AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Studies of the Impacts of Biological Particles on Clouds and Precipitation in Aircraft and Sea Spray Studies
KIMBERLY PRATHER, Paul DeMott, Vicki Grassian, Timothy Bertram, Grant Deane, Matthew Ruppel, Douglas Collins, Andrew Ault, University of California, San Diego
Abstract Number: 612 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Aerosols can modify cloud microphysical properties including droplet size and water phase, and thus can alter precipitation efficiency. In particular, dust aerosols which originate from various deserts around the world, have been shown to serve as effective ice nuclei (IN) and potentially enhance precipitation in mixed-phase clouds. IN are atmospheric particles that catalyze the freezing of supercooled cloud droplets, producing ice crystals that would not form otherwise at warmer, mixed-phase cloud temperatures. Some types of biological aerosols such as bacteria have also been shown to serve as effective IN at relatively warm temperatures, however recent modeling studies have concluded they are of minor importance to global IN concentrations and precipitation processes. In general, the specific sources of the biological particles that serve as ice nuclei are poorly understood and most studies have focused on the ice nucleation activity of terrestrial biological particles. The role of the ocean in producing biological particles which impact clouds is far less understood. This presentation will describe in-situ cloud measurements made in aircraft studies using single particle mass spectrometry to probe the chemical composition of cloud nuclei. This study shows the presence of biological markers in mixed phase clouds and their impact on ice formation and precipitation processes. Results will be presented from laboratory ocean-atmosphere wave flume studies aimed at better understanding marine sources of ice nuclei. These studies use natural seawater and control biological conditions of the seawater to probe how seawater composition impacts the composition and the ice nucleation ability of the resulting sea spray aerosol.