Tropospheric aerosol ages

Aerosol concentrations and size distributions can be investigated remotely using sun-photometry. Characterization of volcanic aerosol is important in smdies of plume chemistry, atmospheric radiation, and the environmental and health impacts of particle emissions. Watson and Oppenheimer (2000, 2001) used a portable sun-photometer to observe tropospheric aerosol emitted by Mt. Etna. They found distinct aerosol optical signatures for the several plumes emitted from Etna s different summit craters, and apparent coagulation of particles as the plume aged. More recently. Porter et al. (2002) have obtained sun-photometer and pulsed lidar data for the plume from Pu u O o vent on Kilauea, Hawaii, from a moving vehicle in order to build profiles of sulfate concentration. 

By comparison, few of their tropospheric samples, represented by open circles, lie on either model evolution curve, but all lie within an envelope bounded by the batch model curve on the right. These data are consistent with mixing of aerosols with varying ages, and many of the data strongly indicate that mixing has occurred. The data that fall between the two model curves are most constrained and indicate an age between 20 d and 30 d. 

---