The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study C. Timmreck1 and H.-F. Graf1,2 1Max-Planck Institut für Meteorologie, Hamburg, Germany 2Centre for Atmospheric Science University of Cambridge, UK
Abstract. The chemistry climate model MAECHAM4/ CHEM with
interactive and prognostic volcanic aerosol and ozone was used
to study the initial dispersal and radiative forcing
of a possible Northern Hemisphere mid-latitude super eruption.
Tropospheric climate anomalies are not analysed since sea
surface temperatures are kept fixed. Our experiments show that the global
dispersal of a super eruption located at Yellowstone, Wy.
is strongly dependent on the season of the eruption.
In Northern Hemisphere summer the volcanic cloud is
transported westward and preferentially southward, while in Northern
Hemisphere winter the cloud is transported eastward and more northward
compared to the summer case. Aerosol induced heating leads to a more global
spreading with a pronounced cross equatorial transport. For a summer
eruption aerosol is transported much further to the Southern Hemisphere
than for a winter eruption.
In contrast to Pinatubo case studies, strong cooling
tendencies appear with maximum
peak values of less than −1.6 K/day three months after the
eruption in the upper tropical stratosphere.
This strong cooling effect weakens with decreasing aerosol density
over time and initially prevents the aerosol laden air from further active
All-sky net radiative flux changes of less than −32 W/m2 at the surface
are about a factor of 6
larger than for the Pinatubo eruption. Large positive flux
anomalies of more than 16 W/m2 are found in the first months in the
tropics and sub tropics. These strong forcings call for a fully coupled
ocean/atmosphere/chemistry model to study climate sensitivity
to such a super-eruption.
Citation: Timmreck, C. and Graf, H.-F.: The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study, Atmos. Chem. Phys., 6, 35-49, doi:10.5194/acp-6-35-2006, 2006.