Strong Vertical Velocity Impacts on Cloud Droplet Properties; Implications for Aerosol Indirect Effects
Cloud droplet sizes and behaviors are influenced both by local dynamical effects, such as vertical velocity, and aerosol particles. It is challenging to discern these influences and formulate cloud behavior properly in response to both dynamical and aerosol effects. U.S. Department of Energy scientists at Brookhaven National Laboratory and their collaborators have studied these effects on cloud droplets using data collected in cumulus clouds during the Routine AAF [Atmospheric Radiation Measurement (ARM) Aerial Facility] Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign. Their focus was on the effect of vertical velocity on cloud droplet number concentration and droplet size distribution. This observational study showed that with increasing vertical velocity, the droplet number concentration increases while the size distribution range decreases. These effects happen to be opposite that of enhanced aerosol numbers. Thus, this study is an important step toward understanding and discerning the relative influences of cloud dynamical vigor and aerosol particles on cloud properties.
Lu, C., Y. Liu, S. Niu, and A. M. Vogelmann. 2012). “Observed Impacts of Vertical Velocity on Cloud Microphysics and Implications for Aerosol Indirect Effects,” Geophysical Research Letters 39, L21808. DOI: 10.1029/2012GL053599.