Abstract

Knowledge of the spatial and temporal variability of precipitation is needed for African societies to manage agriculture, water resources, public health, renewable energy, and hazard mitigation. This study examines the occurrences of organized convection in Africa using five years (1999-2003) of ... Show moreKnowledge of the spatial and temporal variability of precipitation is needed for African societies to manage agriculture, water resources, public health, renewable energy, and hazard mitigation. This study examines the occurrences of organized convection in Africa using five years (1999-2003) of digital infrared imagery. Domains are: 0° to 20°N and 20°W to 40°E; 15°S to 15°N and 20°W to 45°E; 35°S to 15°S and 10°E to 45°E. Reduced-dimension techniques are used to document properties of cold clouds, proxies for precipitation. Large-scale environments are diagnosed from global analyses. A sizeable fraction of the rainfall in Africa results from long-lived "episodes" of deep convection. Episodes are coherent sequences of organized convection that propagate and regenerate on regional and continental scales. Most episodes have phase speeds of 10-20 m s⁻¹. A major generating factor for convection is thermal forcing associated with large elevated heat sources. Episodes occur with moderate vertical wind shear. Study results infer the potential for increased predictive skill in sub-seasonal weather prediction, which could enable substantial societal benefits. Show less