“…Advanced data assimilation allows the propagation of observational information in time and space and from a limited number of observed species to a wide range of chemical components and provides global fields that are physically and chemically consistent and in agreement with individual observations (Sandu and Chai, 2011;Bocquet et al, 2015). Various studies have demonstrated the capability of data assimilation techniques in the analysis of chemical species in the troposphere and stratosphere (e.g., Stajner and Wargan, 2004;Jackson, 2007;Parrington et al, 2009;Kiesewetter et al, 2010;Flemming et al, 2011;Coman et al, 2012;Inness et al, 2013;Emili et al, 2014;Miyazaki et al, 2012aMiyazaki et al, , b, 2014Miyazaki et al, , 2015Miyazaki et al, , 2017Miyazaki and Eskes, 2013;van der A et al, 2015;Gaubert et al, 2016).…”