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Title:
Comparing the Climatic Impact from Low Latitude versus High Latitude Volcanic Eruptions
Authors:
Oman, L.; Robock, A.; Stenchikov, G.
Affiliation:
AA(Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States; ), AB(Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States; ), AC(Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 United States; )
Publication:
American Geophysical Union, Fall Meeting 2003, abstract #A41D-0725
Publication Date:
12/2003
Origin:
AGU
AGU Keywords:
0305 Aerosols and particles (0345, 4801), 0370 Volcanic effects (8409), 3334 Middle atmosphere dynamics (0341, 0342), 3360 Remote sensing, 8409 Atmospheric effects (0370)
Bibliographic Code:
2003AGUFM.A41D0725O

Abstract

Explosive volcanic eruptions cause large amounts of SO2 to be injected into the stratosphere. The SO2 is converted to sulfate aerosols over time, which cause a significant radiative perturbation to the climate system. The resulting climate response should depend strongly on the latitude of the eruption. We examine these differences using observations and a new version (model E) of the Goddard Institute for Space Studies (GISS) general circulation model (GCM), comparing the temperature and circulation responses of the low latitude Mount Pinatubo (15° N) eruption on June 15, 1991, with those from the high latitude Katmai (58° N) eruption, which occurred on June 6, 1912. For the Pinatubo eruption, we constructed an aerosol data set utilizing SAGE II observations as well as other remote sensing instruments. Our new simulations with the GISS GCM, as well as previous simulations with the GFDL SKYHI and Max Planck ECHAM 4 GCMs, have shown that volcanic aerosol heating of the lower stratosphere from thermal IR and solar near-IR radiation causes changes in the circulation of the stratosphere by increasing the meridional temperature gradient, resulting in a stronger polar vortex. They also showed that reduced solar radiation in the troposphere caused cooler temperatures in the subtropics, which decreased the meridional temperature gradient. This caused a reduction in the amplitude of planetary waves and allowed further strengthening of the polar vortex. The resulting forced positive phase of the Arctic Oscillation caused changes in tropospheric circulation. For Katmai, aerosol data were derived primarily from pyrheliometric observations, and show that while the optical depth was similar in magnitude to the Mount Pinatubo eruption, it was confined to the Northern Hemisphere generally north of 30° N. Modeling of this eruption showed mainly mid- and high latitude cooling over continental areas for approximately 1 year following the eruption. This caused an increase in the meridional temperature gradient. Simulations also indicate a warmer and weaker stratospheric polar vortex in the first winter following the eruption.
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