TROPICAL OCEAN GLOBAL WARMING AND ITS INFLUENCE ON THE INTENSITY OF DAILY PRECIPITATION IN ARGENTINA

FEDERICO ARIEL ROBLEDO; VERA, CAROLINA; OLGA C. PENALBA

Montevideo

Conferencia; WCRP Conference for Latin America and the Caribbean, "Developing, Linking and Applying Climate Knowledge"; 2014

WCRP World Climate Research Programe

The intensity of daily extreme precipitation (DIER75) in Argentina has exhibited during the second half of the twentieth century significant modulations by both long-term trends and year-to-year variability, as our previous analyses showed. Moreover, a significant relationship has been found between DIER75 anomalies calculated for 35 raingauges and sea surface temperature (SST) in the tropical regions for period 1962-2005. In addition, during the past 100 years, a clear increase in global SST anomalies haven been detected. The warming is large at the tropics and particularly over the western equatorial Pacific. Moreover, tropical SST increase exhibits a nonlinear evolution superimposed with the temporal year-to-year variability. Nevertheless, it is yet unclear how that combined SST anomaly signal has affected the activity of daily extreme events in Argentina. The aim of this work is then to describe and understand the main temporal oscillations and trends associated with DIER75 in the context of global warming. Special focus is made in exploring the relationship between the large tropical SST increase and DIER75 variations in Argentina along the second half of the twentieth century. The study is highly relevant as it provides valuable information about changes in the activity of the daily precipitation extremes in Argentina in the context of a global warming. Singular Value Decomposition (SVD) between monthly standardized DIER75 anomalies over Argentina and monthly SST anomalies between 17.5 ° N and 90 ° S is performed under three different conditions: a) keeping trends, b) removing linear trends, and) removing global SST warming signal. The comparison of the results obtained from the three SVD analyses shows that in the context of global warming, the influence of central equatorial Pacific SST anomalies onto DIER75 anomalies associated with ENSO weakens, and the corresponding SST anomalies expand southward. In addition, DIER75 anomalies get weaken in central-eastern Argentina and in the region by the extratropical Andes. DIER75 associated variability shows a nonlinear trend and dominant oscillation in 6 and 4 years. Also, in the context of global warming, there is no clear relationship between Niño Modoki and DIER75 in central eastern of Argentina, which is significant in the analysis made removing trends . In contrast, the Indian Ocean intensifies its relationship with DIER75 in central Argentina with periods of variability of 3.3 years. On the other hand, the relationship between tropical Atlantic Ocean and DIER75 in central Argentina presents nonlinear trends and significant variability on periods of 11.2 years. In the context of global warming, the subtropical Atlantic Ocean relationship with DIER75 over central Argentina is reinforced.