Atmospheric structure and momentum balance during a gap-wind event in Shelikof Strait, Alaska

Abstract

Gap winds occur in topographically restricted channels when a component of the pressure gradient is parallel to the channel axis. Alongshore sea level pressure ridging was observed. Vertical cross sections show that across-strait gradients of boundary-layer temperature and depth accounted for the pressure distribution. Geostrophic adjustment of the mass field to the along-strait wind component contributed to development of the observed pressure pattern. However, the Rossby radius was larger than the strait width, and atmospheric structure in the strait exit region indicates transition of the flow to open coastline conditions. Entrainment of air into the boundary layer was the largest retarding force and contributed to the along-strait profile of boundary-layer depth. Large horizontal divergence was observed within the strait, yet boundary-layer depth increased slightly following the flow. Entrainment at the inversion and sea surface fluxes accounted for along-strain variation of boundary-layer equivalent potential temperature. -from Authors