Comparison of Mount Pinatubo and El Chichon volcanic events: Lidar observations at 10.6 and 0.69 μm

Abstract

Analyses of a dense set of lidar observations of the volcanic clouds from Mount Pinatubo and El Chichon, primarily over Boulder, Colorado, and at a wavelength of 10.59 μm, reveal notable similarities and differences. The importance of tropopause folding events for purging stratospheric debris into the troposphere is confirmed, as well as the role of gravitational settling to bring debris into the grasp of the folding mechanism. Seasonal influences appear more important than time after eruption in both poleward transport and in purging stratospheric material downward. We discuss the lengthening of the decay process for the Mount Pinatubo clouds by either an equatorial reservoir of debris or by eruptions of Mount Spurr. Simultaneous observations at 0.69 and 10.59 μm help monitor aerosol effective radii versus altitude with good temporal and vertical resolution.

Greenland Ice Sheet melt extent: 1979–1999

“…As such, it is likely that the eruption did affect the melt but not to the extent previously believed. have occurred by 1995 [Hansen et al, 1996], which is consistent with the estimated e-folding time constant of 500 days reported for midlatitudes [Post et al, 1996]. Assuming this to be the case, if we remove the melt years of 1992, 1993, and 1994, the melt trend increases by nearly half to 1.4%/yr.…”

“…roughly half the sulfur dioxide input to the atmosphere[McCormick et al, 1984], its global effects are not so dramatic, but it is possible that the low melt value for 1982 may have been partially influenced by the eruption. The e-folding time constant for E1 Chich6n was estimated at 208 days[Post et al, 1996]; however, so if it did impact the melt, its effects would have been nearly 90% diminished by the following melt season.…”

Atmospheric transparency at Flagstaff, Arizona, 1972–1996: Baselines and Volcanic episodes compared

“…Overall, the two eruption clouds showed somewhat different histories. The extinction from the Pinatubo cloud rose and fell more steeply than that from E1 Chichtn, a distinction noted also by Post et al (1996) authors, using a different instrument, report an extreme peak in extinction on the same date (May 15, 1982) as is shown in our photometry.…”

Global impacts of the 1980s regime shift

“…This fits with measurements that show that much of the aerosol plume from Pinatubo moved rapidly to the south of the equator after the eruption whereas most of the El Chichón plume remained in the Northern Hemisphere (McCormick et al ., ). The seasonal timing of the eruptions (figure 7 in Post et al ., ) and differences in stratospheric wind direction and strength, linked to the quasi‐biennial oscillation (McCormick et al ., ), have also contributed.…”