Orographic effects during winter cold-air outbreaks over the Sea of Japan (East Sea): Results from a shallow-layer model

We study the effects of the coastal topography on the western shore of the Sea of Japan (East Sea) on the flow of cold-air coming from the interior during winter cold-air outbreaks. The flow was modeled using a rotating 1-12 shallow-layer model. We consider two cases in detail: a layer constrained to follow the valley north of Vladivostok, the only direct access to the ocean, and a thicker layer able to flow over the coastal range as well. Several interesting phenomena emerge, related to the transition to supercritical flow near topographic features. It is shown that the flow along the Vladivostok valley will detach from the eastern side of the channel to form a jet aligned with the coast southwest of the opening. For the flow over the range, we were able to reproduce some of the features observed from satellite scatterometer wind measurements, such as the wakes (vortex street) in the lee of peaks along the range. Our model supports the existence of a heat-flux center for the formation of deep water southeast of Vladivostok during outbreaks only when the layer is thicker than the coastal range.