AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Cloud-Aerosol Interactions in Deep-Convective Systems: Particle Mass, Number, and Composition Effects
BENJAMIN MURPHY, Ilona Riipinen, Annica Ekman, Stockholm University
Abstract Number: 208 Working Group: Aerosols, Clouds, and Climate
Abstract The number, size, and composition of an aerosol population entrained into a cloud system can affect cloud physical features (e.g. updraft velocity or precipitation rate) while cloud properties can affect features of the aerosol population (e.g. through wet scavenging or aqueous-phase chemistry). In order to invesitgate these complicated feedbacks, we present a new three-dimensional cloud-resolving model, CRM-ORG, which accounts for the processing of inorganic and organic aerosol components in a fully-coupled, dynamic simulation. We apply this model to a case study of a deep convective cloud under clean conditions above the tropical Amazon.
Incorporating the Volatility Basis Set approach of Donahue et al. (2006) into the 3-D cloud resolving host model described by Ekman et al. (2006), the CRM-ORG model relies on a suite of lumped species to describe the oxidation products of biogenic VOCs. The mass transfer of these species to/from particles and cloud drops is treated dynamically along with aqueous-phase chemical reactions relevant to the production of low-volatility organic compounds that partition significantly to the particulate phase after cloud drop evaporation. The model accounts for particle nucleation and growth due to condensation of organic vapors. This work also probes the sensitivity of the results to both the nucleation mechanism formulation and condensable organic vapor volaitlity.
In order to gain a general understanding of cloud-aerosol interactions, we report the net effect of cloud processing on aerosol mass and number throughout the column. Of particular focus is the generation of new particles in the relatively clean background environment of the upper troposphere where substantial amounts of trace gases and particles are injected within the cloud outflow.
Ekman, A.M.L., Wang, C., Ström, J. and Krejci, R. (2006) J. Atmos. Sci. 63, 682-696.
Donahue, N.M., Robinson, A.L., Stanier, C.O. and Pandis, S.N. (2006) Environ. Sci. Technol. 40, 2635-2643.