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Title:
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The Association Between the North Atlantic Oscillation and the Interannual Variability of the Tropospheric Transport Pathways in Western Europe
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Author(s):
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Orza, J.A.G.; Cabello Ganuza, M.; Galiano, V.; Vermeulen, A.T.; Stein, A.F.
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Published by:
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Publication date:
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ECN
Environment & Energy Engineering
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11-6-2013
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ECN report number:
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Document type:
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ECN-B--13-005
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Book
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Number of pages:
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Full text:
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17
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Download PDF
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Published in: Langranian Modeling of the Atmospheric, 127, 141, Geophysical Monograph Series 200.
Abstract:
The variations in tropospheric transport pathways over a 20 year period, 1990–
2009, are studied at six locations in Europe. Three Atlantic (Lisbon, Mace Head,
and Cabauw) and three Mediterranean sites (Málaga and Elche in the western part
and Lecce in the central Mediterranean) are considered. The work is based on the
identification of flow types at each location by robust cluster analysis of the
trajectories, the assessment of temporal trends for each advection pattern, and
subsequent quantification of the association, at the monthly scale, between the
North Atlantic Oscillation (NAO) index (NAOi) and the frequency of occurrence of
the identified flows. This exploratory study demonstrates the usefulness of the
approach for specific locations in a context where synoptic circulation/weathertype
classifications are usually used. A different number of advection pathways
were identified at each location. Common features to all the sites were prevalence
of westerly flows, strong seasonal variability, and association of the air flow types
to known synoptic situations in both phases of the NAO. The degree of association
varies strongly with latitude, location within the Mediterranean basin, and closeness
to the action centers. Overall, flows reaching Mace Head and Cabauw present
stronger association to the NAO, which is substantially reduced at lower latitudes
and is not significant at Lisbon. Significant temporal trends are found for northerly
flows at Mace Head andMálaga, associated to changes at the beginning of the study
period that are also present in the NAOi time series. WSW flows at Mace Head
exhibit a steady decreasing trend over the whole period.
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