HR: 0800h
AN: A41D-0738    [Abstracts]
TI: Parameterization of the effect of sub-grid scale aerosol dynamics on aerosol number emission rates
AU: Theodoritsi, G
EM: gtheodorits@upnet.gr
AF: Department of Chemical Engineering, University of Patras, University of Patras, Patras, 265 00, Greece
AU: * Pierce, J R
EM: jrpierce@andrew.cmu.edu
AF: Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, United States
AU: Adams, P J
EM: petera@andrew.cmu.edu
AF: Department of Civil and Environmental Engineering, Department of Engineering and Public Policy, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, United States
AU: Pandis, S N
EM: spyros@andrew.cmu.edu
AF: Department of Chemical Engineering, University of Patras, University of Patras, Patras, 265 00, Greece
AU: Pandis, S N
EM: spyros@andrew.cmu.edu
AF: Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, United States
AB: One of the major challenges in simulating the aerosol number concentration and number size distribution in the atmosphere is the description of aerosol dynamics near sources of primary particles. These emission "hot spots" may be metropolitan areas in global models or large point sources in global and regional models. Most models currently simulate the average particle number concentration in the grid cell, spreading the effect of the hot spot unrealistically across the cell. However, coagulation is a nonlinear process and numerical "dilution" of the emitted particles in the full grid cell introduces potentially significant bias in the model results. Unfortunately, simulation of the rapid dilution of particles as they disperse away from their source together with their coagulation, removal, and growth or evaporation is prohibitively expensive for regional and global chemical transport models. In this study, we develop a method for the parameterization of the sub-grid scale aerosol dynamics. This method calculates the probability that a given particle emitted inside the grid cell will survive and be available for transfer outside the cell. This survival probability is calculated theoretically as a function of the emitted particle size, the pre-existing aerosol size distribution in the grid cell, the meteorological conditions, and the size of the grid cell. The net number of particles effectively emitted to the grid cell can then be calculated by multiplying the size dependent emission rate in the inventory with this survival probability. The method simultaneously conserves mass by adding the mass of particles lost by coagulation to the larger particle sizes. The approach is grid-size independent and can be used in models of all scales. Its results compare favorably with the predictions of a detailed one-dimensional aerosol dynamics and chemistry model under a variety of atmospheric conditions.
DE: 1610 Atmosphere (0315, 0325)
DE: 3311 Clouds and aerosols
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting