The influence of convective adjustment time scale (τ) in simulating the tropical transient activity is examined using the NCAR-Community Atmosphere Model (CAM). 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). EXPT produces more reasonable ISV, with prominent, coherent, and organized eastward propagation. The active phases of the ISV constitute hierarchical substructures embedded within them, which are absent in CTRL. The Kelvin waves become slow, Madden-Julian oscillation (MJO) become energetic, n = 1 equatorial Rossby (ER) and n = 0 eastward inertio-gravity (EIG) waves become prominent, with the increase of τ. On the contrary, the mixed Rossby-gravity (MRG) waves at higher wavenumber regimes become weak. The amplitude of diurnal variability decreases, but the phase remains largely unchanged. At sub-diurnal scales, the variability of precipitation increases. In CTRL, precipitation always occurs in the tropics with light or moderate intensity, which becomes intermittent when s is increased to 8 h.
