Boundary layer shock-like dynamics of the ITCZ

Evidence of shock-like structures in the boundary layer of axisymmetric tropical cyclones has been shown in recent studies. The purpose of this presentation is to explore the possibility of shock-like boundary layer structures in the Intertropical Convergence Zone (ITCZ). Zonally symmetric slab boundary layer analytical and numerical models are formulated. When the boundary layer meridional inflow is large enough, the neglect of the meridional advection terms v(∂u/∂y) and v(∂v/∂y) is not justifiable. With the inclusion of these terms in the boundary layer zonal and meridional momentum equations, along with an initial condition of a broad low pressure region just above the boundary layer, discontinuities form in both the zonal and meridional winds after 10-20 hours. Along with these discontinuities, singularities arise in vorticity, divergence, and Ekman pumping. Such thin zonally elongated strips of vorticity, divergence, and convection are often observed in the central and eastern Pacific ITCZ in satellite imagery. These Burgers' "shock-like" structures emerge because the meridional boundary layer equation contains an embedded Burgers' equation.