MEASUREMENT OF EXTINCTION-TO-BACKSCATTER RATIO FOR NEAR-SURFACE AEROSOLS

A method for measuring the local extinction-to-backscatter ratio of at mospheric aerosols is described and demonstrated using aerosols indige nous to the arid southwestern United States. The approach employs simu ltaneous observations from two separate devices: one a nephelometer (f or the extinction measurement) and the other a backscattersonde operat ed at ground level (for the backscatter measurement). Since the instru ments may be deficient in measuring the true scattering coefficients f or some aerosols, optical response models are employed to estimate the magnitude of possible errors and make modest corrections to improve t he accuracy of the final values. It is found that the measured extinct ion-to-backscatter ratio is similar to the values calculated from a si mple optical model employing homogeneous spherical aerosols with sizes and bulk composition comparable to the aerosol associated with the me asurements. Thus possible nonspherical particle scattering effects wer e not distinctly observed for the aerosols sampled.