Trend Analysis Of Reduced Nitrogen Components Over The Netherlands With The Emep4nl And Ops Model

Declining ammonia emissions are not always reflected in ammonia concentrations due to physicochemical processes and meteorology. Here we present a trend analysis of reduced nitrogen components over the Netherlands using two different types of atmospheric transport models: the Eulerian grid model EMEP/MSC-W and the plume model OPS. We employ calculations with the Eulerian grid model EMEP/MSC-W for the Netherlands in its EMEP4NL configuration. Using the Weather Research Forecast (WRF) model as meteorological driver plus detailed emission data over the Netherlands as input into the EMEP4NL model, we present simulation results over the Netherlands of reduced nitrogen components from this model at a horizontal resolution of 1.3 x 2.1 km. Using this configuration of the EMEP/MSC-W model (EMEP4NL), a trend analysis is performed over the period 2006-2015 for concentration and deposition of reduced nitrogen components over the Netherlands. The same analysis is performed with the OPS-model, a plume model with a Lagrangian trajectory model for long range transport. Both models use the same MACC III emission distribution for countries outside of the Netherlands, and spatially more detailed emissions for the Netherlands itself. Emission totals per SNAP (Supporting National Action and Planning) sector per country are used over the period 2006-2015, according to the latest CEIP (Centre on Emissions Inventories and Projections) expert estimates. The OPS-model is driven with yearly specific meteorological fields provided by the Royal Netherlands Meteorological Institute (KNMI). Furthermore, the OPSmodel parameterizes its chemistry, whereas EMEP4NL uses a state-of-the-art chemistry scheme. Results from ammonia concentrations, ammonium concentrations and wet deposition as calculated with both models, are first compared with observations from the National Air Quality Monitoring Network in the Netherland (LML). Calculations of ammonia and wet deposition both agree well with the measurements in the OPS and the EMEP4NL model. Ammonium is better represented by calculations with the EMEP4NL model than by the OPS-model. Measurements of dry deposition of reduced nitrogen are very limited, therefore only a comparison is made between the model results of EMEP4NL and OPS. Subsequently, a trend analysis is performed over the period 2006-2015 for the reduced nitrogen components for both model calculation results and the measurements. The trends of all components are calculated over the mean values of monitoring stations over the Netherlands. The reported decline in the emissions of ammonia is not reflected in the ammonia concentrations and wet deposition of reduced nitrogen as measured and calculated with the OPS and the EMEP4NL model. Ammonium concentrations on the other hand are declining (also) due to the decrease of the SOx emissions over the period 2006-2015. Finally, both models show a slight decline in the dry deposition values, despite the fact that both models (and observations) do not show a decrease in the ammonia concentrations. A more detailed analysis of the comparison of dry deposition of reduced nitrogen between both models, and the influence of the physicochemical processes and meteorology is in preparation. Overall, it is found that the calculated trends for the different reduced nitrogen components with a grid model like EMEP4NL and a plume model like OPS are roughly in line with each other.