Daily intensity of extreme rainfall in Argentina and their relationship with the Southern Ocean Sea surface temperature

FEDERICO ARIEL ROBLEDO; OLGA C. PENALBA; MARIA LAURA BETTOLLI

Montrel Canada

Conferencia; IAMAS, IAPSO and IACS Joint Assembly, (MOCA-09); 2009

IAMAS, IAPSO and IACS

The main objective of this research is to analyze the relationship between sea surface temperature (SST) of the Southern Oceans and the daily intensity of extreme rainfall (DIER) over Argentina. A Singular Value Decomposition (SVD) analysis was performed jointly on DIER in Argentina and SST in the Southern Oceans. The analysis was performed in the period 1962-2005, using two data sets: Kaplan SST V2 of the southern ocean NOAA)and daily rainfall observations from Argentina (SMN). Autumn is the season of the year that is best represented by the first mode, accounting for up to 49% of the autumn covariance between DIER and SST. Spring is the second best represented first mode with 45%. The spring and autumn SST patterns are different, the first one show a dipole in the South Pacific Ocean (SPO) with opposite anomalies of SST between the southwest (180ºW 40ºS) and northeast (90ºW ? 5ºS) of the SPO. Autumn pattern does not show a dipole in the SPO and the covariance is only significant in the tropical Pacific Ocean. Nevertheless, the spring and autumn DIER patterns are similar, with a strong covariance in the central and east of Argentina. Cold condition in the central-east Pacific SST during autumn are associated with lower rainfall intensity in in central-eastern Argentina. The temporal patterns of DIER exhibit significant inter-annual variability in autumn and spring, with periods of 4 to 6 years. The autumn patterns suggest a very low-frequency variation with a period longer than 15 years.