quick look at preliminary results
Movies from our most recent realistic CSIDE simulations on our finest grid (7 – 100 m horizontal resolution) covering the coastline of the US/Mexico border region for July 2015 can be seen here. These simulations are 2-way coupled wave-hydrodynamic simulations with fully realistic oceanic and atmospheric forcing (see additional details below). Please note that these are hot off the presses and are currently undergoing validation and improvements. As these are still preliminary simulations, please do not share with others. Please contact Falk Feddersen or Sarah Giddings with any questions about the simulations.
Sea surface conditions (below)
Depth-integrated passive tracer simulations at 3 known hotspots for pollution (below). Tracers are released from the point sources at realistic flow rates (~25 MGD) and with initial concentrations of 1. Thus the colorbar can be interpreted as the % of tracer remaining (0.01 = 1%). For example, during the period of strongest southerly swell during this simulation period, on 20 July, 2015 (see Figure below the movie), moderate waves from the S-SW drive northward alongshore surfzone currents and tracer from Pt. Bandera reaches Imperial Beach and Coronado coastlines at concentrations >1% of the source. Concentrations along parts of the Mexican coast are >10% of the input concentration, decreasing slowly and remaining >4% near the international border.
Snapshot from 20 July 2015 (above) with moderate waves from the S-SW driving significant northward transport of the tracers, particularly those released at the shoreline. The black star indicates the tracer release location and the dye is plotted on a logarithmic scale of the % of the initial concentrations. Predominant offshore wave direction is indicated on the second panel with wave heights.
More about the model
The model is developed within the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) framework (Warner et al., 2010) utilizing both the hydrodynamic module and wave module. The hydrodynamic module utilizes the Regional Ocean Modeling System (ROMS) (Shchepetkin and McWilliams, 2005), a free surface, hydrostatic, primitive equation model which is coupled to the wave model, Simulating Waves in the Nearshore (SWAN) (Booij et al., 1999), a wave-averaged spectral wave model. The COAWST model has recently be shown to well represent ocean dynamics from the surfzone across the shelf (e.g., Kumar et al. 2012, 2015, 2016) and also in estuaries (Ganju et al., 2017) and tidal outlets (Olabarrieta et al., 2014).
CSIDE simulation domains
The model domains (see left figure above) encompass a series of 1-way nested rectangular grids starting at the coarsest resolution (LV1) telescoping in to the highest resolution (LV4). The highest resolution LV4 grid (right figure above) covers the region from Pt. Loma, San Diego Bay, down the coast to Baja Malibu, MX at variable horizontal grid resolution from 100 to 7 m with 15 vertical levels and includes the 3 main pollution point sources for the region.
CSIDE simulation forcing
Forcing for all domains is realistic. LV1 is initialized with and forced at the open ocean boundary using solutions from the data assimilative, realistic, MITgcm California State Estimate (CASE, http://www.ecco.ucsd.edu/case.html), which has 7 km resolution and covers most of the CA Current System. Open boundary conditions for each subsequent level is then applied from the coarser resolution (i.e., LV1 solutions are used to force LV2). Surface atmospheric forcing for all grids use the NOAA North American Mesoscale Forecast System Hindcast (NAM) with data gaps interpolated with U.S. Navy Fleet Numerical high resolution Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) atmospheric variables. Tidal constituent amplitude and phase are extracted from ADCIRC (http://adcirc.org/products/adcirc-tidal-databases/) and imposed at the LV1 boundary. Finally, wave information from the CDIP Monitoring and Prediction system (MOP – which uses CDIP buoys and a linear model) have been extracted at the LV4 boundary and are used as boundary conditions for the LV4 wave model.
CSIDE simulation validation