The influence of volcanic stratospheric aerosols on interannual global climate variations
Andsager, Karen Marie
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https://hdl.handle.net/2142/20338
Description
Title
The influence of volcanic stratospheric aerosols on interannual global climate variations
Author(s)
Andsager, Karen Marie
Issue Date
1992
Doctoral Committee Chair(s)
Handler, Paul
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, General
Physics, Atmospheric Science
Language
eng
Abstract
A qualitative physical mechanism has been proposed to explain the forcing of the El Nino/Southern Oscillation (ENSO) by low-latitude volcanic stratospheric aerosols (Handler 1989). This mechanism is based on the normal global annual cycle resulting from the normal annual cycle in the distribution of incoming solar radiation. The presence of a volcanic stratospheric aerosol, which backscatters incoming solar radiation, is hypothesized to trigger the ENSO through an amplification of the normal annual decrease in wind strength and corresponding increase in sea surface temperatures (SST) in the eastern tropical Pacific Ocean. The observational evidence for an association between the record of volcanic eruptions and SST and the Southern Oscillation Index (SOI, Tahiti SLP minus Darwin SLP) over the last 120 years is examined using superposed epoch analysis. Composites using as key dates low-latitude volcanic eruptions suggest that these eruptions are followed by statistically significantly warm sea surface temperatures at least at the 1% level, if not higher, with the greatest warming generally occurring in the first three seasons after the eruption. Satellite data on the distribution of recent volcanic aerosols suggests that an aerosol must only be present over the tropics (about 20$\sp\circ$S to 20$\sp\circ$N) to trigger an ENSO event. For the physical mechanism by which an ENSO event may be triggered by a volcanic stratospheric aerosol, these results and the results of recent computer modeling studies imply the need for a shift away from past emphasis on surface cooling and SLP anomalies and toward consideration of stratospheric warming and changes in energy storage and transport.
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