Long-range convective ozone transport during INTEX



[1] Ozone transport across the tropopause near a convective region in the central Pacific is calculated for a 1-day period using a nested grid, high-resolution simulation with the University of Wisconsin Nonhydrostatic Modeling System (UWNMS). This ozone is then tracked into the region where DC-8 lidar ozone observations on 6 July 2004 were taken over the United States during the Intercontinental Chemical Transport Experiment-North America (INTEX-NA). On 2 July a convective complex developed north of the Midway Islands and intensified as it propagated eastward. Satellite observations captured this event well, and the UWNMS simulation placed the convection just east of an upper level trough along the subtropical jet. The proximity of the strong convection to the lowered tropopause resulted in significant stratospheric ozone contribution (SOC) to the troposphere. During the 24 h period starting at 1200 UTC 2 July, total net ozone flux into the troposphere was calculated to be about 0.2 Tg across the nested grid domain. Because the convective outflow was feeding the subtropical jet, the SOC was quickly transported across the eastern Pacific and into the INTEX-NA region. Using an “SOC tracer” we show that a small but significant percentage of observed ozone on the DC8 flight can be attributed to SOC from this one convective event. This supports the idea that the stratosphere over the Pacific is an important source of ozone for air entering North America from the west.