Labs WMT ROMSLIte RiverForcing

Introduction to Regional Ocean Modeling - River Forcing-flood and drought conditions

This lab has been designed and developed by Courtney Harris, Julia Moriarty, Danielle Tarpley, Virginia Institute of Marine Sciences, Gloucester Point, VA
with assistance of Irina Overeem, CSDMS, University of Colorado, CO

Classroom organization
This lab is the fourth in a series of introduction to the Regional Ocean Modeling System (ROMS) for inexperienced users. ROMS is a three-dimensional hydrodynamic ocean model (see Haidvogel et al. 2008; myroms.org). ROMS solves the conservation of mass and three-dimensional momentum equations and includes transport equations for temperature and salinity. The version implemented here also accounts for suspended sediment transport and deposition, following Warner et al. (2008). Here we present a basic configuration of ROMS in the framework of the Web Modeling Tool (WMT). This series of labs is designed for inexperienced modelers to gain some experience with running a numerical model, changing model inputs, and analyzing model output. The example provided looks at the influence of a river plume on the hydrodynamics and sediment transport within an idealized continental shelf. This fourth lab will compare the effect of river flood conditions with low river water or drought conditions.
This lab will likely take ~ 3hours to complete in the classroom.
If you have never used the Web Modeling Tool, learn how to use it here. The WMT allows you to set up simulations, but once you are ready to run them, you will need an account on the CSDMS supercomputer to submit your job. More information on getting an account can be found here HPCC Access. Note that getting permission for access takes a few days after your application.

Learning objectives

Skills

• compare simulation output for several configurations of the Regional Ocean Modeling System
• hands-on experience with visualizing NetCDF output with Matlab or Panoply.

Topical learning objectives

• learn about the impact of river conditions on the nearshore environment
• explore river flood deposition versus drought conditions deposition

Lab Notes

>> Open a new browser window and open the Web Modeling Tool here and select the ROMS project
>> This WMT project is unique in that there is only a single driver, ROMS-Lite. It is a pre-compiled instance of the larger ROMS system specially configured for teaching use.

You are now familiar with the basic river plume numerical experiment. Sofar, we have kept river discharge constant over the duration of the simulation at 1500 m3/sec. In these experiments we will drastically increase and reduce river discharge in different simulations and investigate the effects of fluvial forcing on the plume and nearshore deposition.

>> Set up a configuration for a river in flood, the discharge at 2000 m3/sec, and with high sediment concentration. We will run the river flood for 96 hours (this simulation still takes only a few minutes to run). Download the zip file with your simulation output from the run status window

The ocean_riverplume2.nc file has bundled all important output. Typically the tracer quantities, like salinity and suspended sediment concentration, can be plotted as a 2D plot of eta-rho (x-axis) and xhi_rho (y-axis).

Plot a stack of planview maps of salinity, how far out offshore does the river plume still affect the ocean conditions? Until what depth is salinity noticeably affected?

This feature is a coast-hugging plume, or also called a 'surface trapped plume'. Why? Do you know of real-world  examples of coast-hugging plumes? 

>> Set up an additional WMT ROMS-Lite simulation for the same river and ocean conditions, but double the suspended sediment concentrations. Run this simulation and download the output.

Plot plan view maps of the final time slice for the mud001 concentration, do this both for our 'base case' as well as for the 'high concentration' simulation. How do the two results differ from each other? Does a river plume with a higher sediment concentration travel further out offshore? What do you think controls this distance?

References and More information

• The regional oceanic modeling system (ROMS): a split-explicit, free-surface, topography-following-coordinate oceanic model, A. F. Shchepetkin, J. C. McWilliams, Ocean Modelling 9 (2005) 347–404
• Much more information on ROMS community help pages
• Arakawa, A.; Lamb, V.R. (1977). "Computational design of the basic dynamical processes of the UCLA general circulation model". Methods of Computational Physics 17. New York: Academic Press. pp. 173–265.