
Long-term observations show that surface ozone at WLG has increased significantly, by 0.21 ppbv year − 1 during spring season, 0.18 ppbv year − 1 during summer, 0.26 ppbv year − 1 during autumn, and 0.11 ppbv year − 1 during winter over the period 1994–2016 ( Xu et al., 2020). Jos Lelieveld, in Asian Atmospheric Pollution, 2022 2.1.1.3 Inter-annual ozone trend In both periods, the spatial distribution of WA is quite similar with a few changes in the southwestern part of the Emilia-Romagna region ( Fig. The winter season presents values from 117 to 416 mm during 1990s for WA, while during 2015s the values of WA range from 113 to 380 mm. In the same season but during 2015s, the WA varied from 82 to 647 mm showing the highest values (above 500 mm) in the mountain areas and the lowest values in the plain ( Fig. In the fall season, during 1990s the WA varied from 64 to 550 mm showing the higher values (above 500 mm) in the Northern Apennines and the lower values (below 100 mm) in the Po Plain.

The higher values (above 40) were identified in the mountain areas while the lower values (below 20 mm) were identified in the plain, especially in the northeastern part ( Fig. Background image source: Esri, Garmin, GEBCO, NOAA NGDC, and other contributors.ĭuring the summer season, the 1990s period recorded values between 11 and 62 mm, while the 2015s period recorded values between 7 and 47 mm.

Spatial distribution of seasonal WA in the Emilia-Romagna region.
