Fast-Response (4 Hz) In Situ Ozone Measurements by a UV Absorption Photometer on the WB-57F During ACCENT

The ACCENT (Atmospheric Chemistry of Combustion Emissions Near the Tropopause) campaign was a multi-agency investigation of the chemistry and dynamics of rocket and aircraft emissions in the upper troposphere (UT) and lower stratosphere (LS). The mission utilized the NASA WB-57F aircraft as the platform for a multi-investigator suite of measurement instrumentation for a wide variety of gas-phase and particulate species in the UT/LS. As part of this mission, the PSI UV Ozone Photometer obtained in situ ozone data at measurement frequencies of 1 and 4 Hz. Operation at 4 Hz on board the WB-57F produced ozone measurements with spatial resolutions near 50 m. These data can be used to investigate fine-scale ozone variability and mixing scales in the normal upper atmosphere and across sharp boundaries as observed in ozone-depleted rocket exhaust plumes. Fast-response ozone data were obtained in flights over Hurricane Floyd and into the ITCZ, as well as in encounters with exhaust plumes from an Athena solid-fueled rocket and from the Space Shuttle, both near 18 km altitude. In the rocket plume measurements, the data show well-defined regions containing near-zero ozone concentrations, which persist and expand for 0.5 to 1.5 hr after passage of the rocket. In addition, the data exhibit considerable spatial structure within the ozone-depleted regions that indicates a high degree of dynamic complexity in the intercepted plume segments. We will present an overview of the fast-response ozone data base, and will discuss chemical kinetic and dynamic implications of the rocket plume measurements. This research was supported by NASA and by the Air Force Office of Scientific Research.