N2O from the Swiss midlands: regional sources and hot spots

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This project will, for the first time, conduct real-time quasi-continuous measurements of N2O concentrations and site-specific isotopic composition at field and regional scale at a tall tower (Beromünster), located in a rural environment on the Swiss plateau. In a top-down approach, using these measurements, backward Lagrangian particle dispersion modeling (FLEXPART-COSMO) and an inversion system, the source strengths of total N2O and its isotopic signatures in northern Switzerland will be determined. In a complementary bottom-up approach, a state of the art biogeochemical model (LandscapeDNDC) will be extended with a sub-module capable for simulating isotopic signatures of N2O emitted from soils. The model extension will be based on enrichment factors for the relevant processes involved in ecosystem nitrogen cycling. LandscapeDNDC is the most suitable for this approach since besides all other relevant ecosystem N cycling processes also microbial processes such as nitrification and denitrification are already implemented. The model will be supplemented with algorithms reflecting process specific isotopic site preferences of produced and emitted N2O. The extended LandscapDNDC model in combination with detailed geospatial information on soil, vegetation and management will finally be used to identify and assess site, field and regional-scale patterns of soil N2O emissions. The backward Lagrangian transport simulations will provide the necessary link between these bottom-up estimates and the measurements at the tall tower and will allow to check for consistency between biogeochemistry model predictions and observations and to identify weaknesses in our current understanding of the underlying processes.The work is planned for a three-year study based on a PhD (WP 1) and a two year (50 %) post-doc position at Empa (WP 3) advised by the experts of the Laboratory for Air Pollution & Environmental Technology and a three-year PhD position at KIT (WP 2) guided by the specialists at the Institute of Meteorology and Climate Research IMK-IFU, Garmisch-Partenkirchen.