On the nature of air pollution dynamics in Mexico City—I. Nonlinear analysis

We have applied a nonlinear dynamic analysis to air quality data (ozone, carbon monoxide, nitrous oxide and sulfur dioxide) obtained at 13 of the surface stations of the automated monitoring network in Mexico City, following the work of Li et al. (1994, Atmospheric Environment28, 1707–1714). The time series used consisted of hourly data obtained during 1993. The analysis has helped to identify the nature of the dynamics of ozone production and we have determined the number of degrees of freedom of the system. Interestingly, this value varied with location within the city, ranging from two (at a station located downtown) to eight. We suggest that this difference may be linked to variations in local orography that forces a vortex-type circulation within the basin throughout the year.