A new algorithm to generate a priori trace gas profiles for the GGG2020 retrieval algorithm

The authors are deeply grateful to Arlyn Andrews from NOAA for providing the approach to generate the stratospheric CO₂, which was adapted and expanded upon for the other stratospheric priors, as well as the tables of stratospheric age of air used throughout this work. The GEOS data used in this study/project have been provided by the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center. Joshua L. Laughner and Paul O. Wennberg acknowledge funding from NASA grant NNX17AE15G. We thank all TCCON partners for carrying out the GGG2014 and GGG2020 retrievals that provided the VSFs for Sect. 5.2. The AirCore campaign in Cyprus received support by the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 856612 and the government of Cyprus and additional support from the Service National d'Observation ICOS-France-Atmosphere coordinated by LSCE. The TCCON Nicosia site has received additional support from the European Union's Horizon 2020 Research and Innovation Programme (EMME-CARE) under grant agreement no. 856612, the government of Cyprus, and the University of Bremen. The CH₄ tower measurements at Park Falls were supported by the DOE Ameriflux Network Management project award to the ChEAS core site cluster (NSF nos. 0845166 and 1822420). NOAA/GML AirCore profiles were supported by NASA (grant no. 80NSSC18K0898). The authors are grateful to Peter Bernath for his leadership of the ACE-FTS project, which was invaluable to this work. The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, is a Canadian-led mission mainly supported by the Canadian Space Agency. A portion of this research was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with NASA (80NM0018D0004). Government sponsorship is also acknowledged.

This research has been supported by the National Aeronautics and Space Administration (grant nos. 80NM0018D0004, NNX17AE15G, and 80NSSC18K0898), the National Science Foundation (grant nos. 0845166 and 1822420), and Horizon 2020 (EMME-CARE, grant no. 856612). Additional support has been provided by the government of Cyprus and the University of Bremen.

JLL created the priors code, carried out the validation, and led the writing of the manuscript. SR developed the code to read GEOS-FPIT meteorology and interpolate to TCCON locations. MK assisted with development of the CO₂ priors. GCT developed the original GGG priors, of which the climatological profiles used for the secondary gases (Sect. 2.4), seasonal cycle parameterization, and tropospheric distance function are retained in this work. POW guided the overall project. Other authors contributed data for validation of the priors. All authors reviewed the manuscript.

At least one of the (co-)authors is a member of the editorial board of Atmospheric Measurement Techniques. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.

This paper was edited by Jian Xu and reviewed by Zhao-Cheng Zeng and one anonymous referee.