| 10 Feb 2026
Interactive Simulation of Methane and Hydrogen Soil Deposition in ECHAM5/MESSy Atmospheric Chemistry Model (EMAC) v2.55 with the new Submodel BIODEP (v1.0)
Abstract. Methane (CH4) and hydrogen (H2) play critical roles in atmospheric chemistry and climate processes. CH4 is a powerful greenhouse gas, whereas H2, although not a greenhouse gas itself, indirectly affects radiative forcing by modifying the atmosphere's oxidative capacity and therefore the concentrations of CH4, ozone (O3) and stratospheric water vapor. Hydrogen is predominantly removed through microbial uptake in soils, while approximately 6 % of CH4 is taken up by soils, a factor that contributes significantly to its overall atmospheric budget. Soil uptake depends on various soil characteristics, including type, temperature, moisture, and for CH4, nitrogen deposition. Accurately representing these influences requires a detailed understanding of both atmospheric conditions and land surface and hydrological properties. However, many Earth system models currently use fixed soil deposition rates for H2 and CH4, without accounting for variations in soil properties. We present BIODEP, a new biogenic deposition submodel that has been integrated into the ECHAM/MESSy Atmospheric Chemistry model (EMAC). BIODEP dynamically simulates the uptake of CH4 and H2 by soil, based on local meteorological and soil conditions. With BIODEP, the soil sinks of CH4 and H2 are updated online based on the meteorological conditions, atmospheric composition, and land surface properties provided by the EMAC model. The EMAC model is coupled to the JSBACH land surface and vegetation model. This allows for a consistent and interactive treatment of soil sinks within the atmospheric chemistry model. Modeled global mean soil uptakes of 62.7 ± 11.7 Tg yr−1 for H2 and 30.2 ± 4.8 Tg yr−1 for CH4 are consistent with previous studies, and the resulting atmospheric mixing ratios show good agreement with observations from the NOAA GML Carbon Cycle Cooperative Global Air Sampling Network, evaluated over the period 2009–2019. In addition, comparison with column-averaged CH4 (XCH4) observations from the Greenhouse Gases Observing Satellite (GOSAT) demonstrates that EMAC reproduces the global and zonal-scale methane distribution with small mean biases, providing independent support for the accuracy of the simulated soil methane sink. This development makes EMAC a state-of-the-art model to interactively simulate atmospheric chemistry, including both the soil sinks of CH4 and H2. This enables more consistent simulation of trace gas budgets and an improved assessment of the feedbacks between land surface processes, atmospheric composition, and future climate and emission scenarios.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Geoscientific Model Development.
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