A hemispherical general circulation model has been used to study the consequences of the termination of the incoming solar radiation on the fully developed meteorological fields of the model. The subsequent decay of these fields was followed for a period of 50 d, at which stage the total kinetic energy had declined to 25% of its initial value. The decay time of the atmosphere was found to be considerably longer than previous estimates in the literature because the dissipation rates declined proportionately faster than the energy. The basis response of the model atmosphere was characterized by a rapid decline in eddy activity and a much slower rundown in the zonal mean terms. The reduction in the eddy activity occurred because the fall in the absolute temperatures in the model suppressed the energizing source for the wave. In addition, this caused the atmosphere to become baroclinically stable, the eddy processes thus being isolated from the large source of zonal available potential energy present in the model. The stratosphere was converted into a quasi-isothermal regime, but the basis zonal mean temperature and zonal wind distributions in the troposphere persisted throughout the experiment, albeit reduced in amplitude. The model retained a 'memory' of its synoptic meridional velocity distribution, which characterized the underlying baroclinic nature of the normal atmosphere, even after 50 d. Overall, the resilience of the atmosphere to this drastic change in its boundary conditions was most impressive and presumably is of importance in climatic studies.