Ozone modelling and mapping for risk assessment: an overview of different approaches for human and ecosystems health

Tropospheric ozone (O3) is one of the most concerned air pollutants due to its widespread impacts on land-vegetated ecosystems and human health. Ozone is also the third greenhouse gas for radiative forcing. Consequently, it should be carefully and continuously monitored to estimate its potential adverse impacts, especially in those regions where concentrations are high. Continuous large-scale O3 concentration measurement is crucial but may be unfeasible because of economic and practical limitations; therefore, quantifying the real impact of O3 over large areas is currently an open challenge. Thus, one of the final objectives of O3 modelling is to reproduce maps of continuous concentrations (both spatially and temporally) and risk assessment for human and ecosystem health. We here reviewed the most relevant approaches used for O3 modelling and mapping starting from the simplest geo-statistical approaches and increasing in complexity up to simulations embedded into the global/regional circulation models and the pros and cons of each mode are highlighted. The analysis showed that a simpler approach (mostly statistical models) is suitable for mapping O3 concentrations at the local scale, where enough O3 concentration data are available. The associated error in mapping can be reduced by using more complex methodologies, based on co-variables. The models available at the regional or global level are used depending on the needed resolution and the domain where they are applied to. Increasing the resolution corresponds to an increase in the prediction but only up to a certain limit. However, with any approach, the ensemble models should be preferred.