Abstract
Twenty years of IMERG precipitation estimates are used to evaluate the contributions of mesoscale convective system (MCS) rainfall to total rainfall in the Congo Basin. Studying these systems advances our basic understanding of Congo Basin rainfall on all time scales. The seasonality of MCS rainfall in the Congo Basin follows the seasonality of total rainfall with high rainfall in spring, summer, and fall and a winter dry season in each hemisphere. In the equinoctial seasons, MCS rainfall accounts for ≥ 80% of total rainfall within 5° of the equator with the highest rainfall rates occurring along the eastern and western boundaries of the basin. In boreal summer, MCS rainfall maxima occur near the Cameroon Highlands (9°–18°E) and in boreal winter, they occur along the eastern orography (22°–28°E). The 80% percent contribution is sustained in the continental interior (15°–25°E, 5°S–5°N) throughout the year. The diurnal cycle of MCS rainfall is similar to that of total rainfall. Diurnal cycles are unimodal in the equinoctial seasons but are regionally and seasonally inhomogeneous in the solstitial seasons. Regardless of modality, MCS rainfall is highest at 15Z (1600/1700 LT) and lowest at 10Z. MCS percent contribution changes little throughout the diurnal cycle but is highest (≥ 90%) at 04Z close to the continental interior. Larger MCSs contribute their greatest percentage of MCS rainfall (83–92%) between 04Z and 07Z, while more-intensely precipitating MCSs have no seasonally or regionally consistent diurnal cycle. Seasonal and diurnal MCS rainfall maxima are associated with unstable MSE profiles in the lower troposphere. Changes in moisture drive the seasonal cycle of MSE while changes in temperature drive its diurnal cycle.
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Availability of data and material
IMERG data is freely available at https://gpm.nasa.gov/data/imerg.
Code availability
Figures for the analysis were produced using the GRaDs software freely available at http://cola.gmu.edu/grads/gadoc/gadoc.php, and using Python software freely available at https://www.python.org/.
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Acknowledgements
Support from NSF Award #26-1016-20 is gratefully acknowledged. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing database resources that have contributed to the research results reported within this paper. URL: http://www.tacc.utexas.edu. The Grid Analysis and Display System software (GrADS) developed at COLA/IGES was used for generating select figures. We also thank the reviewers for their insight in revising the manuscript.
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The research was supported by the U.S. National Science Foundation Award #26-1016-20.
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All three authors contributed to the final manuscript, and an MCS identification algorithm was provided by Edward Vizy.
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Andrews, P.C., Cook, K.H. & Vizy, E.K. Mesoscale convective systems in the Congo Basin: seasonality, regionality, and diurnal cycles. Clim Dyn 62, 609–630 (2024). https://doi.org/10.1007/s00382-023-06903-7
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DOI: https://doi.org/10.1007/s00382-023-06903-7