Elsevier

Atmospheric Environment

Volume 43, Issue 6, February 2009, Pages 1189-1195
Atmospheric Environment

Impact of large scale circulation on European summer surface ozone and consequences for modelling forecast

https://doi.org/10.1016/j.atmosenv.2008.10.039Get rights and content

Abstract

In this study, we investigate the benefit for European ozone simulation of using day-to-day varying chemical boundary conditions produced by a global chemical weather forecast platform instead of climatological monthly means at the frontiers of a regional model. We performed two simulations over Europe using the regional (0.5 × 0.5°) CHIMERE CTM forced by global scale simulations based on the LMDz-INCA CTM. For summer 2005, ozone differences exceeding 20 ppb can be punctually found between these two simulations in the borders of the domain. The mean of the differences ranges between 0 and 3 ppb beyond 15° of the frontiers of the regional model.

Correlations with ground-based ozone measurements at more than 400 stations are slightly increased by the use of daily boundary conditions. The simulation of the temporal variability is significantly enhanced in particular for the daily means and daily maxima. As expected, the gain is higher at the borders of the regional domain.

The change of percentile distribution shows that the net impact of high temporal resolution boundary conditions is not of major concern for surface ozone peaks which are mainly due to local photochemistry. The use of daily boundary conditions is however necessary to correctly simulate concentrations in the 20–35 ppb range which are of crucial interest for human and vegetation exposure effects.

Introduction

Attention is paid to tropospheric ozone (O3) for its role as greenhouse gases impacting global climate (Forster et al., 2007) as well as for its impact on air quality in the boundary layer especially during smog events. Indeed, such latter events can cause both human health problems (West et al., 2007) and vegetation damage (Ashmore, 2005, Felzer et al., 2007). In order to monitor and prevent the impact of high ozone episodes on population's exposure, operational regional forecast systems were built up during the last decade (Honoré et al., 2008).

Such systems are based on regional (limited-area) chemistry-transport models (CTMs) that represent physical and chemical processes controlling ozone concentrations at spatial and temporal scales relevant for air quality concerns. These models have been widely evaluated in their “reanalysis” version against ground-based ozone measurements for several years (van Loon et al., 2007, Vautard et al., 2006) showing the ability of these tools to simulate summer ozone concentrations quite reasonably. Indeed, van Loon et al. (2007) show that the surface ozone concentrations simulated by the European models (used at their continental resolution, i.e. 30–50 km) have correlations with observations lying from 0.5 to 0.7 for daily means and 0.6 to 0.7 for daily maxima.

However, large uncertainties in the CTM results remain due to the quality and accuracy of their external forcings: meteorological fields, emissions of primary pollutants or chemical boundary conditions.

For example, long range transport of pollutants can significantly impact regional air quality (Fiore et al., 2002). This process impacts local ozone pollution by two ways differing in terms of both spatial and temporal scales. Firstly, it can modify by a few ppb the background ozone on which local ozone production is added (Parrish et al., 1993, Auvray and Bey, 2005). Secondly, sporadic transport events of highly polluted air masses from one continent to another induce local ozone increase by up to 5–10 ppb (Li et al., 2002). These two types of influences are important because both ozone peaks and moderate but continuous elevations of background ozone can impact human health and ecosystems. The impact of boundary conditions on regional scale ozone concentrations was recently investigated by Tang et al. (2007) and Song et al. (2008) for U.S.A. using downscaling approaches from global to regional models. Over Europe, the gain from an adequate representation of such large scale events in regional ozone forecasting remains to be investigated.

Global chemical forecast systems were recently developed based on global chemistry-climate models. Such tools allow, for example, to forecast large scale pollution events due to particular meteorological conditions (e.g. heat wave) as well as large biomass burning events. At the regional scale, chemical forecast systems use simplified large scale boundary conditions, generally monthly fields.

In this work, we quantify the benefit of using a global chemical weather forecast system to constrain the chemical concentrations on a daily basis at the geographical boundaries of a European regional forecast system. The cumulative effects of the recirculation of polluted European air masses and of the intercontinental transport on surface ozone concentrations are examined for summer 2005.

Section snippets

Modelling set-up

The daily averaged concentrations of pollutants simulated by a global chemistry-climate model (LMDz-INCA) are taken as lateral and top boundary conditions by the CHIMERE regional air pollution model for a forecast experiment over the summer 2005. This one-way nested platform was used to investigate the effect of future global ozone change on regional air quality in a similar configuration described in Szopa et al. (2006) and Szopa and Hauglustaine (2007).

The LMDz atmospheric General Circulation

Variability of daily ozone concentrations in the global model

We first investigate the temporal variability of the global LMDz-INCA daily ozone fields. Fig. 1 shows the standard deviation of the daily LMDz-INCA ozone concentrations around the mean of July and August. Results are displayed for the surface (i.e. first model level) and at 430 hPa (corresponding roughly to the upper limit of the CHIMERE domain). At the surface, this deviation exceeds 5 ppb over the most part of the area and can reach 12–15 ppb locally at the eastern frontier of the CHIMERE

Conclusion

In this study, we investigate the benefit of using day-to-day varying chemical boundary conditions instead of climatological monthly means at the frontiers of a regional model. For that purpose, simulations are performed over Europe using the regional (0.5 × 0.5°) CTM forced by global scale simulations based on the LMDz-INCA CTM. The impact on simulated surface ozone is significant. As expected, the gain is higher at the borders of the regional domain. Correlations with observations are slightly

Acknowledgments

The authors acknowledge EMEP, IER (University of Stuttgart) and UK Department of Environment for providing present day emissions for Europe. Thanks to the national environment agencies of Belgium, Swiss, Germany, Great Britain and France (IRCE-LINE, SAEFL, UBA, UK Department of Environment and the ADEME) for providing the validated O3 observations. Other ground-based ozone measurements were downloaded from the European Air Quality Database (http://air-climate.eionet.europa.eu/databases/airbase/

References (25)

  • P. Forster et al.

    Changes in atmospheric constituents and in radiative forcing

  • D.A. Hauglustaine et al.

    Interactive chemistry in the Laboratoire de Meteorologie Dynamique general circulation model: description and background tropospheric chemistry evaluation

    J. Geophys. Res.

    (2004)
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