“…The advent of airborne measurements of OH reactivity (OHR) provides a method to evaluate the total sink of OH across a range of altitudes and a variety of locations and chemical environments (Mao et al, 2009). Previous work compared surface observations of OHR at a single site to the sum of individually calculated OHR components from measurements (Di Carlo, 2004;Yoshino et al, 2006;Sinha et al, 2008Sinha et al, , 2010Mao et al, 2010;Dolgorouky et al, 2012;Hansen et al, 2014;Nakashima et al, 2014;Nölscher et al, 2012Nölscher et al, , 2016Ramasamy et al, 2016;Zannoni et al, 2016Zannoni et al, , 2017 or from simple models (Ren et 10 al., 2006;Lee et al, 2009;Lou et al, 2010;Mogensen et al, 2011;Mao et al, 2012;Edwards et al, 2013;Kaiser et al, 2016;Whalley et al, 2016). Ferracci et al (2018) explored the impact of missing OHR estimated from surface observations on modeled global OH levels.…”