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NOAA Research 2007 Outstanding Scientific Paper Awards

“Large upper tropospheric ozone enhancements above midlatitude North America during summer: In situ evidence from the IONS and MOZAIC ozone measurement network”

Owen R. Cooper, Andreas Stohl, Michael Trainer, Anne M. Thompson, Jacquelyn C. Witte, Samuel J. Oltmans, Gary Morris, Kenneth E. Pickering, James H. Crawford, Gao Chen, Ronald C. Cohen, Timothy H. Bertram, Paul J. Wooldridge, Anne E. Perring, William H. Brune, John Merrill, Jennie L. Moody, David Tarasick, Philippe Nédélec, Gerry Forbes, Michael J. Newchurch, Frank J. Schmidlin, Bryan J. Johnson Solene Turquety, Steven L. Baughcum, Xinrong Ren, Fred. C. Fehsenfeld, James F. Meagher, Nicole Spichtinger, Clyde C. Brown, Stuart A. McKeen, I. Stuart McDermid, and Thierry Leblanc

ABSTRACT
The most extensive set of free tropospheric ozone measurements ever compiled across midlatitude North America was measured with daily ozonesondes, commercial aircraft and a lidar at 14 sites during July-August 2004. The model estimated stratospheric ozone was subtracted from all profiles, leaving a tropospheric residual ozone. On average the upper troposphere above midlatitude eastern North America contained 15 ppbv more tropospheric residual ozone than the more polluted layer between the surface and 2 km above sea level. Lowest ozone values in the upper troposphere were found above the two upwind sites in California. The upper troposphere above midlatitude eastern North America contained 16 ppbv more tropospheric residual ozone than the upper troposphere above three upwind sites, with the greatest enhancement above Houston, Texas, at 24 ppbv. Upper tropospheric CO measurements above east Texas show no statistically significant enhancement compared to west coast measurements, arguing against a strong influence from fresh surface anthropogenic emissions to the upper troposphere above Texas where the ozone enhancement is greatest. Vertical mixing of ozone from the boundary layer to the upper troposphere can only account for 2 ppbv of the 16 ppbv ozone enhancement above eastern North America; therefore the remaining 14 ppbv must be the result of in situ ozone production. The transport of NOx tracers from North American anthropogenic, biogenic, biomass burning, and lightning emissions was simulated for the upper troposphere of North America with a particle dispersion model. Additional box model calculations suggest the 24 ppbv ozone enhancement above Houston can be produced over a 10 day period from oxidation reactions of lightning NOx and background mixing ratios of CO and CH4. Overall, we estimate that 69–84% (11–13 ppbv) of the 16 ppbv ozone enhancement above eastern North America is due to in situ ozone production from lightning NOx with the remainder due to transport of ozone from the surface or in situ ozone production from other sources of NOx. FULL TEXT pdf

Cumulative lightning N emissions from CG and IC flashes between 21 June and 15 August 2004

Cumulative lightning N emissions from CG and IC flashes between 21 June and 15 August 2004. (larger image)

Locations of the fourteen ozone profile sites in 2004

Locations of the fourteen ozone profile sites in 2004: T, Trinidad Head; L, Table Mountain/MOZAIC; H, Houston; V, Huntsville; A, Atlanta; W, Wallops Island; D, Washington DC; Y, New York City; N, Narragansett; B, research vessel Ronald H. Brown; S, Sable Island; M, Montreal; O, Ontario; and P, Pellston. The locations of the tropical portions of the MOZAIC flights to and from Caracas (C) during 1999–2004 are also shown. (larger image)

Distributions of measured NOx from the DC8 above eastern North America during 1 July to 15 August 2004 and the corresponding FLEXPART lightning NOx tracer values

Distributions of measured NOx (blue) from the DC8 above eastern North America during 1 July to 15 August 2004 and the corresponding FLEXPART lightning NOx tracer values (red). Shown are the median values (solid lines) and the 10th and 90th percentiles (dashed lines) with modeled NOx lifetimes of (a) 1 day, (b) 2 days, and (c) 4 days. (larger image)


 

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10/22/07