Multiscale Convective Circulations and Scale Interactions in a Global Storm-Resolving Model

Understanding the relation between large-scale ((Formula presented.) 100 km) tropical atmospheric motions and small-scale convective circulations remains a challenge, despite such multiscale interactions playing a crucial role in the dynamics of large-scale circulations. In this study, a 40-day simulation made with a global storm-resolving model at 4 km horizontal resolution is used to simultaneously characterize large- and small-scale convective circulations and examine their relationships. The large-scale motions are characterized by the area-averaged vertical mass flux profile over tropical domains of similar size to the grid scale of contemporary climate models; small-scale motions are computed as deviations of vertical mass flux from the large-scale mean. We find that the simulated large-scale circulations tend to evolve in a systematic way that bears qualitative resemblance to the canonical evolution of tropical convective systems, with large-scale regimes progressing, on average, from weak but widespread subsidence, to shallow ascent/congestus clouds, to deep convection, to top-heavy stratiform anvils, and finally returning to a suppressed state. Utilizing the moisture-space framework, we compare the composite structures of the small-scale circulations in different large-scale regimes. We find that the structure of the large-scale vertical motions strongly constrains the shape of the embedded small-scale circulations. We further identify tropical anvil clouds as mediators of deep convection's up-scale influence on changes in the large-scale circulation.