On the importance of the Mozambique Channel for the climate of southeastern Africa

• Published in: Climate dynamics Vol. 60; no. 1-2; pp. 279 - 299
• Main Authors: Mawren, D., Blamey, R., Hermes, J., Reason, C. J. C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2023; Springer; Springer Nature B.V
• Subjects: Analysis; Annual variations; Atmospheric circulation; Biodiversity; Climate; Climatology; Convective activity; Cyclones; Dynamic meteorology; Earth and Environmental Science; Earth Sciences; Environmental aspects; Geography; Geophysics/Geodesy; Heat transport; Hurricanes; Mesoscale convective systems; Ocean circulation; Ocean-atmosphere interaction; Oceanography; Oceans; Offshore; Precipitation; Rainfall; Summer; Summer rainfall; Tracking; Tropical cyclones; Upper ocean; Africa; Madagascar; Mozambique
• ISSN: 0930-7575; 1432-0894
• DOI: 10.1007/s00382-022-06334-w

The unique geography of the Mozambique Channel largely results from the mountainous island of Madagascar, the fourth largest island in the world by area, extending 13 degrees of latitude. Madagascar, which forms the eastern boundary of the Mozambique Channel, is the only example worldwide of a large tropical island situated just offshore from a tropical-subtropical continent. The Channel has important consequences for southeastern African climate, oceanic circulation and is also a region of high biodiversity. Here, the annual cycle of the regional ocean–atmosphere interactions and circulation are synthesized to help explain some of the distinctive features of southeastern African climate, including the Mozambique Channel Trough, tropical cyclone and mesoscale convective system activity, and rainfall distributions. Upper ocean heat transport from the north into the Channel is greater than that south out of the Channel throughout the year, but particularly in March–April, so this region acts as a warm pool helping to fuel convective activity. From November to April, both Madagascar and Mozambique experience substantial shifts in the areas of maximum contribution to average rainfall from tropical cyclones. Over Mozambique, this average is impacted by the impact of relatively few very intense systems either making landfall or tracking close by in the Channel. However, on average, large areas of Mozambique receive ~ 10–30% of their summer rainfall from these systems whereas for Madagascar, the contribution is much higher (~ 30–70%). The greater frequency of intense tropical cyclones in March–April relative to the mid-summer appears related to the tropical cyclone heat potential reaching its maximum during these months.