A wavelet analysis of multiday extreme ozone and its precursors in Mexico city during 2015–2016

Daniel Aguilar-Velázquez, Israel Reyes-Ramírez

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


During the past decades, many authors have studied extreme ozone (O 3) events on successive days in several cities around the world, where extreme pollution concentrations are considered as values exceeding air quality standards. These multiday episodes are caused by different variables: weather conditions, pollution precursors life times and air pollution transport. However, a complete characterization of the temporal behavior of multiday extreme O 3 episodes is still lacking. In the present paper, we used the Haar wavelet transform to study the period (T in days) of multiday extreme O 3 episodes in Mexico city during 2015–2016, when 10 ozone contingencies occurred and changes in driving restrictions were implemented. In addition, we studied the temporal correlations between extreme O 3 and extreme: nitrogen dioxide (NO 2), carbon monoxide (CO) and ultraviolet B radiation (UVB) for a broad range of time scales by means of the Haar Wavelet cross-correlation method. The results show that multiday O 3 episodes mainly exhibit periods of T>4 days, while NO 2 and CO show multiday episodes comprising principally periods of T>2 days. The cross correlation analysis reveals that CO and NO 2 are temporal anti-correlated with O 3 for daily variations T<1. However, NO 2 and CO are strongly and moderately correlated with O 3 for T>4, respectively, indicating that NO 2, CO and O 3 are correlated in a multi-temporal clustered form.

Original languageAmerican English
Pages (from-to)112-119
Number of pages100
JournalAtmospheric Environment
StatePublished - 1 Sep 2018


  • Multiday episodes
  • Ozone
  • Ozone precursors
  • Wavelet analysis

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