Comparison of the depolarization measurement capability of a lidar ceilometer with cloud particle sensor sondes: A case study of liquid water clouds

Liquid clouds scatter the downward shortwave radiation more than ice clouds, which modulates the surface heat budget. Therefore, a better representation of the cloud phase in climate models, validated by observations, is needed to improve future projections. A ceilometer is a land-based observation system for clouds. This study focused on a new lidar ceilometer with a depolarization function (Vaisala CL61) for distinguishing cloud phases. The data were compared with cloud particle sensor (CPS) sondes at Kitami City in Japan in March 2022. Multiple layers characterized one case with smaller liquid water content at the lower boundary layer, while the other case was a deep liquid cloud layer case with more liquid water content at the cloud bottom. The linear depolarization ratios were well matched in both observing systems. The CL61 detected the signal below the first layer with the amount of liquid water content at 0.4 g m⁻³ (or bottom of the layer with 0.4 g m⁻³).