Accueil > Actualités > Séminaires > Séminaire de Young-Oh Kwon


Titre : Northern Hemisphere Atmospheric Transient Eddy Fluxes and Their Co-variability with the Gulf Stream and Kuroshio-Oyashio Extensions
Nom du conférencier : Young-Oh Kwon
Son affiliation : (Woods Hole Oceanographic Institution)
Laboratoire organisateur : LOCEAN
Date et heure : 02-05-2012 12h15
Lieu : UPMC, 4 place Jussieu, Paris 5e - LOCEAN, Tour 45-55 salle des séminaires
Résumé :


Time series of winter (January-March) meridional transient eddy heat and moisture fluxes (<v'T'> and <v'q'>) for 1979-2009 in two separate frequency bands, i.e. the synoptic (2-8 days) and intra-seasonal (8-90 days) are calculated for the whole Northern Hemisphere based on daily atmospheric variables from the NASA Modern Era Retrospective-analysis for Research and Applications (MERRA) at 1/2 degrees latitude by 2/3 degrees longitude resolution. The climatological mean transient eddy fluxes in the two frequency bands exhibit markedly distinct spatial patterns. The synoptic transient eddy fluxes exhibit the storm-tracks, of which maxima are co-located wuith the Gulf Stream and the Kuroshio-Oyashio Extensions. On the other hand, the intra-seasonal transient eddy fluxes are associated with the Arctic Oscillation and Pacific North American teleconnection with the maxima co-located with the major orogaphy, e.g. the Rockies and Greenland. In a vertically and zonally integrated poleward heat transport sense, the maximum heat transports in the two frequency bands are comparable, while the sensible heat fluxes are twice greater than the latent heat fluxes.


In addition, co-variability between the meridional transient eddy heat and moisture fluxes and their divergence and the changes in the position of the ocean fronts associated with the Kuroshio Extension (KE), Oyashio Extension (OE) and Gulf Stream (GS) is examined with a focus on the interannual to decadal time scale. Statistically significant correlations are found from the surface up to 250 hPa for all three ocean fronts. The regression patterns when the GS (or KE) leads the transient eddy fluxes are almost opposite to those when the GS (or KE) lags by a couple of years, thus implying a negative feedback between the ocean and atmosphere. On the other hand, the regressions on the OE index exhibit the same signs between the positive and negative lags, implying a positive feedback. The co-variability explained approximately half of the interannual and longer variance in the synoptic band, while only  ~20 % for the intra-seasonal band.