MUELLER MATRIX FOR ATMOSPHERIC AEROSOLS AT CO2-LASER WAVELENGTHS FROMPOLARIZED BACKSCATTERING LIDAR MEASUREMENTS

The Mueller matrix (M) over tilde for atmospheric aerosol backscatteri ng in Utah (a desert environment) is derived from lidar-polarized back scattering measurements at CO2 wavelengths for a horizontal path a few meters above the ground. The Mueller matrix is nearly a diagonal matr ix, with m(11) = S-11, m(22) = (S-22 - S-33)/2, and m(33) congruent to -m(22), as is expected for randomly oriented aerosols with axial symm etry. The ratio m(22/)m(11) is approximately 0.75, for which the linea r depolarization ratio is approximately 0.15. In computing the Mueller matrix from lidar-polarized backscattering measurements of various co mbinations of transmit/receive polarizations (xy), two steps are emplo yed: (1) a deconvolution process to produce a liar signal p(xy)(r) fro m the polarized lidar measurements by deconvolving the long CO2 laser pulse and the lidar system impulse-response function (i.e., removing t heir smearing effect from the measured lidar signal), and (2) a constr ained slope method to produce an aerosol backscattering coefficient be ta(xy), for each polarization configuration xy, from which the Mueller matrix is computed.