Relationship Between Turbulence and Drizzle Onset and Growth in Low-level Continental and Marine Stratiform Clouds Using ARM Observations

Description

Drizzle is ubiquitous in low-level stratiform clouds. Several numerical studies and field experiments have provided supporting evidence of the dominant role of liquid water path in drizzle growth and of an aerosol role in drizzle suppression. However, it remains unclear if and to what extent turbulence influences the production and development of drizzle in low-level stratiform clouds. Here, we use ARM observations to investigate the relationship between turbulence and drizzle. A large dataset of continental and maritime stratocumulus clouds is identified. Using synergy between ground-based aerosol observing systems and active and passive remote-sensing instruments, time series of LWP, cloud condensation nuclei (CCN) number concentration (NCCN), cloud base drizzle rate (RCB), eddy dissipation rate (EDR), and radar Doppler spectrum skewness are derived. This dataset is conditionally sampled with respect to LWP and NCCN, and for each subset within a specific range of LWP and NCCN values, these parameters are used to provide information on drizzle onset, drizzle growth and in-cloud turbulence. The radar Doppler spectrum skewness estimated from the profiling cloud radar is a particularly sensitive parameter in the early detection of drizzle onset. Drizzle growth is evaluated using the drizzle rate estimated at the cloud base. All of these parameters are utilized to investigate the level of turbulence in low stratiform clouds and its relationship to drizzle onset and growth.