Satellite-Based Tropospheric NO2 Column Trends in the Last 10 Years Over Mexican Urban Areas Measured by the Ozone Monitoring Instrument

Abstract:

Population density and economic activities in urban agglomerations have drastically increased in many cities in Mexico during the last decade. Several factors are responsible for increased urbanization such as a shift of people from rural to urban areas while looking for better education, services and job opportunities as well as the natural growth of the urban areas themselves. Urbanization can create great social, economic and environmental pressures and changes which can easily be observed in most urban agglomerations in the world. In this study, we have focused on analyzing tropospheric NO₂ (nitrogen dioxide) column trends over Mexican urban areas that have a population of at least one million inhabitants according to the latest 2010 population census. Differential Optical Absorption Spectroscopy (DOAS) measurements of NO₂ conducted by the space-borne Ozone Monitoring Instrument (OMI) on board the Aura satellite between 2005 and 2014 have been used for this analysis. This dataset has allowed us to obtain a satellite-based 10-year tropospheric NO₂ column trend over the most populated Mexican cities which include the dominating metropolitan area of Mexico City with more than twenty million inhabitants as well as ten other Mexican cities with a population ranging between one to five million inhabitants with a wide range of activities (commercial, agricultural or heavily industrialized) as well as two important border crossings. Distribution maps of tropospheric NO₂ columns above the studied urban agglomerations were reconstructed from the analyzed OMI dataset, allowing to identify areas of interest due to clear NO₂ enhancements inside these urban regions.