A three-dimensional hydrostatic model has been employed to simulate thermal circulations in a coastal region. The model has been given topography and surface heating, in order to describe the conditions at Blekinge, a coastal region in southern Sweden. The influences of topography and direction of the large-scale wind on thermal circulations have been investigated, in particular, the effects on development and occurrence of sea-breeze and coastal jet.
The area can roughly be divided into two perpendicular coast-sections, the Kalmar coast and the Blekinge coast. The circulations at those coasts have been of primary interest in the investigation.
Many of the results obtained, are related to the frequently occurring sea-breeze. For all the four wind directions, sea-breeze events were found to occur. The location of the observed sea-breezes were different for the different wind directions. In almost every sea-breeze event, there were other forcing factors involved in the forming of the actual shape and intensity than the differential heating. An example of this, is the eddy formation during the northerly wind. The sea-breezes were all of individual strength and extension, some of the observed sea-breezes showed many of the characteristic features, while others were merely a perturbation due to thermal forcing. The overall observation in the sea-breeze sense, is that the circulations are mainly determined by the topography and topographical induced flows. The area of most complex nature and largest influence were found to be in the surroundings of the intersection point between the two coasts.
Two coastal jets have been observed in this investigation. The location of their formation was for both cases the channel between the Kalmar coast and the island Öland. Coastal jets occurred when the large-scale wind was perpendicular to the channel. During the Westerly wind a southerly jet was formed around 08.00 (LST), with a maximum velocity of the magnitude ~4.5 m/s. During the easterly wind a northerly jet, of the magnitude ~6 m/s was formed at 02.00. The cause of the jets are probably a combined effect of many origins. Thermal wind reduced the wind speed above the jet, and turbulence was transferring momentum down to the surface.
The complexity of the flows in coastal areas is clearly established. The thermal perturbations are strong in these areas and the result of this thermal forcing takes on a broad variety of shapes
1995. , p. 32