Inverse modeling of aerosol dynamics: Condensational growth

Abstract

The feasibility of inverse modeling a multicomponent, size-resolved aerosol evolving by condensation/evaporation is investigated. The adjoint method is applied to the multicomponent aerosol dynamic equation in a box model (zero-dimensional) framework. Both continuous and discrete formulations of the model (the forward equation) and the adjoint are considered. A test example is studied in which the initial aerosol size composition distribution and the pure component vapor concentrations (i.e., vapor pressures) are estimated on the basis of measurements of all species, or a subset of the species, and the entire size distribution, or a portion of the size distribution. It is found that the adjoint method can successfully retrieve the initial size distribution and the pure component vapor concentrations even when only a subset of the species or a portion of the size distribution is observed, although this success is shown to depend upon the form of the initial estimates, the nature of the observations, and the length of the assimilation period. The results presented here provide a basis for the inverse modeling of aerosols in three-dimensional atmospheric chemical transport models.

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