Abstract
Accurate simulations of the coupling between radiation, clouds and the circulation in general circulation models (GCMs) play an important role in governing the frequency and intensity of convection and the hydrological cycle. We investigate radiative feedbacks associated with the Madden-Julian Oscillation (MJO) using radiative kernels. We find that changes in clouds, compared to those in temperature, water vapor and albedo, induce the largest radiative perturbations during active phases of the MJO. Strong radiative heating helps the MJO survive the barrier effect of the Maritime Continent. To examine how radiation affects the development of organized convective systems under realistic boundary conditions, a series of mechanism-denial experiments are conducted in a high-resolution GCM where synoptic-scale interactions between radiation and convection are disabled. When radiative interactions are suppressed, the global TC frequency is reduced, which is primarily due to a decrease in the frequency of pre-TC synoptic disturbances, whereas the likelihood that the disturbances undergo cyclogenesis is less affected. TC duration is also reduced because TC genesis locations are shifting toward coastal regions when radiative interactions are suppressed. In a warmer climate, the magnitude of the reduction in TC frequency is diminished due to greater contribution from latent heat release with increased sea surface temperatures. Suppressing radiative interactions also reduces the spatial contrast in radiative cooling from dry to moist regions and thus the upgradient transport of moist static energy, resulting in a reduction in the degree of aggregation and extreme precipitation events at regional scales. Based on an ensemble of state-of-the-art GCMs, we find that the spatial patterns of future precipitation change exhibit a strong dependence on the current climate. Therefore, models can be screened using observations as a constraint to reduce the intermodel spread in projections of future climate change.