Use of coupled ozone fields in a 3-D circulation model of the middle atmosphere

Abstract

Abstract. With a detailed chemistry scheme for the middle atmosphere up to 70 km which has been added to the 3-D Karlsruhe simulation model of the middle atmosphere (KASIMA), the eects of coupling chemistry and dynamics through ozone are studied for the middle atmosphere. An uncoupled version using an ozone climatology for determining heating rates and a coupled version using on-line ozone are compared in a 10-month integration with meteorological analyses for the winter 1992/93 as the lower boundary condition. Both versions simulate the meteorological situation satisfactorily, but exhibit a too cold lower stratosphere. The on-line ozone diers from the climatological data between 20 and 40 km by exhibiting too high ozone values, whereas in the lower mesosphere the ozone values are too low. The coupled model version is stable and diers only above 40 km signi®cantly from the uncoupled version. Direct heating eects are identi®ed to cause most of the dierences. The well-known negative correlation between temperature and ozone is reproduced in the model. As a result, the coupled version slightly approaches the climatological ozone ®eld. Further feedback eects are studied by using the on-line ozone ®eld as a basis for an arti®cial climatology. For non-disturbed ozone conditions realistic monthly and zonally averaged ozone data are sucient to determine the heating rates for modelling the middle atmosphere.

Sensitivity of climate to dynamically‐consistent zonal asymmetries in ozone

“…As in the Southern Hemisphere, the phase relationship between the ozone anomaly and the temperature response varies with month and pressure level. Reddmann et al [1999] find only a small temperature response to zonal asymmetries in ozone in the Northern Hemisphere at 2 hPa on December 30th, and conclude that the response to zonal asymmetries in ozone is weak. We find no significant temperature response over the Arctic at this level and time (Figure 3d), but we find a significant temperature response at 2 hPa earlier in the year, and at other levels in December.…”

“…Another simpler approach is to simply use daytime mean values of ozone in the mesosphere. This would, for example, parallel the approach followed by Reddmann et al [1999], where daytime mean values of ozone were specified above 50 km. One drawback of this approach, however, is that the nighttime long‐wave terrestrial radiation sees the low daytime ozone concentrations and this could lead to a bias.…”

“…One way in which the influence of zonal asymmetries in ozone may be examined in a more realistic context is by comparing a simulation of a coupled chemistry model, with a second simulation in which the zonal mean of the calculated ozone is prescribed. Reddmann et al [1999] carried out such a comparison using the 3‐D Karlsruhe simulation model of the middle atmosphere (KASIMA), accounting for the diurnal cycle in ozone above 50 km by prescribing the daytime mean ozone above this level in the second simulation, and with conditions at the 10‐km lower boundary prescribed from European Centre for Medium Range Weather Forecasting (ECMWF) analyses. Their simulations start in July, meaning that they are not able to realistically simulate the Antarctic winter vortex or Antarctic ozone depletion.…”

Total hydrogen mixing ratio anomaly around the mesopause region

“…Different global 2‐D or 3‐D models designed to model the stratosphere/mesosphere have their upper border just around the mesopause/turbopause meaning, within (or slightly above) the most sensitive region of the atmosphere [e.g., Garcia and Solomon , 1983; Smith and Brasseur , 1991; Bacmeister et al , 1995; Summers et al , 1997; Reddmann et al , 1999]. Hence it is important to know the relations at the upper border.…”

Modeling disturbed stratospheric chemistry during solar‐induced NOx enhancements observed with MIPAS/ENVISAT

“…A detailed description of the model is given by Kouker et al [1999a]. The model has been previously used for investigations of stratospheric transport and chemistry [ Kouker , 1993; Reddmann et al , 1999; Ruhnke et al , 1999; Kouker et al , 1999b; Reddmann et al , 2001].…”