Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)

[摘要] Atmospheric aerosols directly affect climate by scattering and absorbingradiation. The magnitude of the impact is dependent upon the wavelength oflight, but is often estimated near 550 nm. When light scattering andabsorption by aerosols is approximated, the wavelength dependence of therefractive index for specific components is lost. As a result, climatemodels would have inherent uncertainties for aerosol contributions toradiative forcing when considering the entire solar spectrum. An aerosolextinction differential optical absorption spectrometer has been developedto directly measure aerosol extinction at mid-ultraviolet to near infraredwavelengths. The instrument consists of a spectrometer coupled to a closedWhite-type multi-pass gas cell with an adjustable path length of up toapproximately 20 m. Laboratory measurements of various gases are comparedwith known absorption cross sections. Additionally, the extinction ofmonodisperse samples of polystyrene latex spheres are measured and comparedto Mie theory generated with refractive index values from the literature tovalidate the new instrument. The polystyrene experiments also emphasize theability of the new instrument to retrieve the wavelength dependentrefractive index, especially in the ultraviolet wavelength regions wherevariability is expected. The spectrometer will be a significant advancementfor determining wavelength dependent complex refractive indices in futurelaboratory studies as well as provide the ability to monitor ambient aerosollight extinction.

[学科分类] 几何与拓扑