ON THE NATURE OF AIR-POLLUTION DYNAMICS IN MEXICO-CITY .1. NONLINEAR-ANALYSIS

We have applied a nonlinear dynamic analysis to air quality data (ozon e, carbon monoxide, nitrous oxide and sulfur dioxide) obtained at 13 o f the surface stations of the automated monitoring network in Mexico C ity, following the work of Li er nl. (1994, Atmospheric Environment 28 , 1707-1714). The time series used consisted of hourly data obtained d uring 1993. The analysis has helped to identify the nature of the dyna mics of ozone production and we have determined the number of degrees of freedom of the system. Interestingly, this value varied with locati on within the city, ranging From two (at a station located downtown) t o eight. We suggest that this difference may be linked to variations i n local orography that forces a vortex-type circulation within the bas in throughout the year. Copyright (C) 1996 Elsevier Science Ltd