Constrained Lidar Ratios for Volcanic Ash and Sulfate Layers in the Stratosphere from CALIOP Version 4.10 Data

Lidar ratios are required to retrieve the extinction profiles in CALIOP algorithm. Unconstrained retrievals: A default lidar ratio is used depending upon the aerosol subtype. Constrained retrievals: The lidar ratio (S) is retrieved from the measured two way transmittance (T2), when clear air is found both above and below the layer for at least 2.5 km (T^2 = /; S = (1-T2)/2γ’), where and are the mean attenuated scattering ratios below and above the layer respectively, and γ’ is the layer integrated attenuated backscatter. A multiple scattering factor of 1 is assumed. In general, constrained lidar ratios are expected to be more representative (but also noisier) than the unconstrained cases, hence accuracy of the unconstrained lidar ratios can be assessed using the constrained ones.