Investigating ground-level ozone pollution in semi-arid and arid regions of Arizona using WRF-Chem v4.4 modeling

However, the model tends to overestimate surface NO 2 concentrations, particularly during nighttime hours. Among the three cities studied, Phoenix (PHX) and Tucson (TUS) exhibit a negative bias in both hourly and MDA8 O 3 levels, while Yuma demonstrates a relatively large positive bias. The simulated mean hourly and MDA8 O 3 concentrations in Phoenix are 44.6 and 64.7 parts per billion (ppb), respectively, compared to observed values of 47.5 and 65.7 ppb, resulting in mean negative biases of - 2.9 and - 1.0 ppb, respectively.Furthermore, the analysis of the simulated ratio of formaldehyde (HCHO) to NO 2 ( HCHO / NO 2 ; FNR), reveals interesting insights of the sensitivity of O 3 to its precursors.

In Phoenix, the FNR varies from a VOC (volatile organic compound)-limited regime in the most populated areas to a transition between VOC-limited and NO x -limited regimes throughout the metro area, with an average FNR of 1.15. In conclusion, this study sheds light on the persistent challenge of ground-level O 3 pollution in semi-arid and arid regions, using the state of Arizona as a case study.