A tale of two summers (2004, 2005): Ozone soundings in the Mid-Atlantic region

Ozone soundings serve to integrate models, aircraft and ground-based measurements for better interpretation of atmospheric pollution. An important feature of sonde data is having ozone partial pressures (with P-T-U from radiosondes and winds, if available) at 5-10 m resolution from the surface to 10 hPa. Ozonesonde data at Wallops Island, Virginia (37.9 N, 75.5W) have been taken weekly since the 1960's and were augmented with additional launches in July-August 2004 as part of the IONS (INTEX Ozonesonde Network Study; ) project. Also in 2004, as part of IONS, summertime soundings were initiated at the Howard University Beltsville Research Facility (Maryland; 39.0N, 76.5 W). The general features of tropospheric ozone in July and August 2004 at the two sites included relatively low ozone in the lower troposphere compared to Wallops climatology. In addition, in 2004 Maryland had only one ozone NAAQS air quality violation. In mid-August 2005, a classic high- pressure stagnation period led to a Code Red situation and very high ozone over Beltsville. In addition, the influence of the nighttime low-level jet on pollution was characterized through an enhanced sampling schedule during 12-14 August 2005.