New perspectives on summertime UT/LS ozone over North America from the strategic IONS sounding network (2004, 2006)

The recent deployment of strategically designed and launch-coordinated ozonesonde networks has revolutionized sampling in the UT/LS (upper troposphere-lower stratosphere) with consistent temporal and vertical (100 m) resolution. Examples include the SHADOZ (Southern Hemisphere Additional Ozonesondes) tropical network , operating since 1998, and the campaign-based IONS (INTEX [Intercontinental Transport Experiment] Ozonesonde Network Study) networks over North America in July-August 2004 and March-August 2006, . In IONS, spatial and temporal variations within a regionally dense network allow evaluation of ozone distributions and comparisons with correlative satellite data and models [Tarasick et al., 2007]. Ozone budgets throughout the UT/LS are determined in unprecedented detail. We present selected discoveries from the 2004 and 2006 IONS soundings:

• IONS provided ~300 O3 profiles from eleven North American sites and the R/V R H Brown in the Gulf of Maine. With July-August 2004 dominated by low- pressure conditions over northeastern North America (NENA), the UT/LS was a mixture of stratospheric O3 interleaved with O3 from aged or relatively fresh pollution and lightning. With a filtered version of the Pierce and Grant [1998] laminar technique, we find that > 1/4 of free tropospheric O3 in NENA originated in the stratosphere [Thompson et al., 2007a,b]. Analysis of potential vorticity and Wallops ozonesondes (38N, 75.5W) in June-July-August 1996-2004 suggests that stratospheric contribution to the 2004 UT/LS O3 budgets is typical.
• IONS in 2006 covered boreal spring and summer, with a greater range (the eleven 2004 sites plus a dozen in California, New Mexico, Mexico City, Barbados and southwestern Canada). There was more pollution in the troposphere and regional UT/LS O3 contrasts between 2004 and 2006 but both years displayed a persistent UT ozone maximum [Cooper et al., 2007] over the summertime south- central US. The March 2006 period over Mexico revealed distinct UT/LS gravity wave influence.