HR: 14:00h
AN: A33B-03    [Abstracts]
TI: Interannual Climate Variability in the South Atlantic: Linking Tropics and Subtropics.
AU: * Trzaska, S
EM: syl@iri.columbia.edu
AF: International Research Institute for Climate Prediction (IRI), 61 Rt. 9W, PO Box 1000, Palisades, NY 10964-8000 United States
AU: Robertson, A W
EM: awr@iri.columbia.edu
AF: International Research Institute for Climate Prediction (IRI), 61 Rt. 9W, PO Box 1000, Palisades, NY 10964-8000 United States
AU: Farrara, J D
EM: jfarrara@ucla.edu
AF: Department of Atmospheric Sciences, University of California, Los Angeles (UCLA), 405 Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AU: Mechoso, C R
EM: mechoso@atmos.ucla.edu
AF: Department of Atmospheric Sciences, University of California, Los Angeles (UCLA), 405 Hilgard Avenue, Los Angeles, CA 90095-1565 United States
AB: Climate variability in the tropical Atlantic is of capital importance for climate in the adjacent semi-arid regions of North Eastern Brazil, Sahel and Southern Africa. Standard multivariate analyses have isolated the dominant patterns of variability in the region, related or not to ENSO, but most of the studies have considered the tropics and the sub-extratropics separately. Moreover, most of the studies focused on the interannual and decadal time scales, the latter explaining a large part of the total variability in the Atlantic. However, despite the differences between the regions, climate variability in the South Atlantic is linked to the variability of the intensity and location of the subtropical High. This work focuses on the dominant modes of variability common to the tropical and subtropical parts of the South Atlantic and their specific time scales. Special focus is put on interannual time scales and variability not related to ENSO. The dominant modes are reproduced by the UCLA AGCM coupled to a simple, constant depth, oceanic mixed layer in the Atlantic. In both, the observations and the model, the interannual variability in the South Atlantic is dominated by two separate times scales. The longer, ca. 5 years, seems to arise from interhemispheric interactions in the Atlantic while the shorter, quasi-biennial, is characteristic of the South Atlantic itself. Its main feature is an apparent anticlockwise propagation of the anomalies within the South Atlantic basin, from the subtropics in boreal spring to the tropical and equatorial regions in boreal summer. It provides a useful link between the modes of variability identified separately in the tropics and the subtropics and in different seasons. The agreement between simulated and observed spatio-temporal characteristics provides a potential for short term seasonal predictability of the South Atlantic SST. Such predictability, based on air-sea thermodynamical interactions, links between tropics and subtropics and recognition of the different time scales is further explored in this work.
DE: 3309 Climatology (1620)
DE: 3319 General circulation
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4215 Climate and interannual variability (3309)
DE: 9325 Atlantic Ocean
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly