Lidar Inversion Research Articles

Down looking lidar inversion constrained by ocean reflection and forward scatter of laser light

The laser aureole at 1.06 microm resulting from the redirection of light by sea surface reflection and forward scatter through maritime boundary layer aerosols to a sensor high above the ocean surface is modeled for profiles with typical North Atlantic aerosol size distributions. The magnitude of this laser aureole is highly correlated with the optical depth for these profiles. This optical depth, estimated from the laser aureole, is used to adjust the power of the extinction-backscatter relationship in a Bernoulli-Riccati lidar inversion. Using a lognormal marine aerosol model, 150 profiles of aerosol size distributions are selected by their probability of occurrence in the North Atlantic boundary layer. For these profiles, the lidar inversion using the estimated optical depth predicted the surface extinction 5 times better than the lidar inversions using a climatological backscatter-extinction relationship.

Lidar inversion with variable backscatter/extinction ratios

The conventional approach to solving the single-scattering lidar equation makes use of the assumption of a power law relation between backscatter and extinction with a fixed exponent and constant of proportionality. An alternative formulation is given herein which assumes the proportionality factor in the power law relationship is itself a function of range or extinction. The resulting lidar equation is solvable as before, and examples are given to show how even an approximate description of deviations from the power law form can yield an improved inversion solution for the extinction. A further generalization is given which includes the effects of a background of Rayleigh scatterers.

Sensitivity of a lidar inversion algorithm to parameters relating atmospheric backscatter and extinction

A solution of the single-scattering lidar equation requires a relationship between the coefficients of backscatter beta(r) and extinction sigma(r) to be of the form beta(r) = C2sigma(r)k, where C2 and k are parameters independent of range r. The sensitivity of a particular lidar inversion algorithm to uncertainties in C2 and k is investigated using a measured lidar return which indicated the atmosphere to be essentially horizontally homogeneous during a reduced visibility condition. Starting with the measured power returned as a function of range, extinction coefficients and average visibilities are calculated using the inversion algorithm for different values of C2 and k and compared with those inferred from the lidar return using the slope method. The calculated extinction coefficients (and visibilities) were found to be extremely sensitive to uncertainties in C2. This questions the usefulness of the lidar inversion algorithm for aerosol extinction applications when the air mass characteristics change along the measurement path.

Significance of the boundary value term in the Klett lidar inversion formula

Significance of the boundary value term in the Klett lidar inversion formula