Abstract
Abstract. The impact of six heterogeneous gas–aerosol uptake reactions on tropospheric ozone and nitrogen species was studied using two chemical transport models, the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP MSC-W) and the European Centre Hamburg general circulation model combined with versions of the Hamburg Aerosol Model and Model for Ozone and Related chemical Tracers (ECHAM-HAMMOZ). Species undergoing heterogeneous reactions in both models include N2O5, NO3, NO2, O3, HNO3, and HO2. Since heterogeneous reactions take place at the aerosol surface area, the modelled surface area density (Sa) of both models was compared to a satellite product retrieving the surface area. This comparison shows a good agreement in global pattern and especially the capability of both models to capture the extreme aerosol loadings in east Asia. The impact of the heterogeneous reactions was evaluated by the simulation of a reference run containing all heterogeneous reactions and several sensitivity runs. One reaction was turned off in each sensitivity run to compare it with the reference run. The analysis of the sensitivity runs confirms that the globally most important heterogeneous reaction is the one of N2O5. Nevertheless, NO2, HNO3, and HO2 heterogeneous reactions gain relevance particularly in east Asia due to the presence of high NOx concentrations and high Sa in the same region. The heterogeneous reaction of O3 itself on dust is of minor relevance compared to the other heterogeneous reactions. The impacts of the N2O5 reactions show strong seasonal variations, with the biggest impacts on O3 in springtime when photochemical reactions are active and N2O5 levels still high. Evaluation of the models with northern hemispheric ozone surface observations yields a better agreement of the models with observations in terms of concentration levels, variability, and temporal correlations at most sites when the heterogeneous reactions are incorporated. Our results are loosely consistent with results from earlier studies, although the magnitude of changes induced by N2O5 reaction is at the low end of estimates, which seems to fit a trend, whereby the more recent the study the lower the impacts of these reactions.
Highlights
Nitrogen species, ozone, and atmospheric aerosols are major pollutants in the atmosphere, having strong impacts on ecosystems and human health, and interacting with climate (Ainsworth et al, 2012; Harrison and Yin, 2000; Simpson et al, 2014; IPCC, 2013)
Analysing all the possible differences in these two different models is beyond of the scope of this study, but it may well be that ECHAM-HAMMOZ overestimates the impact of HNO3 due to missing nitrate aerosol formation and EMEP underestimates the impact due to the use of only coarse sea salt and dust aerosol for the HNO3 and HO2 reactions
One can never know if models produce good results for the right reasons, we have shown that both ECHAM-HAMMOZ and EMEP can reproduce even daily ozone variations remarkably well at sites across the globe
Summary
Ozone, and atmospheric aerosols are major pollutants in the atmosphere, having strong impacts on ecosystems and human health, and interacting with climate (Ainsworth et al, 2012; Harrison and Yin, 2000; Simpson et al, 2014; IPCC, 2013). S. Stadtler et al.: Impacts of gas–aerosol uptake mainly removing NOx from the troposphere (Mozurkewich and Calvert, 1988; Dentener and Crutzen, 1993; Evans and Jacob, 2005; Chang et al, 2011; Brown and Stutz, 2012), which can lead to ozone reduction (Macintyre and Evans, 2010). Other oxidized nitrogen species undergo heterogeneous reactions on different aerosol types. Many modelling studies have been conducted over the years on these processes, but usually heterogeneous reactions were studied individually, and typically considering annual global budgets rather than detailed temporal or spatial resolution of the impacts (Dentener and Crutzen, 1993; Rudich et al, 1998; Saathoff et al, 2001; Bauer et al, 2004; Hodzic et al, 2006; Thornton et al, 2008; Chang et al, 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
