Infrared Extinction Spectra of Some Common Liquid Aerosols.

摘要

Infrared extinction spectra in the 3- to 5-micrometers and 7- to 13-micrometers atmospheric 'window' regions have been obtained for smokes of petroleum oil, sulphuric acid, and phosphoric acid of varying droplet concentration, and for water fogs. Spectra were also obtained at 0.36 to 2.35 micrometers for petroleum oil and sulphuric acid smokes. Experimental results were compared, for sulphuric acid and water aerosols, to calculated values obtained from the Mie theory. Agreement was as good as plus or minus 10%. When absorbing smoke droplets are small compared to wavelength, very useful approximations apply and droplet clouds may be spectrally simulated by thin liquid films. In such cases, the imaginary component of refractive index may be approximated directly from aerosol spectra. At 12.5-micrometers wavelength, water fog extinction is nearly independent of droplet size distribution, suggesting a simple scheme for measurement of total liquid water content of an optical path.