Quantifying Precipitation Efficiency in Tropical Mesoscale Convective Systems: Insights from Global Cloud-Resolving Models and IMERGE Observations
Thabo E. Makgoale1 and Sylvia Sullivan1,2
1Department of Hydrology and Atmospheric Sciences, University of Arizona, United States of America.
2 Department of Chemical and Environmental Engineering, University of Arizona, United States of America.
Tropical deep moist convection frequently organizes into mesoscale convective systems (MCSs), coherent structures that extend beyond the scale of individual thunderstorms and persist for hours to days. These systems are a primary contributor to accumulated tropical precipitation and are closely linked to extreme rainfall events and severe wind occurrences. Despite their significant impact, current models continue to face challenges in accurately simulating convective precipitation associated with MCSs, largely due to the wide range of spatial and temporal scales involved. Recent advances in computational power have enabled the development of global cloud-resolving models (GCRMs) that operate at considerably finer grid resolutions than traditional global climate models (GCMs). In a recent study (Makgoale and Sullivan, 2024, in review), precipitation efficiency (ε) – defined as the fraction of atmospheric condensate that reaches the surface as precipitation was characterized using GCRMs, revealing substantial inter-model variability in both magnitude and spatial distribution. Notably, phase-partitioned analyses of ε indicate pronounced differences during intense rainfall events, particularly over the Bay of Bengal, where MCS activity and concurrent convective precipitation are prevalent. To further investigate this link, we compute and characterize the precipitation efficiency of MCSs by integrating existing GCRM simulations with IMERG observations and FLEXTRKR tracking data. This approach aims to advance our understanding of the spatial and temporal variations in ε and to clarify the role of MCSs in modulating precipitation processes in the tropics.