Optical Modeling of Visibility and Visibility Instrumentation Using Stratified Mie Theory.
Abstract
In this study a new method of matching stratified Mie theory to size-time-composition resolved impactor data is developed and applied to rural data. The new model is free of theoretical systematic errors which exist in the standard approach and also includes the effect of relative humidity in an alternate and improved format. A physical description based on the volume Mie coefficients is emphasized and a corresponding lognormal parameterization scheme is introduced. Both theoretical and experimental results indicate that aerosols in rm D_{p } < 2.5mu m dichotomous sampling protocols are not adequate to predict visible or ultraviolet extinction. Further, to the extent that size shifts occur within the accumulation mode, the experimental results also indicate a limited correlation between those aerosols responsible for visibility reduction and those that extinguish ultraviolet. Hence, in order to better understand and monitor the effect of anthropogenic aerosols on atmospheric visibility and ground level ultraviolet fluxes, we must routinely combine impactor data sets in discrete highly resolved size ranges with stratified Mie theory. In addition, highly instructional computer-generated three-dimensional surface plots are presented which convey the global theoretical characteristics of the Mie parameters, including extensions well into the strong absorption region.
- Publication:
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Ph.D. Thesis
- Pub Date:
- January 1992
- Bibcode:
- 1992PhDT.......128R
- Keywords:
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- Physics: Atmospheric Science; Physics: Optics; Physics: General