Student Seminar: Ayako Yamamoto
Please join us tomorrow, Wednesday Oct 3 for a seminar by Ayako Yamamoto entitled “On the source of European winter temperature variability.” in Burnside Hall room 934 at 14:35 . Her abstract follows:
The traditional view that ocean heat transport causes warmer winters in Western Europe relative to those in western North America (e.g., Maury, 1855), was challenged in a provocative study by Seager et al. (2002). They offer the alternative hypothesis that the zonal asymmetry in Northern Hemisphere climatological temperatures is instead set by the orographically-forced southwesterly winds over the Atlantic Ocean, with the annually-integrated net ocean heat transport playing a small role. However, neither paradigm addresses the role of air mass trajectory versus ocean heat transport on the variability in Western European temperatures. In this project, we quantitatively evaluate the source of wintertime temperature variability in Western Europe, examining the contribution of the trajectory of the air parcels arriving in Western Europe, the sea surface temperature (SST) over which these air parcels travel, and the role of the coupling between the two mechanisms. To tackle this question, a novel Lagrangian approach is used: we track air particles backward in time using the atmospheric dispersion model, FLEXPART (Stohl et al. 2005), driven with meteorological data from the National Centers of Environmental Prediction each January over the period from 1981 to 2009. The dispersion model is the appropriate tool to study this question because it accounts for turbulence in the planetary boundary layer. We then conduct a suite of idealized experiments that explicitly separates the role of SST and trajectory variability. Our preliminary results suggest that pathway variability is a much better predictor of interannual variability in the along-pathway heat fluxes than SST. However, SST also appears to be necessary in reconstructing the true heat fluxes on longer than interannual time scale.