Development of a process-based model to derive methane emissions from natural wetlands for climate studies

Methane is an important greenhouse gas contributing about 22% to the greenhouse effect at present. Methane emissions from natural wetlands, which constitute the biggest methane source at present and the major non-anthropogenic one, depend highly on the climate. In order to investigate the response of methane emissions from natural wetlands to climate variations, a 1-dimensional process-based climate-sensitive model to derive methane emissions from natural wetlands is developed. In the model the processes leading to methane emission are simulated within a 1-dimensional soil column and the three different transport mechanisms diffusion, plant-mediated transport and ebullition are modeled explicitly. The model forcing consists of daily values of the soil temperature, the water table and the Net Primary Productivity. Tests of the methane model using observed data obtained at 15 field stations within 6 wetlands, representing a large variety of environmental conditions, show good agreement. For the use of the 1-dimensional methane model on the global scale, global data sets for all model parameters are generated, derived from the output of a biosphere model and existing data sets of vegetation and soil properties. Furthermore, a simple hydrological model is developed in order to simulate the position of the water table in wetlands. Tests of the 1-dimensional hydrological model, forced by ECMWF re-analyses with observed water table levels from different wetlands, show a good agreement between model results and observations in general. (orig.)Available from TIB Hannover: RR 9(60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman