Intercontinental Chemical Transport Experiment Ozonesonde Network Study (IONS) 2004: 1. Summertime upper troposphere/lower stratosphere ozone over northeastern North America

Abstract

Coordinated ozonesonde launches from the Intercontinental Transport Experiment (INTEX) Ozonesonde Network Study (IONS) (http://croc.gsfc.nasa.gov/intex/ions.html) in July‐August 2004 provided nearly 300 O 3 profiles from eleven North American sites and the R/V Ronald H. Brown in the Gulf of Maine. With the IONS period dominated by low‐pressure conditions over northeastern North America (NENA), the free troposphere in that region was frequently enriched by stratospheric O 3 . Stratospheric O 3 contributions to the NENA tropospheric O 3 budget are computed through analyses of O 3 laminae (Pierce and Grant, 1998; Teitelbaum et al., 1996), tracers (potential vorticity, water vapor), and trajectories. The lasting influence of stratospheric incursions into the troposphere is demonstrated, and the computed stratospheric contribution to tropospheric column O 3 over the R/V Ronald H. Brown and six sites in Michigan, Virginia, Maryland, Rhode Island, and Nova Scotia, 23% ± 3%, is similar to summertime budgets derived from European O 3 profiles (Collette and Ancellet, 2005). Analysis of potential vorticity, Wallops ozonesondes (37.9°N, 75.5°W), and Measurements of Ozone by Airbus In‐service Aircraft (MOZAIC) O 3 profiles for NENA airports in June‐July‐August 1996–2004 shows that the stratospheric fraction in 2004 may be typical. Boundary layer O 3 at Wallops and northeast U.S. sites during IONS also resembled O 3 climatology (June‐July‐August 1996–2003). However, statistical classification of Wallops O 3 profiles shows the frequency of profiles with background, nonpolluted boundary layer O 3 was greater than normal during IONS.