Effects of ocean-atmosphere coupling in a modeling study of coastal upwelling in the area of orographically-intensified flow

Natalie Perlin, Eric Skyllingstad, and Roger Samelson

Oregon State University, College of Oceanic and Atmospheric Sciences

Regional ocean-atmosphere model is used to study three-dimensional coastal circulation in the presence of coastline bend. Coastal promontories often introduce significant lower tropospheric flow disturbances, leading to spatial variations in wind forcing over the coastal ocean. Wind-driven seasonal upwelling along the West coast of the U.S. is an example of ocean-atmosphere interaction on regional to local scale that becomes very complex around coastal capes and points.

Model domain is designed to simulate a coastline with an idealized bay, formed by successive inland and seaward coastal bends. Horizontal domain has 3-km grid boxes, it extends about 630 km in the alongshore direction, about 480 km in the cross-shore direction including coastal land in the east. Results of the study show that this scale is large enough for orographic wind intensification to develop downstream of the inland bend during the simulation, while the grid is fine enough to resolve nearshore wind modification due to developing coastal upwelling. Sea surface temperature fields show temporal and spatial differences in upwelling development along the two sides of the simulated bay, the complexity of wind field over the area, and the importance for accurate wind representation for coastal ocean prediction. Atmospheric marine boundary layer exhibits features characteristic of the areas downwind of major capes and points along the West coast. This allows for the analysis of boundary layer details in regions of its rapid vertical and horizontal changes.