Springtime aerosol layers in the free troposphere over Australia: Mildura Aerosol Tropospheric Experiment (MATE 98)

A field campaign focused primarily on free tropospheric aerosol measurement s over Mildura, Australia, at 34 degrees S (Mildura Aerosol Tropospheric Ex periment (MATE 98)) was conducted in the austral spring of 1998 to test for the current presence of a seasonal aerosol layering activity observed ill the 1970s and to obtain additional characteristics that would lead to a bet ter understanding of the phenomenon. Ground-based lidar as well as balloon- borne optical particle counters and backscattersondes with ozone sensors we re employed. The results indicate that large horizontal scale layers are pr esent and show that their structure is highly correlated with excess ozone. Particle concentrations in the layers were sufficient to measurably affect aerosol optical depth. The probable source is distant biomass burning regi ons, but a detailed understanding of associated smoke transport and evoluti on as observed over Mildura is incomplete.