Technical note: How are NH 3 dry deposition estimates affected by combining the LOTOS-EUROS model with IASI-NH 3 satellite observations?

van der Graaf, Shelley C.; Dammers, Enrico; Schaap, Martijn; Erisman, Jan Willem

Atmospheric levels of reactive nitrogen have increased substantially during the last century resulting in increased nitrogen deposition to ecosystems, causing harmful effects such as soil acidification, reduction in plant biodiversity and eutrophication in lakes and the ocean. Recent developments in the use of atmospheric remote sensing enabled us to resolve concentration fields of inline-formulaNH3 with larger spatial coverage. These observations may be used to improve the quantification of inline-formulaNH3 deposition. In this paper, we use a relatively simple, data-driven method to derive dry deposition fluxes and surface concentrations of inline-formulaNH3 for Europe and for the Netherlands. The aim of this paper is to determine the applicability and the limitations of this method for inline-formulaNH3. Space-born observations of the Infrared Atmospheric Sounding Interferometer (IASI) and the LOTOS-EUROS atmospheric transport model are used. The original modelled dry inline-formulaNH3 deposition flux from LOTOS-EUROS and the flux inferred from IASI are compared to indicate areas with large discrepancies between the two. In these areas, potential model or emission improvements are needed. The largest differences in derived dry deposition fluxes occur in large parts of central Europe, where the satellite-observed inline-formulaNH3 concentrations are higher than the modelled ones, and in Switzerland, northern Italy (Po Valley) and southern Turkey, where the modelled inline-formulaNH3 concentrations are higher than the satellite-observed ones. A sensitivity analysis of eight model input parameters important for inline-formulaNH3 dry deposition modelling showed that the IASI-derived dry inline-formulaNH3 deposition fluxes may vary from inline-formula∼ 20 % up to inline-formula∼50 % throughout Europe. Variations in the inline-formulaNH3 dry deposition velocity led to the largest deviations in the IASI-derived dry inline-formulaNH3 deposition flux and should be focused on in the future. A comparison of inline-formulaNH3 surface concentrations with in situ measurements of several established networks – the European Monitoring and Evaluation Programme (EMEP), Meetnet Ammoniak in Natuurgebieden (MAN) and Landelijk Meetnet Luchtkwaliteit (LML) – showed no significant or consistent improvement in the IASI-derived inline-formulaNH3 surface concentrations compared to the originally modelled inline-formulaNH3 surface concentrations from LOTOS-EUROS. It is concluded that the IASI-derived inline-formulaNH3 deposition fluxes do not show strong improvements compared to modelled inline-formulaNH3 deposition fluxes and there is a future need for better, more robust, methods to derive inline-formulaNH3 dry deposition fluxes.



van der Graaf, Shelley C. / Dammers, Enrico / Schaap, Martijn / et al: Technical note: How are NH3 dry deposition estimates affected by combining the LOTOS-EUROS model with IASI-NH3 satellite observations?. 2018. Copernicus Publications.


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