Spatial distribution and transport patterns of NO2 in the Tijuana – San Diego area

The atmospheric composition of the San Diego – Tijuana border is affected by transport of air pollutants between both regions and in both directions. In this study we show NO2 transport events identified during Cal–Mex 2010 field experiment at two different ground sites, located one downwind of the other. This field campaign was designed to overlap with the closing weeks of CalNex project to observe trans–boundary pollution transport in this area. The measurements showed a clear dispersion pattern of NO2 towards the east–southeast on several occasions during the field experiment. Additionally, the NO2 column distribution above the Tijuana – San Diego region was reconstructed from the OMI satellite data product, and a cluster analysis with the corresponding meteorological data was performed to identify four distinct wind patterns yielding different NO2 distribution maps and detecting dominant wind patterns in this region, either towards the E–SE or E–NE approximately 86% of the time.