The role of the South Indian and Pacific oceans in South American monsoon variability

Author(s)

Drumond, A. R. de M. ^[1] ; Ambrizzi, T. ^[2]

Affiliation

^[1] Univ Sao Paulo, Inst Oceanog, Dept Phys Oceanog, BR-05508120 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Dept Atmospher Sci, Inst Astron Geophys & Atmospher Sci, BR-05508120 Sao Paulo - Brazil

• Document type: Journal article
• Source: THEORETICAL AND APPLIED CLIMATOLOGY; v. 94, n. 3-4, p. 125-137, NOV 2008.
• Web of Science Citations: 12

Abstract

This work has investigated the impact of three different low-frequency sea surface temperature (SST) variability modes located in the Indian and the Pacific Oceans on the interannual variability of the South American Monsoon System (SAMS) using observed and numerical data. Rotated Empirical Orthogonal Function (REOF) analysis and numerical simulations with a General Circulation Model (GCM) were used. One of the three SST variability modes is located close to southeastern Africa. According to the composites, warmer waters over this region are associated with enhanced austral summer precipitation over the sub-tropics. The GCM is able to reproduce this anomalous precipitation pattern, simulating a wave train emanating from the Indian Ocean towards South America (SA). A second SST variability mode was located in the western Pacific Ocean. REOF analysis indicates that warmer waters are associated with drought conditions over the South Atlantic Convergence Zone (SACZ) and enhanced precipitation over the sub-tropics. The GCM indicates that the warmer waters over Indonesia generate drought conditions over tropical SA through a Pacific South America-like (PSA) wave pattern emanating from the western Pacific. Finally, the third SST variability mode is located over the southwestern South Pacific. The composites indicate that warmer waters are associated with enhanced precipitation over the SACZ and drought conditions over the sub-tropics. There is a PSA-like wave train emanating from Indonesia towards SA, and another crossing the Southern Hemisphere in the extra-tropics, probably associated with transient activity. The GCM is able to reproduce the anomalous precipitation pattern, although it is weaker than observed. The PSA-like pattern is simulated, but the model fails in reproducing the extra-tropical wave activity. (AU)

• FAPESP's process: 01/13816-1 - Brazilian component of the South American low level jet east of the Andes field experiment: interaction in meso and large scale between the Amazon and La Plata River Basins
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 01/06842-6 - Study of the influence of the subtropical Atlantic ocean on the climate of South America
• Grantee: Anita Rodrigues de Moraes Drumond
• Support Opportunities: Scholarships in Brazil - Doctorate