Causal wavelet analysis of ozone pollution contingencies in the Mexico City Metropolitan Area

Abstract: In the recent two decades, the Mexico City Metropolitan Area (MCMA) has been plagued by high concentrations of air pollutants, risking the health integrity of its inhabitants. Although some policies have been undertaken, they have been insufficient to deplete high air pollutants. Environmental contingencies are commonly imposed when the ozone concentration overpasses a certain threshold, which is well above the recommended maximum by the WHO. This work used a causal version of a generalized Morlet wavelet to characterize the dynamics of daily ozone concentration in the MCMA. The results indicated that the formation of dangerous ozone concentration levels is a consequence of accumulation and incomplete dissipation effects acting over a wide range of time scales. Ozone contingencies occurred when the wavelet coefficient power is increasing, which was linked to an inti-persistence behavior. It was proposed that the wavelet methodology could be used as a further tool for signaling the potential formation of adverse ozone pollution scenarios.