The hydrological cycle over a wide range of climates in an idealized GCM

To explore how mean precipitation changes in different climates, we have simulated a wide range of climates with a diverse set of hydrological cycles using an idealized general circulation model (GCM). While the idealized GCM does not capture the full complexity of the hydrological cycle, the range of climates simulated allows the testing and development of theories of how water vapor transport and mean precipitation behave in altered climates. Energy constraints are shown to be useful in understanding the behavior of the global average precipitation, and a stochastic model is used to examine the behavior of the precipitation from large-scale condensation. The poleward eddy moisture flux is a function of the eddy kinetic energy and the specific humidity in the Tropics, but the local balance between changes in moisture transport and evaporation is not straightforward, with implications for the subtropical precipitation. In general, the simulations suggest that different responses of the hydrological cycle to climate forcing perturbations can be expected in different climate regimes.