On the Influence of Sea Surface Temperatures on Cyclone Characteristics in the Gulf Stream and Kuroshio Region

• Main Author: Tsopouridis, Leonidas
• Other Authors: orcid:0000-0002-2043-0871
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2021
• Subjects: Pacific; North Atlantic
• Online Access: https://hdl.handle.net/11250/2724565

The Gulf Stream and the Kuroshio are the western boundary currents in the North Atlantic and North Pacific, respectively and are associated with maxima in midlatitude precipitation and air-sea heat exchange in the midlatitudes. Both regions are characterized by the strongest sea surface temperature (SST) gradients over the Northern Hemisphere’s midlatitudes, able to anchor the storm track and influence the development of individual cyclones. Other mechanisms were also found to contribute significantly to the intensification of cyclones. These include the absolute SST values, the land-sea temperature contrast, latent heat release, surface fluxes from the ocean, and strong upper-level forcing.The main goal of this thesis is to understand the characteristics of individual cyclones and the mechanisms leading to their intensification, as well as to document the changes on both individual cyclones and the storm track as a whole when a strong SST gradient is present/absent in the Gulf Stream and Kuroshio region. Individual cyclones were tracked using the University of Melbourne cyclone detection and tracking algorithm and categorised depending on their propagation relative to the Gulf Stream and Kuroshio SST fronts, which were detected automatically using an established algorithm that was originally used for detecting atmospheric fronts. Comparing results for the different categories we found that cyclones staying north of the Gulf Stream SST front and those crossing it northward were the ones with the maximum intensification,due to the increased low-level baroclinicity, arising primarily from the land-sea temperature contrast. Differently, in the Kuroshio region, we found cyclones crossing the SST front or remaining on its warm side, to intensify the most. We related this higher intensification to the propagation of cyclones near the left exit region of the jet stream,accounting also for higher precipitation. Even if the SST front contributes to the climatological low-level baroclinicity, no direct effect to the ...