Smart balloon observations over the North Atlantic: O₃ data analysis and modeling
Loading...
Collections
Author/Creator ORCID
Date
2006-08-31
Type of Work
Department
Program
Citation of Original Publication
Mao, Huiting, Robert Talbot, Donald Troop, Randy Johnson, Steven Businger, and Anne M. Thompson. “Smart Balloon Observations over the North Atlantic: O₃ Data Analysis and Modeling.” Journal of Geophysical Research: Atmospheres 111, no. D23 (2006). https://doi.org/10.1029/2005JD006507.
Rights
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain
Public Domain
Subjects
Abstract
[1] The temporal and spatial variations of ozone (O₃) in polluted continental outflow over the North Atlantic were investigated during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) field campaign in July–August 2004. Our analysis utilized measurements of O₃ from three smart balloons traveling at 0.5–3 km altitude in combination with simulations using the MM5/SMOKE/CMAQ air quality modeling system. Model results for over and within 300 km off North America were corroborated by comparison to a suite of measurements from ground stations, ozonesondes, and the NOAA ship Ronald H. Brown cruising in the Gulf of Maine. A prominent feature of the O₃ distribution was the high mixing ratios over the North Atlantic, reaching a peak value of 171 ppbv, compared to the northeastern United States (<∼100 ppbv). The enhanced O₃ levels over ocean, mostly observed at night, appeared to be the result of four factors: (1) a supply of precursors in prevailing flow off the polluted U.S. east coast, (2) significant daytime in situ chemical production, (3) minimal depositional loss to the ocean at the balloon altitudes, and (4) small nighttime chemical loss. An important implication is that quantification of O₃ export from the United States must include estimation of downwind chemical processing in polluted air masses. Balloons 3 and 4 were launched within 18 hours of each other, and their tracks allowed examination of horizontal gradients in O₃ across distances varying from 200 to 400 km. In air masses influenced by recent outflow (<2 days) the O₃ gradient was −0.2 to 0.2 ppbv km⁻¹, while by distant source regions (>2 days) it exhibited only −0.05–0.05 ppbv km⁻¹. These same two balloons encountered Hurricane Alex at different times, but both measured O₃ mixing ratios >100 ppbv. Our model results show clearly that polluted air from the mid-Atlantic states was channeled directly into Alex's inflow region. Overall, variations in O₃ on timescales of tens of minutes to hours are attributed to its highly heterogeneous distribution in urban plumes, with variations over hours to days caused by changing source regions related to cyclonic activity.