Measurement of extinction-to-backscatter ratio for near-surface aerosols

A method for measuring the local extinction-to-backscatter ratio of atmospheric aerosols is described and demonstrated using aerosols indigenous to the arid southwestern United States. The approach employs simultaneous observations from two separate devices: one a nephelometer (for the extinction measurement) and the other a backscattersonde operated at ground level (for the backscatter measurement). Since the instruments may be deficient in measuring the true scattering coefficients for some aerosols, optical response models are employed to estimate the magnitude of possible errors and make modest corrections to improve the accuracy of the final values. It is found that the measured extinction-to-backscatter ratio is similar to the values calculated from a simple optical model employing homogeneous spherical aerosols with sizes and bulk composition comparable to the aerosol associated with the measurements. Thus possible nonspherical particle scattering effects were not distinctly observed for the aerosols sampled.