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

作者：Aguilar Velazquez Daniel^*; Reyes Ramirez Israel

来源：Atmospheric Environment, 2018, 188: 112-119.

DOI：10.1016/j.atmosenv.2018.06.017

• Ozone
• Ozone precursors
• Multiday episodes
• Wavelet analysis

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 (NO2), 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 NO2 and CO show multiday episodes comprising principally periods of T > 2 days. The cross correlation analysis reveals that CO and NO2 are temporal anti-correlated with O-3 for daily variations T < 1. However, NO2 and CO are strongly and moderately correlated with O-3 for T > 4, respectively, indicating that NO2, CO and O-3 are correlated in a multi-temporal clustered form.

• 出版日期2018-9