Near-surface ozone trends over Europe in RegCM3/CAMx simulations for the time period 1996–2006

Abstract

The RegCM3/CAMx modeling system is applied to estimate near surface ozone trends over Europe for the time period 1996–2006. In order to assess the impact of changing anthropogenic emissions and meteorology on modeled ozone trends two simulations were performed: The first simulation (CONEM) was forced from constant anthropogenic emissions based on the EMEP emissions of the year 1996, while the second simulation (VAREM) was forced from year to year varying anthropogenic emissions based on the EMEP emissions of the years 1996–2006.Near surface ozone measurements from the EMEP database are used for assessing the skill of the modeling system to reproduce the observed ozone trends. Concerning VAREM simulation the main pattern is a significant positive annual trend over southern UK and Benelux which is also detected in the observations, attributed to the reduction of ozone titration by NO as a result of NOx emissions control policies. Significant negative ozone trends are found over the Mediterranean due to reduction of ozone precursors emissions over continental Europe. As far as it concerns CONEM simulation a significant increase of ozone is found during summer associated with the heatwave event of 2003. Overall, the observed ozone trends are captured fairly well by the RegCM3/CAMx modeling system over the highly polluted areas of central and western Europe but only partially reproduced or not captured at all at the rest of Europe, probably due to limitations of the model setup to capture background ozone variability related to processes such as intercontinental transport and stratosphere–troposphere exchange.