HR: 16:15h
AN: A44B-02    [Abstracts]
TI: A Parameterization of Ion Induced Nucleation of Sulphuric Acid and Water
AU: * Tripathi, S N
EM: snt@iitk.ac.in
AF: Indian Institute of technology Kanpur, India, India, Kanpur, UP 208016 India
AU: Kumar, S
EM: SanjeevKumar@alumni.iitk.ac.in
AF: Indian Institute of technology Kanpur, India, India, Kanpur, UP 208016 India
AU: Modgil, M S
EM: msingh@iitk.ac.in
AF: Indian Institute of technology Kanpur, India, India, Kanpur, UP 208016 India
AU: Lovejoy, E
EM: Edward.R.Lovejoy@noaa.gov
AF: Aeronomy Laboratory, NOAA, Boulder, Colorado, CO 80305 United States
AB: Aerosol is ubiquitous in Earth's atmosphere, and affects health, visibility, atmospheric chemistry, and climate. Particle nucleation that can not be explained with classical binary nucleation theory has been observed in the lower and middle troposphere. Ion induced nucleation (IIN), involving the negative ion H$_{2}$SO$_{4}$/H$_{2}$O mechanism, has been shown to be an effective source of new particles in atmosphere. This paper describes a 5 dimensional parameterization of IIN that covers the complete range of conditions relevant to the lower atmosphere, based on the kinetic aerosol model SAWNUC (Sulphuric Acid and Water Nucleation). SAWNUC is a kinetic model that is based on experimental thermodynamics of small ion clusters of H$_{2}$SO$_{4}$ and H$_{2}$O. A nested Do Loop version of SAWNUC was created to cover the complete range of input variables required for parameterization. Six output variables generated from SAWNUC were (1) particle nucleation rate (cm$^{-3}$ s$^{-1}$), (2) H$_{2}$SO$_{4}$ nucleation rate (cm$^{-3}$ s$^{-1}$), (3) number of H$_{2}$SO$_{4}$ in average nucleating cluster, (4) number of H$_{2}$O in average nucleating cluster, (5) radius (nm) of average nucleating cluster, and (6) first order loss of H$_{2}$SO$_{4}$ to particles (s$^{-1}$). The parameterized dataset consisted of 76800 points. The input parameters for parameterization are (1) Temperature-T (190-300 K), (2) Relative Humidity-RH (0.05-0.95), (3) number concentration of H$_{2}$SO$_{4}$ (10$^{5}$-10$^{8}$ cm$^{-3}$), (4) First order loss of H$_{2}$SO$_{4}$ to particles (0.00009-0.0245 s$^{-1}$), and (5) Ion Source rate (1-50 ion pairs cm$^{-3}$ s$^{-1}$). The parameterization generally reproduces the modeled nucleation rate to within a factor of two over the whole range of conditions, except when the nucleation rate is very low ($<$ 10$^{-6}$ cm$^{-3}$ s$^{-1}$), which corresponds to less than 0.1 particle day$^{-1}$ cm$^{-3}$. If the ratio of model value to the parameterized value falls between 0.5 and 2.0, it is treated as efficient output of parameterization. Efficiencies exceeding 85 percent are obtained. The standard deviation of the ratio of model value to the parameterization value is used as a measure of the accuracy of the parameterization. For the present IIN parameterization, the standard deviation falls between 0.2 and 0.5. This parameterization speeds up IIN calculations by a factor of $\sim$10$^{6}$, as compared to the original SAWNUC model.
UR: http://home.iitk.ac.in/~snt/param
DE: 3309 Climatology (1620)
DE: 1704 Atmospheric sciences
DE: 1610 Atmosphere (0315, 0325)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting