The Response of the Offshore Atmospheric Marine Layer to Coastal Topography

QuikSCAT wind and numerical model simulations show that offshore of the shelf, there are significant responses of the marine layer to coastal topography. Where the synoptic scale imposes an along-shore pressure gradient above a threshold, the atmosphere is weakly accelerated along the coast and toward the equator. With in this zone, there is usually one two major coastal capes. The lower atmosphere is further accelerated by hydraulic effects in response to the capes downwind. The result is often a narrow, curved arc of maximum wind speeds extending more than 300 km cross-shore. The fastest winds in zone are over the mid-shelf and the maximum wind speed decreases offshore. The marine layer and atmosphere through the mid-levels above this maximum zone responds as a stationary wave. The ocean surface experiences a wind stress divergence on the north side of this maximum and a wind stress convergence on the south side. The wind stress curl is negative causing downwelling as the fastest wind speeds are over the shelf. These features are short-lived but dominate monthly means of the wind speeds and wind stress. Currently conducted regional climate simulations reveal that these zones of maximum winds can have a climate signature and significance.