Characterizing mega-city pollution with TES O3 and CO measurements

Concurrent tropospheric O 3 and CO vertical profiles from the Tropospheric Emission Spectrometer (TES) during the MILAGRO/INTEX-B aircraft campaigns over the Mexico City Metropolitan Area (MCMA) allow us to characterize mega-city pollution. Outflow from the MCMA occurred predominantly at 600–800 hPa, evident in O 3 , CO, and NO x 5 enhancements in the in situ observations. We examined O 3 , CO, and their correlation at 600–800 hPa from TES retrievals, aircraft measurements, and GEOS-Chem model results over the aircraft coverage (within a radius of ∼700 km around MCMA). The enhancements in O 3 and CO seen in the in situ measurements are not apparent in TES data, due to the lack of TES coverage during several strong pollution events. However, 10 TES O 3 and CO data are consistent with the aircraft observations on a daily mean basis (50–60 ppbv and 100–130 ppbv for O 3 and CO respectively). The O 3-CO correlation coefficients and enhancement ratios (∆O 3 /∆CO) derived from TES data are in good agreements with those derived from the aircraft observations and GEOS-Chem model results (r:0.5–0.9;∆O 3 /∆CO: 0.3–0.4), reflecting significant springtime photochemical 15 production over MCMA and the surrounding region.