More than a decade of TICOSONDE directly measured and inferred profiles of SO2

The TICOSONDE project began in 2005 in San Jose, Costa Rica and continues to this day. A SHADOZ station in the northern hemisphere tropics, TICOSONDE has supported more than 600 ozonesonde flights on a nearly weekly schedule. Interference from SO₂ in the cathode cell reactions of the electrochemical concentration cell (ECC) instrument used to measure ozone led to the frequent appearance of notches in the data record. Several active volcanoes near San Jose, most notably Turrialba, are the sources of the SO₂. Since 2012, we have made direct measurements of SO₂ profiles using the dual-sonde technique of Morris et al. (2010). Recently, we have inferred SO₂ profiles from the notches in the historic record prior to the deployment of the dual-sonde approach. Most recently, we deployed a new direct measurement approach in March 2018. We review lessons learned along the way and insights from each of the techniques as well as from the long time series of SO₂ profiles.