The effect of plume intermittency upon differential absorption Lidar measurements

The effect of plume intermittency upon a shot averaged differential absorption Lidar (DIAL) system has been modelled using datasets obtained with a rapid-scanning backscatter Lidar. It is shown that shot averaging within the non-linear DIAL analysis may lead to the analysed plume cross-section differing significantly from the true mean. If the plume is optically dense at the resonant wavelength, intermittency may lead to target gas concentrations being substantially underestimated. Conversely, if the aerosol providing the backscatter signal is strongly correlated with the target gas, then the shape of the cross-section will be greatly distorted but, unless the plume is optically dense, the overall flux will be approximately correct.