Improved modelling of atmospheric ammonia over Denmark using the coupled modelling system DAMOS

Abstract

Abstract.A local-scale Gaussian dispersion-deposition model (OML-DEP) has been coupled to a regional chemistry-transport model (DEHM with a resolution of approximately 6 km × 6 km over Denmark) in the Danish Ammonia Modelling System, DAMOS. Thereby, it has been possible to model the distribution of ammonia concentrations and depositions on a spatial resolution down to 400 m × 400 m for selected areas in Denmark. DAMOS has been validated against measured concentrations from the dense measuring network covering Denmark. Here measured data from 21 sites are included and the validation period covers 2-5 years within the period [2005][2006][2007][2008][2009]. A standard time series analysis (using statistic parameters like correlation and bias) shows that the coupled model system captures the measured time series better than the regional-scale model alone. However, our study also shows that about 50 % of the modelled concentration level at a given location originates from non-local emission sources. The local-scale model covers a domain of 16 km × 16 km, and of the locally released ammonia (NH 3 ) within this domain, our simulations at five sites show that 14-27 % of the locally (within 16 km × 16 km) emitted NH 3 also deposits locally. These results underline the importance of including both high-resolution local-scale modelling of NH 3 as well as the regional-scale component described by the regional model. The DAMOS system can be used as a tool in environmental management in relation to assessments of total nitrogen load of sensitive nature areas in intense agricultural regions. However, high spatio-temporal resolution in input parameters like NH 3 emissions and landuse data is required.

Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange

“…Comparisons between computed and measured ambient NH 3 concentrations demonstrated considerable improvements in model performance over Denmark when the high spatial and temporal resolution emission inventory was applied, instead of the conventional (static) seasonal variations approach (Skjøth et al, 2004). Further, Geels et al (2012) showed that the coupled DEHM/OML-DEP model system captured the measured NH 3 time series in Denmark better than the regional-scale model alone, and that about 50 % of the modelled concentration level at a given location originated from non-local emission sources. However, the coupled DAMOS model still overestimated observed local ammonia concentrations across Denmark, which might in part be explained by overestimated national emissions, by underestimated rates of conversion to NH + 5212 C. R. Flechard et al: Biosphere-atmosphere ammonia exchange and, as in the LOTOS-EUROS case (Wichink Kruit et al, 2012), by the model grid square size.…”

“…Use of plume or Lagrangian 1-D models close to the source (see Asman, 2001;Hertel et al, 2006Hertel et al, , 2011 or coupling of sub-grid dispersion models to CTMs (e.g. Geels et al, 2012) should help bridge the gap between groundbased, single-point observations and spatially averaged CTM outputs, and could be used to help parameterize larger scale CTM models in future.…”

“…the LOTOS-EUROS model (using revised DEPAC 3.11) (Wichink Kruit et al, 2012); the coupled CMAQ-EPIC model (Cooter et al, 2010(Cooter et al, , 2012Bash et al, 2012); and AURAMS (Zhang et al, 2010). Other CTMs have meanwhile focused on improving the treatment of subgrid variability (DAMOS; Geels et al, 2012) or the spatial and temporal distribution of NH 3 emissions by field-applied mineral fertiliers (CHIMERE/Volt'Air, Hamaoui-Laguel et al, 2012).…”

“…20 km) Gaussian plume dispersion and deposition model OML-DEP (400 × 400 m 2 resolution) (Geels et al, 2012). The model may be coupled to a code (Skjøth et al, 2011) for calculating ammonia emission on the European scale, accounting for local climate and local management, in which a modular approach is applied for deriving data as input to the temporally varying ammonia emission model.…”

“…unified EMEP MSC-W model ( Vieno et al, 2010);a Wesely (1989) approach is used in CHIMERE (Vautard et al, 2001;LMD, 2011); DEPAC is used in OPS-Pro 4.1 (van Jaarsveld, 2004); EMEP R c /V d approach is used in the coupled Danish Ammonia Modelling System DAMOS (DEHM/OML-DEP) (Geels et al, 2012); combined DEPAC and EMEP parameterizations in MATCH (Klein et al, 2002); and LUC-specific values of R c are used in FRAME (Singles et al, 1998). Nevertheless, a few instances of χ c model implementation in CTMs have recently been reported, using new χ c parameterization schemes (see Sect.…”