Evolution of Australian Bushfire 2009 Plume in the UTLS region investigated using the OSIRIS limb profiles

Major Bushfires in south-eastern Victoria, Australia, produced a smoke plume on 7 February 2009 that was injected into the troposphere, vertically advecting to the lower stratosphere. In order to investigate both horizontal and vertical evolution of this smoke plume, global maps of limb-scattered radiances were produced. These maps were plotted using observations at various altitudes from the OSIRIS (Optical Spectrograph and Infrared Imager System) instrument onboard the Odin satellite. The OSIRIS Level 1 radiances, taken at a 2 km vertical step, were averaged for OSIRIS CCD pixels 1205-1220 (at around 800 nm), and were used to monitor the position and intensity of the aerosol smoke plume as it was transported vertically and horizontally. The results of this analysis suggest that the plume moved eastward from its initial source to New Zealand and reached an altitude of 14 km by 11 February. The plume remained fairly stationary until 13 February, during which time other large radiance perturbations over Indonesia, northern Australia and the Tasman Sea were observed, often extending from 12 to 18 km. On 14 February the bushfire plume was observed at about 19 km and remained over the Tasman Sea until 19 February, gradually moving upwards to 21 km. Subsequently the plume was observed to be moving westward within the 19-21 altitude range over the Indian Ocean, reaching Madagascar at the end of February. It remained stationary over Madagascar until late February and then moved across southern Africa. At that time another convection event was observed by OSIRIS over southern Africa from the beginning of March which had a vertical distribution from ~14-18 km, which the bushfire plume was seen to pass through. This resulted in radiance perturbations over southern Africa for over a week. The plume arrived at South America on 9 March and was observed at 20-22 km altitude. Over the next few weeks it remained over the South American region. Throughout this period the aerosol plume was mostly confined at extra-tropical latitudes (0-30°S) in the Southern Hemisphere, with a gradual loss in radiance intensity, indicating a slow decrease in aerosol density within the plume over the 2 month period. At the end of March, the plume became partially dispersed over the Eastern Pacific region with radiance perturbations observed at altitudes of 20-24 km. The background radiance intensity is calculated in order to obtain a more accurate intensity level of the aerosol plume itself. This is performed by averaging global radiances within a 10 degree latitude band centered on the plume, excluding an area of 10 x 10 degrees around the plume. Subtracting background radiance gives net plume radiance intensity, which is a combination of single and multiple scattering from aerosol particles within the plume. This is determined for each day from 11 February until the end of October. A correlation between the radiance maxima and O3 and NO2 number density, simultaneously measured by OSIRIS, is analysed in order to investigate any effect of this pyroconvection event on atmospheric chemistry over time.