Estimating effective radius and liquid water content from radar and lidar based on the CLARE98 data-set

Abstract

Retrieval methods to estimate the effective radius (re) and the liquid water content (LWC) of stratocumulus clouds from radar and lidar observations are presented here. The retrieval of re is accomplished by combining radar and lidar observations by means of a Z/α − re relation, which is derived from the measurements of in-situ particle probe instruments. The retrieval of LWC, on the other hand, is done solely on the basis of radar observations. However, when plotting a Z-LWC diagram, there was too much scatter, preventing a direct derivation of a Z-LWC relation. It appears that the deviating points in the Z-LWC scatter diagram are mainly caused by the size distributions that have a rather large re. By filtering out these distributions, the scatter in the Z-LWC diagram is significantly reduced and an empirical Z-LWC relation is derived. The estimates of re and LWC using airborne radar and lidar show reasonably good agreements with the profiles measured in-situ. A comparison of the LWC estimated from ground-based radar data, integrated over the cloud height, with the liquid water path provided by a radiometer also shows good z agreement, with a general offset of about 50 g m−2.