Abstract
The decay rate of the non-molecular radar cross section βM of the post-Fuego stratospheric aerosols observed by lidar was much smaller than that deduced by using the wellknown Gudiksen's 2-dimensional atmospheric model. The discrepancy can be explained by a kinetic aerosol model including condensation growth of the aerosols. A closed incompressible air parcel model is proposed to discuss chemical and physical processes of the volcanic substances separately from the global transport.
The kinetic aerosol model is used to examine temporal variations of aerosol size distributions in a volcanic air parcel. Sulfur cycle in the model is described by three equations. The first one expresses conversion of SO2 to H2SO4 vapor of which concentration is described by the second one. The third one describes the time evolution of the size distribution in terms of condensation and coagulation processes. Assuming two initial size distributions, Haze H and log normal, these equations are solved numerically for the aerosols with size range 0.01μm<r<0.4μm.
In the case of the Haze H initial size distribution the discrepancy can be explained if we take appropriate values of conversion rate and initial concentration of SO2. On the contrary, in the case of log normal, the observed decay rate can not be explained by the kinetic aerosol model in this paper.
