Multi Wavelength Contrast Telephotometry: Instrument Design And Data Interpretation

William C. Malm; Kenneth O'Dell

doi:10.1117/12.956541

18 August 1978 Multi Wavelength Contrast Telephotometry: Instrument Design And Data Interpretation

William C. Malm, Kenneth O'Dell

Proceedings Volume 0142, Optical Properties of the Atmosphere; (1978) https://doi.org/10.1117/12.956541
Event: 1978 Technical Symposium East, 1978, Washington, D.C., United States

Abstract

A contrast telephotometer, capable of simultaneouly measuring the brightness of two adjacent objects at various wavelengths, was designed and constructed. The instrument was used to measure the contrast of Mormon Mountain (located 30 km southeast of Flagstaff, AZ) against the horizon sky. Measurements were initiated on September 11, 1974, and data taken through August 29, 1975 are presented here. A theoretical model was formulated to examine the dynamics of contrast variations as a function of observation angle, tropospheric and stratospheric aerosol extinction coefficients. Calculations and measurements indicate that while measurements in the blue portion of the visible spectrum are primarily sensitive to aerosol within the mixing layer, contrast measurements in the red portion of the spectrum are sensitive to aerosol above the mixing layer. The relationship between wavelength, contrast and vertical aerosol distributions is quite dependent on observation angle. Because contrast is related to both tropospheric and stratospheric aerosol concentrations, the instrument is well suited to measure contrast changes caused by spatial variations in aerosol concentrations that take place over hundreds of kilometers. Contrast is directly related to visibility and consequently the contrast telephotometer is also a direct measure of visibility as a function of spatially varying aerosol loads.

Citation Download Citation

William C. Malm and Kenneth O'Dell "Multi Wavelength Contrast Telephotometry: Instrument Design And Data Interpretation", Proc. SPIE 0142, Optical Properties of the Atmosphere, (18 August 1978); https://doi.org/10.1117/12.956541

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