A Framework to Evaluate Convective Aggregation: Examples with Different
Microphysics Schemes
Abstract
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.