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Volume 17, issue 15 | Copyright
Atmos. Chem. Phys., 17, 9379-9398, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Aug 2017

Research article | 07 Aug 2017

Seasonal and spatial changes in trace gases over megacities from Aura TES observations: two case studies

Karen E. Cady-Pereira1, Vivienne H. Payne2, Jessica L. Neu2, Kevin W. Bowman2, Kazuyuki Miyazaki2,3, Eloise A. Marais4,a, Susan Kulawik5, Zitely A. Tzompa-Sosa6, and Jennifer D. Hegarty1 Karen E. Cady-Pereira et al.
  • 1Atmospheric and Environmental Research, Lexington, MA, USA
  • 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 3Japan Agency for Marine-Earth Science and Technology, Yokohoma, Kanagawa Prefecture, Japan
  • 4School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 5Bay Area Environmental Research Institute/NASA Ames, Mountain View, CA, USA
  • 6Department of Atmospheric Sciences, Colorado State University, Colorado Springs, CO, USA
  • anow at: School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, UK

Abstract. The Aura Tropospheric Emission Spectrometer (TES) is collecting closely spaced observations over 19 megacities. The objective is to obtain measurements that will lead to better understanding of the processes affecting air quality in and around these cities, and to better estimates of the seasonal and interannual variability. We explore the TES measurements of ozone, ammonia, methanol and formic acid collected around the Mexico City metropolitan area (MCMA) and in the vicinity of Lagos (Nigeria). The TES data exhibit seasonal signals that are correlated with Atmospheric Infrared Sounder (AIRS) CO and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD), with in situ measurements in the MCMA and with Goddard Earth Observing System (GEOS)-Chem model output in the Lagos area. TES was able to detect an extreme pollution event in the MCMA on 9 April 2013, which is also evident in the in situ data. TES data also show that biomass burning has a greater impact south of the city than in the caldera where Mexico City is located. TES measured enhanced values of the four species over the Gulf of Guinea south of Lagos. Since it observes many cities from the same platform with the same instrument and applies the same retrieval algorithms, TES data provide a very useful tool for easily comparing air quality measures of two or more cities. We compare the data from the MCMA and Lagos, and show that, while the MCMA has occasional extreme pollution events, Lagos consistently has higher levels of these trace gases.

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Short summary
Air quality is a major issue for megacities. Our paper looks at satellite measurements over Mexico City and Lagos of several trace gases gases related to air quality to determine the temporal and spatial variability of these gases, and it relates this variability to local conditions, such as topography, winds and biomass burning events. We find that, while Mexico City is known for severe pollution events, the levels of of pollution in Lagos are much higher and more persistent.
Air quality is a major issue for megacities. Our paper looks at satellite measurements over...