Methanol-CO correlations in Mexico City pollution outflow from aircraft and satellite during MILAGRO
Item
Title (Dublin Core)
Methanol-CO correlations in Mexico City pollution outflow from aircraft and satellite during MILAGRO
Description (Dublin Core)
The correlation between methanol (CH<sub>3</sub>OH) and carbon monoxide (CO) is of particular interest for characterizing biogenic and anthropogenic emission sources of CH<sub>3</sub>OH and other chemical species. Here, the CH<sub>3</sub>OH/CO enhancement ratio (ΔCH<sub>3</sub>OH/ΔCO) in the lower to middle troposphere is examined using coincident CH<sub>3</sub>OH and CO observations from aircraft (NCAR C-130 and NASA DC-8) and from the Tropospheric Emission Spectrometer (TES) satellite during the MegaCity Initiative: Local and Global Research Observations (MILAGRO) in the Mexico City region in March 2006. ΔCH<sub>3</sub>OH/ΔCO ratios from the two in-situ aircraft measurements are far higher than previously reported CH<sub>3</sub>OH emission ratios relative to CO from US cities. This may reflect combustion of different fuel types in this area, and possibly photochemical production of CH<sub>3</sub>OH in Mexico City outflow. TES CH<sub>3</sub>OH and CO retrievals over the MILAGRO domain show relatively high sensitivity in the 600–800 hPa range, associated with Mexico City pollution outflow. The TES derived ΔCH<sub>3</sub>OH/ΔCO ratios during MILAGRO are 18–24 ppt ppb<sup>−1</sup>, which are similar to those observed from the DC-8 (26–39 ppt ppb<sup>−1</sup>), but lower than the C-130 observations (41–55 ppt ppb<sup>−1</sup>). Differences between the ΔCH<sub>3</sub>OH/ΔCO ratios measured aboard the two aircraft preclude an absolute validation of the TES-derived ratios for this dataset. The ΔCH<sub>3</sub>OH/ΔCO ratios observed from TES over this domain reflect bulk enhancements of CH<sub>3</sub>OH and CO in Mexico City outflow. Although the TES measurements are not expected to resolve small-scale variability in the ΔCH<sub>3</sub>OH/ΔCO ratio downwind of the strong source region of Mexico City, it is demonstrated that TES can clearly distinguish differences in the ΔCH<sub>3</sub>OH/ΔCO ratio due to different source categories of CH<sub>3</sub>OH. An example of this is shown by contrasting measurements over Mexico City (strong anthropogenic emissions) with those over the Amazon Basin (strong biogenic emissions). The results from this case study show the potential to gain insight into global sources of CH<sub>3</sub>OH and related species from satellite observations, especially for regions and time periods where no in situ measurements are available.
Creator (Dublin Core)
Xiao, Y.
Cady-Pereira, K. E.
Payne, V. H.
Millet, D. B.
Shephard, M. W.
Luo, M.
Alvarado, M.
Wells, K. C.
Apel, E. C.
Campos, T. L.
Singh, H. B.
Sachse, G. W.
Date (Dublin Core)
2018-08-10
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acpd-12-5705-2012
https://acp.copernicus.org/preprints/acp-2011-1029/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
