TRANSPORT OF THE PINATUBO VOLCANIC AEROSOL TO A NORTHERN MIDLATITUDE SITE

A 2-year time series of high resolution lidar backscatter profiles at 0.532 mu m, taken NOAA Fritz Peak Observatory (39.9 degrees N, 105.3 d egrees W) is analyzed to investigate the evolution of the stratospheri c aerosol following the eruption of Mount Pinatubo in June, 1991. Aero sol from the eruption first appeared as transient layers just above th e tropopause in late summer and early fall of 1991. This was followed by a rapid increase in aerosol centered near 21 km, with an exponentia l risetime of similar to 22 days. The maximum in late December 1991 wa s followed by a slow decline, punctuated by seasonal increases below 1 8 km and with an exponential decay timescale of similar to 300 days ne ar 20 km. Aerosol backscatter is converted to mass and a principal com ponent analysis (PCA) is performed to explore the statistical properti es of aerosol variability. More than 80% of the variability in aerosol mass is described by only three components, corresponding to variatio ns in the layers 17-22 km (PC1, 44%), below 17 km (PC2, 27%), and abov e 22 km (PC3, 9%). Since most of the temporal variations occur indepen dently in these three layers, this work provides further insight into the nature of stratospheric transport from the tropics to midlatitudes .