Fumiaki is a researcher in GFI. He has been working in GFI from 2014. He has worked on the observed Arctic Climate change with Noel Keenlyside. From this month he started working with Camille Li on the future climate change. On the other hand, since his Ph.D., he has been working on the midlatitude storm track and jets and their relation to SST fronts with Hisashi Nakamura, Noel Keenlyside and Thomas Spengler. His expertise is climate dynamics in the extratropics and relevant air-sea heat exchange.
While the climatological mean sensible and latent heat fluxes are remarkably well described using climatological-mean fields in the bulk flux formulae, this study shows that a significant fraction of the climatological-mean wind speed in the mid-latitudes is associated with wind variations on synoptic time scales. Hence, the prevailing wind direction associated with the most intense air-sea heat exchange can differ from the mean wind direction. To pinpoint these striking differences between the climatological and synoptic viewpoint, this study presents a global climatology of the prevailing surface wind direction during air-sea heat exchanges calculated for instantaneous and time-averaged reanalysis data. The interpretation of the fluxes in the lower latitudes is basically unaffected by the different time averages, highlighting the time-mean nature of the circulation in the low latitudes. In the mid-latitudes, however, the prevailing wind direction features a significant equatorward component for sub-weekly time averages, which reverts to pure westerlies for longer timescales. These findings pinpoint the necessity to consider sub-weekly time-scales, in particular along the mid-latitude SST fronts, to describe the air-sea heat exchange in a physically consistent way.
Arranged date for the seminar talk: Jun 03, 2019