Impact of large scale circulation on European summer surface ozone and consequences for modelling forecast
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)
- et al.
A comparison of simulated and observed ozone mixing ratios for the summer of 1998 in Western Europe
Atmos. Environ.
(2001) Evaluation of long-term ozone simulations from seven regional air quality models and their ensemble
Atmos. Environ.
(2007)- et al.
Validation of a deterministic forecasting system for the ozone concentrations over the Paris area
Atmos. Environ.
(2001) - et al.
Simulation of ozone during the August 2003 heat wave and emission control scenarios
Atmos. Environ.
(2005) Assessing the future global impacts of ozone on vegetation
Plant Cell Environ.
(2005)- et al.
Long-range transport to Europe: seasonal variations and implications for the European ozone budget
J. Geophys. Res.
(2005) Air Pollution by Ozone in Europe in Summer 2005
(2006)- et al.
Impacts of ozone on trees and crops
C.R. Geosci.
(2007) - et al.
Linking ozone pollution and climate change: the case for controlling methane
Geophys. Res. Lett.
(2002) - et al.
Impact of biogenic hydrocarbons on tropospheric chemistry: results from a global chemistry-climate model
Atmos. Chem. Phys.
(2005)
Changes in atmospheric constituents and in radiative forcing
Interactive chemistry in the Laboratoire de Meteorologie Dynamique general circulation model: description and background tropospheric chemistry evaluation
J. Geophys. Res.
Cited by (46)
Impact of time-dependent chemical boundary conditions on tropospheric ozone simulation with WRF-Chem: An experiment over the Metropolitan Area of São Paulo
2018, Atmospheric EnvironmentCitation Excerpt :Currently, air quality modeling and forecast are being performed for Southeastern Brazil with WRF-Chem (Andrade et al., 2015). Nevertheless, uncertainties in model inputs as meteorological information, emission inventories and chemical boundary conditions (CBC) may affect model results (Szopa et al., 2009; Lam and Fu, 2009). For MASP, sensitivity tests were performed to evaluate the quality in meteorological input and emission inventories, but the impacts of chemical boundary conditions have not been addressed yet, despite its importance in the description of pollutants behavior inside the modeling domain.
Evaluation of Meso-NH and WRF/CHEM simulated gas and aerosol chemistry over Europe based on hourly observations
2016, Atmospheric ResearchCitation Excerpt :This is consistent with Solazzo et al. (2013) who found that model performance for ozone in the BL was generally good and mainly influenced by lateral boundary conditions and surface processes such as emissions, transport and photochemistry. Appel et al. (2012) underlined the influence of the forcing model for surface ozone over North America by improving the CMAQ model simulations using the global GEOS-Chem model instead of GEMS (Global and regional Earth-system Monitoring using Satellite and in-situ data) data (Schere et al., 2012) for the boundary conditions However, if the surface ozone is mainly influenced by local photochemistry instead of the pollution inflow, the surface ozone mixing ratio can have low sensitivity large-scale chemical conditions (Szopa et al., 2009). For vertical profiles, Tang et al. (2007) found that the mean O3 vertical profile below 3 km was insensitive to changes in chemical boundary conditions, whereas CO concentrations were sensitive throughout the troposphere.
A standardized methodology for the validation of air quality forecast applications (F-MQO): lessons learnt from its application across Europe
2023, Geoscientific Model Development