Simulations of the Impact of Inhomogeneous Water Columns on the Temporal Stretching of Laser Bathymeter Pulses

This report documents the results of a sensitivity study to determine the potential impact of optical inhomogeneities in the water column in inducing errors in bias correctors for pulse stretching effects for a bathymetric lidar when the correctors are derived on the assumption of a homogeneous column. The existing Monte Carlo radiative transfer simulation program was modified to allow convenient simultaneous estimation of the impulse response functions for a number of different vertical distributions of scatterers and absorbers Outputs were obtained for vertical optical depths up to 16, six different values of single-scatter albedo, and two nadir angles in air -- namely, 0 and 25 degrees.A digital convolution was performed over an anticipated source pulse profile to obtain the ’’environmental response functions” (ERF’s), and biases were estimated by applying the same linear fractional threshold to both the source pulse and the ERF and comparing the results to the actual simulated depths. The results for the inhomogeneities we considered indicate that the use of correctors derived for the homogeneous case is likely to result in errors of less than 10 cm. 1981 OTES (Ocean Technology and Engineering Services) Library Public Domain 1930