| 25 Aug 2025
Understanding mesoscale convective processes over the Congo Basin using the Model for Prediction Across Scales-Atmosphere (MPAS-A)
Abstract. The Congo Basin in Central Africa is one of three convective centers in the tropics, characterized by a high proportion of precipitation produced by mesoscale convective systems (MCSs). However, process-level understanding of these systems and their relationship to environmental factors over the Congo Basin remains unclear, largely due to scarce in-situ observations. This study employs the Model for Prediction Across Scales–Atmosphere (MPAS-A), a global cloud-resolving model, to investigate MCSs in this region. Compared to satellite-observed brightness temperature (Tb), MPAS-A realistically simulates key MCS features, allowing a detailed comparison between two mesoscale convective complex (MCC) cases: one over the southern mountainous region (MCC-south) and the other over the northern lowland forests (MCC-north). MCC-south is larger, longer-lived, and moves a longer distance than MCC-north. Our analysis shows that MCC-south is supported by higher thermodynamic energy and more favorable vertical wind shear ahead of the system. The shear extends up to 400 km, explains up to 65 % of the Tb variance, and is well balanced by a moderately strong cold pool. In contrast, MCC-north features weaker, localized shear near the center and a stronger cold pool. The African Easterly Jet helps maintain the shear in both cases, but an overly strong jet may suppress low-level westerlies and weaken convection. These results show how latitude and topography modulate environmental influences on Congo Basin MCS developments. The findings underscore the value of global cloud-resolving models in data-sparse regions for understanding convective systems and their impacts on weather extremes and societal risks.
This study titled "Understanding mesoscale convective processes over the Congo Basin using the Model for Prediction Across Scales-Atmosphere (MPAS-A)" addresses the lack of in-situ observations by utilizing a global cloud-resolving model to investigate MCSs. I feel this paper is a proof-of-concept for future research work. The research aims to improve the process-level understanding of these systems and their relationship to environmental factors, which are responsible for a significant portion of the region's precipitation.
The study compares two specific mesoscale convective complex (MCC) cases: one over the southern mountainous region (MCC-south) and another over the northern lowland forests (MCC-north). The findings indicate that while both are influenced by the African Easterly Jet, they differ in their dynamics. The MCC-south case is larger, more persistent, and is driven by higher thermodynamic energy and a strong vertical wind shear extending up to 400 km ahead of the system. This shear is well-balanced by a moderately strong cold pool and accounts for a significant portion of the observed brightness temperature variance. In contrast, the MCC-north case is characterized by weaker, localized shear and a stronger cold pool.
In conclusion, the research demonstrates that both latitude and topography play a crucial role in modulating the environmental conditions that influence the development of MCSs in the Congo Basin. The findings highlight the efficacy of using high-resolution global models like MPAS-A to study convective systems in data-sparse regions, offering valuable insights into their impact on extreme weather and societal risks. Based on the paper's findings and the model's capabilities, MPAS-A is a powerful tool for a variety of atmospheric research experiments. Its ability to handle both high-resolution regional and lower-resolution global scales within a single framework makes it particularly versatile. In the future, I would like to see new research insights by incorporating a future climate state (e.g., initialize the model using present and future climate and understand how results differ from those derived using IMPALA data), perturbation experiments to better understand orographic, dynamic and thermodynamic processes, and diurnal cycle (e.g., Alber et al https://doi.org/10.1016/j.atmosres.2021.105869). The opportunities for high spatio-temporal process-based research work over Africa is quite limitless.
Great to see this paper finally out and my best wishes to the research team.
Minor comments: Line 97-99: Why is this paragraph italicized?
Figure 1a: Can you replace this figure with something better such as a variable resolution MPAS Voronoi mesh version (e.g., https://mpas-dev.github.io/atmosphere/atmosphere.html) .
Figure 2: The figure caption for Figure 2 can be re-worded for better clarity.