Two-frequency lidar inversion technique.
An analytical technique for inverting lidar returns is proposed and tested on simulated data. The technique requires simultaneous lidar returns at two frequencies and is based on the assumptions that (1) the ratio of backscatter to extinction is independent of position along the lidar line and (2) the ratio of the extinction coefficients at the two frequencies is independent of position along the lidar line. These assumptions are met if molecular scattering can be neglected and the aerosol is composed of the same kind of particle at all points along the lidar line. The simulated data corresponded to a lidar line of 1.0-km length with a uniform aerosol having a total optical depth of 1.0. The quantities determined by the analysis are the total transmittance T, the ratio between the extinction coefficients at the two frequencies k, and the extinction profiles at the two frequencies. The errors in these quantities are critically dependent on the noise level in the data. When 100 shots were averaged to reduce noise, the rms errors in T and k were 1.93 and 1.54%, respectively, and the maximum error in the extinction profile was 6%. An appendix describes possible extensions to include molecular scattering.
Potter
J F
JF