Quasi-Balanced Contributions to Forced Secondary Circulations

摘要

It is well known that hurricane vortices could be approximated, after azimuthal average, by gradient-wind and hydrostatic balance equations within an error of less than 10%, except in the planetary boundary layer (PBL) and the upper outflow layer (e.g., Willoughby 1990, Zhang et al. 2001). rnUsing Eliassen’s (1951) balanced model, Willoughby (1979) showed that radial gradients of latent heat release in the eyewall could induce a deep layer of inflow in the lower half of the troposphere, a shallow outflow layer above, upward motion in the eyewall and subsidence within the eye. In contrast, the surface friction tends to produce a shallow layer of inflow in the PBL and a deeper layer of outflow and updrafts above.