Global atmospheric hydrogen chemistry and source-sink budget equilibrium simulation with the EMAC v2.55 model

In this study, we use an earth system model with detailed atmospheric chemistry (EMAC v2.55.2) to undertake simulations of hydrogen (H 2 ) atmospheric dynamics. Extensive global equilibrium simulations were performed with a horizontal resolution of 1.9°. The results of this simulation are compared with observational data from 56 stations in the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory (GML) Carbon Cycle Cooperative Global Air Sampling Network. We introduced H 2 sources and sinks, the latter inclusive of a soil uptake scheme, that accounts for bacterial consumption. The model thus accounts for detailed H 2 and methane (CH 4 ) flux boundary conditions. Results from the EMAC model are accurate and predict the magnitude, amplitude and interhemispheric seasonality of the annual H 2 cycle at most observational stations. Time series comparison of EMAC and observational data produces Pearson correlation coefficients ( r ) in excess of 0.9 at eight remote stations located in polar regions and on high mid-latitude islands. A further 23 stations yielded correlation coefficients between 0.7–0.9, predominantly located in remote marine stations across all latitudes and also in polar regions. The quality of model predictions ( r