1116 Balloonsonde SO2 and O3 Profiles from TICOSONDE in Costa Rica for the Validation of OMI and Sentinel-5 Precursor Retrievals

Wednesday, 10 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Gary A. Morris, St. Edward's Univ., Austin, TX; and H. B. Selkirk, H. Vömel, J. A. Diaz, N. A. Krotkov, C. Li, and J. Joiner

Balloonsonde measurements of ozone use an electrochemical concentration cell (ECC) with the redox reaction between KI and O3 (Komhyr, 1969). SO2 causes an interference reaction with the result that for each one molecule of SO2, the ECC registers one less molecule of O3. When the sonde passes through a plume of SO2, the resulting O3 profile exhibits a sudden decrease and subsequent increase in mixing ratio, distinct from typical O3 fluctuations. Our regular ozonesonde flights as part of the TICOSONDE project in Costa Rica have frequently through emission plumes from nearby Turrialba Volcano. Since 2006 more than 100 Ticosonde ozone profiles have contained the telltale notches of SO2 plume interaction. These notches are frequently several kilometers deep and centered near 3.5 km, the elevation of Turrialba. The deployment of a dual ozonesonde instrument that simultaneously measures O3 and SO2 (Morris et al., 2010) in February 2012 demonstrated that the notches were due to SO2. Starting in 2013 TICOSONDE began regularly flying dual ozonesondes in support of OMI SO2 retrieval validation, with 42 dual ozonesonde flights completed through July 2017. This study reviews the TICOSONDE SO2 column observations from both the dual sonde measurements and the recently developed inferred SO2 approach (Morris et al., 2017) and demonstrates the great value of the coincident observations for validation of OMI, OMPS and Copernicus Sentinel 5 Precursor SO2 retrievals.
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