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Extreme rainfall events in West Africa, often linked to Mesoscale Convective Systems (MCSs), cause recurrent floods and socio-economic damage. This study investigates the morphology, dynamic and thermodynamic properties of MCSs associated with extreme rainfall in West Africa. Four key features are analyzed: system area, cloud-top temperature (CTT), translation speed, and desert dust aerosol loading. MCSs were detected and tracked using the Tracking Algorithm for Mesoscale Convective Systems (TAMS). Thermal infrared imagery from the 10.8 µm channel of the SEVIRI onboard MSG provided cloud properties, while rainfall estimates were obtained from the IMERG. Dust AOD within tracked systems was extracted from the CAMS reanalysis. Exploratory statistical analyses (ESA) were applied to assess how these properties distinguish extreme events from climatological baselines and to identify the mechanisms enhancing rainfall efficiency. The results reveal marked contrasts across MCS types. Mesoscale Convective Complexes (MCCs), though least frequent, generate the highest rainfall intensities (up to 24 mm/h) and exhibit the widest variability, emphasizing the importance of structural organization. Disorganized Long-Lived (DLLs) systems dominate extreme event frequency but with lower variability, while Convective Cloud Clusters (CCCs) occupy an intermediate position. Extreme events are systematically associated with smaller and more compact cloud shields (up to 30% below climatology) and reduced translation speeds, indicating that persistence and confinement enhance rainfall efficiency. By contrast, CTT differences between extremes and climatology are minimal, suggesting a limited role in driving rainfall extremes. Finally, dust concentrations are consistently lower during extremes, with median AOD reduced by 37–52% depending on system type, supporting the hypothesis that extreme rainfall preferentially develops under reduced aerosol loading. These findings highlight the combined importance of system organization, persistence, and environmental aerosol conditions in modulating extreme rainfall from West African MCSs.

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Characterizing the Morphology and Thermodynamics of Mesoscale Convective Systems Driving Extreme Rainfall in West Africa

  • 会议论文

  • 发表日期：

    2026年

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  • Dame Gueye,
  • Abdou Lahat Dieng,
  • Kelly M. Núñez Ocasio,
  • Zachary L. Moon,
  • Abdoulaye Deme,
  • Mamadou Sarr,
  • Semou Diouf,
  • Abdou Aziz Coly,
  • Papa Fall,
  • Mamadou Thiam

摘要

Extreme rainfall events in West Africa, often linked to Mesoscale Convective Systems (MCSs), cause recurrent floods and socio-economic damage. This study investigates the morphology, dynamic and thermodynamic properties of MCSs associated with extreme rainfall in West Africa. Four key features are analyzed: system area, cloud-top temperature (CTT), translation speed, and desert dust aerosol loading. MCSs were detected and tracked using the Tracking Algorithm for Mesoscale Convective Systems (TAMS). Thermal infrared imagery from the 10.8 µm channel of the SEVIRI onboard MSG provided cloud properties, while rainfall estimates were obtained from the IMERG. Dust AOD within tracked systems was extracted from the CAMS reanalysis. Exploratory statistical analyses (ESA) were applied to assess how these properties distinguish extreme events from climatological baselines and to identify the mechanisms enhancing rainfall efficiency. The results reveal marked contrasts across MCS types. Mesoscale Convective Complexes (MCCs), though least frequent, generate the highest rainfall intensities (up to 24 mm/h) and exhibit the widest variability, emphasizing the importance of structural organization. Disorganized Long-Lived (DLLs) systems dominate extreme event frequency but with lower variability, while Convective Cloud Clusters (CCCs) occupy an intermediate position. Extreme events are systematically associated with smaller and more compact cloud shields (up to 30% below climatology) and reduced translation speeds, indicating that persistence and confinement enhance rainfall efficiency. By contrast, CTT differences between extremes and climatology are minimal, suggesting a limited role in driving rainfall extremes. Finally, dust concentrations are consistently lower during extremes, with median AOD reduced by 37–52% depending on system type, supporting the hypothesis that extreme rainfall preferentially develops under reduced aerosol loading. These findings highlight the combined importance of system organization, persistence, and environmental aerosol conditions in modulating extreme rainfall from West African MCSs.