Numerical Modeling Air Quality Forecasting Ozone Pollution Wrf-chem Urban Air Pollution Quito Atmospheric Chemistry

External authors:

• Gabriela Mancheno ( Pontificia Universidad Catolica de Chile , Ctr Sustainable Urban Dev CEDEUS )

Abstract:

Tropospheric ozone (O3) is a challenge in high-altitude tropical cities such as Quito, Ecuador, where complex topography, intense solar radiation, and anthropogenic emissions interact. This study evaluates the performance of the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for short-term ozone forecasting, 24-and 48-h predictions during wet, dry, and transitional seasons in 2018. WRF-Chem horizontal resolution was 2 km for the innermost domain and model performance was evaluated against hourly observations from six air quality monitoring stations. The model results reproduced the main diurnal and seasonal variability of ozone concentrations, although biases were identified, particularly in industrial areas. After applying a Model Output Statistics (MOS) correction, forecast accuracy improved substantially, with coefficients of determination (R2) reaching up to 0.98 and mean absolute errors reduced to 4-7 mu g/m3 at most stations. Seasonal performance varied, with the highest skill observed during the wet season (March) and reduced accuracy under transitional meteorological conditions. An independent out-of-sample evaluation of April forecasts showed that applying MOS correction factors derived from March improved predictive skill, increasing R2 values from 0.19 to 0.52 to 0.67-0.90 after correction. Despite persistent biases in industrial areas, these results demonstrate that WRF-Chem provides a robust physical baseline for short-term ozone forecasting in Quito, and that its operational performance can be enhanced through transparent MOS corrections. The proposed framework offers a transferable strategy for improving ozone forecasts in other high-altitude tropical cities and supports the development of early warning systems and evidence-based air quality management.