Remote measurement of NO2 in the brown cloud over Albuquerque,New Mexico

Remote measurements of nitrogen dioxide (NO₂) were recorded in the brown cloud over Albuquerque, NM, using absorption spectroscopy in the winter of 1987-88 and summer of 1989. The NO₂ burdens (optical densities) measured in this manner were found to be in excess of 100 ppm-m. These long pathlength measurements correspond to total concentrations of approximately 5–10 ppb over the integrated observation pathlengths, which ranged from 10–20 km. These concentrations compare well with single location, independent NO _x analyses. Using two correlation (absorption) spectrometers simultaneously, it was shown that the NO₂ distribution is not uniform over the city and can change on the order of minutes in the boundary layer late in the day, demonstrating the advantages of NO₂ optical measurements for assessing the location and extent of urban nitrogen dioxide levels in the boundary layer.