| An efficient and accurate method for the representation of particle
size distributions in atmospheric models is proposed. The method can
be applied, but is not necessarily restricted, to aerosol mass and
number size distributions. A piecewise log-normal approximation of the
number size distribution within sections of the particle size spectrum
is used. Two of the free parameters of the log-normal
approximation are obtained from the integrated number and mass
concentration in each section. The remaining free parameter is prescribed.
The method is efficient in a sense that only relatively few
calculations are required for applications of the method in
atmospheric models.
Applications of the method in simulations of particle growth by
condensation and simulations with a single column model for
nucleation, condensation, gravitational settling, wet deposition,
and mixing are described. The results are compared to results from
simulations employing single- and double-moment bin methods that are
frequently used in aerosol modelling. According to these comparisons,
the accuracy of the method is noticeably higher than the accuracy of
the other methods. |