The links between multiple-scattering induced depolarization and cloud microphysical properties (e.g. cloud particle number density, effective radius, water content) have long been recognised. Previous efforts to use depolarization information in a quantitative manner to retrieve cloud microphysical cloud properties have also been undertaken but with limited scope and, arguably, success. In this work we present a retrieval procedure applicable to liquid stratus clouds with (quasi-)linear LWC profiles and (quasi-)constant number density profiles in the cloud-base region. This set of assumptions allows us to employ a fast and robust inversion procedure based on a lookup-table approach applied to extensive lidar Monte-Carlo multiple-scattering calculations. An example validation case is presented where the results of the inversion procedure are compared with simultaneous cloud radar observations. In non-drizzling conditions it was found, in general, that the lidar-only inversion results can be used to predict the radar reflectivity within the radar calibration uncertainty (2-3 dBZ). Results of a comparison between ground-based aerosol number concentration and lidar-derived cloud base number considerations are also presented. The observed relationship between the two quantities is seen to be consistent with the results of previous studies based on aircraft-based in situ measurements.@en

The microphysical processes in fog are examined based on an analysis of four fog events captured by the in-situ and remote sensing synergy at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the western part of the Netherlands. A 35 GHz cloud radar at CESAR has been used in "fog mode" for the first time in the campaign. In this paper, the microphysical parameterization of fog is first introduced as the basis for analyzing the microphysical processes in the lifecycle of fog. The general microphysical characteristics of the four fog events are studied and key microphysical parameters (droplet number concentration, liquid water content, mean radius, and spectral standard deviation) related to fog are found lower than those in other sites due to the low aerosol concentration at Cabauw. The dominant processes in fog are investigated from the relationships among the key microphysical parameters. The positive correlations of each two parameters in lifecycle stages of a stratus-fog case suggest the dominant scheme in fog is droplet activation with subsequent hygroscopic growth and/or droplet evaporation, which is also supported by the combined observations of visibility and radar reflectivity. The shape of fog drop size distribution regularly broadens and then narrows in the whole lifecycle. However, other mechanisms could exist, although not dominating. Collision-coalescence is a significant factor for the continued growth of big fog droplets when they have reached certain sizes in the mature stage. In the datasets, the collision-coalescence process could be distinguished from the unusual negative correlations among the key microphysical parameters in the lifecycle of another stratus-fog case, and the temporal evolutions of droplet number concentration, mean radius, spectra width, visibility and radar reflectivity show the evidence of it.@en