We present an analysis of volcanic aerosol loading above a northern mid-latitude observing station during the last decade, with particular attention to the decay in the aerosol resulting from the 1982 eruption of El Chichon. 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. Comparison with a number of other data sets is used to establish the validity of our ground-based technique, and to draw inferences regarding stratospheric transport. We also report simulation calculations designed to establish the capabilities and limitations of our measurement and analysis techniques. The main conclusions of the study are as follows. 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; thus inferences regarding stratospheric transport can be drawn from joint analysis of the available data. 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. ¿ American Geophysical Union 1990