资源环境科技发展态势分析平台

Convective aggregation is a self-aggregation phenomenon appearing in idealized radiative-convective equilibrium simulations under constant, uniform sea surface temperature (SST). To gain an understanding of observed convective aggregation or organization, three metrics, i.e., simple convective aggregation index (SCAI), modified SCAI (MCAI), and convective organization potential (COP), are evaluated with cloud object data from CERES. MCAI is related to object sizes through a modified inter-object distance (IOD). It is found that large-size object groups are less aggregated according to SCAI but more organized according to COP, compared to small-size object groups. The opposite sensitivities to object-group size can be explained by the dominant roles of the IOD in SCAI and the sum of object radii in COP as object-group sizes increase. However, large-size object groups are slightly more aggregated than small-size ones according to MCAI. Both SCAI and MCAI increase with the number of cloud objects (N) in an object group but COP has a weak dependency on N. Further sorting by object-group total area shows that sensitivity of MCAI to object-group area agrees with that of SCAI for small-area ranges but with that of COP for large-area ranges, which is related to the weak sensitivity of the modified IOD to object-group area, as compared to that of the original IOD. Finally, the three metrics show the similar contrasts between continental and oceanic convection and the same weak sensitivity to SST. The latter suggests that self-aggregation is weaker at higher SSTs than at lower SSTs, in contrast to the findings of many simulations.