INTER-ANNUAL AND INTERDECADAL VARIABILITY OF SEA SURFACE TEMPERATURE IN THE CENTRAL PACIFIC OCEAN AND RELATION WITH DAILY INTENSITY OF EXTREME RAINFALL IN SOUTH AMERICA

FEDERICO ARIEL ROBLEDO; OLGA C. PENALBA

Melbourne, Australia

Conferencia; 9th International Conference on Southern Hemisphere Meteorology and Oceanography.(9ICSHMO); 2009

American Meteorological Society

The El Niño/Southern Oscillation (ENSO) phenomenon is the dominant inter-annual mode of the Pacific climate and is associated with near-global climate variations. ENSO-related precipitation anomalies in certain regions of the globe might be modulated by lower frequency climate modes. Among these modes, the Pacific Decadal Oscillation (PDO) plays an important role.The main objective of this research is the knowledge of the relationship between ENSO and PDO phases with the daily rainfall intensity over Argentina. The analysis was performed in the period 1962-2005, using three data sets: monthly time series of PDO index, Sea Surface Temperature anomalies of the region Niño 3.4 (SST3.4) from NCEP/NCAR, and daily rainfall observations from Argentina. Monthly index of daily intensity of extreme rainfall (DIER, rainfall greater than 75th daily percentile) was calculated. Spearman non linear correlation coefficient lagged was used to explore the relationship between DIER and SST3.4 indices. Low pass band filter was applied to monthly DIER series (F-DIER) removing the high frequency variability (less than 7 years). The occurrence of positives (negatives) SST3.4 anomalies from July to November in the region Niño3.4, tends to enhance positives (negatives) DIER during November in the center and Northeast region of Argentina. However, in austral winter, August DIER shows negative significant correlations with SST3.4 from July to November of the previous year in the center of Argentina. This means that anomalies of SST in the Central Pacific have opposite response in summer and winter DIER, with a delay impact during cold months (12 months lagged), while in summer months the impact in DIER is more immediate (1 or 2 months lagged). During July and August, F-DIER evidence negative and significant correlations with August to November mean PDO index in the center and Northeast region of Argentina, maintaining the delay impact in precipitation.