Estimating daily ozone levels in urban ambient air

Abstract Since tropospheric ozone poses a significant threat to public health, this research aims to estimate urban daily ozone levels using 2004–2021 polluting and meteorological data of three major European capitals (Madrid, Stockholm, and Rome). The resulting expression showed a goodness-of-fit of 84.99% (range 2–120 µg O 3 /m 3 ), with an average accuracy of 0.01 µg O 3 /m 3 (equivalent to 0.86%). According to the European legislative requirements for short-term ozone modeling (associated uncertainty < 50%), the total number of 2004–2021 daily exceedances was 0.079% (21 cases). As a novelty, the current work evaluated the performance of the suggested approach at both temporal (using data not included in the original approach) and geographical scales (applied to an area different from those used in the original approach), differing from previous studies that did not address these features. Temporally, a global r value of 0.863 was observed, also complying with the current legislative requirements for short-term ozone modeling. The RMSE, MAE, and MAPE metrics were 1.05 μg/m 3 , 1.11 μg/m 3 , and 11.16%, respectively (range 7 to 139 µg/m 3 ). Geographically, an r value of 0.921 was reached, meeting legislative requirements in 98.8% of data. RSME, MAE, and MAPE values of 1.79 µg/m 3 , 3.20 µg/m 3 , and 12.80% were observed. As a potential limitation, reanalysis datasets were used instead of independent observational data. Despite this, a validated, easy-to-implement approach for estimating daily urban ozone levels using satellite data is provided, reducing uncertainty due to limited information, which could complement European Legislative directives on short-term ambient air ozone modeling.