DOI: 10.26050/wdcc/meramo_exp2
title: HBM-ERGOM western Baltic Sea simulations with tagging of medium resolution atmospheric nitrogen deposition by CMAQ

description: Project: HBM-ERGOM western Baltic Sea simulations with tagging of atmospheric nitrogen deposition within the MeRamo project - The MeRamo project (Unterstützung der mit der Umsetzung der EU Meeresstrategie-Rahmenrichtlinie befassten Behörden mittels eines assimilativen Ökosystems) was funded within the German national budget for the EU Copernicus Programme (BMVI Grand 50EW1601). The aim of the project was to link EU Copernicus services -- namely Sentinel remote sensing data -- with a marine biogeochemical model system (HBM-ERGOM). Additionally, the contribution of nitrogen from atmospheric deposition to the marine nitrogen budget was to assess. 

Two scientific questions were derived for the second project focus:

- What contribution does atmospheric nitrogen deposition in total and atmospheric deposition of nitrogen from shipping and agricultural activities have to the nitrogen budget in the marine surface layer of the western Baltic Sea?

- What is the impact of the spatial resolution of nitrogen deposition data on the biogeochemical model predictions in highly structured coastal areas in the western Baltic Sea region?

To deal with these questions, the model system HBM-ERGOM was extended by a nutrient tagging/tracing approach and model simulations with tagged atmospheric nitrogen compounds were performed at the North-German Supercomputing Alliance (HLRN, project id: mvk00054, zulassung.hlrn.de/kurzbeschreibungen/mvk00054.pdf). Three different nitrogen deposition data sets were used for the model simulations. Two spatial highly resolved deposition data sets were provided by the EU BONUS Project SHEBA (Karl et al., 2019, doi:10.5194/acp-2018-1317) and one deposition data set was provided by the Norwegian Meteorological Institut (MetNo, 2016) for the European Evaluation and Modelling Programme (EMEP). The year 2012 was simulated. The North Sea and Baltic Sea were covered by the model domain but only results for the western Baltic Sea are provided here. The latter data were presented in Neumann et al. (2018, doi:10.5194/os-2018-71).
Summary: A marine physical biogeochemical model simulation was performed for the year 2012 covering the North Sea and Baltic Sea. Only data for the western Baltic Sea are provided here. The model output has been validated in Neumann et al. (2018a, doi: 10.5194/os-2018-71). The work was funded by the German Federal Ministry of Transport and Digital Infrastructure (BMVI, FKZ 50EW1601, https://www.io-warnemuende.de/meramo-en.html). The simulation was performed at the North-German Supercomputing Alliance (HLRN, project id: mvk00054, zulassung.hlrn.de/kurzbeschreibungen/mvk00054.pdf). 
The model output data were processed and evaluated on servers provided by the project 'PROSO - Prozesse von Spurenstoffen in der Ostsee' (FKZ 03F0779A).
The model simulation was forced by operational meteorological data of the German Weather Service (DWD). Atmospheric nitrogen deposition data of medium spatial resolution of 16x16 km2 were provided by the Helmholtz-Zentrum Geesthacht within the EU BONUS SHEBA Project (Karl et al., 2019, doi: 10.5194/acp-2018-1317). Information on the riverine inputs, boundary conditions, and the model itself are provided in detail in Neumann et al. (2018b, doi: 10.5194/bg-2018-364).

Nitrogen from atmospheric deposition of shipping-related nitrogen, agricultural-related nitrogen, and total nitrogen has been tagged in the model simulation according to a method by Menésguen et al. (2006, 10.4319/lo.2006.51.1_part_2.0591). Therefore, all nitrogen-containing model variables exist four times in the output: once as regular variables and once per tagged nitrogen source (total, shipping-related, agricultural-related).

The concentrations of all prognostic biogeochemical model variables are given in nitrogen units according to the Redfield ratio.