Previous evaluations of the impact of fluorine chemistry on stratospheric ozone have concluded that the role of fluorine compounds in catalytic ozone removal is negligible. However, recent investigations of the degradation pathways for compounds containing CF3 groups indicates that if the reaction of CF3O with O3 is sufficiently fast, there may be an ozone impact. Some recent measurements indicate that the reaction rate constant of CF3O+O3 is sufficiently low that the ozone impact is likely to be small. However, it is not possible a‐priori to rule out significant ozone removal without additional kinetic data on other reactions. We present calculations to illustrate how different key reactions affect the calculated stratospheric concentrations of the CF3X species (CF3, CF3O, CF3O2, CF3OH, CF3OOH, CF3ONO2, CF3O2NO2, CF3OOCl) and their ability to remove stratospheric ozone. We utilize our results to suggest kinetic measurements that could substantially reduce the uncertainties in CF3 chemistry relevant to the determination of ozone depletion potential of CF3‐bearing compounds.
Increases in aerosol loading after the Pinatubo eruption are expected to cause additional ozone depletion. Even though aerosol loadings were highest in the winter of 1991–1992, recent analyses of satellite and ground‐based ozone measurements indicate that ozone levels in the winter of 1992–1993 are the lowest recorded in recent years, raising the question of the mechanisms responsible for such behavior. We have incorporated aerosol surface areas derived from the Stratospheric Aerosol and Gas Experiment II (SAGE‐II) measurements into our two‐dimensional model. Inclusion of heterogeneous chemistry on these enhanced aerosol surfaces yields maximum ozone reductions during the winter of 1992–1993 in the Northern Hemisphere, consistent with those derived from observations. This delayed behavior is due to the combination of the non‐linear nature of the impact of heterogeneous reactions as a function of aerosol surface area, and the long time constants for ozone in the lower stratosphere. If heterogeneous mechanisms are primarily responsible for the low 1992–1993 ozone levels, we expect ozone concentrations to start recovering in 1994.
This paper outlines an architecture that provides data and software services to enable a set of Unmanned Aircraft (UA) platforms to operate in a wide range of air domains which may include terminal, en route, oceanic and tactical. The architecture allows a collection of command, control, situational awareness, conflict detection and avoidance, and data management elements to be composed in order to meet different requirement sets as defined by specific UA plat-
The deposition altitude of nitrogen oxides and other exhaust species emitted by stratospheric aircraft is a crucial parameter in determining the impact of these emissions on stratospheric ozone. We have utilized a model for the wake of a High‐Speed Civil Transport (HSCT) to estimate the enhancements in water and reductions in ozone in these wakes as a function of time. Radiative calculations indicate differential cooling rates as large as −5K/day at the beginning of the far‐wake regime, mostly due to the enhanced water abundance. These cooling rates would imply a net sinking of the wakes of about 1.2 km after three days in the limit of no mixing. Calculated mid‐latitude column ozone reductions due to emissions from a Mach 2.4 HSCT would then change from about −1% to −0.6%. However, more realistic calculations adopting moderate mixing for the wake reduce the net sinking to less than 0.2 km, making the impact of radiative subsidence negligible.
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