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Earth System Dynamics An interactive open-access journal of the European Geosciences Union

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Earth Syst. Dynam., 7, 371-384, 2016
https://doi.org/10.5194/esd-7-371-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
22 Apr 2016
Atmospheric rivers moisture sources from a Lagrangian perspective
Alexandre M. Ramos1, Raquel Nieto2, Ricardo Tomé1, Luis Gimeno2, Ricardo M. Trigo1, Margarida L. R. Liberato1,3, and David A. Lavers4 1Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
2EPhysLab (Environmental Physics Laboratory), Facultade de Ciencias, Universidade de Vigo, Ourense, Spain
3Escola de Ciências e Tecnologia, Universidade de Trás-os-Montes e Alto Douro, Vila Real, Portugal
4European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, RG2 9AX, UK
Abstract. An automated atmospheric river (AR) detection algorithm is used for the North Atlantic Ocean basin, allowing the identification of the major ARs affecting western European coasts between 1979 and 2012 over the winter half-year (October to March). The entire western coast of Europe was divided into five domains, namely the Iberian Peninsula (9.75° W, 36–43.75° N), France (4.5° W, 43.75–50° N), UK (4.5° W, 50–59° N), southern Scandinavia and the Netherlands (5.25° E, 50–59° N), and northern Scandinavia (5.25° E, 59–70° N). Following the identification of the main ARs that made landfall in western Europe, a Lagrangian analysis was then applied in order to identify the main areas where the moisture uptake was anomalous and contributed to the ARs reaching each domain. The Lagrangian data set used was obtained from the FLEXPART (FLEXible PARTicle dispersion) model global simulation from 1979 to 2012 and was forced by ERA-Interim reanalysis on a 1° latitude–longitude grid.

The results show that, in general, for all regions considered, the major climatological areas for the anomalous moisture uptake extend along the subtropical North Atlantic, from the Florida Peninsula (northward of 20° N) to each sink region, with the nearest coast to each sink region always appearing as a local maximum. In addition, during AR events the Atlantic subtropical source is reinforced and displaced, with a slight northward movement of the sources found when the sink region is positioned at higher latitudes. In conclusion, the results confirm not only the anomalous advection of moisture linked to ARs from subtropical ocean areas but also the existence of a tropical source, together with midlatitude anomaly sources at some locations closer to AR landfalls.


Citation: Ramos, A. M., Nieto, R., Tomé, R., Gimeno, L., Trigo, R. M., Liberato, M. L. R., and Lavers, D. A.: Atmospheric rivers moisture sources from a Lagrangian perspective, Earth Syst. Dynam., 7, 371-384, https://doi.org/10.5194/esd-7-371-2016, 2016.
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Short summary
An atmospheric river (AR) detection algorithm is used for the North Atlantic Ocean basin, allowing the identification of the major ARs that affected western European coasts between 1979 and 2014. A Lagrangian analysis was then applied in order to identify the main sources of moisture of the ARs that reach western European coasts. Results confirm not only the advection of moisture linked to ARs from subtropical ocean areas but also the existence of a tropical one.
An atmospheric river (AR) detection algorithm is used for the North Atlantic Ocean basin,...
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