Articles | Volume 8, issue 9
Research article
03 Sep 2015
Research article |  | 03 Sep 2015

Marine boundary layer drizzle properties and their impact on cloud property retrieval

P. Wu, X. Dong, and B. Xi

Abstract. In this study, we retrieve and document drizzle properties, and investigate the impact of drizzle on cloud property retrieval in Dong et al. (2014a) from ground-based measurements at the ARM Azores facility from June 2009 to December 2010. For the selected cloud and drizzle samples, the drizzle occurrence is 42.6 %, with a maximum of 55.8 % in winter and a minimum of 35.6 % in summer. The annual means of drizzle liquid water path LWPd, effective radius rd, and number concentration Nd for the rain (virga) samples are 4.73 (1.25) g m−2, 61.5 (36.4) μm, and 0.38 (0.79) cm−3. The seasonal mean LWPd values are less than 3 % of the LWP values retrieved by the microwave radiometer (MWR). The annual mean differences in cloud-droplet effective radius with and without drizzle are 0.75 and 2.35 %, respectively, for the virga and rain samples. Therefore, we conclude that the impact of drizzle below the cloud base on cloud property retrieval is insignificant for a solar-transmission-based method, but significant for any retrievals using radar reflectivity.

Short summary
How does drizzle underneath marine boundary layer (MBL) clouds affect cloud property retrievals? How much liquid water is depleted by virga and rain? To our knowledge, no previous studies have quantitatively estimated the impact of drizzle on cloud property retrievals. Cloud parameterization and radiative transfer modeling researchers will be interested since we give quantitative estimations of drizzle and cloud effective radius, no. concentration, liquid water content, and optical thickness.