Shock-like Structures in the ITCZ Boundary Layer

Evidence of shock-like structures in the boundary layer of axisymmetric tropical cyclones has been shown in Williams et al. (2013). The purpose of this presentation is to explore the possibility of shock-like changes in the Intertropical Convergence Zone (ITCZ). When the boundary layer meridional inflow is large enough, the neglect of the meridional advection terms v(du/dy) and v(dv/dy) is not justifiable. With the inclusion of these terms in the boundary layer meridional momentum equation, along with an initial condition of low pressure in the tropics, shock-like changes occur in the horizontal winds and Ekman pumping. The large increase in Ekman pumping occurs in a thin strip, and the peak Ekman pumping lies near the center of the ITCZ. Such thin zonally elongated strips of convection and vorticity are often seen in the central and eastern Pacific ITCZ. As a theoretical basis for the above arguments, the zonally symmetric version of the slab boundary layer model used in Williams et al. (2013) is implemented. The emphasis is to help interpret satellite observations of the ITCZ as Burgers' "shock-like" structures that emerge from the fact that the meridional boundary layer equation contains an embedded Burgers' equation (Burgers 1948).