%0 Conference Proceedings
%4 sid.inpe.br/mtc-m19/2010/09.13.19.38
%2 sid.inpe.br/mtc-m19/2010/09.13.19.38.28
%T ENSO and extreme rainfall events in present and future climate in South America
%D 2010
%A Grimm, A M,
%A Flach, R A,
%A Tedeschi, Renata Gonçalves,
%@affiliation Physics, Universidade Federal do Paraná, Curitiba, Brazil
%@affiliation Physics, Universidade Federal do Paraná, Curitiba, Brazil
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@electronicmailaddress grimm@fisica.ufpr.br
%@electronicmailaddress rafa.ambiental@gmail.com
%@electronicmailaddress renata.tedeschi@cptec.inpe.br
%B The Meeting of the Americas.
%C Foz do Iguaçu, BR
%8 08-12 aug 2010
%S Abstracts
%K Extreme events, climate change and variability, precipitation, ENSO.
%X Analysis with observed data shows a clear association between ENSO (El Niño / La Niña) episodes and the frequency of extreme rainfall events over South America. ENSO is the main source of interannual variability in South America, and its influence varies throughout the annual cycle. For instance, in austral spring (November) it is very significant in southeastern South America, producing increase (decrease) of extreme events in the La Plata Basin during El Niño (EN) (La Niña, LN) episodes. In peak summer monsoon season (January), the extreme events in Central-East South America, in the South Atlantic Convergence Zone and in the core monsoon region are enhanced (hampered) during EN (LN) episodes. In austral autumn (April), there is significant enhancement of extreme events in the La Plata Basin during EN episodes, while at the same time of LN episodes the frequency of extreme events is increased in Northeast Brazil. These significant changes in extremes are much more extensive than the corresponding changes in monthly rainfall, because the highest sensitivity to ENSO is in the extreme range of daily precipitation. The ENSO-related changes in the frequency of extreme rainfall are important, since the most dramatic consequences of climate variability result from changes in extreme events. Therefore, an important issue is the assessment of the impact of global anthropogenic climate change on ENSO and its impact on extreme rainfall in South America. Possible future changes in the influence of ENSO on the frequency of extreme precipitation events in South America are analyzed through the outputs of the coupled model ECHAM5-OM for the twentieth century climate (1960-2000), and the future climate scenario SRES-A2 (2060-2100). Extreme events are defined as three-day mean precipitation above the 90th percentile. The EN and LN years in the model output are determined from the Niño 3 SST anomalies (as in the observations), and verified against the extreme phases of the ENSO mode of SST variability, for both periods. The model reproduces well the strongest observed impacts of ENSO in the present climate, although not all their features. The areas with consistent impact on the frequency of extreme events are generally extended in the future climate, and the ENSO-related frequency is enhanced with respect to the present in several instances, such as the spring in southeastern South America (La Plata Basin). Also the shifts produced in the daily rainfall distributions, with respect to present climate during EN, LN and all years are examined. In southern Brazil, for instance, the probability of light rainfall in spring is reduced, while it increases in the heavy rainfall tail of the frequency distributions.
%@language en