Numerical modelling of 2003 summer forest fire impacts on air quality over Portugal

Abstract

In 2003 Portugal faced the worst fire season ever recorded. The main purpose of this work is to evaluate the effects of the 2003 forest fires on the air quality, applying four numerical modelling systems (LOTOS-EUROS, MM5-CMAQ, WRF/chem and MM5-CHIMERE), and to compare their results with air quality data from several monitoring stations in Portugal. Forest fire emissions have been calculated taking into account the most suitable parameters for Portuguese forest/fire characteristics and the area burned by each forest fire. They were added to the anthropogenic and biogenic gridded emissions, according to the fire location and assuming a uniform fire spread and injection into the mixing layer. Simulations were performed during August 2003 regarding gaseous and particulate matter pollutants. To better evaluate the impact of forest fire emission on the air quality, a baseline simulation was performed, including the “conventional” emissions, along with a forest fire simulation, which also considered emissions from forest fires. Modelling hourly results, namely particulate matter (PM) and ozone (O3) concentration, values have been compared to measurement data at several monitoring locations. In general, the different modelling systems show a good performance, which improves when forest fire emissions are considered, particularly for the PM concentrations. The influence of the forest fire emissions in O3 formation is not so evident and needs more attention. The evaluation of the impact of forest fires on the air quality should be included in air quality assessment procedures, specifically in areas that are often affected by forest fires, such as south Europe, and air quality modelling systems can be important tools to achieve this goal.