Abstract

OLIVEIRA, Washington; CUNHA, Lúcio  and  PAIVA, Isabel. Influence of the North Atlantic Oscillation on the Mondego and the Vouga rivers streamflow: relevance in the occurrence of floods and flooding processes. GOT [online]. 2017, n.12, pp.255-279. ISSN 2182-1267.  https://doi.org/10.17127/got/2017.12.011.

The North Atlantic Oscillation (NAO) is the main atmospheric circulation pattern in the North Atlantic sector. Its dipole structure remains visible throughout the entire year. Although the atmospheric mechanisms that govern the NAO are beyond the scope of knowledge, the comprehension of its effects is widespread, even though forecasting it poses a great challenge. Providing important information to this challenge, at the present time, trends are contributing with vital data for a perception of the NAO variability over time. The weather in the Iberian Peninsula and Portugal is strictly related to the NAO phase (positive or negative), and therefore to all its elements. However, precipitation, out of all-weather elements, is by far the most reliant on the phase of this atmospheric dipole. Hence, precipitation such as rain is the major source for river streamflow in the Mediterranean Climate. For that reason, NAO impacts are likely to occur. That fact becomes even more pertinent if we consider that the NAO explains more atmospheric variability during boreal winter (December to March) which is the period with the most significant rainfall across the Iberian Peninsula and when extreme hydrological phenomena, namely flood and flooding processes, are more frequent. Distinctively but in great agreement in their behaviour, Vouga and Mondego hydrographic basins are no exception in their linkage to the NAO with a significant response to rainfall patters imposed by this Oscillation.

Keywords : North Atlantic Oscillation (NAO); Atmospheric Precipitation; Rivers Streamflow; Flood and Flooding; Vouga river; Mondego river.

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