Rossby wave breaking and extreme windstorms overWestern Europe
(English)Manuscript (preprint) (Other academic)
We investigate the role of upper-level Rossby wave breaking in the evolution ofthemost extreme windstorms affecting three regions inWestern Europe: Britainand Ireland, Scandinavia and Western Continental Europe. Using ERA40and ERA-Interim reanalysis data along with EC-Earth model output at twodifferent spatial resolutions, we first construct an extreme wind climatologyover the selected regions and inter-compare the model climatology with thatcomputed from the reanalysis data. Using a storm destructiveness measure, wethen select the top 25 most destructive storms in each region from a multidecadalclimatology in each of our four datasets; track-by-track analysis revealsa good agreement in the trajectories and evolution of these storms in bothmodel resolutions compared to the reanalysis data. Temporal MSLP reanalysiscomposites demonstrate that in each region, there exists a set of large-scaleconditions conducive to the development of these storms; similar composites ofmodel output data show that these surface conditions are broadly well capturedby both model resolutions. Temporal composites of potential temperature onthe 2-PVU surface using reanalysis data reveal that these regional large-scalesurface patterns can be associated with exceptional cyclonic and anti-cyclonicwave breaking occurring contemporaneously in the North Atlantic; the preciselocation of these wave breaking events controls the position and orientation ofan intense upper-level jet which in turn determines into which region the stormsare steered. Similar composites using model output data show qualitativelythe same picture, but with an overall positive bias most likely due to a lowertropopause height in the model.
Rossby wave breaking, Extreme windstorms, Western Europe
Meteorology and Atmospheric Sciences
Research subject Atmospheric Sciences and Oceanography
IdentifiersURN: urn:nbn:se:su:diva-86519OAI: oai:DiVA.org:su-86519DiVA: diva2:587162