Frontal Structures in the Columbia River Plume Nearfield-A Non-Hydrostatic Coastal Modeling Study
Abstract
Abstract: In a coastal zone where fresh riverine water meets salty seawater, such as in a river mouth, flow structures can be highly complex and unpredictable due to density stratification and flow instabilities. For riverine outflow that is also modulated by tides, the frontal zone, defined here as the sharp transition between freshwater and seawater (salt wedge), is highly dynamics both spatially and temporally. Various flow structures manifesting the sharp transition of flow properties (e.g., salinity) at different scales, such as upwelling/downwelling, internal hydraulic jumps, internal waves and shear instabilities are generated. These flow structures can alter acoustic wave propagation (e.g., Reeder 2014) and the enhanced mixing and turbidity can scatter light and affect water clarity. Some of these flow structures are sufficiently intense to impact navigation safety but in the meantime, they can leave unique surface signatures which can be detected by remote sensing imagery. Hence, studying frontal dynamics is of high naval relevance as well as of civilian interests. The goal of the proposed work is to develop a robust nonhydrostatic coastal modeling system to study and predict the frontal structures of tide-modulated river outflows, mixing and turbidity in stratified and wave-dominated river mouths. Specifically, in the proposed two-year duration, we like to focus on the following three objectives: (1) To continue the non-hydrostatic numerical investigation of resolving frontal structures and the resulting surface signatures at the mouth of the Columbia river (MCR) using NHWAVE and compare/validate the model results with remote-sensing and in-situ data as part of the RIVET III and DARLA MURI projects. (2) To carry out more comprehensive NHWAVE model validation and analysis for frontal structures using field data obtained in September 2014 and newly planned field campaigns in 2015 and 2016. (3) To investigate the performance and sensitivity of different sub-grid closure schemes in NHWAVE to effectively resolve various flow structures in the fontal zone.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512612
Entities
People
- Tian-jian Hsu
Organizations
- Office of Naval Research
- United States Navy
- University of Delaware