Tales of two UnTrim Applications:

Title: Tales of two UnTrim Applications: A 3D River Plume over the Continental Shelf and Wind Driven Circulation in Upper Klamath Lake, OregonSpeaker: Dr. Ralph T. Cheng, U.S. Geological Survey, Menol Park, CAAbstract:Two recent applications of the UnTRIM model are presented. (A) River derived fresh water discharging into the adjacent continental shelf forms a trapped river plume that propagates in a narrow region along the coast. The physics associated with the formation of river plumes spans a wide range of vertical and horizontal length scales. A proper description of the dynamics of river plume cannot be achieved without a realistic representation of the flow and salinity structure near the river mouth that controls the initial formation and propagation of the plume in the coastal ocean. The tidal dynamics near the river mouth shows that the ebb flow regime can be represented by a jet-like flow and a sink-like flow during flood. Strong exiting momentum in the jet-like flow being forced by Coriolis acceleration creates the initial formation of the river plume. During flooding cycle, the momentum is more evenly distributed; there is not a dominant preferred direction of freshwater. The complete river/estuary and coastal ocean system is simulated using the unstructured grid UnTRIM model. The simulations are carried out in tidal dynamics time-scales extending the simulations to cover processes in residual time-scales. The uniquely important role of Coriolis acceleration is shown. The results of this investigation show properties of the river plume and the tidal and residual characteristics of flow and salinity within the estuary; they are completely consistent with the physics of estuary and coastal ocean. (B) Wind-driven circulation in Upper Klamath Lake plays an important role determining the water quality and the health of the lake ecosystem. Time-series of water velocity measured by two ADCPs were collected in the summer of 2003. Strong correlations between the wind and circulation show clockwise circulation under prevailing wind (NW) and counterclockwise circulation as the wind shifted to SE. The UnTRIM model reproduced wind-driven circulation at a deep water station while the model results did not match observations at the shallow water station. The results of correlation analysis suggests that the ADCP time-series data at the shallow water station are suspect, which leads to the conclusion that field data must be analyzed to show consistency with the physics. When the data do not match the expected physics, there might be hidden messages in these data.

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