Validation of the nonhydrostatic General Curvilinear Coastal Ocean Model (GCCOM) for stratified flows

While global- and basin-scale processes can be captured quite well with computationally-inexpensive hydrostatic models, smaller-scale features such as shoaling nonlinear internal waves and bores, coastal fronts, and other convective processes require the use of a nonhydrostatic model to accurately capture dynamics. Here the nonhydrostatic capabilities of the General Curvilinear Coastal Ocean Model (GCCOM) in a stratified environment are introduced. GCCOM is a three-dimensional, nonhydrostatic Large Eddy Simulation (LES), rigid lid model that has the ability to run in a fully three-dimensional general curvilinear coordinate system. This model was previously validated for unstratified flows with curvilinear coordinates. Here, recent advances of the model to simulate stratified flows are presented, focusing on sigma coordinate grids with both flat bottom geometry and a local gently sloping seamount. In particular, a suite of test cases widely used as benchmarks for assessing the nonhydrostatic capabilities for gravity-driven flows and internal waves is presented: an internal seiche in a flat bottom tank, the classic lock release and gravity current experiment, and a field-scale internal wave beam experiment consisting of an oscillating tidal flow over a topographic ridge. GCCOM shows excellent agreement with the benchmark test cases and is able to accurately resolve complex nonhydrostatic phenomena in stratified flows. Future studies will utilize the model capabilities for realistic field-scale internal wave simulations

Mimetic Coastal Ocean Modeling In General Coordinates And Using Machine Learning Based Predictions

Nonlinear internal waves are a ubiquitous and fundamental aspect of the coastal ecosystem understanding. However, they rely on extreme geographical conditions and precise dimensional equilibrium to be captured accurately. The General Curvilinear Coastal Ocean Model (GCCOM) was validated, serial and parallel versions for a set of experiments showcasing stratified and non-hydrostatic flow phenomena. Still, the 3D curvilinear capability has proven to be elusive. We apply cutting-edge numerical methods to improve upon the previously validated GCCOM, elevating it to field-scale capacity. This reformulation of the GCCOM equations uses novel 3D curvilinear mimetic operators, a buoyancy body force, and mimetic upwind and gradient-based momentum equations developed for this work. This model represents the most complete implementation of the 3D curvilinear mimetic operators utilizing the MOLE library or any other mimetic applications in literature to date. Results show it to be more physically accurate and better energy conserving than the validated GCCOM and other similar models, permitting the use of 3D curvilinear grids for arbitrary geometries, parallelizable arbitrary domain decomposition, and order-of-magnitude wider time steps. Additionally, we implement machine learning models to coastal ocean data to predict Dissolved Oxygen (DO) content with supervised methods; results show a Median Absolute Percentage Error (MAPE) of 2-6% for instantaneous indirect readings of DO and 0.18% for five days forecast of DO in coastal areas, using a previously predicted temperature of 1.60% MAPE. Dissolved Oxygen is known to be a critically important component to track in coastal environments but also expensive to measure and almost impossible to model with traditional methods due to high nonlinearity. The ML component of this thesis opens the possibility of high precision indirect estimates of biogeochemical quantities, along with highly accurate time series forecasts and a host of new applications of machine learning to environmental sciences

Multiscale, Multiphysics Modelling of Coastal Ocean Processes: Paradigms and Approaches

This Special Issue includes papers on physical phenomena, such as wind-driven flows, coastal flooding, and turbidity currents, and modeling techniques, such as model comparison, model coupling, parallel computation, and domain decomposition. These papers illustrate the need for modeling coastal ocean flows with multiple physical processes at different scales. Additionally, these papers reflect the current status of such modeling of coastal ocean flows, and they present a roadmap with numerical methods, data collection, and artificial intelligence as future endeavors

CAL POLY PIER MASTER PLAN

The Cal Poly Pier (Pier) Master/Facility Plan (FP) document provides the vision of the future for the Pier, a marine science research facility. The Plan facilitates project development and management of the Pier while meeting university and department research goals. Specifically, the FP document establishes goals and strategies to direct long-term development of the Pier, streamlines agency approval and permit requirements, provides context for pier management, and assists the permitting process for future development as it relates to regulatory permits and programmatic growth on the Cal Poly Pier to help meet goals of the Center for Coastal Marine Sciences (CCMS). The Cal Poly Pier is the marine field station for the California Polytechnic State University San Luis Obispo (Cal Poly) CCMS and is one of several facilities that supports research and educational activities. The CCMS is a CSU Campus Center research organization that provides research and education activities as a part of Cal Poly’s overall mission while offering opportunities to interested parties beyond Cal Poly, such as private and public entities. The 3,057-foot long pier provides students, faculty, researchers, and other users unrivaled access to the marine environment of the Central Coast and fosters hands-on learning opportunities to progress marine research and science. The Master Plan name was changed to Facility Plan to streamline the plan approval process and to minimize the potential for errors

Simulating Wintertime Lake Dynamics Using the MITgcm Ice Model

Lake Erie is an important source of drinking water, a location for recreational activities and a haven for unique ecosystems (e.g. Point Pelee). Recent research has suggested that some wintertime processes are significantly increasing amounts of hypoxic water and harmful algal blooms found in the lake during the following summer. Much of the mixing in Lake Erie is caused by wind forcing. Mixing also occurs via an unstable water column that results from incoming solar radiation when water is below the temperature (around 4 degrees) at which the maximum density occurs. This thesis reports on several highly idealized lake ice simulations using MITgcm (Massachusetts Institute of Technology General Circulation Model). The MITgcm is a 3D ocean model with the ability to model sea ice that was specifically chosen for this work because of its fully nonhydrostatic capabilities. This work was carried out with the intention of gaining a clear understanding of the MITgcm and some of its packages so that the model may be confidently applied to future work involving Lake Erie. In this thesis, we consider small rectangular lakes with a partial ice cover of constant thickness. We vary several parameter settings for our simulations including initial surface temperature, air temperature, incoming shortwave and longwave radiation, wind forcing, rotation, horizontal domain size, and horizontal resolution. We also carry out simulations using the fully nonhydrostatic version of the MITgcm as well as simulations using hydrostatic approximation. Results from this work suggests that the ice cover acts as a barrier between the wind forcing and the surface of the lake. We observe that the surface currents are generally much weaker in ice-covered regions. Applying the hydrostatic approximation results in less symmetry among the surface currents. Lakes with larger horizontal domains require more time to force a proportional amount of ice across the lake compared to smaller lakes under similar forcing, there is also less ice pile-up observed in the larger lake in terms of height. Rotation also appears to have more influence over larger lakes compared to smaller lakes. Overall, the simulations behave as expected, however some results have been puzzling, such as noise occurring in the net upward heat flux for larger lakes. This thesis also discusses issues we have faced with the model, which includes ice growth during above freezing temperatures, ice remaining stagnant due to strange behaviour of momentum solvers, and confusion surrounding the model's computation of net upward shortwave radiation