Effects of biogenic emissions on an extreme event of tropospheric ozone pollution over southwestern Europe (Iberian Peninsula)

Biogenic emissions are those emitted by natural sources such as plants, trees and soil. The main biogenic volatile organic compounds (BVOCs) involved in these emissions are isoprene and monoterpenes, which can undergo photochemical reactions in the atmosphere and contribute to the formation of tropospheric ozone. Warmer temperatures and increased solar radiation can intensify emission rates. On the other hand, different BVOCs may respond differently to water stress. For example, isoprene emissions have been observed to decrease under water stress conditions, while emissions of some monoterpenes may increase. Therefore, the study of biogenic emissions is essential for understanding the Earth's atmosphere, especially in the context of climate change and air quality. To understand the interactions between biogenic emissions and near-surface ozone, advanced atmospheric models are required.

This study presents a series of meteorology-chemistry online coupled simulations using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to investigate the sensitivity of surface ozone concentration to changes in biogenic emissions during an extreme ozone concentration event (12-15 July 2022) over the Iberian Peninsula. Biogenic emissions are introduced into WRF-Chem using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) version 2.04. The experiments consist in varying the biogenic emissions by perturbing parameters related to the emission rates and the type and amount of vegetation.

Preliminary results show that the inclusion of biogenic emissions can increase the near-surface ozone concentrations by up to 30% in some locations. Although we do not obtain a much better performance of the model in representing the observed ozone series, the observed extreme values can be better explained when biogenic emissions are considered. Therefore, it is fundamental to consider both natural and anthropogenic sources when addressing ozone pollution.

 

Acknowledgements: Project PID2020-115693RB-I00 funded by MCIN/ AEI /10.13039/501100011033