Publication Date

December 2008


During the month of August 2008, 10 ozonesondes were launched from Hokkaido University in Sapporo, Japan as part of a study to examine regional pollution during the Olympic period. Seven of these soundings included a second instrument with a filter designed to remove SO2 from the intake air stream. SO2 interferes with the normal chemistry of the electrochemical cell (ECC) method for ozone detection, with the net result being that each molecule of SO2 registers as minus one molecule of O3. Thus the unfiltered sonde reports [O3] - [SO2] while the filtered sonde reports [O3]. Laboratory tests prior to launch indicate that the SO2 filter is ~87% effective, while destroying little to no O3. The difference between the filtered and unfiltered readings is ~[SO2]. We demonstrate the effectiveness of this technique in the lower and middle troposphere by examining profiles both with and without SO2 present. Ozone Monitoring Instrument (OMI) SO2 data (Krotkov et al., 2006, 2008) and trajectories from the NASA Goddard Trajectory model (Schoeberl & Sparling, 1995) connect the SO2 detected by our balloon borne instruments over Hokkaido, Japan 21 – 22 August to the plume from the volcanic eruption of Mt. Kasatochi 7 – 9 August.