A Technique for Estimating Liquid Droplet Diameter and Liquid Water Content in Stratocumulus Clouds Using Radar and Lidar Measurements

Abstract

This paper describes a technique for estimating the liquid water content (LWC) and a characteristic particle diameter in stratocumulus clouds using radar and lidar observations. The uncertainty in LWC estimate from radar and lidar measurements is significantly reduced once the characteristic particle diameter is known. The technique is independent of the drop size distribution (DSD). It is applicable for a broad range of W-band reflectivity (Z) between -30 and 0 dBZ and all values of lidar backscatter (β) observations. No partitioning of cloud or drizzle is required based on an arbitrary threshold of Z as in prior studies. A methodology for estimating droplet diameter and LWC was derived from the electromagnetic simulations of radar and lidar observations. In situ stratocumulus cloud and drizzle probe spectra were input to the electromagnetic simulation. The retrieved droplet diameter and LWC were validated using the in situ measurements from the southeastern Pacific. The retrieval methodology was applied to radar and lidar measurements from the northeastern Pacific. Uncertainty in the retrieved droplet diameter and LWC due to the measurement errors in radar and lidar backscatter measurements are 7 % and 14 % respectively. The retrieved LWC was validated using the concurrent G-band radiometer estimates of the liquid water path.