Pinatubo eruption

Another method of probing sulfuric acid aerosols is to heat the sample intake sufficiently to vaporize sulfuric acid-water aerosols but not other particles such as those containing ash minerals the difference between the measured particles with and without intake heating provides a measure of the contribution of sulfuric acid-water. Using this technique, Deshler et al. (1992), for example, have shown that more than 90% of the stratospheric particles above Laramie, Wyoming, after the Mount Pinatubo eruption were composed of sulfuric acid-water mixtures. 

Figure 12.28 shows the particle surface area size distribution before the Mount Pinatubo eruption (Fig. 12.28a), inside the main aerosol layer several months after the eruption (Fig. 12.28b), and almost two years after the eruption (Fig. 12.28c). (See Chapter 9.A.2 for a description of how particle size distributions are normally characterized.) Prior to the eruption, the surface area distribution is unimodal, with typical radii of 0.05-0.09 /xrn and a number concentration of l-20 particles cm 1. In the main stratospheric aerosol layer formed after the eruption, the distribution is bimodal...

Figure 12.29 shows the ratio of the particle surface area at an altitude of 20 km and 45°N latitude to that in 1978-1979 for the period from 1979 to 1995 based on satellite measurements (Solomon et al., 1996). The increases due to volcanic eruptions are evident, particularly the Mount Pinatubo eruption. 

Laboratory studies of the uptake of CIO into sulfuric acid (Martin et al., 1979, 1980), taken in light of a deficit in the inorganic chlorine budget at 17 km after the Mount Pinatubo eruption, led Jaegle et al. (1996) to propose that a heterogeneous reaction of CIO on sulfuric acid aerosols to form perchloric acid, HC104, may also occur. 

FIGURE 12.28 Particle surface area distributions in the stratosphere (a) before Mount Pinatubo eruption, (b) August 20, 1991, over California, and (c) May 7, 1993, over California (adapted from Russell et al. (1996) and Goodman et al. (1994)). 

There are a number of measurements documenting changes in NO and NO. in the stratosphere after the Mount Pinatubo eruption and which have been attributed to the removal of oxides of nitrogen due to reactions on aerosol particles. For example, a decrease in stratospheric NOz after the eruption followed by a return to normal levels has been reported (e.g., see Van Roozendael et al., 1997 and De Maziere et al., 1998). Similarly, NO decreases of up to 70% were reported, as well as increases in gaseous HN03 (much of that produced on the sulfate particles is released to the gas phase) (e.g., see Coffey and Mankin, 1993 Koike et al., 1993, 1994 David et al., 1994 Webster et al., 1994 and Rinsland et al., 1994). 

A similar relationship was observed in Germany. Figure 12.36, for example, shows the deviation of the monthly mean ozone concentration after corrections for seasonal variations, long-term trends, the QBO and vortex effects, and the associated particle surface area concentration from 1991 to 1994 (Ansmann et al., 1996). The increase in the particle surface area due to Mount Pinatubo is clear associated with this increase in aerosol particles are negative monthly mean deviations in ozone that persist until fall 1993, when the surface area approaches the preeruption values. Similarly, the decrease in the total column ozone from 1980-1982 to 1993 observed at Edmonton, Alberta, Canada, and shown at the beginning of this chapter in Fig. 12.1 has been attributed to the effects of the Mount Pinatubo eruption (Kerr et al., 1993). 

Fiocco, G., D. Fua, and G. Visconti, Eds., The Effects of Mt. Pinatubo Eruption on the Atmosphere and Climate, NATO ASI Series Volume 42, Subseries I, Global Environmental Change, Springer-Verlag, Berlin/New York, 1996. 

Hansen, J., A. Lacis, R. Ruedy, and M. Sato, Potential Climate Impact of Mount Pinatubo Eruption, Geophys. Res. Lett., 19, 215-218(1992). 

The effects of the Pinatubo eruption on retrievals of stratospheric aerosol Reff, S and... 

The stratospheric umbrella cloud formed during the Pinatubo eruption attained a vertical thickness... 

Read W. G., Froidevaux L., and Waters J. W. (1993) Microwave limb sounder measurements of stratospheric SO2 from the Mt. Pinatubo eruption. Geophys. Res. Lett. 20, 1299-1302. 

Hansen J., Lacis A., Ruedy R., and Sato M. (1992) Potential chmate impact of Mount Pinatubo eruption. Geophys. Res. Lett. 19, 215-218. 

Hoffmann V, Fehr KT (1996) Micromagnetic, rockmagnetic and minerological studies on dacitic pumice from the Pinatubo eruption (1991, Phillipines) showing self-reversed TRM. Geophys Res Lett... 

M. Blumthaler, W. Ambach (1994). Changes in solar radiation fluxes after the Pinatubo eruption. Tellus, 46B, 76-78. 

Graf, H.-F., I. Kirchner, A. Robock, and I. Schult, Pinatubo eruption winter chmate effects Model versus observations. Climate Dyn 9, 81, 1993. 

The Antarctic ozone hole cannot get very much deeper than it presently is — since virtually all the ozone is now removed each year in those altitudes where PSCs occur. Ozone column minima near 100 DU were observed after the Pinatubo eruption, when the efficiency of heterogeneous chemistry was especially enhanced by very large aerosol amounts over a broad altitude range as noted above. This suggests that the ozone hole could only become deeper in the absence of major... 

---