Descripción: Fil:Romero, S.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Eighteen year (1985-2002) sea surface temperature (SST) data are used to study the intraseasonal variability of the Patagonian shelf break front (SBF) in the SW South Atlantic Ocean between 39° and 44°S. The cross-shelf break SST gradients reveal distinct, previously undocumented thermal fronts located both, offshore and inshore of the SBF. Throughout the year the main SBF, identified as a band of negative SST gradient maxima (relatively strong offshore temperature decrease), forms a persistent feature located closed to the 200 m isobath, while two distinct negative gradient maxima are located inshore and offshore of this location. Daily SST images reveal the presence of three branches of cold waters whose edges delineate the above mentioned fronts. The two offshore branches closely follow lines of constant potential vorticity (f/h) and appear to be associated with the Malvinas Current, while a third branch, located further onshore, is not steered by the bottom topography. South of 40°S the onshore branch forms a quasi permanent front parallel to the SBF. Copyright 2008 by the American Geophysical Union.

Descripción: The classification of El Niño events was performed based on the time evolution of sea surface warming in the tropical Pacific Ocean during the period 1950-2000. Two sets of events were constructed: one in which the warming core migrates eastward along the tropical Pacific until April-June of the following year, and another one in which it evolves westward until November-January. The first type has associated positive precipitation anomalies over southeastern South America during April-June. It results from a favourable combination of cyclonic vorticity advection and humidity convergence. At high levels, cyclonic vorticity advection is explained in terms of an eastward extension of the subtropical jet. Enhanced humidity advection takes place by an increased low-level northwesterly flow to the east of the Andes. It provides enough moisture availability that, in combination with the upper-level cyclonic vorticity advection, supports heavy precipitation during April-June. The second type of event exhibits slight negative or near-normal precipitation anomalies over the same region. Both low and high-level circulation anomalies are also weaker in this case. The 1997-1998 El Niño is analysed separately because it cannot be classified into any of the previously described event types. The observed distribution of both types of events along the analysed period changes after the 1970s. Comparison with other authors' results suggests the influence of low-frequency processes such as the Pacific Decadal Oscillation (PDO). Copyright © 2008 Royal Meteorological Society.

Descripción: A Singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and the sea surface temperature (SST) of all the oceans from 17.5°N to 90°S in order to identify the large-scale variability of the SSTs related to extreme rainfall, in the period 1962-2005. The main objective of the article is to objectively recognize regions of the tropical and subtropical oceans that could be related with the extreme rainfall over Argentina. Spring is the season that is best represented by the first mode, accounting for up to 45% of the covariance between the DIER and SST. The first SVD mode of spring, summer and autumn presents a pattern of SST relating to the El Niño-Southern Oscillations (ENSO) phenomena with an enhanced DIER in different zones of centre and east of Argentina. In the second SVD mode of spring and summer, the SST patterns show cold conditions in the tropical and subtropical Atlantic and near Indonesia with an enhancement of the DIER in the centre and east of Argentina. These modes show a significant decadal variability. In the third SVD mode of spring and summer, the SST patterns present warm and cold conditions in the Indian Ocean and the centre and western Pacific Ocean (PO) with decreased rainfall in the northern and eastern portion of Argentina, respectively. This mode shows a significant period of temporal variability of around 14 years. The third mode of autumn presents warm conditions in the tropical Atlantic and the southwest PO with a low DIER in the centre and east of Argentina. This mode also presents temporal variability of around 14 years. The correlation between each mode derived from analysis of SVD and climate indices related with SST were computed. © 2012 Royal Meteorological Society.