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

oleh: P. Wu, X. Dong, B. Xi

Format: Article
Diterbitkan: Copernicus Publications 2015-09-01

Deskripsi

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 LWP<sub>d</sub>, effective radius <i>r</i><sub>d</sub>, and number concentration <i>N</i><sub>d</sub> for the rain (virga) samples are 4.73 (1.25) g m<sup>−2</sup>, 61.5 (36.4) μm, and 0.38 (0.79) cm<sup>−3</sup>. The seasonal mean LWP<sub>d</sub> 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.