ausblenden:
Schlagwörter:
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Zusammenfassung:
Simulations of ozone loss rates using a three-dimensional chemical transport model
and a box model during recent Antarctic and Arctic winters are compared with
experimental loss rates. The study focused on the Antarctic winter 2003, during which the
first Antarctic Match campaign was organized, and on Arctic winters 1999/2000,
2002/2003. The maximum ozone loss rates retrieved by the Match technique for the
winters and levels studied reached 6 ppbv/sunlit hour and both types of simulations could
generally reproduce the observations at 2-sigma error bar level. In some cases, for
example, for the Arctic winter 2002/2003 at 475 K level, an excellent agreement within
1-sigma standard deviation level was obtained. An overestimation was also found with the
box model simulation at some isentropic levels for the Antarctic winter and the Arctic
winter 1999/2000, indicating an overestimation of chlorine activation in the model. Loss
rates in the Antarctic show signs of saturation in September, which have to be considered
in the comparison. Sensitivity tests were performed with the box model in order to
assess the impact of kinetic parameters of the ClO-Cl2O2 catalytic cycle and total bromine
content on the ozone loss rate. These tests resulted in a maximum change in ozone loss
rates of 1.2 ppbv/sunlit hour, generally in high solar zenith angle conditions. In some
cases, a better agreement was achieved with fastest photolysis of Cl2O2 and additional
source of total inorganic bromine but at the expense of overestimation of smaller ozone
loss rates derived later in the winter.
