AN ASSESSMENT OF THE IMPACT OF VOLCANIC-ERUPTIONS ON THE NORTHERN HEMISPHERES AEROSOL BURDEN DURING THE LAST DECADE

The optical depth data at five wavelengths are derived from sunradiometry data. These are tabulated, and inferences regarding size distribution of the volcanic aerosol are drawn. Under suitable conditions, ground-based sunradiometry can reliably monitor variations in the stratospheric aerosol of less than 0.01 optical depths on time scales of a few weeks or longer. Large (on the order of 0.5 micrometer) particles remained present throughout the decay of the El Chichon aerosol, and there is substantial agreement among mid-latitude data sets collected by several techniques. The available evidence supports the proposition that mid-latitude decay is modulated by annual transport of fresh material from low latitudes, primarily, with some transport from polar latitudes. -from Authors