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Atmospheric rivers in the Atlantic Ocean

October 15, 2019 @ 3:00 pm - 4:00 pm

Alexandre M. Ramos, Assistant Researcher
Instituto Dom Luiz – Universidade de Lisboa

The speaker has more than 15 years of experience in climate research, in extra-tropical cyclones, heatwaves, precipitation impacts, and climate change. I participated in more than 13 national and international projects.

My research is now focused on the Atmospheric Rivers variability in Atlantic Basin and their influence in adjacent costal regions. Currently I am a Leader of Working Package 1 of the DOMACLES COST action (compound event project). In recent years it was found that there is a strong relationship between Atmospheric Rivers (ARs) and extreme precipitation and floods across the Atlantic Ocean Basin. ARs are relatively narrow and elongated filaments of high water vapour transport, which are associated with tropical moisture exports and often occur in combination with the passage of strong extratropical cyclones. Such structures transport more than 90% of the total mid-latitude vertically integrated water vapour and can lead to intense precipitation episodes due to their interaction with topography or ascent in the Warm Conveyor Belt. The relationship is especially strong in the Atlantic Ocean along the western European and South Africa coasts, with some areas having 8 of their top 10 annual maxima precipitation events related to ARs. In the case of the Iberian Peninsula, the association between ARs and extreme precipitation days in the western river basins is noteworthy, while for the eastern and southern basins the impact of ARs is reduced. Regarding the South Atlantic, the role played by ARs bound for the western coast of South Africa, during the austral winter months, was recently evaluated. It was shown that in areas of high topography they present the highest percentage of persistent ARs contribution to rainfall, whereas stations downwind of the major topographic barriers show the lowest contributions. We show that around 70% of the top 50 daily winter rainfall extremes in South Africa are linked to ARs.


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