Science.gov

Sample records for ocean model simulation

  1. Tidal simulation using regional ocean modeling systems (ROMS)

    NASA Technical Reports Server (NTRS)

    Wang, Xiaochun; Chao, Yi; Li, Zhijin; Dong, Changming; Farrara, John; McWilliams, James C.; Shum, C. K.; Wang, Yu; Matsumoto, Koji; Rosenfeld, Leslie K.; Paduan, Jeffrey D.

    2006-01-01

    The purpose of our research is to test the capability of ROMS in simulating tides. The research also serves as a necessary exercise to implement tides in an operational ocean forecasting system. In this paper, we emphasize the validation of the model tide simulation. The characteristics and energetics of tides of the region will be reported in separate publications.

  2. Simulating aggregate dynamics in ocean biogeochemical models

    NASA Astrophysics Data System (ADS)

    Jackson, George A.; Burd, Adrian B.

    2015-04-01

    The dynamics of elements in the water column is complex, depending on multiple biological and physical processes operating at very different physical scales. Coagulation of particulate material is important for transforming particles and moving them in the water column. Mechanistic models of coagulation processes provide a means to predict these processes, help interpret observations, and provide insight into the processes occurring. However, most model applications have focused on describing simple marine systems and mechanisms. We argue that further model development, in close collaboration with field and experimental scientists, is required in order to extend the models to describe the large-scale elemental distributions and interactions being studied as part of GEOTRACES. Models that provide a fundamental description of trace element-particle interactions are required as are experimental tests of the mechanisms involved and the predictions arising from models. However, a comparison between simple and complicated models of aggregation and trace metal provides a means for understanding the implications of simplifying assumptions and providing guidance as to which simplifications are needed.

  3. Arctic Ocean Freshwater: How Robust are Model Simulations

    NASA Technical Reports Server (NTRS)

    Jahn, A.; Aksenov, Y.; deCuevas, B. A.; deSteur, L.; Haekkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; Lique, C.; Nguyen, A.; Pemberton, P.; Worthen, D.; Zhang, J.

    2012-01-01

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.

  4. Arctic Ocean freshwater: How robust are model simulations?

    NASA Astrophysics Data System (ADS)

    Jahn, A.; Aksenov, Y.; de Cuevas, B. A.; de Steur, L.; Häkkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; Lique, C.; Nguyen, A.; Pemberton, P.; Worthen, D.; Zhang, J.

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.

  5. Variability and trends in Southern Ocean eddy activity in 1/12° ocean model simulations

    NASA Astrophysics Data System (ADS)

    Patara, Lavinia; Böning, Claus W.; Biastoch, Arne

    2016-05-01

    The response of eddy kinetic energy (EKE) to the strengthening of Southern Hemisphere winds occurring since the 1950s is investigated with a global ocean model having a resolution of 1/12° in the Antarctic Circumpolar Current domain. The simulations expose regional differences in the relative importance of stochastic and wind-related contributions to interannual EKE changes. In the Pacific and Indian sectors the model captures the EKE variability observed since 1993 and confirms previous hypotheses of a lagged response to regional wind stress anomalies. Here the multidecadal trend in wind stress is reflected in an increase in EKE typically exceeding 5 cm2 s-2 decade-1. In the western Atlantic, EKE variability is mostly stochastic, is weakly correlated with wind fluctuations, and its multidecadal trends are close to zero. The nonuniform distribution of wind-related changes in the eddy activity could affect the regional patterns of ocean circulation and biogeochemical responses to future climate change.

  6. Sensitivity of ocean model simulation in the coastal ocean to the resolution of the meteorological forcing

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Shapiro, Georgy; Thain, Richard

    2013-04-01

    The quality of ocean simulations depends on a number of factors such as approximations in governing equations, errors introduced by the numerical scheme, uncertainties in input parameters, and atmospheric forcing. The identification of relations between the uncertainties in input and output data is still a challenge for the development of numerical models. The impacts of ocean variables on ocean models are still not well known (e.g., Kara et al., 2009). Given the considerable importance of the atmospheric forcing to the air-sea interaction, it is essential that researchers in ocean modelling work need a good understanding about how sensitive the atmospheric forcing is to variations of model results, which is beneficial to the development of ocean models. Also, it provides a proper way to choose the atmospheric forcing in ocean modelling applications. Our previous study (Shapiro et al, 2011) has shown that the basin-wide circulation pattern and the temperature structure in the Black Sea produced by the same model is significantly dependent on the source of the meteorological input, giving remarkably different responses. For the purpose of this study we have chosen the Celtic Sea where high resolution meteo data are available from the UK Met office since 2006. The Celtic Sea is tidally dominated water basin, with the tidal stream amplitude varying from 0.25m/s in the southwest to 2 m/s in the Bristol Channel. It is also filled with mesoscale eddies which contribute to the formation of the residual (tidally averaged) circulation pattern (Young et al, 2003). The sea is strongly stratified from April to November, which adds to the formation of density driven currents. In this paper we analyse how sensitive the model output is to variations in the spatial resolution of meteorological using low (1.6°) and high (0.11°) resolution meteo forcing, giving the quantitative relation between variations of met forcing and the resulted differences of model results, as well as

  7. Ocean Dynamics Simulation during an Extreme Bora Event using a Two-Way Coupled Atmosphere-Ocean Modeling System

    NASA Astrophysics Data System (ADS)

    Licer, Matjaz; Smerkol, Peter; Fettich, Anja; Ravdas, Michalis; Papapostolou, Alexandros; Mantziafou, Anneta; Cedilnik, Jure; Strajnar, Benedikt; Jeromel, Maja; Pristov, Neva; Jerman, Jure; Petan, Saso; Malacic, Vlado; Sofianos, Sarantis

    2015-04-01

    The response of the Adriatic Sea to cold north-easterly Bora wind forcing has been modelled numerous times, but usually using one-way coupling techniques. One of the most significant events of the kind took place in February 2012, when hurricane force Bora was blowing over the Northern Adriatic almost continuously for over three weeks, causing extreme air-sea interactions leading to severe water cooling (below 4 degrees Celsius) and extensive dense water formation (with density anomalies above 30.5 kg/m3). The intensity of the atmosphere-ocean interactions during such conditions calls for a two-way atmosphere-ocean coupling approach. We compare the performances of a) fully two-way coupled atmosphere-ocean modelling system and b) one way coupled ocean model (forced by the atmospheric model hourly output) to the available in-situ measurements (coastal buoy, CTD). The models used were ALADIN (4.4 km resolution) on the atmospheric side and POM (1/30°× 1/30° resolution) on the ocean side. The atmosphere-ocean coupling was implemented using the OASIS3-MCT model coupling toolkit. We show that the atmosphere-ocean two-way coupling significantly improves the simulated temperature and density response of the ocean since it represents short-termed transient features much better than the offline version of the ocean model.

  8. Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model

    SciTech Connect

    Murtugudde, R.; Seager, R.; Busalacchi, A.

    1996-08-01

    A reduced gravity, primitive equation, ocean general circulation model (GCM) is coupled to an advective atmospheric mixed-layer (AML) model to demonstrate the importance of a nonlocal atmospheric mixed-layer parameterization for a proper simulation of surface heat fluxes and sea surface temperatures (SST). Seasonal variability of the model SSTs and the circulation are generally in good agreement with the observations in each of the tropical oceans. These results are compared to other simulations that use a local equilibrium mixed-layer model. Inclusion of the advective AML model is demonstrated to lead to a significant improvement in the SST simulation in all three oceans. Advection and diffusion of the air humidity play significant roles in determining SSTs even in the tropical Pacific where the local equilibrium assumption was previously deemed quite accurate. The main, and serious, model flaw is an inadequate representation of the seasonal cycle in the upwelling regions of the eastern Atlantic and Pacific Oceans. The results indicate that the feedback between mixed-layer depths and SSTs can amplify SST errors, implying that increased realism in the modeling of the ocean mixed layer increases the demand for realism in the representation of the surface heat fluxes. The performance of the GCM with a local-equilibrium mixed-layer model in the Atlantic is as poor as previous simple ocean model simulations of the Atlantic. The conclusion of earlier studies that the simple ocean model was at fault may, in fact, not be correct. Instead the local-equilibrium heat flux parameterization appears to have been the major source of error. Accurate SST predictions may, hence, be feasible by coupling the AML model to computationally efficient simple ocean models. 69 refs., 18 figs., 1 tab.

  9. Cloud-radiative effects on implied oceanic energy transports as simulated by atmospheric general circulation models

    SciTech Connect

    Gleckler, P.J.; Randall, D.A.; Boer, G.

    1994-03-01

    This paper reports on energy fluxes across the surface of the ocean as simulated by fifteen atmospheric general circulation models in which ocean surface temperatures and sea-ice boundaries are prescribed. The oceanic meridional energy transport that would be required to balance these surface fluxes is computed, and is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean energy transport can be affected by the errors in simulated cloud-radiation interactions.

  10. Climate Simulations for 1951-2050 with a Coupled Atmosphere-Ocean Model.

    NASA Astrophysics Data System (ADS)

    Sun, Shan; Hansen, James E.

    2003-09-01

    The authors simulate climate change for 1951-2050 using the GISS SI2000 atmospheric model coupled to HYCOM, a quasi-isopycnal ocean model (`ocean E'), and contrast the results with those obtained using the same atmosphere coupled to a passive Q-flux ocean model (`ocean B') and the same atmosphere driven by observed SST (`ocean A'). All of the models give reasonable agreement with observed global temperature change during 1951-2000, but the quasi-isopycnal ocean E mixes heat more deeply and hence sequesters heat more effectively on the century timescale. Global surface warming in the next 50 yr is only 0.3°-0.4°C with this ocean in simulations driven by an `alternative scenario' climate forcing (1.1 W m2 in the next 50 yr), only half as much as with ocean B. From the different models the authors estimate that the earth was out of radiation balance by about 0.18 W m2 in 1951 and is now out of balance by about 0.75 W m2. This energy imbalance, or residual climate forcing, a consequence of deep ocean mixing of heat anomalies and the history of climate forcings, is a crucial measure of the state of the climate system that should be precisely monitored with full-ocean temperature measurements.

  11. MJO simulation in a cloud-system-resolving global ocean-atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Sasaki, Wataru; Onishi, Ryo; Fuchigami, Hiromitsu; Goto, Koji; Nishikawa, Shiro; Ishikawa, Yoichi; Takahashi, Keiko

    2016-09-01

    An observed Madden-Julian Oscillation (MJO) propagating from the central Indian Ocean to the western Pacific from 15 December 2006 to 10 January 2007 was successfully simulated by a cloud-system-resolving global ocean-atmosphere coupled model without parameterization of cumulus convection. We found that the ocean coupling has significant impacts on the MJO simulation, e.g., strength of the moisture convergence, and the timing and strength of the westerly wind burst over the Maritime Continent. The model also generally well simulated the decay of the MJO in the western Pacific, as well as the changes in sea surface temperature. These results demonstrate that the cloud-system-resolving global ocean-atmosphere coupled model can be used for realistic MJO simulation.

  12. Cloud-radiative effects on implied oceanic energy transports as simulated by atmospheric general circulation models

    SciTech Connect

    Gleckler, P.J.; Randall, D.A.; Boer, G.

    1995-04-01

    This paper summarizes the ocean surface net energy flux simulated by fifteen atmospheric general circulation models constrained by realistically-varying sea surface temperatures and sea ice as part of the Atmospheric Model Intercomparison Project. In general, the simulated energy fluxes are within the very large observational uncertainties. However, the annual mean oceanic meridional heat transport that would be required to balance the simulated surface fluxes is shown to be critically sensitive to the radiative effects to clouds, to the extent that even the sign of the Southern Hemisphere ocean heat transport can be affected by the errors in simulated cloud-radiation interactions. It is suggested that improved treatment of cloud radiative effects should help in the development of coupled atmospheric-ocean general circulation models. 16 refs., 3 figs.

  13. Cloud-radiative effects on implied oceanic energy transport as simulated by atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Gleckler, P. J.; Randall, D. A.; Boer, G.; Colman, R.; Dix, M.; Galin, V.; Helfand, M.; Kiehl, J.; Kitoh, A.; Lau, W.

    1995-01-01

    This paper summarizes the ocean surface net energy flux simulated by fifteen atmospheric general circulation models constrained by realistically-varying sea surface temperatures and sea ice as part of the Atmospheric Model Intercomparison Project. In general, the simulated energy fluxes are within the very large observational uncertainties. However, the annual mean oceanic meridional heat transport that would be required to balance the simulated surface fluxes is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean heat transport can be affected by the errors in simulated cloud-radiation interactions. It is suggested that improved treatment of cloud radiative effects should help in the development of coupled atmosphere-ocean general circulation models.

  14. Evaluation of Arctic Sea Ice Thickness Simulated by Arctic Ocean Model Intercomparison Project Models

    NASA Technical Reports Server (NTRS)

    Johnson, Mark; Proshuntinsky, Andrew; Aksenov, Yevgeny; Nguyen, An T.; Lindsay, Ron; Haas, Christian; Zhang, Jinlun; Diansky, Nikolay; Kwok, Ron; Maslowski, Wieslaw; Hakkinen, Sirpa; Ashik, Igor; De Cuevas, Beverly

    2012-01-01

    Six Arctic Ocean Model Intercomparison Project model simulations are compared with estimates of sea ice thickness derived from pan-Arctic satellite freeboard measurements (2004-2008); airborne electromagnetic measurements (2001-2009); ice draft data from moored instruments in Fram Strait, the Greenland Sea, and the Beaufort Sea (1992-2008) and from submarines (1975-2000); and drill hole data from the Arctic basin, Laptev, and East Siberian marginal seas (1982-1986) and coastal stations (1998-2009). Despite an assessment of six models that differ in numerical methods, resolution, domain, forcing, and boundary conditions, the models generally overestimate the thickness of measured ice thinner than approximately 2 mand underestimate the thickness of ice measured thicker than about approximately 2m. In the regions of flat immobile landfast ice (shallow Siberian Seas with depths less than 25-30 m), the models generally overestimate both the total observed sea ice thickness and rates of September and October ice growth from observations by more than 4 times and more than one standard deviation, respectively. The models do not reproduce conditions of fast ice formation and growth. Instead, the modeled fast ice is replaced with pack ice which drifts, generating ridges of increasing ice thickness, in addition to thermodynamic ice growth. Considering all observational data sets, the better correlations and smaller differences from observations are from the Estimating the Circulation and Climate of the Ocean, Phase II and Pan-Arctic Ice Ocean Modeling and Assimilation System models.

  15. Onset time and strength of oceanic deep convection diagnosed from an ocean large-eddy simulation model

    SciTech Connect

    Denbo, D.W.

    1995-01-01

    Deep convection has an important role in the large-scale thermohaline circulation, which in turn plays a central part in determining global climate. Manabe and Stouffer`s climate simulations have shown that the thermal and dynamic structure of the oceans have pronounced changes in model climates with increased CO{sub 2}. In their simulations, the addition of low-salinity surface water at high latitudes prevents the ventilation of the deep ocean, thus reducing or in some cases nearly extinguishing the thermohaline circulation. Siegenthaler and Sarmiento remarked that whereas the ocean is the largest of the rapidly exchanging global carbon reservoirs and a major sink for anthropogenic carbon, this uptake capacity become available only when the whole ocean is chemically equilibrated with the new atmospheric CO{sub 2} concentration. The dynamics of the oceanic uptake of CO{sub 2} is therefore strongly determined by the rate of downward transport of CO{sub 2}-laden water from surface to depth. The importance of deep convection in moderating the uptake of CO{sub 2} by the ocean and its role in the meridional circulation, which affects climate by transporting heat from the tropics to the polar regions, motivates this research. The experiments described here were designed to study the sensitivity of the onset time and strength of deep convection to changes in the heat flux, latent heat flux, and perturbations of the surface mixed-layer temperature and salinity.

  16. Ocean-Atmosphere Coupled Model Simulations of Precipitation in the Central Andes

    NASA Technical Reports Server (NTRS)

    Nicholls, Stephen D.; Mohr, Karen I.

    2015-01-01

    The meridional extent and complex orography of the South American continent contributes to a wide diversity of climate regimes ranging from hyper-arid deserts to tropical rainforests to sub-polar highland regions. In addition, South American meteorology and climate are also made further complicated by ENSO, a powerful coupled ocean-atmosphere phenomenon. Modelling studies in this region have typically resorted to either atmospheric mesoscale or atmosphere-ocean coupled global climate models. The latter offers full physics and high spatial resolution, but it is computationally inefficient typically lack an interactive ocean, whereas the former offers high computational efficiency and ocean-atmosphere coupling, but it lacks adequate spatial and temporal resolution to adequate resolve the complex orography and explicitly simulate precipitation. Explicit simulation of precipitation is vital in the Central Andes where rainfall rates are light (0.5-5 mm hr-1), there is strong seasonality, and most precipitation is associated with weak mesoscale-organized convection. Recent increases in both computational power and model development have led to the advent of coupled ocean-atmosphere mesoscale models for both weather and climate study applications. These modelling systems, while computationally expensive, include two-way ocean-atmosphere coupling, high resolution, and explicit simulation of precipitation. In this study, we use the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST), a fully-coupled mesoscale atmosphere-ocean modeling system. Previous work has shown COAWST to reasonably simulate the entire 2003-2004 wet season (Dec-Feb) as validated against both satellite and model analysis data when ECMWF interim analysis data were used for boundary conditions on a 27-9-km grid configuration (Outer grid extent: 60.4S to 17.7N and 118.6W to 17.4W).

  17. Preliminary ice shelf-ocean simulation results from idealized standalone-ocean and coupled model intercomparison projects (MIPs)

    NASA Astrophysics Data System (ADS)

    Asay-Davis, Xylar; Martin, Daniel

    2016-04-01

    The second Ice Shelf-Ocean MIP (ISOMIP+) and the first Marine Ice Sheet-Ocean MIP (MISOMIP1) prescribe a set of idealized experiments for ocean models with ice-shelf cavities and coupled ice sheet-ocean models, respectively. ISOMIP+ and MISOMIP1 were designed together with the third Marine Ice Sheet MIP (MISMIP+) with three main goals, namely that the MIPs should provide: a controlled forum for researchers to compare their model results with those from other models during model development. a path for testing components in the process of developing coupled ice sheet-ocean models. a basic setup from which a large variety of parameter and process studies can usefully be performed. The experimental design for the three MIPs is currently under review in Geoscientific Model Development (Asay-Davis et al. 2015, doi:10.5194/gmdd-8-9859-2015). We present preliminary results from ISOMIP+ and MISOMIP1 experiments using several ocean-only and coupled ice sheet-ocean models. Among ocean models, we show that differences in model behavior are significant enough that similar results can only be achieved by tuning model parameters (e.g. boundary-layer transfer coefficients, drag coefficients, vertical mixing parameterizations) for each models. This tuning is constrained by a desired mean melt rate in quasi-steady state under specified forcing conditions, akin to how models would be tuned based on observations for non-idealized simulations. We also present a number of parameter studies based the MIP experiments. Again, using several models, we show that melt rates respond sub-linearly to both changes in the square root of the drag coefficient and the heat-transfer coefficient, and that melting is relatively insensitive to horizontal-mixing coefficients (perhaps because the resolution is sufficient to permit eddies) but more sensitive to vertical-mixing coefficients. We show that the choice of the equation of state (linear or nonlinear) does not have a significant impact as long as

  18. Simulating Late Ordovician deep ocean O2 with an earth system climate model. Preliminary results.

    NASA Astrophysics Data System (ADS)

    D'Amico, Daniel F.; Montenegro, Alvaro

    2016-04-01

    The geological record provides several lines of evidence that point to the occurrence of widespread and long lasting deep ocean anoxia during the Late Ordovician, between about 460-440 million years ago (ma). While a series of potential causes have been proposed, there is still large uncertainty regarding how the low oxygen levels came about. Here we use the University of Victoria Earth System Climate Model (UVic ESCM) with Late Ordovician paleogeography to verify the impacts of paleogeography, bottom topography, nutrient loading and cycling and atmospheric concentrations of O2 and CO2 on deep ocean oxygen concentration during the period of interest. Preliminary results so far are based on 10 simulations (some still ongoing) covering the following parameter space: CO2 concentrations of 2240 to 3780 ppmv (~8x to 13x pre-industrial), atmospheric O2 ranging from 8% to 12% per volume, oceanic PO4 and NO3 loading from present day to double present day, reductions in wind speed of 50% and 30% (winds are provided as a boundary condition in the UVic ESCM). For most simulations the deep ocean remains well ventilated. While simulations with higher CO2, lower atmospheric O2 and greater nutrient loading generate lower oxygen concentration in the deep ocean, bottom anoxia - here defined as concentrations <10 μmol L-1 - in these cases is restricted to the high-latitue northern hemisphere. Further simulations will address the impact of greater nutrient loads and bottom topography on deep ocean oxygen concentrations.

  19. Adaptation of an unstructured-mesh, finite-element ocean model to the simulation of ocean circulation beneath ice shelves

    NASA Astrophysics Data System (ADS)

    Kimura, Satoshi; Candy, Adam S.; Holland, Paul R.; Piggott, Matthew D.; Jenkins, Adrian

    2013-07-01

    Several different classes of ocean model are capable of representing floating glacial ice shelves. We describe the incorporation of ice shelves into Fluidity-ICOM, a nonhydrostatic finite-element ocean model with the capacity to utilize meshes that are unstructured and adaptive in three dimensions. This geometric flexibility offers several advantages over previous approaches. The model represents melting and freezing on all ice-shelf surfaces including vertical faces, treats the ice shelf topography as continuous rather than stepped, and does not require any smoothing of the ice topography or any of the additional parameterisations of the ocean mixed layer used in isopycnal or z-coordinate models. The model can also represent a water column that decreases to zero thickness at the 'grounding line', where the floating ice shelf is joined to its tributary ice streams. The model is applied to idealised ice-shelf geometries in order to demonstrate these capabilities. In these simple experiments, arbitrarily coarsening the mesh outside the ice-shelf cavity has little effect on the ice-shelf melt rate, while the mesh resolution within the cavity is found to be highly influential. Smoothing the vertical ice front results in faster flow along the smoothed ice front, allowing greater exchange with the ocean than in simulations with a realistic ice front. A vanishing water-column thickness at the grounding line has little effect in the simulations studied. We also investigate the response of ice shelf basal melting to variations in deep water temperature in the presence of salt stratification.

  20. ENSO Simulation in Coupled Ocean-Atmosphere Models: Are the Current Models Better?

    SciTech Connect

    AchutaRao, K; Sperber, K R

    2005-04-29

    Maintaining a multi-model database over a generation or more of model development provides an important framework for assessing model improvement. Using control integrations, we compare the simulation of the El Nino/Southern Oscillation (ENSO), and its extratropical impact, in models developed for the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report with models developed in the late 1990's (the so-called Coupled Model Intercomparison Project-2 [CMIP2] models). The IPCC models tend to be more realistic in representing the frequency with which ENSO occurs, and they are better at locating enhanced temperature variability over the eastern Pacific Ocean. When compared with reanalyses, the IPCC models have larger pattern correlations of tropical surface air temperature than do the CMIP2 models during the boreal winter peak phase of El Nino. However, for sea-level pressure and precipitation rate anomalies, a clear separation in performance between the two vintages of models is not as apparent. The strongest improvement occurs for the modeling groups whose CMIP2 model tended to have the lowest pattern correlations with observations. This has been checked by subsampling the multi-century IPCC simulations in a manner to be consistent with the single 80-year time segment available from CMIP2. Our results suggest that multi-century integrations may be required to statistically assess model improvement of ENSO. The quality of the El Nino precipitation composite is directly related to the fidelity of the boreal winter precipitation climatology, highlighting the importance of reducing systematic model error. Over North America distinct improvement of El Nino forced boreal winter surface air temperature, sea-level pressure, and precipitation rate anomalies in the IPCC models occurs. This improvement, is directly proportional to the skill of the tropical El Nino forced precipitation anomalies.

  1. Present-day Circum-Antarctic Simulations using the POPSICLES Coupled Ice Sheet-Ocean Model

    NASA Astrophysics Data System (ADS)

    Asay-Davis, X.; Martin, D. F.; Price, S. F.; Maltrud, M. E.; Collins, W.

    2014-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1o (~5 km) ocean resolution and with adaptive ice-sheet model resolution as fine as 500 m. We compare time-averaged melt rates below a number of major ice shelves with those reported by Rignot et al. (2013) as well as other recent studies. We also present seasonal variability and decadal trends in submarine melting from several Antarctic regions. Finally, we explore the influence on basal melting and system dynamics resulting from two different choices of climate forcing: a "normal-year" climatology and the CORE v. 2 forcing data (Large and Yeager 2008).POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh (2009) to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3D; Pattyn et al., 2013) and realistic configurations (Favier et al. 2014).A companion presentation, "Response of the Antarctic Ice Sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model" in session C024 covers the ice-sheet response to these melt rates in the coupled simulation

  2. Numerical simulation of Typhoon Muifa (2011) using a Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system

    NASA Astrophysics Data System (ADS)

    Liu, Na; Ling, Tiejun; Wang, Hui; Zhang, Yunfei; Gao, Zhiyi; Wang, Yi

    2015-04-01

    The newly developed Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System is applied to investigate typhoon-ocean interactions in this study. The COAWST modeling system represents the state-of-the-art numerical simulation technique comprising several coupled models to study coastal and environmental processes. The modeling system is applied to simulate Typhoon Muifa (2011), which strengthened from a tropical storm to a super typhoon in the Northwestern Pacific, to explore the heat fluxes exchanged among the processes simulated using the atmosphere model WRF, ocean model ROMS and wave model SWAN. These three models adopted the same horizontal grid. Three numerical experiments with different coupling configurations are performed in order to investigate the impact of typhoon-ocean interaction on the intensity and ocean response to typhoon. The simulated typhoon tracks and intensities agree with observations. Comparisons of the simulated variables with available atmospheric and oceanic observations show the good performance of using the coupled modeling system for simulating the ocean and atmosphere processes during a typhoon event. The fully coupled simulation that includes a ocean model identifies a decreased SST as a result of the typhoon-forced entrainment. Typhoon intensity and wind speed are reduced due to the decrease of the sea surface temperature when using a coupled ocean model. The experiments with ocean coupled to atmosphere also results in decreased sea surface heat flux and air temperature. The heat flux decreases by about 29% compared to the WRF only case. The reduction of the energy induced by SST decreases, resulting in weakening of the typhoon. Coupling of the waves to the atmosphere and ocean model induces a slight increase of SST in the typhoon center area with the ocean-atmosphere interaction increased as a result of wave feedback to atmosphere.

  3. Combined simulation of carbon and water isotopes in a global ocean model

    NASA Astrophysics Data System (ADS)

    Paul, André; Krandick, Annegret; Gebbie, Jake; Marchal, Olivier; Dutkiewicz, Stephanie; Losch, Martin; Kurahashi-Nakamura, Takasumi; Tharammal, Thejna

    2013-04-01

    Carbon and water isotopes are included as passive tracers in the MIT general circulation model (MITgcm). The implementation of the carbon isotopes is based on the existing MITgcm carbon cycle component and involves the fractionation processes during photosynthesis and air-sea gas exchange. Special care is given to the use of a real freshwater flux boundary condition in conjunction with the nonlinear free surface of the ocean model. The isotopic content of precipitation and water vapor is obtained from an atmospheric GCM (the NCAR CAM3) and mapped onto the MITgcm grid system, but the kinetic fractionation during evaporation is treated explicitly in the ocean model. In a number of simulations, we test the sensitivity of the carbon isotope distributions to the formulation of fractionation during photosynthesis and compare the results to modern observations of δ13C and Δ14C from GEOSECS, WOCE and CLIVAR. Similarly, we compare the resulting distribution of oxygen isotopes to modern δ18O data from the NASA GISS Global Seawater Oxygen-18 Database. The overall agreement is good, but there are discrepancies in the carbon isotope composition of the surface water and the oxygen isotope composition of the intermediate and deep waters. The combined simulation of carbon and water isotopes in a global ocean model will provide a framework for studying present and past states of ocean circulation such as postulated from deep-sea sediment records.

  4. Simulating the last glacial-interglacial transition with a coupled atmosphere-ocean-ice sheet model

    NASA Astrophysics Data System (ADS)

    Mikolajewicz, Uwe; Ziemen, Florian

    2015-04-01

    One of the major challenges in climate modeling is the simulation of glacial-interglacial transitions. A few models of intermediate complexity have been successful in simulating the last termination. Complex atmosphere-ocean general circulation models have been shown to be able to yield realistic climate changes with prescribed ice sheets. Here we presents results from a first attempt to simulate a substantial part of the last glacial cycle with an AOGCM coupled interactively with a state-of-the-art ice sheet model. The ECHAM5/MPIOM AOGCM has been interactively coupled to the dynamical ice sheet model PISM. The latter is run for most of the northern hemisphere with a horizontal resolution of 20 km. An earlier version of this model ( Ziemen et al. 2014) has been applied to a steady state simulation of the last glacial maximum (LGM). The model was integrated from the late Glacial into the Holocene using insolation and greenhouse gas concentrations as transient forcing. Land sea mask and ocean topography are fixed at LGM conditions, river routing and surface elevation for the atmospheric model component are calculated interactively depending on the simulated ice sheets. To make these long simulations feasible, the atmosphere is accelerated by a factor of 10 relative to the other model components using a periodically-synchronous coupling technique. A mini-ensemble with different initial conditions has been run. In all simulation the northern hemispheric deglaciation starts between 18 and 17 kyr BP, consistent with the onset of global warming. The model produces Heinrich event like variability as part of its internal variability. These rapid ice discharge events have a strong impact on the North Atlantic meridional overturning circulation (NAMOC). During the peak deglaciation the NAMOC is collapsed (with a few short interruptions) for several thousand years, which is longer than the estimates from reconstructions. This seems to be an artifact due to keeping ocean

  5. Ensemble climate simulations using a fully coupled ocean-troposphere-stratosphere general circulation model.

    PubMed

    Huebener, H; Cubasch, U; Langematz, U; Spangehl, T; Niehörster, F; Fast, I; Kunze, M

    2007-08-15

    Long-term transient simulations are carried out in an initial condition ensemble mode using a global coupled climate model which includes comprehensive ocean and stratosphere components. This model, which is run for the years 1860-2100, allows the investigation of the troposphere-stratosphere interactions and the importance of representing the middle atmosphere in climate-change simulations. The model simulates the present-day climate (1961-2000) realistically in the troposphere, stratosphere and ocean. The enhanced stratospheric resolution leads to the simulation of sudden stratospheric warmings; however, their frequency is underestimated by a factor of 2 with respect to observations.In projections of the future climate using the Intergovernmental Panel on Climate Change special report on emissions scenarios A2, an increased tropospheric wave forcing counteracts the radiative cooling in the middle atmosphere caused by the enhanced greenhouse gas concentration. This leads to a more dynamically active, warmer stratosphere compared with present-day simulations, and to the doubling of the number of stratospheric warmings. The associated changes in the mean zonal wind patterns lead to a southward displacement of the Northern Hemisphere storm track in the climate-change signal. PMID:17569652

  6. Wave heights in the 21st century Arctic Ocean simulated with a regional climate model

    NASA Astrophysics Data System (ADS)

    Khon, V. C.; Mokhov, I. I.; Pogarskiy, F. A.; Babanin, A.; Dethloff, K.; Rinke, A.; Matthes, H.

    2014-04-01

    While wave heights globally have been growing over recent decades, observations of their regional trends vary. Simulations of future wave climate can be achieved by coupling wave and climate models. At present, wave heights and their future trends in the Arctic Ocean remain unknown. We use the third-generation wave forecast model WAVEWATCH-III forced by winds and sea ice concentration produced within the regional model HIRHAM, under the anthropogenic scenario SRES-A1B. We find that significant wave height and its extremes will increase over different inner Arctic areas due to reduction of sea ice cover and regional wind intensification in the 21st century. The opposite tendency, with a slight reduction in wave height appears for the Atlantic sector and the Barents Sea. Our results demonstrate the complex wave response in the Arctic Ocean to a combined effect of wind and sea ice forcings in a climate-change scenario during the 21st century.

  7. Southern Ocean variability derived from GRACE retrievals, model simulations and in-situ measurements

    NASA Astrophysics Data System (ADS)

    Böning, C.; Timmermann, R.; Macrander, A.; Schröter, J.; Boebel, O.

    2009-04-01

    The Gravity Recovery and Climate Experiment (GRACE) provides estimates of the Earth's static and time-variant gravity field. Solutions from various processing centres (GFZ, CSR, GRGS, JPL etc.) enable us to determine mass redistributions on the globe. Given that land signals are generally large compared to anomalies over the ocean, an assessment of the latter requires a particularly careful filtering of the data. We utilized the Finite Element Sea-Ice Ocean Model (FESOM) to develop a filtering algorithm which relies on the spatial coherency of ocean bottom pressure (OBP) anomalies. Taking large-scale circulation patterns into account, the new filter yields an improved representation of OBP (i.e. ocean mass) variability in the filtered GRACE data. In order to investigate the representation of Antarctic Circumpolar Current (ACC) variability in the pattern-filtered GRACE retrievals, an analysis of OBP anomalies in FESOM results and in-situ measurements has been performed. A bottom pressure recorder array in the ACC region south of Africa (36°S-58°S, 1°W-7°E) provides data from 2002-2008. Based on anomalies of OBP gradients between individual instruments, these in-situ measurements give an estimate of the overall transport variability as well as of the movement of ACC fronts and transport redistribution between different sectors of the ACC. The validation of simulated and satellite-derived OBP anomaly gradients against these data yields a measure for the representation of this variability in FESOM and GRACE. Furthermore, model simulations are used to assess the relation between transport variations in individual filaments of the Southern Ocean and total transport variability in this and other sectors of the ACC.

  8. A model to simulate nonhydrostatic internal gravity waves in the ocean

    NASA Astrophysics Data System (ADS)

    Vitousek, S.; Fringer, O. B.; Zhang, Y.

    2015-12-01

    Internal gravity waves in the ocean are primarily generated due to tidal flow over topography that generates internal tides, or internal waves of tidal frequency. As they propagate, internal tides steepen into trains of internal solitary waves that eventually break upon interacting with shallow coastal topography. Modeling internal solitary waves is difficult because they have length scales that are short relative to the internal tide, and so many grid points in three dimensions are needed to accurately resolve their evolution. Because internal solitary waves arise from a balance between nonlinear advection of momentum and nonhydrostatic dispersion, they must be simulated with nonhydrostatic ocean models. Such models are expensive because computation of the nonhydrostatic pressure requires solution of a three-dimensional Poisson equation that can incur an order of magnitude increase in the computational cost. Finally, because internal solitary waves can propagate over long distances with little to no dissipation or mixing of the thermocline upon which they propagate, the numerical model must minimize spurious vertical numerical diffusion of the density field. We will discuss development of a new ocean model designed to accurately simulate internal solitary waves. Horizontally unstructured, finite-volume grids are employed to enable resolution of the multiscale nature of internal solitary waves by refining the grid where they are likely to form. To resolve the nonlinear-nonhydrostatic balance in the waves, the model computes the nonhydrostatic pressure, but with a preconditioner that ensures minimal overhead where the nonhydrotatic pressure is not needed. Finally, to minimize spurious numerical diffusion, we employ an Arbitrary-Lagrangian-Eulerian (ALE), or hybrid, vertical coordinate system in which the vertical direction is discretized with boundary-following (sigma or s), Cartesian (z), or density-following (isopycnal) coordinates. Because isopycnal coordinates

  9. Coupled atmosphere-ocean model simulations of El Nino/Southern Oscillation with and without an active Indian Ocean

    SciTech Connect

    Nagai, T.; Kitamura, Y.; Endoh, M.; Tokioka, T.

    1995-01-01

    An atmospheric general circulation model (GCM) was coupled with an ocean GCM covering the Pacific. This coupled model (PAC) was integrated over a 30-year period. The PAC model stimulates well the mean seasonally varying atmospheric and ocean fields and reproduces interannual variations corresponding to ENSO (El Nino/Southern Oscillation). The same atmospheric GCM was coupled with an ocean GCM covering the Indian Ocean and the tropical Pacific. This coupled model (IPC) was integrated over a 35-year period. The model climate in IPC is fairly reasonable, and its Pacific part is very similar to the Pacific climate of the PAC model. ENSO is the major interannual variability in the IPC model. The dynamics of ENSO in IPC are essentially the same as that in PAC. In the Pacific, the subsurface ocean heat content anomalies are formed by wind anomalies and show westward propagation centered off the equator. After they reach the western Pacific, they show eastward propagation along the equator. They produce changes in the thermocline structure in the eastern equatorial Pacific resulting in anomalies in SSTs. The SST anomalies provide wind anomalies, the sign of which is opposite to that of the wind anomalies in the first stage, so that this chain will continue. ENSO in the PAC and IPC models can be regarded as the {open_quotes}delayed oscillator{close_quotes} operating in the Pacific. Although the major interannual variability in the Indian Ocean is linked to ENSO in the Pacific, the Indian Ocean does not play any active role in the ENSO cycle in the IPC model. Interannual variability of monsoon activity in the IPC model is more reasonable than that in the PAC model. However, any definite mechanism for the relationship between monsoon activity and ENSO does not emerge in the present study. 31 refs., 14 figs.

  10. An ocean-atmosphere climate simulation with an embedded cloud resolving model

    NASA Astrophysics Data System (ADS)

    Stan, Cristiana; Khairoutdinov, Marat; DeMott, Charlotte A.; Krishnamurthy, V.; Straus, David M.; Randall, David A.; Kinter, James L.; Shukla, J.

    2010-01-01

    Mean climate and intraseasonal to interannual variability of two versions of the Community Climate System Model (CCSM) coupled atmosphere-ocean general circulation model (CGCM) are analyzed. The first version is the standard CCSM, in which cloud effects on the large-scale circulation are represented via parameterizations. The second version includes “super-parameterization” (SP) of convective processes by replacing parameterized cloud processes with a two-dimensional (2D) cloud-process resolving model (CRM) at each CGCM grid column. The SP-CCSM improves several shortcomings of the CCSM simulation, including mean precipitation patterns, equatorial SST cold tongue structure and associated double intertropical convergence zone (ITCZ), the Asian monsoon, periodicity of the El Niño-Southern Oscillation, and the intraseasonal Madden-Julian Oscillation. These improvements were obtained without the retuning of the coupled model, which is surprising in view of previous experience with other coupled models.

  11. Development of a Coupled Ocean-Hydrologic Model to Simulate Pollutant Transport in Singapore Coastal Waters

    NASA Astrophysics Data System (ADS)

    Chua, V. P.

    2015-12-01

    Intensive agricultural, economic and industrial activities in Singapore and Malaysia have made our coastal areas under high risk of water pollution. A coupled ocean-hydrologic model is employed to perform three-dimensional simulations of flow and pollutant transport in Singapore coastal waters. The hydrologic SWAT model is coupled with the coastal ocean SUNTANS model by outputting streamflow and pollutant concentrations from the SWAT model and using them as inputs for the SUNTANS model at common boundary points. The coupled model is calibrated with observed sea surface elevations and velocities, and high correlation coefficients that exceed 0.97 and 0.91 are found for sea surface elevations and velocities, respectively. The pollutants are modeled as Gaussian passive tracers, and are released at five upstream locations in Singapore coastal waters. During the Northeast monsoon, pollutants released in Source 1 (Johor River), Source 2 (Tiram River), Source 3 (Layang River) and Source 4 (Layau River) enter the Singapore Strait after 4 days of release and reach Sentosa Island within 9 days. Meanwhile, pollutants released in Source 5 (Kallang River) reach Sentosa Island after 4 days. During the Southwest monsoon, the dispersion time is roughly doubled, with pollutants from Sources 1 - 4 entering the Singapore Strait only after 12 days of release due to weak currents.

  12. A mass-conserving advection scheme for offline simulation of scalar transport in coastal ocean models

    NASA Astrophysics Data System (ADS)

    Gillibrand, P. A.; Herzfeld, M.

    2016-05-01

    We present a flux-form semi-Lagrangian (FFSL) advection scheme designed for offline scalar transport simulation with coastal ocean models using curvilinear horizontal coordinates. The scheme conserves mass, overcoming problems of mass conservation typically experienced with offline transport models, and permits long time steps (relative to the Courant number) to be used by the offline model. These attributes make the method attractive for offline simulation of tracers in biogeochemical or sediment transport models using archived flow fields from hydrodynamic models. We describe the FFSL scheme, and test it on two idealised domains and one real domain, the Great Barrier Reef in Australia. For comparison, we also include simulations using a traditional semi-Lagrangian advection scheme for the offline simulations. We compare tracer distributions predicted by the offline FFSL transport scheme with those predicted by the original hydrodynamic model, assess the conservation of mass in all cases and contrast the computational efficiency of the schemes. We find that the FFSL scheme produced very good agreement with the distributions of tracer predicted by the hydrodynamic model, and conserved mass with an error of a fraction of one percent. In terms of computational speed, the FFSL scheme was comparable with the semi-Lagrangian method and an order of magnitude faster than the full hydrodynamic model, even when the latter ran in parallel on multiple cores. The FFSL scheme presented here therefore offers a viable mass-conserving and computationally-efficient alternative to traditional semi-Lagrangian schemes for offline scalar transport simulation in coastal models.

  13. Impacts of atmospheric and oceanic resolution on the tropical Pacific climatology simulated by GFDL's new climate models

    NASA Astrophysics Data System (ADS)

    Wittenberg, A. T.; Vecchi, G. A.; Delworth, T. L.; Rosati, A.; Anderson, W.; Zeng, F. J.

    2014-12-01

    We examine impacts of atmospheric and oceanic grid refinement on simulations of the tropical Pacific climatology, using a series of high-resolution global coupled GCMs recently developed at GFDL. Starting from the CM2.1 model developed for CMIP3, the new models progressively refine the horizontal grid spacing in the atmosphere by a factor of five (CM2.5-FLOR), and additionally in the ocean by factors of four (CM2.5) and ten (CM2.6). The atmospheric refinement is found to substantially improve the coupled simulation's tropical Pacific climatology of SST, rainfall, surface pressure, winds, coastal upwelling, and upper-ocean temperature and salinity -- and also reduces the net air-sea heat flux into the ocean near the equator, indicating reduced ocean-dynamical cooling due to weaker trade winds. Oceanic refinement, in contrast, results in much less improvement to the simulated surface climatology -- and in some respects actually degrades the simulation, for example by over-intensifying the thermal stratification of the equatorial upper ocean. This suggests that in the more strongly-eddying regimes permitted by higher resolution, some of the ocean component's physical parameterizations may need retuning or reformulation. The causes of these various sensitivities are discussed, along with avenues toward future improvements.

  14. Simulation of the world ocean climate with a massively parallel numerical model

    NASA Astrophysics Data System (ADS)

    Ushakov, K. V.; Ibrayev, R. A.; Kalmykov, V. V.

    2015-07-01

    The INM-IO numerical World Ocean model is verified through the calculation of the model ocean climate. The numerical experiment was conducted for a period of 500 years following the CORE-I protocol. We analyze some basic elements of the large-scale ocean circulation and local and integral characteristics of the model solution. The model limitations and ways they are overcome are described. The results generally fit the level of leading models. This experiment is a necessary step preceding the transition to high-resolution diagnostic and prognostic calculations of the state of the World Ocean and its individual basins.

  15. Simulating the Response to Astronomical Forcing with a Coupled Atmosphere-Ocean Model

    NASA Astrophysics Data System (ADS)

    Erb, M. P.; Broccoli, A. J.; Raney, B.

    2015-12-01

    Substantial variations in climate during the Quaternary Period have been reconstructed from a wide array of paleoclimate proxies, with much of the variance occurring on the same time scales as astronomical forcing. To understand the mechanisms that may be responsible for these variations, we employ a set of single-forcing simulations with a coupled atmosphere-ocean general circulation model and systematically examine the climatic responses to changes in Earth's orbital parameters (i.e., perihelion date and axial tilt). We survey some of the highlights from our analysis of these simulations, including the response of tropical circulation to astronomical forcing and contributions of radiative feedbacks to the global and regional thermodynamic response.

  16. Impact of air-sea coupling on the simulation of tropical cyclones in the North Indian Ocean using a simple 3-D ocean model coupled to ARW

    NASA Astrophysics Data System (ADS)

    Srinivas, C. V.; Mohan, Greeshma M.; Naidu, C. V.; Baskaran, R.; Venkatraman, B.

    2016-08-01

    In this work, the impact of air-sea coupling on tropical cyclone (TC) predictions is studied using a three-dimensional Price-Weller-Pinkel (3DPWP) ocean model coupled to the Advanced Research Weather Research and Forecasting in six tropical storms in the North Indian Ocean, representing different intensities, seasonality, and varied oceanic conditions. A set of numerical experiments are conducted for each cyclone using sea surface temperature (SST) boundary conditions derived from Global Forecast System (GFS) SST, NOAA/National Centers for Environmental Prediction SST, and ocean coupling (3DPWP). Significant differences and improvements are found in the predicted intensity and track in the simulations, in which the cyclones' impact on SST is included. It has been found that while the uncoupled model using GFS SST considerably overestimated the intensity as well as produced large track errors, the ocean coupling substantially improved the track and intensity predictions. The improvements with 3DPWP are because of simulating the ocean-atmosphere feedback in terms of deepening of ocean mixed layer, reduction in enthalpy fluxes, and storm-induced SST cooling as seen in observations. The coupled model could simulate the cold wake in SST, asymmetries in the surface winds, enthalpy fluxes, size, and structure of the storm in better agreement with observations than the uncoupled model. The coupled model reduced the track errors by roughly 0.3-39% and intensity errors by 29-47% at 24-96 h predictions by controlling the northward deviation of storms tracks by SST cooling and associated changes in the dynamics. The vorticity changes associated with horizontal advection and stretching terms affect the tracks of the storms in the three simulations.

  17. Can Regional Ocean-Atmosphere Coupled Model Improve the Simulation of the Interannual Variability of Western North Pacific Summer Monsoon?

    NASA Astrophysics Data System (ADS)

    Zou, L.; Zhou, T.

    2012-12-01

    With the motivation to improve the simulation of interannual variability of western North Pacific summer monsoon (WNPSM), a flexible regional ocean-atmosphere-land system coupled model (FROALS) was developed through the OASIS3.0 coupler. The regionally coupled model is composed of a regional climate model RegCM3 as its atmospheric component, a global climate ocean model (LICOM) as its oceanic component. Impacts of local air-sea interaction on the simulation of interannual variability of WNPSM are investigated by performing regionally ocean-atmosphere coupled and uncoupled simulations, with focus on the El Niño decaying summer. Compared to uncoupled simulation, the regionally coupled simulation exhibits improvements in both the climatology and interannual variability of rainfall over WNP. In El Niño decaying summer, the WNP saw an anomalous anticyclone, less rainfall and enhanced subsidence, which led to an increase in downward shortwave radiation flux, and thereby a warmer SST anomalies. Thus the ocean appears as a slave to atmospheric forcing. But in the uncoupled simulation, the atmosphere is a slave to oceanic SST forcing, the warmer SST anomalies located over east of the Philippines unrealistically produce excessive rainfall. In the regionally coupled run, the un-realistic positive rainfall anomalies and the associated atmospheric circulations over east of the Philippines are significantly improved, highlighting the importance of air-sea coupling in the simulation of interannual variability of WNPSM. One limitation of the model is that the anomalous anticyclone over WNP is weaker than the observation in both the regionally coupled and uncoupled simulations. This is resulted from the weaker simulated climatological summer rainfall intensity over the monsoon trough.

  18. Simulating Heinrich events in a coupled atmosphere-ocean-ice sheet model

    NASA Astrophysics Data System (ADS)

    Mikolajewicz, Uwe; Ziemen, Florian

    2016-04-01

    Heinrich events are among the most prominent events of long-term climate variability recorded in proxies across the northern hemisphere. They are the archetype of ice sheet - climate interactions on millennial time scales. Nevertheless, the exact mechanisms that cause Heinrich events are still under discussion, and their climatic consequences are far from being fully understood. We contribute to answering the open questions by studying Heinrich events in a coupled ice sheet model (ISM) atmosphere-ocean-vegetation general circulation model (AOVGCM) framework, where this variability occurs as part of the model generated internal variability without the need to prescribe external perturbations, as was the standard approach in almost all model studies so far. The setup consists of a northern hemisphere setup of the modified Parallel Ice Sheet Model (mPISM) coupled to the global coarse resolution AOVGCM ECHAM5/MPIOM/LPJ. The simulations used for this analysis were an ensemble covering substantial parts of the late Glacial forced with transient insolation and prescribed atmospheric greenhouse gas concentrations. The modeled Heinrich events show a marked influence of the ice discharge on the Atlantic circulation and heat transport, but none of the Heinrich events during the Glacial did show a complete collapse of the North Atlantic meridional overturning circulation. The simulated main consequences of the Heinrich events are a freshening and cooling over the North Atlantic and a drying over northern Europe.

  19. A Realistically Perturbed Atmosphere and Ocean De-Aliasing Model for Future Gravity Mission Simulation Studies

    NASA Astrophysics Data System (ADS)

    Dobslaw, Henryk; Forootan, Ehsan; Bergmann-Wolf, Inga; Neumayer, Karl-Hans; Mayer-Gürr, Torsten; Kusche, Jürgen; Flechtner, Frank

    2015-04-01

    Recently completed performance studies of future gravity mission concepts arrived at sometimes contradicting conclusions about the importance of non-tidal aliasing errors that remain in the finally retrieved gravity field time-series. In those studies, typically a fraction of the differences between two different models of atmosphere and ocean mass variability determined the magnitude of the aliasing errors. Since differences among arbitrary pairs of the numerical models available might lead to widely different aliasing errors and thus conclusions regarding limiting error contributors of a candidate mission, we present here for the first time a version of a realistically perturbed de-aliasing model that is consistent with the updated ESA Earth System Model for gravity mission simulation studies (Dobslaw et al., 2015). The error model is available over the whole 12-year period of the ESA ESM and consists of two parts: (i) a component containing signals from physical processes that are intentionally omitted from de-aliasing models, as for a example, variations in global eustatic sea-level; and (ii) a series of true errors that consist of in total five different components with realistically re-scaled variability at both small and large spatial scales for different frequency bands ranging from sub-daily to sub-monthly periods. Based on a multi-model ensemble of atmosphere and ocean mass variability available to us for the year 2006, we will demonstrate that our re-scaled true errors have plausible magnitudes and correlation characteristics in all frequency bands considered. The realism of the selected scaling coefficients for periods between 1 and 30 days is tested further by means of a variance component estimation based on the constrained daily GRACE solution series ITSG-GRACE2014. Initial full-scale simulation experiments are used to re-assess the relative importance of non-tidal de-aliasing errors for the GRACE-FO mission, which might be subsequently expanded to

  20. Impact of variable seawater conductivity on motional induction simulated with an ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Irrgang, C.; Saynisch, J.; Thomas, M.

    2016-01-01

    Carrying high concentrations of dissolved salt, ocean water is a good electrical conductor. As seawater flows through the Earth's ambient geomagnetic field, electric fields are generated, which in turn induce secondary magnetic fields. In current models for ocean-induced magnetic fields, a realistic consideration of seawater conductivity is often neglected and the effect on the variability of the ocean-induced magnetic field unknown. To model magnetic fields that are induced by non-tidal global ocean currents, an electromagnetic induction model is implemented into the Ocean Model for Circulation and Tides (OMCT). This provides the opportunity to not only model ocean-induced magnetic signals but also to assess the impact of oceanographic phenomena on the induction process. In this paper, the sensitivity of the induction process due to spatial and temporal variations in seawater conductivity is investigated. It is shown that assuming an ocean-wide uniform conductivity is insufficient to accurately capture the temporal variability of the magnetic signal. Using instead a realistic global seawater conductivity distribution increases the temporal variability of the magnetic field up to 45 %. Especially vertical gradients in seawater conductivity prove to be a key factor for the variability of the ocean-induced magnetic field. However, temporal variations of seawater conductivity only marginally affect the magnetic signal.

  1. Assessment of atmosphere-ocean general circulation model simulations of winter northern hemisphere atmospheric blocking

    NASA Astrophysics Data System (ADS)

    Vial, Jessica; Osborn, Tim J.

    2012-07-01

    An assessment of six coupled Atmosphere-Ocean General Circulation Models (AOGCMs) is undertaken in order to evaluate their ability in simulating winter atmospheric blocking highs in the northern hemisphere. The poor representation of atmospheric blocking in climate models is a long-standing problem (e.g. D'Andrea et al. in Clim Dyn 4:385-407, 1998), and despite considerable effort in model development, there is only a moderate improvement in blocking simulation. A modified version of the Tibaldi and Molteni (in Tellus A 42:343-365, 1990) blocking index is applied to daily averaged 500 hPa geopotential fields, from the ERA-40 reanalysis and as simulated by the climate models, during the winter periods from 1957 to 1999. The two preferred regions of blocking development, in the Euro-Atlantic and North Pacific, are relatively well captured by most of the models. However, the prominent error in blocking simulations consists of an underestimation of the total frequency of blocking episodes over both regions. A more detailed analysis revealed that this error was due to an insufficient number of medium spells and long-lasting episodes, and a shift in blocking lifetime distributions towards shorter blocks in the Euro-Atlantic sector. In the Pacific, results are more diverse; the models are equally likely to overestimate or underestimate the frequency at different spell lengths. Blocking spatial signatures are relatively well simulated in the Euro-Atlantic sector, while errors in the intensity and geographical location of the blocks emerge in the Pacific. The impact of models' systematic errors on blocking simulation has also been analysed. The time-mean atmospheric circulation biases affect the frequency of blocking episodes, and the maximum event duration in the Euro-Atlantic region, while they sometimes cause geographical mislocations in the Pacific sector. The analysis of the systematic error in time-variability has revealed a negative relationship between the high

  2. Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

    NASA Technical Reports Server (NTRS)

    Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

    1999-01-01

    A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

  3. Ocean Drilling Simulation Activity.

    ERIC Educational Resources Information Center

    Telese, James A.; Jordan, Kathy

    The Ocean Drilling Project brings together scientists and governments from 20 countries to explore the earth's structure and history as it is revealed beneath the oceans' basins. Scientific expeditions examine rock and sediment cores obtained from the ocean floor to learn about the earth's basic processes. The series of activities in this…

  4. Efficient Flowline Simulations of Ice Shelf-Ocean Interactions: Sensitivity Studies with a Fully Coupled Model

    NASA Technical Reports Server (NTRS)

    Walker, Ryan Thomas; Holland, David; Parizek, Byron R.; Alley, Richard B.; Nowicki, Sophie M. J.; Jenkins, Adrian

    2013-01-01

    Thermodynamic flowline and plume models for the ice shelf-ocean system simplify the ice and ocean dynamics sufficiently to allow extensive exploration of parameters affecting ice-sheet stability while including key physical processes. Comparison between geophysically and laboratory-based treatments of ice-ocean interface thermodynamics shows reasonable agreement between calculated melt rates, except where steep basal slopes and relatively high ocean temperatures are present. Results are especially sensitive to the poorly known drag coefficient, highlighting the need for additional field experiments to constrain its value. These experiments also suggest that if the ice-ocean interface near the grounding line is steeper than some threshold, further steepening of the slope may drive higher entrainment that limits buoyancy, slowing the plume and reducing melting; if confirmed, this will provide a stabilizing feedback on ice sheets under some circumstances.

  5. Distribution of oceanic 137Cs from the Fukushima Dai-ichi Nuclear Power Plant simulated numerically by a regional ocean model.

    PubMed

    Tsumune, Daisuke; Tsubono, Takaki; Aoyama, Michio; Hirose, Katsumi

    2012-09-01

    Radioactive materials were released to the environment from the Fukushima Dai-ichi Nuclear Power Plant as a result of the reactor accident after the Tohoku earthquake and tsunami of 11 March 2011. The measured (137)Cs concentration in a seawater sample near the Fukushima Dai-ichi Nuclear Power Plant site reached 68 kBq L(-1) (6.8 × 10(4)Bq L(-1)) on 6 April. The two major likely pathways from the accident site to the ocean existed: direct release of high radioactive liquid wastes to the ocean and the deposition of airborne radioactivity to the ocean surface. By analysis of the (131)I/(137)Cs activity ratio, we determined that direct release from the site contributed more to the measured (137)Cs concentration than atmospheric deposition did. We then used a regional ocean model to simulate the (137)Cs concentrations resulting from the direct release to the ocean off Fukushima and found that from March 26 to the end of May the total amount of (137)Cs directly released was 3.5 ± 0.7 PBq ((3.5 ± 0.7) × 10(15)Bq). The simulated temporal change in (137)Cs concentrations near the Fukushima Daini Nuclear Power Plant site agreed well with observations. Our simulation results showed that (1) the released (137)Cs advected southward along the coast during the simulation period; (2) the eastward-flowing Kuroshio and its extension transported (137)C during May 2011; and (3) (137)Cs concentrations decreased to less than 10 BqL(-1) by the end of May 2011 in the whole simulation domain as a result of oceanic advection and diffusion. We compared the total amount and concentration of (137)Cs released from the Fukushima Dai-ichi reactors to the ocean with the (137)Cs released to the ocean by global fallout. Even though the measured (137)Cs concentration from the Fukushima accident was the highest recorded, the total released amount of (137)Cs was not very large. Therefore, the effect of (137)Cs released from the Fukushima Dai-ichi reactors on concentration in the whole North

  6. Behaviour of oceanic 137Cs following the Fukushima Daiichi Nuclear Power Plant accident for four years simulated numerically by a regional ocean model

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Koven, C. D.; Riley, W. J.; Zhu, B.; Hicks Pries, C.; Phillips, C. L.

    2014-12-01

    A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) following the earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways, direct release from the accident site and atmospheric deposition.We reconstructed spatiotemporal variability of 137Cs activity in the regional ocean for four years by numerical model, such as a regional scale and the North Pacific scale oceanic dispersion models, an atmospheric transport model, a sediment transport model, a dynamic biological compartment model for marine biota and river runoff model. Direct release rate of 137Cs were estimated for four years after the accident by comparing simulated results and observed activities very close to the site. The estimated total amounts of directly release was 3.6±0.7 PBq. Directly release rate of 137Cs decreased exponentially with time by the end of December 2012 and then, was almost constant. Decrease rate were quite small after 2013. The daily release rate of 137Cs was estimated to be the order of magnitude of 1010 Bq/day by the end of March 2015. The activity of directly released 137Cs was detectable only in the coastal zone after December 2012. Simulated 137Cs activities attributable to direct release were in good agreement with observed activities, a result that implies the estimated direct release rate was reasonable. There is no observed data of 137Cs activity in the ocean from 11 to 21 March 2011. Observed data of marine biota should reflect the history of 137Cs activity in this early period. We reconstructed the history of 137Cs activity in this early period by considering atmospheric deposition, river input, rain water runoff from the 1F NPP site. The comparisons between simulated 137Cs activity of marine biota by a dynamic biological compartment and observed data also suggest that simulated 137Cs activity attributable to atmospheric deposition was underestimated in this early period. The

  7. Behaviour of oceanic 137Cs following the Fukushima Daiichi Nuclear Power Plant accident for four years simulated numerically by a regional ocean model

    NASA Astrophysics Data System (ADS)

    Tsumune, D.; Tsubono, T.; Aoyama, M.; Misumi, K.; Tateda, Y.

    2015-12-01

    A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) following the earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways, direct release from the accident site and atmospheric deposition.We reconstructed spatiotemporal variability of 137Cs activity in the regional ocean for four years by numerical model, such as a regional scale and the North Pacific scale oceanic dispersion models, an atmospheric transport model, a sediment transport model, a dynamic biological compartment model for marine biota and river runoff model. Direct release rate of 137Cs were estimated for four years after the accident by comparing simulated results and observed activities very close to the site. The estimated total amounts of directly release was 3.6±0.7 PBq. Directly release rate of 137Cs decreased exponentially with time by the end of December 2012 and then, was almost constant. Decrease rate were quite small after 2013. The daily release rate of 137Cs was estimated to be the order of magnitude of 1010 Bq/day by the end of March 2015. The activity of directly released 137Cs was detectable only in the coastal zone after December 2012. Simulated 137Cs activities attributable to direct release were in good agreement with observed activities, a result that implies the estimated direct release rate was reasonable. There is no observed data of 137Cs activity in the ocean from 11 to 21 March 2011. Observed data of marine biota should reflect the history of 137Cs activity in this early period. We reconstructed the history of 137Cs activity in this early period by considering atmospheric deposition, river input, rain water runoff from the 1F NPP site. The comparisons between simulated 137Cs activity of marine biota by a dynamic biological compartment and observed data also suggest that simulated 137Cs activity attributable to atmospheric deposition was underestimated in this early period. The

  8. One-Dimensional Coupled Ecosystem-Carbon Flux Model for the Simulation of Biogeochemical Parameters at Ocean Weather Station P

    NASA Technical Reports Server (NTRS)

    Signorini, S.; McClain, C.; Christian, J.; Wong, C. S.

    2000-01-01

    In this Technical Publication, we describe the model functionality and analyze its application to the seasonal and interannual variations of phytoplankton, nutrients, pCO2 and CO2 concentrations in the eastern subarctic Pacific at Ocean Weather Station P (OWSP, 50 deg. N 145 deg. W). We use a verified one-dimensional ecosystem model, coupled with newly incorporated carbon flux and carbon chemistry components, to simulate 22 years (1958-1980) of pCO2 and CO2 variability at Ocean Weather Station P (OWS P). This relatively long period of simulation verifies and extends the findings of previous studies using an explicit approach for the biological component and realistic coupling with the carbon flux dynamics. The slow currents and the horizontally homogeneous ocean in the subarctic Pacific make OWS P one of the best available candidates for modeling the chemistry of the upper ocean in one dimension. The chlorophyll and ocean currents composite for 1998 illustrates this premise. The chlorophyll concentration map was derived from SeaWiFS data and the currents are from an OGCM simulation (from R. Murtugudde).

  9. Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling and Fe limitation in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Mongin, Mathieu; Nelson, David M.; Pondaven, Philippe; Tréguer, Paul

    2006-03-01

    We previously reported the application of an upper-ocean biogeochemical model in which the elemental composition of the phytoplankton is flexible and responds to changes in light and nutrient availability [Mongin, M., Nelson, D., Pondaven, P., Brzezinski, M., Tréguer, P., 2003. Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling in the western Sargasso Sea. Deep-Sea Research I 50, 1445-1480]. That model, applied in the western Sargasso Sea, considered the cycles of C, N and Si in the upper 400 m and limitation of phytoplankton growth by N, Si and light. We now report a new version of this model that includes Fe cycling and Fe limitation and its application in the Southern Ocean. The model includes two phytoplankton groups, diatoms and non-siliceous forms. Uptake of NO 3- by phytoplankton is light dependent, but NH 4+, Si(OH) 4 and Fe uptake are not and can therefore continue through the night. The model tracks the resulting C/N and Fe/C ratios of both groups and Si/N ratio of diatoms, and permits uptake of C, N, Fe and Si to proceed independently when those ratios are close to those of nutrient-replete phytoplankton. When they indicate a deficiency cellular C, N, Fe or Si, uptake of the non-limiting elements is controlled by the content of the limiting element in accordance with the cell-quota formulation of [Droop, M., 1974. The nutrient status of algal cell in continuous culture. Journal of the Marine Biological Association of the United Kingdom 54, 825-855]. The model thus identifies the growth-limiting element and quantifies the degree of limitation from the elemental composition of the phytoplankton. We applied this model at the French KERFIX site in the Indian Ocean sector of the Southern Ocean, using meteorological forcing for that site from 1991 to 1995. As in the Sargasso Sea application, the flexible-composition structure provides simulations that are consistent with field data with only minimal

  10. Simulation of the spatiotemporal variability of the World Ocean sea surface hight by the INM climate models

    NASA Astrophysics Data System (ADS)

    Iakovlev, N. G.; Volodin, E. M.; Gritsun, A. S.

    2016-07-01

    The results of simulations of the World Ocean sea surface hight (SSH) in by various versions of the Climate Model of the Institute of Numerical Mathematics, Russian Academy of Sciences, are compared with the CNES-CLS09 fields of the mean dynamic topography (deviation of the ocean level from the geoid). Three models with different ocean blocks are considered which slightly differ in numerical schemes and have various horizontal spatial resolution, i.e., the INMCM4 model, which participated in the Climate Model Intercomparison Project (CMIP Phase 5, resolution of 1° × 1/2°); the INMCM5 model, which participates in the next project, CMIP6 (resolution of 1/2° × 1/4°); and the advanced INMCM-ER eddy-resolving model (resolution of 1/6° × 1/8°). It is shown that an increase in the spatial resolution improves the reproduction of ocean currents (with Agulhas and Kuroshio currents as examples) and their variability. A probable cause of relatively high errors in the reproduction of the SSH of Southern and Indian oceans is discussed.

  11. A VIIRS ocean data simulator

    NASA Astrophysics Data System (ADS)

    Robinson, Wayne D.; Patt, Frederick S.; Franz, Bryan A.; Turpie, Kevin R.; McClain, Charles R.

    2009-08-01

    One of the roles of the VIIRS Ocean Science Team (VOST) is to assess the performance of the instrument and scientific processing software that generates ocean color parameters such as normalized water-leaving radiances and chlorophyll. A VIIRS data simulator is being developed to help aid in this work. The simulator will create a sufficient set of simulated Sensor Data Records (SDR) so that the ocean component of the VIIRS processing system can be tested. It will also have the ability to study the impact of instrument artifacts on the derived parameter quality. The simulator will use existing resources available to generate the geolocation information and to transform calibrated radiances to geophysical parameters and visa-versa. In addition, the simulator will be able to introduce land features, cloud fields, and expected VIIRS instrument artifacts. The design of the simulator and its progress will be presented.

  12. El Nino-southern oscillation simulated in an MRI atmosphere-ocean coupled general circulation model

    SciTech Connect

    Nagai, T.; Tokioka, T.; Endoh, M.; Kitamura, Y. )

    1992-11-01

    A coupled atmosphere-ocean general circulation model (GCM) was time integrated for 30 years to study interannual variability in the tropics. The atmospheric component is a global GCM with 5 levels in the vertical and 4[degrees]latitude X 5[degrees] longitude grids in the horizontal including standard physical processes (e.g., interactive clouds). The oceanic component is a GCM for the Pacific with 19 levels in the vertical and 1[degrees]x 2.5[degrees] grids in the horizontal including seasonal varying solar radiation as forcing. The model succeeded in reproducing interannual variations that resemble the El Nino-Southern Oscillation (ENSO) with realistic seasonal variations in the atmospheric and oceanic fields. The model ENSO cycle has a time scale of approximately 5 years and the model El Nino (warm) events are locked roughly in phase to the seasonal cycle. The cold events, however, are less evident in comparison with the El Nino events. The time scale of the model ENSO cycle is determined by propagation time of signals from the central-eastern Pacific to the western Pacific and back to the eastern Pacific. Seasonal timing is also important in the ENSO time scale: wind anomalies in the central-eastern Pacific occur in summer and the atmosphere ocean coupling in the western Pacific operates efficiently in the first half of the year.

  13. Regional model simulation of summer rainfall over the Philippines: Effect of choice of driving fields and ocean flux schemes

    NASA Astrophysics Data System (ADS)

    Francisco, R. V.; Argete, J.; Giorgi, F.; Pal, J.; Bi, X.; Gutowski, W. J.

    2006-09-01

    The latest version of the Abdus Salam International Centre for Theoretical Physics (ICTP) regional model RegCM is used to investigate summer monsoon precipitation over the Philippine archipelago and surrounding ocean waters, a region where regional climate models have not been applied before. The sensitivity of simulated precipitation to driving lateral boundary conditions (NCEP and ERA40 reanalyses) and ocean surface flux scheme (BATS and Zeng) is assessed for 5 monsoon seasons. The ability of the RegCM to simulate the spatial patterns and magnitude of monsoon precipitation is demonstrated, both in response to the prominent large scale circulations over the region and to the local forcing by the physiographical features of the Philippine islands. This provides encouraging indications concerning the development of a regional climate modeling system for the Philippine region. On the other hand, the model shows a substantial sensitivity to the analysis fields used for lateral boundary conditions as well as the ocean surface flux schemes. The use of ERA40 lateral boundary fields consistently yields greater precipitation amounts compared to the use of NCEP fields. Similarly, the BATS scheme consistently produces more precipitation compared to the Zeng scheme. As a result, different combinations of lateral boundary fields and surface ocean flux schemes provide a good simulation of precipitation amounts and spatial structure over the region. The response of simulated precipitation to using different forcing analysis fields is of the same order of magnitude as the response to using different surface flux parameterizations in the model. As a result it is difficult to unambiguously establish which of the model configurations is best performing.

  14. Simulation of glacial ocean biogeochemical tracer and isotope distributions based on the PMIP3 suite of climate models

    NASA Astrophysics Data System (ADS)

    Khatiwala, Samar; Muglia, Juan; Kvale, Karin; Schmittner, Andreas

    2016-04-01

    In the present climate system, buoyancy forced convection at high-latitudes together with internal mixing results in a vigorous overturning circulation whose major component is North Atlantic Deep Water. One of the key questions of climate science is whether this "mode" of circulation persisted during glacial periods, and in particular at the Last Glacial Maximum (LGM; 21000 years before present). Resolving this question is both important for advancing our understanding of the climate system, as well as a critical test of numerical models' ability to reliably simulate different climates. The observational evidence, based on interpreting geochemical tracers archived in sediments, is conflicting, as are simulations carried out with state-of-the-art climate models (e.g., as part of the PMIP3 suite), which, due to the computational cost involved, do not by and large include biogeochemical and isotope tracers that can be directly compared with proxy data. Here, we apply geochemical observations to evaluate the ability of several realisations of an ocean model driven by atmospheric forcing from the PMIP3 suite of climate models to simulate global ocean circulation during the LGM. This results in a wide range of circulation states that are then used to simulate biogeochemical tracer and isotope (13C, 14C and Pa/Th) distributions using an efficient, "offline" computational scheme known as the transport matrix method (TMM). One of the key advantages of this approach is the use of a uniform set of biogeochemical and isotope parameterizations across all the different circulations based on the PMIP3 models. We compare these simulated distributions to both modern observations and data from LGM ocean sediments to identify similarities and discrepancies between model and data. We find, for example, that when the ocean model is forced with wind stress from the PMIP3 models the radiocarbon age of the deep ocean is systematically younger compared with reconstructions. Changes in

  15. Eddy permitting simulation of the global ocean model COCO4.3 driven by the CORE inter- annual forcing

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Hasumi, H.; Komuro, Y.; Sakamoto, T. T.

    2008-12-01

    We are developing ocean component of the CCSR/NIES/FRCGC climate model to conduct high-resolution global warming simulations under IPCC scenarios. This presentation focuses on the performance and the behavior and role of eddies in the global ocean. The Ocean model is CCSR Ocean Component Model (COCO) version 4.3, which is a z-coordinate, free-surface primitive equation ocean model with multi-category sea ice model. The geographical North Pole is moved to 40W, 77N on Greenland and the geographical South Pole is moved to 40E, 77S. The computational domain covers global ocean, with zonal grid spacing of 0.28125 degree and meridional grid spacing of 0.1875 degree. There are 50 vertical levels excluding the bottom boundary layer, and 7 of which are within the sigma-coordinate (~42m). The model employs the momentum advection algorithm of Ishizaki and Motoi (1991), which is a pseudo-enstrophy preserving scheme with a consideration for up-/down-sloping advection. The model's tracer advection is based on the second-order moment (SOM) advection scheme of Prather, M. J. (1986). The vertical mixing of momentum and tracers is represented by a harmonic form. The coefficients are calculated by the parameterization of Noh and Kim (1999), but the formulation is slightly modified (see K1-developers, 2004). As background diffusivity, a minimum value is set for each level, suggested by Tsujino et al. (2000). The Smagorinsky's (1963) biharmonic viscosity is applied for the lateral momentum mixing, and its coefficient is dependent on the grid width and the strain rate, and its controlled by a single non- dimensional parameter whose values is taken to be 2.5. The constant coefficient biharmonic diffusion is applied with the coefficient value of 1.0E9 m4/s. The model is driven by the inter-annual forcing data set adopted by common ocean-ice reference experiments (CORE). The results are reported by focusing on heat transport in strong eddy activity regions, such as the Kuroshio

  16. Modeling of the Acoustic Reverberation Special Research Program deep ocean seafloor scattering experiments using a hybrid wave propagation simulation technique

    NASA Astrophysics Data System (ADS)

    Robertsson, Johan O. A.; Levander, Alan; Holliger, Klaus

    1996-02-01

    Quantitative modeling of bottom-interacting ocean acoustic waves is complicated by the long propagation ranges and by the complexity of the scattering targets. We employ a two-dimensional (2-D) hybrid technique combining Gaussian beam, finite difference, and Kirchhoff integral solutions of the wave equation to simulate ocean acoustic experiments within half of a convergence zone in the SOFAR channel. The 2-D modeling approach is reasonable due to the one-dimensional (1-D) velocity distribution in the water column and the strong lineation of the seafloor morphology parallel to the mid-ocean ridges. Full-waveform modeling of ocean acoustic data requires that the topography and the material properties of the seafloor are available at scales that are several orders of magnitude smaller than typical bathymetric sampling rates. We have therefore investigated the effects on the ocean acoustic response of a stochastic interpolation scheme used to generate seafloor models. For typical grazing angles of the incident wave field (approximately 5°-20°), we found that different stochastic realizations of the same seafloor segment (sampled at 200 m) yield an intrinsic uncertainty of the order of 3-8 dB in amplitude and 0.1-0.3 s in time for individual prominent events in the reverberant acoustic field. Hybrid simulations are compared to beam-formed ocean acoustic data collected during the Acoustic Reverberation Special Research Program (ARSRP) cruises. Side lobe noise in the observed acoustic data is simulated by adding band-limited white noise at -30 dB relative to the maximum intensity in the synthetic data. Numerical simulations can be limited to the response of only one of the mirror azimuth beams provided that the experimental geometry is suitably chosen. For the 2-D approximation to be valid, the cross-range resolution of the observed data must be smaller than the characteristic scale of seafloor lineations, and the beams of interest must be approximately perpendicular to

  17. Natural Air-Sea Flux of CO2 in Simulations of the NASA-GISS Climate Model: Sensitivity to the Physical Ocean Model Formulation

    NASA Technical Reports Server (NTRS)

    Romanou, A.; Gregg, Watson W.; Romanski, J.; Kelley, M.; Bleck, R.; Healy, R.; Nazarenko, L.; Russell, G.; Schmidt, G. A.; Sun, S.; Tausnev, N.

    2013-01-01

    Results from twin control simulations of the preindustrial CO2 gas exchange (natural flux of CO2) between the ocean and the atmosphere are presented here using the NASA-GISS climate model, in which the same atmospheric component (modelE2) is coupled to two different ocean models, the Russell ocean model and HYCOM. Both incarnations of the GISS climate model are also coupled to the same ocean biogeochemistry module (NOBM) which estimates prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2. Model intercomparison is carried out at equilibrium conditions and model differences are contrasted with biases from present day climatologies. Although the models agree on the spatial patterns of the air-sea flux of CO2, they disagree on the strength of the North Atlantic and Southern Ocean sinks mainly because of kinematic (winds) and chemistry (pCO2) differences rather than thermodynamic (SST) ones. Biology/chemistry dissimilarities in the models stem from the different parameterizations of advective and diffusive processes, such as overturning, mixing and horizontal tracer advection and to a lesser degree from parameterizations of biogeochemical processes such as gravitational settling and sinking. The global meridional overturning circulation illustrates much of the different behavior of the biological pump in the two models, together with differences in mixed layer depth which are responsible for different SST, DIC and nutrient distributions in the two models and consequently different atmospheric feedbacks (in the wind, net heat and freshwater fluxes into the ocean).

  18. Simulation of global warming with a simple coupled ocean-atmosphere model

    SciTech Connect

    Jin Xiangze; Zhang Xuehong

    1994-12-31

    A highly simplified ocean-atmosphere coupling system is established based on a two-dimensional oceanic thermohaline circulation model and an energy balance atmospheric model. Transient responses of the coupled system to a radiation forcing corresponding to the doubling of the atmospheric CO{sub 2} concentration have been investigated with an emphasis on the role of the model`s thermohaline circulation in the warming processes of the system. The results show that there are some significant differences between the Pacific and the Atlantic in their transient responses. On the whole, the warming in the Atlantic is slower in the surface and faster in the deep layers than those in the Pacific due to the process of the deep water formation in the northern North Atlantic, where the active convection and the downward vertical advection transport the surface thermal anomalies into the lower layers efficiently. On a hundred-year time scale, the thermohaline circulation in the North Atlantic is weakened. As a result, the warming in the upper layer of the northern North Atlantic will be further delayed because of the reduction of the northward heat transport.

  19. Do Coupled Climate Models Correctly SImulate the Upward Branch of the Deept Ocean Global Conveyor?

    SciTech Connect

    Sarmiento, Jorge L; Downes, Stephanie; Bianchi, Daniele

    2013-01-17

    The large-scale meridional overturning circulation (MOC) connects the deep ocean, a major reservoir of carbon, to the other components of the climate system and must therefore be accurately represented in Earth System Models. Our project aims to address the specific question of the pathways and mechanisms controlling the upwelling branch of the MOC, a subject of significant disagreement between models and observational syntheses, and among general circulation models. Observations of these pathways are limited, particularly in regions of complex hydrography such as the Southern Ocean. As such, we rely on models to examine theories of the overturning circulation, both physically and biogeochemically. This grant focused on a particular aspect of the meridional overturning circulation (MOC) where there is currently significant disagreement between models and observationally based analyses of the MOC, and amongst general circulation models. In particular, the research focused on addressing the following questions: 1. Where does the deep water that sinks in the polar regions rise to the surface? 2. What processes are responsible for this rise? 3. Do state-of-the-art coupled GCMs capture these processes? Our research had three key components: observational synthesis, model development and model analysis. In this final report we outline the key results from these areas of research for the 2007 to 2012 grant period. The research described here was carried out primarily by graduate student, Daniele Bianchi (now a Postdoc at McGill University, Canada), and Postdoc Stephanie Downes (now a Research Fellow at The Australian national University, Australia). Additional support was provided for programmers Jennifer Simeon as well as Rick Slater.

  20. A two-dimensional ocean model for long-term climatic simulations: Stability and coupling to atmospheric and sea ice models

    NASA Astrophysics Data System (ADS)

    Harvey, L. D. Danny

    1992-06-01

    A two-dimensional (latitude-depth) deep ocean model is presented which is coupled to a sea ice model and an Energy Balance Climate Model (EBCM), the latter having land-sea and surface-air resolution. The processes which occur in the ocean model are thermohaline overturning driven by the horizontal density gradient, shallow wind-driven overturning cells, convective overturning, and vertical and horizontal diffusion of heat and salt. The density field is determined from the temperature and salinity fields using a nonlinear equation of state. Mixed layer salinity is affected by evaporation, precipitation, runoff from continents, and sea ice freezing and melting, as well as by advective, convective, and diffusive exchanges with the deep ocean. The ocean model is first tested in an uncoupled mode, in which hemispherically symmetric mixed layer temperature and salinity, or salinity flux, are specified as upper boundary conditions. An experiment performed with previous models is repeated in which a mixed layer salinity perturbation is introduced in the polar half of one hemisphere after switching from a fixed salinity to a fixed salinity flux boundary condition. For small values of the vertical diffusion coefficient KV, the model undergoes self-sustained oscillations with a period of about 1500 years. With larger values of KV, the model locks into either an asymmetric mode with a single overturning cell spanning both hemispheres, or a symmetric quiescent state with downwelling near the equator, upwelling at high latitudes, and a warm deep ocean (depending on the value of KV). When the ocean model is forced with observed mixed layer temperature and salinity, no oscillations occur. The model successfully simulates the very weak meridional overturning and strong Antarctic Circumpolar Current at the latitudes of the Drake Passage. The coupled EBCM-deep ocean model displays internal oscillations with a period of 3000 years if the ocean fraction is uniform with latitude and KV

  1. Convective and moist vorticity vectors associated with tropical oceanic convection: A three-dimensional cloud-resolving model simulation

    NASA Astrophysics Data System (ADS)

    Gao, Shouting; Li, Xiaofan; Tao, Wei-Kuo; Shie, Chung-Lin; Lang, Steve

    2007-01-01

    The relationships between cloud hydrometeors and convective/moist vorticity vectors are investigated using hourly data from a three-dimensional, 5-day cloud-resolving model (CRM) simulation during the Tropical Rainfall Measuring Mission (TRMM) Kwajalein Experiment (KWAJEX). Vertical components of convective and moist vorticity vectors are highly correlated with cloud hydrometeors. The vertical components represent the interaction between horizontal vorticity and horizontal moist potential temperature/specific humidity gradient. The vertical components of convective and moist vorticity vectors can be used to study tropical oceanic convection in both two-dimensional and three-dimensional frameworks.

  2. Modeling of present-day atmosphere and ocean non-tidal de-aliasing errors for future gravity mission simulations

    NASA Astrophysics Data System (ADS)

    Dobslaw, Henryk; Bergmann-Wolf, Inga; Forootan, Ehsan; Dahle, Christoph; Mayer-Gürr, Torsten; Kusche, Jürgen; Flechtner, Frank

    2016-05-01

    A realistically perturbed synthetic de-aliasing model consistent with the updated Earth System Model of the European Space Agency is now available over the period 1995-2006. The dataset contains realizations of (1) errors at large spatial scales assessed individually for periods 10-30, 3-10, and 1-3 days, the S1 atmospheric tide, and sub-diurnal periods; (2) errors at small spatial scales typically not covered by global models of atmosphere and ocean variability; and (3) errors due to physical processes not represented in currently available de-aliasing products. The model is provided in two separate sets of Stokes coefficients to allow for a flexible re-scaling of the overall error level to account for potential future improvements in atmosphere and ocean mass variability models. Error magnitudes for the different frequency bands are derived from a small ensemble of four atmospheric and oceanic models. For the largest spatial scales up to d/o = 40 and periods longer than 24 h, those error estimates are approximately confirmed from a variance component estimation based on GRACE daily normal equations. Future mission performance simulations based on the updated Earth System Model and the realistically perturbed de-aliasing model indicate that for GRACE-type missions only moderate reductions of de-aliasing errors can be expected from a second satellite pair in a shifted polar orbit. Substantially more accurate global gravity fields are obtained when a second pair of satellites in an moderately inclined orbit is added, which largely stabilizes the global gravity field solutions due to its rotated sampling sensitivity.

  3. Ocean General Circulation Models

    SciTech Connect

    Yoon, Jin-Ho; Ma, Po-Lun

    2012-09-30

    1. Definition of Subject The purpose of this text is to provide an introduction to aspects of oceanic general circulation models (OGCMs), an important component of Climate System or Earth System Model (ESM). The role of the ocean in ESMs is described in Chapter XX (EDITOR: PLEASE FIND THE COUPLED CLIMATE or EARTH SYSTEM MODELING CHAPTERS). The emerging need for understanding the Earth’s climate system and especially projecting its future evolution has encouraged scientists to explore the dynamical, physical, and biogeochemical processes in the ocean. Understanding the role of these processes in the climate system is an interesting and challenging scientific subject. For example, a research question how much extra heat or CO2 generated by anthropogenic activities can be stored in the deep ocean is not only scientifically interesting but also important in projecting future climate of the earth. Thus, OGCMs have been developed and applied to investigate the various oceanic processes and their role in the climate system.

  4. Embedding a one-column ocean model in CAM5 for improving low-resolution MJO simulations

    NASA Astrophysics Data System (ADS)

    Lan, Yung-Yao; Tseng, Wan-Ling; Tsuang, Ben-Jei; Hsu, Huang-Hsiung; Shiu, Chein-Jung; Tu, Chia-Ying

    2015-04-01

    The impact of air-sea interaction on Madden-Julian oscillation (MJO) was investigated with the Community Atmosphere Model (CAM5) coupled to a one-column SIT (Snow/Ice/Thermocline) ocean model. The SIT embedding in CAM5 (CAM5-SIT) is developed to simulate high-resolution vertical mixing u-current, v-current, water temperature and salinity within 10-m depth and mid-resolution from 10-m depth down to the abyss. A more elaborate parameterization of vertical-mixing processes by the turbulent kinetic energy (TKE) equation provides realistic simulations of the turbulent mixing with a reasonable computational efficiency. Weak winds and large insolation resulted in SCAM a shallow mixed layer and large SST diurnal cycles at TOGA COARE during the IOP periods. By contrast, the strong wind (> 10 m/s) erroneously enhances mixed layer deepening and surface temperature cooling. Diurnal SST variation will strengthen the diurnal moistening in atmosphere and both are potential sources of MJO predictability. Time-evolving SST with a diurnal cycle strongly influences the onset and intensity of MJO convection. CAM5-SIT with half-hour coupling frequency significantly improves the MJO simulation over CAM5 with prescribed SST, fully coupled with Slab Ocean Model and with pop2 in wavenumber-frequency spectra of equatorial 850 hPa zonal wind (U850). The mean state SST and eastward propagating U850 and precipitation of CAM5-SIT results are similar to the observations. Using CAM5-SIT, the Rossby number of outgoing longwave radiation in wavenumber-frequency cross-spectra is weaker than observation, which is due to large-scale perturbation. The model distribution at high frequency and small-scale perturbation scheme in Kelvin wave are wider than observation. The coupled model experiments clearly demonstrate the importance of the diurnal SST in MJO eastward propagation. Keywords: Madden-Julian oscillation; CAM5-SIT; turbulent kinetic energy; SST; TOGA COARE

  5. Mesoscale ocean dynamics modeling

    SciTech Connect

    mHolm, D.; Alber, M.; Bayly, B.; Camassa, R.; Choi, W.; Cockburn, B.; Jones, D.; Lifschitz, A.; Margolin, L.; Marsden, L.; Nadiga, B.; Poje, A.; Smolarkiewicz, P.; Levermore, D.

    1996-05-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The ocean is a very complex nonlinear system that exhibits turbulence on essentially all scales, multiple equilibria, and significant intrinsic variability. Modeling the ocean`s dynamics at mesoscales is of fundamental importance for long-time-scale climate predictions. A major goal of this project has been to coordinate, strengthen, and focus the efforts of applied mathematicians, computer scientists, computational physicists and engineers (at LANL and a consortium of Universities) in a joint effort addressing the issues in mesoscale ocean dynamics. The project combines expertise in the core competencies of high performance computing and theory of complex systems in a new way that has great potential for improving ocean models now running on the Connection Machines CM-200 and CM-5 and on the Cray T3D.

  6. Modeling of Present-Day Atmosphere and Ocean Non-Tidal De-Aliasing Errors for Future Gravity Mission Simulations

    NASA Astrophysics Data System (ADS)

    Bergmann-Wolf, I.; Dobslaw, H.; Mayer-Gürr, T.

    2015-12-01

    A realistically perturbed synthetic de-aliasing model consistent with the updated Earth System Model of the European Space Agency (Dobslaw et al., 2015) is now available for the years 1995 -- 2006. The data-set contains realizations of (i) errors at large spatial scales assessed individually for periods between 10 -- 30, 3 -- 10, and 1 -- 3 days, the S1 atmospheric tide, and sub-diurnal periods; (ii) errors at small spatial scales typically not covered by global models of atmosphere and ocean variability; and (iii) errors due to physical processes not represented in currently available de-aliasing products. The error magnitudes for each of the different frequency bands are derived from a small ensemble of four atmospheric and oceanic models. In order to demonstrate the plausibility of the error magnitudes chosen, we perform a variance component estimation based on daily GRACE normal equations from the ITSG-Grace2014 global gravity field series recently published by the University of Graz. All 12 years of the error model are used to calculate empirical error variance-covariance matrices describing the systematic dependencies of the errors both in time and in space individually for five continental and four oceanic regions, and daily GRACE normal equations are subsequently employed to obtain pre-factors for each of those matrices. For the largest spatial scales up to d/o = 40 and periods longer than 24 h, errors prepared for the updated ESM are found to be largely consistent with noise of a similar stochastic character contained in present-day GRACE solutions. Differences and similarities identified for all of the nine regions considered will be discussed in detail during the presentation.Dobslaw, H., I. Bergmann-Wolf, R. Dill, E. Forootan, V. Klemann, J. Kusche, and I. Sasgen (2015), The updated ESA Earth System Model for future gravity mission simulation studies, J. Geod., doi:10.1007/s00190-014-0787-8.

  7. Atmospheric Weather Noise Characteristics in 20th Century Coupled Atmosphere-Ocean Model Simulations

    NASA Astrophysics Data System (ADS)

    Colfescu, Ioana; Schneider, Edwin

    2016-04-01

    The statistical characteristics of the atmospheric internal variability (hereafter weather noise) for surface pressure (PS) in 20th century simulations of a coupled general circulation model are documented. The weather noise is determined from post-industrial (1871-1998) Community Climate System Model 3 simulations by removing the SST and externally forced responses from the total fields.The forced responses are found from atmosphere-only simulations forced by the SST and external forcing of the coupled runs. The spatial patterns of the main modes of weather noise variability of the noise are found for boreal winter and summer from empirical orthogonal function (EOF) analyses performed globally, and for various regions, including the North Atlantic, the North Pacific, and the equatorial Pacific. The temporal characteristics of the modes are illustrated by power spectra and probability density functions (PDF) of the principal components (PC). Our findings show that, for two different realizations of weather noise, the variability is dominated by large scale spatial structures of the weather noise that resemble observed patterns, and that their relative amplitudes in the CGCM and AGCM simulations are very similar. The regional expression of the seasonally dependent AO-like or AAO-like dominant global pattern is also found in the regional analyses, giving similar PCs. The PCs in the CGCM and the corresponding SST forced AGCM simulations are uncorrelated, but the spectra and PDFs of the CGCM and AGCM PCs are similar. The temporal structures of the PCs are white at timescales larger than few months, so that these modes can be thought of as stochastic forcings (in time) for the climate system. The PDFs of the weather noise PCs are not statistically distinguishable from Gaussian distributions with the same standard deviation. The PDFs do not change substantially between the first and second half of the 20th century.

  8. [Simulation of polarization SAR imaging of ocean surface].

    PubMed

    Guo, Ding; Gu, Xing-Fa; Yu, Tao; Fernado, N; Li, Juan; Chen, Xing-Feng

    2011-10-01

    The polarization synthetic aperture radar (SAR) imaging simulation is of great significance to ocean surface scattering. According to the theory of wind-wave spectrum, rough ocean surface was modeled in the present paper using the two-scale-model. This treatment takes both the large scale and small scale surface into account. By using the velocity bunching (VB) theory, Bragg scattering model and the small perturbation model (SPM), the polarization SAR system can simulate the ocean surface with various parameters and ocean states. The effects of the parameters of ocean waves and the parameters of SAR system were analyzed. Finally, some useful conclusions were drawn, which are helpful for extracting the information of ocean surface. The method is an effective way in the ocean SAR design and the ocean surface research.

  9. [Simulation of polarization SAR imaging of ocean surface].

    PubMed

    Guo, Ding; Gu, Xing-Fa; Yu, Tao; Fernado, N; Li, Juan; Chen, Xing-Feng

    2011-10-01

    The polarization synthetic aperture radar (SAR) imaging simulation is of great significance to ocean surface scattering. According to the theory of wind-wave spectrum, rough ocean surface was modeled in the present paper using the two-scale-model. This treatment takes both the large scale and small scale surface into account. By using the velocity bunching (VB) theory, Bragg scattering model and the small perturbation model (SPM), the polarization SAR system can simulate the ocean surface with various parameters and ocean states. The effects of the parameters of ocean waves and the parameters of SAR system were analyzed. Finally, some useful conclusions were drawn, which are helpful for extracting the information of ocean surface. The method is an effective way in the ocean SAR design and the ocean surface research. PMID:22250525

  10. Tropical Oceanic Precipitation Processes over Warm Pool: 2D and 3D Cloud Resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Tao, W.- K.; Johnson, D.

    1998-01-01

    Rainfall is a key link in the hydrologic cycle as well as the primary heat source for the atmosphere, The vertical distribution of convective latent-heat release modulates the large-scale circulations of the tropics, Furthermore, changes in the moisture distribution at middle and upper levels of the troposphere can affect cloud distributions and cloud liquid water and ice contents. How the incoming solar and outgoing longwave radiation respond to these changes in clouds is a major factor in assessing climate change. Present large-scale weather and climate models simulate cloud processes only crudely, reducing confidence in their predictions on both global and regional scales. One of the most promising methods to test physical parameterizations used in General Circulation Models (GCMS) and climate models is to use field observations together with Cloud Resolving Models (CRMs). The CRMs use more sophisticated and physically realistic parameterizations of cloud microphysical processes, and allow for their complex interactions with solar and infrared radiative transfer processes. The CRMs can reasonably well resolve the evolution, structure, and life cycles of individual clouds and cloud systems, The major objective of this paper is to investigate the latent heating, moisture and momenti,im budgets associated with several convective systems developed during the TOGA COARE IFA - westerly wind burst event (late December, 1992). The tool for this study is the Goddard Cumulus Ensemble (CCE) model which includes a 3-class ice-phase microphysical scheme, The model domain contains 256 x 256 grid points (using 2 km resolution) in the horizontal and 38 grid points (to a depth of 22 km depth) in the vertical, The 2D domain has 1024 grid points. The simulations are performed over a 7 day time period. We will examine (1) the precipitation processes (i.e., condensation/evaporation) and their interaction with warm pool; (2) the heating and moisture budgets in the convective and

  11. Evaluation of precipitation over an oceanic region of Japan in convection-permitting regional climate model simulations

    NASA Astrophysics Data System (ADS)

    Murata, Akihiko; Sasaki, Hidetaka; Kawase, Hiroaki; Nosaka, Masaya

    2016-05-01

    We investigated the performance of a convection-permitting regional climate model with respect to precipitation in the present climate around the southwestern oceanic region of Japan. The effects of explicit representation of convective processes without cumulus parameterization can be properly estimated by using a model domain without complex topography or convoluted coastlines. The amounts of annual and monthly precipitation and the frequencies of daily and hourly precipitation were well reproduced by the convection-permitting model with a 2-km grid spacing, and its performance was better than that of a model with a coarser mesh. In particular, the frequencies of hourly precipitation in the convection-permitting simulation matched the observed frequencies for precipitation intensities below 20 mm h-1. Above intensities of 20 mm h-1, however, the convection-permitting model tended to overestimate the frequency of hourly precipitation. To explore the mechanism of this overestimation of heavy hourly precipitation, the sensitivity of the frequency distribution of precipitation to the horizontal resolution was tested by changing the horizontal grid spacing of the model from 2 to 4 km and then 1.5 km. The results showed that the overestimation was increased when the horizontal resolution was coarser, owing to spurious grid-scale precipitation, which causes heavy precipitation to be highly concentrated in a single grid. This spurious grid-scale precipitation may be caused by insufficient representation of convective downdrafts in convection-permitting simulations by models with coarser resolutions.

  12. An intermediate-complexity model for simulating marine biogeochemistry in deep time: Validation against the modern global ocean

    NASA Astrophysics Data System (ADS)

    Romaniello, Stephen J.; Derry, Louis A.

    2010-08-01

    We present a new high-resolution 1-D intermediate-complexity box model (ICBM) of ocean biogeochemical processes for paleoceanographic applications. The model contains 79 reservoirs in three regions that should be generally applicable throughout much of Earth history: (1) a stratified gyre region, (2) a high-latitude convective region, and (3) an upwelling region analogous to those found associated with eastern boundary currents. Transport processes are modeled as exchange fluxes between boxes and by eddy diffusion terms. Significant improvement in the representation of middepth oxygen budgets was achieved by implementing nonlocal mixing between the high-latitude surface and gyre thermocline reservoirs. The biogeochemical submodel simulates coupled C, N, P, O, and S systematics with explicit representation of microbial populations, using a process-based approach. Primary production follows Redfield stoichiometry, while water column remineralization is depth- and redox couple-dependent. Settling particulate organic matter is incorporated into a benthic submodel that accounts for burial and remineralization. The C/P ratio of burial depends on bottom water oxygen. Denitrification takes place both by classical and anammox pathways. The ICBM was tested against modern oceanographic observations from the Global Ocean Data Analysis Project, Joint Global Ocean Flux Study, and other databases. Comparisons of model output with circulation tracers including θ, salinity, CFC-12, and radiocarbon permit a test of the physical exchange scheme. Vertical profiles of biogeochemically reactive components in each of the three regions are in good agreement with observations. Under modern conditions the upwelling zone displays a pronounced oxygen minimum zone and water column denitrification, while these are not present in the high-latitude or gyre regions. Model-generated global fluxes also compare well to independent estimates of primary production, burial, and phosphorous and nitrogen

  13. Large eddy simulation in the ocean

    NASA Astrophysics Data System (ADS)

    Scotti, Alberto

    2010-12-01

    Large eddy simulation (LES) is a relative newcomer to oceanography. In this review, both applications of traditional LES to oceanic flows and new oceanic LES still in an early stage of development are discussed. The survey covers LES applied to boundary layer flows, traditionally an area where LES has provided considerable insight into the physics of the flow, as well as more innovative applications, where new SGS closure schemes need to be developed. The merging of LES with large-scale models is also briefly reviewed.

  14. Simulation Tool for GNSS Ocean Surface Reflections

    NASA Astrophysics Data System (ADS)

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-04-01

    GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surface heights, and patterns of the general ocean circulation. In the reflection zone the measurements may derive parameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have shown such results leading. The coming satellite missions, CYGNSS, COSMIC-2, and GEROS on the International Space Station, are focusing on GNSS ocean reflection measurements. Thus, simulation studies highlighting the assumptions for the data retrievals and the precision and the accuracy of such measurements are of interest for assessing the observational method. The theory of propagation of microwaves in the atmosphere is well established, and methods for propagation modeling range from ray tracing to numerical solutions to the wave equation. Besides ray tracing there are propagation methods that use mode theory and a finite difference solution to the parabolic equation. The presented propagator is based on the solution of the parabolic equation. The parabolic equation in our simulator is solved using the split-step sine transformation. The Earth's surface is modeled with the use of an impedance model. The value of the Earth impedance is given as a function of the range along the surface of the Earth. This impedance concept gives an accurate lower boundary condition in the determination of the electromagnetic field, and makes it possible to simulate reflections and the effects of transitions between different mediums. A semi-isotropic Philips spectrum is used to represent the air-sea interaction. Simulated GPS ocean surface reflections will be presented and discussed based on different ocean characteristics. The spectra of the simulated surface reflections will be analyzed

  15. Simple ocean carbon cycle models

    SciTech Connect

    Caldeira, K.; Hoffert, M.I.; Siegenthaler, U.

    1994-02-01

    Simple ocean carbon cycle models can be used to calculate the rate at which the oceans are likely to absorb CO{sub 2} from the atmosphere. For problems involving steady-state ocean circulation, well calibrated ocean models produce results that are very similar to results obtained using general circulation models. Hence, simple ocean carbon cycle models may be appropriate for use in studies in which the time or expense of running large scale general circulation models would be prohibitive. Simple ocean models have the advantage of being based on a small number of explicit assumptions. The simplicity of these ocean models facilitates the understanding of model results.

  16. An Ecosystem Model for the Simulation of Physical and Biological Oceanic Processes-IDAPAK User's Guide and Applications

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.; Arrigo, Kevin; Murtugudde, Ragu; Signorini, Sergio R.; Tai, King-Sheng

    1998-01-01

    This TM describes the development, testing, and application of a 4-component (phytoplankton, zooplankton, nitrate, and ammonium) ecosystem model capable of simulating oceanic biological processes. It also reports and documents an in-house software package (Interactive Data Analysis Package - IDAPAK) for interactive data analysis of geophysical fields, including those related to the forcing, verification, and analysis of the ecosystem model. Two regions were studied in the Pacific: the Warm Pool (WP) in the Equatorial Pacific (165 deg. E at the equator) and at Ocean Weather Station P (OWS P) in the Northeast Pacific (50 deg. N, 145 deg. W). The WP results clearly indicate that the upwelling at 100 meters correlates well with surface blooms. The upwelling events in late 1987 and 1990 produced dramatic increases in the surface layer values of all 4 ecosystem components, whereas the spring-summer deep mixing events, do not seem to incur a significant response in any of the ecosystem quantities. The OWS P results show that the monthly profiles of temperature, the annual cycles of solar irradiance, and 0- to 50-m integrated nitrate accurately reproduce observed values. Annual primary production is 190 gC/m(exp 2)/yr, which is consistent with recent observations but is much greater than earlier estimates.

  17. Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS).

    PubMed

    Nyamweya, Chrispine; Desjardins, Christopher; Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

    2016-01-01

    Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria. PMID:27030983

  18. Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS)

    PubMed Central

    Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

    2016-01-01

    Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September–May) and mixing (June–August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore—offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria. PMID:27030983

  19. Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS).

    PubMed

    Nyamweya, Chrispine; Desjardins, Christopher; Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

    2016-01-01

    Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria.

  20. Daily simulation using a three-dimensional atmosphere-ocean regional coupled model, CReSS-NHOES over the CINDY/DYNAMO observation region

    NASA Astrophysics Data System (ADS)

    Shinoda, T.; Yoshioka, M. K.; Aiki, H.; Kato, M.; Masunaga, H.; Smedstad, L. F.; Katsumata, M.; Yoneyama, K.; Higuchi, A.; Tsuboki, K.; Uyeda, H.

    2012-12-01

    We develop a three-dimensional atmosphere-ocean regional coupled-model with cloud-permitting scale; the atmosphere part is Cloud Resolving Storm Simulator (CReSS) and the ocean one is Non Hydrostatic Ocean model for the Earth Simulator (NHOES). This study shows results of daily simulation over the CINDY/DYNAMO observation region using CReSS-NHOES. Three types of sensitivity experiment are carried out to clarify the effect of the two-way coupled simulation and horizontal grid resolutions. One is the CReSS-NHOES two-way coupled simulation with horizontal grid spacing of 0.045 degree (approximately 4.8 km). Another two simulations are the CReSS simulations without coupling NHOES with horizontal grid spacing of 0.045 and 0.0225 degrees (approximately 2.4 km). The Global Spectral Model (GSM: Horizontal grid resolution is approximately 50 km) data provided by Japan Meteorological Agency (JMA) are used as the initial and boundary conditions of the atmosphere in CReSS and CReSS-NHOES. Three-dimensional Navy Coastal Ocean Model (NCOM) data provided by Naval Research Laboratory are used as the initial and boundary conditions of the ocean in CReSS-NHOES. The daily simulation is carried out for 36 hours from 12 UTC from October 1, 2011 to January 31, 2012 almost every day. We reproduce approximately 30-day surface pressure perturbation that should be related to the Madden-Julian Oscillation, half-day surface pressure perturbation that is related to the atmospheric tide, and the existence of low equivalent potential temperature airmass in the middle troposphere at a fixed observation point of the R/V Mirai (80.5E, 8S). However, the sharp vertical gradient of temperature and salinity at the bottom of the ocean mixed layer at the same point cannot be reproduced. The sensitivity of the coupling of the ocean model is not critical, because the difference of area-averaged sea surface temperature, sensible and latent heat fluxes from the sea surface is quite small. This should be

  1. Earth and ocean modeling

    NASA Technical Reports Server (NTRS)

    Knezovich, F. M.

    1976-01-01

    A modular structured system of computer programs is presented utilizing earth and ocean dynamical data keyed to finitely defined parameters. The model is an assemblage of mathematical algorithms with an inherent capability of maturation with progressive improvements in observational data frequencies, accuracies and scopes. The Eom in its present state is a first-order approach to a geophysical model of the earth's dynamics.

  2. A Markov track model for simulating Typhoon Tracks in North-Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Song, B.; Rajagopalan, B.; Lim, G. H.

    2014-12-01

    Typhoons typically occur during Jul-Sep, and the average number of occurrences per year in North Pacific and land falling over South Korea is ~25 and ~3, respectively. They cause enormous damage to infrastructure and lives and more so to developing countries in the region. Hence, to manage and mitigate this natural hazard, robust estimates of typhoon risks are necessary. Historical data is limited in length and incomplete in its variability. Thus, a methodology to generate a rich variety of realistic typhoon scenarios and the associated land fall risk along the coastal regions of their impact is important. To this end, we propose a spatial Markov track simulation model. In this, the domain is divided into 5x5 grids, and a typhoon in a grid box has ten states to transit to in the following 6-hour period - they are moving into one of the 8 neighboring grids, staying or fizzling out in the same grid. Based on historical 6-hourly typhoon track data (for the period 1977 - 2013) transition probabilities (i.e. probability of transitioning to one of the aforementioned ten states from the current 6-hour period to the following 6-hour period) are compute. Typhoon origination probabilities are also computed for each grid box. A track is initiated from one of the grid boxes based on the origination probabilities and it is propagated by the spatial Markov transition probabilities. A large number of synthetic tracks are generated for the spatial Markov probabilities from which estimates of land falling risks can be computed for different coastal segments. Wind speed magnitudes at each time step are generated by K-nearest neighbor resampling of the speeds of the historical tracks within each grid box based on the speed of the previous time step. A statistical distribution such as Weibull, can also be fitted for each neighborhood sample to simulate wind speeds. The Markov probabilities can also be estimated conditioned on large scale climate features that impact typhoon tracks to

  3. Responses of the Tropical Pacific to Wind Forcing as Observed by Spaceborne Sensors and Simulated by an Ocean General Circulation Model

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Tang, Qenqing; Atlas, Robert

    1996-01-01

    In this study, satellite observations, in situ measurements, and model simulations are combined to assess the oceanic response to surface wind forcing in the equatorial Pacific. The surface wind fields derived from observations by the spaceborne special sensor microwave imager (SSM/I) and from the operational products of the European Centre for Medium-Range Weather Forecasts (ECMWF) are compared. When SSM/I winds are used to force a primitive-equation ocean general circulation model (OGCM), they produce 3 C more surface cooling than ECMWF winds for the eastern equatorial Pacific during the cool phase of an El Nino-Southern Oscillation event. The stronger cooling by SSM/I winds is in good agreement with measurements at the moored buoys and observations by the advanced very high resolution radiometer, indicating that SSM/I winds are superior to ECMWF winds in forcing the tropical ocean. In comparison with measurements from buoys, tide gauges, and the Geosat altimeter, the OGCM simulates the temporal variations of temperature, steric, and sea level changes with reasonable realism when forced with the satellite winds. There are discrepancies between model simulations and observations that are common to both wind forcing fields, one of which is the simulation of zonal currents; they could be attributed to model deficiencies. By examining model simulations under two winds, vertical heat advection and uplifting of the thermocline are found to be the dominant factors in the anomalous cooling of the ocean mixed layer.

  4. A study of biases in simulation of the Indian Ocean basin mode and its capacitor effect in CMIP3/CMIP5 models

    NASA Astrophysics Data System (ADS)

    Tao, Weichen; Huang, Gang; Hu, Kaiming; Gong, Hainan; Wen, Guanhuan; Liu, Lin

    2016-01-01

    Based on 15 Coupled Model Intercomparison Project (CMIP) phase 3 (CMIP3) and 32 CMIP phase 5 (CMIP5) models, a detailed diagnosis was carried out to understand what compose the biases in simulation of the Indian Ocean basin mode (IOBM) and its capacitor effect. Cloud-radiation-SST (CRS) feedback and wind-evaporation-SST (WES) feedback are the two major atmospheric processes for SST changes. Most CMIP models simulate a stronger CRS feedback and a weaker WES feedback. During boreal fall of the El Niño/Southern Oscillation developing year and the following spring, there are weak biases of suppressed rainfall anomalies over the Maritime Continent and anomalous anticyclone over South Indian Ocean. Most CMIP models simulate reasonable short wave radiation (SWR) and weaker latent heat flux (LHF) anomalies. This leads to a weak bias of atmospheric processes. During winter, however, the rainfall anomalies are stronger due to west bias, and the anomalous anticyclone is comparable to observations. As such, most models simulate stronger SWR and reasonable LHF anomalies, leading to a strong bias of atmospheric processes. The thermocline feedback is stronger in most models. Though there is a deep bias of climatology thermocline, most models capture reasonable sea surface height-induced SST anomalies. Therefore, the effect of oceanic processes offset the weak bias of atmospheric processes in spring, and the tropical Indian Ocean warming persists into summer. However, anomalous northwest Pacific (NWP) anticyclone is weaker due to weak and west bias of the capacitor effect. The unrealistic western Pacific SST anomalies in models favor the westward extension of Rossby wave from the Pacific, weakening the effect of Kelvin wave from the Indian Ocean. Moreover, the western Pacific warming forces the NWP anticyclone move farther north than observations, suggesting a major forcing from the Pacific. Compared to CMIP3, CMIP5 models simulate the feedbacks more realistically and display

  5. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

  6. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  7. Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

    PubMed Central

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

    2013-01-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  8. Invigorating ocean boundary current systems around Australia during 1979-2014: As simulated in a near-global eddy-resolving ocean model

    NASA Astrophysics Data System (ADS)

    Feng, Ming; Zhang, Xuebin; Oke, Peter; Monselesan, Didier; Chamberlain, Matthew; Matear, Richard; Schiller, Andreas

    2016-05-01

    Ocean boundary currents, transporting water masses and marine biota along the coastlines, are important for regional climate and marine ecosystem functions. In this study, we review the dominant multi-decadal trends of ocean boundary currents around Australia. Using an eddy-resolving global ocean circulation model, this study has revealed that the major ocean boundary current systems around Australia, the East Australian Current (EAC), the Indonesian Throughflow (ITF), the Leeuwin Current, the South Australian Current and the Flinders Current, have strengthened during 1979-2014, consistent with existing observations. Eddy energetics in the EAC, the ITF/South Equatorial Current in the southeast Indian Ocean, and the Leeuwin Current have also enhanced during the same period. The multi-decadal strengthening of the ocean boundary current systems are primarily driven by large scale wind patterns associated with the dominant modes of climate variability and change - the phase shift of the Inter-decadal Pacific Oscillation/Pacific Decadal Oscillation strengthens the ITF and the Leeuwin Current/South Australian Current; and the poleward shift and strengthening of surface winds in the subtropical gyres reinforce the EAC and the Flinders Current. The invigorating ocean boundary current systems have induced extreme oceanographic conditions along the Australian coastlines in recent years, including the poleward shift of marine ecosystems off the east coast of Australia and the consecutive Ningaloo Niño - marine heatwave events off the west coast during 2011-2013. Understanding long-term trends and decadal variations of the ocean boundary currents is crucial to project future changes of the coastal marine systems under the influence of human-induced greenhouse gas forcing.

  9. Open ocean tide modelling

    NASA Technical Reports Server (NTRS)

    Parke, M. E.

    1978-01-01

    Two trends evident in global tidal modelling since the first GEOP conference in 1972 are described. The first centers on the incorporation of terms for ocean loading and gravitational self attraction into Laplace's tidal equations. The second centers on a better understanding of the problem of near resonant modelling and the need for realistic maps of tidal elevation for use by geodesists and geophysicists. Although new models still show significant differences, especially in the South Atlantic, there are significant similarities in many of the world's oceans. This allows suggestions to be made for future locations for bottom pressure gauge measurements. Where available, estimates of M2 tidal dissipation from the new models are significantly lower than estimates from previous models.

  10. The Parallelized Large-Eddy Simulation Model (PALM) version 4.0 for atmospheric and oceanic flows: model formulation, recent developments, and future perspectives

    NASA Astrophysics Data System (ADS)

    Maronga, B.; Gryschka, M.; Heinze, R.; Hoffmann, F.; Kanani-Sühring, F.; Keck, M.; Ketelsen, K.; Letzel, M. O.; Sühring, M.; Raasch, S.

    2015-02-01

    In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.

  11. The Parallelized Large-Eddy Simulation Model (PALM) version 4.0 for atmospheric and oceanic flows: model formulation, recent developments, and future perspectives

    NASA Astrophysics Data System (ADS)

    Maronga, B.; Gryschka, M.; Heinze, R.; Hoffmann, F.; Kanani-Sühring, F.; Keck, M.; Ketelsen, K.; Letzel, M. O.; Sühring, M.; Raasch, S.

    2015-08-01

    In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.

  12. Adaptive wavelet simulation of global ocean dynamics

    NASA Astrophysics Data System (ADS)

    Kevlahan, N. K.-R.; Dubos, T.; Aechtner, M.

    2015-07-01

    In order to easily enforce solid-wall boundary conditions in the presence of complex coastlines, we propose a new mass and energy conserving Brinkman penalization for the rotating shallow water equations. This penalization does not lead to higher wave speeds in the solid region. The error estimates for the penalization are derived analytically and verified numerically for linearized one dimensional equations. The penalization is implemented in a conservative dynamically adaptive wavelet method for the rotating shallow water equations on the sphere with bathymetry and coastline data from NOAA's ETOPO1 database. This code could form the dynamical core for a future global ocean model. The potential of the dynamically adaptive ocean model is illustrated by using it to simulate the 2004 Indonesian tsunami and wind-driven gyres.

  13. Simulations of the carbon cycle in the oceans

    SciTech Connect

    Not Available

    1992-07-01

    This study includes models of oceanic CO{sub 2} uptake. This perturbation simulation of carbon dioxide uptake gives strong support to estimates of oceanic uptake of fossil CO{sub 2} of order 2 GtC/yr. over the last decade. Carbon and carbon-nitrogen models are considered.

  14. Simulations of the carbon cycle in the oceans

    SciTech Connect

    Not Available

    1992-01-01

    This study includes models of oceanic CO{sub 2} uptake. This perturbation simulation of carbon dioxide uptake gives strong support to estimates of oceanic uptake of fossil CO{sub 2} of order 2 GtC/yr. over the last decade. Carbon and carbon-nitrogen models are considered.

  15. Simulation of anthropogenic CO2 uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

    NASA Astrophysics Data System (ADS)

    Wang, S.; Moore, J. K.; Primeau, F. W.; Khatiwala, S.

    2011-11-01

    The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant) inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the ΔC* method, and two are based on reconstructions of the Green function for the surface-to-interior transport, the TTD method and the maximum entropy inversion method (KPH). The KPH method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1) to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the KPH method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the KPH method are generally valid on the global scale, but may introduce significant errors in Cant estimates on regional scales. The KPH method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

  16. Simulating transoceanic migrations of young loggerhead sea turtles: merging magnetic navigation behavior with an ocean circulation model.

    PubMed

    Putman, Nathan F; Verley, Philippe; Shay, Thomas J; Lohmann, Kenneth J

    2012-06-01

    Young loggerhead sea turtles (Caretta caretta) from eastern Florida, USA, undertake a transoceanic migration in which they gradually circle the Sargasso Sea before returning to the North American coast. Loggerheads possess a 'magnetic map' in which regional magnetic fields elicit changes in swimming direction along the migratory pathway. In some geographic areas, however, ocean currents move more rapidly than young turtles can swim. Thus, the degree to which turtles can control their migratory movements has remained unclear. In this study, the movements of young turtles were simulated within a high-resolution ocean circulation model using several different behavioral scenarios, including one in which turtles drifted passively and others in which turtles swam briefly in accordance with experimentally derived data on magnetic navigation. Results revealed that small amounts of oriented swimming in response to regional magnetic fields profoundly affected migratory routes and endpoints. Turtles that engaged in directed swimming for as little as 1-3 h per day were 43-187% more likely than passive drifters to reach the Azores, a productive foraging area frequented by Florida loggerheads. They were also more likely to remain within warm-water currents favorable for growth and survival, avoid areas on the perimeter of the migratory route where predation risk and thermal conditions pose threats, and successfully return to the open-sea migratory route if carried into coastal areas. These findings imply that even weakly swimming marine animals may be able to exert strong effects on their migratory trajectories and open-sea distributions through simple navigation responses and minimal swimming.

  17. Simulating transoceanic migrations of young loggerhead sea turtles: merging magnetic navigation behavior with an ocean circulation model.

    PubMed

    Putman, Nathan F; Verley, Philippe; Shay, Thomas J; Lohmann, Kenneth J

    2012-06-01

    Young loggerhead sea turtles (Caretta caretta) from eastern Florida, USA, undertake a transoceanic migration in which they gradually circle the Sargasso Sea before returning to the North American coast. Loggerheads possess a 'magnetic map' in which regional magnetic fields elicit changes in swimming direction along the migratory pathway. In some geographic areas, however, ocean currents move more rapidly than young turtles can swim. Thus, the degree to which turtles can control their migratory movements has remained unclear. In this study, the movements of young turtles were simulated within a high-resolution ocean circulation model using several different behavioral scenarios, including one in which turtles drifted passively and others in which turtles swam briefly in accordance with experimentally derived data on magnetic navigation. Results revealed that small amounts of oriented swimming in response to regional magnetic fields profoundly affected migratory routes and endpoints. Turtles that engaged in directed swimming for as little as 1-3 h per day were 43-187% more likely than passive drifters to reach the Azores, a productive foraging area frequented by Florida loggerheads. They were also more likely to remain within warm-water currents favorable for growth and survival, avoid areas on the perimeter of the migratory route where predation risk and thermal conditions pose threats, and successfully return to the open-sea migratory route if carried into coastal areas. These findings imply that even weakly swimming marine animals may be able to exert strong effects on their migratory trajectories and open-sea distributions through simple navigation responses and minimal swimming. PMID:22573765

  18. Repulsive magnetic levitation-based ocean wave energy harvester with variable resonance: Modeling, simulation and experiment

    NASA Astrophysics Data System (ADS)

    Masoumi, Masoud; Wang, Ya

    2016-10-01

    This paper investigates a magnetic levitation characteristic used in a vibration based energy harvester, called repulsive magnetic scavenger (RMS). The RMS is capable of harvesting ocean wave energy with a unique repelling permanent magnet array, which provides a stronger and more uniform magnetic field, compared to its attracting magnetic counterparts. The levitating magnets are stacked together around a threaded rod so that the same pole is facing each other. Two fixed magnets placed with one at each end of the RMS provides a collocated harvesting and braking mechanism in the face of high amplitude vibrations. Magnets in the levitated magnet stack are separated by pole pieces which are made of metals to intensify the magnetic field strength. The effect of the thickness and the use of different materials with different permeability for pole pieces is also studied to obtain an optimal energy harvesting efficiency. Moreover, the procedure to find the restoring force applied to the levitating magnet stack is demonstrated. Then, the Duffing vibration equation of the harvester is solved and the frequency response function is calculated for various force amplitudes and electrical damping so as to investigate the effect of these parameters on the response of the system. Furthermore, the effect of the maximum displacement of the moving magnet stack on the natural frequency of the device is studied. And finally, Faraday's law is employed to estimate the output voltage and power of the system under the specified input excitation force. Experiments show that the output emf voltage of the manufactured prototype reaches up to 42 V for an excitation force with the frequency of 9 Hz and the maximum amplitude of 3.4 g.

  19. Simulated Atlantic Meridional Overturning Circulation in the 20th century with an ocean model forced by reanalysis-based atmospheric data sets

    NASA Astrophysics Data System (ADS)

    He, Yan-Chun; Drange, Helge; Gao, Yongqi; Bentsen, Mats

    2016-04-01

    Global ocean hindcast simulations for the period 1871-2009 have been run with the ocean-sea ice component of the Norwegian Earth System Model (NorESM-O), forced by an adjusted version of the Twentieth Century Reanalysis version 2 data set (20CRv2 data set), as well as by the commonly used second version of atmospheric forcing data set for the Coordinated Ocean-ice Reference Experiments phase-II (CORE-II) for the period 1948-2007 (hereafter CORE.v2 data set). The simulated Atlantic Meridional Overturning Circulation (AMOC) in the 20CR and the CORE simulations have comparable variability as well as mean strength during the last three decades of the integration. The simulated AMOC undergoes, however, distinctly different evolutions during the period 1948-1970, with a sharply declining strength in CORE but a gradual increase in 20CR. Sensitivity experiments suggest that differences in the wind forcing between CORE and 20CR have major impact on the simulated AMOCs during this period. It is furthermore found that differences in the air temperature between the two data sets do contribute to the differences in AMOC, but to a much lesser degree than the wind. An additional factor for the diverging AMOC in the two decades following 1948 is the inevitable switching of atmospheric forcing fields in 1948 in the CORE.v2-based runs due to the cyclic spin-up procedure of the ocean model. The latter is a fundamental issue for any ocean hindcast simulation. The ocean initial state mainly influence the actual value but to a lesser degree also the temporal evolution (variability) of AMOC. It may take about two decades for the AMOC to adjust to a new atmospheric state during the spin-up, although a dynamically balanced ocean initial state tends to reduce the adjustment time and the magnitude of the deviation, implying that an ocean model run with atmospheric forcing fields extending back in time, like 20CRv2, can be used to extend the reliable duration of CORE-type of simulations.

  20. Modelling the global coastal ocean.

    PubMed

    Holt, Jason; Harle, James; Proctor, Roger; Michel, Sylvain; Ashworth, Mike; Batstone, Crispian; Allen, Icarus; Holmes, Robert; Smyth, Tim; Haines, Keith; Bretherton, Dan; Smith, Gregory

    2009-03-13

    Shelf and coastal seas are regions of exceptionally high biological productivity, high rates of biogeochemical cycling and immense socio-economic importance. They are, however, poorly represented by the present generation of Earth system models, both in terms of resolution and process representation. Hence, these models cannot be used to elucidate the role of the coastal ocean in global biogeochemical cycles and the effects global change (both direct anthropogenic and climatic) are having on them. Here, we present a system for simulating all the coastal regions around the world (the Global Coastal Ocean Modelling System) in a systematic and practical fashion. It is based on automatically generating multiple nested model domains, using the Proudman Oceanographic Laboratory Coastal Ocean Modelling System coupled to the European Regional Seas Ecosystem Model. Preliminary results from the system are presented. These demonstrate the viability of the concept, and we discuss the prospects for using the system to explore key areas of global change in shelf seas, such as their role in the carbon cycle and climate change effects on fisheries. PMID:19087928

  1. Improved Climate Simulations through a Stochastic Parameterization of Ocean Eddies

    NASA Astrophysics Data System (ADS)

    Williams, Paul; Howe, Nicola; Gregory, Jonathan; Smith, Robin; Joshi, Manoj

    2016-04-01

    In climate simulations, the impacts of the sub-grid scales on the resolved scales are conventionally represented using deterministic closure schemes, which assume that the impacts are uniquely determined by the resolved scales. Stochastic parameterization relaxes this assumption, by sampling the sub-grid variability in a computationally inexpensive manner. This presentation shows that the simulated climatological state of the ocean is improved in many respects by implementing a simple stochastic parameterization of ocean eddies into a coupled atmosphere-ocean general circulation model. Simulations from a high-resolution, eddy-permitting ocean model are used to calculate the eddy statistics needed to inject realistic stochastic noise into a low-resolution, non-eddy-permitting version of the same model. A suite of four stochastic experiments is then run to test the sensitivity of the simulated climate to the noise definition, by varying the noise amplitude and decorrelation time within reasonable limits. The addition of zero-mean noise to the ocean temperature tendency is found to have a non-zero effect on the mean climate. Specifically, in terms of the ocean temperature and salinity fields both at the surface and at depth, the noise reduces many of the biases in the low-resolution model and causes it to more closely resemble the high-resolution model. The variability of the strength of the global ocean thermohaline circulation is also improved. It is concluded that stochastic ocean perturbations can yield reductions in climate model error that are comparable to those obtained by refining the resolution, but without the increased computational cost. Therefore, stochastic parameterizations of ocean eddies have the potential to significantly improve climate simulations. Reference PD Williams, NJ Howe, JM Gregory, RS Smith, and MM Joshi (2016) Improved Climate Simulations through a Stochastic Parameterization of Ocean Eddies. Journal of Climate, under revision.

  2. Ocean Wave Simulation Based on Wind Field.

    PubMed

    Li, Zhongyi; Wang, Hao

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates. PMID:26808718

  3. Ocean Wave Simulation Based on Wind Field.

    PubMed

    Li, Zhongyi; Wang, Hao

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

  4. Ocean Wave Simulation Based on Wind Field

    PubMed Central

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates. PMID:26808718

  5. Comparison of tropical pacific temperature and current simulations with two vertical mixing schemes embedded in an ocean general circulation model and reference to observations

    NASA Technical Reports Server (NTRS)

    Halpern, David; Chao, YI; Ma, Chung-Chun; Mechoso, Carlos R.

    1995-01-01

    The Pacanowski-Philander (PP) and Mellor-Yamada (MY) parameterization models of vertical mixing by turbulent processes were embedded in the Geophysical Fluid Dynamics Laboratory high-resolution ocean general circulation model of the tropical Pacific Ocean. All other facets of the numerical simulations were the same. Simulations were made for the 1987-1988 period. At the equator the MY simulation produced near-surface temperatures more uniform with depth, a deeper thermocline, a deeper core speed of the Equatorial Undercurrent, and a South Equatorial Current with greater vertical thickness compared with that computed with the PP method. Along 140 deg W, between 5 deg N and 10 deg N, both simulations were the same. Moored buoy current and temperature observations had been recorded by the Pacific Marine Environmental Laboratory at three sites (165 deg E, 140 deg W, 110 deg W) along the equator and at three sites (5 deg N, 7 deg N, 9 deg N) along 140 deg W. Simulated temperatures were lower than those observed in the near-surface layer and higher than those observed in the thermocline. Temperature simulations were in better agreement with observations compared to current simulations. At the equator, PP current and temperature simulations were more representative of the observations than MY simulations.

  6. Simulating Ocean Fertilization: Effectiveness and Unintended Consequences

    SciTech Connect

    Caldeira, K

    2002-11-03

    The primary objectives of this project are to assess, and improve our understanding of: (1) The effectiveness of various proposals to intentionally store carbon in the ocean through fertilization of the surface ocean with iron and/or macronutrients; and (2) Biologically relevant consequences of long-term and extensive ocean fertilization. The PISCES ocean biogeochemistry model, developed at the MPI in Hamburg, Germany, and IPSL in Saclay, France will be used in this study. This model considers Fe, N, P, O{sub 2}, Si, alkalinity, and carbon, in organic and inorganic, dissolved and particulate forms. The model represents diatoms, coccolithophorids, nitrogen fixers, and two classes of zooplankton. This model will be incorporated into the LLNL ocean GCM, which is already being applied to other problems in ocean carbon sequestration. After coupling the ocean biogeochemistry and circulation models, the reliability of this model will be evaluated by comparison to observations. These include observations of natural ecological and biogeochemical variation and observations of small-scale iron fertilization experiments (e.g. SOFeX, IRONEx). This strategy will produce a tested model with predictive capability that we will use to address the following important questions: What is the long-term effectiveness of ocean carbon sequestration via different ocean fertilization strategies? What are the long-term environmental consequences of prolonged or widespread ocean fertilization? What processes need to be included in the models, to better reproduce effects observed in iron fertilization experiments? What should the next experiment measure to better aid the models?

  7. Estimation of Fresh and Salt Water Fluxes and Transports in the Indian Ocean using satellite observations and model simulations

    NASA Astrophysics Data System (ADS)

    Bulusu, Subrahmanyam; Nyadjro, Ebenezer

    2014-05-01

    This study describes the fresh and salt water fluxes and transports in the Indian Ocean using satellite-derived salinity observations from the SMOS (Soil Moisture and Ocean Salinity) and Aquarius missions, and model outputs from the HYbrid Coordinate Ocean Model (HYCOM) and the Simple Ocean Data Assimilation (SODA) Re-analysis. Argo salinity data is used to validate the aforementioned salinity datasets. Salt budget estimations using SMOS salinity data show favorable comparisons with published results, with the potential for additional novel studies when more valid satellite-derived salinity data become available. On seasonal time scales, there is a considerable exchange of salt and fresh waters between the Bay of Bengal (BoB) and the Arabian Sea (AS) and vice versa. The pathways of the high/low salinity waters are identified using satellite observations. The Sea Surface Salinity (SSS) changes in the Southeastern Arabian Sea are as a result of the advection of low salinity waters from the BoB via coastal Kelvin waves. The long term mean salt transport shows seasonal reversals that are more pronounced in the northern Indian Ocean than in the southern Indian Ocean. Meridional salt transport is northward along the Somali Current (SC) in the Arabian Sea and the East India coastal Current (EICC) in the Bay of Bengal during the southwest monsoon season. The opposite holds during the northeast monsoon season. Mean zonal salt transport is of a higher magnitude than the meridional component and shows significant seasonal reversals in the equatorial region. Empirical Orthogonal Function (EOF) analyses of meridional salt transport show that the variability is primarily seasonally driven and is the result of seasonally reversing monsoonal winds and currents. The amplitudes of the EOFs suggest that the Indian Ocean dipole may also influence the variability. Spatially, the most variable regions are along the northeast African coast, and in the eastern Arabian Sea, the Bay of

  8. LLNL Ocean General Circulation Model

    2005-12-29

    The LLNL OGCM is a numerical ocean modeling tool for use in studying ocean circulation over a wide range of space and time scales, with primary applications to climate change and carbon cycle science.

  9. Climate warming due to increasing atmospheric CO2 - Simulations with a multilayer coupled atmosphere-ocean seasonal energy balance model

    NASA Technical Reports Server (NTRS)

    Li, Peng; Chou, Ming-Dah; Arking, Albert

    1987-01-01

    The transient response of the climate to increasing CO2 is studied using a modified version of the multilayer energy balance model of Peng et al. (1982). The main characteristics of the model are described. Latitudinal and seasonal distributions of planetary albedo, latitude-time distributions of zonal mean temperatures, and latitudinal distributions of evaporation, water vapor transport, and snow cover generated from the model and derived from actual observations are analyzed and compared. It is observed that in response to an atmospheric doubling of CO2, the model reaches within 1/e of the equilibrium response of global mean surface temperature in 9-35 years for the probable range of vertical heat diffusivity in the ocean. For CO2 increases projected by the National Research Council (1983), the model's transient response in annually and globally averaged surface temperatures is 60-75 percent of the corresponding equilibrium response, and the disequilibrium increases with increasing heat diffusivity of the ocean.

  10. Evaluation of the present climate simulated by the regional Eta model driven by the Brazilian Global coupled ocean-atmosphere Model

    NASA Astrophysics Data System (ADS)

    Chou, Sin Chan; Lyra, André; Juliano Silva, Adan; Nobre, Paulo

    2013-04-01

    The Eta Model is used operationally by INPE at the Centre for Weather Forecasts and Climate Studies (CPTEC) to produce weather forecasts over South America since 1997 and seasonal climate forecasts since 2002. The model has gone through upgrades along these years and is able to produce decadal integrations to downscale climate projections. Likewise, the INPE global atmospheric model has been coupled to MOM4 ocean model and decadal integrations in the period 1960-2105 was produced and contributed to the CMIP5 dataset. The development of the Brazilian Earth System Model (BESM) has been ongoing parallel to the development of the Brazilian regional earth system model (BESM-R). The objective of this work is to evaluate the regional Eta model nested in the BESM in the present climate simulations, from 1961-1990. The Eta model was configured with 20-km horizontal resolution and 38 layers, in a domain covering all South America. In the lower boundary, sea surface temperature was provided by the BESM and was updated daily during the regional integration, whereas the lateral boundaries were updated every 6 hours with the BESM atmospheric conditions. Continuous 30-year integrations were carried out by the regional model. Large scale circulation pattern at upper and low levels are shown in comparison with the respective BESM flow and evaluated against reanalyses. The regional model shows improvement in the precipitation and temperature pattern over the continent. Seasonal cycle of precipitation and temperature are also shown.

  11. Continuous assimilation of simulated Geosat altimetric sea level into an eddy-resolving numerical ocean model. I - Sea level differences. II - Referenced sea level differences

    NASA Technical Reports Server (NTRS)

    White, Warren B.; Tai, Chang-Kou; Holland, William R.

    1990-01-01

    The optimal interpolation method of Lorenc (1981) was used to conduct continuous assimilation of altimetric sea level differences from the simulated Geosat exact repeat mission (ERM) into a three-layer quasi-geostrophic eddy-resolving numerical ocean box model that simulates the statistics of mesoscale eddy activity in the western North Pacific. Assimilation was conducted continuously as the Geosat tracks appeared in simulated real time/space, with each track repeating every 17 days, but occurring at different times and locations within the 17-day period, as would have occurred in a realistic nowcast situation. This interpolation method was also used to conduct the assimilation of referenced altimetric sea level differences into the same model, performing the referencing of altimetric sea sevel differences by using the simulated sea level. The results of this dynamical interpolation procedure are compared with those of a statistical (i.e., optimum) interpolation procedure.

  12. Toward Submesocale Ocean Modelling and Observations for Global Ocean Forecast.

    NASA Astrophysics Data System (ADS)

    Drillet, Y.

    2014-12-01

    Mercator Ocean is the French oceanographic operational center involved in the development an operation of global high resolution ocean forecasting systems; it is part of the European Copernicus Marine service initiated during MyOcean project. Mercator Ocean currently delivers daily 1/12° global ocean forecast based on the NEMO model which allows for a good representation of mesoscale structures in main areas of the global ocean. Data assimilation of altimetry provides a precise initialization of the mesoscale structures while in situ observations, mainly based on the ARGO network, and satellite Sea Surface Temperature constrain water mass properties from the surface to intermediate depths. One of the main improvements scheduled in the coming years is the transitioning towards submesoscale permitting horizontal resolution (1/36°). On the basis of numerical simulations in selected areas and standard diagnostics developed to validate operational systems, we will discuss : i) The impact of the resolution increase at the basin scale. ii) Adequacy of numerical schemes, vertical resolution and physical parameterization. iii) Adequacy of currently implemented data assimilation procedures in particular with respect to new high resolution data set such as SWOT.

  13. Ocean Clutter Modeling for Ship Detection

    NASA Astrophysics Data System (ADS)

    Tao, Ding; Anfinsen, Stian Normann; Brekke, Camilla

    2013-03-01

    This work addresses the problem of covariance matrix estimation for ocean clutter modeling. For ship detection based on polarimetric synthetic aperture radar (Pol-SAR) imagery and constant false alarm rate (CFAR) detectors, accurate ocean clutter modeling is essential. The covariance matrix provides all the polarimetric information of the ocean clutter and its estimate is always involved in PolSAR detection [1]. The aim of this work is to investigate and compare the behavior of different covariance matrix estimators, i.e., the sample mean, fixedpoint, and maximum likelihood estimators. An approximate maximum likelihood covariance matrix estimator is also proposed and discussed for better computational efficiency. Their performances are evaluated in terms of the Kullback-Leibler (KL) matrix distance, and computational efficiency. Various textured ocean clutter conditions are considered, ranging from high texture to the non-textured case with Gaussian clutter. Experiments are performed on simulated ocean clutter data.

  14. Eddy Permitting Simulations of Biogeochemical Cycles in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Sumata, H.; Hashioka, T.; Suzuki, T.; Yamanaka, Y.

    2008-12-01

    A 3D ecosystem-biogeochemical model simulation for the global domain is performed in order to investigate variability of oceanic ecosystem on time scales of years to decades. The model has a horizontal resolution of 1/4 times 1/6 degrees and 51 vertical levels, covering the entire domain of the world ocean. The ecosystem- biogeochemical part of the model is based on NEMURO (North Pacific Ecosystem Model Used for Regional Oceanography), and is coupled with CCSR Ocean Component Model (COCO) version 4.3 by an offline technique. The physical part of the model is driven by the inter-annual forcing by common ocean-ice reference experiments (CORE) data from 1958 to 2004, and reasonably simulates inter-annual to decadal variabilities of ocean conditions related to biogeochemical cycles. These properties of the physical model with its eddying filed enable us to reproduce the realistic distributions of nutrients and plankton productions. Comparisons with historical station data show that the model also reasonably simulates the observed variabilities of ecosystem on time scales of years to decades. In particular, the model captures the transitions of biogeochemical cycles associated with regime shifts.

  15. Mixing parameterizations in ocean climate modeling

    NASA Astrophysics Data System (ADS)

    Moshonkin, S. N.; Gusev, A. V.; Zalesny, V. B.; Byshev, V. I.

    2016-03-01

    Results of numerical experiments with an eddy-permitting ocean circulation model on the simulation of the climatic variability of the North Atlantic and the Arctic Ocean are analyzed. We compare the ocean simulation quality with using different subgrid mixing parameterizations. The circulation model is found to be sensitive to a mixing parametrization. The computation of viscosity and diffusivity coefficients by an original splitting algorithm of the evolution equations for turbulence characteristics is found to be as efficient as traditional Monin-Obukhov parameterizations. At the same time, however, the variability of ocean climate characteristics is simulated more adequately. The simulation of salinity fields in the entire study region improves most significantly. Turbulent processes have a large effect on the circulation in the long-term through changes in the density fields. The velocity fields in the Gulf Stream and in the entire North Atlantic Subpolar Cyclonic Gyre are reproduced more realistically. The surface level height in the Arctic Basin is simulated more faithfully, marking the Beaufort Gyre better. The use of the Prandtl number as a function of the Richardson number improves the quality of ocean modeling.

  16. Simulation of optimal arctic routes using a numerical sea ice model based on an ice-coupled ocean circulation method

    NASA Astrophysics Data System (ADS)

    Nam, Jong-Ho; Park, Inha; Lee, Ho Jin; Kwon, Mi Ok; Choi, Kyungsik; Seo, Young-Kyo

    2013-06-01

    Ever since the Arctic region has opened its mysterious passage to mankind, continuous attempts to take advantage of its fastest route across the region has been made. The Arctic region is still covered by thick ice and thus finding a feasible navigating route is essential for an economical voyage. To find the optimal route, it is necessary to establish an efficient transit model that enables us to simulate every possible route in advance. In this work, an enhanced algorithm to determine the optimal route in the Arctic region is introduced. A transit model based on the simulated sea ice and environmental data numerically modeled in the Arctic is developed. By integrating the simulated data into a transit model, further applications such as route simulation, cost estimation or hindcast can be easily performed. An interactive simulation system that determines the optimal Arctic route using the transit model is developed. The simulation of optimal routes is carried out and the validity of the results is discussed.

  17. Dynamical downscaling of historical climate over CORDEX East Asia domain: A comparison of regional ocean-atmosphere coupled model to stand-alone RCM simulations

    NASA Astrophysics Data System (ADS)

    Zou, Liwei; Zhou, Tianjun; Peng, Dongdong

    2016-02-01

    The FROALS (flexible regional ocean-atmosphere-land system) model, a regional ocean-atmosphere coupled model, has been applied to the Coordinated Regional Downscaling Experiment (CORDEX) East Asia domain. Driven by historical simulations from a global climate system model, dynamical downscaling for the period from 1980 to 2005 has been conducted at a uniform horizontal resolution of 50 km. The impacts of regional air-sea couplings on the simulations of East Asian summer monsoon rainfall have been investigated, and comparisons have been made to corresponding simulations performed using a stand-alone regional climate model (RCM). The added value of the FROALS model with respect to the driving global climate model was evident in terms of both climatology and the interannual variability of summer rainfall over East China by the contributions of both the high horizontal resolution and the reasonably simulated convergence of the moisture fluxes. Compared with the stand-alone RCM simulations, the spatial pattern of the simulated low-level monsoon flow over East Asia and the western North Pacific was improved in the FROALS model due to its inclusion of regional air-sea coupling. The results indicated that the simulated sea surface temperature (SSTs) resulting from the regional air-sea coupling were lower than those derived directly from the driving global model over the western North Pacific north of 15°N. These colder SSTs had both positive and negative effects. On the one hand, they strengthened the western Pacific subtropical high, which improved the simulation of the summer monsoon circulation over East Asia. On the other hand, the colder SSTs suppressed surface evaporation and favored weaker local interannual variability in the SST, which led to less summer rainfall and weaker interannual rainfall variability over the Korean Peninsula and Japan. Overall, the reference simulation performed using the FROALS model is reasonable in terms of rainfall over the land area of

  18. Dense water formation and BiOS-induced variability in the Adriatic Sea simulated using an ocean regional circulation model

    NASA Astrophysics Data System (ADS)

    Dunić, Natalija; Vilibić, Ivica; Šepić, Jadranka; Somot, Samuel; Sevault, Florence

    2016-08-01

    A performance analysis of the NEMOMED8 ocean regional circulation model was undertaken for the Adriatic Sea during the period of 1961-2012, focusing on two mechanisms, dense water formation (DWF) and the Adriatic-Ionian Bimodal Oscillating System (BiOS), which drive interannual and decadal variability in the basin. The model was verified based on sea surface temperature and sea surface height satellite measurements and long-term in situ observations from several key areas. The model qualitatively reproduces basin-scale processes: thermohaline-driven cyclonic circulation and freshwater surface outflow along the western Adriatic coast, dense water dynamics, and the inflow of Ionian and Levantine waters to the Adriatic. Positive temperature and salinity biases are reported; the latter are particularly large along the eastern part of the basin, presumably because of the inappropriate introduction of eastern Adriatic rivers into the model. The highest warm temperature biases in the vertical direction were found in dense-water-collecting depressions in the Adriatic, indicating either an inappropriate quantification of DWF processes or temperature overestimation of modelled dense water. The decadal variability in the thermohaline properties is reproduced better than interannual variability, which is considerably underestimated. The DWF rates are qualitatively well reproduced by the model, being larger when preconditioned by higher basin-wide salinities. Anticyclonic circulation in the northern Ionian Sea was modelled only during the Eastern Mediterranean Transient. No other reversals of circulation that could be linked to BiOS-driven changes were modelled.

  19. Modeling ocean deep convection

    NASA Astrophysics Data System (ADS)

    Canuto, V. M.; Howard, A.; Hogan, P.; Cheng, Y.; Dubovikov, M. S.; Montenegro, L. M.

    The goal of this study is to assess models for Deep Convection with special emphasis on their use in coarse resolution ocean general circulation models. A model for deep convection must contain both vertical transport and lateral advection by mesoscale eddies generated by baroclinic instabilities. The first process operates mostly in the initial phases while the second dominates the final stages. Here, the emphasis is on models for vertical mixing. When mesoscales are not resolved, they are treated with the Gent and McWilliams parameterization. The model results are tested against the measurements of Lavender, Davis and Owens, 2002 (LDO) in the Labrador Sea. Specifically, we shall inquire whether the models are able to reproduce the region of " deepest convection," which we shall refer to as DC (mixed layer depths 800-1300 m). The region where it was measured by Lavender et al. (2002) will be referred to as the LDO region. The main results of this study can be summarized as follows. 3° × 3° resolution. A GFDL-type OGCM with the GISS vertical mixing model predicts DC in the LDO region where the vertical heat diffusivity is found to be 10 m 2 s -1, a value that is quite close to the one suggested by heuristic studies. No parameter was changed from the original GISS model. However, the GISS model also predicts some DC in a region to the east of the LDO region. 3° × 3° resolution. A GFDL-type OGCM with the KPP model (everything else being the same) does not predict DC in the LDO region where the vertical heat diffusivity is found to be 0.5 × 10 -4 m 2 s -1 which is the background value. The KPP model yields DC only to the east of the LDO region. 1° × 1° resolution. In this case, a MY2.5 mixing scheme predicts DC in the LDO region. However, it also predicts DC to the west, north and south of it, where it is not observed. The behavior of the KPP and MY models are somewhat anti-symmetric. The MY models yield too low a mixing in stably stratified flows since they

  20. View-Dependent Tessellation and Simulation of Ocean Surfaces

    PubMed Central

    Puig-Centelles, Anna; Ramos, Francisco; Chover, Miguel; Sbert, Mateu

    2014-01-01

    Modeling and rendering realistic ocean scenes have been thoroughly investigated for many years. Its appearance has been studied and it is possible to find very detailed simulations where a high degree of realism is achieved. Nevertheless, among the solutions to ocean rendering, real-time management of the huge heightmaps that are necessary for rendering an ocean scene is still not solved. We propose a new technique for simulating the ocean surface on GPU. This technique is capable of offering view-dependent approximations of the mesh while maintaining coherence among the extracted approximations. This feature is very important as most solutions previously presented must retessellate from the initial mesh. Our solution is able to use the latest extracted approximation when refining or coarsening the mesh. PMID:24672405

  1. The VIIRS Ocean Data Simulator Enhancements and Results

    NASA Technical Reports Server (NTRS)

    Robinson, Wayne D.; Patt, Fredrick S.; Franz, Bryan A.; Turpie, Kevin R.; McClain, Charles R.

    2011-01-01

    The VIIRS Ocean Science Team (VOST) has been developing an Ocean Data Simulator to create realistic VIIRS SDR datasets based on MODIS water-leaving radiances. The simulator is helping to assess instrument performance and scientific processing algorithms. Several changes were made in the last two years to complete the simulator and broaden its usefulness. The simulator is now fully functional and includes all sensor characteristics measured during prelaunch testing, including electronic and optical crosstalk influences, polarization sensitivity, and relative spectral response. Also included is the simulation of cloud and land radiances to make more realistic data sets and to understand their important influence on nearby ocean color data. The atmospheric tables used in the processing, including aerosol and Rayleigh reflectance coefficients, have been modeled using VIIRS relative spectral responses. The capabilities of the simulator were expanded to work in an unaggregated sample mode and to produce scans with additional samples beyond the standard scan. These features improve the capability to realistically add artifacts which act upon individual instrument samples prior to aggregation and which may originate from beyond the actual scan boundaries. The simulator was expanded to simulate all 16 M-bands and the EDR processing was improved to use these bands to make an SST product. The simulator is being used to generate global VIIRS data from and in parallel with the MODIS Aqua data stream. Studies have been conducted using the simulator to investigate the impact of instrument artifacts. This paper discusses the simulator improvements and results from the artifact impact studies.

  2. Precipitation extremes over Amazonia - atmospheric and oceanic associated features observed and simulated by HADGEM2-ES, CPTEC/INPE AGCM and Eta/CPTEC regional model

    NASA Astrophysics Data System (ADS)

    Cavalcanti, I. F.

    2013-05-01

    Extreme monthly cases of precipitation (positive and negative anomalies) over Amazonia are analyzed to show the atmospheric and oceanic related features and the ability of CPTEC AGCM and HADGEM2-ES in simulating them. Humidity flux variability over the Tropical Atlantic region is analyzed related to the precipitation variability over Amazonia. Besides the Pacific Ocean influence, the Amazonia precipitation is affected by the Tropical Atlantic Ocean, both by the SST and atmospheric flux humidity. Correlations between Atlantic SST and Amazonia precipitation show that there are specific months and areas that are affected by SST anomalies. The extreme cases are obtained from the Standardized Precipitation Index (SPI) applied to monthly data in four areas of Amazonia: northwest, northeast, west and east areas. The period of analysis is 1981 to 2010 to GPCP observed precipitation and CPTEC/INPE AGCM. As this AGCM is the base of the Brazilian Model of Earth System, its behavior on the mechanisms leading to extremes over Amazonia, compared to observations is discussed. Projections of extremes over the region are analyzed with results from CMIP5 HADGEM2-ES during 2073-2099 compared to 1979-2005. The regional Eta CPTEC model is also analyzed in two periods: 1960 to 1990 and 2040 to 2070, with boundary conditions of CMIP3 HADCM3 A1B scenario. The relevance of this analysis is to identify changes in frequency and intensity of extremes in the Amazon region in a higher resolution than the global models.

  3. The roles of vertical mixing, solar radiation, and wind stress in a model simulation of the sea surface temperature seasonal cycle in the tropical Pacfic Ocean

    NASA Technical Reports Server (NTRS)

    Chen, Dake; Busalacchi, Antonio J.; Rothstein, Lewis M.

    1994-01-01

    The climatological seasonal cycle of sea surface temperature (SST) in the tropical Pacific is simulated using a newly developed upper ocean model. The roles of vertical mixing, solar radiation, and wind stress are investigated in a hierarchy of numerical experiments with various combinations of vertical mixing algorithms and surface-forcing products. It is found that the large SST annual cycle in the eastern equatorial Pacific is, to a large extent, controlled by the annually varying mixed layer depth which, in turn, is mainly determined by the competing effects of solar radiation and wind forcing. With the application of our hybrid vertical mixing scheme the model-simulated SST annual cycle is much improved in both amplitude and phase as compared to the case of a constant mixed layer depth. Beside the strong effects on vertical mixing, solar radiation is the primary heating term in the surface layer heat budget, and wind forcing influences SST by driving oceanic advective processes that redistribute heat in the upper ocean. For example, the SST seasonal cycle in the western Pacific basically follows the semiannual variation of solar heating, and the cycle in the central equatorial region is significantly affected by the zonal advective heat flux associated with the seasonally reversing South Equatorial Current. It has been shown in our experiments that the amount of heat flux modification needed to eliminate the annual mean SST errors in the model is, on average, no larger than the annual mean uncertainties among the various surface flux products used in this study. Whereas a bias correction is needed to account for remaining uncertainties in the annual mean heat flux, this study demonstrates that with proper treatment of mixed layer physics and realistic forcing functions the seasonal variability of SST is capable of being simulated successfully in response to external forcing without relying on a relaxation or damping formulation for the dominant surface heat

  4. An overlooked problem in model simulations of the thermohaline circulation and heat transport in the Atlantic Ocean

    SciTech Connect

    Boening, C.W.; Holland, W.R.; Bryan, F.O.; Danabasoglu, G.; Mcwilliams, J.C. |

    1995-03-01

    Many models of the large-scale thermohaline circulation in the ocean exhibit strong zonally integrated upwelling in the midlatitude North Atlantic that significantly decreases the amount of deep water that is carried from the formation regions in the subpolar North Atlantic toward low latitudes and across the equator. In an analysis of results from the Community Modeling Effort using a suite of models with different horizontal resolution, wind and thermohaline forcing, and mixing parameters, it is shown that the upwelling is always concentrated in the western boundary layer between roughly 30 deg and 40 deg N. The vertical transport across 1000 m appears to be controlled by local dynamics and strongly depends on the horizontal resolution and mixing parameters of the model. It is suggested that in models with a realistic deep-water formation rate in the subpolar North Atlantic, the excessive upwelling can be considered as the prime reason for the typically too low meridional overturning rates and northward heat transports in the subtropical North Atlantic. A new isopycnal advection and mixing parameterization of tracer transports by mesoscale eddies yield substantial improvements in these integral measures of the circulation.

  5. Numerical simulations of oceanic oxygen cycling in the FAMOUS Earth-System model: FAMOUS-ES, version 1.0

    NASA Astrophysics Data System (ADS)

    Williams, J. H. T.; Totterdell, I. J.; Halloran, P. R.; Valdes, P. J.

    2014-02-01

    Addition and validation of an oxygen cycle to the ocean component of the FAMOUS climate model are described. Surface validation is carried out with respect to HadGEM2-ES where good agreement is found and where discrepancies are mainly attributed to disagreement in surface temperature structure between the models. The agreement between the models at depth (where observations are also used in the comparison) in the Southern Hemisphere is less encouraging than in the Northern Hemisphere. This is attributed to a combination of excessive surface productivity in FAMOUS' equatorial waters (and its concomitant effect on remineralisation at depth) and its reduced overturning circulation compared to HadGEM2-ES. For the entire Atlantic basin FAMOUS has a circulation strength of 12.7 ± 0.4 Sv compared to 15.0 ± 0.9 for HadGEM2-ES. The HadGEM2-ES data used in this paper were obtained from the online database of the fifth Coupled Model Intercomparison Project, CMIP5 (Taylor et al., 2012).

  6. NEMO Oceanic Model Optimization

    NASA Astrophysics Data System (ADS)

    Epicoco, I.; Mocavero, S.; Murli, A.; Aloisio, G.

    2012-04-01

    NEMO is an oceanic model used by the climate community for stand-alone or coupled experiments. Its parallel implementation, based on MPI, limits the exploitation of the emerging computational infrastructures at peta and exascale, due to the weight of communications. As case study we considered the MFS configuration developed at INGV with a resolution of 1/16° tailored on the Mediterranenan Basin. The work is focused on the analysis of the code on the MareNostrum cluster and on the optimization of critical routines. The first performance analysis of the model aimed at establishing how much the computational performance are influenced by the GPFS file system or the local disks and wich is the best domain decomposition. The results highlight that the exploitation of local disks can reduce the wall clock time up to 40% and that the best performance is achieved with a 2D decomposition when the local domain has a square shape. A deeper performance analysis highlights the obc_rad, dyn_spg and tra_adv routines are the most time consuming routines. The obc_rad implements the evaluation of the open boundaries and it has been the first routine to be optimized. The communication pattern implemented in obc_rad routine has been redesigned. Before the introduction of the optimizations all processes were involved in the communication, but only the processes on the boundaries have the actual data to be exchanged and only the data on the boundaries must be exchanged. Moreover the data along the vertical levels are "packed" and sent with only one MPI_send invocation. The overall efficiency increases compared with the original version, as well as the parallel speed-up. The execution time was reduced of about 33.81%. The second phase of optimization involved the SOR solver routine, implementing the Red-Black Successive-Over-Relaxation method. The high frequency of exchanging data among processes represent the most part of the overall communication time. The number of communication is

  7. An observing system simulation for Southern Ocean carbon dioxide uptake.

    PubMed

    Majkut, Joseph D; Carter, Brendan R; Frölicher, Thomas L; Dufour, Carolina O; Rodgers, Keith B; Sarmiento, Jorge L

    2014-07-13

    The Southern Ocean is critically important to the oceanic uptake of anthropogenic CO2. Up to half of the excess CO2 currently in the ocean entered through the Southern Ocean. That uptake helps to maintain the global carbon balance and buffers transient climate change from fossil fuel emissions. However, the future evolution of the uptake is uncertain, because our understanding of the dynamics that govern the Southern Ocean CO2 uptake is incomplete. Sparse observations and incomplete model formulations limit our ability to constrain the monthly and annual uptake, interannual variability and long-term trends. Float-based sampling of ocean biogeochemistry provides an opportunity for transforming our understanding of the Southern Ocean CO2 flux. In this work, we review current estimates of the CO2 uptake in the Southern Ocean and projections of its response to climate change. We then show, via an observational system simulation experiment, that float-based sampling provides a significant opportunity for measuring the mean fluxes and monitoring the mean uptake over decadal scales.

  8. Ocean Modeling of the North Atlantic

    NASA Technical Reports Server (NTRS)

    Seminar, A. J.

    1984-01-01

    Present modeling of the North Atlantic is inadequate and can be improved in a number of ways. A number of important physical processes are listed in five categories from the viewpoints of how they are treated in isolation, how they are usually represented in present ocean basin models, and how they may be better represented in future models. In the first two categories of vertical boundary processes and internal vertical mixing, parameterizations exist which can easily be incorporated into models and which will have important effects on the simulated structure of the North Atlantic. For the third catagory (mesoscale eddy effects), adequate parameterizations do not exist; but the order of magnitude of the effects is known from observational and process-model studies. A horizontal grid spacing of 100 km or less in required to allow parameterizations with this order of magnitude, as well as to resolve the time-averaged ocean fields. In the fourth category of large scale transports improvements are suggested by way of increased vertical resolution and by the requirement that lateral mixing due to eddies takes place on isopycnal surfaces. Model incorporation of the latter phenomenta is underway. In the fifth category of miscellaneous high-latitude processes, formulations for the treatment of sea ice are available for use. However, the treatment of gravitational instability, which is crucial to deepwater formation in the Atlantic Ocean, will require additional refinements to account for the unresolved physics of chimney formations in the open ocean and buoyant plumes near ocean boundaries.

  9. Global climate simulations at 3000-year intervals for the last 21 000 years with the GENMOM coupled atmosphere–ocean model

    USGS Publications Warehouse

    Alder, Jay R.; Hostetler, Steven W.

    2015-01-01

    We apply GENMOM, a coupled atmosphere–ocean climate model, to simulate eight equilibrium time slices at 3000-year intervals for the past 21 000 years forced by changes in Earth–Sun geometry, atmospheric greenhouse gases (GHGs), continental ice sheets, and sea level. Simulated global cooling during the Last Glacial Maximum (LGM) is 3.8 ◦C and the rate of post-glacial warming is in overall agreement with recently published temperature reconstructions. The greatest rate of warming occurs between 15 and 12 ka (2.4 ◦C over land, 0.7 ◦C over oceans, and 1.4 ◦C globally) in response to changes in radiative forcing from the diminished extent of the Northern Hemisphere (NH) ice sheets and increases in GHGs and NH summer insolation. The modeled LGM and 6 ka temperature and precipitation climatologies are generally consistent with proxy reconstructions, the PMIP2 and PMIP3 simulations, and other paleoclimate data–model analyses. The model does not capture the mid-Holocene “thermal maximum” and gradual cooling to preindustrial (PI) global temperature found in the data. Simulated monsoonal precipitation in North Africa peaks between 12 and 9 ka at values ∼ 50 % greater than those of the PI, and Indian monsoonal precipitation peaks at 12 and 9 ka at values ∼ 45 % greater than the PI. GENMOM captures the reconstructed LGM extent of NH and Southern Hemisphere (SH) sea ice. The simulated present-day Antarctica Circumpolar Current (ACC) is ∼ 48 % weaker than the observed (62 versus 119 Sv). The simulated present-day Atlantic Meridional Overturning Circulation (AMOC) of 19.3 ± 1.4 Sv on the Bermuda Rise (33◦ N) is comparable with observed value of 18.7 ± 4.8 Sv. AMOC at 33◦ N is reduced by ∼ 15 % during the LGM, and the largest post-glacial increase (∼ 11 %) occurs during the 15 ka time slice.

  10. Four simple ocean carbon models

    NASA Technical Reports Server (NTRS)

    Moore, Berrien, III

    1992-01-01

    This paper briefly reviews the key processes that determine oceanic CO2 uptake and sets this description within the context of four simple ocean carbon models. These models capture, in varying degrees, these key processes and establish a clear foundation for more realistic models that incorporate more directly the underlying physics and biology of the ocean rather than relying on simple parametric schemes. The purpose of this paper is more pedagogical than purely scientific. The problems encountered by current attempts to understand the global carbon cycle not only require our efforts but set a demand for a new generation of scientist, and it is hoped that this paper and the text in which it appears will help in this development.

  11. A simulation of synthetic aperture radar imaging of ocean waves

    NASA Technical Reports Server (NTRS)

    Swift, C. T.

    1974-01-01

    A simulation of radar imaging of ocean waves with synthetic aperture techniques is presented. The modelling is simplistic from the oceanographic and electromagnetic viewpoint in order to minimize the computational problems, yet reveal some of the physical problems associated with the imaging of moving ocean waves. The model assumes: (1) The radar illuminates a one-dimensional, one harmonic ocean wave. (2) The scattering is assumed to be governed by geometrical optics. (3) The radar is assumed to be down-looking, with Doppler processing (range processing is suppressed due to the one-dimensional nature of the problem). (4) The beamwidth of the antenna (or integration time) is assumed to be sufficiently narrow to restrict the specular points of the peaks and troughs of the wave. The results show that conventional processing of the image gives familiar results if the ocean waves are stationary. When the ocean wave dispersion relationship is satisfied, the image is smeared due to the motion of the specular points over the integration time. In effect, the image of the ocean is transferred to the near field of the synthetic aperture.

  12. Pathways of Atlantic Waters into the Arctic Ocean: Eddy-permitting ocean and sea ice simulations

    NASA Astrophysics Data System (ADS)

    Wekerle, Claudia; von Appen, Wilken-Jon; Danilov, Sergey; Jung, Thomas; Kanzow, Torsten; Schauer, Ursula; Timmermann, Ralph; Wang, Qiang

    2015-04-01

    Fram Strait is the only deep gateway connecting the central Arctic with the North Atlantic. Boundary currents on each side are responsible for the exchange of water masses between the Arctic and North Atlantic. The East Greenland Current (EGC) carries fresh and cold Arctic waters and sea ice southward, whereas the West Spitsbergen Current (WSC) carries warm Atlantic Waters (AW) into the Arctic Ocean. The complex topography in Fram Strait leads to a branching of the northward flowing WSC, with one branch recirculating between 78°N and 81°N which then joins the EGC. To date, the dynamics as well as the precise location of this recirculation are unclear. The goal of this research project is to quantify the amount and variability of AW which recirculates immediately in Fram Strait, and to investigate the role of atmospheric forcing and oceanic meso-scale eddies for the recirculation. We use simulations carried out with a global configuration of the Finite Element Sea ice-Ocean Model (FESOM) at eddy-permitting scales. The advantage of this model is the finite element discretization of the governing equations, which allows us to locally refine the mesh in areas of interest and keep it coarse in other parts of the global oceans without the need for traditional nesting. Here we will show the first results of the model validation. The model has ~9 km resolution in the Nordic Seas and Fram Strait and 1 deg south of 50°N. We assess the model capabilities in simulating the ocean circulation in the Nordic Seas and Fram Strait by comparing with the available observational data, e.g. with data from the Fram Strait oceanographic mooring array. The ocean volume and heat transport from the Atlantic Ocean into the Nordic Seas and at the Fram Strait are analyzed. Our results show that the model can capture some of the observed key ocean properties in our region of interest, while some tuning is required to further improve the model. In the next phase of this project we will focus

  13. Evaluating the deep-ocean circulation of a global ocean model using carbon isotopic ratios

    NASA Astrophysics Data System (ADS)

    Paul, André; Dutkiewicz, Stephanie; Gebbie, Jake; Losch, Martin; Marchal, Olivier

    2016-04-01

    We study the sensitivity of a global three-dimensional biotic ocean carbon-cycle model to the parameterizations of gas exchange and biological productivity as well as to deep-ocean circulation strength, and we employ the carbon isotopic ratios δ13C and Δ14C of dissolved inorganic carbon for a systematic evaluation against observations. Radiocarbon (Δ14C) in particular offers the means to assess the model skill on a time scale of 100 to 1000 years relevant to the deep-ocean circulation. The carbon isotope ratios are included as tracers in the MIT general circulation model (MITgcm). The implementation involves the fractionation processes during photosynthesis and air-sea gas exchange. We present the results of sixteen simulations combining two different parameterizations of the piston velocity, two different parameterizations of biological productivity (including the effect of iron fertilization) and four different overturning rates. These simulations were first spun up to equilibrium (more than 10,000 years of model simulation) and then continued from AD 1765 to AD 2002. For the model evaluation, we followed the OCMIP-2 (Ocean Carbon-Cycle Model Intercomparision Project phase two) protocol, comparing the results to GEOSECS (Geochemical Ocean Sections Survey) and WOCE (World Ocean Circulation Experiment) δ13C and natural Δ14C data in the world ocean. The range of deep natural Δ14C (below 1000 m) for our single model (MITgcm) was smaller than for the group of different OCMIP-2 models. Furthermore, differences between different model parameterizations were smaller than for different overturning rates. We conclude that carbon isotope ratios are a useful tool to evaluate the deep-ocean circulation. Since they are also available from deep-sea sediment records, we postulate that the simulation of carbon isotope ratios in a global ocean model will aid in estimating the deep-ocean circulation and climate during present and past.

  14. Diagnosis of the Marine Low Cloud Simulation in the NCAR Community Earth System Model (CESM) and the NCEP Global Forecast System (GFS)-Modular Ocean Model v4 (MOM4) coupled model

    SciTech Connect

    Xiao, Heng; Mechoso, C. R.; Sun, Rui; Han, J.; Pan, H. L.; Park, S.; Hannay, Cecile; Bretherton, Christopher S.; Teixeira, J.

    2014-07-25

    We present a diagnostic analysis of the marine low cloud climatology simulated by two state-of-the-art coupled atmosphere-ocean models: the NCAR Community Earth System Model (CESM) and the NCEP Global Forecasting System (GFS). In both models, the shallow convection and boundary layer turbulence parameterizations have been recently updated: both models now use a mass-flux scheme for the parameterization of shallow convection, and a turbulence parameterization capable of handling Stratocumulus (Sc)-topped Planetary Boundary Layers (PBLs). For shallow convection, both models employ a convective trigger function based on the concept of convective inhibition and both include explicit convective overshooting/penetrative entrainment formulation. For Sc-topped PBL, both models treat explicitly turbulence mixing and cloud-top entrainment driven by cloud-top radiative cooling. Our focus is on the climatological transition from Sc to shallow Cumulus (Cu)-topped PBL in the subtropical eastern oceans. We show that in the CESM the coastal Sc-topped PBLs in the subtropical Eastern Pacific are well-simulated but the climatological transition from Sc to shallow Cu is too abrupt and happens too close to the coast. By contrast, in the GFS coupled simulation the coastal Sc amount and PBL depth are severely underestimated while the transition from Sc to shallow Cu is ³delayed² and offshore Sc cover is too extensive in the subtropical Eastern Pacific. We discuss the possible connections between such differences in the simulations and differences in the parameterizations of shallow convection and boundary layer turbulence in the two models.

  15. Ensemble simulations of the ocean induced magnetic field

    NASA Astrophysics Data System (ADS)

    Irrgang, Christopher; Saynisch, Jan; Hagedoorn, Jan M.; Thomas, Maik

    2016-04-01

    The recent advent of new high-resolution datasets of electromagnetic induction allows novel combinations of observations and models. The ocean induced magnetic field provides the potential to indirectly observe the ocean general circulation and may be utilized by data assimilation techniques. The modelling of the ocean induced magnetic field is affected by various uncertainties that originate from errors in the input data and from the applied model itself. The amount of aggregated uncertainties and their effect on the modelling of electromagnetic induction in the ocean is unknown. However, the knowledge of model uncertainties is essential for many research questions. To investigate the uncertainty in the modelling of motional induction, ensemble simulations with an ocean general circulation model and an electromagnetic induction model are performed on the basis of different error scenarios. This approach allows to estimate both the spatial distribution and temporal variation of the uncertainty. The largest uncertainty in the motionally induced magnetic field occurs in the area of the Antarctic Circumpolar Current. Local maxima reach values of up to 0.7 nano Tesla (nT). The estimated global annual mean uncertainty in the motionally induced magnetic field ranges from 0.1 to 0.4 nT. The relative amount of uncertainty reaches up to 30 % of the induced magnetic signal strength with largest values in regions in the northern hemisphere. The major source of uncertainty is found to be introduced by the wind stress from the atmospheric forcing of the ocean model. In addition, the temporal evolution of the uncertainty in the motionally induced magnetic field shows distinct seasonal variations. Specific regions are identified which are robust with respect to the introduced uncertainties.

  16. A baroclinic quasigeostrophic open ocean model

    NASA Technical Reports Server (NTRS)

    Miller, R. N.; Robinson, A. R.; Haidvogel, D. B.

    1983-01-01

    A baroclinic quasigeostrophic open ocean model is presented, calibrated by a series of test problems, and demonstrated to be feasible and efficient for application to realistic mid-oceanic mesoscale eddy flow regimes. Two methods of treating the depth dependence of the flow, a finite difference method and a collocation method, are tested and intercompared. Sample Rossby wave calculations with and without advection are performed with constant stratification and two levels of nonlinearity, one weaker than and one typical of real ocean flows. Using exact analytical solutions for comparison, the accuracy and efficiency of the model is tabulated as a function of the computational parameters and stability limits set; typically, errors were controlled between 1 percent and 10 percent RMS after two wave periods. Further Rossby wave tests with realistic stratification and wave parameters chosen to mimic real ocean conditions were performed to determine computational parameters for use with real and simulated data. Finally, a prototype calculation with quasiturbulent simulated data was performed successfully, which demonstrates the practicality of the model for scientific use.

  17. Simulated and observed variability in ocean temperature and heat content.

    PubMed

    Achutarao, K M; Ishii, M; Santer, B D; Gleckler, P J; Taylor, K E; Barnett, T P; Pierce, D W; Stouffer, R J; Wigley, T M L

    2007-06-26

    Observations show both a pronounced increase in ocean heat content (OHC) over the second half of the 20th century and substantial OHC variability on interannual-to-decadal time scales. Although climate models are able to simulate overall changes in OHC, they are generally thought to underestimate the amplitude of OHC variability. Using simulations of 20th century climate performed with 13 numerical models, we demonstrate that the apparent discrepancy between modeled and observed variability is largely explained by accounting for changes in observational coverage and instrumentation and by including the effects of volcanic eruptions. Our work does not support the recent claim that the 0- to 700-m layer of the global ocean experienced a substantial OHC decrease over the 2003 to 2005 time period. We show that the 2003-2005 cooling is largely an artifact of a systematic change in the observing system, with the deployment of Argo floats reducing a warm bias in the original observing system.

  18. Climate science: Unexpected fix for ocean models

    NASA Astrophysics Data System (ADS)

    Kelly, Kathryn A.; Thompson, Luanne

    2016-07-01

    Computational models persistently underestimate strong currents that redistribute ocean heat. This problem is solved in models in which ocean eddies are damped by coupling of the atmosphere with the sea. See Letter p.533

  19. A simulation of the global ocean circulation with resolved eddies

    NASA Astrophysics Data System (ADS)

    Semtner, Albert J.; Chervin, Robert M.

    1988-12-01

    A multilevel primitive-equation model has been constructed for the purpose of simulating ocean circulation on modern supercomputing architectures. The model is designed to take advantage of faster clock speeds, increased numbers of processors, and enlarged memories of machines expected to be available over the next decade. The model allows global eddy-resolving simulations to be conducted in support of the World Ocean Circulation Experiment. Furthermore, global ocean modeling is essential for proper representation of the full range of oceanic and climatic phenomena. The first such global eddy-resolving ocean calculation is reported here. A 20-year integration of a global ocean model with ½° grid spacing and 20 vertical levels has been carried out with realistic geometry and annual mean wind forcing. The temperature and salinity are constrained to Levitus gridded data above 25-m depth and below 710-m depth (on time scales of 1 month and 3 years, respectively), but the values in the main thermocline are unconstrained for the last decade of the calculation. The final years of the simulation allow the spontaneous formation of waves and eddies through the use of scale-selective viscosity and diffusion. A quasi-equilibrium state shows many realistic features of ocean circulation, including unstable separating western boundary currents, the known anomalous northward heat transport in the South Atlantic, and a global compensation for the abyssal spread of North Atlantic Deep Water via a long chain of thermocline mass transport from the tropical Pacific, through the Indonesian archipelago, across the Indian Ocean, and around the southern tip of Africa. This chain of thermocline transport is perhaps the most striking result from the model, and eddies and waves are evident along the entire 20,000-km path of the flow. The modeled Gulf Stream separates somewhat north of Cape Hatteras, produces warm- and cold-core rings, and maintains its integrity as a meadering thermal front

  20. Ocean modelling on the CYBER 205 at GFDL

    NASA Technical Reports Server (NTRS)

    Cox, M.

    1984-01-01

    At the Geophysical Fluid Dynamics Laboratory, research is carried out for the purpose of understanding various aspects of climate, such as its variability, predictability, stability and sensitivity. The atmosphere and oceans are modelled mathematically and their phenomenology studied by computer simulation methods. The present state-of-the-art in the computer simulation of large scale oceans on the CYBER 205 is discussed. While atmospheric modelling differs in some aspects, the basic approach used is similar. The equations of the ocean model are presented along with a short description of the numerical techniques used to find their solution. Computational considerations and a typical solution are presented in section 4.

  1. Numerical simulation and prediction of coastal ocean circulation

    SciTech Connect

    Chen, P.

    1992-01-01

    Numerical simulation and prediction of coastal ocean circulation have been conducted in three cases. 1. A process-oriented modeling study is conducted to study the interaction of a western boundary current (WBC) with coastal water, and its responses to upstream topographic irregularities. It is hypothesized that the interaction of propagating WBC frontal waves and topographic Rossby waves are responsible for upstream variability. 2. A simulation of meanders and eddies in the Norwegian Coastal Current (NCC) for February and March of 1988 is conducted with a newly developed nested dynamic interactive model. The model employs a coarse-grid, large domain to account for non-local forcing and a fine-grid nested domain to resolve meanders and eddies. The model is forced by wind stresses, heat fluxes and atmospheric pressure corresponding Feb/March of 1988, and accounts for river/fjord discharges, open ocean inflow and outflow, and M[sub 2] tides. The simulation reproduced fairly well the observed circulation, tides, and salinity features in the North Sea, Norwegian Trench and NCC region in the large domain and fairly realistic meanders and eddies in the NCC in the nested region. 3. A methodology for practical coastal ocean hindcast/forecast is developed, taking advantage of the disparate time scales of various forcing and considering wind to be the dominant factor in affecting density fluctuation in the time scale of 1 to 10 days. The density field obtained from a prognostic simulation is analyzed by the empirical orthogonal function method (EOF), and correlated with the wind; these information are then used to drive a circulation model which excludes the density calculation. The method is applied to hindcast the circulation in the New York Bight for spring and summer season of 1988. The hindcast fields compare favorably with the results obtained from the prognostic circulation model.

  2. Adaptation of a general circulation model to ocean dynamics

    NASA Technical Reports Server (NTRS)

    Turner, R. E.; Rees, T. H.; Woodbury, G. E.

    1976-01-01

    A primitive-variable general circulation model of the ocean was formulated in which fast external gravity waves are suppressed with rigid-lid surface constraint pressires which also provide a means for simulating the effects of large-scale free-surface topography. The surface pressure method is simpler to apply than the conventional stream function models, and the resulting model can be applied to both global ocean and limited region situations. Strengths and weaknesses of the model are also presented.

  3. Impact of mesoscale ocean currents on sea ice in high-resolution Arctic ice and ocean simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxia; Maslowski, Wieslaw; Semtner, Albert J.

    1999-08-01

    A high-resolution sea ice model is designed for simulating the Arctic. The grid resolution is ˜18 km, and the domain contains the main Arctic Ocean, Nordic Seas, Canadian Archipelago, and the subpolar North Atlantic. The model is based on a widely used dynamic and thermodynamic model with more efficient numerics. The oceanic forcing is from an Arctic Ocean model with the same horizontal resolution as the ice model and 30 levels. The atmospheric forcing is from 3-day average 1990-1994 European Centre for Medium-Range Weather Forecasts operational data. Results from the ice model are compared against satellite passive-microwave observations and drifting buoys. The model realistically simulates ice tongues and eddies in the Greenland Sea. The mesoscale ocean eddies along the East Greenland Current (EGC) are demonstrated to be responsible for the presence of ice eddies and tongues out of the Greenland Sea ice edge. Large shear and divergence associated with the mesoscale ice eddies and strong ice drift, such as the one above the EGC, result in thinner and less compact ice. The mesoscale ocean eddies along the Alaskan Chukchi shelf break, the Northwind Ridge, and the Alpha-Mendeleyev Ridge are major contributors to mesoscale reduction of ice concentration, in addition to atmospheric storms which usually lead to a broad-scale reduction of ice concentration. The existence of mesoscale ocean eddies greatly increases nonuniformity of ice motion, which means stronger ice deformation and more open water. An eddy-resolving coupled ice-ocean model is highly recommended to adequately simulate the small but important percentage of open water in the Arctic pack ice, which can significantly change the heat fluxes from ocean to atmosphere and affect the global climate.

  4. A Parallel Ocean Model With Adaptive Mesh Refinement Capability For Global Ocean Prediction

    SciTech Connect

    Herrnstein, Aaron R.

    2005-12-01

    An ocean model with adaptive mesh refinement (AMR) capability is presented for simulating ocean circulation on decade time scales. The model closely resembles the LLNL ocean general circulation model with some components incorporated from other well known ocean models when appropriate. Spatial components are discretized using finite differences on a staggered grid where tracer and pressure variables are defined at cell centers and velocities at cell vertices (B-grid). Horizontal motion is modeled explicitly with leapfrog and Euler forward-backward time integration, and vertical motion is modeled semi-implicitly. New AMR strategies are presented for horizontal refinement on a B-grid, leapfrog time integration, and time integration of coupled systems with unequal time steps. These AMR capabilities are added to the LLNL software package SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) and validated with standard benchmark tests. The ocean model is built on top of the amended SAMRAI library. The resulting model has the capability to dynamically increase resolution in localized areas of the domain. Limited basin tests are conducted using various refinement criteria and produce convergence trends in the model solution as refinement is increased. Carbon sequestration simulations are performed on decade time scales in domains the size of the North Atlantic and the global ocean. A suggestion is given for refinement criteria in such simulations. AMR predicts maximum pH changes and increases in CO2 concentration near the injection sites that are virtually unattainable with a uniform high resolution due to extremely long run times. Fine scale details near the injection sites are achieved by AMR with shorter run times than the finest uniform resolution tested despite the need for enhanced parallel performance. The North Atlantic simulations show a reduction in passive tracer errors when AMR is applied instead of a uniform coarse resolution. No

  5. Development of ocean model LSOMG

    NASA Astrophysics Data System (ADS)

    Sachl, Libor; Martinec, Zdenek

    2015-04-01

    The purpose of this contribution is to present the ocean general circulation model LSOMG. It originates from the LSG (Maier-Reimer and Mikolajewicz, 1992) ocean model, however, significant number of changes has been made. LSOMG is a z-coordinate baroclinic ocean model which solves the primitive equations under the Boussinesq approximation. We intend to use the model for a various geophysical applications with the focus on paleoclimate studies. Hence, the model is not as complex as the current state-of-art climate models, such as the Modular Ocean Model or NEMO models. On the other hand, it is less computationally demanding. The changes and improvements in the code will be reported. One of the obvious changes is that the governing equations are no more discretized on the Arakawa E grid. The whole model has been rewritten on the Arakawa C grid. The main motivation is to avoid a coexistence of two solutions on the grid that evolve independently of each other. A more natural treatment of boundary conditions and simpler structure of the grid are additional advantages. Another significant change is the treatment of time tendencies. The system of equations is split to barotropic and baroclinic subsystems. Both subsystems may either be discretized at the same time points (as in the original LSG model), or their discretizations may be staggered in time as described in Griffies (2004). The original fully implicit barotropic time stepping scheme was found to significantly dissipate energy. Three different time stepping schemes are available instead. Namely, the predictor-corrector scheme of Griffies (2004), the generalized forward-backward scheme of Shchepetkin and McWilliams (2008) and the implicit free surface scheme of Campin et al. (2004). The first two schemes are intended to be used with the split-explicit model configuration for short-term studies whereas the third scheme is suitable for long-term studies, e.g. paleoclimate studies. The short-term studies may also

  6. Numerical Simulation of Salinity and Dissolved Oxygen at Perdido Bay and Adjacent Coastal Ocean

    EPA Science Inventory

    Environmental Fluid Dynamic Code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing fa...

  7. Impact of ocean-atmosphere coupling and high resolution on the simulation of medicanes over the Mediterranean Sea: multi-model analysis with Med-CORDEX and EURO-CORDEX runs

    NASA Astrophysics Data System (ADS)

    Gaertner, Miguel Angel; Jesús González-Alemán, Juan; Romera, Raquel; Domínguez, Marta; Gil, Victoria; Sánchez, Enrique; Gallardo, Clemente; Miglietta, Mario Marcelo; Walsh, Kevin; Sein, Dmitri; Somot, Samuel; dell'Aquila, Alessandro; Ahrens, Bodo; Colette, Augustin; Bastin, Sophie; Van Meijgaard, Erik; Nikulin, Grigory

    2016-04-01

    Medicanes are cyclones over the Mediterranean Sea having a tropical structure and a rather small size, for which the sea-atmosphere interaction plays a fundamental role. High resolution and ocean-atmosphere coupled RCM simulations performed in MedCORDEX and EURO-CORDEX projects are used to analyze the ability of RCMs to represent the observed characteristics of medicanes, and the impact of increasing resolution and using air-sea coupling on its simulation. An observational database based on satellite images combined with very high resolution simulations (Miglietta et al. 2013) is used as the reference for evaluating the simulations. The simulated medicanes do not coincide in general with the observed cases, so that the evaluation should be done in a statistical sense. The spatial distribution of medicanes is generally well simulated, while the monthly distribution reveals the difficulty of simulating the first medicanes appearing in September after the summer minimum. Large differences are found among models, supporting the use of multi-model ensembles. Interesting trade-offs are found for some models, as better values for intensity are associated to worse frequency values in one model, or relatively good values of frequency and intensity are obtained at the expense of a damped air-sea interaction in a model with spectral nudging. High resolution has a strong and positive impact on the frequency of simulated medicanes, while the effect on its intensity is less clear. Air-sea coupling reduces the medicane frequency, as could be expected due to a negative intensity feedback that is known for tropical cyclones. A preliminary analysis indicates that this feedback could depend on the oceanic mixed layer depth, increasing the interest of applying ocean-atmosphere coupled RCMs

  8. Mixing parametrizations for ocean climate modelling

    NASA Astrophysics Data System (ADS)

    Gusev, Anatoly; Moshonkin, Sergey; Diansky, Nikolay; Zalesny, Vladimir

    2016-04-01

    The algorithm is presented of splitting the total evolutionary equations for the turbulence kinetic energy (TKE) and turbulence dissipation frequency (TDF), which is used to parameterize the viscosity and diffusion coefficients in ocean circulation models. The turbulence model equations are split into the stages of transport-diffusion and generation-dissipation. For the generation-dissipation stage, the following schemes are implemented: the explicit-implicit numerical scheme, analytical solution and the asymptotic behavior of the analytical solutions. The experiments were performed with different mixing parameterizations for the modelling of Arctic and the Atlantic climate decadal variability with the eddy-permitting circulation model INMOM (Institute of Numerical Mathematics Ocean Model) using vertical grid refinement in the zone of fully developed turbulence. The proposed model with the split equations for turbulence characteristics is similar to the contemporary differential turbulence models, concerning the physical formulations. At the same time, its algorithm has high enough computational efficiency. Parameterizations with using the split turbulence model make it possible to obtain more adequate structure of temperature and salinity at decadal timescales, compared to the simpler Pacanowski-Philander (PP) turbulence parameterization. Parameterizations with using analytical solution or numerical scheme at the generation-dissipation step of the turbulence model leads to better representation of ocean climate than the faster parameterization using the asymptotic behavior of the analytical solution. At the same time, the computational efficiency left almost unchanged relative to the simple PP parameterization. Usage of PP parametrization in the circulation model leads to realistic simulation of density and circulation with violation of T,S-relationships. This error is majorly avoided with using the proposed parameterizations containing the split turbulence model

  9. Stochastic simulations of ocean waves: An uncertainty quantification study

    NASA Astrophysics Data System (ADS)

    Yildirim, B.; Karniadakis, George Em

    2015-02-01

    The primary objective of this study is to introduce a stochastic framework based on generalized polynomial chaos (gPC) for uncertainty quantification in numerical ocean wave simulations. The techniques we present can be easily extended to other numerical ocean simulation applications. We perform stochastic simulations using a relatively new numerical method to simulate the HISWA (Hindcasting Shallow Water Waves) laboratory experiment for directional near-shore wave propagation and induced currents in a shallow-water wave basin. We solve the phased-averaged equation with hybrid discretization based on discontinuous Galerkin projections, spectral elements, and Fourier expansions. We first validate the deterministic solver by comparing our simulation results against the HISWA experimental data as well as against the numerical model SWAN (Simulating Waves Nearshore). We then perform sensitivity analysis to assess the effects of the parametrized source terms, current field, and boundary conditions. We employ an efficient sparse-grid stochastic collocation method that can treat many uncertain parameters simultaneously. We find that the depth-induced wave-breaking coefficient is the most important parameter compared to other tunable parameters in the source terms. The current field is modeled as random process with large variation but it does not seem to have a significant effect. Uncertainty in the source terms does not influence significantly the region before the submerged breaker whereas uncertainty in the incoming boundary conditions does. Considering simultaneously the uncertainties from the source terms and boundary conditions, we obtain numerical error bars that contain almost all experimental data, hence identifying the proper range of parameters in the action balance equation.

  10. Microscopic, Macroscopic, and Megascopic Melts: a simple model to synthesize simulation, spectroscopy, shock, and sink/float constraints on silicate melts and magma oceans

    NASA Astrophysics Data System (ADS)

    Asimow, P. D.; Thomas, C.; Wolf, A. S.

    2012-12-01

    Silicate melts are the essential agents of planetary differentiation and evolution. Their phase relations, element partitioning preferences, density, and transport properties determine the fates of heat and mass flow in the high-temperature interior of active planets. In the early Earth and in extrasolar super-Earth-mass terrestrial planets it is these properties at very high pressure (> 100 GPa) that control the evolution from possible magma oceans to solid-state convecting mantles. Yet these melts are complex, dynamic materials that present many challenges to experimental, theoretical, and computational understanding or prediction of their properties. There has been encouraging convergence among various approaches to understanding the structure and dynamics of silicate melts at multiple scales: nearest- and next-nearest neighbor structural information is derived from spectroscopic techniques such as high-resolution multinuclear NMR; first-principles molecular dynamics probe structure and dynamics at scales up to hundreds of atoms; Archimedean, ultrasonic, sink/float, and shock wave methods probe macroscopic properties (and occasionally dynamics); and deformation and diffusion experiments probe dynamics at macroscopic scale and various time scales. One challenge that remains to integrating all this information is a predictive model of silicate liquid structure that agrees with experiments and simulation both at microscopic and macroscopic scale. In addition to our efforts to collect macroscopic equation of state data using shock wave methods across ever-wider ranges of temperature, pressure, and composition space, we have introduced a simple model of coordination statistics around cations that can form the basis of a conceptual and predictive link across scales and methods. This idea is explored in this presentation specifically with regard to the temperature dependence of sound speed in ultramafic liquids. This is a highly uncertain quantity and yet it is key, in

  11. Extinction of the northern oceanic deep convection in an ensemble of climate model simulations of the 20th and 21st centuries

    NASA Astrophysics Data System (ADS)

    Brodeau, Laurent; Koenigk, Torben

    2016-05-01

    We study the variability and the evolution of oceanic deep convection in the northern North Atlantic and the Nordic Seas from 1850 to 2100 using an ensemble of 12 climate model simulations with EC-Earth. During the historical period, the model shows a realistic localization of the main sites of deep convection, with the Labrador Sea accounting for most of the deep convective mixing in the northern hemisphere. Labrador convection is partly driven by the NAO (correlation of 0.6) and controls part of the variability of the AMOC at the decadal time scale (correlation of 0.6 when convection leads by 3-4 years). Deep convective activity in the Labrador Sea starts to decline and to become shallower in the beginning of the twentieth century. The decline is primarily caused by a decrease of the sensible heat loss to the atmosphere in winter resulting from increasingly warm atmospheric conditions. It occurs stepwise and is mainly the consequence of two severe drops in deep convective activity during the 1920s and the 1990s. These two events can both be linked to the low-frequency variability of the NAO. A warming of the sub-surface, resulting from reduced convective mixing, combines with an increasing influx of freshwater from the Nordic Seas to rapidly strengthen the surface stratification and prevent any possible resurgence of deep convection in the Labrador Sea after the 2020s. Deep convection in the Greenland Sea starts to decline in the 2020s, until complete extinction in 2100. As a response to the extinction of deep convection in the Labrador and Greenland Seas, the AMOC undergoes a linear decline at a rate of about -0.3 Sv per decade during the twenty-first century.

  12. Transport simulation of the radionuclide from the shelf to open ocean around Fukushima

    NASA Astrophysics Data System (ADS)

    Miyazawa, Yasumasa; Masumoto, Yukio; Varlamov, Sergey M.; Miyama, Toru

    2012-12-01

    We simulate radionuclide distribution in the ocean due to direct emission from the Fukushima Daiichi nuclear power plant (FNPP) for the period from 21 March to 6 May 2011. Dispersion of Cesium-137 is modeled by a transport equation with advection and diffusion by three dimensional ocean current. The ocean current data are provided from a data-assimilative, tide-resolving ocean general circulation model with horizontal resolution of 1/36°. Results show that the radionuclide expands from the shelf region into open ocean in April by the ocean currents and farther transported eastward along the Kuroshio Extension front in May. Sensitivity experiments demonstrate that the mesoscale geostrophic currents basically governed the transport processes in the open ocean after April. In the shelf region, on the other hand, the wind-driven currents facilitate the north-south extension of the radionuclide distribution through the repeated generations of the shelf waves. Influences of tide and river discharges cannot be neglected.

  13. Simulated and observed variability in ocean temperature and heat content

    PubMed Central

    AchutaRao, K. M.; Ishii, M.; Santer, B. D.; Gleckler, P. J.; Taylor, K. E.; Barnett, T. P.; Pierce, D. W.; Stouffer, R. J.; Wigley, T. M. L.

    2007-01-01

    Observations show both a pronounced increase in ocean heat content (OHC) over the second half of the 20th century and substantial OHC variability on interannual-to-decadal time scales. Although climate models are able to simulate overall changes in OHC, they are generally thought to underestimate the amplitude of OHC variability. Using simulations of 20th century climate performed with 13 numerical models, we demonstrate that the apparent discrepancy between modeled and observed variability is largely explained by accounting for changes in observational coverage and instrumentation and by including the effects of volcanic eruptions. Our work does not support the recent claim that the 0- to 700-m layer of the global ocean experienced a substantial OHC decrease over the 2003 to 2005 time period. We show that the 2003–2005 cooling is largely an artifact of a systematic change in the observing system, with the deployment of Argo floats reducing a warm bias in the original observing system. PMID:17578928

  14. Investigation of Coastal Ocean Response to Landfalling Hurricane Using a Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) Model: Idealized Experiments

    NASA Astrophysics Data System (ADS)

    Zambon, J. B.; He, R.; Warner, J. C.

    2008-12-01

    We investigate coupling mechanisms among ocean, atmosphere and waves during land-falling hurricanes on an idealized coastal ocean setting with the recently developed Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system. The atmosphere is represented by the Weather Research and Forecasting (WRF) model, the ocean by the Regional Ocean Modeling System (ROMS), and waves by the Simulating Waves Nearshore (SWAN) model, with data fields exchanged by the Model Coupling Toolkit (MCT) during concurrent simulations. Coupled model simulations are performed on an idealized ocean grid with a linear coastline and bathymetry representative of a typical coastal shelf. We focus on ocean responses before, during and after landfall. Six sensitivity experiments are performed by switching on and off the two- way communications of various ocean, atmosphere and wave state variables. Model solutions clearly demonstrate complex interactions between the atmosphere, ocean, and wave responses, highlighting the importance and necessity of using an advanced, interdisciplinary, coupled modeling system to study the dynamics of landfalling hurricanes

  15. Global ocean modeling on the Connection Machine

    SciTech Connect

    Smith, R.D.; Dukowicz, J.K.; Malone, R.C.

    1993-10-01

    The authors have developed a version of the Bryan-Cox-Semtner ocean model (Bryan, 1969; Semtner, 1976; Cox, 1984) for massively parallel computers. Such models are three-dimensional, Eulerian models that use latitude and longitude as the horizontal spherical coordinates and fixed depth levels as the vertical coordinate. The incompressible Navier-Stokes equations, with a turbulent eddy viscosity, and mass continuity equation are solved, subject to the hydrostatic and Boussinesq approximations. The traditional model formulation uses a rigid-lid approximation (vertical velocity = 0 at the ocean surface) to eliminate fast surface waves. These waves would otherwise require that a very short time step be used in numerical simulations, which would greatly increase the computational cost. To solve the equations with the rigid-lid assumption, the equations of motion are split into two parts: a set of twodimensional ``barotropic`` equations describing the vertically-averaged flow, and a set of three-dimensional ``baroclinic`` equations describing temperature, salinity and deviations of the horizontal velocities from the vertically-averaged flow.

  16. Evidence of systematic biases in ocean surface heat fluxes simulated by AGCMs

    SciTech Connect

    Gleckler, P.J.; Randall, D.A.

    1995-01-01

    The Atmospheric Model Intercomparison Project has provided a unique opportunity to evaluate atmospheric general circulation model (AGCM) simulations made with realistic boundary forcing. Here we report on some results from AMIP Subproject No. 5, making use of a suite of observationally-based estimates of ocean surface heat fluxes to evaluate the seasonal cycle of surface heating as simulated by AGCMs.

  17. Observationally-Based Data/Model Metrics from the Southern Ocean Climate Model Atlas

    NASA Astrophysics Data System (ADS)

    Abell, J.; Russell, J. L.; Goodman, P. J.

    2015-12-01

    The Southern Ocean Climate Model Atlas makes available observationally-based standardized data/model metrics of the latest simulations of climate and projections of climate change from available climate models. Global climate model simulations differ greatly in the Southern Ocean, so the development of consistent, observationally-based metrics, by which to assess the fidelity of model simulations is essential. We will present metrics showing and quantifying the results of the modern day climate simulations over the Southern Ocean from models submitted as part of the CMIP5/IPCC-AR5 process. Our analysis will focus on the simulations of the temperature, salinity and carbon at various depths and along significant hydrographic sections. The models exhibit different skill levels with various metrics between models and also within individual models.

  18. Modeling and Assimilating Ocean Color Radiances

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2012-01-01

    Radiances are the source of information from ocean color sensors to produce estimates of biological and geochemical constituents. They potentially provide information on various other aspects of global biological and chemical systems, and there is considerable work involved in deriving new information from these signals. Each derived product, however, contains errors that are derived from the application of the radiances, above and beyond the radiance errors. A global biogeochemical model with an explicit spectral radiative transfer model is used to investigate the potential of assimilating radiances. The results indicate gaps in our understanding of radiative processes in the oceans and their relationships with biogeochemical variables. Most important, detritus optical properties are not well characterized and produce important effects of the simulated radiances. Specifically, there does not appear to be a relationship between detrital biomass and its optical properties, as there is for chlorophyll. Approximations are necessary to get beyond this problem. In this reprt we will discuss the challenges in modeling and assimilation water-leaving radiances and the prospects for improving our understanding of biogeochemical process by utilizing these signals.

  19. Warm World Ocean Thermohaline Circulation Model

    NASA Astrophysics Data System (ADS)

    Zimov, N.; Zimov, S. A.

    2014-12-01

    Modern day ocean circulation is dominated by thermal convection with cold waters subsiding in the Northern Atlantic, filling the ocean interior with cold and heavy water. However, ocean circulation diminished during the last glaciation and consequently the downwelling of the cold. Therefore interior ocean water temperatures must have been affected by other mechanisms which are negligible in the current state. We propose that the submergence of highly saline water from warm seas with high rates of evaporation (like the Red or Mediterranean Sea) was a major factor controlling ocean circulation during the last glaciation. Even today, waters in these poorly connected seas are the heaviest waters in the World ocean (1.029 g/cm3). The second mechanism affecting ocean temperature is the geothermal heat flux. With no heat exchange between the atmosphere and the ocean, geothermal heat flux through the ocean floor is capable of increasing ocean temperature by tens of degrees C over a 100 thousand year glacial cycle. To support these hypotheses we present an ocean box model that describes thermohaline circulation in the World Ocean. According to the model parameters, all water circulation is driven by the water density gradient. Boxes include high-latitude seas, high salinity seas, surface ocean, glaciers, and rift and lateral zones of the ocean interior. External heat sources are radiative forcing, affected by Milankovich cycles, and geothermal heat flux. Additionally this model accounts for the heat produced by organic rain decay. Taking all input parameters close to currently observed values, the model manages to recreate the glacial-interglacial cycles. During the glacial periods only haline circulation takes place, the ocean is strongly stratified, and the interior ocean accumulates heat while high-latitudes accumulate ice. 112,000 years after glaciation starts, water density on the ocean bottom becomes equal to the density of water in high-latitude seas, strong thermal

  20. A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

  1. Simulation of the carbon cycle in the ocean

    SciTech Connect

    Fasham, M.J.R.

    1991-09-16

    A dual carbon-nitrogen biological model of the upper ocean has been developed, which has successfully allowed predictions of fluxes of carbon between atmosphere and the deep ocean to made. Regarding studying the carbon cycle in the ocean, the modelling has highlighted the need for a good understanding of the interactions between the carbon and nitrogen cycles, and also the importance of zooplankton grazing and levels of overwintering biological stocks. Problems have been encountered with the accuracy of prediction of the partial pressure of carbon dioxide in the surface ocean, and the sensitivity of the model to zooplankton parameters, and those parameters which effect overwintering stocks (e.g. mortality parameters). The model has recently been incorporated into a physical General Circulation Model of the Atlantic Ocean. Future work will involve assessing the performance of the biological model in General Circulation Models, and making necessary refinements in order to improve its predictive ability. 1 ref., 1 fig.

  2. Testing Components of New Community Isopycnal Ocean Circulation Model

    SciTech Connect

    Bryan, Kirk

    2008-05-09

    The ocean and atmosphere are both governed by the same physical laws and models of the two media have many similarities. However, there are critical differences that call for special methods to provide the best simulation. One of the most important difference is that the ocean is nearly opaque to radiation in the visible and infra-red part of the spectrum. For this reason water mass properties in the ocean are conserved along trajectories for long distances and for long periods of time. For this reason isopycnal coordinate models would seem to have a distinct advantage in simulating ocean circulation. In such a model the coordinate surfaces are aligned with the natural paths of near adiabatic, density conserving flow in the main thermocline. The difficulty with this approach is at the upper and lower boundaries of the ocean, which in general do not coincide with density surfaces. For this reason hybrid coordinate models were proposed by Bleck and Boudra (1981) in which Cartesian coordinates were used near the ocean surface and isopycnal coordinates were used in the main thermocline. This feature is now part of the HICOM model (Bleck, 2002).

  3. On effective resolution in ocean models

    NASA Astrophysics Data System (ADS)

    Soufflet, Yves; Marchesiello, Patrick; Lemarié, Florian; Jouanno, Julien; Capet, Xavier; Debreu, Laurent; Benshila, Rachid

    2016-02-01

    The increase of model resolution naturally leads to the representation of a wider energy spectrum. As a result, in recent years, the understanding of oceanic submesoscale dynamics has significantly improved. However, dissipation in submesoscale models remains dominated by numerical constraints rather than physical ones. Effective resolution is limited by the numerical dissipation range, which is a function of the model numerical filters (assuming that dispersive numerical modes are efficiently removed). We present a Baroclinic jet test case set in a zonally reentrant channel that provides a controllable test of a model capacity at resolving submesoscale dynamics. We compare simulations from two models, ROMS and NEMO, at different mesh sizes (from 20 to 2 km). Through a spectral decomposition of kinetic energy and its budget terms, we identify the characteristics of numerical dissipation and effective resolution. It shows that numerical dissipation appears in different parts of a model, especially in spatial advection-diffusion schemes for momentum equations (KE dissipation) and tracer equations (APE dissipation) and in the time stepping algorithms. Effective resolution, defined by scale-selective dissipation, is inadequate to qualify traditional ocean models with low-order spatial and temporal filters, even at high grid resolution. High-order methods are better suited to the concept and probably unavoidable. Fourth-order filters are suited only for grid resolutions less than a few kilometers and momentum advection schemes of even higher-order may be justified. The upgrade of time stepping algorithms (from filtered Leapfrog), a cumbersome task in a model, appears critical from our results, not just as a matter of model solution quality but also of computational efficiency (extended stability range of predictor-corrector schemes). Effective resolution is also shaken by the need for non scale-selective barotropic mode filters and requires carefully addressing the

  4. Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

    NASA Astrophysics Data System (ADS)

    Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

    2015-01-01

    Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative

  5. Variability of Ocean Heat Uptake: Reconciling Observations and Models

    SciTech Connect

    AchutaRao, K M; Santer, B D; Gleckler, P J; Taylor, K; Pierce, D; Barnett, T; Wigley, T L

    2005-05-05

    This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our results illustrate that subsampling model data at the locations of available observations increases the variability, reducing the discrepancy between models and observations.

  6. Ocean foam generation and modeling

    NASA Technical Reports Server (NTRS)

    Porter, R. A.; Bechis, K. P.

    1976-01-01

    A laboratory investigation was conducted to determine the physical and microwave properties of ocean foam. Special foam generators were designed and fabricated, using porous glass sheets, known as glass frits, as the principal element. The glass frit was sealed into a water-tight vertical box, a few centimeters from the bottom. Compressed air, applied to the lower chamber, created ocean foam from sea water lying on the frit. Foam heights of 30 cm were readily achieved, with relatively low air pressures. Special photographic techniques and analytical procedures were employed to determine foam bubble size distributions. In addition, the percentage water content of ocean foam was determined with the aid of a particulate sampling procedure. A glass frit foam generator, with pore diameters in the range 70 - 100 micrometers, produced foam with bubble distributions very similar to those found on the surface of natural ocean foam patches.

  7. Incorporating Phaeocystis into a Southern Ocean ecosystem model

    NASA Astrophysics Data System (ADS)

    Wang, Shanlin; Moore, J. Keith

    2011-01-01

    Phaeocystis antarctica is an important phytoplankton species in the Southern Ocean. We incorporated P. antarctica into the biogeochemical elemental cycling ocean model to study Southern Ocean ecosystem dynamics and biogeochemistry. The optimum values of ecological parameters for Phaeocystis were sought through synthesizing laboratory and field observations, and the model output was evaluated with observed chlorophyll a, carbon biomass, and nutrient distributions. Several factors have been proposed to control Southern Ocean ecosystem structure, including light adaptation, iron uptake capability, and loss processes. Optimum simulation results were obtained when P. antarctica had a relatively high α (P-I curve initial slope) value and a higher half-saturation constant for iron uptake than other phytoplankton. Simulation results suggested that P. antarctica had a competitive advantage under low irradiance levels, especially in the Ross Sea and Weddell Sea. However, the distributions of P. antarctica and diatoms were also strongly influenced by iron availability. Although grazing rates had an influence on total biomass, our simulations did not show a strong influence of grazing pressure in the competition between P. antarctica and diatoms. However, limited observations and the relative simplicity of zooplankton in our model suggest further research is needed. Overall, P. antarctica contributed ˜13% of annual primary production and ˜19% of sinking carbon export in the Southern Ocean (>40°S) in our best case simulation. At higher latitudes (>60°S) P. antarctica accounts for ˜23% of annual primary production and ˜30% of sinking carbon export.

  8. Nested ocean models: Work in progress

    NASA Technical Reports Server (NTRS)

    Perkins, A. Louise

    1991-01-01

    The ongoing work of combining three existing software programs into a nested grid oceanography model is detailed. The HYPER domain decomposition program, the SPEM ocean modeling program, and a quasi-geostrophic model written in England are being combined into a general ocean modeling facility. This facility will be used to test the viability and the capability of two-way nested grids in the North Atlantic.

  9. Lagrangian predictability characteristics of an Ocean Model

    NASA Astrophysics Data System (ADS)

    Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia

    2014-11-01

    The Mediterranean Forecasting System (MFS) Ocean Model, provided by INGV, has been chosen as case study to analyze Lagrangian trajectory predictability by means of a dynamical systems approach. To this regard, numerical trajectories are tested against a large amount of Mediterranean drifter data, used as sample of the actual tracer dynamics across the sea. The separation rate of a trajectory pair is measured by computing the Finite-Scale Lyapunov Exponent (FSLE) of first and second kind. An additional kinematic Lagrangian model (KLM), suitably treated to avoid "sweeping"-related problems, has been nested into the MFS in order to recover, in a statistical sense, the velocity field contributions to pair particle dispersion, at mesoscale level, smoothed out by finite resolution effects. Some of the results emerging from this work are: (a) drifter pair dispersion displays Richardson's turbulent diffusion inside the [10-100] km range, while numerical simulations of MFS alone (i.e., without subgrid model) indicate exponential separation; (b) adding the subgrid model, model pair dispersion gets very close to observed data, indicating that KLM is effective in filling the energy "mesoscale gap" present in MFS velocity fields; (c) there exists a threshold size beyond which pair dispersion becomes weakly sensitive to the difference between model and "real" dynamics; (d) the whole methodology here presented can be used to quantify model errors and validate numerical current fields, as far as forecasts of Lagrangian dispersion are concerned.

  10. Multiresolution in CROCO (Coastal and Regional Ocean Community model)

    NASA Astrophysics Data System (ADS)

    Debreu, Laurent; Auclair, Francis; Benshila, Rachid; Capet, Xavier; Dumas, Franck; Julien, Swen; Marchesiello, Patrick

    2016-04-01

    CROCO (Coastal and Regional Ocean Community model [1]) is a new oceanic modeling system built upon ROMS_AGRIF and the non-hydrostatic kernel of SNH, gradually including algorithms from MARS3D (sediments)and HYCOM (vertical coordinates). An important objective of CROCO is to provide the possibility of running truly multiresolution simulations. Our previous work on structured mesh refinement [2] allowed us to run two-way nesting with the following major features: conservation, spatial and temporal refinement, coupling at the barotropic level. In this presentation, we will expose the current developments in CROCO towards multiresolution simulations: connection between neighboring grids at the same level of resolution and load balancing on parallel computers. Results of preliminary experiments will be given both on an idealized test case and on a realistic simulation of the Bay of Biscay with high resolution along the coast. References: [1] : CROCO : http://www.croco-ocean.org [2] : Debreu, L., P. Marchesiello, P. Penven, and G. Cambon, 2012: Two-way nesting in split-explicit ocean models: algorithms, implementation and validation. Ocean Modelling, 49-50, 1-21.

  11. Modeling Mesoscale Eddies in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1999-01-01

    Ocean modeling plays an important role in understanding the current climatic conditions and predicting the future climate change. Modeling the ocean at eddy-permitting and/or eddy resolving resolutions (1/3 degree or higher) has a two-fold objective. One part is to represent the ocean as realistically as possible, because mesoscale eddies have an impact on the large-scale circulation. The second objective is to learn how to represent effects of mesoscale eddies without explicitly resolving them. This is particularly important for climate models which cannot be run at eddy-resolving resolutions because of the computational constraints. At JPL, a 1/6 degree latitude by 1/6 degree longitude with 37 vertical levels Atlantic Ocean model has been developed. The model is based on the Parallel Ocean Program (POP) developed at Los Alamos National Laboratory (LANL). Using the 256-processor Cray T3D, we have conducted a 40-year integration of this Atlantic eddy-resolving ocean model. A regional analysis demonstrate that many observed features associated with the Caribbean Sea eddies can be realistically simulated by this model. Analysis of this Atlantic eddy-resolving ocean model further suggests that these Caribbean Sea eddies are connected with eddies formed outside the Caribbean Sea at the confluence of the North Brazil Current (NBC) and the North Equatorial Countercurrent. The diagram of the model simulated surface current shows that the Caribbean eddies ultimately originate in the NBC retroflection region, traveling more than a year from the North Brazil coast through the Lesser Antilles into the Caribbean Sea and eventually into the Gulf of Mexico. Additional information is contained in the original.

  12. Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George

    2016-01-01

    Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state-of-the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin.

  13. Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments

    PubMed Central

    Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George

    2016-01-01

    Abstract Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state‐of‐the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin.

  14. Utilizing Kernelized Advection Schemes in Ocean Models

    NASA Astrophysics Data System (ADS)

    Zadeh, N.; Balaji, V.

    2008-12-01

    There has been a recent effort in the ocean model community to use a set of generic FORTRAN library routines for advection of scalar tracers in the ocean. In a collaborative project called Hybrid Ocean Model Environement (HOME), vastly different advection schemes (space-differencing schemes for advection equation) become available to modelers in the form of subroutine calls (kernels). In this talk we explore the possibility of utilizing ESMF data structures in wrapping these kernels so that they can be readily used in ESMF gridded components.

  15. The impacts of precipitating cloud radiative effects on ocean surface evaporation, precipitation, and ocean salinity in coupled GCM simulations

    NASA Astrophysics Data System (ADS)

    Li, J.-L. F.; Wang, Yi-Hui; Lee, Tong; Waliser, Duane; Lee, Wei-Liang; Yu, Jia-Yuh; Chen, Yi-Chun; Fetzer, Eric; Hasson, Audrey

    2016-08-01

    The coupled global climate model (GCM) fidelity in representing upper ocean salinity including near sea surface bulk salinity (SSS) is evaluated in this study, with a focus on the Pacific Ocean. The systematic biases in ocean surface evaporation (E) minus precipitation (P) and SSS are found to be fairly similar in the twentieth century simulations of the Coupled Model Intercomparison Phase 3 (CMIP3) and Phase 5 (CMIP5) relative to the observations. One of the potential causes of the CMIP model biases is the missing representation of the radiative effects of precipitating hydrometeors (i.e., snow) in most CMIP models. To examine the radiative effect of cloud snow on SSS, sensitivity experiments with and without such effect are conducted by the National Center for Atmospheric Research-coupled Community Earth System Model (CESM). This study investigates the difference in SSS between sensitivity experiments and its relationship with atmospheric circulation, E - P and air-sea heat fluxes. It is found that the exclusion of the cloud snow radiative effect in CESM produces weaker Pacific trade winds, resulting in enhanced precipitation, reduced evaporation, and a reduction of the upper ocean salinity in the tropical and subtropical Pacific. The latter results in an improved comparison with climatological upper ocean bulk salinity. The introduction of cloud snow also altered the budget terms that maintain the time-mean salinity in the mixed layer.

  16. Visualization and analysis of eddies in a global ocean simulation

    SciTech Connect

    Williams, Sean J; Hecht, Matthew W; Petersen, Mark; Strelitz, Richard; Maltrud, Mathew E; Ahrens, James P; Hlawitschka, Mario; Hamann, Bernd

    2010-10-15

    Eddies at a scale of approximately one hundred kilometers have been shown to be surprisingly important to understanding large-scale transport of heat and nutrients in the ocean. Due to difficulties in observing the ocean directly, the behavior of eddies below the surface is not very well understood. To fill this gap, we employ a high-resolution simulation of the ocean developed at Los Alamos National Laboratory. Using large-scale parallel visualization and analysis tools, we produce three-dimensional images of ocean eddies, and also generate a census of eddy distribution and shape averaged over multiple simulation time steps, resulting in a world map of eddy characteristics. As expected from observational studies, our census reveals a higher concentration of eddies at the mid-latitudes than the equator. Our analysis further shows that mid-latitude eddies are thicker, within a range of 1000-2000m, while equatorial eddies are less than 100m thick.

  17. Models for ecological models: Ocean primary productivity

    USGS Publications Warehouse

    Wikle, Christopher K.; Leeds, William B.; Hooten, Mevin B.

    2016-01-01

    The ocean accounts for more than 70% of planet Earth's surface, and it processes are critically important to marine and terrestrial life.  Ocean ecosystems are strongly dependent on the physical state of the ocean (e.g., transports, mixing, upwelling, runoff, and ice dynamics(.  As an example, consider the Coastal Gulf of Alaska (CGOA) region.

  18. Simulated effect of deep-sea sedimentation and terrestrial weathering on projections of ocean acidification

    NASA Astrophysics Data System (ADS)

    Cao, Long; Zheng, Meidi; Caldeira, Ken

    2016-04-01

    Projections of ocean acidification have often been based on ocean carbon cycle models that do not represent deep-sea sedimentation and terrestrial weathering. Here we use an Earth system model of intermediate complexity to quantify the effect of sedimentation and weathering on projections of ocean acidification under an intensive CO2 emission scenario that releases 5000 Pg C after year 2000. In our simulations, atmospheric CO2 reaches a peak concentration of 2123 ppm near year 2300 with a maximum reduction in surface pH of 0.8. Consideration of deep-sea sedimentation and terrestrial weathering has negligible effect on these peak changes. Only after several millenniums, sedimentation and weathering feedbacks substantially affect projected ocean acidification. Ten thousand years from today, in the constant-alkalinity simulation, surface pH is reduced by ˜0.7 with 95% of the polar oceans undersaturated with respect to calcite, and no ocean has a calcite saturation horizon (CSH) that is deeper than 1000 m. With the consideration of sediment feedback alone, surface pH is reduced by ˜0.5 with 35% of the polar oceans experiencing calcite undersaturation, and 8% global ocean has a CSH deeper than 1000 m. With the addition of weathering feedback, depending on the weathering parameterizations, surface pH is reduced by 0.2-0.4 with no polar oceans experiencing calcite undersaturation, and 30-80% ocean has a CSH that is deeper than 1000 m. Our results indicate that deep-sea sedimentation and terrestrial weathering play an important role in long-term ocean acidification, but have little effect on mitigating ocean acidification in the coming centuries.

  19. Towards petascaling of the NEMO ocean model

    NASA Astrophysics Data System (ADS)

    Donners, J.; Audiffren, N.; Molines, J.-M.

    2012-04-01

    PRACE, the Partnership for Advanced Computing in Europe, offers acces to the largest high-performance computing systems in Europe. These systems follow the trend of increasing numbers of nodes, each with an increasing number of cores. To utilize these computing systems, it is necessary to use a model that is parallellized and has a good scalability. This poster describes different efforts to improve the scalability of the NEMO ocean model. Most importantly, the problem size needs to be chosen adequately: it should contain enough computations to keep thousands of cores busy, but foremostly it has to be scientifically relevant. The global, 1/12degree, NEMO ocean model configuration, developed by the Mercator team, is used for operational ocean forecasting. Therefore, PRACE selected this model for the PRACE Benchmarking suite. However, an increased problem size alone was not enough to efficiently use these petascale systems. Different optimizations were required to reach the necessary performance. Scientifically, the model should simulate one year within a wallclock day. Technically, the application needs to scale up to a minimum number of cores. For example, to utilize the fastest system in Europe, the new Curie system in France, the lower limit is 2048 cores. Scalability can be increased by minimizing the time needed for communication between cores. This has been done in two ways. Firstly, advanced parameters of the MPI-communication library were optimized. The improvement consists in: 1. using RDMA for eager messages (NEMO messages size are below the eager size limit) conjugated with adequate openib flags. 2. tuning for openMPI for collective communication through the btl_coll_tuned_dynamic_rules flag. Overall, the improvement is 33%. Secondly, NEMO uses a tri-polar and staggered grid, which involves a complicated fold across the northpole. Communication along this fold involves collective gather and scatter operations which create a bottleneck at a single core, so

  20. Simulating Fertilization of the Ocean as a Carbon Sequestration Strategy: Effectiveness and Unintended Consequences

    SciTech Connect

    Caldeira, K

    2002-03-20

    The primary objectives of this project are to assess, and improve our understanding of: (1) The effectiveness of various strategies to intentionally store carbon in the ocean through fertilization of the surface ocean with iron and/or macronutrients; and (2) Unanticipated environmental consequences of these ocean fertilization strategies. We propose to use what may be the best global ocean biogeochemical model in the world (PISCES) and apply it to perform the most realistic global-scale simulations of various iron fertilization scenarios. Versions of PISCES are currently used by MPI in Germany and IPSL in France. The model represents diatoms, coccolithophorids, and two classes of zooplankton. This model considers Fey N, P, O{sub 2}, Si, alkalinity, and carbon; for some of these it considers dissolved inorganic and organic, as well as particulate, forms. We would install the PISCES model with a minimum of modification into the LLNL ocean model, and perform an initial suite of simulations of both iron fertilization experiments (e.g., SOFeX) and proposed iron fertilization strategies. Based on the simulated experiments, we will analyze model deficiencies with respect to the observations and use this analysis to improve future versions of the model. The source code for and results from this set of models will be freely distributed, and thus should help groups performing related work elsewhere. This project the most-realistic ocean fertilization simulations yet performed in a global model, with an assessment of and improvement in the reliability of those predictions using results from iron fertilization experiments such as SOFeX. These results will help provide context and guidance for biological observations within the ocean carbon sequestration research program.

  1. Iron Resources and Oceanic Nutrients: Advancement of Global Environment Simulations

    NASA Astrophysics Data System (ADS)

    Debaar, H. J.

    2002-12-01

    simulated. An existing plankton ecosystem model already well predicts limitation by four nutrients (N, P, Si, Fe) of two algal groups (diatoms and nanoplankton) including export and CO2 air/sea exchange. This is being expanded with 3 other groups of algae and DMS(P)pathways. Next this extended ecosystem model is being simplified while maintaining reliable output for export and CO2/DMS gas exchange. This unit will then be put into two existing OBCM's. Inputs of Fe from above and below into the oceans have been modeled. Moreover a simple global Fe cycling model has been verified versus field data and insights. Two different OBCM's with same upper ocean ecosystem/DMS unit and Fe cycling will be verified versus pre-industrial and present conditions. Next climate change scenario's, notably changes in Fe inputs, will be run, with special attention to climatic feedbacks (warming) on the oceanic cycles and fluxes.

  2. Short-term sea ice forecasts with the RASM-ESRL coupled model: A testbed for improving simulations of ocean-ice-atmosphere interactions in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Solomon, A.; Cox, C. J.; Hughes, M.; Intrieri, J. M.; Persson, O. P. G.

    2015-12-01

    The dramatic decrease of Arctic sea-ice has led to a new Arctic sea-ice paradigm and to increased commercial activity in the Arctic Ocean. NOAA's mission to provide accurate and timely sea-ice forecasts, as explicitly outlined in the National Ocean Policy and the U.S. National Strategy for the Arctic Region, needs significant improvement across a range of time scales to improve safety for human activity. Unfortunately, the sea-ice evolution in the new Arctic involves the interaction of numerous physical processes in the atmosphere, ice, and ocean, some of which are not yet understood. These include atmospheric forcing of sea-ice movement through stress and stress deformation; atmospheric forcing of sea-ice melt and formation through energy fluxes; and ocean forcing of the atmosphere through new regions of seasonal heat release. Many of these interactions involve emerging complex processes that first need to be understood and then incorporated into forecast models in order to realize the goal of useful sea-ice forecasting. The underlying hypothesis for this study is that errors in simulations of "fast" atmospheric processes significantly impact the forecast of seasonal sea-ice retreat in summer and its advance in autumn in the marginal ice zone (MIZ). We therefore focus on short-term (0-20 day) ice-floe movement, the freeze-up and melt-back processes in the MIZ, and the role of storms in modulating stress and heat fluxes. This study uses a coupled ocean-atmosphere-seaice forecast model as a testbed to investigate; whether ocean-sea ice-atmosphere coupling improves forecasts on subseasonal time scales, where systematic biases develop due to inadequate parameterizations (focusing on mixed-phase clouds and surface fluxes), how increased atmospheric resolution of synoptic features improves the forecasts, and how initialization of sea ice area and thickness and snow depth impacts the skill of the forecasts. Simulations are validated with measurements at pan-Arctic land

  3. Modelling Ocean Surface Waves in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, Lucia; Aksenov, Yevgeny; Coward, Andrew; Bertino, Laurent; Williams, Timothy; Nurser, George A. J.

    2015-04-01

    In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with up to a 39% widening in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to reflection and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to external stresses. This process generates a distribution of floe sizes and impacts the dynamics of sea ice by the means of combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 degree resolution with a wave-ice interaction module described above. The module introduces two new diagnostics previously unavailable in GCM's: surface wave spectra in sea ice covered areas, and floe size distribution due to wave-induced fragmentation. We discuss the impact of these processes on the ocean and sea ice state, including ocean circulation, mixing, stratification and the role of the MIZ in the ocean variability. The model predictions for the floe sizes in the summer Arctic Ocean range from 60 m in the inner MIZ to a few tens of meters near the open ocean, which agrees with estimates from the satellites. The extent of the MIZ throughout the year is also in

  4. A regional ocean model for the Southwest Pacific Ocean region to assess the risk of storms

    NASA Astrophysics Data System (ADS)

    Natoo, N.; Paul, A.; Hadfield, M.; Jendersie, S.; Bornman, J.; de Lange, W.; Ye, W.; Schulz, M.

    2012-04-01

    New Zealand's coasts are not only affected by mid-latitude storms, but infrequently also by storms that originate from the tropics. Projections for the southern hemisphere's southwest Pacific island countries for the 21st century show a poleward shift of the mid-latitude storm tracks, which consequently might result in changes in wind, precipitation and temperature patterns. Furthermore, an increase in frequency of intense storms is expected for the New Zealand region, which will very likely increase the risk of storm surges and flooding of coastal and low-lying regions. We employ the Regional Ocean Modeling System (ROMS) to assess the changes in the storm climate of the New Zealand region. The model set-up uses a resolution of ~50 km for the Southwest Pacific Ocean "parent domain" and ~10 km for the New Zealand "child domain", to well represent the major eddies that influence the climate of North Island. With the aim to later utilize this nested ocean model set-up as part of a coupled ocean-atmosphere modelling system for the Southwest Pacific Ocean region, results for the 20th century will be presented. The simulated circulation is shown to be largely consistent with the observed regional oceanography.

  5. Modelling salt finger formation using the Imperial College Ocean Model

    NASA Astrophysics Data System (ADS)

    MacTavish, F. P.; Cotter, C. J.; Piggott, M. D.

    2009-04-01

    We present numerical simulations of salt finger formation produced using the Imperial College Ocean Model (ICOM) which is a finite element model using adaptive meshing. Our aim is to validate the model against published data and to develop the capability to simulate salt finger formation using adaptive meshes. Salt fingering is a form of double-diffusion which occurs because heat diffuses more quickly than salt. When an area of warm, salty water overlies an area of colder, fresher water, an initial perturbation can lead to some of the water from the lower layer moving into the top layer. Its temperature then increases more quickly than its salinity, so that the water is less dense than its surroundings and it will rise up more. This process repeats to form salt fingers, with salt fingers also forming in the downward direction. Salt fingers play a role in oceanic mixing, in particular they are responsible for maintaining thermohaline staircases such as the C-SALT staircase which have been observed extensively, particularly in the tropics. The study of salt fingers could therefore improve our understanding of processes in the ocean, and inform the design of subgrid parameterisations in general circulation models. We used the salt finger formation test case of Oezgoekmen et al (1998) in order to validate ICOM. The formation of salt fingers is modelled by solving the Navier-Stokes equations for a two-dimensional rectangular area of Boussinesq fluid, beginning with two layers of water, the top warm and salty and the bottom cold and fresh, with parameters chosen to match the test case of Oezgoekmen et al (1998). The positions of the interfaces between the fingering layer and the mixed layers as well as the finger growth rate and the kinetic energy are plotted against time. The results are compared with those of Oezgoekmen et al (1998). We present results from structured meshes and preliminary results using adaptive meshing.

  6. Monte Carlo code for high spatial resolution ocean color simulations.

    PubMed

    D'Alimonte, Davide; Zibordi, Giuseppe; Kajiyama, Tamito; Cunha, José C

    2010-09-10

    A Monte Carlo code for ocean color simulations has been developed to model in-water radiometric fields of downward and upward irradiance (E(d) and E(u)), and upwelling radiance (L(u)) in a two-dimensional domain with a high spatial resolution. The efficiency of the code has been optimized by applying state-of-the-art computing solutions, while the accuracy of simulation results has been quantified through benchmark with the widely used Hydrolight code for various values of seawater inherent optical properties and different illumination conditions. Considering a seawater single scattering albedo of 0.9, as well as surface waves of 5 m width and 0.5 m height, the study has shown that the number of photons required to quantify uncertainties induced by wave focusing effects on E(d), E(u), and L(u) data products is of the order of 10(6), 10(9), and 10(10), respectively. On this basis, the effects of sea-surface geometries on radiometric quantities have been investigated for different surface gravity waves. Data products from simulated radiometric profiles have finally been analyzed as a function of the deployment speed and sampling frequency of current free-fall systems in view of providing recommendations to improve measurement protocols.

  7. Monte Carlo code for high spatial resolution ocean color simulations.

    PubMed

    D'Alimonte, Davide; Zibordi, Giuseppe; Kajiyama, Tamito; Cunha, José C

    2010-09-10

    A Monte Carlo code for ocean color simulations has been developed to model in-water radiometric fields of downward and upward irradiance (E(d) and E(u)), and upwelling radiance (L(u)) in a two-dimensional domain with a high spatial resolution. The efficiency of the code has been optimized by applying state-of-the-art computing solutions, while the accuracy of simulation results has been quantified through benchmark with the widely used Hydrolight code for various values of seawater inherent optical properties and different illumination conditions. Considering a seawater single scattering albedo of 0.9, as well as surface waves of 5 m width and 0.5 m height, the study has shown that the number of photons required to quantify uncertainties induced by wave focusing effects on E(d), E(u), and L(u) data products is of the order of 10(6), 10(9), and 10(10), respectively. On this basis, the effects of sea-surface geometries on radiometric quantities have been investigated for different surface gravity waves. Data products from simulated radiometric profiles have finally been analyzed as a function of the deployment speed and sampling frequency of current free-fall systems in view of providing recommendations to improve measurement protocols. PMID:20830183

  8. Scientific development of a massively parallel ocean climate model. Final report

    SciTech Connect

    Semtner, A.J.; Chervin, R.M.

    1996-09-01

    Over the last three years, very significant advances have been made in refining the grid resolution of ocean models and in improving the physical and numerical treatments of ocean hydrodynamics. Some of these advances have occurred as a result of the successful transition of ocean models onto massively parallel computers, which has been led by Los Alamos investigators. Major progress has been made in simulating global ocean circulation and in understanding various ocean climatic aspects such as the effect of wind driving on heat and freshwater transports. These steps have demonstrated the capability to conduct realistic decadal to century ocean integrations at high resolution on massively parallel computers.

  9. Medicanes in an ocean-atmosphere coupled regional climate model

    NASA Astrophysics Data System (ADS)

    Akhtar, N.; Brauch, J.; Dobler, A.; Béranger, K.; Ahrens, B.

    2014-03-01

    So-called medicanes (Mediterranean hurricanes) are meso-scale, marine, and warm-core Mediterranean cyclones that exhibit some similarities to tropical cyclones. The strong cyclonic winds associated with medicanes threaten the highly populated coastal areas around the Mediterranean basin. To reduce the risk of casualties and overall negative impacts, it is important to improve the understanding of medicanes with the use of numerical models. In this study, we employ an atmospheric limited-area model (COSMO-CLM) coupled with a one-dimensional ocean model (1-D NEMO-MED12) to simulate medicanes. The aim of this study is to assess the robustness of the coupled model in simulating these extreme events. For this purpose, 11 historical medicane events are simulated using the atmosphere-only model, COSMO-CLM, and coupled model, with different setups (horizontal atmospheric grid-spacings of 0.44°, 0.22°, and 0.08°; with/without spectral nudging, and an ocean grid-spacing of 1/12°). The results show that at high-resolution, the coupled model is able to not only simulate most of medicane events but also improve the track length, core temperature, and wind speed of simulated medicanes compared to the atmosphere-only simulations. The results suggest that the coupled model is more proficient for systemic and detailed studies of historical medicane events, and that this model can be an effective tool for future projections.

  10. Medicanes in an ocean-atmosphere coupled regional climate model

    NASA Astrophysics Data System (ADS)

    Akhtar, N.; Brauch, J.; Dobler, A.; Béranger, K.; Ahrens, B.

    2014-08-01

    So-called medicanes (Mediterranean hurricanes) are meso-scale, marine, and warm-core Mediterranean cyclones that exhibit some similarities to tropical cyclones. The strong cyclonic winds associated with medicanes threaten the highly populated coastal areas around the Mediterranean basin. To reduce the risk of casualties and overall negative impacts, it is important to improve the understanding of medicanes with the use of numerical models. In this study, we employ an atmospheric limited-area model (COSMO-CLM) coupled with a one-dimensional ocean model (1-D NEMO-MED12) to simulate medicanes. The aim of this study is to assess the robustness of the coupled model in simulating these extreme events. For this purpose, 11 historical medicane events are simulated using the atmosphere-only model, COSMO-CLM, and coupled model, with different setups (horizontal atmospheric grid spacings of 0.44, 0.22, and 0.08°; with/without spectral nudging, and an ocean grid spacing of 1/12°). The results show that at high resolution, the coupled model is able to not only simulate most of medicane events but also improve the track length, core temperature, and wind speed of simulated medicanes compared to the atmosphere-only simulations. The results suggest that the coupled model is more proficient for systemic and detailed studies of historical medicane events, and that this model can be an effective tool for future projections.

  11. A one ocean model of biodiversity

    NASA Astrophysics Data System (ADS)

    O'Dor, Ronald K.; Fennel, Katja; Berghe, Edward Vanden

    2009-09-01

    The history of life is written in the ocean, and the history of the ocean is written in DNA. Geologists have shown us that hundreds of millions of years of ocean history can be revealed from records of a single phylum in cores of mud from abyssal plains. We are now accumulating genetic tools to unravel the relationships of hundreds of phyla to track this history back billions of years. The technologies demonstrated by the Census of Marine Life (CoML) mean that the ocean is no longer opaque or unknowable. The secrets of the largest component of the biosphere are knowable. The cost of understanding the history of ocean life is not cheap, but it is also not prohibitive. A transparent, open ocean is available for us to use to understand ourselves. This article develops a model of biodiversity equilibration in a single, physically static ocean as a step towards biodiversity in physically complex real oceans. It attempts to be quantitative and to simultaneously account for biodiversity patterns from bacteria to whales focusing on emergent properties rather than details. Biodiversity reflects long-term survival of DNA sequences, stabilizing "ecosystem services" despite environmental change. In the ocean, mechanisms for ensuring survival range from prokaryotes maintaining low concentrations of replicable DNA throughout the ocean volume, anticipating local change, to animals whose mobility increases with mass to avoid local change through movement. Whales can reach any point in the ocean in weeks, but prokaryotes can only diffuse. The high metabolic costs of mobility are offset by the dramatically lower number of DNA replicates required to ensure survival. Reproduction rates probably scale more or less inversely with body mass. Bacteria respond in a week, plankton in a year, whales in a century. We generally lack coherent theories to explain the origins of animals (metazoans) and the contributions of biodiversity to ecosystems. The One Ocean Model suggests that mobile

  12. (CO sub 2 uptake in an Ocean Circulation Model)

    SciTech Connect

    Siegenthaler, U.C.

    1990-11-06

    The traveler collaborated with Drs. J. L. Sarmiento and J. C. Orr of the Program in Atmospheric Sciences at Princeton University to finish the article A Perturbation Simulation of CO{sub 2} Uptake in an Ocean Circulation Model,'' which has been submitted to the Journal of Geophysical Research for publication. With F. Joos, a graduate student from the University of Bern, the traveler started writing a journal article describing a box model of the global carbon cycle that is an extension of the one-dimensional box-diffusion model. The traveler further collaborated with F. Joos and Dr. J. L. Sarmiento on modeling the potential enhancement of oceanic CO{sub 2} uptake by fertilizing the southern ocean with iron. A letter describing the results is currently being written for the journal Nature.

  13. The development of a coupled ice-ocean model for forecasting ice conditions in the Arctic

    NASA Astrophysics Data System (ADS)

    Riedlinger, Shelley H.; Preller, Ruth H.

    1991-09-01

    A coupled ice-ocean model has been developed to investigate how a better simulation of ice-ocean interaction can improve sea ice forecasting capabilities. The coupling of the ice and ocean results in improved temporal variability of ocean circulation and heat and salt exchange between ice and ocean. The U.S. Navy's Polar Ice Prediction System is coupled to a diagnostic version of the Bryan-Cox three-dimensional ocean circulation model. A horizontal grid spacing of 127 km was used in the coupled model with 17 vertical levels from the surface to the ocean bottom. Atmospheric data from the Naval Operational Global Atmospheric Prediction System (NOGAPS) for 1986 were used to force the model. The ice-ocean model simulation yielded realistic ice thickness distributions, ice drifts, and ocean currents. The model predicted accurate seasonal trends in ice growth and decay. Excess ice is often grown in the Greenland and Barents seas in fall and winter. This is due, in part, to the model's grid resolution which does not accurately resolve narrow currents, such as the West Spitsbergen Current. A sensitivity study of the heat transfer coefficients used in the ice model showed that the ice edge could be improved by using different coefficient values for thick ice, thin ice, and open water. Other sensitivity studies examined the effect of removing the "distorted" physics frequently used in the Bryan-Cox ocean circulation model and the effect of the vertical eddy momentum coefficient on the surface ocean circulation. An additional simulation was made using 1989 NOGAPS forcing to examine what type of variability could occur when using different years of NOGAPS forcing in the diagnostic ocean model. Significant differences occurred between the 1989 and 1986 ice thickness distributions as well as the oceanic heat fluxes. These differences show that the forecast system, which presently uses an ocean "climatology," can benefit from the variability allowed by the diagnostic ocean model.

  14. A 1/16° eddying simulation of the global NEMO sea-ice-ocean system

    NASA Astrophysics Data System (ADS)

    Iovino, Doroteaciro; Masina, Simona; Storto, Andrea; Cipollone, Andrea; Stepanov, Vladimir N.

    2016-08-01

    Analysis of a global eddy-resolving simulation using the NEMO general circulation model is presented. The model has 1/16° horizontal spacing at the Equator, employs two displaced poles in the Northern Hemisphere, and uses 98 vertical levels. The simulation was spun up from rest and integrated for 11 model years, using ERA-Interim reanalysis as surface forcing. Primary intent of this hindcast is to test how the model represents upper ocean characteristics and sea ice properties. Analysis of the zonal averaged temperature and salinity, and the mixed layer depth indicate that the model average state is in good agreement with observed fields and that the model successfully represents the variability in the upper ocean and at intermediate depths. Comparisons against observational estimates of mass transports through key straits indicate that most aspects of the model circulation are realistic. As expected, the simulation exhibits turbulent behaviour and the spatial distribution of the sea surface height (SSH) variability from the model is close to the observed pattern. The distribution and volume of the sea ice are, to a large extent, comparable to observed values. Compared with a corresponding eddy-permitting configuration, the performance of the model is significantly improved: reduced temperature and salinity biases, in particular at intermediate depths, improved mass and heat transports, better representation of fluxes through narrow and shallow straits, and increased global-mean eddy kinetic energy (by ˜ 40 %). However, relatively minor weaknesses still exist such as a lower than observed magnitude of the SSH variability. We conclude that the model output is suitable for broader analysis to better understand upper ocean dynamics and ocean variability at global scales. This simulation represents a major step forward in the global ocean modelling at the Euro-Mediterranean Centre on Climate Change and constitutes the groundwork for future applications to short

  15. A three-dimensional numerical simulation of Typhoon Holly in the northwestern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Hong, Chul-Hoon; Yoon, Jong-Hwan

    2003-08-01

    A three-dimensional primitive equation model (the Princeton Ocean Model, often called POM) has been implemented for simulating Typhoon Holly generated in the tropical Pacific Ocean. This is the first time that a study of this type, previously used mostly for coastal, regional simulations, has been implemented for the northwestern Pacific Ocean, from 24°N to 52°N, including the East China Sea, the Yellow Sea, and the East (Japan) Sea. In the open ocean the model circulation, sea surface elevation, and temperature distribution with the passage of Holly are described; the results are in part compared with observation in the Korea (Tsushima) Strait. The model reproduces well several prominent features obtained in the observation such as a rapid increase of temperature in the Korea Strait during the passage of Typhoon Holly, in August 1984, and reasonably explains how they happened. Around the vicinity of the typhoon center, the model temperature field successfully presents "sea surface cooling" in the open ocean, having been frequently observed in the past. The model also suggests that a coastal jet around the Korea Strait and a cyclonic eddy field behind Holly in the East China Sea play an important role in the oceanic conditions although they have not yet been identified by observations.

  16. The Biogeochemical Influences of Dust Deposition in a Global Ocean Ecosystem Simulation

    NASA Astrophysics Data System (ADS)

    Moore, J. K.

    2003-12-01

    Global ocean simulations of ocean biogeochemistry are driven with model estimates of atmospheric dust transport and deposition as a key source of iron to the upper ocean. The coupled Biogeochemistry/Ecosystem/Circulation (BEC) model includes explicit phytoplankton functional groups that compete for available light and several potentially growth-limiting nutrients - nitrogen, phosphorus, silicon, and iron. Diatoms, coccolithophores, picoplankton, and nitrogen fixing diazotrophs are represented in the model. These different classes of phytoplankton experience differential grazing pressure and other loss terms in the model. Global scale patterns in nutrient limitation, primary production, carbon export out of surface waters, and nitrogen fixation are all sensitive to variations in atmospheric dust deposition. Dust deposition also significantly influences the competition between phytoplankton groups (diatom vs. non-diatoms, n-fixers vs. picoplankton). The potential impacts of climate driven variations in dust deposition to the oceans will be discussed.

  17. A 1/16° eddying simulation of the global ocean/sea ice system

    NASA Astrophysics Data System (ADS)

    Iovino, Dorotea; Masina, Simona; Storto, Andrea; Cipollone, Andrea; Stepanov, Vladimir N.

    2016-04-01

    Analysis of a global eddy-resolving simulation using the NEMO general circulation model is presented. The model has 1/16° horizontal spacing at the equator, employs two displaced poles in the Northern Hemisphere, and uses 98 vertical levels. The simulation was spun up from rest and integrated for 11 model years, using ERA-Interim reanalysis as surface forcing. Primary intent of this hindcast is to test how the model represents upper ocean characteristics and sea ice properties. Numerical results show that, overall, the general circulation is well reproduced, with realistic values for overturning mass and heat transports. Analysis of the zonal averaged temperature and salinity, and the mixed layer depth indicate that the model average state is in good agreement with observed fields. Comparisons against observational estimates of mass transports through key straits indicate that most aspects of the model circulation are realistic. As expected, the simulation exhibits turbulent behaviour. The spatial distribution of the sea surface height variability from the model is close to the observed pattern. Despite the increase in resolution, the variability amplitude is still weak, in particular in the Southern Ocean. The distribution and volume of the sea ice are, to a large extent, comparable to observed values. Compared with a corresponding coarse-resolution configuration, the performance of the model is significantly improved, although relatively minor weaknesses still exist. We conclude that the model output is suitable for broader analysis to better understand upper ocean dynamics and ocean variability at global scales. This simulation represents a major step forward in the CMCC global ocean modelling, and constitutes the groundwork for future applications to short-range ocean forecasting.

  18. Monte Carlo and discrete-ordinate simulations of irradiances in the coupled atmosphere-ocean system.

    PubMed

    Gjerstad, Karl Idar; Stamnes, Jakob J; Hamre, Børge; Lotsberg, Jon K; Yan, Banghua; Stamnes, Knut

    2003-05-20

    We compare Monte Carlo (MC) and discrete-ordinate radiative-transfer (DISORT) simulations of irradiances in a one-dimensional coupled atmosphere-ocean (CAO) system consisting of horizontal plane-parallel layers. The two models have precisely the same physical basis, including coupling between the atmosphere and the ocean, and we use precisely the same atmospheric and oceanic input parameters for both codes. For a plane atmosphere-ocean interface we find agreement between irradiances obtained with the two codes to within 1%, both in the atmosphere and the ocean. Our tests cover case 1 water, scattering by density fluctuations both in the atmosphere and in the ocean, and scattering by particulate matter represented by a one-parameter Henyey-Greenstein (HG) scattering phase function. The CAO-MC code has an advantage over the CAO-DISORT code in that it can handle surface waves on the atmosphere-ocean interface, but the CAO-DISORT code is computationally much faster. Therefore we use CAO-MC simulations to study the influence of ocean surface waves and propose a way to correct the results of the CAO-DISORT code so as to obtain fast and accurate underwater irradiances in the presence of surface waves.

  19. Characterizing Ocean Turbulence from Argo, Acoustic Doppler, and Simulation Data

    NASA Astrophysics Data System (ADS)

    McCaffrey, Katherine

    Turbulence is inherently chaotic and unsteady, so observing it and modeling it are no easy tasks. The ocean's sheer size makes it even more difficult to observe, and its unpredictable and ever-changing forcings introduce additional complexities. Turbulence in the oceans ranges from basin scale to the scale of the molecular viscosity. The method of energy transfer between scales is, however, an area of active research, so observations of the ocean at all scales are crucial to understanding the basic dynamics of its motions. In this collection of work, I use a variety of datasets to characterize a wide range of scales of turbulence, including observations from multiple instruments and from models with different governing equations. I analyzed the largest scales of the turbulent range using the global salinity data of the Argo profiling float network. Taking advantage of the scattered and discontinuous nature of this dataset, the second-order structure function was calculated down to 2000m depth, and shown to be useful for predicting spectral slopes. Results showed structure function slopes of 2/3 at small scales, and 0 at large scales, which corresponds with spectral slopes of -5/3 at small scales, and -1 at large scales. Using acoustic Doppler velocity measurements, I characterized the meter- to kilometer-scale turbulence at a potential tidal energy site in the Puget Sound, WA. Acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter (ADV) observations provided the data for an analysis that includes coherence, anisotropy, and intermittency. In order to more simply describe these features, a parameterization was done with four turbulence metrics, and the anisotropy magnitude, introduced here, was shown to most closely capture the coherent events. Then, using both the NREL TurbSim stochastic turbulence generator and the NCAR large-eddy simulation (LES) model, I calculated turbulence statistics to validate the accuracy of these methods in reproducing

  20. Parallel Computation of the Regional Ocean Modeling System (ROMS)

    SciTech Connect

    Wang, P; Song, Y T; Chao, Y; Zhang, H

    2005-04-05

    The Regional Ocean Modeling System (ROMS) is a regional ocean general circulation modeling system solving the free surface, hydrostatic, primitive equations over varying topography. It is free software distributed world-wide for studying both complex coastal ocean problems and the basin-to-global scale ocean circulation. The original ROMS code could only be run on shared-memory systems. With the increasing need to simulate larger model domains with finer resolutions and on a variety of computer platforms, there is a need in the ocean-modeling community to have a ROMS code that can be run on any parallel computer ranging from 10 to hundreds of processors. Recently, we have explored parallelization for ROMS using the MPI programming model. In this paper, an efficient parallelization strategy for such a large-scale scientific software package, based on an existing shared-memory computing model, is presented. In addition, scientific applications and data-performance issues on a couple of SGI systems, including Columbia, the world's third-fastest supercomputer, are discussed.

  1. Resolving the upper-ocean warm layer improves the simulation of the Madden-Julian oscillation

    NASA Astrophysics Data System (ADS)

    Tseng, Wan-Ling; Tsuang, Ben-Jei; Keenlyside, Noel S.; Hsu, Huang-Hsiung; Tu, Chia-Ying

    2015-03-01

    Here we show that coupling a high-resolution one-column ocean model to an atmospheric general circulation model dramatically improves simulation of the Madden-Julian oscillation (MJO) to have realistic strength, period, and propagation speed. The mechanism for the simulated MJO involves both frictional wave-convective conditional instability of the second kind (Frictional wave-CISK) and air-sea convective intraseasonal interaction (ASCII). In particular, better resolving the fine structure of upper ocean temperature, especially the warm layer, produces more vigorous atmosphere-ocean interaction and strengthens intraseasonal variations in both SST and atmospheric circulation. This helps organize and strengthen deep convection, inducing a stronger Kelvin-wave like perturbation and frictional near-surface convergence to the east. In addition, the warmer SST ahead of the MJO also acts to destabilize the boundary layer and enhance frictional convergence. These lead to a more realistic eastward-propagating MJO. A suite of sensitivity experiments were performed to show the robustness of the mechanisms and to demonstrate: (1) that mean state differences are not the main contributors to the improved simulation of our coupled model; (2) the role of SST variability in enhancing frictional convergence and intraseasonal variations in precipitation, and (3) that the simulation is significantly degraded when the first ocean model layer is thicker than 10 m. Our coupled model results are consistent with observations and demonstrate a simple but effective means to significantly improve MJO simulation and potentially also forecasts.

  2. Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of atmospheric dispersion model with improved deposition scheme and oceanic dispersion model

    NASA Astrophysics Data System (ADS)

    Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

    2014-06-01

    Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Dai-ichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate a detailed time trend of atmospheric releases during the accident by combining environmental monitoring data with atmospheric model simulations from WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information), and simulations from the oceanic dispersion model SEA-GEARN-FDM, both developed by the authors. A sophisticated deposition scheme, which deals with dry and fogwater depositions, cloud condensation nuclei (CCN) activation and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The fallout to the ocean surface calculated by WSPEEDI-II was used as input data for the SEA-GEARN-FDM calculations. Reverse and inverse source-term estimation methods based on coupling the simulations from both models was adopted using air dose rates and concentrations, and sea surface concentrations. The results revealed that the major releases of radionuclides due to FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, the morning of 13 March after the venting event at Unit 3, midnight of 14 March when the SRV (Safely Relief Valve) at Unit 2 was opened three times, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of

  3. Numerical modelling of floating debris in the world's oceans.

    PubMed

    Lebreton, L C-M; Greer, S D; Borrero, J C

    2012-03-01

    A global ocean circulation model is coupled to a Lagrangian particle tracking model to simulate 30 years of input, transport and accumulation of floating debris in the world ocean. Using both terrestrial and maritime inputs, the modelling results clearly show the formation of five accumulation zones in the subtropical latitudes of the major ocean basins. The relative size and concentration of each clearly illustrate the dominance of the accumulation zones in the northern hemisphere, while smaller seas surrounded by densely populated areas are also shown to have a high concentration of floating debris. We also determine the relative contribution of different source regions to the total amount of material in a particular accumulation zone. This study provides a framework for describing the transport, distribution and accumulation of floating marine debris and can be continuously updated and adapted to assess scenarios reflecting changes in the production and disposal of plastic worldwide.

  4. A perfectly matched layer for fluid-solid problems: Application to ocean-acoustics simulations with solid ocean bottoms.

    PubMed

    Xie, Zhinan; Matzen, René; Cristini, Paul; Komatitsch, Dimitri; Martin, Roland

    2016-07-01

    A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range-dependent and depth-dependent wave speed and density, as well as steep ocean floor topography. For truncation of the infinite domain, to efficiently absorb outgoing waves, a fluid-solid complex-frequency-shifted unsplit perfectly matched layer is introduced based on the complex coordinate stretching technique. The complex stretching is rigorously taken into account in the derivation of the fluid-solid matching condition inside the absorbing layer, which has never been done before in the time domain. Two implementations are designed: a convolutional formulation and an auxiliary differential equation formulation because the latter allows for implementation of high-order time schemes, leading to reduced numerical dispersion and dissipation, a topic of importance, in particular, in long-range ocean acoustics simulations. The method is validated for a two dimensional fluid-solid Pekeris waveguide and for a three dimensional seamount model, which shows that the technique is accurate and numerically long-time stable. Compared with widely used paraxial absorbing boundary conditions, the perfectly matched layer is significantly more efficient at absorbing both body waves and interface waves.

  5. A perfectly matched layer for fluid-solid problems: Application to ocean-acoustics simulations with solid ocean bottoms.

    PubMed

    Xie, Zhinan; Matzen, René; Cristini, Paul; Komatitsch, Dimitri; Martin, Roland

    2016-07-01

    A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range-dependent and depth-dependent wave speed and density, as well as steep ocean floor topography. For truncation of the infinite domain, to efficiently absorb outgoing waves, a fluid-solid complex-frequency-shifted unsplit perfectly matched layer is introduced based on the complex coordinate stretching technique. The complex stretching is rigorously taken into account in the derivation of the fluid-solid matching condition inside the absorbing layer, which has never been done before in the time domain. Two implementations are designed: a convolutional formulation and an auxiliary differential equation formulation because the latter allows for implementation of high-order time schemes, leading to reduced numerical dispersion and dissipation, a topic of importance, in particular, in long-range ocean acoustics simulations. The method is validated for a two dimensional fluid-solid Pekeris waveguide and for a three dimensional seamount model, which shows that the technique is accurate and numerically long-time stable. Compared with widely used paraxial absorbing boundary conditions, the perfectly matched layer is significantly more efficient at absorbing both body waves and interface waves. PMID:27475142

  6. A Coupled Atmosphere-Ocean-Wave Modeling System

    NASA Astrophysics Data System (ADS)

    Allard, R. A.; Smith, T.; Rogers, W. E.; Jensen, T. G.; Chu, P.; Campbell, T. J.

    2012-12-01

    A growing interest in the impacts that large and small scale ocean and atmospheric events (El Niño, hurricanes, etc.) have on weather forecasting has led to the coupling of atmospheric, ocean circulation and ocean wave models. The Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS™ ) consists of the Navy's atmospheric model coupled to the Navy Coastal Ocean Model (NCOM) and the wave models SWAN (Simulating WAves Nearshore) and WAVEWATCH III (WW3™). In a fully coupled mode, COAMPS, NCOM, and SWAN (or WW3) may be integrated concurrently so that currents and water levels, wave-induced stress, bottom drag, Stokes drift current, precipitation, and surface fluxes of heat, moisture, and momentum are exchanged across the air-wave-sea interface. This coupling is facilitated through the Earth System Modeling Framework (ESMF). The ESMF version of COAMPS is being transitioned to operational production centers at the Naval Oceanographic Office and the Fleet Numerical Meteorology and Oceanography Center. Highlights from validation studies for the Florida Straits, Hurricane Ivan and the Adriatic Sea will be presented. COAMPS® is a registered trademark of the Naval Research Laboratory.

  7. Modeling Europa's Ice-Ocean Interface

    NASA Astrophysics Data System (ADS)

    Elsenousy, A.; Vance, S.; Bills, B. G.

    2014-12-01

    This work focuses on modeling the ice-ocean interface on Jupiter's Moon (Europa); mainly from the standpoint of heat and salt transfer relationship with emphasis on the basal ice growth rate and its implications to Europa's tidal response. Modeling the heat and salt flux at Europa's ice/ocean interface is necessary to understand the dynamics of Europa's ocean and its interaction with the upper ice shell as well as the history of active turbulence at this area. To achieve this goal, we used McPhee et al., 2008 parameterizations on Earth's ice/ocean interface that was developed to meet Europa's ocean dynamics. We varied one parameter at a time to test its influence on both; "h" the basal ice growth rate and on "R" the double diffusion tendency strength. The double diffusion tendency "R" was calculated as the ratio between the interface heat exchange coefficient αh to the interface salt exchange coefficient αs. Our preliminary results showed a strong double diffusion tendency R ~200 at Europa's ice-ocean interface for plausible changes in the heat flux due to onset or elimination of a hydrothermal activity, suggesting supercooling and a strong tendency for forming frazil ice.

  8. Modelling the turbulence of a freezing Martian ocean

    NASA Astrophysics Data System (ADS)

    Kiss, Gabor; Leitner, Johannes; Firneis, Maria

    2015-04-01

    We modified the General Ocean Turbulence Model (GOTM) to fit simulations investigating the hypotheses of early oceans or seas on planet Mars. Observed morphologies like paleoshorelines (Parker et al. 1987, Carr et al. 2003) and buried craters (Boyce et al. 2005, Head et al. 2002) indicate possible processes which could have been caused by large standing open bodies of water in the northern hemisphere of Mars. These structures, as well as altitude measurements of delta networks (diAchille et al. 2010) proclaim various sizes of oceans and or seas. Evidence for their existence whether one or more at different times in the early history of the planet, or the evolution and fate of an ocean are still elusive. The smoothness of the northern plains is debated, to be the result of volcanic effluents followed by the deposition of the sedimental load called the Vastias Borealis Formation (VBF). Detailed observations of crater depths (d/D ratios) in the northern hemisphere have shown further arguments for a northern ocean. The prevailing opinion is a short life of a liquid ocean, and a rather fast freezing period leading to sublimation under a thin atmosphere. McKay et al. (1990) have shown that liquid habitats could be maintained under an ice sheet for up to several hundred million years, if melt/freshwater and or volcanic activity was supported. Using the atmospheric data of the GCM (Forget et al. 1999) as input parameters for temperature and wind velocities, we simulate an ocean exposed from mild to freezing temperatures of water at different atmospheric pressures. We are investigating the detailed effects of turbulence on the ocean or sea floors, as well as the effects of salinity and freshwater inflow on the Martian soil. Apart from the driving forces like fed of outflow channels and or rivers and wind, the duration of liquid water is a key question on the redistribution of sediments and the formation of coastal structures.

  9. North Pacific Mesoscale Coupled Air-Ocean Simulations Compared with Observations

    SciTech Connect

    Koracin, Darko; Cerovecki, Ivana; Vellore, Ramesh; Mejia, John; Hatchett, Benjamin; McCord, Travis; McLean, Julie; Dorman, Clive

    2013-04-11

    Executive summary The main objective of the study was to investigate atmospheric and ocean interaction processes in the western Pacific and, in particular, effects of significant ocean heat loss in the Kuroshio and Kuroshio Extension regions on the lower and upper atmosphere. It is yet to be determined how significant are these processes are on climate scales. The understanding of these processes led us also to development of the methodology of coupling the Weather and Research Forecasting model with the Parallel Ocean Program model for western Pacific regional weather and climate simulations. We tested NCAR-developed research software Coupler 7 for coupling of the WRF and POP models and assessed its usability for regional-scale applications. We completed test simulations using the Coupler 7 framework, but implemented a standard WRF model code with options for both one- and two-way mode coupling. This type of coupling will allow us to seamlessly incorporate new WRF updates and versions in the future. We also performed a long-term WRF simulation (15 years) covering the entire North Pacific as well as high-resolution simulations of a case study which included extreme ocean heat losses in the Kuroshio and Kuroshio Extension regions. Since the extreme ocean heat loss occurs during winter cold air outbreaks (CAO), we simulated and analyzed a case study of a severe CAO event in January 2000 in detail. We found that the ocean heat loss induced by CAOs is amplified by additional advection from mesocyclones forming on the southern part of the Japan Sea. Large scale synoptic patterns with anomalously strong anticyclone over Siberia and Mongolia, deep Aleutian Low, and the Pacific subtropical ridge are a crucial setup for the CAO. It was found that the onset of the CAO is related to the breaking of atmospheric Rossby waves and vertical transport of vorticity that facilitates meridional advection. The study also indicates that intrinsic parameterization of the surface fluxes

  10. Strong coupling among Antarctic ice shelves, ocean circulation and sea ice in a global sea-ice - ocean circulation model

    NASA Astrophysics Data System (ADS)

    Sergienko, Olga

    2016-04-01

    The thermodynamic effects of Antarctic ice shelf interaction with ocean circulation are investigated using a global, high-resolution, isopycnal ocean-circulation model coupled to a sea-ice model. The model uses NASA MERRA Reanalysis from 1992 to 2011 as atmospheric forcing. The simulated long-period variability of ice-shelf melting/freezing rates differ across geographic locations. The ice shelves in Antarctic Peninsula, Amundsen and Bellingshausen sea embayments and the Amery Ice Shelf experience an increase in melting starting from 2005. This increase in melting is due to an increase in the subsurface (100-500 m) ocean heat content in the embayments of these ice shelves, which is caused by an increase in sea-ice concentration after 2005, and consequent reduction of the heat loss to the atmosphere. Our simulations provide a strong evidence for a coupling between ocean circulation, sea ice and ice shelves.

  11. Ocean Response to Possible Southern Meltwater Pulses During Eocene-Oligocene Cooling Climate Trend: A Sensitivity Ocean Modeling Study

    NASA Astrophysics Data System (ADS)

    Haupt, B. J.; Seidov, D.

    2003-12-01

    Understanding ocean circulation and sea level change in the past (and foreseeable future) is one of the focal points of paleoceanography. Sea level may change due to several primary causes, including the meltdown of the major ice sheets, sea ice melting, and changes in the thermohaline structure of the oceans. The sensitivity of the past ocean circulation to meltwater impacts may have been different from the present-day. We still have only a vague understanding of how ocean basin geography may influence the freshwater impacts in different oceans; the role of geography is important for reconstructing variability of past climates with substantially different land-sea distributions. As freshwater impacts in past geologic eras having different basins configurations may have been different from the present-day pattern, the sensitivity of the ocean circulation to sea surface density impacts and climate change could have been different as well. We use the Eocene-Oligocene geometry and climate to address the past ocean and sea level long-term internal variability because this time slice provides a substantially different geometry and for a strong sea ice impact that can be seen in the geologic record. The Eocene epoch is crucial as a transition from the warm Cretaceous ocean to cooler oceans that may have been subject to bi-polar millennial-scale oscillations of the deep ocean circulation caused by freshwater pulses of the developing southern cryosphere. In a series of numerical experiments, sea ice melting and sea water freezing around Antarctica were simulated by superimposing freshwater layers over zonally-averaged sea surface salinity. Eocene sea surface temperature and sea surface salinity are specified based on the paleoclimatic record and modeling. In our simulations, the Eocene ocean circulation is indeed sensitive to freshwater impacts in the Southern Hemisphere. There are noticeable sea level changes caused by the restructuring of the deep ocean thermal and

  12. SENSITIVITY OF THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION MULTILAYER MODEL TO INSTRUMENT ERROR AND PARAMETERIZATION UNCERTAINTY

    EPA Science Inventory

    The response of the National Oceanic and Atmospheric Administration multilayer inferential dry deposition velocity model (NOAA-MLM) to error in meteorological inputs and model parameterization is reported. Monte Carlo simulations were performed to assess the uncertainty in NOA...

  13. Simulated changes in dissolved Iron deposition to the global ocean driven by human activity

    NASA Astrophysics Data System (ADS)

    Myriokefalitakis, Stelios; Daskalakis, Nikos; Mihalopoulos, Nikos; Baker, Alex R.; Nenes, Athanassios; Kanakidou, Maria

    2015-04-01

    The global 3-d chemistry transport atmospheric model TM4-ECPL is used to simulate the atmospheric cycle of iron (Fe) and evaluate its atmospheric deposition to the ocean by accounting for both Fe natural and anthropogenic sources as well as of the proton and ligand promoted iron mobilisation from dust aerosol. Model evaluation is performed by comparison to available observations. Present day dissolved Fe deposition presents strong spatial and temporal variability with an annual deposition flux about 0.489 Tg(Fe)/yr from which about 25% are deposited over the ocean. The model simulates past, present and future iron deposition accounting for changes in anthropogenic emissions. We show that dissolved iron deposition has significantly increased since 1850 while it is expected to decrease in the future due to air pollution regulations. These changes affect the atmospheric dissolved Fe supply to High-Nutrient-Low-Chlorophyll oceanic areas characterized by Fe scarcity.

  14. High-Order/Low-Order methods for ocean modeling

    SciTech Connect

    Newman, Christopher; Womeldorff, Geoff; Chacón, Luis; Knoll, Dana A.

    2015-06-01

    We examine a High Order/Low Order (HOLO) approach for a z-level ocean model and show that the traditional semi-implicit and split-explicit methods, as well as a recent preconditioning strategy, can easily be cast in the framework of HOLO methods. The HOLO formulation admits an implicit-explicit method that is algorithmically scalable and second-order accurate, allowing timesteps much larger than the barotropic time scale. We demonstrate how HOLO approaches, in particular the implicit-explicit method, can provide a solid route for ocean simulation to heterogeneous computing and exascale environments.

  15. The role of local atmospheric forcing on the modulation of the ocean mixed layer depth in reanalyses and a coupled single column ocean model

    NASA Astrophysics Data System (ADS)

    Pookkandy, Byju; Dommenget, Dietmar; Klingaman, Nicholas; Wales, Scott; Chung, Christine; Frauen, Claudia; Wolff, Holger

    2016-02-01

    The role of local atmospheric forcing on the ocean mixed layer depth (MLD) over the global oceans is studied using ocean reanalysis data products and a single-column ocean model coupled to an atmospheric general circulation model. The focus of this study is on how the annual mean and the seasonal cycle of the MLD relate to various forcing characteristics in different parts of the world's oceans, and how anomalous variations in the monthly mean MLD relate to anomalous atmospheric forcings. By analysing both ocean reanalysis data and the single-column ocean model, regions with different dominant forcings and different mean and variability characteristics of the MLD can be identified. Many of the global oceans' MLD characteristics appear to be directly linked to the different atmospheric forcing characteristics at different locations. Here, heating and wind-stress are identified as the main drivers; in some, mostly coastal, regions the atmospheric salinity forcing also contributes. The annual mean MLD is more closely related to the annual mean wind-stress and the MLD seasonality is more closely related to the seasonality in heating. The single-column ocean model, however, also points out that the MLD characteristics over most global ocean regions, and in particular in the tropics and subtropics, cannot be maintained by local atmospheric forcings only, but are also a result of ocean dynamics that are not simulated in a single-column ocean model. Thus, lateral ocean dynamics are essential in correctly simulating observed MLD.

  16. Evaluation of a global internal-tide resolving and submesoscale admitting ocean simulation

    NASA Astrophysics Data System (ADS)

    Ubelmann, C.; Menemenlis, D.; Fu, L. L.; Zhao, Z.

    2014-12-01

    We will present ongoing evaluation of a global ocean and sea ice configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) that has 0.75 to 2.2 km horizontal grid spacing and 1-m thick vertical levels near the surface. Surface boundary conditions are from the 0.14-degree European Center for Medium-Range Weather Forecasts (ECMWF) atmospheric operational model analysis, starting in 2011, including atmospheric pressure forcing. The simulation also includes tidal forcing. A unique feature of this simulation is that we save hourly output of full 3-dimensional model prognostic variables, making it a remarkable tool for the study of ocean processes and for the simulation of satellite observations. Although this initial simulation was run without ocean data constraints, it already presents very interesting features and interactions between an exceptionally wide range of scales. The simulation resolves geostrophic eddies and internal tides and admits submesoscale variability and unbalanced dynamics such as internal waves at non-tidal frequencies.We will present some evaluation of these different components based on altimetry observations and moorings. As a first result, the internal tides for the major tidal components have overall realistic amplitudes and spatial patterns compared to independent analyses from altimetry, although some discrepancies arise in equatorial regions. Despite discrepancies with observations, this simulation already constitutes an extremely useful tool for ocean process studies and for satellite observation system experiments, for example, in preparation for the Surface Water and Ocean Topography (SWOT) mission. As a preliminary exercise, the simulation has been tested in the SWOT simulator developed at the Jet Propulsion Laboratory (Fu et al., in this session). Some illustrations of the challenges will be presented.

  17. Mapping ocean tides with satellites - A computer simulation

    NASA Technical Reports Server (NTRS)

    Won, I. J.; Kuo, J. T.; Jachens, R. C.

    1978-01-01

    As a preliminary study for the future worldwide direct mapping of the open ocean tide with satellites equipped with precision altimeters we conducted a simulated study using sets of artificially generated altimeter data constructed from a realistic geoid and four pairs of major tides in the northeastern Pacific Ocean. Recovery of the original geoid and eight tidal maps is accomplished by a space-time, least squares harmonic analysis scheme. The resultant maps appear fairly satisfactory even when random noises up to + or - 100 cm are added to the altimeter data of sufficient space-time density. The method also produces a refined geoid which is rigorously corrected for the dynamic tides.

  18. Model Scaling of Hydrokinetic Ocean Renewable Energy Systems

    NASA Astrophysics Data System (ADS)

    von Ellenrieder, Karl; Valentine, William

    2013-11-01

    Numerical simulations are performed to validate a non-dimensional dynamic scaling procedure that can be applied to subsurface and deeply moored systems, such as hydrokinetic ocean renewable energy devices. The prototype systems are moored in water 400 m deep and include: subsurface spherical buoys moored in a shear current and excited by waves; an ocean current turbine excited by waves; and a deeply submerged spherical buoy in a shear current excited by strong current fluctuations. The corresponding model systems, which are scaled based on relative water depths of 10 m and 40 m, are also studied. For each case examined, the response of the model system closely matches the scaled response of the corresponding full-sized prototype system. The results suggest that laboratory-scale testing of complete ocean current renewable energy systems moored in a current is possible. This work was supported by the U.S. Southeast National Marine Renewable Energy Center (SNMREC).

  19. Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

    NASA Astrophysics Data System (ADS)

    Martin, T.; Reintges, A.; Park, W.; Latif, M.

    2014-12-01

    Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and

  20. The Simulated Influence of Anthropogenic Climate Warming on the Oceanic Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Cao, L.; Caldeira, K.; Kheshgi, H.

    2001-12-01

    Prediction of the redistribution of anthropogenic CO2 in the atmosphere-ocean-land biosphere system is complicated by our limited understanding of the mechanisms driving carbon sequestration by the ocean and the terrestrial biosphere. Furthermore, the rates of carbon sequestration are sensitive to climate change projected to result from increases in CO2 and other greenhouse gas and changes in aerosol concentrations. This sensitivity creates feedback loops; an understanding of these feedbacks is prerequisite to forecasting future atmospheric CO2 concentrations and climate change. For instance, climate affects the oceanic carbon reservoir through the temperature-dependent relationship between total dissolved carbon and the partial pressure of CO2, and through potential climate-induced changes in ocean transport and ocean biological activity. A two-dimensional (latitude-depth) coupled atmosphere-ocean climate-carbon cycle model is developed and used to examine possible feedbacks between global climate change and the ocean carbon cycle system. The model has surface-air, land-sea, and latitudinal resolution, and is forced with diurnally averaged but seasonally varying insolation. The ocean component consists of the zonal mean balance equations of horizontal momentum, mass, temperature and salinity. The momentum balance is diagnostic, and time dependence enters through the advection-diffusion equations for temperature and salinity. The density field is calculated using a nonlinear, pressure-dependent equation of state. In this study the model is used to project future atmospheric CO2 concentrations and temperature change due to greenhouse gas and aerosol scenarios recently developed by IPCC (Nakicenovic et al., 2000), and evaluated the climate change feedback contribution to spatial and temporal changes in ocean carbon uptake. Globally, projected warming over the next century can decrease the strength of oceanic uptake of CO2 resulting in a positive feedback on CO2

  1. Origin and models of oceanic transform faults

    NASA Astrophysics Data System (ADS)

    Gerya, Taras

    2012-02-01

    Mid-ocean ridges sectioned by transform faults represent prominent surface expressions of plate tectonics. A fundamental problem of plate tectonics is how this pattern has formed and why it is maintained. Gross-scale geometry of mid-ocean ridges is often inherited from respective rifted margins. Indeed, transform faults seem to nucleate after the beginning of the oceanic spreading and can spontaneously form at a single straight ridge. Both analog and numerical models of transform faults were investigated since the 1970s. Two main groups of analog models were developed: thermomechanical (freezing wax) models with accreting and cooling plates and mechanical models with non-accreting lithosphere. Freezing wax models reproduced ridge-ridge transform faults, inactive fracture zones, rotating microplates, overlapping spreading centers and other features of oceanic ridges. However, these models often produced open spreading centers that are dissimilar to nature. Mechanical models, on the other hand, do not accrete the lithosphere and their results are thus only applicable for relatively small amount of spreading. Three main types of numerical models were investigated: models of stress and displacement distribution around transforms, models of their thermal structure and crustal growth, and models of nucleation and evolution of ridge-transform fault patterns. It was shown that a limited number of spreading modes can form: transform faults, microplates, overlapping spreading centers, zigzag ridges and oblique connecting spreading centers. However, the controversy exists whether these patterns always result from pre-existing ridge offsets or can also form spontaneously at a single straight ridge during millions of year of accretion. Therefore, two types of transform fault interpretation exist: plate fragmentation structures vs. plate accretion structures. Models of transform faults are yet relatively scarce and partly controversial. Consequently, a number of first order

  2. Final Report. Coupled simulations of Antarctic Ice-sheet/ocean interactions using POP and CISM

    SciTech Connect

    Asay-Davis, Xylar Storm

    2015-12-30

    The project performed under this award, referred to from here on as CLARION (CoupLed simulations of Antarctic Ice-sheet/Ocean iNteractions), included important advances in two models of ice sheet and ocean interactions. Despite its short duration (one year), the project made significant progress on its three major foci. First, together with collaborator Daniel Martin at Lawrence Berkeley National Laboratory (LBNL), I developed the POPSICLES coupled ice sheet-ocean model to the point where it could perform a number of pan-Antarctic simulations under various forcing conditions. The results were presented at a number of major conferences and workshops worldwide, and are currently being incorporated into two manuscripts in preparation.

  3. Analyzing the Effect of Tropical Cyclones on the Upper Ocean Using an Ocean General Circulation Model with Varying Horizontal Grid Resolution

    NASA Astrophysics Data System (ADS)

    Li, H.; Sriver, R. L.

    2015-12-01

    Tropical cyclones (TCs) have the potential to influence regional and global climate through their interactions with the upper ocean. Here we present results from a suite of ocean-only model experiments featuring the Community Earth System Model (CESM), in which we analyze the effect of tropical cyclone wind forcing on the global ocean using three different horizontal ocean grid resolutions (3˚, 1˚, and 0.1˚). The ocean simulations are forced with identical atmospheric inputs from the Coordinated Ocean-Ice Reference Experiments version 2 (COREv2) normal year forcing conditions, featuring global blended TC winds from a fully-coupled CESM simulation with a 25 km atmosphere [Small et al., 2014]. The simulated TC climatology shows good agreement with observational estimates of annual TC statistics, including annual frequency, intensity distributions, and geographic distributions. Each simulation is 10 years, which includes a 5-year spin up and 5 years of TC-wind forcing. In addition, we conduct corresponding control simulations for each grid resolution configuration without applied TC forcing. We will discuss the TC-induced ocean responses across a variety of spatial and temporal scales. A key highlight of this work is analyzing the effect of ocean horizontal grid resolution on TC-induced ocean responses, particularly at resolutions capable of simulating mesoscale ocean eddies.

  4. The Fidelity of Ocean Models With Explicit Eddies (Chapter 17)

    SciTech Connect

    McClean, J; Jayne, S; Maltrud, M; Ivanova, D

    2007-08-01

    Current practices within the oceanographic community have been reviewed with regard to the use of metrics to assess the realism of the upper-ocean circulation, ventilation processes diagnosed by time-evolving mixed layer depth and mode water formation, and eddy heat fluxes in large-scale fine resolution ocean model simulations. We have striven to understand the fidelity of these simulations in the context of their potential use in future fine-resolution coupled climate system studies. A variety of methodologies are used to assess the veracity of the numerical simulations. Sea surface height variability and the location of western boundary current paths from altimetry have been used routinely as basic indicators of fine-resolution model performance. Drifters and floats have also been used to provide pseudo-Eulerian measures of the mean and variability of surface and sub-surface flows, while statistical comparisons of observed and simulated means have been carried out using James tests. Probability density functions have been used to assess the Gaussian nature of the observed and simulated flows. Length and time scales have been calculated in both Eulerian and Lagrangian frameworks from altimetry and drifters, respectively. Concise measures of multiple model performance have been obtained from Taylor diagrams. The time-evolution of the mixed layer depth at monitoring stations has been compared with simulated time series. Finally, eddy heat fluxes are compared to climatological inferences.

  5. An abrupt climate event in a coupled ocean-atmosphere simulation without external forcing.

    PubMed

    Hall, A; Stouffer, R J

    2001-01-11

    Temperature reconstructions from the North Atlantic region indicate frequent abrupt and severe climate fluctuations during the last glacial and Holocene periods. The driving forces for these events are unclear and coupled atmosphere-ocean models of global circulation have only simulated such events by inserting large amounts of fresh water into the northern North Atlantic Ocean. Here we report a drastic cooling event in a 15,000-yr simulation of global circulation with present-day climate conditions without the use of such external forcing. In our simulation, the annual average surface temperature near southern Greenland spontaneously fell 6-10 standard deviations below its mean value for a period of 30-40 yr. The event was triggered by a persistent northwesterly wind that transported large amounts of buoyant cold and fresh water into the northern North Atlantic Ocean. Oceanic convection shut down in response to this flow, concentrating the entire cooling of the northern North Atlantic by the colder atmosphere in the uppermost ocean layer. Given the similarity between our simulation and observed records of rapid cooling events, our results indicate that internal atmospheric variability alone could have generated the extreme climate disruptions in this region. PMID:11196636

  6. Global warming in a coupled climate model including oceanic eddy-induced advection

    NASA Astrophysics Data System (ADS)

    Hirst, Anthony C.; Gordon, Hal B.; O'Farrell, Siobhan P.

    The Gent and McWilliams (GM) parameterization for large-scale water transport caused by mesoscale oceanic eddies is introduced into the oceanic component of a global coupled ocean-atmosphere model. Parallel simulations with and without the GM scheme are performed to examine the effect of this parameterization on model behavior under constant atmospheric CO2 and on the model response to increasing CO2. The control (constant CO2) runs show substantial differences in the oceanic stratification and extent of convection, similar to differences found previously using uncoupled ocean models. The transient (increasing CO2) runs show moderate differences in the rate of oceanic heat sequestration (less in the GM case), as expected based on passive tracer uptake studies. However, the surface warming is weaker in the GM case, especially over the Southern Ocean, which is contrary to some recent supposition. Reasons for the reduced warming in the GM case are discussed.

  7. Serving ocean model data on the cloud

    USGS Publications Warehouse

    Meisinger, M.; Farcas, C.; Farcas, E.; Alexander, Corrine; Arrott, M.; de La Beaujardière, J.; Hubbard, P.; Mendelssohn, R.; Signell, R.

    2009-01-01

    The NOAA-led Integrated Ocean Observing System (IOOS) and the NSF-funded Ocean Observatories Initiative Cyberinfrastructure Project (OOI-CI) are collaborating on a prototype data delivery system for numerical model output and other gridded data using cloud computing. The strategy is to take an existing distributed system for delivering gridded data and redeploy on the cloud, making modifications to the system that allow it to harness the scalability of the cloud as well as adding functionality that the scalability affords. ??2009 MTS.

  8. Low-frequency variability in a climate model with a mixed-layer ocean

    SciTech Connect

    Gould-Stewart, S.

    1984-11-01

    A mixed-layer ocean model coupled to a global spectral atmospheric circulation model produces a warming in the model equatorial Pacific Ocean similar to the El Nino or Southern Oscillation (SO) response. The mechanism for producing the SO-like response in an ocean with heat storage and without ocean dynamics is investigated. The model is capable of simulating SO-like time scales, but the details of the structure of the warming differ significantly from the observed El Nino/Southern Oscillation (ENSO) response. 22 refs.

  9. Effect of mineral dust on ocean color retrievals from space: A radiative transfer simulation study

    NASA Astrophysics Data System (ADS)

    Ahmad, Z.; Franz, B. A.

    2014-12-01

    Mineral aerosols (dust) are one of the major components of all aerosols found in the Earth's atmosphere. They are mainly soil particles that originate from arid and semiarid regions of the world that can be carried by winds for thousands of kilometers. They are a major impediment in the remote sensing of the ocean color (spectral water-leaving reflectance), because they absorb solar radiation in the UV and visible part of the spectrum and their micro-physical and optical properties are highly variable. Further, there are no reliable working algorithms to detect their presence from spaceborne ocean color observations alone, when they are present in small amount (optical thickness < 0.2). In this paper we examine effect of mineral dust on ocean color retrieval from space. We use Ahmad-Fraser's vector radiative transfer (RT) code (v3.0) for ocean-atmosphere system to simulate the pseudo observations (top of atmosphere radiance) for models containing different types of aerosols (absorbing and non-absorbing) in the atmosphere. We consider the mineral aerosols as consisting of an external mixture of illite, kaolinite, montmorillonite, quartz, and calcite with a small amount of hematite (as an internal mixture), which provide the spectral dependence of single scattering albedo consistent with the values reported in the literature. We also vary the aerosol layer height in the atmosphere and amount of chlorophyll in the ocean. The simulated pseudo observations were processed through standard NASA algorithms to determine the ocean color (spectral water-leaving reflectance) and derived chlorophyll in the ocean. Results of the RT simulation study for different Sun-satellite viewing geometry, aerosol layer height and chlorophyll amount in the ocean is presented.

  10. Polarimetric lidar returns in the ocean: a Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Adams, James T.; Kattawar, George W.

    1997-02-01

    Anisotropy in the polarization state of backscattered light from a polarized beam incident on suspensions in water analogous to hydrosols in seawater has been observed experimentally. Viewed through an orientated polarizer, characteristic patterns in the backscattered light are produced. We wish to present the results of Monte Carlo simulations of these physical effects demonstrating excellent agreement with published and unpublished experimental observations. These simulations show that the effects observed are produced by the incoherent scattering of light in the range of volume fractions reported and that this treatment should a low predictions to be made about the application of this technique to ocean probing lidar.

  11. Assimilation of altimeter topography into oceanic models

    NASA Technical Reports Server (NTRS)

    Demey, Pierre; Menard, Yves; Pinardi, Nadia; Schroeter, J.; Verron, J.

    1991-01-01

    The primary goals of the authors are to build an intuition for assimilation techniques and to investigate the impact of variable altimeter topography on simple or complex oceanic models. In particular, applying various techniques and sensitivity studies to model and data constraints plays a key role. We are starting to use quasi-geostrophic, semigeostrophic, and primitive-equation (PE) models and to test the schemes in regions of interest to the World Ocean Circulation Experiment (WOCE), as well as in the northeast Atlantic and the Mediterranean. The impact of scatterometer wind forcing on the results is also investigated. The use of Geosat, European Remote Sensing satellite (ERS-1), and TOPEX/POSEIDON altimetry data is crucial in fine tuning the models and schemes to the selected areas of interest.

  12. Aviation Safety Simulation Model

    NASA Technical Reports Server (NTRS)

    Houser, Scott; Yackovetsky, Robert (Technical Monitor)

    2001-01-01

    The Aviation Safety Simulation Model is a software tool that enables users to configure a terrain, a flight path, and an aircraft and simulate the aircraft's flight along the path. The simulation monitors the aircraft's proximity to terrain obstructions, and reports when the aircraft violates accepted minimum distances from an obstruction. This model design facilitates future enhancements to address other flight safety issues, particularly air and runway traffic scenarios. This report shows the user how to build a simulation scenario and run it. It also explains the model's output.

  13. Modelling the Oceanic Nd Isotopic Composition With a North Atlantic Eddy Permitting Model

    NASA Astrophysics Data System (ADS)

    Peronne, S.; Treguier, A.; Arsouze, T.; Dutay, J.; Lacan, F.; Jeandel, C.

    2006-12-01

    The oceanic water masses differ by their temperatures, salinity, but also a number of geochemical tracers characterized by their weak concentrations and their ability to quantify oceanic processes (mixing, scavenging rates etc). Among these tracers, the Nd isotopic composition (hereafter epsilon-Nd) is a (quasi) conservative tracer of water mass mixing in the ocean interior, far from any lithogenic inputs. It has been recently established that exchange of Nd at the oceanic margins could be the dominant process controlling both its concentration and isotopic composition distribution in the ocean. This was demonstrated using in situ measurements and budget calculations and has recently been confirmed by a low resolution (2°) modeling approach (Arsouze et al., 2006). However, the currents flowing on the ocean margins are not correctly represented in coarse ocean models. It is the case in the North Atlantic ocean, which is of particular interest since i) it is the area of deep water formation and ii) these deep waters are characterized by the most negative epsilon-Nd values of the world ocean, which are used as "imprint" of the present and past thermohaline circulation. It is therefore essential to understand how these water masses acquire their epsilon-Nd signature. We propose here the first results of the modeling of oceanic Nd isotopic composition at eddy-permitting resolution, with the North Atlantic 0.25° version of the NEMO model used for the DRAKKAR European project. A 150 years off-line experiment and a shorter on-line experiment are performed. Simulated Nd distributions are compared to the present-day data base, vertical profiles, and the results of the low resolution model (in the North Atlantic). The eddy permitting model generally provides improved results, provided a high enough exchange rate is imposed in the deep ocean. Deficiencies of the simulated distribution in the Nordic Seas and the subpolar gyre are explained by errors in the input function on

  14. Partially molten magma ocean model

    SciTech Connect

    Shirley, D.N.

    1983-02-15

    The properties of the lunar crust and upper mantle can be explained if the outer 300-400 km of the moon was initially only partially molten rather than fully molten. The top of the partially molten region contained about 20% melt and decreased to 0% at 300-400 km depth. Nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt, then grew peripherally until they coverd the moon. Throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick. The thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below. Concentrations of Sr, Eu, and Sm in pristine ferroan anorthosites are found to be consistent with this model, as are trends for the ferroan anorthosites and Mg-rich suites on a diagram of An in plagioclase vs. mg in mafics. Clustering of Eu, Sr, and mg values found among pristine ferroan anorthosites are predicted by this model.

  15. Ocean Biogeochemistry and Phytoplankton Ecology in a Global Simulation

    NASA Astrophysics Data System (ADS)

    Moore, J. K.; Doney, S. C.; Lindsay, K.

    2005-05-01

    A coupled Biogeochemistry/Ecosystem/Circulation (BEC) model is used to examine ocean biogeochemistry and phytoplankton ecology at the global scale. Phytoplankton groups represented in the model include diatoms, diazotrophs, coccolithophores and picoplankton. The groups experience differential grazing pressure and compete for light and the potentially growth-limiting nutrients iron, nitrate, ammonium, phosphate, and silicate. The model includes several key aspects of the global nitrogen cycle including nitrogen fixation (by the diazotrophs), water column denitrification under low oxygen conditions, and atmospheric nitrogen deposition to the oceans. We examine how these nitrogen fluxes influence ecosystem structure and also how light and nutrient availability restrict phytoplankton growth rates over seasonal timescales. Atmospheric deposition of mineral dust also inputs dissolved iron to the ocean model. These iron additions modify phytoplankton community composition, and rates of production and export in the iron-limited High Nitrate, Low Chlorophyll regions, and indirectly modify ecosystem dynamics by altering rates of nitrogen fixation in nitrogen-depleted, tropical and subtropical regions. We will examine the links between dust/iron deposition and nitrogen cycling in the oceans.

  16. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification

    NASA Astrophysics Data System (ADS)

    Zhang, Han; Cao, Long

    2016-02-01

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scenario with SRES A2 CO2 emission until 2100 and zero emission afterwards, by year 3500, in the simulation without CO2-calcification feedback, model projects an accumulated ocean CO2 uptake of 1462 PgC, atmospheric CO2 of 612 ppm, and surface pH of 7.9. Inclusion of CO2-calcification feedback increases ocean CO2 uptake by 9 to 285 PgC, reduces atmospheric CO2 by 4 to 70 ppm, and mitigates the reduction in surface pH by 0.003 to 0.06, depending on the form of parameterization scheme used. It is also found that the effect of CO2-calcification feedback on ocean carbon uptake is comparable and could be much larger than the effect from CO2-induced warming. Our results highlight the potentially important role CO2-calcification feedback plays in ocean carbon cycle and projections of future atmospheric CO2 concentrations.

  17. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification.

    PubMed

    Zhang, Han; Cao, Long

    2016-01-01

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scenario with SRES A2 CO2 emission until 2100 and zero emission afterwards, by year 3500, in the simulation without CO2-calcification feedback, model projects an accumulated ocean CO2 uptake of 1462 PgC, atmospheric CO2 of 612 ppm, and surface pH of 7.9. Inclusion of CO2-calcification feedback increases ocean CO2 uptake by 9 to 285 PgC, reduces atmospheric CO2 by 4 to 70 ppm, and mitigates the reduction in surface pH by 0.003 to 0.06, depending on the form of parameterization scheme used. It is also found that the effect of CO2-calcification feedback on ocean carbon uptake is comparable and could be much larger than the effect from CO2-induced warming. Our results highlight the potentially important role CO2-calcification feedback plays in ocean carbon cycle and projections of future atmospheric CO2 concentrations. PMID:26838480

  18. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification.

    PubMed

    Zhang, Han; Cao, Long

    2016-02-03

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scenario with SRES A2 CO2 emission until 2100 and zero emission afterwards, by year 3500, in the simulation without CO2-calcification feedback, model projects an accumulated ocean CO2 uptake of 1462 PgC, atmospheric CO2 of 612 ppm, and surface pH of 7.9. Inclusion of CO2-calcification feedback increases ocean CO2 uptake by 9 to 285 PgC, reduces atmospheric CO2 by 4 to 70 ppm, and mitigates the reduction in surface pH by 0.003 to 0.06, depending on the form of parameterization scheme used. It is also found that the effect of CO2-calcification feedback on ocean carbon uptake is comparable and could be much larger than the effect from CO2-induced warming. Our results highlight the potentially important role CO2-calcification feedback plays in ocean carbon cycle and projections of future atmospheric CO2 concentrations.

  19. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification

    PubMed Central

    Zhang, Han; Cao, Long

    2016-01-01

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scenario with SRES A2 CO2 emission until 2100 and zero emission afterwards, by year 3500, in the simulation without CO2-calcification feedback, model projects an accumulated ocean CO2 uptake of 1462 PgC, atmospheric CO2 of 612 ppm, and surface pH of 7.9. Inclusion of CO2-calcification feedback increases ocean CO2 uptake by 9 to 285 PgC, reduces atmospheric CO2 by 4 to 70 ppm, and mitigates the reduction in surface pH by 0.003 to 0.06, depending on the form of parameterization scheme used. It is also found that the effect of CO2-calcification feedback on ocean carbon uptake is comparable and could be much larger than the effect from CO2-induced warming. Our results highlight the potentially important role CO2-calcification feedback plays in ocean carbon cycle and projections of future atmospheric CO2 concentrations. PMID:26838480

  20. Continental and oceanic crustal magnetization modelling

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.; Hayling, K. L.

    1984-01-01

    Inversion of magnetic data from the MAGSAT satellite, to arrive at intensities of magnetization of the Earth's crust, was performed by two different methods. The first method uses a spherical harmonic model of the magnetic field. The coefficients believed to represent sources in the Earth's crust can then be inverted to arrive at vertical dipole moments per unit area at the Earth's surface. The spherical harmonic models contain coefficients of degrees of harmonics up to 23. The dipole moment per unit area for a surface element can then be determined by summing the contribution for each individual degree of harmonic. The magnetic moments were calculated for continental and oceanic areas separately as well as over certain latitudinal segments. Of primary concern was to determine whether there are any differences between continental and oceanic areas. The second analysis with magnetization intensities was made using narrower ranges of degrees of harmonics, assuming that higher degrees are present in the core field signal.

  1. Modelling ocean carbon cycle with a nonlinear convolution model

    NASA Astrophysics Data System (ADS)

    Kheshgi, Haroon S.; White, Benjamin S.

    1996-02-01

    A nonlinear convolution integral is developed to model the response of the ocean carbon sink to changes in the atmospheric concentration of CO2. This model can accurately represent the atmospheric response of complex ocean carbon cycle models in which the nonlinear behavior stems from the nonlinear dependence of CO2 solubility in seawater on CO2 partial pressure, which is often represented by the buffer factor. The kernel of the nonlinear convolution model can be constructed from a response of such a complex model to an arbitrary change in CO2 emissions, along with the functional dependence of the buffer factor. Once the convolution kernel has been constructed, either analytically or from a model experiment, the convolution representation can be used to estimate responses of the ocean carbon sink to other changes in the atmospheric concentration of CO2. Thus the method can be used, e.g., to explore alternative emissions scenarios for assessments of climate change. A derivation for the nonlinear convolution integral model is given, and the model is used to reproduce the response of two carbon cycle models: a one-dimensional diffusive ocean model, and a three-dimensional ocean-general-circulation tracer model.

  2. Experimental design for three interrelated Marine Ice-Sheet and Ocean Model Intercomparison Projects

    NASA Astrophysics Data System (ADS)

    Asay-Davis, X. S.; Cornford, S. L.; Durand, G.; Galton-Fenzi, B. K.; Gladstone, R. M.; Gudmundsson, G. H.; Hattermann, T.; Holland, D. M.; Holland, D.; Holland, P. R.; Martin, D. F.; Mathiot, P.; Pattyn, F.; Seroussi, H.

    2015-11-01

    Coupled ice sheet-ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions in the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the ice shelf-ocean MIP second phase (ISOMIP+) and coupled ice sheet-ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for evaluation of the participating models.

  3. Simulating the Oceanic Migration of Silver Japanese Eels.

    PubMed

    Chang, Yu-Lin; Miyazawa, Yasumasa; Béguer-Pon, Mélanie

    2016-01-01

    The oceanic migration of silver Japanese eels starts from their continental growth habitats in East Asia and ends at the spawning area near the West Mariana Ridge seamount chain. However, the actual migration routes remain unknown. In this study, we examined the possible oceanic migration routes and strategies of silver Japanese eels using a particle tracking method in which virtual eels (v-eels) were programmed to move vertically and horizontally in an ocean circulation model (Japan Coastal Ocean Predictability Experiment 2, JCOPE2). Four horizontal swimming strategies were tested: random heading, true navigation (readjusted heading), orientation toward the spawning area (fixed heading), and swimming against the Kuroshio. We found that all strategies, except random swimming, allowed v-eels swimming at 0.65 m s-1 to reach the spawning area within eight months after their departure from the south coast of Japan (end of the spawning season). The estimated minimum swimming speed required to reach the area spawning within eight months was 0.1 m s-1 for true navigation, 0.12 m s-1 for constant compass heading, and 0.35 m s-1 for swimming against the Kuroshio. The lowest swimming speed estimated from tracked Japanese eels at sea was 0.03 m.s-1, which would not allow them to reach the spawning area within eight months, through any of the tested orientation strategies. Our numerical experiments also showed that ocean circulation significantly affected the migration of Japanese v-eels. A strong Kuroshio could advect v-eels further eastward. In addition, western Pacific ocean currents accelerated the migration of navigating v-eels. The migration duration was shortened in years with a stronger southward flow, contributed by a stronger recirculation south of Japan, an enhanced subtropical gyre, or a higher southward Kuroshio velocity.

  4. Simulating the Oceanic Migration of Silver Japanese Eels.

    PubMed

    Chang, Yu-Lin; Miyazawa, Yasumasa; Béguer-Pon, Mélanie

    2016-01-01

    The oceanic migration of silver Japanese eels starts from their continental growth habitats in East Asia and ends at the spawning area near the West Mariana Ridge seamount chain. However, the actual migration routes remain unknown. In this study, we examined the possible oceanic migration routes and strategies of silver Japanese eels using a particle tracking method in which virtual eels (v-eels) were programmed to move vertically and horizontally in an ocean circulation model (Japan Coastal Ocean Predictability Experiment 2, JCOPE2). Four horizontal swimming strategies were tested: random heading, true navigation (readjusted heading), orientation toward the spawning area (fixed heading), and swimming against the Kuroshio. We found that all strategies, except random swimming, allowed v-eels swimming at 0.65 m s-1 to reach the spawning area within eight months after their departure from the south coast of Japan (end of the spawning season). The estimated minimum swimming speed required to reach the area spawning within eight months was 0.1 m s-1 for true navigation, 0.12 m s-1 for constant compass heading, and 0.35 m s-1 for swimming against the Kuroshio. The lowest swimming speed estimated from tracked Japanese eels at sea was 0.03 m.s-1, which would not allow them to reach the spawning area within eight months, through any of the tested orientation strategies. Our numerical experiments also showed that ocean circulation significantly affected the migration of Japanese v-eels. A strong Kuroshio could advect v-eels further eastward. In addition, western Pacific ocean currents accelerated the migration of navigating v-eels. The migration duration was shortened in years with a stronger southward flow, contributed by a stronger recirculation south of Japan, an enhanced subtropical gyre, or a higher southward Kuroshio velocity. PMID:26982484

  5. Effect of Aerosol and Ocean Representation on Simulated Climate Responses

    NASA Astrophysics Data System (ADS)

    Dallafior, Tanja; Folini, Doris; Knutti, Reto; Wild, Martin

    2016-04-01

    It is still debated to what extent anthropogenic aerosols shaped 20th century surface temperatures, especially sea surface temperatures (SSTs), through alteration of surface solar radiation (SSR). SSTs, in turn, are crucial in the context of atmospheric circulation and ocean heat uptake. Uncertainty considering anthropogenic aerosol forcing thus translates into uncertainty regarding ocean heat uptake and, ultimately, climate responses towards anthropogenic influences. We use the global climate model ECHAM to analyse the 20th century climate response towards either anthropogenic aerosols or well-mixed greenhouse gases or both with different representations of ocean and aerosols: atmosphere-only with prescribed SSTs and interactive aerosols; mixed-layer ocean and interactive or prescribed aerosols; fully coupled with prescribed aerosols. For interactive aerosols we use the Hamburg Aerosol Module (HAM). Our results suggest that up to 15% of global ocean surfaces undergo an SSR reduction of at least -4W/m² in the year 2000, due to anthropogenic aerosols. The area affected depends on how aerosols are represented and whether clear sky or all sky SSR is considered. In MLO equilibria with interactive aerosols, anthropogenic aerosols clearly shape surface temperature response patterns. This is to a lesser degree the case for the transient fully coupled case. Additivity of global mean temperature responses towards single forcings - an assumption often made in the literature - is not fulfilled for the MLO experiments, but for the fully coupled experiments. While some of these differences can be attributed to the differing ocean representation, it is implied that differing aerosol representation may play an even more relevant role. Thus, our results corroborate not only the relevance of anthropogenic aerosols for surface temperature responses, but also highlight the relevance of choice of aerosol representation.

  6. Simulating the Oceanic Migration of Silver Japanese Eels

    PubMed Central

    Chang, Yu-Lin; Miyazawa, Yasumasa; Béguer-Pon, Mélanie

    2016-01-01

    The oceanic migration of silver Japanese eels starts from their continental growth habitats in East Asia and ends at the spawning area near the West Mariana Ridge seamount chain. However, the actual migration routes remain unknown. In this study, we examined the possible oceanic migration routes and strategies of silver Japanese eels using a particle tracking method in which virtual eels (v-eels) were programmed to move vertically and horizontally in an ocean circulation model (Japan Coastal Ocean Predictability Experiment 2, JCOPE2). Four horizontal swimming strategies were tested: random heading, true navigation (readjusted heading), orientation toward the spawning area (fixed heading), and swimming against the Kuroshio. We found that all strategies, except random swimming, allowed v-eels swimming at 0.65 m s−1 to reach the spawning area within eight months after their departure from the south coast of Japan (end of the spawning season). The estimated minimum swimming speed required to reach the area spawning within eight months was 0.1 m s−1 for true navigation, 0.12 m s−1 for constant compass heading, and 0.35 m s−1 for swimming against the Kuroshio. The lowest swimming speed estimated from tracked Japanese eels at sea was 0.03 m.s−1, which would not allow them to reach the spawning area within eight months, through any of the tested orientation strategies. Our numerical experiments also showed that ocean circulation significantly affected the migration of Japanese v-eels. A strong Kuroshio could advect v-eels further eastward. In addition, western Pacific ocean currents accelerated the migration of navigating v-eels. The migration duration was shortened in years with a stronger southward flow, contributed by a stronger recirculation south of Japan, an enhanced subtropical gyre, or a higher southward Kuroshio velocity. PMID:26982484

  7. Response of the Antarctic ice sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model

    NASA Astrophysics Data System (ADS)

    Martin, D. F.; Asay-Davis, X.; Price, S. F.; Cornford, S. L.; Maltrud, M. E.; Ng, E. G.; Collins, W.

    2014-12-01

    We present the response of the continental Antarctic ice sheet to sub-shelf-melt forcing derived from POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1 degree (~5 km) ocean resolution and ice sheet resolution as fine as 500 m using adaptive mesh refinement. A comparison of fully-coupled and comparable standalone ice-sheet model results demonstrates the importance of two-way coupling between the ice sheet and the ocean. The POPSICLES model couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). BISICLES makes use of adaptive mesh refinement to fully resolve dynamically-important regions like grounding lines and employs a momentum balance similar to the vertically-integrated formulation of Schoof and Hindmarsh (2009). Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests like MISMIP3D (Pattyn et al., 2013) and realistic configurations (Favier et al. 2014). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). A companion presentation, "Present-day circum-Antarctic simulations using the POPSICLES coupled land ice-ocean model" in session C027 describes the ocean-model perspective of this work, while we focus on the response of the ice sheet and on details of the model. The figure shows the BISICLES-computed vertically-integrated ice velocity field about 1 month into a 20-year coupled Antarctic run. Groundling lines are shown in green.

  8. A Pacific Ocean general circulation model for satellite data assimilation

    NASA Technical Reports Server (NTRS)

    Chao, Y.; Halpern, D.; Mechoso, C. R.

    1991-01-01

    A tropical Pacific Ocean General Circulation Model (OGCM) to be used in satellite data assimilation studies is described. The transfer of the OGCM from a CYBER-205 at NOAA's Geophysical Fluid Dynamics Laboratory to a CRAY-2 at NASA's Ames Research Center is documented. Two 3-year model integrations from identical initial conditions but performed on those two computers are compared. The model simulations are very similar to each other, as expected, but the simulations performed with the higher-precision CRAY-2 is smoother than that with the lower-precision CYBER-205. The CYBER-205 and CRAY-2 use 32 and 64-bit mantissa arithmetic, respectively. The major features of the oceanic circulation in the tropical Pacific, namely the North Equatorial Current, the North Equatorial Countercurrent, the South Equatorial Current, and the Equatorial Undercurrent, are realistically produced and their seasonal cycles are described. The OGCM provides a powerful tool for study of tropical oceans and for the assimilation of satellite altimetry data.

  9. Interannual simulation of tropical oceans during 1958-2014 using a high resolution OGCM

    NASA Astrophysics Data System (ADS)

    Yamanaka, Goro; Tsujino, Hiroyuki; Nakano, Hideyuki; Urakawa, Shogo; Sakamoto, Kei

    2016-04-01

    We develop a high-resolution tropical ocean model (0.2 deg. x 0.1 deg.) nested to a low-resolution global domain model (1 deg. x 0.5 deg.). We use a two-way nesting approach which allows for communication between the global model and the nest in both directions. A comparison between the high and low-resolution models is made to examine the impact of horizontal resolution on tropical ocean simulations. The long-term mean simulated Indonesian Throughflow transport in the higher-resolution model (13.1 Sv) agrees well with the observed estimate (about 15 Sv). The higher-resolution model permits more enhanced representation of Equatorial Upwelling and horizontal current shear north of the equator. Tropical instability waves (TIWs) in the equatorial Pacific and Atlantic Oceans are more clearly resolved in the higher-resolution model with larger amplitudes. TIWs enhance meridional heat exchange in the eastern tropical Pacific, which results in relative SST warming north of the equator, while enhanced upwelling in the high-resolution model results in relative SST cooling at the equator and along the South American coast. This means that the high-resolution model further strengthens the north-south asymmetry of the mean equatorial Pacific SSTs.

  10. Two- and Three-Dimensional Simulations of Asteroid Ocean Impacts

    NASA Astrophysics Data System (ADS)

    Gisler, G.; Weaver, R.; Gittings, M.; Mader, C.

    2002-12-01

    We have performed a series of two-dimensional and three-dimensional simulations of asteroid impacts into an ocean using the SAGE code from Los Alamos National Laboratory and Science Applications International Corporation. The SAGE code is a compressible Eulerian hydrodynamics code using continuous adaptive mesh refinement for following discontinuities with a fine grid while treating the bulk of the simulation more coarsely. We have used realistic equations of state for the atmosphere, sea water, the oceanic crust, and the mantle. In two dimensions, we simulated asteroid impactors moving at 20 km/s vertically through an exponential atmosphere into a 5 km deep ocean. The impactors were composed of mantle material (3.32 g/cc) or iron (7.8 g/cc) with diameters from 250m to 10 km. In our three-dimensional runs we simulated asteroids of 1 km diameter composed of iron moving at 20 km/s at angles of 45 and 60 degrees from the vertical. All impacts, including the oblique ones, produce a large underwater cavities with nearly vertical walls followed by a collapse starting from the bottom and subsequent vertical jetting. Substantial amounts of water are vaporized and lofted high into the atmosphere. In the larger impacts, significant amounts of crustal and even mantle material are lofted as well. Tsunamis up to a kilometer in initial height are generated by the collapse of the vertical jet. These waves are initially complex in form, and interact strongly with shocks propagating through the water and the crust. The tsunami waves are followed out to 100 km from the point of impact. Their periods and wavelengths show them to be intermediate type waves, and not (in general) shallow-water waves. At great distances, the waves decay as the inverse of the distance from the impact point, ignoring sea-floor topography. For all impactors smaller than about 2 km diameter, the impacting body is highly fragmented and its remains lofted into the stratosphere with the water vapor and crustal

  11. Two- and Three-Dimensional Simulations of Asteroid Ocean Impacts

    NASA Astrophysics Data System (ADS)

    Gisler, G.; Weaver, R. P.; Mader, C. L.; Gittings, M. L.

    2003-01-01

    We have performed a series of two-dimensional and three-dimensional simulations of asteroid impacts into an ocean using the SAGE code from Los Alamos National Laboratory and Science Applications International Corporation. The SAGE code is a compressible Eulerian hydrodynamics code using continuous adaptive mesh refinement for following discontinuities with a fine grid while treating the bulk of the simulation more coarsely. We have used tabular equations of state for the atmosphere, water, the oceanic crust, and the mantle. In two dimensions, we simulated asteroid impactors moving at 20 km/s vertically through an exponential atmosphere into a 5 km deep ocean. The impactors were composed of mantle material (3.32 g/cc) or iron (7.8 g/cc) with diameters from 250m to 10 km. In our three-dimensional runs we simulated asteroids of 1 km diameter composed of iron moving at 20 km/s at angles of 45 and 60 degrees from the vertical. All impacts, including the oblique ones, produce large underwater cavities with nearly vertical walls followed by a collapse starting from the bottom and subsequent vertical jetting. Substantial amounts of water are vaporized and lofted high into the atmosphere. In the larger impacts, significant amounts of crustal and even mantle material are lofted as well. Tsunamis up to a kilometer in initial height are generated by the collapse of the vertical jet. These waves are initially complex in form, and interact strongly with shocks propagating through the water and the crust. The tsunami waves are followed out to 100 km from the point of impact. Their periods and wavelengths show them to be intermediate type waves, and not (in general) shallow-water waves. At great distances, the waves decay faster than the inverse of the distance from the impact point, ignoring sea-floor topography. For all impactors smaller than about 2 km diameter, the impacting body is highly fragmented and its remains lofted into the stratosphere with the water vapor and crustal

  12. Computer Modeling and Simulation

    SciTech Connect

    Pronskikh, V. S.

    2014-05-09

    Verification and validation of computer codes and models used in simulation are two aspects of the scientific practice of high importance and have recently been discussed by philosophers of science. While verification is predominantly associated with the correctness of the way a model is represented by a computer code or algorithm, validation more often refers to model’s relation to the real world and its intended use. It has been argued that because complex simulations are generally not transparent to a practitioner, the Duhem problem can arise for verification and validation due to their entanglement; such an entanglement makes it impossible to distinguish whether a coding error or model’s general inadequacy to its target should be blamed in the case of the model failure. I argue that in order to disentangle verification and validation, a clear distinction between computer modeling (construction of mathematical computer models of elementary processes) and simulation (construction of models of composite objects and processes by means of numerical experimenting with them) needs to be made. Holding on to that distinction, I propose to relate verification (based on theoretical strategies such as inferences) to modeling and validation, which shares the common epistemology with experimentation, to simulation. To explain reasons of their intermittent entanglement I propose a weberian ideal-typical model of modeling and simulation as roles in practice. I suggest an approach to alleviate the Duhem problem for verification and validation generally applicable in practice and based on differences in epistemic strategies and scopes

  13. Ocean modelling aspects for drift applications

    NASA Astrophysics Data System (ADS)

    Stephane, L.; Pierre, D.

    2010-12-01

    Nowadays, many authorities in charge of rescue-at-sea operations lean on operational oceanography products to outline research perimeters. Moreover, current fields estimated with sophisticated ocean forecasting systems can be used as input data for oil spill/ adrift object fate models. This emphasises the necessity of an accurate sea state forecast, with a mastered level of reliability. This work focuses on several problems inherent to drift modeling, dealing in the first place with the efficiency of the oceanic current field representation. As we want to discriminate the relevance of a particular physical process or modeling option, the idea is to generate series of current fields of different characteristics and then qualify them in term of drift prediction efficiency. Benchmarked drift scenarios were set up from real surface drifters data, collected in the Mediterranean sea and off the coasts of Angola. The time and space scales that we are interested in are about 72 hr forecasts (typical timescale communicated in case of crisis), for distance errors that we hope about a few dozen of km around the forecast (acceptable for reconnaissance by aircrafts) For the ocean prediction, we used some regional oceanic configurations based on the NEMO 2.3 code, nested into Mercator 1/12° operational system. Drift forecasts were computed offline with Mothy (Météo France oil spill modeling system) and Ariane (B. Blanke, 1997), a Lagrangian diagnostic tool. We were particularly interested in the importance of the horizontal resolution, vertical mixing schemes, and any processes that may impact the surface layer. The aim of the study is to ultimately point at the most suitable set of parameters for drift forecast use inside operational oceanic systems. We are also motivated in assessing the relevancy of ensemble forecasts regarding determinist predictions. Several tests showed that mis-described observed trajectories can finally be modelled statistically by using uncertainties

  14. Oceanic Carbon Dioxide Uptake in a Model of Century-Scale Global Warming

    PubMed

    Sarmiento; Le Quéré C

    1996-11-22

    In a model of ocean-atmosphere interaction that excluded biological processes, the oceanic uptake of atmospheric carbon dioxide (CO2) was substantially reduced in scenarios involving global warming relative to control scenarios. The primary reason for the reduced uptake was the weakening or collapse of the ocean thermohaline circulation. Such a large reduction in this ocean uptake would have a major impact on the future growth rate of atmospheric CO2. Model simulations that include a simple representation of biological processes show a potentially large offsetting effect resulting from the downward flux of biogenic carbon. However, the magnitude of the offset is difficult to quantify with present knowledge.

  15. Oceanic Carbon Dioxide Uptake in a Model of Century-Scale Global Warming

    PubMed

    Sarmiento; Le Quéré C

    1996-11-22

    In a model of ocean-atmosphere interaction that excluded biological processes, the oceanic uptake of atmospheric carbon dioxide (CO2) was substantially reduced in scenarios involving global warming relative to control scenarios. The primary reason for the reduced uptake was the weakening or collapse of the ocean thermohaline circulation. Such a large reduction in this ocean uptake would have a major impact on the future growth rate of atmospheric CO2. Model simulations that include a simple representation of biological processes show a potentially large offsetting effect resulting from the downward flux of biogenic carbon. However, the magnitude of the offset is difficult to quantify with present knowledge. PMID:8910268

  16. Subsurface radar location of the putative ocean on Ganymede: Numerical simulation of the surface terrain impact

    NASA Astrophysics Data System (ADS)

    Ilyushin, Ya. A.

    2014-03-01

    Exploration of subsurface oceans on Jupiter's icy moons is a key issue of the icy moons' geology. Radar is in fact the only sounding technique which is able to penetrate their icy mantles, which can be many kilometers thick. Surface clutter, i.e. scattering of the radio waves on the rough surface, is known to be one of the most important problems of subsurface radar probing. Adequate numerical modeling of this scattering is required on all stages of subsurface radar experiment, including design of an instrument, operational strategy planning and data interpretation. In the present paper, a computer simulation technique for numerical simulations of radar sounding of rough surfaces is formulated in general form. Subsurface radar location of the ocean beneath Ganymedian ice with chirp radar signals has been simulated.

  17. Theory Modeling and Simulation

    SciTech Connect

    Shlachter, Jack

    2012-08-23

    Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.

  18. Modelling coral polyp calcification in relation to ocean acidification

    NASA Astrophysics Data System (ADS)

    Hohn, S.; Merico, A.

    2012-11-01

    Rising atmospheric CO2 concentrations due to anthropogenic emissions induce changes in the carbonate chemistry of the oceans and, ultimately, a drop in ocean pH. This acidification process can harm calcifying organisms like coccolithophores, molluscs, echinoderms, and corals. It is expected that ocean acidification in combination with other anthropogenic stressors will cause a severe decline in coral abundance by the end of this century, with associated disastrous effects on reef ecosystems. Despite the growing importance of the topic, little progress has been made with respect to modelling the impact of acidification on coral calcification. Here we present a model for a coral polyp that simulates the carbonate system in four different compartments: the seawater, the polyp tissue, the coelenteron, and the calcifying fluid. Precipitation of calcium carbonate takes place in the metabolically controlled calcifying fluid beneath the polyp tissue. The model is adjusted to a state of activity as observed by direct microsensor measurements in the calcifying fluid. We find that a transport mechanism for bicarbonate is required to supplement carbon into the calcifying fluid because CO2 diffusion alone is not sufficient to sustain the observed calcification rates. Simulated CO2 perturbation experiments reveal decreasing calcification rates under elevated pCO2 despite the strong metabolic control of the calcifying fluid. Diffusion of CO2 through the tissue into the calcifying fluid increases with increasing seawater pCO2, leading to decreased aragonite saturation in the calcifying fluid. Our modelling study provides important insights into the complexity of the calcification process at the organism level and helps to quantify the effect of ocean acidification on corals.

  19. Modeling High-Resolution Coastal Ocean Dynamics with COAMPS: System Overview, Applications and Future Directions

    NASA Astrophysics Data System (ADS)

    Allard, R. A.; Campbell, T. J.; Edwards, K. L.; Smith, T.; Martin, P.; Hebert, D. A.; Rogers, W.; Dykes, J. D.; Jacobs, G. A.; Spence, P. L.; Bartels, B.

    2014-12-01

    The Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS®) is an atmosphere-ocean-wave modeling system developed by the Naval Research Laboratory which can be configured to cycle regional forecasts/analysis models in single-model (atmosphere, ocean, and wave) or coupled-model (atmosphere-ocean, ocean-wave, and atmosphere-ocean-wave) modes. The model coupling is performed using the Earth System Modeling Framework (ESMF). The ocean component is the Navy Coastal Ocean Model (NCOM), and the wave components include Simulating WAves Nearshore (SWAN) and WaveWatch-III. NCOM has been modified to include wetting and drying, the effects of Stokes drift current, wave radiation stresses due to horizontal gradients of the momentum flux of surface waves, enhancement of bottom drag in shallow water, and enhanced vertical mixing due to Langmuir turbulence. An overview of the modeling system including ocean data assimilation and specification of boundary conditions will be presented. Results from a high-resolution (10-250m) modeling study from the Surfzone Coastal Oil Pathways Experiment (SCOPE) near Ft. Walton Beach, Florida in December 2013 will be presented. ®COAMPS is a registered trademark of the Naval Research Laboratory

  20. Simulated 21st century's increase in oceanic suboxia by CO2-enhanced biotic carbon export

    NASA Astrophysics Data System (ADS)

    Oschlies, Andreas; Schulz, Kai G.; Riebesell, Ulf; Schmittner, Andreas

    2008-12-01

    The primary impacts of anthropogenic CO2 emissions on marine biogeochemical cycles predicted so far include ocean acidification, global warming induced shifts in biogeographical provinces, and a possible negative feedback on atmospheric CO2 levels by CO2-fertilized biological production. Here we report a new potentially significant impact on the oxygen-minimum zones of the tropical oceans. Using a model of global climate, ocean circulation, and biogeochemical cycling, we extrapolate mesocosm-derived experimental findings of a pCO2-sensitive increase in biotic carbon-to-nitrogen drawdown to the global ocean. For a simulation run from the onset of the industrial revolution until A.D. 2100 under a "business-as-usual" scenario for anthropogenic CO2 emissions, our model predicts a negative feedback on atmospheric CO2 levels, which amounts to 34 Gt C by the end of this century. While this represents a small alteration of the anthropogenic perturbation of the carbon cycle, the model results reveal a dramatic 50% increase in the suboxic water volume by the end of this century in response to the respiration of excess organic carbon formed at higher CO2 levels. This is a significant expansion of the marine "dead zones" with severe implications not only for all higher life forms but also for oxygen-sensitive nutrient recycling and, hence, for oceanic nutrient inventories.

  1. Modeling oceanic multiphase flow by using Lagrangian particle tracking

    NASA Astrophysics Data System (ADS)

    Matsumura, Y.

    2014-12-01

    While the density of seawater is basically determined by its temperature, salinity and pressure, the effective density becomes higher when the water mass contains suspended sediment. On the other hands, effective density declines when water mass contains fine scale materials of lower density such as bubbles and ice crystals. Such density anomaly induced by small scale materials suspended in water masses sometimes plays important roles in the sub-mesoscale ocean physics. To simulate these small scale oceanic multiphase flow, a new modeling framework using an online Lagrangian particle tracking method is developed. A Lagrangian particle tracking method has substantial advantages such as an explicit treatment of buoyancy force acting on each individual particle, no numerical diffusion and dissipation, high dynamic range and an ability to track the history and each individual particle. However, its numerical cost causes difficulty when we try to simulate a large number of particles. In the present study we implement a numerically efficient particle tracking scheme using linked-list data structure, which is coupled with a nonhydrostatic dynamical core. This newly developed model successfully reproduces characteristics of some interesting small scale multiphase processes, for example hyperpycnal flow (a sediment-rich river water plume trapped at ocean floor) and grease ice cover (a slurry mixture of frazil ice crystals and seawater).

  2. LABORATORY EXPERIMENTS TO SIMULATE CO2 OCEAN DISPOSAL

    SciTech Connect

    Stephen M. Masutani

    1999-12-31

    This Final Technical Report summarizes the technical accomplishments of an investigation entitled ''Laboratory Experiments to Simulate CO{sub 2} Ocean Disposal'', funded by the U.S. Department of Energy's University Coal Research Program. This investigation responds to the possibility that restrictions on greenhouse gas emissions may be imposed in the future to comply with the Framework Convention on Climate Change. The primary objective of the investigation was to obtain experimental data that can be applied to assess the technical feasibility and environmental impacts of oceanic containment strategies to limit release of carbon dioxide (CO{sub 2}) from coal and other fossil fuel combustion systems into the atmosphere. A number of critical technical uncertainties of ocean disposal of CO{sub 2} were addressed by performing laboratory experiments on liquid CO{sub 2} jet break-up into a dispersed droplet phase, and hydrate formation, under deep ocean conditions. Major accomplishments of this study included: (1) five jet instability regimes were identified that occur in sequence as liquid CO{sub 2} jet disintegration progresses from laminar instability to turbulent atomization; (2) linear regression to the data yielded relationships for the boundaries between the five instability regimes in dimensionless Ohnesorge Number, Oh, and jet Reynolds Number, Re, space; (3) droplet size spectra was measured over the full range of instabilities; (4) characteristic droplet diameters decrease steadily with increasing jet velocity (and increasing Weber Number), attaining an asymptotic value in instability regime 5 (full atomization); and (5) pre-breakup hydrate formation appears to affect the size distribution of the droplet phase primary by changing the effective geometry of the jet.

  3. An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations: Hydrography and fluxes

    NASA Astrophysics Data System (ADS)

    Ilicak, Mehmet; Drange, Helge

    2016-04-01

    We compare the simulated Arctic Ocean in fifteen global ocean-sea ice models in the framework of the Coordinated Ocean-ice Reference Experiments, phase II (CORE-II). Most of these models are the ocean and sea-ice components of the coupled climate models used in the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments. We mainly focus on the hydrography of the Arctic interior, the state of Atlantic Water layer and heat and volume transports at the gateways of the Davis Strait, the Bering Strait, the Fram Strait and the Barents Sea Opening. We found that there is a large spread in temperature in the Arctic Ocean between the models, and generally large differences compared to the observed temperature at intermediate depths. Warm bias models have a strong temperature anomaly of inflow of the Atlantic Water entering the Arctic Ocean through the Fram Strait. Another process that is not represented accurately in the CORE-II models is the formation of cold and dense water, originating on the eastern shelves. In the cold bias models, excessive cold water forms in the Barents Sea and spreads into the Arctic Ocean through the St. Anna Through. There is a large spread in the simulated mean heat and volume transports through the Fram Strait and the Barents Sea Opening. The models agree more on the decadal variability, to a large degree dictated by the common atmospheric forcing. We conclude that the CORE-II model study helps us to understand the crucial biases in the Arctic Ocean. The current coarse resolution state-of-the-art ocean models need to be improved in accurate representation of the Atlantic Water inflow into the Arctic and density currents coming from the shelves.

  4. Numerical simulation of short period Earth rotation variations induced by ocean tides

    NASA Astrophysics Data System (ADS)

    Goss, Andreas; Schindelegger, Michael; Seitz, Florian

    2016-04-01

    The Dynamic Model for Earth Rotation and Gravity (DyMEG) has been used in several previous studies for the numerical simulation of Earth rotation (polar motion and length-of-day) on time scales from seasons to decades. Our current activities aim at the extension of the model and its application for the simulation of high frequency Earth rotation signals with periods of a few hours up to several days. This requires several model adaptations, such as the incorporation of additional excitation mechanisms as well as the identification and implementation of an appropriate numerical integrator. Here we particularly focus on the effect of ocean tides as they - due to their strictly periodic signal characteristics - provide a good possibility to evaluate the performance of the model and to detect potential computational problems. Secondary effects due to atmospheric and non-tidal oceanic influences are incorporated as well. We validate the simulated polar motion and length-of-day time series against hourly GNSS (Global Navigation Satellite System) data and conventional ocean tide routines of the IERS (International Earth Rotation and Reference Systems Service).

  5. The Effect of Atmosphere-Ocean-Wave Interactions and Model Resolution on Hurricane Katrina in a Coupled Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Patricola, C. M.; Chang, P.; Saravanan, R.; Montuoro, R.

    2012-04-01

    The sensitivity of simulated strength, track, and structure of Hurricane Katrina to atmospheric model resolution, cumulus parameterization, and initialization time, as well as mesoscale ocean-atmosphere interactions with and without small-scale ocean-wave effect, are investigated with a fully coupled regional climate model. The atmosphere, ocean, and wave components are represented by the Weather Research and Forecasting Model (WRF), Regional Ocean Modeling System (ROMS), and Simulating WAves Nearshore (SWAN) model. Uncoupled atmosphere-only simulations with horizontal resolutions of 1, 3, 9, and 27 km show that while the simulated cyclone track is highly sensitive to initialization time, its dependence on model resolution is relatively weak. Using NCEP/CFSR reanalysis as initial and boundary conditions, WRF, even at low resolution, is able to track Katrina accurately for 3 days before it made landfall on August 29, 2005. Katrina's strength, however, is much more difficult to reproduce and exhibits a strong dependence on model resolution. At its lowest resolution (27 km), WRF is only capable of simulating a maximum strength of Category 2 storm. Even at 1 km resolution, the simulated Katrina only reaches Category 4 storm intensity. Further WRF experiments with and without cumulus parameterization reveal minor changes in strength. None of the WRF-only simulations capture the observed rapid intensification of Katrina to Category 5 when it passed over a warm Loop-Current eddy (LCE) in the Gulf of Mexico, suggesting that mesoscale ocean-atmosphere interactions involving LCEs may play a crucial role in Katrina's rapid intensification. Coupled atmosphere-ocean simulations are designed and carried out to investigate hurricane Katrina-LCE interactions with and without considering small-scale ocean wave processes in order to fully understand the dynamical ocean-atmosphere processes in the observed rapid cyclone intensification.

  6. Simulating the modern δ30Si distribution in the oceans and in marine sediments

    NASA Astrophysics Data System (ADS)

    Gao, S.; Wolf-Gladrow, D. A.; Völker, C.

    2016-02-01

    The δ30Si of biogenic silica (δ30SiBSi) in marine sediments is a promising proxy for the reconstruction of silicic acid utilization by diatoms in the geological past. The application of this proxy, however, requires an understanding of the modern δ30Si distributions and their controlling mechanisms. Here we present results from a modern climate simulation with a coupled ocean-sediment model that includes a prognostic formulation of biogenic silica production with concurrent silicon isotopic fractionation. In agreement with previous studies, biological fractionation combined with physical transport and mixing determines the oceanic distribution of simulated δ30Si. A new finding is a distinct seasonal cycle of δ30Si in the surface ocean, which is inversely related to that of silicic acid concentration and mixed layer depth. We also provide the first simulation results of sedimentary δ30Si, which reveal that (1) the δ30SiBSi distribution in the surface sediment reflects the exported δ30SiBSi signal from the euphotic zone and (2) the dissolution of biogenic silica in the sediment acts as a source of relatively light δ30Si into the bottom waters of the polar oceans, while it is a source of heavier δ30Si to the subtropical South Atlantic and South Pacific.

  7. The sensitivity of dimethyl sulfide production to simulated climate change in the Eastern Antarctic Southern Ocean

    NASA Astrophysics Data System (ADS)

    Gabric, Albert J.; Cropp, Roger; Hirst, Tony; Marchant, Harvey

    2003-11-01

    Dimethyl sulfide (DMS) is a radiatively active trace gas produced by enzymatic cleavage of its precursor compound, dimethyl sulfoniopropionate (DMSP), which is released by marine phytoplankton in the upper ocean. Once ventilated to the atmosphere, DMS is oxidised to form non-sea-salt sulfate and methane sulfonate (MSA) aerosols, which are a major source of cloud condensation nuclei (CCN) in remote marine air and may thus play a role in climate regulation. Here we simulate the change in DMS flux in the Eastern Antarctic ocean from 1960 2086, corresponding to equivalent CO2 tripling relative to pre-industrial levels. Calibration to contemporary climate conditions was carried out using a genetic algorithm to fit the model to surface chlorophyll from the 4-yr SeaWiFs satellite archive and surface DMS from an existing global database. Following the methodology used previously in the Subantarctic Southern Ocean, we then simulated DMS emissions under enhanced greenhouse conditions by forcing the DMS model with output from a coupled atmospheric ocean general circulation model (GCM). The GCM was run in transient mode under the IPCC/IS92a radiative forcing scenario. By 2086, the change simulated in annual integrated DMS flux is around 20% in ice-free waters, with a greater increase of 45% in the seasonal ice zone (SIZ). Interestingly, the large increase in flux in the SIZ is not due to higher in situ production but mainly because of a loss of ice cover during summer autumn and an increase in sea-to-air ventilation of DMS. These proportional changes in areal mean flux (25%) are much higher than previously estimated for the Subantarctic Southern Ocean (5%), and point to the possibility of a significant DMS climate feedback at high Southern latitudes. Due to the nexus between ice cover and food-web structure, the potential for ecological community shifts under enhanced greenhouse conditions is high, and the implications for DMS production are discussed.

  8. The Leading Modes of Decadal SST Variability in the Southern Ocean in CMIP5 Simulations

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Dommenget, Dietmar

    2016-04-01

    The leading modes of Sea Surface Temperature (SST) variability in the Southern Ocean on decadal and even larger time scales are analysed using Coupled Model Intercomparison Project 5 (CMIP5) model simulations and observations. We compare the modes from the CMIP5 super ensemble against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability and the physical processes affecting the characteristics of the modes. The results show three main modes in the Southern Ocean: the first and most dominant mode on interannual to decadal time scales is an annular mode with largest amplitudes in the Pacific, which is strongly related to atmospheric forcing by the Southern Annular Mode (SAM) and El Nino Southern Oscillation (ENSO). The second mode is an almost basin wide monopole pattern, which has pronounced multi-decadal and longer time scales variability. It is firstly inducted by the Wave-3 patterns in the atmosphere and further developed via ocean dynamics. The third mode is a dipole pattern in the southern Pacific that has a pronounced peak in the power spectrum at multi-decadal time scales. All three leading modes found in the CMIP5 super model have distinct patterns and time scale behaviour that can not be explained by simple stochastic null hypothesis, thus all three leading modes are ocean-atmospheric coupled modes and are likely to be substantially influenced or driven by ocean dynamical processes. The mechanism of the basin-wide mode is further analysed based on a series of idealized experiments. The results show that the monopole mode has a two-step power spectrum, with a first spectral increase on interannual time scale and a second higher up level on the multi-decadal to centennial time scales. Ocean dynamics, especially the ocean advection, transport the anomalous signals, connect the entire ocean and lead to the homogeneous-like spatial pattern even under stochastic

  9. Modeled ocean circulation in Nares Strait and its dependence on landfast-ice cover

    NASA Astrophysics Data System (ADS)

    Shroyer, Emily L.; Samelson, Roger M.; Padman, Laurie; Münchow, Andreas

    2015-12-01

    Two simplified ocean simulations are used to study circulation and transport within Nares Strait. The simulations are similar, except that one included a coupled sea ice model that effectively established a landfast ice cover throughout the simulation year. Comparison between the ocean-only and ocean-ice simulations reveals a systematic change in the current structure, reminiscent of the seasonal shift under mobile and landfast ice previously observed in Nares Strait. A surface-intensified jet, which carries low-salinity water along the strait's centerline, develops within the ocean-only simulation. The current structure under landfast ice is characterized by a subsurface jet located along the western side with low-salinity surface water distributed along the eastern side of the strait. Intermediate salinity water is offset to the west in the ice-ocean simulation relative to the ocean-only simulation, while high-salinity water (>34.8) is constrained to recirculations that are located north and south of a sill in Kane Basin. The simulations, combined with an idealized, semianalytical model, suggest that the structural shift is caused by the surface Ekman layer beneath the landfast ice and the associated eastward advection of near-surface low-salinity water and westward movement of the jet. Temporal variability in the ocean-ice simulation is dominated by the remote response to the time-dependent northern boundary conditions. In contrast, the ocean-only simulation favors an instability and additionally responds to local surface wind forcing, which enhances the variability within the strait above that imposed at the boundaries.

  10. The DEBOT Model, a New Global Barotropic Ocean Tidal Model: Test Computations and an Application in Related Geophysical Disciplines

    NASA Astrophysics Data System (ADS)

    Einspigel, D.; Sachl, L.; Martinec, Z.

    2014-12-01

    We present the DEBOT model, which is a new global barotropic ocean model. The DEBOT model is primarily designed for modelling of ocean flow generated by the tidal attraction of the Moon and the Sun, however it can be used for other ocean applications where the barotropic model is sufficient, for instance, a tsunami wave propagation. The model has been thoroughly tested by several different methods: 1) synthetic example which involves a tsunami-like wave propagation of an initial Gaussian depression and testing of the conservation of integral invariants, 2) a benchmark study with another barotropic model, the LSGbt model, has been performed and 3) results of realistic simulations have been compared with data from tide gauge measurements around the world. The test computations prove the validity of the numerical code and demonstrate the ability of the DEBOT model to simulate the realistic ocean tides. The DEBOT model will be principaly applied in related geophysical disciplines, for instance, in an investigation of an influence of the ocean tides on the geomagnetic field or the Earth's rotation. A module for modelling of the secondary poloidal magnetic field generated by an ocean flow is already implemented in the DEBOT model and preliminary results will be presented. The future aim is to assimilate magnetic data provided by the Swarm satellite mission into the ocean flow model.

  11. Numerical investigation of algebraic oceanic turbulent mixing-layer models

    NASA Astrophysics Data System (ADS)

    Chacón-Rebollo, T.; Gómez-Mármol, M.; Rubino, S.

    2013-11-01

    In this paper we investigate the finite-time and asymptotic behaviour of algebraic turbulent mixing-layer models by numerical simulation. We compare the performances given by three different settings of the eddy viscosity. We consider Richardson number-based vertical eddy viscosity models. Two of these are classical algebraic turbulence models usually used in numerical simulations of global oceanic circulation, i.e. the Pacanowski-Philander and the Gent models, while the other one is a more recent model (Bennis et al., 2010) proposed to prevent numerical instabilities generated by physically unstable configurations. The numerical schemes are based on the standard finite element method. We perform some numerical tests for relatively large deviations of realistic initial conditions provided by the Tropical Atmosphere Ocean (TAO) array. These initial conditions correspond to states close to mixing-layer profiles, measured on the Equatorial Pacific region called the West-Pacific Warm Pool. We conclude that mixing-layer profiles could be considered as kinds of "absorbing configurations" in finite time that asymptotically evolve to steady states under the application of negative surface energy fluxes.

  12. The leading modes of decadal SST variability in the Southern Ocean in CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Dommenget, Dietmar

    2016-09-01

    The leading modes of Sea Surface Temperature variability in the Southern Ocean on decadal and even larger time scales are analysed using Coupled Model Intercomparison Project 5 (CMIP5) model simulations and observations. The analysis is based on Empirical Orthogonal Function modes of the CMIP5 model super ensemble. We compare the modes from the CMIP5 super ensemble against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability and the physical processes affecting the characteristics of the modes. The results show three main modes in the Southern Ocean: the first and most dominant mode on interannual to decadal time scales is an annular mode with largest amplitudes in the Pacific, which is strongly related to atmospheric forcing by the Southern Annular Mode and El Nino Southern Oscillation. The second mode is an almost basin wide monopole pattern, which has pronounced multi-decadal and longer time scales variability. It is firstly inducted by the Wave-3 patterns in the atmosphere and further developed via ocean dynamics. The third mode is a dipole pattern in the southern Pacific that has a pronounced peak in the power spectrum at multi-decadal time scales. All three leading modes found in the CMIP5 super model have distinct patterns and time scale behaviour that can not be explained by simple stochastic null hypothesis, thus all three leading modes are ocean-atmosphere coupled modes and are likely to be substantially influenced or driven by ocean dynamical processes.

  13. Mean Sea Level Derived from Altimetry and Wind-Driven Numerical Models in the Indian Ocean

    NASA Technical Reports Server (NTRS)

    Perigaud, C.; Delecluse, P.; Greiner, E.; Rogel, P.

    1995-01-01

    Wind-driven model skill in simulating sea level variations in the Indian Ocean depends on our knowledge of the mean ocean dynamic topography. This is demonstrated by running the nonlinear or linear version of a shallow-water model driven by observed winds over Geosat and TOPEX periods. Geosat variations are assimilated in the nonlinear shallow-water model with the objective of obtaining topography data.

  14. Analyzing Glacial-Interglacial Ocean Biogeochemical States in the MPI-Earth System Model

    NASA Astrophysics Data System (ADS)

    Heinze, M.; Ilyina, T.

    2015-12-01

    There is still little consensus about the mechanisms causing the glacial - interglacial variationsin atmospheric CO2 concentrations of around 100 ppm. Some of those mechanisms aredriven by alterations in ocean biogeochemical cycles. Hence, it is crucial to understand oceanbiogeochemistry dynamics during glacial-interglacial transitions. Within the German nationalclimate modeling initiative PalMod, aiming at simulating a full glacial cycle (135k - today) intransient mode with a state-of-the-art Earth System Model (ESM), we address the oceanbiogeochemistry cycles using a comprehensive modeling approach. In order to set up themodel we start with ocean only simulations, which are based on the 3-D ocean generalcirculation model MPIOM coupled to the ocean biogeochemistry model HAMOCC.Atmospheric forcing data is derived from a fully coupled LGM simulation including theatmosphere general circulation model ECHAM6. This setup provides us a sophisticatedrepresentation of the ocean biogeochemistry during the LGM without using any kind of datarestoring,to be consistent with the biological, chemical and physical dynamics of the model.We analyze alterations in ocean biogeochemistry during the LGM in comparison to a preindustrialcontrol climate. We discuss and quantify the changes in ocean biogeochemicalcycles between these two states, as well as possible implications for carbon transfer due tochanges in ocean dynamics. In the next steps we will use the ocean biogeochemistry model aspart of the fully coupled MPI-ESM. Our results aim at improving the understanding of glacial- interglacial changes in atmospheric CO2, especially in terms of marine carbon sequestrationand release. The presented work contributes to developing comprehensive ESMs, which arecapable of simulating the climate evolution and the variability during the last glacial cycle.

  15. Parameterization of mixed layer eddies. III: Implementation and impact in global ocean climate simulations

    NASA Astrophysics Data System (ADS)

    Fox-Kemper, B.; Danabasoglu, G.; Ferrari, R.; Griffies, S. M.; Hallberg, R. W.; Holland, M. M.; Maltrud, M. E.; Peacock, S.; Samuels, B. L.

    A parameterization for the restratification by finite-amplitude, submesoscale, mixed layer eddies, formulated as an overturning streamfunction, has been recently proposed to approximate eddy fluxes of density and other tracers. Here, the technicalities of implementing the parameterization in the coarse-resolution ocean component of global climate models are made explicit, and the primary impacts on model solutions of implementing the parameterization are discussed. Three global ocean general circulation models including this parameterization are contrasted with control simulations lacking the parameterization. The MLE parameterization behaves as expected and fairly consistently in models differing in discretization, boundary layer mixing, resolution, and other parameterizations. The primary impact of the parameterization is a shoaling of the mixed layer, with the largest effect in polar winter regions. Secondary impacts include strengthening the Atlantic meridional overturning while reducing its variability, reducing CFC and tracer ventilation, modest changes to sea surface temperature and air-sea fluxes, and an apparent reduction of sea ice basal melting.

  16. Evaluating Consistency in the Ocean Model Component of the Community Earth System Model

    NASA Astrophysics Data System (ADS)

    Hammerling, D.; Hu, Y.; Baker, A. H.; Huang, X.; Tseng, Y. H.; Bryan, F.

    2015-12-01

    We developed a new ensemble-based statistical method for evaluating the consistency in the Parallel Ocean Program (POP), the ocean model component of the Community Earth System Model (CESM). Since the ocean dynamics are chaotic in nature, a roundoff-level perturbation in the initial conditions will potentially result in distinct model solutions. No bit-for-bit (BFB) identical results in ocean solutions can be guaranteed for even tiny code modification. Our approach takes the natural variability of the ocean model into account through POP ensemble simulations. In particular, the statistical distribution from an ensemble of POP simulations is used to determine the standard score of any new model solution at each grid point. This setup accounts for the spatial heterogeneity in variability within the ensemble. Then the percentage of grid points which have scores greater than a specified threshold indicates whether the new model simulation is statistically distinguishable from the ensemble simulations. We evaluate the new tool on three types of scenarios: running with different processor layouts, changing the physical parameterization, and varying the convergence tolerance in the barotropic solver. Results indicate that our new testing tool is capable of distinguishing cases which should be consistent with the ensemble, such as the solutions with different processor layouts, and those which should not, such as increasing a certain physical parameter by two or more times. This new tool provides a simple, subjective and systematic way to evaluate the difference between the given solution and the ensemble, thus facilitating the detection of errors introduced during model development.

  17. Comparison of a coupled atmosphere-ocean (WRF-ROMS) model with an atmosphere only model (WRF) of two North Atlantic hurricanes

    NASA Astrophysics Data System (ADS)

    Mooney, P.; Mulligan, F. J.; Bruyere, C. L.; Bonnlander, B.

    2013-12-01

    We investigate the ability of a coupled regional atmosphere-ocean modeling system to simulate two extreme events in the North Atlantic. In this study we use the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST; Warner et al., 2010) modeling system with only the atmosphere and ocean models activated. COAWST couples the atmosphere model (Weather Research and Forecasting model; WRF) to the ocean model (Regional Ocean Modeling System; ROMS) with the Model Coupling Toolkit. Results from the coupled system are compared with atmosphere only simulations of North Atlantic storms to evaluate the performance of the coupled modeling system. Two extreme events (Hurricane Katia and Hurricane Irene) were chosen to assess the level of improvement (or otherwise) arising from coupling WRF with ROMS. These two hurricanes involve different dynamics and present different challenges to the modeling system. Modelled storm tracks, storm intensities and sea surface temperatures are compared with observations to appraise the coupled modeling system's simulation of these two extreme events.

  18. Long-term ocean simulations in FESOM: evaluation and application in studying the impact of Greenland Ice Sheet melting

    NASA Astrophysics Data System (ADS)

    Wang, Xuezhu; Wang, Qiang; Sidorenko, Dmitry; Danilov, Sergey; Schröter, Jens; Jung, Thomas

    2012-12-01

    The Finite Element Sea-ice Ocean Model (FESOM) is formulated on unstructured meshes and offers geometrical flexibility which is difficult to achieve on traditional structured grids. In this work, the performance of FESOM in the North Atlantic and Arctic Ocean on large time scales is evaluated in a hindcast experiment. A water-hosing experiment is also conducted to study the model sensitivity to increased freshwater input from Greenland Ice Sheet (GrIS) melting in a 0.1-Sv discharge rate scenario. The variability of the Atlantic Meridional Overturning Circulation (AMOC) in the hindcast experiment can be explained by the variability of the thermohaline forcing over deep convection sites. The model also reproduces realistic freshwater content variability and sea ice extent in the Arctic Ocean. The anomalous freshwater in the water-hosing experiment leads to significant changes in the ocean circulation and local dynamical sea level (DSL). The most pronounced DSL rise is in the northwest North Atlantic as shown in previous studies, and also in the Arctic Ocean. The released GrIS freshwater mainly remains in the North Atlantic, Arctic Ocean and the west South Atlantic after 120 model years. The pattern of ocean freshening is similar to that of the GrIS water distribution, but changes in ocean circulation also contribute to the ocean salinity change. The changes in Arctic and sub-Arctic sea level modify exchanges between the Arctic Ocean and subpolar seas, and hence the role of the Arctic Ocean in the global climate. Not only the strength of the AMOC, but also the strength of its decadal variability is notably reduced by the anomalous freshwater input. A comparison of FESOM with results from previous studies shows that FESOM can simulate past ocean state and the impact of increased GrIS melting well.

  19. Simulations of the tides of ancient oceans and the evolution of the Earth-Moon system

    NASA Astrophysics Data System (ADS)

    Nerge, P.; Ludwig, T.; Thomas, M.; Jungclaus, J.; Sündermann, J.; Brosche, P.

    2012-04-01

    We will simulate the spatial and temporal characteristics of the ocean tides for the present time as well as for a time slice of the Neoproterozoic Era (˜620 Ma b.p.). A focus will be on the transfer of angular momentum between the Earth and the Moon in order to physically simulate the observed increase of day length and the Moon's distance. The numerical results will be validated against geological proxy data of the tidal spectrum of the Australian continental plate. Subsequently, the evolution of the ocean tides under the influence of the continental drift from present time until the Neoproterozoic will be simulated. Again, a focus will be on the transfer of angular momentum between the Earth and Moon in order to physically explain the dynamical evolution of the Earth-Moon system and, therewith, the increase of day length of about 2 hours as well as the decrease of month length of about 1 day. The simulation of the ocean tides shall be carried out with the three-dimensional Max-Planck-Institute ocean circulation model (Marsland, et al., 2003) forced by the complete lunisolar tidal potential (Thomas, 2001). A curvilinear grid with freely selectable grid poles is utilized by the model. Hence, the resolution can be efficiently increased around Australia for evaluation of our results. The simulations require exceptional performance in computing and storage that is provided by the German Climate Computing Center. So far, the limited availability of geological proxy data has prevented a detailed quantification of the transfer of angular momentum in the Earth-Sun-Moon-system mainly due ocean tides far back in the Earth's history. Considering recent paleontological data, and advances in numerical modelling and high performance computing, we will strive to reduce these deficits. First self-consistent geological data on ocean tides, Earth's rotational parameters and orbital elements of the Moon have been provided by the research of Williams (2000) on the sediment layers

  20. Numerical simulation of environment modulation of chemical signal structure and odor dispersal in the open ocean.

    PubMed

    Baird, R C; Johari, H; Jumper, G Y

    1996-04-01

    Hydrodynamic models were used to simulate the dispersal of a model fish pheromone at three characteristic depth regimes (mixed layer, and 300 and 1000 m) of broad extent in the open ocean at the scale of individual organisms. The models were calibrated to experimental studies of dye dispersal at these depths and the goldfish pheromone system was used as the model odorant. There are profound differences in the time course and geometry of dispersing odor fields with depths. Below the thermocline odor fields spread primarily as horizontal patches with dispersal rates about five times slower at 1000 m as compared to 300 m. In the mixed layer, odors disperse rapidly in all directions and the maximum radial distance of spread of a physiologically active odor patch is less than half of the deep water value. Increases in the threshold sensitivity of olfactory receptors can greatly increase effective odor field size. Chemical signals impact the encounter dynamics among oceanic organisms by affecting the distance at which the target (emitting) individual is perceived. Perception distances due to olfactory cues can be significantly greater than for other senses in pelagic oceanic environments. Environment specific modulation of odor fields then affects the signal properties and therefore utility of chemoreception that, in turn, bear on encounter probabilities and transfer functions in oceanic ecosystems.

  1. Model of Methane Hydrate Formation in Mid-ocean Ridges

    NASA Astrophysics Data System (ADS)

    Dmitrievsky, A. N.; Balanyuk, I. E.; Sorokhtin, O. G.; Matveenkov, V. V.; Dongaryan, L. Sh.

    2003-04-01

    MODEL OF METHANE HYDRATE FORMATION IN MID-OCEAN RIDGES A.N. Dmitrievsky, I.E. Balanyuk, O.G.Sorokhtin, V.V. Matveenkov, and L.Sh. Dongaryan P.P.Shirshov Institute of Oceanology Russian Academy of Sciences Moscow, Russia, balanyuk@sio.rssi.ru One among the most perspective direction in studying the ocean floor is the research of hydrothermal fields within the most active zones — rift valleys, where the processes of spreading of the ocean floor, uplift of the deep matter to the surface of the ocean floor, and creation of the new oceanic crust occur. Volcanic activity in these zones is accompanied with the formation of the hydrothermal system executing separation, transfer, and precipitation of a series of chemical elements. It is known that ore deposits with high concentration of iron, manganese, copper, nickel, cobalt are formed as a result of hydrothermal activity. It is much less known that hydrothermal activity in these zones has important but not so evident result — the formation of hydrocarbons in the form of methane hydrates. We propose the hypothesis of formation of methane hydrate deposits over the shallow slopes of the mid-oceanic ridges as an outcome of the action of two factors: the thermal convection of water in fractured-porous rocks of the crust and the reaction of serpentinization of the crust. The intensive exhalation of hydrocarbons takes place in the process of serpentinization. The conditions of water convection in the porous media are favorable for the formation and accumulation of methane hydrates in the near-surface layers of the oceanic crust. The carbonic-acid gas dissolved in the seawater is involved into the process of methane hydrate formation. It was established that the most favorable conditions for this mechanism are over the slopes of the Mid-Atlantic Ridge. All types of water areas where gas hydrates occur can be conditionally subdivided into following geodynamic zones: the abyssal basins of the inner and marginal seas, the

  2. How well do coupled models replicate ocean energetics relevant to ENSO?

    NASA Astrophysics Data System (ADS)

    Brown, Jaclyn N.; Fedorov, Alexey V.; Guilyardi, Eric

    2011-06-01

    Accurate replication of the processes associated with the energetics of the tropical ocean is necessary if coupled GCMs are to simulate the physics of ENSO correctly, including the transfer of energy from the winds to the ocean thermocline and energy dissipation during the ENSO cycle. Here, we analyze ocean energetics in coupled GCMs in terms of two integral parameters describing net energy loss in the system using the approach recently proposed by Brown and Fedorov (J Clim 23:1563-1580, 2010a) and Fedorov (J Clim 20:1108-1117, 2007). These parameters are (1) the efficiency γ of the conversion of wind power into the buoyancy power that controls the rate of change of the available potential energy (APE) in the ocean and (2) the e-folding rate α that characterizes the damping of APE by turbulent diffusion and other processes. Estimating these two parameters for coupled models reveals potential deficiencies (and large differences) in how state-of-the-art coupled GCMs reproduce the ocean energetics as compared to ocean-only models and data assimilating models. The majority of the coupled models we analyzed show a lower efficiency (values of γ in the range of 10-50% versus 50-60% for ocean-only simulations or reanalysis) and a relatively strong energy damping (values of α-1 in the range 0.4-1 years versus 0.9-1.2 years). These differences in the model energetics appear to reflect differences in the simulated thermal structure of the tropical ocean, the structure of ocean equatorial currents, and deficiencies in the way coupled models simulate ENSO.

  3. Simulated impacts of afforestation in East China monsoon region as modulated by ocean variability

    NASA Astrophysics Data System (ADS)

    Ma, Di; Notaro, Michael; Liu, Zhengyu; Chen, Guangshan; Liu, Yongqiang

    2013-11-01

    Using the National Center for Atmospheric Research Community Climate System Model Version 3.5, this paper examines the climatic effects of afforestation in the East China monsoon region with a focus on land-atmosphere interactions and the modulating influence of ocean variability. In response to afforestation, the local surface air temperature significantly decreases in summer and increases in winter. The summer cooling is attributed to enhanced evapotranspiration from increased tree cover. During winter, afforestation induces greater roughness and weaker winds over the adjacent coastal ocean, leading to diminished latent heat flux and increased sea-surface temperature (SST). The enhanced SST supports greater atmospheric water vapor, which is accompanied by anomalous wind, and transported into the East China monsoon region. The increase in atmospheric water vapor favors more cloud cover and precipitation, especially in the eastern afforestation region. Furthermore, the increase in atmospheric water vapor and cloud cover produce a greenhouse effect, raising the wintertime surface air temperature. By comparing simulations in which ocean temperature are either fixed or variable, we demonstrate that a significant hydrologic response in East China to afforestation only occurs if ocean temperatures are allowed to vary and the oceanic source of moisture to the continent is enhanced.

  4. An update on modeling land-ice/ocean interactions in CESM

    SciTech Connect

    Asay-davis, Xylar

    2011-01-24

    This talk is an update on ongoing land-ice/ocean coupling work within the Community Earth System Model (CESM). The coupling method is designed to allow simulation of a fully dynamic ice/ocean interface, while requiring minimal modification to the existing ocean model (the Parallel Ocean Program, POP). The method makes use of an immersed boundary method (IBM) to represent the geometry of the ice-ocean interface without requiring that the computational grid be modified in time. We show many of the remaining development challenges that need to be addressed in order to perform global, century long climate runs with fully coupled ocean and ice sheet models. These challenges include moving to a new grid where the computational pole is no longer at the true south pole and several changes to the coupler (the software tool used to communicate between model components) to allow the boundary between land and ocean to vary in time. We discuss benefits for ice/ocean coupling that would be gained from longer-term ocean model development to allow for natural salt fluxes (which conserve both water and salt mass, rather than water volume).

  5. Laboratory Simulations of Ammonia-Rich Oceans in Icy Worlds

    NASA Technical Reports Server (NTRS)

    Vance, S. D.; Brown, J. M.

    2011-01-01

    Improved equations of state for ammonia-water solutions are important for properly understanding the interiors of large icy satellites hosting deep interior oceans. Titan is the primary example of such a world, but water-rich dwarf planets Measurements of solution density are now possible at relevant pressures (above approx. 250 megapascals) using the Simulator for Icy World Interiors. Analysis of sound velocity measurements in aqueous magnesium sulfate obtained in our laboratory, shows a correction on the order of 5% to 700 megapascals (7 kilobar) from -20 to 100 C and to 3 m (approx. 30 percentage by weight) concentration. Accurate prediction of density as a function of pressure, temperature, and ammonia concentration are needed for interpretation of remote observations to address questions of interior liquid layer depth, composition, and fluid dynamics.

  6. An assessment of a software simulation tool for lidar atmosphere and ocean measurements

    NASA Astrophysics Data System (ADS)

    Powell, K. A.; Vaughan, M.; Burton, S. P.; Hair, J. W.; Hostetler, C. A.; Kowch, R. S.

    2014-12-01

    A high-fidelity lidar simulation tool is used to generate synthetic lidar backscatter data that closely matches the expected performance of various lidars, including the noise characteristics inherent to analog detection and uncertainties related to the measurement environment. This tool supports performance trade studies and scientific investigations for both the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which flies aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL). CALIOP measures profiles of attenuated backscatter coefficients (532 and 1064 nm) and volume depolarization ratios at 532 nm. HSRL measures the same profiles plus volume depolarization at 1064 nm and a molecular-only profile which allows for the direct retrieval of aerosol extinction and backscatter profiles at 532 nm. The simulation tool models both the fundamental physics of the lidar instruments and the signals generated from aerosols, clouds, and the ocean surface and subsurface. This work presents the results of a study conducted to verify the accuracy of the simulated data using data from both HSRL and CALIOP. The tool was tuned to CALIOP instrument settings and the model atmosphere was defined using profiles of attenuated backscatter and depolarization obtained by HSRL during underflights of CALIPSO. The validated HSRL data provide highly accurate measurements of the particulate intensive and extensive optical properties and thus were considered as the truth atmosphere. The resulting simulated data were processed through the CALIPSO data analysis system. Comparisons showed good agreement between the simulated and CALIOP data. This verifies the accuracy of the tool to support studies involving the characterization of instrument components and advanced data analysis techniques. The capability of the tool to simulate ocean surface scattering and subsurface

  7. Model Calculations of Ocean Acidification at the End Cretaceous

    NASA Astrophysics Data System (ADS)

    Tyrrell, T.; Merico, A.; Armstrong McKay, D. I.

    2014-12-01

    Most episodes of ocean acidification (OA) in Earth's past were either too slow or too minor to provide useful lessons for understanding the present. The end-Cretaceous event (66 Mya) is special in this sense, both because of its rapid onset and also because many calcifying species (including 100% of ammonites and >95% of calcareous nannoplankton and planktonic foraminifera) went extinct at this time. We used box models of the ocean carbon cycle to evaluate whether impact-generated OA could feasibly have been responsible for the calcifier mass extinctions. We simulated several proposed consequences of the asteroid impact: (1) vaporisation of gypsum (CaSO4) and carbonate (CaCO3) rocks at the point of impact, producing sulphuric acid and CO2 respectively; (2) generation of NOx by the impact pressure wave and other sources, producing nitric acid; (3) release of CO2 from wildfires, biomass decay and disinterring of fossil organic carbon and hydrocarbons; and (4) ocean stirring leading to introduction into the surface layer of deep water with elevated CO2. We simulated additions over: (A) a few years (e-folding time of 6 months), and also (B) a few days (e-folding time of 10 hours) for SO4 and NOx, as recently proposed by Ohno et al (2014. Nature Geoscience, 7:279-282). Sulphuric acid as a consequence of gypsum vaporisation was found to be the most important acidifying process. Results will also be presented of the amounts of SO4 required to make the surface ocean become extremely undersaturated (Ωcalcite<0.5) for different e-folding times and combinations of processes. These will be compared to estimates in the literature of how much SO4 was actually released.

  8. Global Ocean Reanalysis Simulations at Mercator Océan GLORYS1: the Argo years 2002-2008

    NASA Astrophysics Data System (ADS)

    Drevillon, M.; Parent, L.; Ferry, N.; Greiner, E.; Barnier, B.

    2009-12-01

    Since a decade ago, Mercator Océan develops and operates different ocean forecasting systems based on OGCM models and advanced data assimilation schemes using in situ and remotely sensed data. In the framework of the European GMES MyOcean project (FP7, 2009-2011), Mercator Océan will become a main contributor for the delivery of regular and systematic information to intermediate users & downstream service provider. Conjointly to this operational activity, the generation of global reanalysis simulations is a growing priority to satisfy scientist demands for climate studies. During this presentation, we will expose the results of the first global eddy-permitting (1/4°) ocean reanalysis simulation performed by Mercator Océan. It covers the 2002-2008 time period, which benefits from the ARGO float measurements. This significant improvement of the Global Ocean Observing System tends to indicate that the last decade is the primary test bed period for the development and the validation of any ocean reanalysis system. The “reanalysis system” is based on the current operational global ocean forecasting system, available since April 2008: the ocean and sea ice model NEMO is coupled with the SAM2 (Système d'Assimilation Mercator V2) data assimilation system, a reduced order extended Kalman filter with the capability to manage various and high number of observations and specially designed for expensive configurations. Dedicated altimetry database (from CLS) and in situ database (from CORIOLIS data center / Ifremer) have been used for the integration of this reanalysis simulation and the temporal continuity is assured by the IAU (Incremental Analysis Updates) method. An overall assessment of this reanalysis simulation will be given, with its strengths, its limitations and its necessary update in order to obtain a better depiction of the ocean state along the 2000's or the Altimetry years (1992-today). contact:lparent@mercator-ocean.fr

  9. Numerical noise in ocean and estuarine models

    USGS Publications Warehouse

    Walters, R.; Carey, G.F.

    1984-01-01

    Approximate methods for solving the shallow water equations may lead to solutions exhibiting large fictitious, numerically-induced oscillations. The analysis of the discrete dispersion relation and modal solutions of small wavelengths provides a powerful technique for assessing the sensitivity of alternative numerical schemes to irregular data which may lead to such oscillatory numerical noise. For those schemes where phase speed vanishes at a finite wavenumber or there are multiple roots for wavenumber, oscillation modes can exist which are uncoupled from the dynamics of the problem. The discrete modal analysis approach is used here to identify two classes of spurious oscillation modes associated respectively with the two different asymptotic limits corresponding to estuarine and large scale ocean models. The analysis provides further insight into recent numerical results for models which include large spatial scales and Coriolis acceleration. ?? 1984.

  10. Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the Regional Ocean Modeling System

    USGS Publications Warehouse

    Haidvogel, D.B.; Arango, H.; Budgell, W.P.; Cornuelle, B.D.; Curchitser, E.; Di, Lorenzo E.; Fennel, K.; Geyer, W.R.; Hermann, A.J.; Lanerolle, L.; Levin, J.; McWilliams, J.C.; Miller, A.J.; Moore, A.M.; Powell, T.M.; Shchepetkin, A.F.; Sherwood, C.R.; Signell, R.P.; Warner, J.C.; Wilkin, J.

    2008-01-01

    Systematic improvements in algorithmic design of regional ocean circulation models have led to significant enhancement in simulation ability across a wide range of space/time scales and marine system types. As an example, we briefly review the Regional Ocean Modeling System, a member of a general class of three-dimensional, free-surface, terrain-following numerical models. Noteworthy characteristics of the ROMS computational kernel include: consistent temporal averaging of the barotropic mode to guarantee both exact conservation and constancy preservation properties for tracers; redefined barotropic pressure-gradient terms to account for local variations in the density field; vertical interpolation performed using conservative parabolic splines; and higher-order, quasi-monotone advection algorithms. Examples of quantitative skill assessment are shown for a tidally driven estuary, an ice-covered high-latitude sea, a wind- and buoyancy-forced continental shelf, and a mid-latitude ocean basin. The combination of moderate-order spatial approximations, enhanced conservation properties, and quasi-monotone advection produces both more robust and accurate, and less diffusive, solutions than those produced in earlier terrain-following ocean models. Together with advanced methods of data assimilation and novel observing system technologies, these capabilities constitute the necessary ingredients for multi-purpose regional ocean prediction systems. ?? 2007 Elsevier Inc. All rights reserved.

  11. Feature Analysis of Ocean Waves in North Central Pacific Ocean Based ASAR Wave Spectral Data and Wave Model

    NASA Astrophysics Data System (ADS)

    Wang, Jichao; Zhang, Jie; Yang, Jungang; Meng, Junmin

    2013-01-01

    Directional Spectrum of the ocean waves could be obtained form Envisat advanced synthetic aperture radar (ASAR) wave spectral data. The wave model WAVEWATCH III (WW3) is applied to simulate the ocean wave field. Study area is 185°E-215°E and 15°N-30°N, time range is from 1 January 2008 to 31 December 2008. Based on ASAR and buoy data, the wave numerical simulation and assimilation of the north central Pacific Ocean is carried out. The validation and assessment of ASAR ocean wave spectra products is performed. The optimal interpolation (OI) algorithm is used in model WW3 for assimilating ASAR wave spectra data. Based on the result of the simulation and assimilation, mean waves direction (MWD), significant wave height (SWH) and mean wave period (MWP) are analysed. SWH and MWP are larger in winter and SWH reach to more than 2.5 meters. Seasonal change of SWH and MWP are significant.

  12. Development of the Southern Ocean Climate Model Atlas

    NASA Astrophysics Data System (ADS)

    Rudd, J.; Russell, J. L.; Goodman, P. J.

    2014-12-01

    The development of consistent, observationally-based metrics, by which to assess the fidelity of a model simulation is being undertaken by many modelers and modeling groups. A "Southern Ocean Climate Model Atlas" is under construction that will house the results of these various analyses and will provide access for fellow scientists, stakeholders, resource managers and the public to the latest projections of climate and climate change from all of the available climate models. This Atlas will allow a visual comparison of simulated fields, differences and errors and will include quantification of the errors where the observations permit. It will also include the scripts required for anyone to create a comparable map with their own data/output. We will discuss the creation of observationally-based metrics and some of the challenges associated with the consistent quantification of simulations errors and inter-model differences. We will also present some of the commonly assessed variables (e.g. temperature, winds, ice, pH) useful to climate scientists, ecosystem scientists and the general public.

  13. Upscalling processes in an ocean-atmosphere multiscale coupled model

    NASA Astrophysics Data System (ADS)

    Masson, S. G.; Berthet, S.; Samson, G.; Crétat, J.; Colas, F.; Echevin, V.; Jullien, S.; Hourdin, C.

    2015-12-01

    This work explores new pathways toward a better representation of the multi-scale physics that drive climate variability. We are analysing the key upscaling processes by which small-scale localized errors have a knock-on effect onto global climate. We focus on the Peru-Chilli coastal upwelling, an area known to hold among the strongest models biases in the Tropics. Our approach is based on the development of a multiscale coupling interface allowing us to couple WRF with the NEMO oceanic model in a configuration including 2-way nested zooms in the oceanic and/or the atmospheric component of the coupled model. Upscalling processes are evidenced and quantified by comparing three 20-year long simulations of a tropical channel (45°S-45°N), which differ by their horizontal resolution: 0.75° everywhere, 0.75°+0.25° zoom in the southeastern Pacific or 0.25° everywhere. This set of three 20-year long simulations was repeated with 3 different sets of parameterizations to assess the robustness of our results. Our results show that adding an embedded zoom over the southeastern Pacific only in the atmosphere cools down the SST along the Peru-Chili coast, which is a clear improvement. This change is associated with a displacement of the low-level cloud cover, which moves closer to the coast cooling further the coastal area SST. Offshore, we observe the opposite effect with a reduction of the cloud cover with higher resolution, which increases solar radiation and warms the SST. Increasing the resolution in the oceanic component show contrasting results according to the different set parameterization used in the experiments. Some experiment shows a coastal cooling as expected, whereas, in other cases, we observe a counterintuitive response with a warming of the coastal SST. Using at the same time an oceanic and an atmospheric zoom mostly combines the results obtained when using the 2-way nesting in only one component of the coupled model. In the best case, we archive by this

  14. Sensitivity of a climatologically-driven sea ice model to the ocean heat flux

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Good, M. R.

    1982-01-01

    Ocean heat flux sensitivity was studied on a numerical model of sea ice covering the Weddell Sea region of the southern ocean. The model is driven by mean monthly climatological atmospheric variables. For each model run, the ocean heat flux is uniform in both space and time. Ocean heat fluxes below 20 W m to the minus 2 power do not provide sufficient energy to allow the ice to melt to its summertime thicknesses and concentrations by the end of the 14 month simulation, whereas ocean heat fluxes of 30 W m to the minus 2 power and above result in too much ice melt, producing the almost total disappearance of ice in the Weddell Sea by the end of the 14 months. These results are dependent on the atmospheric forcing fields.

  15. Natural Ocean Carbon Cycle Sensitivity to Parameterizations of the Recycling in a Climate Model

    NASA Technical Reports Server (NTRS)

    Romanou, A.; Romanski, J.; Gregg, W. W.

    2014-01-01

    Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10 %) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12-34 %, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which

  16. Tracking the long-distance dispersal of marine organisms: sensitivity to ocean model resolution.

    PubMed

    Putman, Nathan F; He, Ruoying

    2013-04-01

    Ocean circulation models are widely used to simulate organism transport in the open sea, where challenges of directly tracking organisms across vast spatial and temporal scales are daunting. Many recent studies tout the use of 'high-resolution' models, which are forced with atmospheric data on the scale of several hours and integrated with a time step of several minutes or seconds. However, in many cases, the model's outputs that are used to simulate organism movement have been averaged to considerably coarser resolutions (e.g. monthly mean velocity fields). To examine the sensitivity of tracking results to ocean circulation model output resolution, we took the native model output of one of the most sophisticated ocean circulation models available, the Global Hybrid Coordinate Ocean Model, and averaged it to commonly implemented spatial and temporal resolutions in studies of basin-scale dispersal. Comparisons between simulated particle trajectories and in situ near-surface drifter trajectories indicated that 'over averaging' model output yields predictions inconsistent with observations. Further analyses focused on the dispersal of juvenile sea turtles indicate that very different inferences regarding the pelagic ecology of these animals are obtained depending on the resolution of model output. We conclude that physical processes occurring at the scale of days and tens of kilometres should be preserved in ocean circulation model output to realistically depict the movement marine organisms and the resulting ecological and evolutionary processes.

  17. Radiative Transfer Simulations of the Two-Dimensional Ocean Glint Reflectance and Determination of the Sea Surface Roughness

    NASA Technical Reports Server (NTRS)

    Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

    2016-01-01

    An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

  18. Adaptive wavelet simulation of global ocean dynamics using a new Brinkman volume penalization

    NASA Astrophysics Data System (ADS)

    Kevlahan, N. K.-R.; Dubos, T.; Aechtner, M.

    2015-12-01

    In order to easily enforce solid-wall boundary conditions in the presence of complex coastlines, we propose a new mass and energy conserving Brinkman penalization for the rotating shallow water equations. This penalization does not lead to higher wave speeds in the solid region. The error estimates for the penalization are derived analytically and verified numerically for linearized one-dimensional equations. The penalization is implemented in a conservative dynamically adaptive wavelet method for the rotating shallow water equations on the sphere with bathymetry and coastline data from NOAA's ETOPO1 database. This code could form the dynamical core for a future global ocean model. The potential of the dynamically adaptive ocean model is illustrated by using it to simulate the 2004 Indonesian tsunami and wind-driven gyres.

  19. Ocean Models and Proper Orthogonal Decomposition

    NASA Astrophysics Data System (ADS)

    Salas-de-Leon, D. A.

    2007-05-01

    The increasing computational developments and the better understanding of mathematical and physical systems resulted in an increasing number of ocean models. Long time ago, modelers were like a secret organization and recognize each other by using secret codes and languages that only a select group of people was able to recognize and understand. The access to computational systems was reduced, on one hand equipment and the using time of computers were expensive and restricted, and on the other hand, they required an advance computational languages that not everybody wanted to learn. Now a days most college freshman own a personal computer (PC or laptop), and/or have access to more sophisticated computational systems than those available for research in the early 80's. The resource availability resulted in a mayor access to all kind models. Today computer speed and time and the algorithms does not seem to be a problem, even though some models take days to run in small computational systems. Almost every oceanographic institution has their own model, what is more, in the same institution from one office to the next there are different models for the same phenomena, developed by different research member, the results does not differ substantially since the equations are the same, and the solving algorithms are similar. The algorithms and the grids, constructed with algorithms, can be found in text books and/or over the internet. Every year more sophisticated models are constructed. The Proper Orthogonal Decomposition is a technique that allows the reduction of the number of variables to solve keeping the model properties, for which it can be a very useful tool in diminishing the processes that have to be solved using "small" computational systems, making sophisticated models available for a greater community.

  20. Application of a Topological Metric for Assessing Numerical Ocean Models with Satellite Observations

    NASA Astrophysics Data System (ADS)

    Morey, S. L.; Dukhovskoy, D. S.; Hiester, H. R.; Garcia-Pineda, O. G.; MacDonald, I. R.

    2015-12-01

    Satellite-based sensors provide a vast amount of observational data over the world ocean. Active microwave radars measure changes in sea surface height and backscattering from surface waves. Data from passive radiometers sensing emissions in multiple spectral bands can directly measure surface temperature, be combined with other data sources to estimate salinity, or processed to derive estimates of optically significant quantities, such as concentrations of biochemical properties. Estimates of the hydrographic variables can be readily used for assimilation or assessment of hydrodynamic ocean models. Optical data, however, have been underutilized in ocean circulation modeling. Qualitative assessments of oceanic fronts and other features commonly associated with changes in optically significant quantities are often made through visual comparison. This project applies a topological approach, borrowed from the field of computer image recognition, to quantitatively evaluate ocean model simulations of features that are related to quantities inferred from satellite imagery. The Modified Hausdorff Distance (MHD) provides a measure of the similarity of two shapes. Examples of applications of the MHD to assess ocean circulation models are presented. The first application assesses several models' representation of the freshwater plume structure from the Mississippi River, which is associated with a significant expression of color, using a satellite-derived ocean color index. Even though the variables being compared (salinity and ocean color index) differ, the MHD allows contours of the fields to be compared topologically. The second application assesses simulations of surface oil transport driven by winds and ocean model currents using surface oil maps derived from synthetic aperture radar backscatter data. In this case, maps of time composited oil coverage are compared between the simulations and satellite observations.

  1. Modeling of ocean wave effects for LIDAR remote sensing

    NASA Astrophysics Data System (ADS)

    McLean, John W.

    1990-09-01

    A simulation nodel is described which generates realizations of the LIDAR return from a wind roughened ocean, including both surface specular and subsurface volumetric returns. The physical model includes representations for the two dimensional wavy surface (gravity waves), beam spread at the interface due to small scale roughness (capillary waves), and beam spread and attenuation due to multiple scattering and absorption in the water. The sensor model allows for arbitrary incidence angles, transmitter divergences, and receiver fields of view. From ensembles of realizations, the statistical characteristics of the surface wave induced fluctuations are determined, such as profiles of variance versus depth, and spatial/temporal correlations of the returns. Model results are compared with experimental data on specular return statistics and downwelling irradiance fluctuations. Predictions are presented for the round trip LIDAR fluctuations induced by surface waves.

  2. Decadal-Scale Response of the Antarctic Ice sheet to a Warming Ocean using the POPSICLES Coupled Ice Sheet-Ocean model

    NASA Astrophysics Data System (ADS)

    Martin, D. F.; Asay-Davis, X.; Cornford, S. L.; Price, S. F.; Ng, E. G.; Collins, W.

    2015-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period from 1990 to 2010. We use the CORE v. 2 interannual forcing data to force the ocean model. Simulations are performed at 0.1o(~5 km) ocean resolution with adaptive ice sheet resolution as fine as 500 m to adequately resolve the grounding line dynamics. We discuss the effect of improved ocean mixing and subshelf bathymetry (vs. the standard Bedmap2 bathymetry) on the behavior of the coupled system, comparing time-averaged melt rates below a number of major ice shelves with those reported in the literature. We also present seasonal variability and decadal melting trends from several Antarctic regions, along with the response of the ice shelves and the consequent dynamic response of the grounded ice sheet.POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program, and the BISICLES ice-sheet model. POP2x includes sub-ice-shelf circulation using partial top cells and the commonly used three-equation boundary layer physics. Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP) and other continental-scale simulations and melt-rate observations. BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3d) and realistic configurations.The figure shows the BISICLES-computed vertically-integrated grounded ice velocity field 5 years into a 20-year coupled full-continent Antarctic-Southern-Ocean simulation. Submarine melt rates are painted onto the surface of the floating ice shelves. Grounding lines are shown in green.

  3. Modeling ocean wave propagation under sea ice covers

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Shen, Hayley H.; Cheng, Sukun

    2015-02-01

    Operational ocean wave models need to work globally, yet current ocean wave models can only treat ice-covered regions crudely. The purpose of this paper is to provide a brief overview of ice effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea ice can be classified as: landfast ice zone, shear zone, and the marginal ice zone. All ice covers attenuate wave energy. Only long swells can penetrate deep into an ice cover. Being closest to open water, wave propagation in the marginal ice zone is the most complex to model. The physical appearance of sea ice in the marginal ice zone varies. Grease ice, pancake ice, brash ice, floe aggregates, and continuous ice sheet may be found in this zone at different times and locations. These types of ice are formed under different thermal-mechanical forcing. There are three classic models that describe wave propagation through an idealized ice cover: mass loading, thin elastic plate, and viscous layer models. From physical arguments we may conjecture that mass loading model is suitable for disjoint aggregates of ice floes much smaller than the wavelength, thin elastic plate model is suitable for a continuous ice sheet, and the viscous layer model is suitable for grease ice. For different sea ice types we may need different wave ice interaction models. A recently proposed viscoelastic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various ice covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea ice types, previous wave ice interaction models, wave attenuation mechanisms, the methods to calculate wave reflection and transmission between different ice covers, and the effect of ice floe breaking on shaping the sea ice morphology

  4. Numerical simulation of small-scale mixing processes in the upper ocean and atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Druzhinin, O.; Troitskaya, Yu; Zilitinkevich, S.

    2016-02-01

    The processes of turbulent mixing and momentum and heat exchange occur in the upper ocean at depths up to several dozens of meters and in the atmospheric boundary layer within interval of millimeters to dozens of meters and can not be resolved by known large- scale climate models. Thus small-scale processes need to be parameterized with respect to large scale fields. This parameterization involves the so-called bulk coefficients which relate turbulent fluxes with large-scale fields gradients. The bulk coefficients are dependent on the properties of the small-scale mixing processes which are affected by the upper-ocean stratification and characteristics of surface and internal waves. These dependencies are not well understood at present and need to be clarified. We employ Direct Numerical Simulation (DNS) as a research tool which resolves all relevant flow scales and does not require closure assumptions typical of Large-Eddy and Reynolds Averaged Navier-Stokes simulations (LES and RANS). Thus DNS provides a solid ground for correct parameterization of small-scale mixing processes and also can be used for improving LES and RANS closure models. In particular, we discuss the problems of the interaction between small-scale turbulence and internal gravity waves propagating in the pycnocline in the upper ocean as well as the impact of surface waves on the properties of atmospheric boundary layer over wavy water surface.

  5. Global Ocean Reanalysis Simulations at Mercator Océan GLORYS1: the Argo years 2002-2008

    NASA Astrophysics Data System (ADS)

    Parent, L.; Ferry, N.; Barnier, B.; Drevillon, M.; Greiner, E.

    2009-04-01

    Since a decade ago, Mercator Océan develops and operates different ocean forecasting systems based on OGCM models and advanced data assimilation schemes using in situ and remotely sensed data. In the framework of the European GMES MyOcean project (FP7, 2009-2011), Mercator Océan will become a main contributor for the delivery of regular and systematic information to intermediate users & downstream service provider. Conjointly to this operational activity, the generation of global reanalysis simulations is a growing priority to satisfy scientist demands for climate studies. During this presentation, we will expose the results of the first global eddy-permitting (1/4°) ocean reanalysis simulation performed by Mercator Océan. It covers the 2002-2008 time period, which benefits from the ARGO float measurements. This significant improvement of the Global Ocean Observing System tends to indicate that the last decade is the primary test bed period for the development and the validation of any ocean reanalysis system. The "reanalysis system" is based on the current operational global ocean forecasting system, available since April 2008: the ocean and sea ice model NEMO is coupled with the SAM2 (Système d'Assimilation Mercator V2) data assimilation system, a reduced order extended Kalman filter with the capability to manage various and high number of observations and specially designed for expensive configurations. Dedicated altimetry database (from CLS) and in situ database (from CORIOLIS data center / Ifremer) have been used for the integration of this reanalysis simulation and the temporal continuity is assured by the IAU (Incremental Analysis Updates) method. An overall assessment of this reanalysis simulation will be given, with its strengths, its limitations and its necessary update in order to obtain a better depiction of the ocean state along the 2000's or the Altimetry years (1992-today).

  6. Global Ocean Reanalysis Simulations at Mercator Océan GLORYS1: the Argo years 2002-2009

    NASA Astrophysics Data System (ADS)

    Parent, Laurent; Ferry, Nicolas; Barnier, Bernard; Drevillon, Marie; Greiner, Eric

    2010-05-01

    Since a decade ago, Mercator Océan develops and operates different ocean forecasting systems based on OGCM models and advanced data assimilation schemes using in situ and remotely sensed data. In the framework of the European GMES MyOcean project (FP7, 2009-2011), Mercator Océan will become a main contributor for the delivery of regular and systematic information to intermediate users & downstream service provider. Conjointly to this operational activity, the generation of global reanalysis simulations is a growing priority to satisfy scientist demands for climate studies. During this presentation, we will expose the results of the first global eddy-permitting (1/4°) ocean reanalysis simulation performed by Mercator Océan. It covers the 2002-2009 time period, which benefits from the ARGO float measurements. This significant improvement of the Global Ocean Observing System tends to indicate that the last decade is the primary test bed period for the development and the validation of any ocean reanalysis system. The "reanalysis system" is based on the current operational global ocean forecasting system, available since April 2008: the ocean and sea ice model NEMO is coupled with the SAM2 (Système d'Assimilation Mercator V2) data assimilation system, a reduced order extended Kalman filter with the capability to manage various and high number of observations and specially designed for expensive configurations. Dedicated altimetry database (from CLS) and in situ database (from CORIOLIS data center / Ifremer) have been used for the integration of this reanalysis simulation and the temporal continuity is assured by the IAU (Incremental Analysis Updates) method. An overall assessment of this reanalysis simulation will be given, with its strengths, its limitations and its necessary update in order to obtain a better depiction of the ocean state along the 2000's or the Altimetry years (1992-today).

  7. Gyrokinetic particle simulation model

    SciTech Connect

    Lee, W.W.

    1986-07-01

    A new type of particle simulation model based on the gyrophase-averaged Vlasov and Poisson equations is presented. The reduced system, in which particle gyrations are removed from the equations of motion while the finite Larmor radius effects are still preserved, is most suitable for studying low frequency microinstabilities in magnetized plasmas. It is feasible to simulate an elongated system (L/sub parallel/ >> L/sub perpendicular/) with a three-dimensional grid using the present model without resorting to the usual mode expansion technique, since there is essentially no restriction on the size of ..delta..x/sub parallel/ in a gyrokinetic plasma. The new approach also enables us to further separate the time and spatial scales of the simulation from those associated with global transport through the use of multiple spatial scale expansion. Thus, the model can be a very efficient tool for studying anomalous transport problems related to steady-state drift-wave turbulence in magnetic confinement devices. It can also be applied to other areas of plasma physics.

  8. A coastal ocean model with subgrid approximation

    NASA Astrophysics Data System (ADS)

    Walters, Roy A.

    2016-06-01

    A wide variety of coastal ocean models exist, each having attributes that reflect specific application areas. The model presented here is based on finite element methods with unstructured grids containing triangular and quadrilateral elements. The model optimizes robustness, accuracy, and efficiency by using semi-implicit methods in time in order to remove the most restrictive stability constraints, by using a semi-Lagrangian advection approximation to remove Courant number constraints, and by solving a wave equation at the discrete level for enhanced efficiency. An added feature is the approximation of the effects of subgrid objects. Here, the Reynolds-averaged Navier-Stokes equations and the incompressibility constraint are volume averaged over one or more computational cells. This procedure gives rise to new terms which must be approximated as a closure problem. A study of tidal power generation is presented as an example of this method. A problem that arises is specifying appropriate thrust and power coefficients for the volume averaged velocity when they are usually referenced to free stream velocity. A new contribution here is the evaluation of three approaches to this problem: an iteration procedure and two mapping formulations. All three sets of results for thrust (form drag) and power are in reasonable agreement.

  9. Diurnal ocean surface layer model validation

    NASA Technical Reports Server (NTRS)

    Hawkins, Jeffrey D.; May, Douglas A.; Abell, Fred, Jr.

    1990-01-01

    The diurnal ocean surface layer (DOSL) model at the Fleet Numerical Oceanography Center forecasts the 24-hour change in a global sea surface temperatures (SST). Validating the DOSL model is a difficult task due to the huge areas involved and the lack of in situ measurements. Therefore, this report details the use of satellite infrared multichannel SST imagery to provide day and night SSTs that can be directly compared to DOSL products. This water-vapor-corrected imagery has the advantages of high thermal sensitivity (0.12 C), large synoptic coverage (nearly 3000 km across), and high spatial resolution that enables diurnal heating events to be readily located and mapped. Several case studies in the subtropical North Atlantic readily show that DOSL results during extreme heating periods agree very well with satellite-imagery-derived values in terms of the pattern of diurnal warming. The low wind and cloud-free conditions necessary for these events to occur lend themselves well to observation via infrared imagery. Thus, the normally cloud-limited aspects of satellite imagery do not come into play for these particular environmental conditions. The fact that the DOSL model does well in extreme events is beneficial from the standpoint that these cases can be associated with the destruction of the surface acoustic duct. This so-called afternoon effect happens as the afternoon warming of the mixed layer disrupts the sound channel and the propagation of acoustic energy.

  10. On the influence of ocean waves on simulated GNSS-R delay-doppler maps

    NASA Astrophysics Data System (ADS)

    Clarizia, M. P.; di Bisceglie, M.; Galdi, C.; Gommenginger, C.; Srokosz, M.

    2012-04-01

    Global Navigation Satellite System-Reflectometry (GNSS-R), is an established technique that exploits GNSS signals of opportunity reflected from the surface of the ocean, to look primarily at the ocean surface roughness. The strength of this technique, and the primary motivation to carry it forward, is in the fact that GNSS signals are available globally, all the time and over the long term, and could help dramatically improve the monitoring of ocean wind and waves. GNSS-R offers the prospect of high density global measurements of directional sea surface roughness, which are essential for scientific purposes (i.e. quantifying the air-sea exchanges of gases), operational weather and ocean forecasting (i.e. prediction of high winds, dangerous sea states, risk of flooding and storm surges) and to support important climate-relevant Earth Observation techniques (IR SST, or surface salinity retrieval). The retrieval of ocean roughness from GNSS-R data has now been demonstrated with a reasonable level of accuracy from both airborne [1] and spaceborne [2] platforms. In both cases, Directional Mean Square Slopes (DMSS) of the ocean surface have been retrieved from GNSS-R data, in the form of Delay-Doppler Maps (DDMs), using an established theoretical scattering model by Zavorotny and Voronovich (Z-V) [3]. The need for a better assessment of the way the ocean waves influence the scattering of GPS signals has recently led to a different approach, consisting of simulating the scattering of such signals, using a more sophisticated large-scale scattering model than Z-V, and explicit simulations of realistic seas. Initial results produced from these simulations have been recently published in [4], where the emphasis has been put on the effects of different sea states on Radar Cross Section (RCS) and Polarization Ratio (PR) in space domain. Linear wind wave surfaces have been simulated using the Elfouhaily wind wave spectrum [5], for different wind speeds and directions, and with

  11. Sensitivity study of subgrid scale ocean mixing under sea ice using a two-column ocean grid in climate model CESM

    NASA Astrophysics Data System (ADS)

    Jin, Meibing; Hutchings, Jennifer; Kawaguchi, Yusuke

    2015-12-01

    Brine drainage from sea ice formation plays a critical role in ocean mixing and seasonal variations of halocline in polar oceans. The horizontal scale of brine drainage and its induced convection is much smaller than a climate model grid and a model tends to produce false ocean mixing when brine drainage is averaged over a grid cell. A two-column ocean grid (TCOG) scheme was implemented in the Community Earth System Model (CESM) using coupled sea ice-ocean model setting to explicitly solve the different vertical mixing in the two sub-columns of one model grid with and without brine rejection. The fraction of grid with brine rejection was tested to be equal to the lead fraction or a small constant number in a series of sensitivity model runs forced by the same atmospheric data from 1978 to 2009. The model results were compared to observations from 29 ice tethered profilers (ITP) in the Arctic Ocean Basin from 2004 to 2009. Compared with the control run using a regular ocean grid, the TCOG simulations showed consistent reduction of model errors in salinity and mixed layer depth (MLD). The model using a small constant fraction grid for brine rejection was found to produce the best model comparison with observations, indicating that the horizontal scale of the brine drainage is very small compared to the sea ice cover and even smaller than the lead fraction. Comparable to models using brine rejection parameterization schemes, TCOG achieved more improvements in salinity but similar in MLD.

  12. Finding the driver of local ocean-atmosphere coupling in reanalyses and CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Ruiz-Barradas, Alfredo; Kalnay, Eugenia; Peña, Malaquías; BozorgMagham, Amir E.; Motesharrei, Safa

    2016-06-01

    Identification of the driver of coupled anomalies in the climate system is of great importance for a better understanding of the system and for its use in predictive efforts with climate models. The present analysis examines the robustness of a physical method proposed three decades ago to identify coupled anomalies as of atmospheric or oceanic origin by analyzing 850 mb vorticity and sea surface temperature anomalies. The method is then used as a metric to assess the coupling in climate simulations and a 30-year hindcast from models of the CMIP5 project. Analysis of the frequency of coupled anomalies exceeding one standard deviation from uncoupled NCEP/NCAR and ERA-Interim and partially coupled CFSR reanalyses shows robustness in the main results: anomalies of oceanic origin arise inside the deep tropics and those of atmospheric origin outside of the tropics. Coupled anomalies occupy similar regions in the global oceans independently of the spatiotemporal resolution. Exclusion of phenomena like ENSO, NAO, or AMO has regional effects on the distribution and origin of coupled anomalies; the absence of ENSO decreases anomalies of oceanic origin and favors those of atmospheric origin. Coupled model simulations in general agree with the distribution of anomalies of atmospheric and oceanic origin from reanalyses. However, the lack of the feedback from the atmosphere to the ocean in the AMIP simulations reduces substantially the number of coupled anomalies of atmospheric origin and artificially increases it in the tropics while the number of those of oceanic origin outside the tropics is also augmented. Analysis of a single available 30-year hindcast surprisingly indicates that coupled anomalies are more similar to AMIP than to coupled simulations. Differences in the frequency of coupled anomalies between the AMIP simulations and the uncoupled reanalyses, and similarities between the uncoupled and partially coupled reanalyses, support the notion that the nature of the

  13. Three-dimensional simulations of atmospheric methyl chloroform - Effect of an ocean sink

    NASA Technical Reports Server (NTRS)

    Tie, X.; Kao, C.-Y.; Mroz, E. J.; Cicerone, R. J.; Alyea, F. N.; Cunnold, D. M.

    1992-01-01

    A global three-dimensional chemical tracer model of the distribution and seasonal cycles of the surface concentration of CH3CCl3 is compared with surface observations from the Atmospheric Lifetime Experiment (ALE) for the years 1980-1985. Two-dimensional OH distributions calculated by a photochemical model are empirically adjusted from observed trends in the global average and the interhemispheric ratio of methyl chloroform. The effects of the recently discovered ocean sink for methyl chloroform were investigated. The model simulates the 5-year record of observations made at the five ALE sampling sites to generally within +/- 5 percent of the observed mean. The calculated average global lifetime of methyl chloroform is 5.7 +/- 0.3 years. The estimated global mean OH concentration is 6.5 +/- 0.4 x 10 exp 5/cu cm. However, the inclusion of the ocean sink does not significantly improve the simulation of the observed interhemispheric gradient of methyl chloroform. Atmospheric transport dominates the simulated CH3CCl3 seasonal cycle throughout the Northern Hemisphere but is less important in the Southern Hemisphere.

  14. Data assimilation into a numerical equatorial ocean model. I. The model and the assimilation algorithm

    NASA Astrophysics Data System (ADS)

    Long, Robert Bryan; Thacker, William Carlisle

    1989-06-01

    Numerical modeling provides a powerful tool for the study of the dynamics of oceans and atmospheres. However, the relevance of modeling results can only be established by reference to observations of the system being modeled. Typical oceanic observation sets are sparse, asynoptic, of mixed type and limited reliability, generally inadequate in some respects, and redundant and inconsistent in others. An optimal procedure for interfacing such data sets with a numerical model is the so-called adjoint method. This procedure effectively assimilates the observations into a run of the numerical model by finding that solution to the model equations that best fits all observations made within some specified space-time interval. The method requires the construction of the adjoint of the numerical model, a process made practical for models of realistic complexity by the work of Thacker and Long. In the present paper, the first of two parts, we illustrate the application of Thacker and Long's approach by constructing a data-assimilating version of an equatorial ocean model incorporating the adjoint method. The model is subsequently run for 5 years to near-steady-state, and exhibits many of the features known to be characteristic of equatorial oceanic flows. Using the last 54 days of the run as a control, a set of simulated sea-level and subsurface-density observations are collected, then successfully assimilated to demonstrate that the procedure can recover the control run, given a generous amount of data. In part II we conduct a sequence of numerical experiments to explore the ability of more limited sets of observations to fix the state of the modeled ocean; in the process, we examine the potential value of sea-level data obtained via satellite altimetry.

  15. SAR image simulation in the time domain for moving ocean surfaces.

    PubMed

    Yoshida, Takero; Rheem, Chang-Kyu

    2013-04-02

    This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces. We have designed the simulation based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images. The time domain simulation is able to obtain time series of microwave backscattering modulated by the orbital motions of ocean waves. Physical optics approximation is applied to calculate microwave backscattering. The computational grids are smaller than transmit microwave to demonstrate accurate interaction between electromagnetic waves and ocean surface waves. In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves. The SAR images of stationary and moving targets are simulated to confirm SAR signal processing and motion induced modulation. Furthermore, the azimuth signals from the regular wave traveling to the azimuth direction also show the azimuthal shifts due to the orbital motions. In addition, incident angle dependence is simulated for irregular wind waves to compare with Bragg scattering theory. The simulation results are in good agreement with the theory. These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.

  16. Forcing of the deep ocean circulation in simulations of the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Schmittner, A.; Meissner, K. J.; Eby, M.; Weaver, A. J.

    2002-05-01

    From the interpretation of different proxy data it is widely believed that the North Atlantic thermohaline circulation during the maximum of the last ice age ~21,000 years ago was considerably weaker than today. Recent equilibrium simulations with a coupled ocean-atmosphere-sea ice model successfully simulated a reduction in North Atlantic Deep Water (NADW) formation consistent with reconstructions. Here we examine the influence of different air-sea fluxes on simulated changes in the deep ocean circulation between the Last Glacial Maximum and present day. We find that changes in the oceanic surface freshwater fluxes are the dominant forcing mechanism for the reduced Atlantic overturning. Diminished export of freshwater out of the Atlantic drainage basin through the atmosphere decreases surface salinities in the North Atlantic, leading to less NADW formation in the colder climate. Changes in heat fluxes, which lead to increased sea surface densities in the North Atlantic and therefore to an enhanced overturning, are of secondary importance. Wind stress variations seem to play a negligible role. The degree to which the Atlantic freshwater export and hence the NADW formation are reduced depends on the formulation of the atmospheric hydrological cycle and on the strength of the overturning in the present-day simulation. Simulated changes in sea surface properties for a large variety of overturning strengths are compared with different reconstruction data sets. The results depend strongly on the data set used. Sea surface temperature reconstructions from Climate: Long-Range Investigation, Mapping, and Prediction (CLIMAP) and earlier salinity reconstructions based on planktonic foraminifera are most consistent with a significant reduction of the circulation, while recent reconstructions using dinocyst assemblages allow no unequivocal conclusion.

  17. (Modeling the upper ocean and its interaction with the atmosphere)

    SciTech Connect

    Peng, Tsung-Hung.

    1990-03-28

    The traveler attended the International Meeting on Modeling the Physics, Biology and Chemistry of the Upper Ocean and Its Interaction with the Atmosphere in London, England, and presented a lecture entitled Modeling the Seasonality of CO{sub 2} in the North Atlantic.'' This international meeting was jointly sponsored by the International Geosphere Biosphere Programme and the Joint Global Ocean Flux Study. Most lectures focused on the modeling of the upper ocean, with a particular emphasis in the area of marine biology and marine ecosystems. Models ranged from simple box ocean models to general circulation models. A total of 16 papers were presented in this two-day conference. At the end of the conference, it became clear that a better understanding of global change in climate atmospheric CO{sub 2} variations requires a closer link between the studies of marine biology and ocean physics and chemistry.

  18. Observed and Modeled Trends in Southern Ocean Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2003-01-01

    Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong

  19. Simulations of bacterial chemotaxis in the turbulent ocean

    NASA Astrophysics Data System (ADS)

    Watteaux, Romain; Taylor, John

    2012-11-01

    Nearly half of the global primary production occurs in the oceans. Between 30 and 50% of the newly generated carbon is released into the surrounding water as dissolved organic matter (DOM), and is almost exclusively accessible to bacteria. By consuming DOM and returning the carbon to the marine food web, bacteria act as recyclers. Some bacteria are motile and have the ability to modify their otherwise random motility in response to a chemical cue, a process known as chemotaxis. It has been recently shown that motile bacteria can benefit from turbulence by clustering around thin DOM filaments, thereby increasing their uptake (Taylor and Stocker, Science, accepted). Here, we extend the previous analysis by considering weakly diffusive DOM patches (with a Schmidt number, Sc = ν /κC up to 1000), and examine the counteracting effects of chemotaxis and random motility. Using direct numerical simulations (DNS), we find that the uptake enhancement depends on characteristic length scales of DOM and bacteria filaments, which in turn depend on three parameters: the turbulent dissipation rate, the bacteria swimming speed, and the DOM diffusivity. By exploring a range of realistic parameter values, we are able to characterize the advantage afforded by motility.

  20. Including eddies in global ocean models

    NASA Astrophysics Data System (ADS)

    Semtner, Albert J.; Chervin, Robert M.

    The ocean is a turbulent fluid that is driven by winds and by surface exchanges of heat and moisture. It is as important as the atmosphere in governing climate through heat distribution, but so little is known about the ocean that it remains a “final frontier” on the face of the Earth. Many ocean currents are truly global in extent, such as the Antarctic Circumpolar Current and the “conveyor belt” that connects the North Atlantic and North Pacific oceans by flows around the southern tips of Africa and South America. It has long been a dream of some oceanographers to supplement the very limited observational knowledge by reconstructing the currents of the world ocean from the first principles of physics on a computer. However, until very recently, the prospect of doing this was thwarted by the fact that fluctuating currents known as “mesoscale eddies” could not be explicitly included in the calculation.

  1. In Situ Eddy Analysis in a High-Resolution Ocean Climate Model.

    PubMed

    Woodring, Jonathan; Petersen, Mark; Schmeißer, Andre; Patchett, John; Ahrens, James; Hagen, Hans

    2016-01-01

    An eddy is a feature associated with a rotating body of fluid, surrounded by a ring of shearing fluid. In the ocean, eddies are 10 to 150 km in diameter, are spawned by boundary currents and baroclinic instabilities, may live for hundreds of days, and travel for hundreds of kilometers. Eddies are important in climate studies because they transport heat, salt, and nutrients through the world's oceans and are vessels of biological productivity. The study of eddies in global ocean-climate models requires large-scale, high-resolution simulations. This poses a problem for feasible (timely) eddy analysis, as ocean simulations generate massive amounts of data, causing a bottleneck for traditional analysis workflows. To enable eddy studies, we have developed an in situ workflow for the quantitative and qualitative analysis of MPAS-Ocean, a high-resolution ocean climate model, in collaboration with the ocean model research and development process. Planned eddy analysis at high spatial and temporal resolutions will not be possible with a postprocessing workflow due to various constraints, such as storage size and I/O time, but the in situ workflow enables it and scales well to ten-thousand processing elements. PMID:26353372

  2. In Situ Eddy Analysis in a High-Resolution Ocean Climate Model.

    PubMed

    Woodring, Jonathan; Petersen, Mark; Schmeißer, Andre; Patchett, John; Ahrens, James; Hagen, Hans

    2016-01-01

    An eddy is a feature associated with a rotating body of fluid, surrounded by a ring of shearing fluid. In the ocean, eddies are 10 to 150 km in diameter, are spawned by boundary currents and baroclinic instabilities, may live for hundreds of days, and travel for hundreds of kilometers. Eddies are important in climate studies because they transport heat, salt, and nutrients through the world's oceans and are vessels of biological productivity. The study of eddies in global ocean-climate models requires large-scale, high-resolution simulations. This poses a problem for feasible (timely) eddy analysis, as ocean simulations generate massive amounts of data, causing a bottleneck for traditional analysis workflows. To enable eddy studies, we have developed an in situ workflow for the quantitative and qualitative analysis of MPAS-Ocean, a high-resolution ocean climate model, in collaboration with the ocean model research and development process. Planned eddy analysis at high spatial and temporal resolutions will not be possible with a postprocessing workflow due to various constraints, such as storage size and I/O time, but the in situ workflow enables it and scales well to ten-thousand processing elements.

  3. Climate variability and predictability associated with the Indo-Pacific Oceanic Channel Dynamics in the CCSM4 Coupled System Model

    NASA Astrophysics Data System (ADS)

    Yuan, Dongliang; Xu, Peng; Xu, Tengfei

    2016-03-01

    An experiment using the Community Climate System Model (CCSM4), a participant of the Coupled Model Intercomparison Project phase-5 (CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole (IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.

  4. Modelling Tropical Cyclones-Ocean interactions: the role of the Atmophere - Ocean coupling frequency

    NASA Astrophysics Data System (ADS)

    Scoccimarro, Enrico; Fogli, Pier Giuseppe; Gualdi, Silvio; Masina, Simona; Navarra, Antonio

    2016-04-01

    The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. TCs affect the thermal and dynamical structure of the ocean, but the magnitude of the impact is still uncertain. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new CMCC-CM2VHR General Circulation Model, having a horizontal resolution of 1/4 degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-5 Typhoons. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components. In this work, we found that a better representation of the negative Sea Surface Temperature - TC induced feedback, through a high (hourly) coupling frequency, ensures the reduction of the TC induced Power Dissipation Index (PDI) bias of one order of magnitude. In addition, a cat-5 storm case study is deeply investigated also in terms of TC effects on the deep ocean.

  5. Wave hindcast experiments in the Indian Ocean using MIKE 21 SW model

    NASA Astrophysics Data System (ADS)

    Remya, P. G.; Kumar, Raj; Basu, Sujit; Sarkar, Abhijit

    2012-04-01

    Wave prediction and hindcast studies are important in ocean engineering, coastal infrastructure development and management. In view of sparse and infrequent in-situ observations, model derived hindcast wave data can be used for the assessment of wave climate in offshore and coastal areas. In the present study, MIKE 21 SW Model has been used to carry out wave hindcast experiments in the Indian Ocean. Model runs have been made for the year 2005 using QuickSCAT scatterometer winds blended with ECMWF model winds. In order to study the impact of southern ocean swells, the model has been run in two different domains, with the southern boundary being shifted far south for the Domain 60S model. The model simulated wave parameters have been validated by comparing with buoy and altimeter data and various statistical yardsticks have been employed to quantify the validation. Possible reason for the poorer performance of the model in the Arabian Sea has also been pointed out.

  6. Interannual Sea Level Variations in the Tropical Indian Ocean from Geosat and Shallow Water Simulations

    NASA Technical Reports Server (NTRS)

    Perigaud, Claire; Delecluse, Pascale

    1993-01-01

    Sea level variations of the Indian Ocean north of 20 deg S are analyzed from Geosat satellite altimeter data over April 1985-September 1989. These variations are compared and interpreted with numerical simulations derived from a reduced gravity model forced by FSU observed winds over the same period. After decomposition into complex empirical orthogonal functions, the low-frequency anomalies are described by the first two modes for observations as well as for simulations. The sums of the two modes contain 34% and 40% of the observed and simulated variances, respectively. Averaged over the basin, the observed and simulated sea level changes are correlated by 0.92 over 1985-1988. The strongest change happens during the El Ninio 1986-1987: between winter 1986 and summer 1987 the basin-averaged sea level rises by approx. 1 cm. These low-frequency variations can partly be explained by changes in the Sverdrup circulation. The southern tropical Indian Ocean between 1O deg and 20 deg S is the domain where those changes are strongest: the averaged sea level rises by approx. 4.5 cm between winter 1986 and winter 1987. There, the signal propagates southwestward across the basin at a speed similar to free Rossby waves. Sensitivity of observed anomalies is examined over 1987-1988, with different orbit ephemeris, tropospheric corrections, and error reduction processes. The uncertainty of the basin-averaged sea level estimates is mostly due to the way the orbit error is reduced and reaches approx. 1 cm. Nonetheless, spatial correlation is good between the various observations and better than between observations and simulations. Sensitivity of simulated anomalies to the wind uncertainty, examined with Former Soviet Union (FSU) and European Center for Medium-Range Weather Forecasting (ECMWF) forcings over 1985-1988, shows that the variance of the simulations driven by ECMWF is 52% smaller, as FSU winds are stronger than ECMWF. Results show that the wind strength also affects the

  7. Modeling the 2004 Indian Ocean Tsunami for Introductory Physics Students

    ERIC Educational Resources Information Center

    DiLisi, Gregory A.; Rarick, Richard A.

    2006-01-01

    In this paper we develop materials to address student interest in the Indian Ocean tsunami of December 2004. We discuss the physical characteristics of tsunamis and some of the specific data regarding the 2004 event. Finally, we create an easy-to-make tsunami tank to run simulations in the classroom. The simulations exhibit three dramatic…

  8. Parallelism and optimization of numerical ocean forecasting model

    NASA Astrophysics Data System (ADS)

    Xu, Jianliang; Pang, Renbo; Teng, Junhua; Liang, Hongtao; Yang, Dandan

    2016-10-01

    According to the characteristics of Chinese marginal seas, the Marginal Sea Model of China (MSMC) has been developed independently in China. Because the model requires long simulation time, as a routine forecasting model, the parallelism of MSMC becomes necessary to be introduced to improve the performance of it. However, some methods used in MSMC, such as Successive Over Relaxation (SOR) algorithm, are not suitable for parallelism. In this paper, methods are developedto solve the parallel problem of the SOR algorithm following the steps as below. First, based on a 3D computing grid system, an automatic data partition method is implemented to dynamically divide the computing grid according to computing resources. Next, based on the characteristics of the numerical forecasting model, a parallel method is designed to solve the parallel problem of the SOR algorithm. Lastly, a communication optimization method is provided to avoid the cost of communication. In the communication optimization method, the non-blocking communication of Message Passing Interface (MPI) is used to implement the parallelism of MSMC with complex physical equations, and the process of communication is overlapped with the computations for improving the performance of parallel MSMC. The experiments show that the parallel MSMC runs 97.2 times faster than the serial MSMC, and root mean square error between the parallel MSMC and the serial MSMC is less than 0.01 for a 30-day simulation (172800 time steps), which meets the requirements of timeliness and accuracy for numerical ocean forecasting products.

  9. Constructing an idealized model of the North Atlantic Ocean using slippery sacks

    NASA Astrophysics Data System (ADS)

    Haertel, Patrick T.; Van Roekel, Luke; Jensen, Tommy G.

    This paper documents the continued development and testing of a new Lagrangian oceanic general circulation model. The slippery sacks ocean model (SSOM), which represents a body of water as a pile of conforming parcels, is improved and is used to simulate circulations in homogeneous oceans and in an idealized model of the North Atlantic Ocean. A method for including horizontal mixing in the SSOM is presented. A given sack's nearest neighbors are identified in the positive and negative x- and y-directions, and the sack exchanges momentum and/or tracers with these neighbors. This formulation of mixing is straightforward to implement, computationally efficient, and it produces results similar to a standard Eulerian finite-difference representation of diffusion. The model's ability to reproduce the Stommel and Munk solutions to the classical western boundary current problem is tested. When steps are taken to reduce the potential energy barrier to sacks crossing one another, the model generates circulations that are consistent with linear theory. In moderately non-linear regimes the model produces appropriate departures from linear solutions including a boundary current that continues along the northern boundary for a time. Taking advantage of the new mixing scheme and lessons learned from simulations of homogeneous oceans, the authors construct an idealized model of the North Atlantic Ocean. They compare simulations conducted with the SSOM to similar simulations conducted with the Massachusetts Institute of Technology general circulation model (MITgcm). The SSOM and the MITgcm produce similar wind-forced gyres, thermocline structure, and meridional overturning. The SSOM is also used to explore how circulations change in the limit when tracer diffusion goes to zero.

  10. Simulating the amplification of orbital forcing by ocean feedbacks in the last glaciation.

    PubMed

    Khodri, M; Leclainche, Y; Ramstein, G; Braconnot, P; Marti, O; Cortijo, E

    2001-03-29

    According to Milankovitch theory, the lower summer insolation at high latitudes about 115,000 years ago allowed winter snow to persist throughout summer, leading to ice-sheet build-up and glaciation. But attempts to simulate the last glaciation using global atmospheric models have failed to produce this outcome when forced by insolation changes only. These results point towards the importance of feedback effects-for example, through changes in vegetation or the ocean circulation-for the amplification of solar forcing. Here we present a fully coupled ocean-atmosphere model of the last glaciation that produces a build-up of perennial snow cover at known locations of ice sheets during this period. We show that ocean feedbacks lead to a cooling of the high northern latitudes, along with an increase in atmospheric moisture transport from the Equator to the poles. These changes agree with available geological data and, together, they lead to an increased delivery of snow to high northern latitudes. The mechanism we present explains the onset of glaciation-which would be amplified by changes in vegetation-in response to weak orbital forcing. PMID:11279492

  11. STOIC: An Assessment of Coupled Model Climatology and Variability in Tropical Ocean Regions

    SciTech Connect

    Davey, M.K.; Sperber, K.R.; Huddleston, M

    2000-08-30

    The tropics are regions of strong ocean-atmosphere interaction on seasonal and interannual timescales, so a good representation of observed tropical behavior is a desirable objective for coupled ocean-atmosphere general circulation models (CGCMs). To broaden and update previous assessments (Mechoso et al. 1995, Neelin et al. 1992), two complementary projects were initiated by the CLIVAR Working Group on Seasonal to Interannual Prediction (WGSIP): the El Nino Simulation Intercomparison Project (ENSIP, by Mojib Latif) and STOIC (Study of Tropical Oceans In Coupled models). The aim was to compare models against observations to identify common weaknesses and strengths. Results from ENSIP concentrating on the equatorial Pacific have been described by Latif et al. (2000), hereafter ENSIP2000. A detailed report on STOIC is available via anonymous ftp at email.meto.gov.uk/pub/cr/ ''stoic'' and is summarized in Davey et al. (2000). The STOIC analyses extend beyond the equatorial Pacific, to examine behavior in all three tropical ocean regions.

  12. Oceans Abound? Tectonic Tests of Global Ocean Models for Enceladus and Mimas

    NASA Astrophysics Data System (ADS)

    Rhoden, A.; Henning, W. G.; Bland, M. T.; Tajeddine, R.; Hurford, T., Jr.

    2015-12-01

    Librations identified in Cassinidata imply that Mimas either has a global ocean or an irregular core (Tajeddine et al., 2014). A global ocean is the only model consistent with Enceladus' librations (Tajeddine et al., 2015). A global ocean can also explain gravity measurements of Enceladus as long as the overlying ice shell is thicker in the north pole than the south pole (McKinnon, 2015), although a regional sea is also possible (Iess et al., 2014). Generations of fractures at Enceladus' south pole may indicate longitudinal migration of the ice shell, which would also require a global ocean (Patthoff and Kattenhorn, 2011). Because both Mimas and Enceladus have eccentric orbits (0.0196 and 0.0047, respectively) interior models that include oceans can generate much larger tidal stresses than models without oceans. However, the enhancement in tidal stress due to oceans creates complications for both moons. Mimas' surface is ancient and heavily cratered; only about 40 tectonic features have been identified, globally (Schenk, 2011). The lack of tidal-tectonic activity on Mimas implies that either it has not experienced large tidal stresses over its surface age or that its ice shell behaves quite differently than Europa. Enceladus has a young, heavily-fractured region at the south pole, and an old, heavily-cratered region at the north pole. Are global ocean models compatible with ongoing, tidal-tectonic activity at Enceladus' south pole and the lack of activity on Mimas and at Enceladus' north pole? We consider whether global oceans are compatible with the geologic records of Mimas and Enceladus by calculating tidal stresses for 5-layer interior structure models. To explore the range of possible interior structures, we vary the ice shell thickness, the depth of the upper brittle ice layer, and the viscosities of the brittle and ductile ice layers. We find that a global ocean within Mimas generates tidal stresses comparable to those on Europa (~100 kPa) and in some cases

  13. Coupled atmosphere-ocean models of Titan's past

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, James B.; Lunine, Jonathan I.; Courtin, Regis

    1993-01-01

    The behavior and possible past evolution of fully coupled atmosphere and ocean model of Titan are investigated. It is found that Titan's surface temperature was about 20 K cooler at 4 Gyr ago and will be about 5 K warmer 0.5 Gyr in the future. The change in solar luminosity and the conversion of oceanic CH4 to C2H6 drive the evolution of the ocean and atmosphere over time. Titan appears to have experienced a frozen epoch about 3 Gyr ago independent of whether an ocean is present or not. This finding may have important implications for understanding the inventory of Titan's volatile compounds.

  14. Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.

    1999-01-01

    A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological

  15. Intercomparison of present and future climates simulated by coupled ocean-atmosphere GCMs

    SciTech Connect

    Covey, C; AchutaRao, K M; Lambert, S J

    2000-09-06

    We present an overview of results from the most recent phase of the Coupled Model Intercomparison Project (CMIP). This phase of CMIP has archived output from both unforced (''control run'') and perturbed (1% per year increasing atmospheric carbon dioxide) simulations by 15 modern coupled ocean-atmosphere general circulation models. The models are about equally divided between those employing and those not employing ad hoc flux corrections at the ocean-atmosphere interface. The new generation of non-flux-connected control runs are nearly as stable and agree with observations nearly as well as the flux-corrected models. This development represents significant progress in the state of the art of climate modeling since the Second (1995) Scientific Assessment Report of the Intergovernmental Panel on Climate Change (IPCC; see Gates et al. 1996). From the increasing-CO{sub 2} runs, we find that differences between different models, while substantial, are not as great as would be expected from earlier assessments that relied on equilibrium climate sensitivity.

  16. Decadal-Scale Response of the Antarctic Ice sheet to a Warming Ocean using the POPSICLES Coupled Ice Sheet-Ocean model

    NASA Astrophysics Data System (ADS)

    Martin, Daniel; Asay-Davis, Xylar; Cornford, Stephen; Price, Stephen; Ng, Esmond; Collins, William

    2016-04-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period from 1990 to 2010. We use the CORE v. 2 interannual forcing data to force the ocean model. Simulations are performed at 0.1 degree (~5 km) ocean resolution with adaptive ice sheet resolution as fine as 500 m to adequately resolve the grounding line dynamics. We discuss the effect of improved ocean mixing and subshelf bathymetry (vs. the standard Bedmap2 bathymetry) on the behavior of the coupled system, comparing time-averaged melt rates below a number of major ice shelves with those reported in the literature. We also present seasonal variability and decadal melting trends from several Antarctic regions, along with the response of the ice shelves and the consequent dynamic response of the grounded ice sheet. POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program, and the BISICLES ice-sheet model. POP2x includes sub-ice-shelf circulation using partial top cells and the commonly used three-equation boundary layer physics. Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP) and other continental-scale simulations and melt-rate observations. BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3d) and realistic configurations.

  17. Experimental Simulations of Lunar Magma Ocean Crystallization: The Plot (But Not the Crust) Thickens

    NASA Technical Reports Server (NTRS)

    Draper, D. S.; Rapp, J. F.; Elardo, S. M.; Shearer, C. K., Jr.; Neal, C. R.

    2016-01-01

    Numerical models of differentiation of a global-scale lunar magma ocean (LMO) have raised as many questions as they have answered. Recent orbital missions and sample studies have provided new context for a large range of lithologies, from the comparatively magnesian "purest anorthosite" reported by to Si-rich domes and spinel-rich clasts with widespread areal distributions. In addition, the GRAIL mission provided strong constraints on lunar crustal density and average thickness. Can this increasingly complex geology be accounted for via the formation and evolution of the LMO? We have in recent years been conducting extensive sets of petrologic experiments designed to fully simulate LMO crystallization, which had not been attempted previously. Here we review the key results from these experiments, which show that LMO differentiation is more complex than initial models suggested. Several important features expected from LMO crystallization models have yet to be reproduced experimentally; combined modelling and experimental work by our group is ongoing.

  18. The Origin of Systematic Errors in the GCM Simulation of ITCZ Precipitation over Oceans

    NASA Technical Reports Server (NTRS)

    Chao, Winston C.; Suarez, Max J.; Bacmeister, Julio T.; Chen, Baode; Takacs, Lawrence L.

    2006-01-01

    This study provides explanations for some of the experimental findings of Chao (2000) and Chao and Chen (2001) concerning the mechanisms responsible for the ITCZ in an aqua-planet model. These explanations are then applied to explain the origin of some of the systematic errors in the GCM simulation of ITCZ precipitatin over oceans. The ITCZ systematic errors are highly sensitive to model physics and by extension model horizontal resolution. The findings in this study along with those of Chao (2000) and Chao and Chen (2001, 2004) contribute to building a theoretical foundation for ITCZ study. A few possible methods of alleviating the systematic errors in the GCM simulaiton of ITCZ are discussed. This study uses a recent version of the Goddard Modeling and Assimilation Office's Goddard Earth Observing System (GEOS-5) GCM.

  19. Multi-model attribution of upper-ocean temperature changes using an isothermal approach

    PubMed Central

    Weller, Evan; Min, Seung-Ki; Palmer, Matthew D.; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

    2016-01-01

    Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived. PMID:27245575

  20. Multi-model attribution of upper-ocean temperature changes using an isothermal approach.

    PubMed

    Weller, Evan; Min, Seung-Ki; Palmer, Matthew D; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

    2016-06-01

    Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived.

  1. Multi-model attribution of upper-ocean temperature changes using an isothermal approach

    NASA Astrophysics Data System (ADS)

    Weller, Evan; Min, Seung-Ki; Palmer, Matthew D.; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

    2016-06-01

    Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived.

  2. Multi-model attribution of upper-ocean temperature changes using an isothermal approach.

    PubMed

    Weller, Evan; Min, Seung-Ki; Palmer, Matthew D; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

    2016-01-01

    Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived. PMID:27245575

  3. Parameterizations in high resolution isopycanl wind-driven ocean models

    SciTech Connect

    Jensen, T.G.; Randall, D.A.

    1993-01-01

    For the CHAMMP project, we proposed to implement and test new numerical schemes, parameterizations of boundary layer flow and development and implement mixed layer physics in an existing isopycnal models. The objectives for the proposed research were; implement the Arakawa and Hsu, scheme in an existing isopycnal model of the Indian Ocean; recode the new model for a highly parallel architecture; determine effects of various parameterizations of islands; determine the correct lateral boundary condition for boundary layer currents, as for instance the Gulf Stream and other western boundary currents.; and incorporate a oceanic mixed layer on top of the isopycnal deep layers. This is, primarily a model development project, with emphasis on determining the influence and parameterization of narrow flows along continents and through chains of small islands on the large scale oceanic circulation, which is resolved by climate models. The new model is based on the multi-layer FSU Indian Ocean model. Our research strategy is to; recode a one-layer version of the Indian Ocean Model for a highly parallel computer; add thermodynamics to a rectangular domain version of the new model; implement the irregular domain from the Indian Ocean Model into the box model; change the numerical scheme for the continuity equation to the scheme proposed by; perform parameterization experiments with various coast line and island geometries. This report discusses project progress for period August 1, 1992 through December 31, 1992.

  4. Using ocean tracers to reduce uncertainties about ocean diapycnal mixing and model projections

    NASA Astrophysics Data System (ADS)

    Goes, M. P.; Urban, N.; Keller, K.; Schmittner, A.; Tonkonojenkov, R.; Haran, M.

    2010-12-01

    Current projections of the oceanic response to anthropogenic climate forcings are uncertain. Two key sources of these uncertainties are (i) structural errors in current Earth system models and (ii) imperfect knowledge of model parameters. Ocean tracers observations have the potential to reduce these uncertainties. Previous studies typically consider each tracer separately, neglect potentially important statistical properties of the system, or use methods that impose rather daunting computational demands. Here we extend and improve upon a recently developed approach using horizontally averaged vertical profiles of chlorofluorocarbon (CFC-11), radiocarbon (DC14), and temperature (T) observations to reduce model parametric and structural uncertainties. Our method estimates a joint probability density function, which considers cross-tracer correlations and spatial autocorrelations of the errors. We illustrate this method by estimating two model parameters related to the vertical diffusivity, the background vertical diffusivity and the upper Southern Ocean mixing. We show that enhancing the upper Southern Ocean mixing in the model improves the representations of ocean tracers, as well as improves hindcasts of the Atlantic Meridional Overturning Circulation (AMOC) and Ocean Carbon uptake. The most probable value of the background vertical diffusivity in the pelagic pycnocline is between 0.1-0.2 cm2/s. According to the statistical method, observations of DC14 reduce the uncertainty about the background vertical diffusivity the most followed by CFC-11 and T. Using all three tracers jointly reduces the model uncertainty by 40%, more than each tracer individually. Given several important caveats, we illustrate how the reduced model parametric uncertainty improves probabilistic projections of the AMOC and Ocean Carbon uptake.

  5. Response of the Miliolid Archaias angulatus to simulated ocean acidification

    USGS Publications Warehouse

    Knorr, Paul O.; Robbins, Lisa L.; Harries, Peter J.; Hallock, Pamela; Wynn, Jonathan

    2015-01-01

    A common, but not universal, effect of ocean acidification on benthic foraminifera is a reduction in the growth rate. The miliolid Archaias angulatus is a high-Mg (>4 mole% MgCO3), symbiont-bearing, soritid benthic foraminifer that contributes to Caribbean reef carbonate sediments. A laboratory culture study assessed the effects of reduced pH on the growth of A. angulatus. We observed a statistically significant 50% reduction in the growth rate (p < 0.01), calculated from changes in maximum diameter, from 160 μm/28 days in the pH 8.0/pCO2air 480 ppm control group to 80 μm/28 days at a treatment level of pH 7.6/pCO2air 1328 ppm. Additionally, pseudopore area, δ18O values, and Mg/Ca ratio all increased, albeit slightly in the latter two variables. The reduction in growth rate indicates that under a high-CO2 setting, future A. angulatus populations will consist of smaller adults. A model using the results of this study estimates that at pH 7.6 A. angulatus carbonate production in the South Florida reef tract and Florida Bay decreases by 85%, from 0.27 Mt/yr to 0.04 Mt/yr, over an area of 9,000 km2.

  6. SSPX simulation model

    SciTech Connect

    Fowler, T K

    1999-09-20

    An analytical approximation to an R-L-C circuit representing SSPX is shown to reproduce the observed capacitor bank efficiency and gun optimization data. As in the SPICE code, the spheromak gun is represented by a fixed resistance chosen to balance energy transfer to the gun. A revised estimate of the magnetic decay time in SSPX Shot 1822 then brings our estimate of the gun efficiency itself in line with the observed spheromak magnetic field for this shot. Prompted by these successes, we present a turbulence-based theoretical model for the spheromak resistance that can be implemented in the SPICE code, of the form: R{sub s} = {kappa}I (1-I{sub 0}/I){sup 2} where I is the gun current, I{sub 0} = ({Lambda}{sub 0}/{mu}{sub 0}){Phi} with bias flux and Taylor eigenvalue {lambda}{sub 0}, and {kappa} is a coefficient based on the magnetic turbulence model employed in Dan Hua's spheromak simulation code. The value of {kappa} giving a good energy balance (around 0.1 m{Omega}/KA) implies substantial turbulence levels. Implementing our model in SPICE would provide a calibration for theoretical calculations of the turbulence. Our analytic approximation to the SPICE code provides guidance to optimize future performance in SSPX, the greatest benefit appearing to come from reducing or eliminating the protective resistor to increase bank efficiency. Eliminating the resistor altogether doubles the bank efficiency and the spheromak magnetic energy.

  7. Electricity Portfolio Simulation Model

    2005-09-01

    Stakeholders often have competing interests when selecting or planning new power plants. The purpose of developing this preliminary Electricity Portfolio Simulation Model (EPSim) is to provide a first cut, dynamic methodology and approach to this problem, that can subsequently be refined and validated, that may help energy planners, policy makers, and energy students better understand the tradeoffs associated with competing electricity portfolios. EPSim allows the user to explore competing electricity portfolios annually from 2002 tomore » 2025 in terms of five different criteria: cost, environmental impacts, energy dependence, health and safety, and sustainability. Four additional criteria (infrastructure vulnerability, service limitations, policy needs and science and technology needs) may be added in future versions of the model. Using an analytic hierarchy process (AHP) approach, users or groups of users apply weights to each of the criteria. The default energy assumptions of the model mimic Department of Energy’s (DOE) electricity portfolio to 2025 (EIA, 2005). At any time, the user can compare alternative portfolios to this reference case portfolio.« less

  8. A Coupled Ice--Ocean Finite--Element Model of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Iakovlev, N.

    2002-05-01

    A coupled ice-ocean finite-element model of the Arctic Ocean is proposed for the Arctic Ocean Model Intercomparison Project (AOMIP) studies. The model is based on the system of primitive equations for ocean. Sea ice dynamics are based upon the cavitating fluid solution described by Flato and Hibler (1990, 1992). The sea ice component of the model is driven by the heat, momentum, and freshwater fluxes provided at the upper and lower ice boundaries. Vertical water turbulence is parameterized by the generalized Prandtl theory for the vertical turbulent diffusion/momentum exchange coefficient. Model domain covers area north of 65o N. Equations are solved on a rotated coordinate system with the North Pole located at 0o N and 180o W. Horizontal model resolution is 1o and the model has 16 vertical levels. The model numerics is based on the finite-element (FE) spatial approximations. Time approximation is made by the time-splitting scheme with a special treatment for nonlinear sea ice rheology. Temperature, salinity and momentum advection is approximated by the FE upwind scheme with no crosswind diffusion created by Hughes and Brooks, 1979. For the sea ice mass and concentration transports the FE analog of the first order directed differences scheme was developed. The integral function of the model is the sea level elevation, which is determined by an implicit time scheme using Generalized Minimal Residual Method (Saad and Schultz, 1986). Major model results and some considerations for the model intercomparison methodology will be discussed.

  9. The seasonal cycle in a coupled ocean-atmosphere model

    SciTech Connect

    Giese, B.S.; Carton, J.A. )

    1994-08-01

    A coupled ocean-atmosphere model is used to investigate the seasonal cycle of sea surface temperature and wind stress in the Tropics. A control run is presented that gives a realistic annual cycle with a cold tongue in the eastern Pacific and Atlantic Oceans. In an attempt to isolate the mechanisms responsible for the particular annual cycle that is observed. The authors conducted a series of numerical experiments in which they alter the solar forcing. These experiments include changing the longitude of perihelion, increasing the heat capacity of land, and changing the length of the solar year. The results demonstrate that the date of perihelion and land heating do not, by themselves, control the annual cycle. However, there is a natural timescale for the development of the annual cycle. When the solar year is shortened to just 6 months, the seasonal variations of climate remain similar in timing to the control run except that then are weaker. When the solar year is lengthened to 18 months, surface temperature in the eastern Pacific develops a prominent semiannual cycle. The semiannual cycle results from the ITCZ crossing the equator into the Southern Hemisphere and the development of a Northern Hemisphere cold tongue during northern winter. The meridional winds maintain an annual cycle, while the zonal winds have a semiannual component. The Atlantic maintains an annual cycle in all variables regardless of changes in the length of the solar year. A final experiment addresses the factors determining the season in which upwelling occurs. In this experiment the sun is maintained perpetual over the equator (simulating March or September conditions). In this case the atmosphere and ocean move toward September conditions, with a Southern Hemisphere cold tongue and connection north of the equator. 19 refs., 10 figs.

  10. Simulated Last Glacial Maximum Δ14CATM and the Deep Glacial Ocean Reservoir

    NASA Astrophysics Data System (ADS)

    Mariotti, V.; Paillard, D.; Roche, D. M.; Bouttes, N.; Bopp, L.

    2012-12-01

    Δ14Catm has been estimated at 420 ± 80‰ (INTCAL09) during the Last Glacial Maximum (LGM) compared to preindustrial times (0‰), but mechanisms explaining this difference are not yet resolved. Δ14Catm is a function of cosmogenic production in high atmosphere and of carbon cycling in the Earth system (through carbon exchange with the superficial reservoirs, ocean and continental biosphere). 10Be-based reconstructions show a contribution of the cosmogenic production term of only 200 ± 200‰ at the LGM. The remaining 220‰ of Δ14Catm variation between the LGM and preindustrial times have thus to be explained by changes in the carbon cycle. Recently, Bouttes et al. (2010) proposed to explain most of the difference in atmospheric pCO2 between glacial and interglacial times by brine-induced ocean stratification in the Southern Ocean. This mechanism involves the formation of very saline water masses that can store Dissolved Inorganic Carbon (DIC) in the deep ocean. During glacial times, the sinking of brines is enhanced and more DIC is stored in the deep ocean, lowering atmospheric pCO2. Such an isolated ocean reservoir would be characterized by a low Δ14C signature. Evidence of such 14C-depleted deep waters during the LGM has recently been found in the Southern Ocean (Skinner et al., 2010). The degassing of this carbon with low Δ14C would then reduce Δ14Catm throughout the deglaciation. We have further developed the CLIMBER-2 model to include a cosmogenic production of 14C as well as an interactive atmospheric 14C reservoir. We investigate the role of both sinking of brines and cosmogenic production, alongside iron and vertical diffusion mechanisms to explain changes in Δ14Catm during the last deglaciation. In our simulations, not only the sinking of brine mechanism is consistent with past Δ14C data but also it explains most of the differences in atmospheric pCO2 and Δ14C between LGM and preindustrial times.

  11. Multimodel simulations of Arctic Ocean sea surface height variability in the period 1970-2009

    NASA Astrophysics Data System (ADS)

    Koldunov, Nikolay V.; Serra, Nuno; Köhl, Armin; Stammer, Detlef; Henry, Olivier; Cazenave, Anny; Prandi, Pierre; Knudsen, Per; Andersen, Ole Baltazar; Gao, Yongqi; Johannessen, Johnny

    2014-12-01

    The performance of several numerical ocean models is assessed with respect to their simulation of sea surface height (SSH) in the Arctic Ocean, and the main patterns of SSH variability and their causes over the past 40 years (1970-2009) are analyzed. In comparison to observations, all tested models broadly reproduce the mean SSH in the Arctic and reveal a good correlation with both tide gauge data and SSH anomalies derived from satellite observations. Although the models do not represent the positive Arctic SSH trend observed over the last two decades, their interannual-to-decadal SSH variability is in reasonable agreement with available measurements. Focusing on results from one of the models for a detailed analysis, it is shown that the decadal-scale SSH variability over shelf areas and deep parts of the Arctic Ocean have pronounced differences that are determined mostly by salinity variations. A further analysis of the three time periods 1987-1992, 1993-2002, and 2003-2009, corresponding to the transition times between cyclonic and anticyclonic regimes of the atmospheric circulation over the Arctic, revealed an unusual increase of SSH in the Amerasian basin during 2003-2009. Results from this model support the recent finding that the increase is caused mainly by changes in freshwater content brought about by the freshwater export through the Canadian Arctic Archiplago and increased Ekman pumping in the Amerasian basin and partly by lateral freshwater transport changes, leading to a redistribution of low-salinity shelf water. Overall, we show that present-day models can be used for investigating the reasons for low-frequency SSH variability in the region.

  12. Modelling the community life strategies in ice-covered oceans

    NASA Astrophysics Data System (ADS)

    Tedesco, L.; Vichi, M.

    2010-12-01

    Our knowledge on the spatial and temporal dynamics of the sea ice ecosystem is still restricted to limited field campaigns. While the big picture is still missing, modelling studies can provide efficient tools to help quantifying and qualifying the role and the importance of the sea ice ecosystem in ice-covered oceans. Modelling the sea ice ecosystem is still a new and promising field of research. The sea ice ecosystem is highly variable in time and space and can be highly diverse. Sea ice organisms are primarily space-limited: the community is able to live only in the liquid fraction of sea ice. However, only if brines pockets and channels are interconnected, sea ice organisms are able to flourish. Thus, an important feature of any biological model is to simulate the Biologically Active Layer (BAL) of sea ice, where brines are interconnected among themselves and with the ocean for gases' and nutrients' replenishment. In order to reproduce the complexity of the sea ice ecosystem, an already existing and comprehensive biogeochemical model of pelagic waters (BFM) has been adapted to the known physical, biological and ecological processes represented in the BAL of sea ice. The new Biogeochemical Flux Model of Sea Ice (BFM-SI) is fully coupled to the pelagic BFM, allowing only the initialization of the pelagic state variables, while all the mass between the two systems is conserved. The full system is an useful tool for process studies: hot topics such as ice thinning and retreating are linked to possible changes in the composition of the sea ice community. Also depending on the duration of the ice season, the community of primary producers may shift from a light-adapted to a light-acclimated community, which indeed differently contributes to the whole biomass of the system. Also, the duration and magnitude of the melting period affect the stratification of surface waters and indeed the chances that the released biomass will be part of the pelagic community and

  13. Thermohaline feedbacks in ocean-climate models of varying complexity

    NASA Astrophysics Data System (ADS)

    den Toom, M.

    2013-03-01

    The Atlantic Meridional Overturning Circulation (AMOC) is considered an important component of the climate system, because of its significant contribution to the heat budget of the Northern Hemisphere. Theoretical models indicate that the AMOC has non-linear dynamics, which result in a strong sensitivity to high latitude freshwater forcing. These models suggest that, as a result of the presence of multiple equilibria, the AMOC may drive large, abrupt shifts of the climate when a certain threshold is exceeded. There is no direct observational evidence that such AMOC related climate variations occur in reality, but the available data are too short and sparse to be conclusive in this case. Therefore, numerical models provide the main source of information regarding the nonlinear behavior of the AMOC. Because numerical models are necessarily incomplete, not in the least because of a lack of computational resources, their results must always be tested for robustness. This thesis presents four studies that examine how the representation of a certain unresolved process affects the behavior of the simulated AMOC The study in chapter 2 deals with the representation of horizontal mixing by mesoscale eddies. It is shown that a simple horizontal tracer mixing scheme is only a reasonable alternative to the more realistic isoneutral / Gent-McWilliams parameterization, provided that no wind forcing is imposed. In chapter 3, it is demonstrated that the use of a stability-dependent tracer diffusivity, which is commonly used to parameterize convection, leads to the occurrence of artificial multiple equilibria. In chapter 4, the representation of ocean-atmosphere interaction is considered. It is found that the sensitivity to anomalous freshwater forcing is only slightly modified if an interactive (sea surface temperature-dependent) atmosphere model is used, instead of a static atmosphere model. In chapter 5, the simulated sensitivity of the AMOC is compared between a model that

  14. Theoretical comparison of subgrid turbulence in atmospheric and oceanic quasi-geostrophic models

    NASA Astrophysics Data System (ADS)

    Kitsios, Vassili; Frederiksen, Jorgen S.; Zidikheri, Meelis J.

    2016-04-01

    Due to the massive disparity between the largest and smallest eddies in the atmosphere and ocean, it is not possible to simulate these flows by explicitly resolving all scales on a computational grid. Instead the large scales are explicitly resolved, and the interactions between the unresolved subgrid turbulence and large resolved scales are parameterised. If these interactions are not properly represented then an increase in resolution will not necessarily improve the accuracy of the large scales. This has been a significant and long-standing problem since the earliest climate simulations. Historically subgrid models for the atmosphere and ocean have been developed in isolation, with the structure of each motivated by different physical phenomena. Here we solve the turbulence closure problem by determining the parameterisation coefficients (eddy viscosities) from the subgrid statistics of high-resolution quasi-geostrophic atmospheric and oceanic simulations. These subgrid coefficients are characterised into a set of simple unifying scaling laws, for truncations made within the enstrophy-cascading inertial range. The ocean additionally has an inverse energy cascading range, within which the subgrid model coefficients have different scaling properties. Simulations adopting these scaling laws are shown to reproduce the statistics of the reference benchmark simulations across resolved scales, with orders of magnitude improvement in computational efficiency. This reduction in both resolution dependence and computational effort will improve the efficiency and accuracy of geophysical research and operational activities that require data generated by general circulation models, including weather, seasonal, and climate prediction; transport studies; and understanding natural variability and extreme events.

  15. GNSS reflectometry aboard the International Space Station: phase-altimetry simulation to detect ocean topography anomalies

    NASA Astrophysics Data System (ADS)

    Semmling, Maximilian; Leister, Vera; Saynisch, Jan; Zus, Florian; Wickert, Jens

    2016-04-01

    An ocean altimetry experiment using Earth reflected GNSS signals has been proposed to the European Space Agency (ESA). It is part of the GNSS Reflectometry Radio Occultation Scatterometry (GEROS) mission that is planned aboard the International Space Station (ISS). Altimetric simulations are presented that examine the detection of ocean topography anomalies assuming GNSS phase delay observations. Such delay measurements are well established for positioning and are possible due to a sufficient synchronization of GNSS receiver and transmitter. For altimetric purpose delays of Earth reflected GNSS signals can be observed similar to radar altimeter signals. The advantage of GNSS is the synchronized separation of transmitter and receiver that allow a significantly increased number of observation per receiver due to more than 70 GNSS transmitters currently in orbit. The altimetric concept has already been applied successfully to flight data recorded over the Mediterranean Sea. The presented altimetric simulation considers anomalies in the Agulhas current region which are obtained from the Region Ocean Model System (ROMS). Suitable reflection events in an elevation range between 3° and 30° last about 10min with ground track's length >3000km. Typical along-track footprints (1s signal integration time) have a length of about 5km. The reflection's Fresnel zone limits the footprint of coherent observations to a major axis extention between 1 to 6km dependent on the elevation. The altimetric performance depends on the signal-to-noise ratio (SNR) of the reflection. Simulation results show that precision is better than 10cm for SNR of 30dB. Whereas, it is worse than 0.5m if SNR goes down to 10dB. Precision, in general, improves towards higher elevation angles. Critical biases are introduced by atmospheric and ionospheric refraction. Corresponding correction strategies are still under investigation.

  16. Global Carbon Cycle Inside GISS ModelE GCM: Results of Equilibrium and Transient Simulations.

    NASA Astrophysics Data System (ADS)

    Aleinov, I.; Kiang, N. Y.; Romanou, A.; Puma, M. J.; Kharecha, P.; Moorcroft, P. R.; Kim, Y.

    2008-12-01

    We present simulation results for a fully coupled carbon cycle inside the ModelE General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies (GISS). The current implementation utilizes the GISS dynamical atmospheric core coupled to the HYCOM ocean model. The atmospheric core uses a Quadratic Upstream Scheme (QUS) for advection of gas tracers, while HYCOM has its own built-in algorithm for advection of ocean tracers. The land surface part of the model consists of the GISS ground hydrology model coupled to the Ent dynamic global terrestrial ecosystem model. The ocean biogeochemistry model based on Watson Gregg's model was implemented inside the HYCOM ocean model. Together with ocean tracer transport, it describes all aspects of the carbon cycle inside the ocean and provides CO2 fluxes for exchange with the atmosphere. CO2 fluxes from land vegetation are provided by the Ent model, which employs well-known photosynthesis relationships of Farquhar, von Caemmerer, and Berry and stomatal conductance of Ball and Berry. Soil CO2 fluxes are also computed by the Ent model according to the CASA soil biogeochemistry model. We present results of fully coupled GCM simulations as well as off-line tests for different components. For GCM simulations, we present results of both equilibrium and transient runs and discuss implications of biases in GCM-predicted climate for accurate modeling of the carbon cycle.

  17. Modeling pCO sub 2 in the upper ocean

    SciTech Connect

    Archer, D.

    1990-12-01

    This report summarizes our current understanding of the physical, chemical, and biological processes that control the natural cycling of carbon dioxide (CO{sub 2}) in the surface ocean. Because the physics of mixing at the ocean surface creates the essential framework for the chemistry and biology, and because the literature on surface ocean mixing is extensive, a major focus of the report is to review existing mixed layer models for the upper ocean and their implementation in global ocean circulation models. Three families of mixed layer models have been developed. The integrated turbulent kinetic energy'' (TKE) models construct a budget for surface ocean TKE, using the wind stress as source and dissipation as sink for TKE. The shear instability'' models maintain profiles of current velocity resulting from the wind stress. Turbulence closure'' models are the most general and the most complicated of the three types, and are based on laboratory studies of fluid turbulence. This paper explores behavioral distinctions between the three types of models, and summarizes previously published comparisons of the generality, accuracy, and computational requirements of the three models. The application of mixed layer models to treatment of sea ice is also reviewed. 101 refs., 7 figs., 1 tab.

  18. Simulation of ENSO with a global atmospheric GCM coupled to a high-resolution, tropical Pacific ocean GCM

    SciTech Connect

    Philander, S.G.H.; Pacanowski, R.C.; Lau, N.C.; Nath, M.J. )

    1992-04-01

    A global atmospheric general circulation model (GCM) coupled to an oceanic GCM that is dynamically active only in the tropical Pacific simulates variability over a broad spectrum of frequencies. Of special interest is the simulation of a realistically irregular Southern Oscillation between warm El Nino and cold La Nino states with time scale of 5 years. The spatial structure is different in the eastern and western halves of the ocean basin. Sea surface temperature changes have their largest amplitude in the central and eastern tropical Pacific, but the low-frequency zonal wind fluctuations are displaced westward and are large over the western half of the basin. During El Nino the associated curl contributes to a pair of pronounced minima in thermocline depth, symmetrically about the equator in the west. In the east the deepening of the thermodine in response to the winds in the west has an approximate Gaussian shape centered on the equator. The low-frequency sea surface temperature and zonal wind anomalies wax and wane practically in place and in phase without significant zonal phase propagation. Thermocline depth variations have phase propagation, a property of the oceanic response to the quasi-periodic winds that force currents and excite a host of waves with periods near 5 years, This indicates that the ocean-atmosphere interactions that cause El Nino to develop at a certain time are countered and reversed by the delayed response of the ocean to earlier winds. Kelvin and Rossby waves cannot be identified in the low-frequency fluctuations of this model, but they are energetic at relatively short periods and are of vital importance to a quasi-resonant oceanic mode with a period near 7 months that is excited in the model. The similarities and differences between the results of this simulation and those with other models are discussed.

  19. Development and testing of Polar Weather Research and Forecasting model: 2. Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Bromwich, David H.; Hines, Keith M.; Bai, Le-Sheng

    2009-04-01

    A version of the state-of-the-art Weather Research and Forecasting model (WRF) has been developed for polar applications. The model known as "Polar WRF" is tested over the Arctic Ocean with a western Arctic grid using 25-km resolution. The model is based upon WRF version 2.2, with improvements to the Noah land surface model and the snowpack treatment. The ocean surface treatment is modified to include fractional sea ice. Simulations consist of a series of 48-h integrations initialized daily at 0000 UTC. The initial 24 h are taken as model spin-up time for the atmospheric hydrology and boundary layer processes. Arctic conditions are simulated for the selected months: January 1998, June 1998, and August 1998 representing midwinter, early summer, and late summer conditions, respectively, from the Surface Heat Budget of the Arctic (SHEBA) study. The albedo of sea ice is specified as a function of time and latitude for June and as a function of time for August. Simulation results are compared with observations of the drifting ice station SHEBA in the Arctic ice pack. Polar WRF simulations show good agreement with observations for all three months. Some differences between the simulations and observation occur owing to apparent errors in the synoptic forecasts and the representation of clouds. Nevertheless, the biases in the simulated fields appear to be small, and Polar WRF appears to be a very good tool for studies of Arctic Ocean meteorology.

  20. Modelling the distribution of plutonium in the Pacific Ocean.

    PubMed

    Nakano, Masanao; Povinec, Pavel P

    2003-01-01

    An Oceanic General Circulation Model (OGCM) including a plutonium scavenging model as well as an advection-diffusion model has been developed for modelling the distribution of plutonium in the Pacific Ocean. Calculated 239, 240Pu water profile concentrations and 239, 240Pu inventories in water and sediment of the Pacific Ocean have showed a reasonable agreement with the experimental results. The presence of local fallout plutonium in central North Pacific waters has been confirmed. The observed 240Pu/239Pu mass ratios confirm that plutonium originating from local fallout from nuclear weapons tests carried out at Bikini and Enewetak Atolls is more rapidly removed from surface waters to deeper waters than plutonium originating from global fallout. The developed OGCM can be used for modelling the dispersion of other non-conservative tracers in the ocean as well. PMID:12860091

  1. Variational Data Assimilation Technique in Mathematical Modeling of Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Agoshkov, V. I.; Zalesny, V. B.

    2012-03-01

    Problems of the variational data assimilation for the primitive equation ocean model constructed at the Institute of Numerical Mathematics, Russian Academy of Sciences are considered. The model has a flexible computational structure and consists of two parts: a forward prognostic model, and its adjoint analog. The numerical algorithm for the forward and adjoint models is constructed based on the method of multicomponent splitting. The method includes splitting with respect to physical processes and space coordinates. Numerical experiments are performed with the use of the Indian Ocean and the World Ocean as examples. These numerical examples support the theoretical conclusions and demonstrate the rationality of the approach using an ocean dynamics model with an observed data assimilation procedure.

  2. Modelling Ocean Dissipation in Icy Satellites: A Comparison of Linear and Quadratic Friction

    NASA Astrophysics Data System (ADS)

    Hay, H.; Matsuyama, I.

    2015-12-01

    Although subsurface oceans are confirmed in Europa, Ganymede, Callisto, and strongly suspected in Enceladus and Titan, the exact mechanism required to heat and maintain these liquid reservoirs over Solar System history remains a mystery. Radiogenic heating can supply enough energy for large satellites whereas tidal dissipation provides the best explanation for the presence of oceans in small icy satellites. The amount of thermal energy actually contributed to the interiors of these icy satellites through oceanic tidal dissipation is largely unquantified. Presented here is a numerical model that builds upon previous work for quantifying tidally dissipated energy in the subsurface oceans of the icy satellites. Recent semi-analytical models (Tyler, 2008 and Matsuyama, 2014) have solved the Laplace Tidal Equations to estimate the time averaged energy flux over an orbital period in icy satellite oceans, neglecting the presence of a solid icy shell. These models are only able to consider linear Rayleigh friction. The numerical model presented here is compared to one of these semi-analytical models, finding excellent agreement between velocity and displacement solutions for all three terms to the tidal potential. Time averaged energy flux is within 2-6% of the analytical values. Quadratic (bottom) friction is then incorporated into the model, replacing linear friction. This approach is commonly applied to terrestrial ocean dissipation studies where dissipation scales nonlinearly with velocity. A suite of simulations are also run for the quadratic friction case which are then compared to and analysed against recent scaling laws developed by Chen and Nimmo (2013).

  3. Oceanic carbon dioxide uptake in a model of century-scale global warming

    SciTech Connect

    Sarmiento, J.L.; Le Quere, C.

    1996-11-22

    In a model of ocean-atmosphere interaction that excluded biological processes, the oceanic uptake of atmospheric carbon dioxide (CO{sub 2}) was substantially reduced in scenarios involving global warming relative to control scenarios. The primary reason for the reduced uptake was the weakening or collapse of the ocean thermohaline circulation. Such a large reduction in this ocean uptake would have a major impact o the future growth rate of atmospheric CO{sub 2}. Model simulations that include a simple representation of biological processes show a potentially large offsetting effect resulting from the downward flux of biogenic carbon. However, the magnitude of the offset is difficult to quantify with present knowledge. 19 refs., 3 figs., 2 tabs.

  4. Modeling the seasonal variability of a coupled Arctic ice-ocean system

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Mellor, George L.

    1992-01-01

    The seasonal variability of the ice-ocean system in the Arctic Basin and the Norwegian, Greenland, and Barents Seas was modeled using a three-dimensional coupled ice-ocean model developed at Princeton University. The snow-ice model uses a three-level thermodynamic scheme similar to Semtner's (1976), but is extended to include the effect of leads. It is shown that simulations using the climatological monthly forcing fields produce a realistic seasonal variability of the ice cover. The ice thickness had a considerable sensitivity to the choice of the long-wave back radiation scheme, but these effects can be reduced through dynamical factors.

  5. Numerical simulation of large-scale ocean-atmosphere coupling and the ocean's role in climate

    NASA Technical Reports Server (NTRS)

    Gates, W. L.

    1983-01-01

    The problem of reducing model generated sigma coordinate data to pressure levels is considered. A mass consistent scheme for performing budget analyses is proposed, wherein variables interpolated to a given pressure level are weighted according to the mass between a nominal pressure level above and either a nominal pressure level below or the Earth's surface, whichever is closer. The method is applied to the atmospheric energy cycle as simulated by the OSU two level atmospheric general circulation model. The results are more realistic than sigma coordinate analyses with respect to eddy decomposition, and are in agreement with the sigma coordinate evaluation of the numerical energy sink. Comparison with less sophisticated budget schemes indicates superiority locally, but not globally.

  6. "One-Stop Shopping" for Ocean Remote-Sensing and Model Data

    NASA Technical Reports Server (NTRS)

    Li, P. Peggy; Vu, Quoc; Chao, Yi; Li, Zhi-Jin; Choi, Jei-Kook

    2006-01-01

    OurOcean Portal 2.0 (http:// ourocean.jpl.nasa.gov) is a software system designed to enable users to easily gain access to ocean observation data, both remote-sensing and in-situ, configure and run an Ocean Model with observation data assimilated on a remote computer, and visualize both the observation data and the model outputs. At present, the observation data and models focus on the California coastal regions and Prince William Sound in Alaska. This system can be used to perform both real-time and retrospective analyses of remote-sensing data and model outputs. OurOcean Portal 2.0 incorporates state-of-the-art information technologies (IT) such as MySQL database, Java Web Server (Apache/Tomcat), Live Access Server (LAS), interactive graphics with Java Applet at the Client site and MatLab/GMT at the server site, and distributed computing. OurOcean currently serves over 20 real-time or historical ocean data products. The data are served in pre-generated plots or their native data format. For some of the datasets, users can choose different plotting parameters and produce customized graphics. OurOcean also serves 3D Ocean Model outputs generated by ROMS (Regional Ocean Model System) using LAS. The Live Access Server (LAS) software, developed by the Pacific Marine Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA), is a configurable Web-server program designed to provide flexible access to geo-referenced scientific data. The model output can be views as plots in horizontal slices, depth profiles or time sequences, or can be downloaded as raw data in different data formats, such as NetCDF, ASCII, Binary, etc. The interactive visualization is provided by graphic software, Ferret, also developed by PMEL. In addition, OurOcean allows users with minimal computing resources to configure and run an Ocean Model with data assimilation on a remote computer. Users may select the forcing input, the data to be assimilated, the

  7. Modeling water clarity in oceans and coasts

    EPA Science Inventory

    In oceans and coastal waters, phytoplankton is the primary producer of organic compounds which form the base for the food chain. The concentration of phytoplankton is a major factor controlling water clarity and the depth to which light penetrates in the water column. The light i...

  8. Assimilation of satellite surface-height anomalies data into a Hybrid Coordinate Ocean Model (HYCOM) over the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Tanajura, C. A. S.; Lima, L. N.; Belyaev, K. P.

    2015-09-01

    The data of sea height anomalies calculated along the tracks of the Jason-1 and Jason-2 satellites are assimilated into the HYCOM hydrodynamic ocean model developed at the University of Miami, USA. We used a known method of data assimilation, the so-called ensemble method of the optimal interpolation scheme (EnOI). In this work, we study the influence of the assimilation of sea height anomalies on other variables of the model. The behavior of the time series of the analyzed and predicted values of the model is compared with a reference calculation (free run), i.e., with the behavior of model variables without assimilation but under the same initial and boundary conditions. The results of the simulation are also compared with the independent data of observations on moorings of the Pilot Research Array in the Tropical Atlantic (PIRATA) and the data of the ARGO floats using objective metrics. The investigations demonstrate that data assimilation under specific conditions results in a significant improvement of the 24-h prediction of the ocean state. The experiments also show that the assimilated fields of the ocean level contain a clearly pronounced mesoscale variability; thus they quantitatively differ from the dynamics obtained in the reference experiment.

  9. A 1/8° coupled biochemical-physical Indian Ocean Regional Model: Physical results and validation

    NASA Astrophysics Data System (ADS)

    Huang, Ke; Derada, Sergio; Xue, Huijie; Xiu, Peng; Chai, Fei; Xie, Qiang; Wang, Dongxiao

    2015-08-01

    A coupled physical-biochemical Indian Ocean Regional Model (IORM), based on the Navy Coastal Ocean Model (NCOM) and the Carbon Silicate Nitrogen Ecosystem (CoSiNE) model was configured with the primary objective of providing an accurate estimate of the oceanic physical state along with the biochemical processes simulated by CoSiNE to understand the variability in the Indian Ocean (IO). The model did not assimilate any data; instead, weak relaxation of temperature and salinity was implemented to keep the model stable in the long-term simulations. In this study, the skill of the IORM in simulating physical states in the IO was evaluated. Basin-scale surface circulation and cross-sectional transports were compared to observations, which demonstrated that the model replicated most of the observed features with reasonably good accuracy. Consistency and biases in the upper ocean temperature, salinity, and mixed layer depth were also analyzed. Lastly, the seasonality in the IO, its response to monsoonal forcing, and the evolution and dynamics of surface and subsurface dipole events were examined. The IORM reproduced most of the dynamic features including Ekman pumping, wave propagation, and climate variability at both annual and interannual time scales. The internal ocean dynamics and behavior of the modeled sea surface temperature anomaly (SSTA) suggest a coupled ocean/atmosphere instability that will require further research, including sensitivity experiments to realize improvements in model parameterization.

  10. The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in a Coupled Atmosphere-Ocean General Circulation Model

    NASA Astrophysics Data System (ADS)

    Li, F.; Newman, P. A.; Pawson, S.; Waugh, D. W.

    2014-12-01

    Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and surface winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface trend differences on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60ºS. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone

  11. Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces

    PubMed Central

    Yoshida, Takero; Rheem, Chang-Kyu

    2015-01-01

    A time-domain simulation of along-track interferometric synthetic aperture radar (AT-InSAR) has been developed to support ocean observations. The simulation is in the time domain and based on Bragg scattering to be applicable for moving ocean surfaces. The time-domain simulation is suitable for examining velocities of moving objects. The simulation obtains the time series of microwave backscattering as raw signals for movements of ocean surfaces. In terms of realizing Bragg scattering, the computational grid elements for generating the numerical ocean surface are set to be smaller than the wavelength of the Bragg resonant wave. In this paper, the simulation was conducted for a Bragg resonant wave and irregular waves with currents. As a result, the phases of the received signals from two antennas differ due to the movement of the numerical ocean surfaces. The phase differences shifted by currents were in good agreement with the theoretical values. Therefore, the adaptability of the simulation to observe velocities of ocean surfaces with AT-InSAR was confirmed. PMID:26067197

  12. Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces.

    PubMed

    Yoshida, Takero; Rheem, Chang-Kyu

    2015-01-01

    A time-domain simulation of along-track interferometric synthetic aperture radar (AT-InSAR) has been developed to support ocean observations. The simulation is in the time domain and based on Bragg scattering to be applicable for moving ocean surfaces. The time-domain simulation is suitable for examining velocities of moving objects. The simulation obtains the time series of microwave backscattering as raw signals for movements of ocean surfaces. In terms of realizing Bragg scattering, the computational grid elements for generating the numerical ocean surface are set to be smaller than the wavelength of the Bragg resonant wave. In this paper, the simulation was conducted for a Bragg resonant wave and irregular waves with currents. As a result, the phases of the received signals from two antennas differ due to the movement of the numerical ocean surfaces. The phase differences shifted by currents were in good agreement with the theoretical values. Therefore, the adaptability of the simulation to observe velocities of ocean surfaces with AT-InSAR was confirmed. PMID:26067197

  13. Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces.

    PubMed

    Yoshida, Takero; Rheem, Chang-Kyu

    2015-06-10

    A time-domain simulation of along-track interferometric synthetic aperture radar (AT-InSAR) has been developed to support ocean observations. The simulation is in the time domain and based on Bragg scattering to be applicable for moving ocean surfaces. The time-domain simulation is suitable for examining velocities of moving objects. The simulation obtains the time series of microwave backscattering as raw signals for movements of ocean surfaces. In terms of realizing Bragg scattering, the computational grid elements for generating the numerical ocean surface are set to be smaller than the wavelength of the Bragg resonant wave. In this paper, the simulation was conducted for a Bragg resonant wave and irregular waves with currents. As a result, the phases of the received signals from two antennas differ due to the movement of the numerical ocean surfaces. The phase differences shifted by currents were in good agreement with the theoretical values. Therefore, the adaptability of the simulation to observe velocities of ocean surfaces with AT-InSAR was confirmed.

  14. Eddy-resolving 1/10° model of the World Ocean

    NASA Astrophysics Data System (ADS)

    Ibrayev, R. A.; Khabeev, R. N.; Ushakov, K. V.

    2012-02-01

    The first results on simulating the intra-annual variability of the World Ocean circulation by use of the eddy-resolving model are considered. For this purpose, a model of the World Ocean with a 1/10° horizontal resolution and 49 vertical levels was developed (a 1/10 × 1/10 × 49 model of the World Ocean). This model is based on the traditional system of three-dimensional equations of the large-scale dynamics of the ocean and boundary conditions with an explicit allowance for water fluxes on the free surface of the ocean. The equations are written in the tripolar coordinate system. The numerical method is based on the separation of the barotropic and baroclinic components of the solution. Discretization in time is implemented using explicit schemes allowing effective parallelization for a large number of processors. The model uses the sub-models of the boundary layer of the atmosphere and the submodel of sea-ice thermodynamics. The model of the World Ocean was developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS) and the P.P. Shirshov Institute of Oceanogy (IO RAS). The formulation of the problem of simulating the intra-annual variability of thermohydrodynamic processes of the World Ocean and the parameterizations that were used are considered. In the numerical experiment, the temporal evolution of the atmospheric effect is determined by the normal annual cycle according to the conditions of the international Coordinated Ocean-Ice Reference Experiment (CORE-I). The calculation was carried out on a multiprocessor computer with distributed memory; 1601 computational cores were used. The presented analysis demonstrates that the obtained results are quite satisfactory when compared to the results that were obtained by other eddy-resolving models of the global ocean. The analysis of the model solution is, to a larger extent, of a descriptive character. A detailed analysis of the results is to be presented in following works

  15. Advances in a distributed approach for ocean model data interoperability

    USGS Publications Warehouse

    Signell, Richard P.; Snowden, Derrick P.

    2014-01-01

    An infrastructure for earth science data is emerging across the globe based on common data models and web services. As we evolve from custom file formats and web sites to standards-based web services and tools, data is becoming easier to distribute, find and retrieve, leaving more time for science. We describe recent advances that make it easier for ocean model providers to share their data, and for users to search, access, analyze and visualize ocean data using MATLAB® and Python®. These include a technique for modelers to create aggregated, Climate and Forecast (CF) metadata convention datasets from collections of non-standard Network Common Data Form (NetCDF) output files, the capability to remotely access data from CF-1.6-compliant NetCDF files using the Open Geospatial Consortium (OGC) Sensor Observation Service (SOS), a metadata standard for unstructured grid model output (UGRID), and tools that utilize both CF and UGRID standards to allow interoperable data search, browse and access. We use examples from the U.S. Integrated Ocean Observing System (IOOS®) Coastal and Ocean Modeling Testbed, a project in which modelers using both structured and unstructured grid model output needed to share their results, to compare their results with other models, and to compare models with observed data. The same techniques used here for ocean modeling output can be applied to atmospheric and climate model output, remote sensing data, digital terrain and bathymetric data.

  16. Model-Based Detection in a Shallow Water Ocean Environment

    SciTech Connect

    Candy, J V

    2001-07-30

    A model-based detector is developed to process shallow water ocean acoustic data. The function of the detector is to adaptively monitor the environment and decide whether or not a change from normal has occurred. Here we develop a processor incorporating both a normal-mode ocean acoustic model and a vertical hydrophone array. The detector is applied to data acquired from the Hudson Canyon experiments at various ranges and its performance is evaluated.

  17. Scaling laws for parametrizations of subgrid interactions in simulations of oceanic circulations

    PubMed Central

    Kitsios, V.; Frederiksen, J. S.; Zidikheri, M. J.

    2014-01-01

    Parametrizations of the subgrid eddy–eddy and eddy–meanfield interactions are developed for the simulation of baroclinic ocean circulations representative of an idealized Antarctic Circumpolar Current. Benchmark simulations are generated using a spectral spherical harmonic quasi-geostrophic model with maximum truncation wavenumber of T=504, which is equivalent to a resolution of 0.24° globally. A stochastic parametrization is used for the eddy–eddy interactions, and a linear deterministic parametrization for the eddy–meanfield interactions. The parametrization coefficients are determined from the statistics of benchmark simulations truncated back to the large eddy simulation (LES) truncation wavenumber, TRsimulations. PMID:24842029

  18. Effects of sinking of salt rejected during formation of sea ice on results of an ocean-atmosphere-sea ice climate model

    NASA Astrophysics Data System (ADS)

    Duffy, P. B.; Eby, M.; Weaver, A. J.

    We show that results of an ocean-atmosphere-sea-ice model are sensitive to the treatment of salt rejected during formation of sea ice. In our Control simulation, we place all rejected salt in the top ocean-model level. In the Plume simulation, we instantaneously mix rejected salt into the subsurface ocean, to a maximum depth which depends on local density gradients. This mimics the effects of subgrid-scale convection of rejected salt. The results of the Plume simulation are more realistic than those of the Control simulation: the spatial pattern of simulated salinities (especially in the Southern Ocean), deep-ocean temperatures, simulated sea-ice extents and surface air temperatures all agree better with observations. A similar pair of simulations using horizontal tracer diffusion instead of the Gent-McWilliams eddy parameterization show similar changes due to instantaneous mixing of rejected salt.

  19. Use of Advanced Meteorological Model Output for Coastal Ocean Modeling in Puget Sound

    SciTech Connect

    Yang, Zhaoqing; Khangaonkar, Tarang; Wang, Taiping

    2011-06-01

    It is a great challenge to specify meteorological forcing in estuarine and coastal circulation modeling using observed data because of the lack of complete datasets. As a result of this limitation, water temperature is often not simulated in estuarine and coastal modeling, with the assumption that density-induced currents are generally dominated by salinity gradients. However, in many situations, temperature gradients could be sufficiently large to influence the baroclinic motion. In this paper, we present an approach to simulate water temperature using outputs from advanced meteorological models. This modeling approach was applied to simulate annual variations of water temperatures of Puget Sound, a fjordal estuary in the Pacific Northwest of USA. Meteorological parameters from North American Region Re-analysis (NARR) model outputs were evaluated with comparisons to observed data at real-time meteorological stations. Model results demonstrated that NARR outputs can be used to drive coastal ocean models for realistic simulations of long-term water-temperature distributions in Puget Sound. Model results indicated that the net flux from NARR can be further improved with the additional information from real-time observations.

  20. Carbon dioxide induced ocean climatic change and tracer experiment with an atmosphere-ocean general circulation model

    SciTech Connect

    Jiang, Xingjian.

    1991-01-01

    The principal objective of this study is to determine whether or not the penetration of a passive tracer is analogous to the penetration of a greenhouse-gas-induced heating. The Atmosphere Ocean General Circulation Model (A-O GCM) has been used to study CO2-induced climate change and the penetration of passive tracers into the world ocean. The present climate and a 2 x CO2 climate have been simulated. The passive tracers tritium, CFC-11, CFC-12 and a 'passive CO2- induced heating' are simulated. The CO2-induced active and passive warmings are larger in the subtropics and high latitudes than in the tropics. The largest difference between the active and passive CO2-induced heatings occur in the North Atlantic deep ocean, with maximum cooling about -1.5C for the active case in layer four of the ocean (1150m). There is no hemispherically asymmetric warming as that found by Manabe et al. (1990) and Stouffer et al. (1990). The convective overturning and large-scale sinking motion are responsible for the large penetration of CO2-induced warming in high latitudes. The CO2-induced circulation changes show that the North Atlantic thermohaline circulation is significantly weakened due to the penetration of CO2-induced heating. Associated with this change, the strength of North Atlantic conveyor belt is reduced, which results in a large warming in the upper ocean and cooling in the deep layers. The characteristic response time ranges from 40-50 years for the active CO2-induced climate change, and 70-160 years for passive CO2-induced climate change. The physical processes controlling the geochemical tracer penetration are very similar to those for the CO2-induced heating. There is not a single tracer which penetrates into the ocean exactly like the active CO2-induced heating in terms of distribution, transport or physical process. CFC's may be the best candidate as a surrogate for the CO2-induced oceanic climate study.

  1. Coupled atmosphere-ocean-wave simulations of a storm event over the Gulf of Lion and Balearic Sea

    USGS Publications Warehouse

    Renault, Lionel; Chiggiato, Jacopo; Warner, John C.; Gomez, Marta; Vizoso, Guillermo; Tintore, Joaquin

    2012-01-01

    The coastal areas of the North-Western Mediterranean Sea are one of the most challenging places for ocean forecasting. This region is exposed to severe storms events that are of short duration. During these events, significant air-sea interactions, strong winds and large sea-state can have catastrophic consequences in the coastal areas. To investigate these air-sea interactions and the oceanic response to such events, we implemented the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System simulating a severe storm in the Mediterranean Sea that occurred in May 2010. During this event, wind speed reached up to 25 m.s-1 inducing significant sea surface cooling (up to 2°C) over the Gulf of Lion (GoL) and along the storm track, and generating surface waves with a significant height of 6 m. It is shown that the event, associated with a cyclogenesis between the Balearic Islands and the GoL, is relatively well reproduced by the coupled system. A surface heat budget analysis showed that ocean vertical mixing was a major contributor to the cooling tendency along the storm track and in the GoL where turbulent heat fluxes also played an important role. Sensitivity experiments on the ocean-atmosphere coupling suggested that the coupled system is sensitive to the momentum flux parameterization as well as air-sea and air-wave coupling. Comparisons with available atmospheric and oceanic observations showed that the use of the fully coupled system provides the most skillful simulation, illustrating the benefit of using a fully coupled ocean-atmosphere-wave model for the assessment of these storm events.

  2. Multi-property modeling of ocean basin carbon fluxes

    NASA Technical Reports Server (NTRS)

    Volk, Tyler

    1988-01-01

    The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

  3. Contrail Modeling and Simulation

    NASA Astrophysics Data System (ADS)

    Paoli, Roberto; Shariff, Karim

    2016-01-01

    There is large uncertainty in the radiative forcing induced by aircraft contrails, particularly after they transform to cirrus. It has recently become possible to simulate contrail evolution for long periods after their formation. We review the main physical processes and simulation efforts in the four phases of contrail evolution, namely the jet, vortex, vortex dissipation, and diffusion phases. Recommendations for further work are given.

  4. Parameterizations in high resolution isopycnal wind-driven ocean models

    NASA Astrophysics Data System (ADS)

    Jensen, T. G.; Randall, D. A.

    1994-01-01

    For the Computer Hardware Advanced Mathematics and Model Physics (CHAMMP) project, developing a new multilayer ocean model, based on the hydrodynamic FSU Indian Ocean model was proposed. The new model will include prognostic temperature and salinity and will be coded for massively parallel machines. Other specific objectives for the proposed research were to: incorporate a oceanic mixed layer on top of the isopycnal deep layers; implement positive definite scheme for advection; determine effects of islands on large scale flow; and investigate lateral boundary conditions for boundary layer currents. The mixed layer model is proposed to be of a bulk type with prognostic equations for temperature and salinity. Development of parallel code will be done in cooperation with other CHAMMP participants, mainly the ocean modelling group at LANL. The main objective is model development, while the application is to determine the influence and parameterization of narrow flows along continents and through chains of small islands on the large scale oceanic circulation. Test runs with artificial wind stress and heat flux will be used to determine model stability, performance, and optimization for the new model configuration. Tests will include western boundary currents, coastal upwelling, and equatorial dynamics. This report discusses project progress for period January 1, 1993 through December 31, 1993.

  5. Main directions in the simulation of physical characteristics of the World Ocean and seas

    NASA Astrophysics Data System (ADS)

    Sarkisyan, A. S.

    2016-07-01

    A brief analysis of the oceanographic papers printed in this issue is presented. For convenience of the reader, the paper by K. Bryan, a prominent scientist and expert in modeling the physical characteristics of the ocean, is discussed in detail. The remaining studies are described briefly in several sections: direct prognostic modeling, diagnosis-adaptation, four-dimensional analysis, and operational oceanography. At the end of the study, we separately discuss the problem of the reproduction of coastal intensification of temperature, salinity, density, and currents. We believe that the quality of the simulation results can be best assessed in terms of the intensity of coastal currents. In conclusion, this opinion is justified in detail.

  6. Simulation of the trans-oceanic tsunami propagation due to the 1883 Krakatau volcanic eruption

    NASA Astrophysics Data System (ADS)

    Choi, B. H.; Pelinovsky, E.; Kim, K. O.; Lee, J. S.

    The 1883 Krakatau volcanic eruption has generated a destructive tsunami higher than 40 m on the Indonesian coast where more than 36 000 lives were lost. Sea level oscillations related with this event have been reported on significant distances from the source in the Indian, Atlantic and Pacific Oceans. Evidence of many manifestations of the Krakatau tsunami was a subject of the intense discussion, and it was suggested that some of them are not related with the direct propagation of the tsunami waves from the Krakatau volcanic eruption. Present paper analyzes the hydrodynamic part of the Krakatau event in details. The worldwide propagation of the tsunami waves generated by the Krakatau volcanic eruption is studied numerically using two conventional models: ray tracing method and two-dimensional linear shallow-water model. The results of the numerical simulations are compared with available data of the tsunami registration.

  7. Measurements and simulations of polarization states of underwater light in clear oceanic waters

    NASA Astrophysics Data System (ADS)

    You, Yu; Tonizzo, Alberto; Gilerson, Alexander A.; Cummings, Molly E.; Brady, Parrish; Sullivan, James M.; Twardowski, Michael S.; Dierssen, Heidi M.; Ahmed, Samir A.; Kattawar, George W.

    2011-08-01

    Polarization states of the underwater light field were measured by a hyperspectral and multiangular polarimeter and a video polarimeter under various atmospheric, surface, and water conditions, as well as solar and viewing geometries, in clear oceanic waters near Port Aransas, Texas. Some of the first comprehensive comparisons were made between the measured polarized light, including the degree and angle of linear polarization and linear Stokes parameters (Q and U), and those from Monte Carlo simulations that used concurrently measured water inherent optical properties and particle volume scattering functions as input. For selected wavelengths in the visible spectrum, measured and model-simulated polarization characteristics were found to be consistent in most cases. Measured degree and angle of linear polarization are found to be largely determined by an in-water single-scattering model. Model simulations suggest that the degree of linear polarization (DoLP) at horizontal viewing directions is highly dependent on the viewing azimuth angle for a low solar elevation. This implies that animals can use the DoLP signal for orientation.

  8. A Coupled Geodesic Ocean and Ice Model for Climate Studies

    NASA Astrophysics Data System (ADS)

    Tokmakian, R.; Lipscomb, W.; Ringler, T.; Stark, D.

    2006-12-01

    A coupled ocean and sea ice model on a geodesic grid has been developed for use in climate studies. Over the years, different grid definitions and finite difference methods have been developed to solve the equations for fluid flow on a sphere. With the use of any traditional latitude/longitude grid, finite differencing methods encounter the "pole problem" where the lines of latitude and longitude converge at the poles. With the use of a quasi-uniform geodesic grid, the "pole problem" can be avoided (Randall et al. 2002, Ringer and Randall, 2002). The ocean model is a primitive equation model with 33 levels (5 m to 500m vertical resolution) with a horizontal grid resolution of approximately 1.2 degrees (40962 grid cells). The model includes second order dissipation. To increase the time step, the gravity wave retardation method of Higdon (2002) is used. The altimetric based bathymetry estimates of Sandwell and Smith (1997) are incorporated into the ocean model. The sea ice model is the CICE model on geodesic grid (Stark et al. 2006). The CICE model includes the elastic-viscous-plastic ice dynamics as defined by Hunke and Dukowicz (2002) and the energy conserving thermodynamics of Bitz and Lipscomb (1999). The ECMWF atmospheric fields provide the forcing at the ocean/ice-atmosphere interface, in preparation of coupling the ocean/ice system to an atmospheric model also on a similar geodesic grid. The initial results of the ocean/ice coupled system show realistic ocean and ice features (e.g. currents, ice thickness) both in their mean and in the variability of these features.

  9. Mechanistic site-based emulation of a global ocean biogeochemical model for parametric analysis and calibration

    NASA Astrophysics Data System (ADS)

    Hemmings, J. C. P.; Challenor, P. G.; Yool, A.

    2014-09-01

    Biogeochemical ocean circulation models used to investigate the role of plankton ecosystems in global change rely on adjustable parameters to compensate for missing biological complexity. In principle, optimal parameter values can be estimated by fitting models to observational data, including satellite ocean colour products such as chlorophyll that achieve good spatial and temporal coverage of the surface ocean. However, comprehensive parametric analyses require large ensemble experiments that are computationally infeasible with global 3-D simulations. Site-based simulations provide an efficient alternative but can only be used to make reliable inferences about global model performance if robust quantitative descriptions of their relationships with the corresponding 3-D simulations can be established. The feasibility of establishing such a relationship is investigated for an intermediate complexity biogeochemistry model (MEDUSA) coupled with a widely-used global ocean model (NEMO). A site-based mechanistic emulator is constructed for surface chlorophyll output from this target model as a function of model parameters. The emulator comprises an array of 1-D simulators and a statistical quantification of the uncertainty in their predictions. The unknown parameter-dependent biogeochemical environment, in terms of initial tracer concentrations and lateral flux information required by the simulators, is a significant source of uncertainty. It is approximated by a mean environment derived from a small ensemble of 3-D simulations representing variability of the target model behaviour over the parameter space of interest. The performance of two alternative uncertainty quantification schemes is examined: a direct method based on comparisons between simulator output and a sample of known target model "truths" and an indirect method that is only partially reliant on knowledge of target model output. In general, chlorophyll records at a representative array of oceanic sites

  10. Detecting toxic diatom blooms from ocean color and a regional ocean model

    NASA Astrophysics Data System (ADS)

    Anderson, Clarissa R.; Kudela, Raphael M.; Benitez-Nelson, Claudia; Sekula-Wood, Emily; Burrell, Christopher T.; Chao, Yi; Langlois, Gregg; Goodman, Jo; Siegel, David A.

    2011-02-01

    An apparent link between upwelling-related physical signatures, macronutrients, and toxic diatom blooms in the various “hotspots” throughout California has motivated attempts to forecast harmful algal blooms (HABs) as a function of select environmental variables. Empirical models for predicting toxic Pseudo-nitzschia blooms in one such region, the Santa Barbara Channel (SBC), are tested in a nowcast mode using predictions based on merging data from MODIS ocean color geophysical products and the Regional Ocean Modeling System (ROMS) applied to the Southern California Bight. Thresholds for each model generate event forecasts. Spatially-explicit, monthly HAB maps are compared to shipboard observations and California monitoring data, demonstrating that the models predict offshore events otherwise undetected by nearshore monitoring. The use of mechanistic hydrodynamic models in concert with empirical, biological models facilitates future process studies on the effects of coastal eutrophication and climate change on regional HAB dynamics.

  11. Annual sea level variations in the southern tropical Indian Ocean from Geosat and shallow-water simulations

    NASA Technical Reports Server (NTRS)

    Perigaud, Claire; Delecluse, Pascale

    1992-01-01

    Sea level variations in the Indian Ocean north of 20 deg S are analyzed from Geosat satellite altimeter data in 1987-1988. These observed variations are compared with numerical simulations from a reduced-gravity model forced by observed winds over the same period. The first complex empirical orthogonal function of observed and simulated variations is an annual signal. For this signal, observations and simulations are highly correlated in both time and space. Off-equatorial sea level variations propagate westward and poleward as Rossby waves. The strongest annual variations occur in the southeastern tropical Indian Ocean. The maximum amplitude (about 12 cm) is located at about 90 deg E, 12 deg S, although the wind stress curl is weak there and east of it. The signal propagates from the eastern boundary to the southwest across almost all the basin.

  12. Atmosphere & ocean modeling on grids of variable resolution

    NASA Astrophysics Data System (ADS)

    Düben, Peter D.; Korn, Peter

    2014-05-01

    Grids of variable resolution are of great interest in Atmosphere and Ocean Modeling as they offer a route to higher local resolution and improved solutions. On the other hand there are changes in grid resolution considered to be problematic because of the errors they create between coarse and fine parts of a grid due to reflection and scattering of waves. On complex multidimensional domains these errors resist theoretical investigation and demand numerical experiments. With a low-order hybrid continuous/discontinuous finite element model of the inviscid and viscous shallow-water equations a numerical study is carried out that investigates the influence of grid refinement on critical features such as wave propagation, turbulent cascades and the representation of geostrophic balance. The refinement technique we use is static h-refinement, where additional grid cells are inserted in regions of interest known a priori. For the specific finite element model under investigation, the simulations suggest that grid refinement does not deteriorate geostrophic balance and turbulent cascades and the shape of mesh transition zones appears to be less important than expected. However, our results show that the static local refinement is able to reduce the local error, but not necessarily the global error and convergence properties with resolution are changed. Our relatively simple tests already illustrate that grid refinement has to go along with a simultaneous change of the parametrization schemes.

  13. The coupled atmosphere-chemistry-ocean model SOCOL-MPIOM

    NASA Astrophysics Data System (ADS)

    Muthers, S.; Anet, J. G.; Stenke, A.; Raible, C. C.; Rozanov, E.; Brönnimann, S.; Peter, T.; Arfeuille, F. X.; Shapiro, A. I.; Beer, J.; Steinhilber, F.; Brugnara, Y.; Schmutz, W.

    2014-05-01

    The newly developed atmosphere-ocean-chemistry-climate model SOCOL-MPIOM is presented by demonstrating the influence of the interactive chemistry module on the climate state and the variability. Therefore, we compare pre-industrial control simulations with (CHEM) and without (NOCHEM) interactive chemistry. In general, the influence of the chemistry on the mean state and the variability is small and mainly restricted to the stratosphere and mesosphere. The largest differences are found for the atmospheric dynamics in the polar regions, with slightly stronger northern and southern winter polar vortices in CHEM. The strengthening of the vortex is related to larger stratospheric temperature gradients, which are attributed to a parametrization of the absorption of ozone and oxygen in the Lyman-alpha, Schumann-Runge, Hartley, and Higgins bands. This effect is parametrized in the version with interactive chemistry only. A second reason for the temperature differences between CHEM and NOCHEM is related to diurnal variations in the ozone concentrations in the higher atmosphere, which are missing in NOCHEM. Furthermore, stratospheric water vapour concentrations differ substantially between the two experiments, but their effect on the temperatures is small. In both setups, the simulated intensity and variability of the northern polar vortex is inside the range of present day observations. Sudden stratospheric warming events are well reproduced in terms of their frequency, but the distribution amongst the winter months is too uniform. Additionally, the performance of SOCOL-MPIOM under changing external forcings is assessed for the period 1600-2000 using an ensemble of simulations driven by a spectral solar forcing reconstruction. The amplitude of the reconstruction is large in comparison to other state-of-the-art reconstructions, providing an upper limit for the importance of the solar signal. In the pre-industrial period (1600-1850) the simulated surface temperature trends

  14. Modeling the Natural Biogeochemical Cycle of Mercury in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Jaegle, L.; Thompson, L.; Emerson, S. R.; Deutsch, C. A.; Trossman, D. S.; Shao, A.

    2012-12-01

    The ocean plays an important role in the biogeochemical cycling of mercury (Hg) because of its large reservoir mass and re-emission flux via evasion. The currently available Hg models, including 2D slab, 1D column and 0D box model cannot fully resolve the marine Hg cycle because of the lack of the proper spatial resolution. In this work, we have implemented Hg biogeochemistry in a state-of-the-art 3D offline ocean tracer model (OFFTRAC). OFFTRAC simulates the evolution of three Hg species (Hg0aq, HgIIaq and HgPaq), which are diffused and advected in the ocean. Hg0aq and HgII aq are interconverted in the surface ocean via parameterized photochemical and biological redox processes. The partitioning between HgIIaq and HgPaq depends on the local levels of particulate organic carbon (POC). The sinking of HgPaq is parameterized by coupling with the nutrient phosphorous cycle simulated in OFFTRAC. The reduction of HgIIaq to Hg0aq in the anaerobic subsurface water is proportional to the remineralizaiton of POC. OFFTRAC is coupled to a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem chemical transport model. The GEOS-Chem simulation includes a geogenic source and provides the atmospheric deposition flux of HgII to the ocean and atmospheric Hg0 concentrations. The riverine input of Hg is calculated based on the climatological monthly mean fresh water discharge from continental to ocean and the average soil concentrations near the river mouth. The results show that the riverine input enhances Hg concentrations at surface by a factor of 2-3 near large river mouths and nearby coastal regions. The riverine input approximately doubles surface Hg concentration over the Arctic because of the small basin volume. In the deep ocean, which is not influenced by anthropogenic emissions, the model results (1.1±0.3 pM) generally agree with the observed present-day total Hg concentration profiles (1.4±0.9 pM). In the surface ocean, observations show average total Hg

  15. Global Earth Response to Loading by Ocean Tide Models

    NASA Technical Reports Server (NTRS)

    Estes, R. H.; Strayer, J. M.

    1979-01-01

    Mathematical and programming techniques to numerically calculate Earth response to global semidiurnal and diurnal ocean tide models were developed. Global vertical crustal deformations were evaluated for M sub 2, S sub 2, N sub 2, K sub 2, K sub 1, O sub 1, and P sub 1 ocean tide loading, while horizontal deformations were evaluated for the M sub 2 tidal load. Tidal gravity calculations were performed for M sub 2 tidal loads, and strain tensor elements were evaluated for M sub 2 loads. The M sub 2 solution used for the ocean tide included the effects of self-gravitation and crustal loading.

  16. Solidifying the lunar magma ocean: Model results and geochronology (Invited)

    NASA Astrophysics Data System (ADS)

    Elkins-Tanton, L. T.; Burgess, S. D.; Meyer, J.; Wisdom, J.

    2009-12-01

    The Moon is posited to have formed by reconsolidation of materials produced during a giant impact with the Earth early in solar system evolution. The young Moon appears to have experienced a magma ocean of some depth, which resulted in the formation of an anorthosite flotation crust. There is no simple way to reconcile W-Hf results for the age of Moon formation, U-Pb and Sm-Nd ages of lunar crustal crystallization, and modeling results for magma ocean solidification. At the beginning of magma ocean solidification the dense iron- and magnesium-rich phases crystallizing from the cooling magma are believed to have sunk to the bottom of the magma ocean. When approximately 80% of the lunar magma ocean solidified, anorthite began to crystallize and float upward through the more dense magma ocean liquid; anorthite will continue to be added to this flotation crust until the last dregs of the magma ocean solidify. The crystallization times of the anorthite in the flotation crust, therefore, could span the range from about 80% solidification to what has been interpreted as the lunar magma ocean solidification age. Models including convection in the remaining magma ocean, conduction through the growing anorthosite lid, and radiation into space indicate that the magma ocean may freeze to the point of anorthosite formation in less than 104 years, and perhaps as little as 103 years. After this brief free-surface cooling period the growth of the anorthosite lid radically slows heat loss, and complete solidification of the magma ocean will require additional tens of millions of years. Young anorthosite crustal ages, far younger than models would predict possible, may be explained by further investigations into the evolution of the lunar orbit. Tidal heating of the anorthosite crust as the young Moon experiences a period of high eccentricity may delay closure of minerals with radiogenic phases; these late-closing minerals will then yield young ages, though they originally formed

  17. Modeling studies of the upper ocean response to a tropical cyclone

    NASA Astrophysics Data System (ADS)

    Morey, Steven L.; Bourassa, Mark A.; Dukhovskoy, Dmitry S.; O'Brien, James J.

    2006-12-01

    A coupled ocean and boundary layer flux numerical modeling system is used to study the upper ocean response to surface heat and momentum fluxes associated with a major hurricane, namely, Hurricane Dennis (July 2005) in the Gulf of Mexico. A suite of experiments is run using this modeling system, constructed by coupling a Navy Coastal Ocean Model simulation of the Gulf of Mexico to an atmospheric flux model. The modeling system is forced by wind fields produced from satellite scatterometer and atmospheric model wind data, and by numerical weather prediction air temperature data. The experiments are initialized from a data assimilative hindcast model run and then forced by surface fluxes with no assimilation for the time during which Hurricane Dennis impacted the region. Four experiments are run to aid in the analysis: one is forced by heat and momentum fluxes, one by only momentum fluxes, one by only heat fluxes, and one with no surface forcing. An equation describing the change in the upper ocean hurricane heat potential due to the storm is developed. Analysis of the model results show that surface heat fluxes are primarily responsible for widespread reduction (0.5° 1.5°C) of sea surface temperature over the inner West Florida Shelf 100 300 km away from the storm center. Momentum fluxes are responsible for stronger surface cooling (2°C) near the center of the storm. The upper ocean heat loss near the storm center of more than 200 MJ/m2 is primarily due to the vertical flux of thermal energy between the surface layer and deep ocean. Heat loss to the atmosphere during the storm’s passage is approximately 100 150 MJ/m2. The upper ocean cooling is enhanced where the preexisting mixed layer is shallow, e.g., within a cyclonic circulation feature, although the heat flux to the atmosphere in these locations is markedly reduced.

  18. On the dependence of hindcast skill on ocean thermodynamics in a coupled ocean-atmosphere model

    SciTech Connect

    Kleeman, R. )

    1993-11-01

    Three different mechanisms for the generation of ENSO SST anomalies within a simplified tropical Pacific Ocean model are examined: thermocline depth changes, Ekman-induced upwelling anomalies, and zonal advection changes. The effect of varying the relative influence of these terms on the realism of tropical pacific coupled models is analyzed. The principal tool used to assess such realism is hindcast skill, with forced ocean and oscillatory behavior also being examined. Of the mechanisms considered, thermocline perturbations are shown to be crucially important for high coupled-model hindcast skills. Furthermore, it is concluded that the realism of the model (as measured by hindcast skill) deteriorates markedly when the influence on SST of Ekman upwelling becomes greater than a small fraction of the thermocline influence. This provides strong evidence for the hypothesis that Ekman upwelling anomalies (which are essentially a local response to wind stress anomalies) have only a small influence on the creation of real world SST anomalies. The implications of this latter point for coupled models involving ocean general circulation models is briefly discussed. It is also demonstrated that western boundary reflections provide a vital role by means of a negative feedback in ensuring realistic performance. The hindcast skill (as measured by NINO3 anomaly correlation) demonstrated by a model involving only the thermocline mechanism can be tuned to exceed that of the benchmark Cane and Zebiak model for hindcast lags up to 7 months (from 7 to 12 months the model skills are roughly equal). 47 refs., 32 figs.

  19. The Southern Ocean Carbon and Climate Observations and Modeling Program (SOCCOM)

    NASA Astrophysics Data System (ADS)

    Russell, Joellen

    2016-04-01

    SOCCOM is a 6-year observational and modeling research program focused on the role of the Southern Ocean in the anthropogenic carbon budget, ocean biogeochemistry, and climate change. The operational goal of SOCCOM is to deploy nearly 200 Argo-compatible biogeochemically-sensored (BGC) profiling floats equipped with pH, oxygen, nitrate and bio-optical sensors throughout the Southern Ocean waters south of 30°S. These climate-ready BGC-floats are calibrated at the time of deployment by high accuracy biogeochemical measurements, and they operate year around, including in ice-covered waters. The data from the BGC-floats is being assimilated by a Southern Ocean State Estimate (SOSE) model that incorporates biogeochemical processes, and this gridded SOSE output is used to constrain high-resolution coupled atmosphere-ocean model simulations designed to both increase our understanding of Southern Ocean processes and to reduce the uncertainty of projections of the future trajectory of the Earth's carbon, climate and biogeochemistry. We will present an overview of the organization and recent results of SOCCOM as well as the exciting next steps being developed.

  20. Interannual variability of CFC-11 absorption by the ocean: an offline model study

    NASA Astrophysics Data System (ADS)

    Valsala, Vinu; Alsibai, Hayyan M.; Ikeda, Motoyoshi; Maksyutov, Shamil

    2011-04-01

    The global ocean Chlorofluorocarbon (CFC-11) was simulated in an offline model driven by re-analysis ocean currents in order to identify the mechanisms of interannual to interdecadal variability of air-sea CFC fluxes. The model was forced with the observed anthropogenic perturbations of atmospheric CFC-11 from the post industrial period (1938) following the OCMIP-II flux protocols along with the observed winds from 1960 to 1999 in the formulation of surface gas exchanges. The model ocean CFC-11 inventories, at the end of 1990s, accounted approximately 1% of the total atmospheric CFC-11, which is consistent with the corresponding observations. The mid-to-high latitude oceans were venue for strong (weak) oceanic sinks (sources) of CFC-11 during the winter (summer) months. The Southern Ocean (south of 40°S) and the North Atlantic (north of 35°N) provided two largest sinks of CFC-11, through which 31.4 and 14.6% of the global ocean CFC-11 entered, respectively. The eastern tropical Pacific Ocean exhibited large interannual variability of CFC-11 flux with a strong (weak) sink during La Niña (El Niño) years and represented 36% of the global CFC-11 flux variability. The North Atlantic and Southern Ocean were found as regions of large sink efficiency: a capacity to sink more CFC than outsource, although it reduced by 80 and 70%, respectively, in the last 40 years compared to 1960. The sink to source ratio of global ocean CFC-11 fluxes were reduced from 90 to 50% in the last 40 years. This indicates a saturation of CFC in the above-thermocline subsurface that makes the upper ocean less efficient in absorbing CFC in recent decades. A positive trend in CFC sink is now limited to the Southern Ocean, central tropical Pacific and western boundary current regions which possess active upwelling of old water with long time since last atmospheric contact. However, a globally averaged trend was a reduced CFC-11 sink, by emitting 30% of the total ocean CFC-11 that was absorbed

  1. Seasonal heat and freshwater cycles in the Arctic Ocean in CMIP5 coupled models

    NASA Astrophysics Data System (ADS)

    Ding, Yanni; Carton, James A.; Chepurin, Gennady A.; Steele, Michael; Hakkinen, Sirpa

    2016-04-01

    This study examines the processes governing the seasonal response of the Arctic Ocean and sea ice to surface forcings as they appear in historical simulations of 14 Coupled Model Intercomparison Project Phase 5 coupled climate models. In both models and observations, the seasonal heat budget is dominated by a local balance between net surface heating and storage in the heat content of the ocean and in melting/freezing of sea ice. Observations suggest ocean heat storage is more important than sea ice melt, while in most of these models, sea ice melt dominates. Seasonal horizontal heat flux divergence driven by the seasonal cycle of volume transport is only important locally. In models and observations, the dominant terms in the basin-average seasonal freshwater budget are the storages of freshwater between the ocean and sea ice, and the exchange between the two. The largest external source term is continental discharge in early summer, which is an order of magnitude smaller. The appearance of sea ice (extent and volume) and also ocean stratification in both the heat and freshwater budgets provides two links between the budgets and provides two mechanisms for feedback. One consequence of such an interaction is the fact that models with strong/weak seasonal surface heating also have strong/weak seasonal haline and temperature stratification.

  2. Numerical simulation of the Gulf Stream and Mid-Ocean eddies

    NASA Technical Reports Server (NTRS)

    Semtner, A. J., Jr.; Mintz, Y.

    1977-01-01

    Oceanographic field measurements have revealed intense, transient mesoscale motions in many parts of the world ocean. The circulation of the western North Atlantic, considered in the present study as a rectangular basin, is simulated with a primitive equation model that has five levels and a horizontal grid size of 37 km. The model ocean is driven by a 2.5 gyre pattern of steady zonal wind stress and by a Newtonian-type surface heating. Two cases are considered: the first uses a Laplacian formulation for the subgrid-scale lateral diffusions of heat and momentum; the second uses a highly scale-selective biharmonic formulation for these diffusions. An analysis of the heat transport, in the biharmonic experiment, shows that the horizontal transport of heat by eddies is much larger than the subgrid-scale horizontal heat diffusion. In the Gulf Stream region, the eddy heat transport is comparable to the effect of a lateral diffusion coefficient of 10 to the 7th sq cm/s.

  3. Coupling of a regional atmospheric model (RegCM3) and a regional oceanic model (FVCOM) over the maritime continent

    NASA Astrophysics Data System (ADS)

    Wei, Jun; Malanotte-Rizzoli, Paola; Eltahir, Elfatih A. B.; Xue, Pengfei; Xu, Danya

    2014-09-01

    Climatological high resolution coupled climate model simulations for the maritime continent have been carried out using the regional climate model (RegCM) version 3 and the finite volume coastal ocean model (FVCOM) specifically designed to resolve regions characterized by complex geometry and bathymetry. The RegCM3 boundary forcing is provided by the EMCWF-ERA40 re-analysis. FVCOM is embedded in the Global MITgcm which provides boundary forcing. The domain of the coupled regional model covers the entire South China Sea with its through-flow, the entire Indonesian archipelago with the Indonesian through-flow (ITF) and includes a large region in the western Pacific and eastern Indian oceans. The coupled model is able to provide stable and realistic climatological simulations for a specific decade of atmospheric-oceanic variables without flux correction. The major focus of this work is on oceanic properties. First, the coupled simulation is assessed against ocean-only simulations carried out under two different sets of air-sea heat fluxes. The first set, provided by the MITgcm, is proved to be grossly deficient as the heat fluxes are evaluated by a two-dimensional, zonally averaged atmosphere and the simulated SST have anomalous cold biases. Hence the MITgcm fluxes are discarded. The second set, the NCEP re-analysis heat fluxes, produces a climatological evolution of the SST with an average cold bias of ~-0.8 °C. The coupling eliminates the cold bias and the coupled SST evolution is in excellent agreement with the analogous evolution in the SODA re-analysis data. The detailed comparison of oceanic circulation properties with the International Nusantara Stratification and Transport observations shows that the coupled simulation produces the best estimate of the total ITF transport through the Makassar strait while the transports of three ocean-only simulations are all underestimated. The annual cycle of the transport is also very well reproduced. The coupling also

  4. Profiles of ocean surface heating (POSH): A new model of upper ocean diurnal warming

    NASA Astrophysics Data System (ADS)

    Gentemann, Chelle L.; Minnett, Peter J.; Ward, Brian

    2009-07-01

    Shipboard radiometric measurements of diurnal warming at the ocean surface and profiles through the diurnal thermocline were utilized to assess the temporal and vertical variability and to develop a new physics-based model of near-surface warming. The measurements and modeled diurnal warming were compared, with the goal of comprehensively evaluating differences between the data and model results. On the basis of these results, the diurnal model was refined while attempting to maintain agreement with the measurements. Simplified bulk models commonly do not provide information on the vertical structure within the warm layer, but this new model predicts the vertical temperature profile within the diurnal thermocline using an empirically derived function dependent on wind speed. The vertical profile of temperature provides both a straightforward methodology for modeling differences due to diurnal warming between measurements made at different depths (e.g., in situ measurements at various depths and measurements of the surface temperatures by satellite radiometers) and information on upper ocean thermal structure. Additionally, the model estimates of diurnal warming at the ocean surface are important for air-sea heat and gas flux calculations, blending satellite sea surface temperature fields, and air-sea interaction studies.

  5. Simulation of impact of oil spill in the ocean--a case study of Arabian Gulf.

    PubMed

    Verma, Parikshit; Wate, Satish R; Devotta, Sukumar

    2008-11-01

    To meet the growing energy demand worldwide, oil and gas exploration and production activities have increased rapidly both in onshore and offshore areas. The produced oil from the ocean bed is transported onshore either by ship or pipeline. This has increased the risk of oil spill in the coastal area. In order to prepare an emergency preparedness plan and to assess the magnitude of risk involved in transporting and offloading oil, oil spill simulation studies play an important role. This paper describes a simulation of oil spill in coastal bay of Arabian Gulf where new developments are taking place using MIKE 21 model. The developments include a diesel based thermal power plant near Sir Baniyas Island, which is an ecological fragile area. Based on the project activity, two probable scenarios, one for diesel leak (250 m3/h) for 1 h and the other for instantaneous spill (500 m3) are considered. The MIKE 21 model was calibrated for hydrodynamics using measured field data followed by diesel-spill simulation to track its movement in the Arabian Gulf. The results for both leak and instantaneous spill indicate that spilled diesel will not move towards the Sir Banyas Island and more than 45% of the diesel will be evaporated within 48 h of oil spill. Based on the results, a clean up and contingency plan is proposed to mitigate the adverse impacts arising due to diesel spill in the study area.

  6. Application of the generalized vertical coordinate ocean model for better representing satellite data

    NASA Technical Reports Server (NTRS)

    Song, Y. T.

    2002-01-01

    It is found that two adaptive parametric functions can be introduced into the basic ocean equations for utilizing the optimal or hybrid features of commonly used z-level, terrain- following, isopycnal, and pressure coordinates in numerical ocean models. The two parametric functions are formulated by combining three techniques: the arbitrary vertical coordinate system of Kasahara (1 974), the Jacobian pressure gradient formulation of Song (1 998), and a newly developed metric factor that permits both compressible (non-Boussinesq) and incompressible (Boussinesq) approximations. Based on the new formulation, an adaptive modeling strategy is proposed and a staggered finite volume method is designed to ensure conservation of important physical properties and numerical accuracy. Implementation of the combined techniques to SCRUM (Song and Haidvogel1994) shows that the adaptive modeling strategy can be applied to any existing ocean model without incurring computational expense or altering the original numerical schemes. Such a generalized coordinate model is expected to benefit diverse ocean modelers for easily choosing optimal vertical structures and sharing modeling resources based on a common model platform. Several representing oceanographic problems with different scales and characteristics, such as coastal canyons, basin-scale circulation, and global ocean circulation, are used to demonstrate the model's capability for multiple applications. New results show that the model is capable of simultaneously resolving both Boussinesq and non-Boussinesq, and both small- and large-scale processes well. This talk will focus on its applications of multiple satellite sensing data in eddy-resolving simulations of Asian Marginal Sea and Kurosio. Attention will be given to how Topex/Poseidon SSH, TRMM SST; and GRACE ocean bottom pressure can be correctly represented in a non- Boussinesq model.

  7. Modeling Abrupt Change in Global Sea Level Arising from Ocean - Ice-Sheet Interaction

    SciTech Connect

    Holland, David M

    2011-09-24

    It is proposed to develop, validate, and apply a coupled ocean ice-sheet model to simulate possible, abrupt future change in global sea level. This research is to be carried out collaboratively between an academic institute and a Department of Energy Laboratory (DOE), namely, the PI and a graduate student at New York University (NYU) and climate model researchers at the Los Alamos National Laboratory (LANL). The NYU contribution is mainly in the area of incorporating new physical processes into the model, while the LANL efforts are focused on improved numerics and overall model development. NYU and LANL will work together on applying the model to a variety of modeling scenarios of recent past and possible near-future abrupt change to the configuration of the periphery of the major ice sheets. The project's ultimate goal is to provide a robust, accurate prediction of future global sea level change, a feat that no fully-coupled climate model is currently capable of producing. This proposal seeks to advance that ultimate goal by developing, validating, and applying a regional model that can simulate the detailed processes involved in sea-level change due to ocean ice-sheet interaction. Directly modeling ocean ice-sheet processes in a fully-coupled global climate model is not a feasible activity at present given the near-complete absence of development of any such causal mechanism in these models to date.

  8. Effects of vertical shear in modelling horizontal oceanic dispersion

    NASA Astrophysics Data System (ADS)

    Lanotte, A. S.; Corrado, R.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

    2016-02-01

    The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ˜ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

  9. Numerical wind speed simulation model

    SciTech Connect

    Ramsdell, J.V.; Athey, G.F.; Ballinger, M.Y.

    1981-09-01

    A relatively simple stochastic model for simulating wind speed time series that can be used as an alternative to time series from representative locations is described in this report. The model incorporates systematic seasonal variation of the mean wind, its standard deviation, and the correlation speeds. It also incorporates systematic diurnal variation of the mean speed and standard deviation. To demonstrate the model capabilities, simulations were made using model parameters derived from data collected at the Hanford Meteorology Station, and results of analysis of simulated and actual data were compared.

  10. The sources of Antarctic bottom water in a global ice ocean model

    NASA Astrophysics Data System (ADS)

    Goosse, Hugues; Campin, Jean-Michel; Tartinville, Benoı̂t

    Two mechanisms contribute to the formation of Antarctic bottom water (AABW). The first, and probably the most important, is initiated by the brine released on the Antarctic continental shelf during ice formation which is responsible for an increase in salinity. After mixing with ambient water at the shelf break, this salty and dense water sinks along the shelf slope and invades the deepest part of the global ocean. For the second one, the increase of surface water density is due to strong cooling at the ocean-atmosphere interface, together with a contribution from brine release. This induces deep convection and the renewal of deep waters. The relative importance of these two mechanisms is investigated in a global coupled ice-ocean model. Chlorofluorocarbon (CFC) concentrations simulated by the model compare favourably with observations, suggesting a reasonable deep water ventilation in the Southern Ocean, except close to Antarctica where concentrations are too high. Two artificial passive tracers released at surface on the Antarctic continental shelf and in the open-ocean allow to show clearly that the two mechanisms contribute significantly to the renewal of AABW in the model. This indicates that open-ocean convection is overestimated in our simulation. Additional experiments show that the amount of AABW production due to the export of dense shelf waters is quite sensitive to the parameterisation of the effect of downsloping and meso-scale eddies. Nevertheless, shelf waters always contribute significantly to deep water renewal. Besides, increasing the P.R. Gent, J.C. McWilliams [Journal of Physical Oceanography 20 (1990) 150-155] thickness diffusion can nearly suppress the AABW formation by open-ocean convection.

  11. A framework to quantify uncertainty in simulations of oil transport in the ocean

    NASA Astrophysics Data System (ADS)

    Gonçalves, Rafael C.; Iskandarani, Mohamed; Srinivasan, Ashwanth; Thacker, W. Carlisle; Chassignet, Eric; Knio, Omar M.

    2016-04-01

    An uncertainty quantification framework is developed for the DeepC Oil Model based on a nonintrusive polynomial chaos method. This allows the model's output to be presented in a probabilistic framework so that the model's predictions reflect the uncertainty in the model's input data. The new capability is illustrated by simulating the far-field dispersal of oil in a Deepwater Horizon blowout scenario. The uncertain input consisted of ocean current and oil droplet size data and the main model output analyzed is the ensuing oil concentration in the Gulf of Mexico. A 1331 member ensemble was used to construct a surrogate for the model which was then mined for statistical information. The mean and standard deviations in the oil concentration were calculated for up to 30 days, and the total contribution of each input parameter to the model's uncertainty was quantified at different depths. Also, probability density functions of oil concentration were constructed by sampling the surrogate and used to elaborate probabilistic hazard maps of oil impact. The performance of the surrogate was constantly monitored in order to demarcate the space-time zones where its estimates are reliable.

  12. Steady-state and transient modeling of tracer and nutrient distributions in the global ocean

    SciTech Connect

    Stocker, T.F.; Broecker, W.S.

    1993-03-08

    The balance of stable and decaying tracers was incorporated into a latitude-depth ocean circulation model which resolves the major ocean basin and is coupled to an atmospheric energy balance model. The modern distribution of radiocarbon and the analysis of artificial color tracers enabled the census of the deep water masses. We show that good agreement with the observation can be achieved if the surface forcing is modified. The same process could also account for long-term, large-scale changes of the global thermohaline circulation. Uptake rates of carbon are investigated using an inorganic carbon cycle model and performing 2 [times] CO[sub 2]-experiments. We prescribe the industrial evolution of pCO[sub 2] in the atmosphere from 1792 to 1988 and calculate the total flux of carbon into the world ocean. Results are in good agreement with two recent 3-dimensional model simulation. First results using an organic carbon cycle in this model are presented. Changes in the hydrological cycle can stabilize the thermohaline circulation in the Atlantic and enable simulation of climate events resembling the Younger Dryas. By adding the balance of radiocarbon the evolution of its atmospheric concentration is studied during rapid changes of deep ocean ventilation. A resumption of ventilation creates a rapid decrease of atmospheric radiocarbon which is able to mask the natural decay.

  13. Monitoring the Ocean Acoustic Environment: A Model-Based Detection Approach

    SciTech Connect

    Candy, J.V.; Sullivan, E.J.

    2000-03-13

    A model-based approach is applied in the development of a processor designed to passively monitor an ocean acoustic environment along with its associated variations. The technique employs an adaptive, model-based processor embedded in a sequential likelihood detection scheme. The trade-off between state-based and innovations-based monitor designs is discussed, conceptually. The underlying theory for the innovations-based design is briefly developed and applied to a simulated data set.

  14. Reproducibility and Transparency in Ocean-Climate Modeling

    NASA Astrophysics Data System (ADS)

    Hannah, N.; Adcroft, A.; Hallberg, R.; Griffies, S. M.

    2015-12-01

    Reproducibility is a cornerstone of the scientific method. Within geophysical modeling and simulation achieving reproducibility can be difficult, especially given the complexity of numerical codes, enormous and disparate data sets, and variety of supercomputing technology. We have made progress on this problem in the context of a large project - the development of new ocean and sea ice models, MOM6 and SIS2. Here we present useful techniques and experience.We use version control not only for code but the entire experiment working directory, including configuration (run-time parameters, component versions), input data and checksums on experiment output. This allows us to document when the solutions to experiments change, whether due to code updates or changes in input data. To avoid distributing large input datasets we provide the tools for generating these from the sources, rather than provide raw input data.Bugs can be a source of non-determinism and hence irreproducibility, e.g. reading from or branching on uninitialized memory. To expose these we routinely run system tests, using a memory debugger, multiple compilers and different machines. Additional confidence in the code comes from specialised tests, for example automated dimensional analysis and domain transformations. This has entailed adopting a code style where we deliberately restrict what a compiler can do when re-arranging mathematical expressions.In the spirit of open science, all development is in the public domain. This leads to a positive feedback, where increased transparency and reproducibility makes using the model easier for external collaborators, who in turn provide valuable contributions. To facilitate users installing and running the model we provide (version controlled) digital notebooks that illustrate and record analysis of output. This has the dual role of providing a gross, platform-independent, testing capability and a means to documents model output and analysis.

  15. North and equatorial Pacific Ocean circulation in the CORE-II hindcast simulations

    NASA Astrophysics Data System (ADS)

    Tseng, Yu-heng; Lin, Hongyang; Chen, Han-ching; Thompson, Keith; Bentsen, Mats; Böning, Claus W.; Bozec, Alexandra; Cassou, Christophe; Chassignet, Eric; Chow, Chun Hoe; Danabasoglu, Gokhan; Danilov, Sergey; Farneti, Riccardo; Fogli, Pier Giuseppe; Fujii, Yosuke; Griffies, Stephen M.; Ilicak, Mehmet; Jung, Thomas; Masina, Simona; Navarra, Antonio; Patara, Lavinia; Samuels, Bonita L.; Scheinert, Markus; Sidorenko, Dmitry; Sui, Chung-Hsiung; Tsujino, Hiroyuki; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yeager, Steve G.

    2016-08-01

    We evaluate the mean circulation patterns, water mass distributions, and tropical dynamics of the North and Equatorial Pacific Ocean based on a suite of global ocean-sea ice simulations driven by the CORE-II atmospheric forcing from 1963-2007. The first three moments (mean, standard deviation and skewness) of sea surface height and surface temperature variability are assessed against observations. Large discrepancies are found in the variance and skewness of sea surface height and in the skewness of sea surface temperature. Comparing with the observation, most models underestimate the Kuroshio transport in the Asian Marginal seas due to the missing influence of the unresolved western boundary current and meso-scale eddies. In terms of the Mixed Layer Depths (MLDs) in the North Pacific, the two observed maxima associated with Subtropical Mode Water and Central Mode Water formation coalesce into a large pool of deep MLDs in all participating models, but another local maximum associated with the formation of Eastern Subtropical Mode Water can be found in all models with different magnitudes. The main model bias of deep MLDs results from excessive Subtropical Mode Water formation due to inaccurate representation of the Kuroshio separation and of the associated excessively warm and salty Kuroshio water. Further water mass analysis shows that the North Pacific Intermediate Water can penetrate southward in most models, but its distribution greatly varies among models depending not only on grid resolution and vertical coordinate but also on the model dynamics. All simulations show overall similar large scale tropical current system, but with differences in the structures of the Equatorial Undercurrent. We also confirm the key role of the meridional gradient of the wind stress curl in driving the equatorial transport, leading to a generally weak North Equatorial Counter Current in all models due to inaccurate CORE-II equatorial wind fields. Most models show a larger

  16. Computationally Efficient Numerical Model for the Evolution of Directional Ocean Surface Waves

    NASA Astrophysics Data System (ADS)

    Malej, M.; Choi, W.; Goullet, A.

    2011-12-01

    The main focus of this work has been the asymptotic and numerical modeling of weakly nonlinear ocean surface wave fields. In particular, a development of an efficient numerical model for the evolution of nonlinear ocean waves, including extreme waves known as Rogue/Freak waves, is of direct interest. Due to their elusive and destructive nature, the media often portrays Rogue waves as unimaginatively huge and unpredictable monsters of the sea. To address some of these concerns, derivations of reduced phase-resolving numerical models, based on the small wave steepness assumption, are presented and their corresponding numerical simulations via Fourier pseudo-spectral methods are discussed. The simulations are initialized with a well-known JONSWAP wave spectrum and different angular distributions are employed. Both deterministic and Monte-Carlo ensemble average simulations were carried out. Furthermore, this work concerns the development of a new computationally efficient numerical model for the short term prediction of evolving weakly nonlinear ocean surface waves. The derivations are originally based on the work of West et al. (1987) and since the waves in the ocean tend to travel primarily in one direction, the aforementioned new numerical model is derived with an additional assumption of a weak transverse dependence. In turn, comparisons of the ensemble averaged randomly initialized spectra, as well as deterministic surface-to-surface correlations are presented. The new model is shown to behave well in various directional wave fields and can potentially be a candidate for computationally efficient prediction and propagation of extreme ocean surface waves - Rogue/Freak waves.

  17. Global ocean biogeochemistry model HAMOCC: Model architecture and performance as component of the MPI-Earth system model in different CMIP5 experimental realizations

    NASA Astrophysics Data System (ADS)

    Ilyina, Tatiana; Six, Katharina D.; Segschneider, Joachim; Maier-Reimer, Ernst; Li, Hongmei; NúñEz-Riboni, Ismael

    2013-06-01

    Ocean biogeochemistry is a novel standard component of fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiments which project future climate change caused by anthropogenic emissions of greenhouse gases. Of particular interest here is the evolution of the oceanic sink of carbon and the oceanic contribution to the climate-carbon cycle feedback loop. The Hamburg ocean carbon cycle model (HAMOCC), a component of the Max Planck Institute for Meteorology Earth system model (MPI-ESM), is employed to address these challenges. In this paper we describe the version of HAMOCC used in the CMIP5 experiments (HAMOCC 5.2) and its implementation in the MPI-ESM to provide a documentation and basis for future CMIP5-related studies. Modeled present day distributions of biogeochemical variables calculated in two different horizontal resolutions compare fairly well with observations. Statistical metrics indicate that the model performs better at the ocean surface and worse in the ocean interior. There is a tendency for improvements in the higher resolution model configuration in representing deeper ocean variables; however, there is little to no improvement at the ocean surface. An experiment with interactive carbon cycle driven by emissions of CO2 produces a 25% higher variability in the oceanic carbon uptake over the historical period than the same model forced by prescribed atmospheric CO2 concentrations. Furthermore, a climate warming of 3.5 K projected at atmospheric CO2 concentration of four times the preindustrial value, reduced the atmosphere-ocean CO2 flux by 1 GtC yr-1. Overall, the model shows consistent results in different configurations, being suitable for the type of simulations required within the CMIP5 experimental design.

  18. Effect of improved subgrid scale transport of tracers on uptake of bomb radiocarbon in the GFDL Ocean General Circulation Model

    NASA Astrophysics Data System (ADS)

    Duffy, P. B.; Eltgroth, P.; Bourgeois, A. J.; Caldeira, K.

    1995-05-01

    We show that the Gent-McWilliams tracer transport parameterization greatly improves the ability of the GFDL ocean general circulation model to simulate vertical profiles of both temperature and bomb radiocarbon with a single set of model parameter values. This parameterization, which includes new advection terms as well as isopycnal mixing, has previously been shown to greatly improve simulated temperature fields. Here, we show that it does not markedly affect the already good simulation of oceanic absorption of bomb radiocarbon, and discuss the reasons for this result.

  19. How the Ocean personality model affects the perception of crowds.

    PubMed

    Durupinar, F; Pelechano, N; Allbeck, J M; Gudukbay, Ugur; Badler, N I

    2011-01-01

    This approach extends the HiDAC (High-Density Autonomous Crowds) system by providing each agent with a personality model based on the Ocean (openness, conscientiousness, extroversion, agreeableness, and neuroticism) personality model. Each personality trait has an associated nominal behavior. Specifying an agent's personality leads to an automation of low-level parameter tuning.

  20. A model for the probability density function of downwelling irradiance under ocean waves.

    PubMed

    Shen, Meng; Xu, Zao; Yue, Dick K P

    2011-08-29

    We present a statistical model that analytically quantifies the probability density function (PDF) of the downwelling light irradiance under random ocean waves modeling the surface as independent and identically distributed flat facets. The model can incorporate the separate effects of surface short waves and volume light scattering. The theoretical model captures the characteristics of the PDF, from skewed to near-Gaussian shape as the depth increases from shallow to deep water. The model obtains a closed-form asymptotic for the probability that diminishes at a rate between exponential and Gaussian with increasing extreme values. The model is validated by comparisons with existing field measurements and Monte Carlo simulation.

  1. Direct numerical simulation of an iron rain in the magma ocean

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Labrosse, S.; Kurita, K.

    2010-01-01

    Core formation in terrestrial planets is a complex process, possibly involving several mechanisms. This paper presents a direct numerical simulation of one of these, the separation of an emulsion of metal in a magma ocean. The model, using a fully Lagrangian approach called the moving particle semi-implicit method, solves the equations of fluid dynamics, including a proper treatment of surface tension. It allows investigation of the balances controlling the distribution of drop size and velocity, in both two- and three-dimensional situations. A scaling analysis where buoyancy is balanced by both surface tension and inertia correctly predicts the average values in these quantities. The full calculation gives an average drop radius of 1.5 cm falling at a velocity of about 30 cm s-1. Analysis of the full distribution remains interesting and shows that a significant part of the smallest droplets is entrained upward by the return flow in molten silicate and might be entrained by succeeding thermal convection. In addition, we investigate the conversion of gravitational energy into viscous heating and the thermal equilibration between both phases. We find that viscous heating is essentially produced at the surface of iron drops and that thermal equilibration is dominated by advection. Scaling thermal diffusion to chemical diffusion leads to the estimation that the latter would happen in less than 100 m in the magma ocean.

  2. Simulated impacts of the South Atlantic Ocean Dipole on summer precipitation at the Guinea Coast

    NASA Astrophysics Data System (ADS)

    Nnamchi, Hyacinth C.; Li, Jianping; Kang, In-Sik; Kucharski, Fred

    2013-08-01

    An intermediate complexity atmospheric general circulation model has been used to investigate the influence of the South Atlantic Ocean (SAO) dipole (SAOD) on summer precipitation over the Guinea Coast of West Africa. Two ensemble integrations in which idealized but realistic SAOD-type sea surface temperature (SST) anomaly is prescribed only in the SAO, and then globally are performed and inter-compared. Consistently, above (below) the average precipitation is simulated over the Guinea Coast during the positive (negative) phase of the SAOD. Comparison of the two set of experiments reveal that in its active years, the SAOD is a dominant mechanism that shapes the spatial character of summer precipitation at the Guinea coast, the global SST variability merely slightly moderate its effects. During the SAOD, cool SST anomaly in the extra-tropical SAO off the Brazil-Uruguay-Argentina coast gives rise to suppressed convection and mass divergence. In turn, the subsidence tends to amplify the sub-tropical arm of anomalous Hadley-type circulation and consequently large scale convection and mass flux convergence in the equatorial Atlantic Ocean/Gulf of Guinea region bordering on the coastal fringes of West Africa. Precipitation is therefore increased at the Guinea Coast.

  3. CMIP5 historical simulations (1850-2012) with GISS ModelE2

    NASA Astrophysics Data System (ADS)

    Miller, Ron L.; Schmidt, Gavin A.; Nazarenko, Larissa S.; Tausnev, Nick; Bauer, Susanne E.; DelGenio, Anthony D.; Kelley, Max; Lo, Ken K.; Ruedy, Reto; Shindell, Drew T.; Aleinov, Igor; Bauer, Mike; Bleck, Rainer; Canuto, Vittorio; Chen, Yonghua; Cheng, Ye; Clune, Thomas L.; Faluvegi, Greg; Hansen, James E.; Healy, Richard J.; Kiang, Nancy Y.; Koch, Dorothy; Lacis, Andy A.; LeGrande, Allegra N.; Lerner, Jean; Menon, Surabi; Oinas, Valdar; Pérez García-Pando, Carlos; Perlwitz, Jan P.; Puma, Michael J.; Rind, David; Romanou, Anastasia; Russell, Gary L.; Sato, Makiko; Sun, Shan; Tsigaridis, Kostas; Unger, Nadine; Voulgarakis, Apostolos; Yao, Mao-Sung; Zhang, Jinlun

    2014-06-01

    Observations of climate change during the CMIP5 extended historical period (1850-2012) are compared to trends simulated by six versions of the NASA Goddard Institute for Space Studies ModelE2 Earth System Model. The six models are constructed from three versions of the ModelE2 atmospheric general circulation model, distinguished by their treatment of atmospheric composition and the aerosol indirect effect, combined with two ocean general circulation models, HYCOM and Russell. Forcings that perturb the model climate during the historical period are described. Five-member ensemble averages from each of the six versions of ModelE2 simulate trends of surface air temperature, atmospheric temperature, sea ice and ocean heat content that are in general agreement with observed trends, although simulated warming is slightly excessive within the past decade. Only simulations that include increasing concentrations of long-lived greenhouse gases match the warming observed during the twentieth century. Differences in twentieth-century warming among the six model versions can be attributed to differences in climate sensitivity, aerosol and ozone forcing, and heat uptake by the deep ocean. Coupled models with HYCOM export less heat to the deep ocean, associated with reduced surface warming in regions of deepwater formation, but greater warming elsewhere at high latitudes along with reduced sea ice. All ensembles show twentieth-century annular trends toward reduced surface pressure at southern high latitudes and a poleward shift of the midlatitude westerlies, consistent with observations.

  4. CMIP5 Historical Simulations (1850-2012) with GISS ModelE2

    NASA Technical Reports Server (NTRS)

    Miller, Ronald Lindsay; Schmidt, Gavin A.; Nazarenko, Larissa S.; Tausnev, Nick; Bauer, Susanne E.; DelGenio, Anthony D.; Kelley, Max; Lo, Ken K.; Ruedy, Reto; Shindell, Drew T.; Aleinov, Igor; Bauer, Mike; Bleck, Rainer; Canuto, Vittorio; Chen, Yonghua; Cheng, Ye; Clune, Thomas L.; Faluvegi, Greg; Healy, Richard J.; Kiang, Nancy Y.; Lacis, Andy A.; LeGrande, Allegra N.; Lerner, Jean; Rind, David; Russell, Gary L.

    2014-01-01

    Observations of climate change during the CMIP5 extended historical period (1850-2012) are compared to trends simulated by six versions of the NASA Goddard Institute for Space Studies ModelE2 Earth System Model. The six models are constructed from three versions of the ModelE2 atmospheric general circulation model, distinguished by their treatment of atmospheric composition and the aerosol indirect effect, combined with two ocean general circulation models, HYCOM and Russell. Forcings that perturb the model climate during the historical period are described. Five-member ensemble averages from each of the six versions of ModelE2 simulate trends of surface air temperature, atmospheric temperature, sea ice and ocean heat content that are in general agreement with observed trends, although simulated warming is slightly excessive within the past decade. Only simulations that include increasing concentrations of long-lived greenhouse gases match the warming observed during the twentieth century. Differences in twentieth-century warming among the six model versions can be attributed to differences in climate sensitivity, aerosol and ozone forcing, and heat uptake by the deep ocean. Coupled models with HYCOM export less heat to the deep ocean, associated with reduced surface warming in regions of deepwater formation, but greater warming elsewhere at high latitudes along with reduced sea ice. All ensembles show twentieth-century annular trends toward reduced surface pressure at southern high latitudes and a poleward shift of the midlatitude westerlies, consistent with observations.

  5. Joint modeling and simulation system

    NASA Astrophysics Data System (ADS)

    Boyer, Richard T.; McQuay, William K.

    1993-08-01

    The defense budget is shrinking. Weapon systems are getting more complex. Test requirements are increasing. The training and war gaming scenarios are getting more demanding as fielded systems and training simulators are integrated to support combined arms training. To cope with these requirements and still stay within the budget, the Department of Defense is relying on modeling and simulation. The state of the modeling and simulation (M&S) art has advanced to the point where a user can now create incredibly realistic, extremely detailed models which can augment test and evaluation, support the acquisition process, enhance training and war gaming, facilitate intelligence gathering, and support detailed engineering.

  6. Miocene ocean circulation inferred from marine carbon cycle modeling combined with benthic isotope records

    NASA Astrophysics Data System (ADS)

    Butzin, Martin; Lohmann, Gerrit; Bickert, Torsten

    2011-02-01

    In a modeling sensitivity study we investigate the evolution of the ocean circulation and of marine carbon isotope (δ13C) records during the Miocene (about 23-5 million years ago). For this purpose we ran an ocean-circulation carbon cycle model of intermediate complexity (Large Scale Geostrophic- Hamburg Ocean Carbon Cycle Model, version 2s) exploring various seaway configurations. Our investigations confirm that the Central American Seaway played a decisive role in the history of the Miocene ocean circulation. In simulations with a deep Central American Seaway (depth range 1-3 km), typical for the early to middle Miocene, deep water production in the North Atlantic is absent or weak, while the meridional overturning circulation is dominated by water mass formation in the Southern Ocean. Deep water formation in the North Atlantic begins when the Central American Seaway shoals to a few hundreds of meters, which is typical for the late Miocene. Our results do not support ideas that the mid-Miocene closing of the Eastern Tethys contributed to Antarctic glaciation. On the other hand, we find some water exchange between the Indian Ocean and the Atlantic via the Eastern Tethys during the early Miocene. Our model results for the Atlantic meridional overturning circulation and for Atlantic δ13C during the late Miocene are largely independent from depth variations of the Greenland-Scotland Ridge. To a large extent, the evolution of Miocene deep-sea δ13C records can be explained with large-scale ocean circulation changes. Our model-data comparison for the middle and early Miocene suggests that during the early Neogene the seaway effect on benthic δ13C may have been superimposed by further factors such as climate regime shifts and/or terrestrial carbon cycle changes.

  7. North Pacific Mesoscale Coupled Air-Ocean Simulations Compared with Observations

    SciTech Connect

    Cerovecki, Ivana; McClean, Julie; Koracin, Darko

    2014-11-14

    The overall objective of this study was to improve the representation of regional ocean circulation in the North Pacific by using high resolution atmospheric forcing that accurately represents mesoscale processes in ocean-atmosphere regional (North Pacific) model configuration. The goal was to assess the importance of accurate representation of mesoscale processes in the atmosphere and the ocean on large scale circulation. This is an important question, as mesoscale processes in the atmosphere which are resolved by the high resolution mesoscale atmospheric models such as Weather Research and Forecasting (WRF), are absent in commonly used atmospheric forcing such as CORE forcing, employed in e.g. the Community Climate System Model (CCSM).

  8. Improved routines to model the ocean carbonate system: mocsy 1.0

    NASA Astrophysics Data System (ADS)

    Orr, J. C.; Epitalon, J.-M.

    2014-05-01

    Software used by modelers to compute ocean carbonate chemistry is often based on code from the Ocean Carbon Cycle Model Intercomparison Project (OCMIP), last revised in 2005. As an update, we offer here new publicly available Fortran 95 routines to model the ocean carbonate system (mocsy). Both codes take as input dissolved inorganic carbon CT and total alkalinity AT, the only two tracers of the ocean carbonate system that are unaffected by changes in temperature and salinity and conservative with respect to mixing, properties that make them ideally suited for ocean carbon models. With the same basic thermodynamic equilibria, both codes compute surface-ocean pCO2 in order to simulate air-sea CO2 fluxes. The mocsy package goes beyond the OCMIP code by computing all other carbonate system variables (e.g., pH, CO32-, and CaCO3 saturation states) and by doing so throughout the water column. Moreover, it avoids three common model approximations: that density is constant, that modeled potential temperature is equivalent to in situ temperature, and that depth is equivalent to pressure. These approximations work well at the surface, but total errors in computed variables grow with depth, e.g., reaching -8 μatm in pCO2, +0.010 in pH, and +0.01 in ΩA at 5000 m. Besides the equilibrium constants recommended for best practices, mocsy also offers users three new options: (1) a recent formulation for total boron that increases its ocean content by 4%, (2) an older formulation for KF common to all other such software, and (3) recent formulations for K1 and K2 designed to also include low-salinity waters. More total boron increases borate alkalinity and reduces carbonate alkalinity, which is calculated as a difference from total alkalinity. As a result, the computed surface pCO2 increases by 4 to 6 μatm, while the computed aragonite saturation horizon (ASH) shallows by 60 m in the North Atlantic and by up to 90 m in the Southern Ocean. Changes due to the new formulation for K1

  9. Data Organization and I/O in a Parallel Ocean Circulation Model

    SciTech Connect

    Ding, Chris H.Q.; He, Yun

    1999-05-01

    We describe an efficient and scalable parallel I/0 strategy for writing out gigabytes of data generated hourly in the ocean model simulations on massively parallel distributed-memory architectures. Working with Modular Ocean Model, using net CIF file system? and implemented on Cray T3E, the strategy speedup I/0 by a factor of 50 in the sequential case. In parallel case, on 8 PEs up to 256 PEs, our implementation writes out most model dynamic fields of about 1GB to a single netCDF file in 65 seconds, independent of the number of processors. The remap-and-write parallel strategy resolves the memory limitation problem and requires minimal collective I/0 capability of the file system. Several critical optimization on memory management and file access are carried out which ensure this scalability and also speedup the numerical simulation due to improved memory management.

  10. Automatic programming of simulation models

    NASA Technical Reports Server (NTRS)

    Schroer, Bernard J.; Tseng, Fan T.; Zhang, Shou X.; Dwan, Wen S.

    1988-01-01

    The objective of automatic programming is to improve the overall environment for describing the program. This improved environment is realized by a reduction in the amount of detail that the programmer needs to know and is exposed to. Furthermore, this improved environment is achieved by a specification language that is more natural to the user's problem domain and to the user's way of thinking and looking at the problem. The goal of this research is to apply the concepts of automatic programming (AP) to modeling discrete event simulation system. Specific emphasis is on the design and development of simulation tools to assist the modeler define or construct a model of the system and to then automatically write the corresponding simulation code in the target simulation language, GPSS/PC. A related goal is to evaluate the feasibility of various languages for constructing automatic programming