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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 24 | Copyright
Atmos. Chem. Phys., 17, 15151-15165, 2017
https://doi.org/10.5194/acp-17-15151-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Dec 2017

Research article | 21 Dec 2017

Gradients of column CO2 across North America from the NOAA Global Greenhouse Gas Reference Network

Xin Lan1,2, Pieter Tans1, Colm Sweeney1,2, Arlyn Andrews1, Andrew Jacobson1,2, Molly Crotwell1,2, Edward Dlugokencky1, Jonathan Kofler1,2, Patricia Lang1, Kirk Thoning1, and Sonja Wolter1,2 Xin Lan et al.
  • 1National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Boulder, CO, USA
  • 2University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA

Abstract. This study analyzes seasonal and spatial patterns of column carbon dioxide (CO2) over North America, calculated from aircraft and tall tower measurements from the NOAA Global Greenhouse Gas Reference Network from 2004 to 2014. Consistent with expectations, gradients between the eight regions studied are larger below 2km than above 5km. The 11-year mean CO2 dry mole fraction (XCO2) in the column below  ∼ 330hPa ( ∼ 8km above sea level) from NOAA's CO2 data assimilation model, CarbonTracker (CT2015), demonstrates good agreement with those calculated from calibrated measurements on aircraft and towers. Total column XCO2 was attained by combining modeled CO2 above 330hPa from CT2015 with the measurements. We find large spatial gradients of total column XCO2 from June to August, with north and northeast regions having  ∼ 3ppm stronger summer drawdown (peak-to-valley amplitude in seasonal cycle) than the south and southwest regions. The long-term averaged spatial gradients of total column XCO2 across North America show a smooth pattern that mainly reflects the large-scale circulation. We have conducted a CarbonTracker experiment to investigate the impact of Eurasian long-range transport. The result suggests that the large summertime Eurasian boreal flux contributes about half of the north–south column XCO2 gradient across North America. Our results confirm that continental-scale total column XCO2 gradients simulated by CarbonTracker are realistic and can be used to evaluate the credibility of some spatial patterns from satellite retrievals, such as the long-term average of growing-season spatial patterns from satellite retrievals reported for Europe which show a larger spatial difference ( ∼ 6ppm) and scattered hot spots.

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We analyze spatial patterns of column CO2 over North America using well-calibrated aircraft and tall tower measurements. We find that the long-term averaged spatial gradients of column CO2 across North America show a smooth pattern that mainly reflects the large-scale circulation. Our results can serve as a good reference for evaluating current and future column CO2 retrievals from both ground and satellite platforms.
We analyze spatial patterns of column CO2 over North America using well-calibrated aircraft and...
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