Cloud, drizzle, and turbulence observations in marine stratocumulus clouds in the Azores

Description

The recent deployment of the AMF at the Azores provided a unique, long-term record (May 2009 to December 2010) of cloud observations in a regime dominated by low-level stratiform clouds. First, a comprehensive cloud classification scheme that utilizes the radar, lidar, and thermodynamic observations is applied to determine the occurrence of different cloud types (e.g., stratus, cumulus, cirrus) and precipitation (e.g., shallow and deep) over the 20-month long data set to identify stratocumulus periods. Around 30 days dominated by stratocumulus clouds were selected for the analysis. A diurnal cycle was obtained for the cloud and drizzle occurrences, as well as their depth. The strength of the drizzle is further studied in conjunction with various other parameters. For instance, the LWP correlates well with the occurrence of drizzle, with the highest values of LWP found in heavier drizzle events. Also, the effects of the stability and adiabaticity of the cloud layer, as well as the presence of decoupling in the sub-cloud layer on the drizzle production and strength are studied. The mass flux from up and downdrafts are assessed from the cloud radar velocity measurements.