HR: 1340h
AN: A13A-0874    [Abstracts]
TI: A Study of Small Ions and Aerosol Nucleation in the Troposphere
AU: * Lee, K
EM: anticyclone@tamu.edu
AF: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, United States
AU: Lucas, D D
EM: ddlucas@tamu.edu
AF: Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, United States
AB: Ions represent only a small fraction of the number of molecules in Earth's atmosphere and are most abundant in the upper troposphere and lower stratosphere. However recent model studies and observations of atmospheric aerosols have suggested that ions may play an important role in aerosol nucleation even in the lower troposphere due to enhanced growth and stability of ion clusters resulting from electrostatic interactions. The contribution of ions to aerosol nucleation in the whole atmosphere is not easy to assess because of the complex processes and calculations required. We use a 3D global chemical transport model to calculate ion densities in the atmosphere from the ion balance equation for small ion pairs, which are positive/negative molecular ion clusters. Our model includes modified packages for calculating the production of ions from galactic cosmic rays (GCRs) in troposphere and lower stratosphere and from the radioactive decay of radon-222 (²²²Rn) emitted from the surface. Our model also includes new packages for computing the loss of ions by ion-ion recombination and aerosol-ion attachment processes. In the model simulations, ion densities are very significant in the upper troposphere, where most of the production and loss occurs from GCRs and ion-ion recombination, respectively. The ions in the lower troposphere are produced by a combination of GCRs and ²²²Rn and are mostly balanced by loss through aerosol-ion attachment. In spite of the large aerosol-ion attachment sink, substantial amounts of ions are still present in the lower troposphere. We will assess the contribution of small ions to new aerosols formed in the atmosphere by comparing our model simulations to observations.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 4801 Aerosols (0305, 4906)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting