A Study of the Variability of the Coastal Marine Atmospheric Boundary Layer
Abstract
Different processes influence the coastal meteorology on different space and time scales. The interaction between coastal baroclinicity, background (synoptic scale) flow, coastal terrain and coastline geometry are believed to be important. The coastal baroclinicity is important for the diurnal cycle of the coastal jet, but also generates cross-shore flow in gaps where the terrain height is lower. If the terrain is higher than the top of the PBL depth, the flow becomes semi-bounded and geostrophic adjustment is impaired. If the flow is super-critical, information on changes in the pressure field caused by the geometry of the coast cannot propagate upstream. The flow responds with expansion fans and hydraulic jumps to such changes. The strength and direction of the background flow determine to some degree the location and strength of such mesoscale flows. Marine stratocumulus are important in that they enhance turbulent mixing and thus deepens the PBL. This affects coastal jets, since they are driven by the slope of the capping inversion. The interaction between the jet and changes in the coastal terrain may also modify the coastal MABL so that the cloud field is perturbed. The spatial variability of the flow generates horizontal gradients in the momentum transfer to the ocean. This results in up- and downwelling of cold water, changing the sea surface temperature (SST). The new SST distribution may, or may not, feed back to the atmospheric flow. The non-linear interaction between all these processes is responsible for the observed complexity of coastal flows, and our objective is to determine their relative importance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1998
- Accession Number
- ADA534819
Entities
People
- Michael Tjernström
Organizations
- Uppsala University