Development, implementation, and validation of a California coastal ocean modeling, data assimilation, and forecasting system

A three-dimensional, near real-time data-assimilative modeling system for the California coastal ocean is presented. The system consists of a Regional Ocean Modeling System (ROMS) forced by the North American Mesoscale Forecast System (NAM). The ocean model has a horizontal resolution of approximately three kilometers and utilizes a multi-scale three-dimensional variational (3DVAR) data assimilation methodology. The system is run in near real-time to produce a nowcast every six hours and a 72-hour forecast every day. The performance of this nowcast system is presented using results from a six-year period of 2009–2015. The ROMS results are first compared with the assimilated data as a consistency check. RMS differences in observed satellite infrared sea surface temperatures (SST) and vertical profiles of temperature between observations and ROMS nowcasts were found to be mostly less than 0.5 °C, while the RMS differences in vertical profiles of salinity between observations and ROMS nowcasts were found to be 0.09 or less. The RMS differences in SST show a distinct seasonal cycle that mirrors the number of observations available: the nowcast is less skillful with larger RMS differences during the summer months when there are less infrared SST observations due to the presence of low-level clouds. The larger differences during summer were found primarily along the northern and central coasts in upwelling regions where strong gradients exist between colder upwelled waters nearshore and warmer offshore waters. RMS differences between HF radar surface current observations and ROMS nowcasts were approximately 7–8 cm s−1, which is about 30% of the time mean current speeds in this region. The RMS differences in sea surface height (SSH) between the AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic) altimetric satellite observations and ROMS nowcasts were about 2 cm. In addition, the system realistically reproduces the interannual variability in temperatures at the M1 mooring (122.03°W, 36.75°N) in Monterey Bay, including the strong warming of the California coastal ocean during 2014. The ROMS nowcasts were then validated against independent observations. A comparison of the ROMS nowcast with independent profile observations of temperature and salinity shows RMS differences of 0.7 to 0.92 °C and 0.13 to 0.17, which are larger (by up to a factor of 2) than the differences found in the comparisons with assimilated data. Validation of the depth-averaged currents derived from Spray gliders shows that the flow patterns associated with California Current and California Undercurrent/Davidson current systems and their seasonal variations are qualitatively reproduced by the ROMS modeling system. Lastly, the impact of two recent upgrades to the system is quantified. Switching the lateral boundary conditions from a U.S. west coast regional model to the global HYCOM (HYbrid Coordinate Ocean Model) model results in an improvement in the simulation of the seasonal and interannual variations in the SSH, especially south of Pt. Conception (120.47°W, 34.45°N). The assimilation of altimetric satellite SSH data also results in an improvement in the model surface currents when compared to independent surface drifter observations

The Coupled Model Intercomparison Project (CMIP)

The Coupled Model Intercomparison Project (CMIP) was established to study and intercompare climate simulations made with coupled ocean-atmosphere-cryosphere-land GCMs. There are two main phases (CMIP1 and CMIP2), which study, respectively, 1) the ability of models to simulate current climate, and 2) model simulations of climate change due to an idealized change in forcing (a 1% per year CO2 increase). Results from a number of CMIP projects were reported at the first CMIP Workshop held in Melbourne, Australia, in October 1998. Some recent advances in global coupled modeling related to CMIP were also reported. Presentations were based on preliminary unpublished results. Key outcomes from the workshop were that 1) many observed aspects of climate variability are simulated in global coupled models including the North Atlantic oscillation and its linkages to North Atlantic SSTs, El Niño-like events, and monsoon interannual variability; 2) the amplitude of both high- and low-frequency global mean surface temperature variability in many global coupled models is less than that observed, with the former due in part to simulated ENSO in the models being generally weaker than observed, and the latter likely to be at least partially due to the uncertainty in the estimates of past radiative forcing; 3) an El Niño-like pattern in the mean SST response with greater surface warming in the eastern equatorial Pacific than the western equatorial Pacific is found by a number of models in global warming climate change experiments, but other models have a more spatially uniform or even a La Niña-like, response; 4) flux adjustment, by definition, improves the simulation of mean present-day climate over oceans, does not guarantee a drift-free climate, but can produce a stable base state in some models to enable very long term (1000 yr and longer) integrations-in these models it does not appear to have a major effect on model processes or model responses to increasing CO2; and 5) recent multicentury integrations show that a stable surface climate can be attained without flux adjustment (though still with some systematic simulation errors)

Production of a High-Level Waste Glass from Hanford Waste Samples

The HLW glass was produced from a HLW sludge slurry (Envelope D Waste), eluate waste streams containing high levels of Cs-137 and Tc-99, solids containing both Sr-90 and transuranics (TRU), and glass-forming chemicals. The eluates and Sr-90/TRU solids were obtained from ion-exchange and precipitation pretreatments, respectively, of other Hanford supernate samples (Envelopes A, B and C Waste). The glass was vitrified by mixing the different waste streams with glass-forming chemicals in platinum/gold crucibles and heating the mixture to 1150 degree C. Resulting glass analyses indicated that the HLW glass waste form composition was close to the target composition. The targeted waste loading of Envelope D sludge solids in the HLW glass was 30.7 wt percent, exclusive of Na and Si oxides. Condensate samples from the off-gas condenser and off-gas dry-ice trap indicated that very little of the radionuclides were volatilized during vitrification. Microstructure analysis of the HLW glass using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX) showed what appeared to be iron spinel in the HLW glass. Further X-Ray Diffraction (XRD) analysis confirmed the presence of nickel spinel trevorite (NiFe2O4). These crystals did not degrade the leaching characteristics of the glass. The HLW glass waste form passed leach tests that included a standard 90 degree C Product Consistency Test (PCT) and a modified version of the United States Environmental Protection Agency Toxicity Characteristic Leaching Procedure (TCLP)

Station-Keeping Underwater Gliders Using a Predictive Ocean Circulation Model and Applications to SWOT Calibration and Validation

Instrumented ocean moorings are the gold standard for gathering in situ measurements at a fixed location in the ocean. Because they require installation by a ship and must be secured to the seafloor, moorings are expensive, logistically difficult to deploy and maintain, and are constrained to one location once installed. To circumvent these issues, previous studies have attempted to utilize autonomous underwater gliders as platforms for virtual moorings, but these attempts have yielded comparatively large station-keeping errors due to the difficulty of glider control in dynamic ocean currents. We implemented an adaptive planner using a vehicle motion model and a predictive ocean circulation model to improve station-keeping performance by incorporating anticipated currents into glider control. We demonstrate improved station-keeping performance using our planner in both simulation and in-field deployment results, and report smaller average station-keeping error than the Monterey Bay Aquarium Research Institute's M1 mooring. Finally, we utilize our simulation framework to conduct a feasibility study on using an array of autonomous gliders as virtual moorings to conduct critical calibration and validation (CalVal) for the upcoming National Aeronautics and Space Administration, Surface Water and Ocean Topography (SWOT) Mission, instead of using permanent moorings. We show that this approach carries several advantages and has potential to meet the SWOT CalVal objectives

Station-Keeping Underwater Gliders Using a Predictive Ocean Circulation Model and Applications to SWOT Calibration and Validation

Instrumented ocean moorings are the gold standard for gathering in situ measurements at a fixed location in the ocean. Because they require installation by a ship and must be secured to the seafloor, moorings are expensive, logistically difficult to deploy and maintain, and are constrained to one location once installed. To circumvent these issues, previous studies have attempted to utilize autonomous underwater gliders as platforms for virtual moorings, but these attempts have yielded comparatively large station-keeping errors due to the difficulty of glider control in dynamic ocean currents. We implemented an adaptive planner using a vehicle motion model and a predictive ocean circulation model to improve station-keeping performance by incorporating anticipated currents into glider control. We demonstrate improved station-keeping performance using our planner in both simulation and in-field deployment results, and report smaller average station-keeping error than the Monterey Bay Aquarium Research Institute's M1 mooring. Finally, we utilize our simulation framework to conduct a feasibility study on using an array of autonomous gliders as virtual moorings to conduct critical calibration and validation (CalVal) for the upcoming National Aeronautics and Space Administration, Surface Water and Ocean Topography (SWOT) Mission, instead of using permanent moorings. We show that this approach carries several advantages and has potential to meet the SWOT CalVal objectives