Over the past three weeks, torrential wet season rains have fallen throughout parts of south-central Africa, including Zaire, Tanzania, Mozambique, Malawi, Madagascar and adjacent waters. This image shows a rainfall accumulation map obtained using NASA's Tropical Rainfall Measurement Mission (TRMM) satellite, combined with data from other rain measuring satellites. Three weeks of rain accumulation are shown, beginning on January 1, 2003. Rainfall accumulations approach two feet in some locations, leading to serious flooding and the displacement of many people from their homes. Many areas of the tropics endure a perpetual "drought-flood seesaw" over the years and this region of Africa is no exception. These rains, while helping to break a multiple year drought, have also seriously damaged this season's crops.
The heavy rains are an extreme manifestation of the annual pattern of summer rainfall across the southern hemisphere, known as the Intertropical Convergence Zone (ITCZ). Over south central Africa, warm and humid air flowing off the Arabian Sea clashes with the hot, dry Harmattan (desert wind) blowing southward off northern Africa. Violent thunderstorm rains erupt within this atmospheric battle zone. The heavy rains shown in the image over Tanzania and neighboring countries were enhanced by mountainous terrain. The mountains force moisture-laden air from the ocean to ascend, producing more rain within clouds, then concentrate rain runoff into narrow valleys.
Other extreme rainfall events from the past year can be seen on the TRMM website (trmm.gsfc.nasa.gov).
Image courtesy of Hal Pierce, NASA Goddard Space Flight Center.