Physical Oceanography Data Sets

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https://hdl.handle.net/1912/4878

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Browsing Physical Oceanography Data Sets by Subject "Cold tongue"
  • Dataset
    Slab boundary layer model simulations for “Dynamical importance of the trade wind inversion in suppressing the southeast Pacific ITCZ”
    (Woods Hole Oceanographic Institution, 2023-10-05) Gonzalez, Alex O.
    Sea surface temperature (SST) gradients are a primary driver of low-level wind convergence in the east Pacific Inter-Tropical Convergence Zone (ITCZ) through their hydrostatic relationship to the surface pressure gradient force (PGF). However, the surface PGF may not always align with SST gradients due to variations in boundary layer temperature gradients with height, i.e., the boundary layer contribution to the surface PGF. In this study, we investigate the observed northern hemisphere position of the east Pacific ITCZ using a slab boundary layer model (SBLM) driven by different approximations of the boundary layer virtual temperature field. SBLM simulations using the entire boundary layer virtual temperature profile produce a realistic northern hemisphere ITCZ. However, SST-only simulations produce excessive equatorial divergence and southern hemisphere convergence, resulting in a latitudinally-confined double ITCZ-like structure. Observed virtual temperature gradients highlight the importance of northward temperature gradients strengthening with height from the equator to 15 degrees south below the trade wind inversion (TWI). Our interpretation is that the equatorial cold tongue induces relatively weak high surface pressure and double ITCZ-like convergence because the resulting layer of cold air is shallow. Concurrently, relatively strong high surface pressure spreads out in the southern hemisphere due to interactions between stratocumulus clouds and the ocean surface. Together, the equatorial cold tongue and the TWI/stratocumulus clouds enable a more northern hemisphere dominant ITCZ. Thus, we provide evidence of a dynamical link between the equatorial cold tongue, low clouds, and double ITCZs, which continue to be problematic in Earth system models.