A sensitivity study of radiative-convective equilibrium in the tropics with a convection-resolving model

Statistical-equilibrium (SE) states of radiative-convective systems in trop ical oceanic conditions are simulated with a cloud ensemble model (CEM) in this study. Typical large-scale conditions from the Marshall Islands and th e eastern tropical Atlantic regions are used to drive the CEM. The simulated SE precipitable water, column temperature, and relative humid ity are only slightly higher than those of the observed mean states in both regions when time-invariant large-scale total advective cooling and moiste ning effects are imposed from observations. They are much higher than the o bserved if time-invariant observed large-scale ascent is imposed for the Ma rshall Islands region (i.e., ignoring horizontal advective effects). Compar ed with results from two similar studies, this SE state is somewhere betwee n the cold/dry regime by Sui et al. and the warm/humid regime by Grabowski et ar. Temporal variations of the imposed large-scale vertical motion that arrows for subsidence make the SE state colder and drier. It remains about the same, however, if the magnitude of the imposed large scale vertical mot ion is halved. The SE state is also colder and drier if solar radiation is absent. In general, all the SE states shaw that wet columns are thermally m ore stable (unstable) and dry columns are thermally more unstable (stable) in the lower (upper) troposphere. Column budget analyses are performed to explore the differences among the s imulations performed in this study and among the different studies.