Friday, 3 May 2002: 11:30 AM
Intraseasonal variability over tropical Africa
Coherent patterns of intraseasonal variability in deep convection over
tropical Africa are presented, based on an EOF analysis of 25 years of
satellite-measured outgoing longwave radiation data as a proxy for
deep convection. The first mode represents a strengthening of the
West African monsoon convection. It has an associated global
structure and appears to be a remote response to northward-propagating
intraseasonal anomalies over the Indian and western Pacific sectors -
the northern summer counterpart of the Madden-Julian oscillation. The
second mode describes an east-west dipole in convection over Africa.
Enhanced convection over West Africa is preceeded by eastward
propagation of enhanced convective anomalies from the tropical
Atlantic. Reduced convection over East Africa is preceeded by
westward propagation from the Indian Ocean, which again is part of the
dominant mode of intraseasonal variability over the Indian-western
Pacific sector. Patterns of African intraseasonal variability will
also be presented for northern winter and underlying physical
mechanisms will be discussed.
Supplementary URL: http://envam1.env.uea.ac.uk/~e058/amstropmet2002.pdf