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PENALBA Olga Clorinda

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Título:

Impact of climate variability and change on meteorological droughts over Southern South America

Autor/es:

4. JUAN A. RIVERA; OLGA C. PENALBA; DIEGO C. ARANEO

Reunión:

Conferencia; Our Common Future Under Climate Change International Scientific Conference,; 2015

Resumen:

Droughtsare perceived as one of the costliest and least understood natural disasters,given the difficulty in defining its beginning and end, its slow developmentand its multiple regional aspects. Southern South America (SSA) was noexception to this hazard, whose impacts were evident in the reduction in cropyields, reduced cattle products, streamflow deficiencies and consequentlyproblems for hydroelectric power generation. This research addresses theobserved spatial and temporal variability of precipitation and meteorologicaldrought over SSA during the 20th century, and the expected impacts of climatechange on these variables. The Standardized Precipitation Index (SPI) was usedas a short- and long-term drought indicator, given its suitability for thestudy region. Observed trends in the area affected by drought conditions wereassessed through a non-linear approach based on the residual of the empiricalmode decomposition, a recently proposed methodology which is robust in presenceof non-stationary data. Trends indicate the existence of a low-frequencyvariability that modulates regional precipitation patterns at differenttemporal scales, and warns about possible future consequences in the social andeconomic sectors if trends towards an increase in the drought affected areacontinue. This non-linearity was also evident on the temporal behavior of otherhydrometeorological variables, like the annual number of dry days overArgentina, and on the streamflow deficiencies over the central Andes andPatagonia. Moreover, links with decadal oscillations as the PDO were identifiedin the modulation of the decadal component of the annual cumulated deficitvolume in the central Andes of Argentina.The future assessment of precipitation and meteorological drought conditionswas performed through a CMIP5 multi-model ensemble based on 15 GlobalCirculation Models (GCMs) forced under two future scenarios (RCP4.5 andRCP8.5). Changes in meteorological drought characteristics were identified bythe difference for early (2011-2040) and late (2071-2100) 21st century valueswith respect to the 1979-2008 baseline. Future climate conditions are expectedto modify the regional characteristics of meteorological droughts over SSA, butthe range of uncertainty in the expected changes is high. A significantincrease in the number of drought events for most of the 21st centurysub-periods and scenarios is projected for the multi-model ensemble outputs.The mean duration of drought events will be shorter, with no significantchanges in the severity of droughts and the occurrence of multi-decadal changesin the number of critical dry months is likely, although the significance inthe changes depends on the region, future time horizon and scenario. Theseresults overlap with a projected increase in precipitation over most of theregions, which has a strong seasonality and, therefore, will have someimplications upon the future meteorological drought developments and theagricultural and hydrological practices in SSA. It is expected that theoutcomes of

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