12.6
The role of Indian and Pacific Ocean SSTs in African rainfall variability
Richard Washington, University of Oxford, Oxford, Oxon, United Kingdom; and A. Preston and M. C. Todd
The CLIVAR Africa Implementation Plan identified the need to assess the association between extreme rainfall events in Africa and variability in the Indian Ocean which is not related to ENSO. In this paper we undertake both observational and modelling work aimed at clarifying the competing roles of Indian and Pacific Ocean SSTs. In the observational component, we remove ENSO signals from all data to establish global and local-scale teleconnection patterns associated with observed southern African summer (JFM) rainfall variability. The strongest teleconnections are in the Indian Ocean and take the form of an SST warm and cold pools and associated pressure systems in the central and southern regions of the basin. These patterns are distinct from the much debated Indian Ocean Dipole. In order to get to the crux of the dynamical mechanisms surrounding these teleconnections, the second stage of research has centred on running a series of idealised experiments using the atmosphere-only (HadAM3) component of the UKMO Unified Model. These experiments have included Indian Ocean only, Pacific Ocean only and combined SST forcings. Results reinforce the importance of the Indian Ocean SST patterns in affecting southern African rainfall variability and indicate that the atmosphere dynamics are highly sensitive to the location of the SST warm and cold pools.
Session 12, Regional Issues: Africa
Wednesday, 26 March 2003, 1:30 PM-5:15 PM
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