Joubert, A. M., 1997: Simulations by the Atmospheric Model
Intercomparison Project of atmospheric circulation over southern Africa.
International Journal of Climatology, 17, 1129-1154.
Seven simulations by the Atmospheric Model Intercomparison Project
(AMIP) of mean climate and interannual variability over southern Africa
during the 1979-1988 decade are evaluated. The focus of the study is the
representation in the models of both regional and hemispheric circulation
features which influence the climate of the subcontinent. The AMIP integrations
provide an improved simulation of mean circulation around southern Africa
when compared with earlier atmospheric general circulation models. Improvements
are noted in the representation of the position and intensity of the subtropical
anticyclones, the circumpolar trough and the strength of the mid-latitude
westerlies. The representation of tropospheric circulation features throughout
the Southern Hemisphere, including zonal asymmetries and planetary wave
I at 500 hPa, appear to be dependent on the spatial resolution of the models.
No single model simulates all features of southern African circulation
accurately, and model performance varies with the seasons.
Several of the AMIP models are capable of simulating the observed features
of interannual variability in circulation over southern Africa. Simulated
interannual variability in both summer rainfall and circulation is weaker
than observed. Simulated circulation adjustments in the subtropics and
mid-latitudes are in good agreement with observed adjustments associated
with periods of above and below average summer rainfall over the subcontinent.
It is recognized that considerable uncertainty is associated with the single
integrations using observed sea-surface temperature forcing considered
in the present analysis. Ensemble approaches are required to provide a
more comprehensive assessment of the simulated response to imposed forcing.