Atmospheric Chemistry and Physics Discussions The Australian bush fires of February 2009: MIPAS observations and GEM-AQ model results

Abstract

On 7 February 2009, and the following days Southeast Australia was devastated by large bush fires, which burned an area of about 3000 km 2 . This event was extraordinary, because a large number of combustion products was transported into the uppermost troposphere and lower stratosphere within a few days. Various biomass burning prod-5 ucts released by the fire were observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. We track the plume using MIPAS C 2 H 2 , HCN and HCOOH single-scan measurements on a day-to-day basis. The measurements are compared with a high-resolution model run of the Global Envi-ronmental Multiscale-Air Quality (GEM-AQ) model. Generally there is very good agree-10 ment between the spatial distribution of measured and modelled pollutants during the first two weeks after the outbreak of the fire even over intercontinental distances. Both MIPAS and GEM-AQ show a fast south-eastward transport of the pollutants to New Zealand within one day. During the following 3–4 days the plume was located north and eastward of New Zealand and centered at altitudes of 15 to 18 km. Thereafter its 15 eastern part was transported eastward at altitudes of 15–16 km, followed by westward transport of its western part at somewhat higher altitudes. On 17 February the eastern part had reached Southern South America and on 20 February the South African west coast. On the latter day a second relic of the plume was observed moving eastward above the Southern Pacific, whereas the westward transported pollutants were located 20 above Australia at altitudes of 18–20 km. First evidence for entry of the pollutants into the stratosphere was found in MIPAS data of 11 February, followed by larger amounts on 17 February and the days thereafter. Between 20 February and the first week of March the stratospheric pollutants above Australia were transported further westward over the Indian Ocean towards Southern Africa.