‐term statistics associated with passive or active shortcomings of operational cloud screening were inferred to be small to occasionally moderate over a sampling of cases. Diurnal illustrations were given where it was clear that such shortcomings can have a significant impact on the interpretation of specific events; (1) commission errors in τ f due to the exclusion of excessively high‐frequency fine mode events and (2) omission errors in τ c due to the inclusion of insufficiently high‐frequency thin homogeneous cloud events.
Год издания: 2003
Авторы: N. T. O’Neill, T. F. Eck, A. Smirnov, B. N. Holben, S. Thulasiraman
Издательство: American Geophysical Union
Источник: Journal of Geophysical Research Atmospheres
Ключевые слова: Atmospheric aerosols and clouds, Atmospheric chemistry and aerosols, Atmospheric Ozone and Climate
Другие ссылки: Journal of Geophysical Research Atmospheres (HTML)
Maryland Shared Open Access Repository (USMAI Consortium) (PDF)
Maryland Shared Open Access Repository (USMAI Consortium) (HTML)