Correction scheme for spectral broadening by Rayleigh scattering in differential absorption lidar measurements of water vapor in the troposphere.

An evaluation scheme is given to calculate the water vapor content from data obtained by differential absorption lidar (DIAL), taking into account that the Rayleigh scattered part of the return signal shows considerable spectral broadening in contrast to the Mie scattered part. To correct for errors caused by this effect, information on the aerosol backscattering properties is necessary. Sensitivity analysis performed by model calculations show that it can be retrieved with sufficient accuracy from the off-line signal in the same way as for backscatter lidar. It can be expected that water vapor retrieval will be possible with good accuracy even in the most critical cases, where steep gradients in aerosol backscattering exist in the upper troposphere.