Two cloud-resolving models (SCALE and VVM) take different pathways toward convective self-aggregation (CSA) in the radiative-convective equilibrium simulations, although they have similar domain-averaged properties. Analyses in the moisture space show that radiative cooling in the dry area mainly drives CSA in SCALE, while subsidence triggered by the convection in the moist region dominates in VVM. The change in the convective structures is found on the isentropic diagram in VVM, but this transition is unclear in SCALE. The object-based analysis provides that the convective systems with larger sizes are rare in SCALE. In contrast, large-size convective systems frequently develop in the moist region as CSA evolves in VVM. The large-size systems can efficiently drive the circulation between the dry and moist areas. The different pathways to CSA are associated with the transition of convective structures, which provides a new insight to understand CSA among cloud-resolving models based on the perspective of the mechanism.

Two cloud-resolving models (SCALE and VVM) take different pathways toward convective self-aggregation under a radiative-convective equilibrium condition, although the model setups are the same. The physical processes driving the development of self-aggregation in SCALE and VVM, respectively, correspond to the mechanisms for self-aggregation in cold and warm climate states discussed in a previous study. Analyses in the moisture space show that radiative cooling in the dry area mainly drives the aggregation in SCALE, while subsidence induced by the convection in the moist region dominates in VVM. The transition of the convective circulation from convective scale to mesoscale is found on the isentropic diagram in VVM, but this transition is unclear in SCALE. The convective clouds with larger sizes are rare in SCALE. The frequent occurrence of larger convective clouds efficiently drives self-aggregation from the moist area in VVM. These results provide a new insight to understand convective self-aggregation among models.

This study introduces a framework to evaluate convective aggregation (CA) under radiative-convective equilibrium simulations using the vector vorticity equation cloud-resolving model (VVM) coupled to a mixed-layer slab ocean. The framework introduces the competing effects between the convection-SST feedback (CSF) and the moisture-convection feedback (MCF) by modifying the initial SST gradient and the mixed layer depth. Examples of applying this framework are demonstrated by comparing simulations with different microphysics schemes. The convectional five-category scheme (VVM-Lin) and the predicted particle properties scheme (P3) are examined by the matrix formed by these two factors. A clear bifurcation of the aggregated/non-aggregated states can be identified in both sets of experiments. The change of the bifurcation between two sets of experiments suggests that the P3 experiments tend to develop CA due to the stronger MCF. The budget analysis of spatial frozen moist static energy variance is applied to quantify the stronger MCF in the P3 simulations. Convective systems in P3 simulations develop more organized structures, which enhances MCF and leads to CA. The proposed framework provides a reconciled view of the process-based evaluation of CA among cloud-resolving models that use different dynamics and physical parameterizations.

This study investigates the effects of microphysical processes on the precipitation spectrum in a strongly forced environment using a vector vorticity cloud-resolving model (VVM). Experiments are performed under imposed advective cooling and moistening with two microphysics parameterizations: predicted particle properties scheme (P3) and Lin scheme (VVM-Lin). Even though the domain-averaged precipitation is similar in two experiments, P3 exhibits stronger extreme precipitation in the spectrum compared with VVM-Lin. Changes in convective structures are responsible for such a difference. Using the isentropic analyses, we identify that in P3, stronger convective updrafts take place in the high frozen equivalent potential temperature regime where air parcels rarely reach. This is caused by the reduced melting of rimed ice particles for energic parcels. Through defining convective core clouds, the relation between the convective structure on the isentropic diagram and the extreme precipitation can be identified. The shifts toward extreme intensity in the precipitation spectrum suggest that the microphysical processes have significant impacts on the extreme precipitation by the convective core clouds. The treatment of microphysics has significant impacts on the convective structures and then alter the probability of extreme events under the strongly forced environment.