HR: 16:50h
AN: A54A-03    [Abstracts]
TI: The Relationship Between The Indian Ocean Dipole And The Observed Precipitation On The Onset Of The South American Monsoon System: A Correlation Analysis
AU: Drumond, A
EM: anitadru@model.iag.usp.br
AF: Department of Atmospheric Sciences - USP, Rua do Matao, 1226, Sao Paulo, SP 05508- 090, Brazil
AU: * Ambrizzi, T
EM: ambrizzi@model.iag.usp.br
AB: The relationship between the Indian Ocean Dipole (IOD) and the South American precipitation anomalies observed during the Brazilian pre-rainy season (austral spring) is analyzed through a linear correlation analysis. The IOD can be represented by the Dipole Mode Index (DMI), defined as the difference between the normalized sea surface temperature (SST) anomalies observed in the western Indian Ocean (60°-80°E, 10°S-10°N) and in the eastern side of this basin (90°-110°E, 10°S- 0°). In this way, warmer SST in the western Indian and colder in the eastern Indian define a positive DMI and are observed during positive IOD events. The opposite characteristics occur during the negative IOD episodes. The analysis is made for the period between 1950 and 2003 and correlations between the DMI and precipitation anomalies time series are elaborated in a seasonal and monthly scale. Negative correlations in the northeastern Brazil and positive over the southeastern South America were found for the austral spring. This result implies that during positive IOD events enhanced precipitation over the subtropics and drought conditions over northeastern Brazil may occur. In a monthly analysis, this dipolar structure is more evident during October and November while there are not statistically significant correlations over the continent in September. In October, negative correlations occur in some parts of southeastern Brazil while positive is observed over the southeastern South America. This dipolar structure is displaced northward during November when negative correlations over northeastern Brazil and positive over the Parana Brazilian State are observed. A lag correlation analysis suggest that the SST anomalies observed in the Indian Ocean since July has some relationship with the precipitation anomalies observed in the continent during October and November. In order to explain the dynamical aspects between the IOD episodes and the South American climate, numerical experiments with a general circulation model are being carried out and they will be presented elsewhere.
DE: 3300 ATMOSPHERIC PROCESSES
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly