Influence of convective adjustment time scale on the tropical transient activity

In the default configuration of the model, the prescribed value of τ, a characteristic time scale with which convective available potential energy (CAPE) is removed at an exponential rate by convection, is assumed to be 1 h. However, some recent observational findings suggest that it is larger by around one order of magnitude, and subsequent modeling studies showed its impact on mean climate and suggest a value of 8 h.

To see if alteration of this time scale could affect the transient features of climate, numerical experiments are conducted in aquaplanet and real-planet frameworks. The analysis includes the tropical intraseasonal variability (ISV), convectively coupled equatorial waves (CCEW), diurnal and sub-diurnal variability of precipitation, and intensity and frequency of rainfall. Two sets of simulations are conducted: one with a time scale of 1 h (CTRL) and another with 8 h (EXPT).