The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study

[摘要] The chemistry climate model MAECHAM4/ CHEM withinteractive and prognostic volcanic aerosol and ozone was usedto study the initial dispersal and radiativeforcingof a possible Northern Hemisphere mid-latitude super eruption.Tropospheric climate anomalies are not analysed since seasurface temperatures are kept fixed. Our experiments show that the globaldispersal of a super eruption located at Yellowstone, Wy.is strongly dependent on the season of the eruption.In Northern Hemisphere summer the volcanic cloud istransported westward and preferentially southward, while in NorthernHemisphere winter the cloud is transported eastward and more northwardcompared to the summer case. Aerosol induced heating leads to a more globalspreading with a pronounced cross equatorial transport. For a summereruption aerosol is transported much further to the Southern Hemispherethan for a winter eruption. In contrast to Pinatubo case studies, strong coolingtendencies appear with maximumpeak values of less than −1.6 K/day three months after theeruption in the upper tropical stratosphere.This strong cooling effect weakens with decreasing aerosol densityover time and initially prevents the aerosol laden air from further activerising. All-sky net radiative flux changes of less than −32 W/m² at the surfaceareabout a factor of 6larger than for the Pinatubo eruption. Large positive fluxanomalies of more than 16 W/m² are found in the first months in thetropics and sub tropics. These strong forcings call for a fully coupledocean/atmosphere/chemistry model to study climate sensitivityto such a super-eruption.

[学科分类] 大气科学