Precipitation on the Manus Island of Papua New Guinea and ice cloud radiative effects in the surrounding atmosphere in boreal winters

The longwave cloud radiative effect (LW CRE) plays a critical role in regulating tropical moist convection by modifying the atmospheric energy budget. While previous studies have linked LW CRE to the maintenance of convective quasi-equilibrium (CQE) on large scales, its influence at shorter timescales and on individual convective events remains less explored. In this study, we analyze the relationship between precipitation and LW CRE on daily timescales at a location over the equatorial western Pacific. We focus on how LW CRE shapes the thermodynamic environment prior to deep convection. The present results show that enhanced LW CRE and surface turbulent heat fluxes act to increase atmospheric moist static energy (MSE) before
rainfall events, supporting conditions favorable for deep convection. Notably, LW CRE may facilitate ice sublimation in the lower portions of ice clouds by enhancing radiative warming, thereby contributing to the preconditioning of the atmospheric column. In addition, increased humidity in the lower free troposphere above the planetary boundary layer (PBL) is found to reduce the height of anvil cloud tops, suggesting a modulation of convective vertical structure by pre-convective moisture. These findings provide a process-level perspective on how LW CRE contributes to maintaining a quasi-equilibrium convective state in the tropics.