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Sample records for advanced circulation model

  1. Demonstration of an advanced circulation fludized bed coal combustor phase 1: Cold model study. Final report

    SciTech Connect

    Govind, R.

    1993-03-20

    It was found that there was a strong dependence of the density profile on the secondary air injection location and that there was a pronounced solid separation from the conveying gas, due to the swirl motion. Furthermore, the swirl motion generated strong internal circulation patterns and higher slip velocities than in the case of nonswirl motion as in an ordinary circulating fluidized bed. Radial solids flux profiles were measured at different axial locations. The general radial profile in a swirling circulating fluidized bed indicated an increased downward flow of solids near the bed walls, and strong variations in radial profiles along the axial height. For swirl numbers less than 0.9, which is typical for swirling circulating fluidized beds, there is no significant increase in erosion due to swirl motion inside the bed. Pending further investigation of swirl motion with combustion, at least from our cold model studies, no disadvantages due to the introduction of swirl motion were discovered.

  2. An advanced computational bioheat transfer model for a human body with an embedded systemic circulation.

    PubMed

    Coccarelli, Alberto; Boileau, Etienne; Parthimos, Dimitris; Nithiarasu, Perumal

    2016-10-01

    In the present work, an elaborate one-dimensional thermofluid model for a human body is presented. By contrast to the existing pure conduction-/perfusion-based models, the proposed methodology couples the arterial fluid dynamics of a human body with a multi-segmental bioheat model of surrounding solid tissues. In the present configuration, arterial flow is included through a network of elastic vessels. More than a dozen solid segments are employed to represent the heat conduction in the surrounding tissues, and each segment is constituted by a multilayered circular cylinder. Such multi-layers allow flexible delineation of the geometry and incorporation of properties of different tissue types. The coupling of solid tissue and fluid models requires subdivision of the arterial circulation into large and small arteries. The heat exchange between tissues and arterial wall occurs by convection in large vessels and by perfusion in small arteries. The core region, including the heart, provides the inlet conditions for the fluid equations. In the proposed model, shivering, sweating, and perfusion changes constitute the basis of the thermoregulatory system. The equations governing flow and heat transfer in the circulatory system are solved using a locally conservative Galerkin approach, and the heat conduction in the surrounding tissues is solved using a standard implicit backward Euler method. To investigate the effectiveness of the proposed model, temperature field evolutions are monitored at different points of the arterial tree and in the surrounding tissue layers. To study the differences due to flow-induced convection effects on thermal balance, the results of the current model are compared against those of the widely used modelling methodologies. The results show that the convection significantly influences the temperature distribution of the solid tissues in the vicinity of the arteries. Thus, the inner convection has a more predominant role in the human body heat

  3. Development of an advanced finite-difference atmospheric general circulation model

    SciTech Connect

    Randall, D.A.

    1992-03-01

    We have proposed to provide and further develop an advanced finite-difference climate model for use in CHAMMP. The model includes advanced parameterizations of cumulus convection, boundary-layer processes, cloud formation, and land-surface vegetation, as well as parameterizations of radiative transfer and gravity wave drag. Postprocessing codes and a user's guide will also be provided. This research is being conducted in collaboration with Professors C.R. Mechoso and A. Arakawa at the University of California at Los Angeles (UCLA). The following research tasks are being carried out in support of CHAMMP: (1) Provide to CHAMMP a base-line finite-difference model and postprocessing codes for further development by the CHAMMP Science Team; (2) Provide to CHAMMP improved model physics to be developed in the course of our research project; (3) Provide to CHAMMP improved computational methods for use in the model; and, (4) Investigate the performance of current and to-be-developed physical parameterizations and computational methods at very high resolution.

  4. An advanced computational bioheat transfer model for a human body with an embedded systemic circulation.

    PubMed

    Coccarelli, Alberto; Boileau, Etienne; Parthimos, Dimitris; Nithiarasu, Perumal

    2016-10-01

    In the present work, an elaborate one-dimensional thermofluid model for a human body is presented. By contrast to the existing pure conduction-/perfusion-based models, the proposed methodology couples the arterial fluid dynamics of a human body with a multi-segmental bioheat model of surrounding solid tissues. In the present configuration, arterial flow is included through a network of elastic vessels. More than a dozen solid segments are employed to represent the heat conduction in the surrounding tissues, and each segment is constituted by a multilayered circular cylinder. Such multi-layers allow flexible delineation of the geometry and incorporation of properties of different tissue types. The coupling of solid tissue and fluid models requires subdivision of the arterial circulation into large and small arteries. The heat exchange between tissues and arterial wall occurs by convection in large vessels and by perfusion in small arteries. The core region, including the heart, provides the inlet conditions for the fluid equations. In the proposed model, shivering, sweating, and perfusion changes constitute the basis of the thermoregulatory system. The equations governing flow and heat transfer in the circulatory system are solved using a locally conservative Galerkin approach, and the heat conduction in the surrounding tissues is solved using a standard implicit backward Euler method. To investigate the effectiveness of the proposed model, temperature field evolutions are monitored at different points of the arterial tree and in the surrounding tissue layers. To study the differences due to flow-induced convection effects on thermal balance, the results of the current model are compared against those of the widely used modelling methodologies. The results show that the convection significantly influences the temperature distribution of the solid tissues in the vicinity of the arteries. Thus, the inner convection has a more predominant role in the human body heat

  5. Modelled Circulation In Storfjorden

    NASA Astrophysics Data System (ADS)

    Skogseth, R.; Asplin, L.

    The model area Storfjorden is situated between the islands Spitsbergen, Barentsöya and Edgeöya at the Svalbard Archipelago. The entrance of Storfjorden is defined by a shallow bank Storfjordbanken and some small islands Tusenöyane in southeast, and by an 115m deep sill at about 76 45' N in the south. Maximum depth in Storfjorden is 190m, which is surrounded by gradually shallower shelves in the north, the east and southeast. A steep bottom slope is present on the western side of Storfjorden. He- leysundet and Freemansundet, two sounds between respectively Spitsbergen and Bar- entsöya, and Barentsöya and Edgeöya, define two narrow and shallow entrances in the north and northeast connecting Storfjorden with the northwestern Barents Sea. Strong tidal currents exist in Heleysundet (4-5ms-1) and Freemansundet (2-3ms-1), but the general circulation in Storfjorden is not well known. The coastal current in Storfjor- den is cyclonic directed into Storfjorden south of Edgeöya from the East Spitsbergen Current and out of Storfjorden south of Spitsbergen where it is called Sørkappstrøm- men. A three-dimensional sigma layered numerical ocean model called Bergen Ocean Model (BOM) was used to simulate the circulation in Storfjorden with Freemansundet opened. Two simulations were carried out, one with heat flux (100 Wm-2) and one without heat flux from the ocean to the atmosphere. The heat flux was applied only in the proper fjord area north of the sill and not outside as a crude approximation of the effects of a polynya in the sea ice cover during winter. Both simulations had a 4km horizontal resolution and 21 sigma layers. The model is forced by winds (from the NCEP reanalyzed fields) and tides. Initial fields are from the DNMI/IMR climatol- ogy. The model simulation without heat flux gave a circulation heavily dependent on tidal forcing, showing strong tidal currents up to 2ms-1 in Freemansundet, between Tusenöyane and on Storfjordbanken southwest of Edgeöya. Earlier

  6. 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.

  7. Development of an advanced finite-difference atmospheric general circulation model. Progress report, September 1, 1991--August 31, 1992

    SciTech Connect

    Randall, D.A.

    1992-03-01

    We have proposed to provide and further develop an advanced finite-difference climate model for use in CHAMMP. The model includes advanced parameterizations of cumulus convection, boundary-layer processes, cloud formation, and land-surface vegetation, as well as parameterizations of radiative transfer and gravity wave drag. Postprocessing codes and a user`s guide will also be provided. This research is being conducted in collaboration with Professors C.R. Mechoso and A. Arakawa at the University of California at Los Angeles (UCLA). The following research tasks are being carried out in support of CHAMMP: (1) Provide to CHAMMP a base-line finite-difference model and postprocessing codes for further development by the CHAMMP Science Team; (2) Provide to CHAMMP improved model physics to be developed in the course of our research project; (3) Provide to CHAMMP improved computational methods for use in the model; and, (4) Investigate the performance of current and to-be-developed physical parameterizations and computational methods at very high resolution.

  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. A blood circulation model for reference man

    SciTech Connect

    Leggett, R.W.; Eckerman, K.F.; Williams, L.R.

    1996-12-31

    A dynamic blood circulation model that predicts the movement and gradual dispersion of a bolus of material in the circulation after its intravenous injection into an adult human. The main purpose of the model is improve the dosimetry of internally deposited radionuclides that decay in the circulation to a significant extent. The model partitions the blood volume into 24 separate organs or tissues, right heart chamber, left heart chamber, pulmonary circulation, arterial outflow to the aorta and large arteries, and venous return via the large veins. Model results were compared to data obtained from injection of carbon 11 labeled carbon monoxide or rubidium 86.

  10. Climate modelling: Northern Hemisphere circulation.

    PubMed

    Gillett, Nathan P

    2005-09-22

    Air pressure at sea level during winter has decreased over the Arctic and increased in the Northern Hemisphere subtropics in recent decades, a change that has been associated with 50% of the Eurasian winter warming observed over the past 30 years, with 60% of the rainfall increase in Scotland and with 60% of the rainfall decrease in Spain. This trend is inconsistent with the simulated response to greenhouse-gas and sulphate-aerosol changes, but it has been proposed that other climate influences--such as ozone depletion--could account for the discrepancy. Here I compare observed Northern Hemisphere sea-level pressure trends with those simulated in response to all the major human and natural climate influences in nine state-of-the-art coupled climate models over the past 50 years. I find that these models all underestimate the circulation trend. This inconsistency suggests that we cannot yet simulate changes in this important property of the climate system or accurately predict regional climate changes.

  11. A blood circulation model for reference man

    SciTech Connect

    Leggett, R.W.; Eckerman, K.F.; Williams, L.R.

    1999-01-01

    This paper describes a dynamic blood circulation model that predicts the movement and gradual dispersal of a bolus of material in the circulation after its intravascular injection into an adult human. The main purpose of the model is to improve the dosimetry of internally deposited radionuclides that decay in the circulation to a significant extent. The total blood volume is partitioned into the blood contents of 24 separate organs or tissues, right heart chambers, left heart chambers, pulmonary circulation, arterial outflow to the systemic tissues (aorta and large arteries), and venous return from the systemic tissues (large veins). As a compromise between physical reality and computational simplicity, the circulation of blood is viewed as a system of first-order transfers between blood pools, with the delay time depending on the mean transit time across the pool. The model allows consideration of incomplete, tissue-dependent extraction of material during passage through the circulation and return of material from tissues to plasma.

  12. An online educational atmospheric global circulation model

    NASA Astrophysics Data System (ADS)

    Navarro, T.; Schott, C.; Forget, F.

    2015-10-01

    As part of online courses on exoplanets of Observatoire de Paris, an online tool designed to vizualise outputs of the Laboratoire de Métérologie Dynamique (LMD) Global Circulation Model (GCM) for various atmospheric circulation regimes has been developed. It includes the possibility for students to visualize 1D and 2D plots along with animations of atmospheric quantities such as temperature, winds, surface pressure, mass flux, etc... from a state-of-the-art model.

  13. Cryogenic helium gas circulation system for advanced characterization of superconducting cables and other devices

    NASA Astrophysics Data System (ADS)

    Pamidi, Sastry; Kim, Chul Han; Kim, Jae-Ho; Crook, Danny; Dale, Steinar

    2012-04-01

    A versatile cryogenic test bed, based on circulating cryogenic helium gas, has been designed, fabricated, and installed at the Florida State University Center for Advanced Power Systems (FSU-CAPS). The test bed is being used to understand the benefits of integrating the cryogenic systems of multiple superconducting power devices. The helium circulation system operates with four sets of cryocooler and heat exchanger combinations. The maximum operating pressure of the system is 2.1 MPa. The efficacy of helium circulation systems in cooling superconducting power devices is evaluated using a 30-m-long simulated superconducting cable in a flexible cryostat. Experiments were conducted at various mass flow rates and a variety of heat load profiles. A 1-D thermal model was developed to understand the effect of the gas flow parameters on the thermal gradients along the cable. Experimental results are in close agreement with the results from the thermal model.

  14. Simple Model of the Circulation.

    ERIC Educational Resources Information Center

    Greenway, Clive A.

    1980-01-01

    Describes a program in BASIC-11 that explores the relationships between various variables in the circulatory system and permits manipulation of several semiindependent variables to model the effects of hemorrhage, drug infusions, etc. A flow chart and accompanying sample printout are provided; the program is listed in the appendix. (CS)

  15. A paleoceanographic circulation and chemistry model

    SciTech Connect

    Southam, J.R. )

    1990-01-09

    We have developed a 3-D circulation and tracer field model for paleoceanographic applications. The development of the model was motivated by the desire to explore Cretaceous Oceanic Anoxic Events and ocean chemistry during glacial and interglacial modes of circulation. The bulk of paleoceanographic data is the consequences of biological processes operating in ancient oceans. This type of data represents the response to environmental conditions and can be used to reconstruct water mass properties. To infer both wind driven and thermohaline components of circulation in ancient oceans requires a model which relates circulation and water mass properties. With this motivation in mind we have formulated a model which satisfies the following criteria: (1) geostrophically balanced interior, (2) multiple sites for deep water production, (3) deep water production described by entraining plumes, (4) high vertical resolution in both velocity and property fields, (5) meridional varibility in wind stress and evaporation-precipitation rate, (6) applicable to basin scale where exchange with adjacent oceans described by flux conditions, and (7) the chemistry is coupled through the flux of particulate carbon sinking through the interior.

  16. Modeling mesoscale circulation of the Black Sea

    NASA Astrophysics Data System (ADS)

    Korotenko, K. A.

    2015-11-01

    An eddy-resolving (1/30)° version of the DieCAST low-dissipative model, adapted to the Black Sea circulation, is presented. Under mean climatological forcing, the model realistically reproduces major dominant large-scale and mesoscale structures of seasonal sea circulation, including the Rim Current, coastal anticyclonic eddies, mushroom currents, etc. Due to its extremely low dissipation and high resolution, the model makes it possible to trace the development of the baroclinic instability along the Turkish and Caucasian coasts, reproduce mesoscale structures generated by this mechanism, and assess the scales of these structures. The model also realistically reproduces short-term effects of bora winds on the evolution of subsurface layer structures.

  17. Circulating a Good Service Model at Its Core: Circulation!

    ERIC Educational Resources Information Center

    Hernandez, Edmee Sofia; Germain, Carol Anne, Ed.

    2009-01-01

    Circulation is the library's tireless foot soldier: it serves as the front gate to the library's services and resources. This service point is where most patrons enter and leave; and experience their first and last impressions--impressions that linger. In an age when academic libraries are facing meager budgets and declining usage statistics, this…

  18. 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

  19. Application of Improved Radiation Modeling to General Circulation Models

    SciTech Connect

    Michael J Iacono

    2011-04-07

    This research has accomplished its primary objectives of developing accurate and efficient radiation codes, validating them with measurements and higher resolution models, and providing these advancements to the global modeling community to enhance the treatment of cloud and radiative processes in weather and climate prediction models. A critical component of this research has been the development of the longwave and shortwave broadband radiative transfer code for general circulation model (GCM) applications, RRTMG, which is based on the single-column reference code, RRTM, also developed at AER. RRTMG is a rigorously tested radiation model that retains a considerable level of accuracy relative to higher resolution models and measurements despite the performance enhancements that have made it possible to apply this radiation code successfully to global dynamical models. This model includes the radiative effects of all significant atmospheric gases, and it treats the absorption and scattering from liquid and ice clouds and aerosols. RRTMG also includes a statistical technique for representing small-scale cloud variability, such as cloud fraction and the vertical overlap of clouds, which has been shown to improve cloud radiative forcing in global models. This development approach has provided a direct link from observations to the enhanced radiative transfer provided by RRTMG for application to GCMs. Recent comparison of existing climate model radiation codes with high resolution models has documented the improved radiative forcing capability provided by RRTMG, especially at the surface, relative to other GCM radiation models. Due to its high accuracy, its connection to observations, and its computational efficiency, RRTMG has been implemented operationally in many national and international dynamical models to provide validated radiative transfer for improving weather forecasts and enhancing the prediction of global climate change.

  20. Analysis of circulating tumor cells derived from advanced gastric cancer.

    PubMed

    Toyoshima, Kosei; Hayashi, Akira; Kashiwagi, Masahide; Hayashi, Naoko; Iwatsuki, Masaaki; Ishimoto, Takatsugu; Baba, Yoshifumi; Baba, Hideo; Ohta, Yoshikazu

    2015-08-15

    Studies in circulating tumor cells (CTCs) have proceeded to be accepted as prognostic markers in several types of cancers. But they are still limited because many are mainly from enumeration of CTCs. Here, we tried to evaluate the tumorigenicity of CTCs from advanced gastric cancer patients (n = 42). Peripheral blood mononuclear cells (PBMC) from the patients were separated into CD45 negative and positive fractions and both were subcutaneously injected into immunodeficient mice. Within 5 months nine tumor-like-structures from six patients but not from healthy volunteers were established. They were durable for passages and all had been confirmed human origin. Eight of the nine tumor-like-structures were from nonauthorized CTC containing cells expressing CD45 and B-cell markers. On the contrary, one of them was developed from CD45(-) PBMC fraction of a patient with bone marrow metastasis reflecting authorized CTCs. Histopathology showed common features with that of original gastric tumor. The cells isolated from the tumor-like-structure expressed EpCAM and CEA further supporting they were from the original tumor. Moreover the cells were CD44 positive to varying degree and a limiting dilution study showed that the CD44(+/high) fraction had tumorigenicity. The CD44 was dominantly in the form of CD44 variant 8-10. The CD44(+/high) cells had higher expression of the glutamate/cysteine transporter xCT compared with the CD44(-/low) cells. Our results showed the existence of tumor-initiating cells in blood of advanced gastric cancer patients and they could be a therapeutic target and prospective tool for further investigations.

  1. Circulation in the Gulf of Mexico: Observations and Models

    NASA Astrophysics Data System (ADS)

    Sturges, Wilton; Lugo-Fernandez, Alexis

    In this book, we describe our current state of knowledge on circulation in the Gulf of Mexico through 22 papers at the forefront of research. The view is selective rather than all-inclusive, with primary focus on circulation at the sea surface and at depth, including nearshore flow. In choosing topics, we have attempted to avoid the distinction between observations and models, as both are essential to advance our understanding of this exceptional body of water. We have also written for specialists and non-specialists alike in both science and industry: for those who work directly on the science associated with the Gulf, and for those whose work depends on the Gulf. And we refer here to physical oceanography, marine geology, sedimentology, coastal and estuarine science, as well as to the petrochemical and fishing industries.

  2. Modeling the Sun's Global Meridional Circulation

    NASA Astrophysics Data System (ADS)

    Dikpati, M.

    2013-12-01

    Meridional circulation is an important ingredient for solar dynamo models, and hence knowing its speed, its profile in latitude and depth and its time variation is crucial for understanding the dynamo. Observations provide us with knowledge about its speed and profile at the surface, more accurately at low to mid-latiudes. Consensus has not been reached regarding what is happening in polar regions and at greater depths. The theory of meridional circulation with latitude and depth can give us guidance as to what may be happening in these regions. A hierarchy of complexity of approaches to develop this theory is possible. We have built a global hydro-dynamical model of meridional circulation that includes Coriolis forces from differential rotation, turbulent Reynolds stresses, pressure forces, and provision for thermodynamics. By specifying differential rotations motivated by observations, we find that the steady-state solutions from this model include the following patterns: i) one long cell with poleward surface flow and an equatorward return flow at the base of the convection zone when there is no density increase with depth; ii) a primary flow-cell with poleward surface flow at low to mid-latitudes, together with a second, high latitude, reversed equatorward flow cell in the case of a solar-like density increase with depth and a solar-like differential rotation. However, for solar-like turbulent viscosity, the meridional flow speeds are much larger than observed, implying that an additional physical mechanism is needed that works against the meridional flow. The most likely candidate is a negative buoyancy force arising from small departures of the radial temperature gradient from the adiabatic gradient. There are several possible mechanisms for producing such an effect, but none can be defined well from available observations.

  3. Electrical Lumped Model Examination for Load Variation of Circulation System

    NASA Astrophysics Data System (ADS)

    Koya, Yoshiharu; Ito, Mitsuyo; Mizoshiri, Isao

    Modeling and analysis of the circulation system enables the characteristic decision of circulation system in the body to be made. So, many models of circulation system have been proposed. But, they are complicated because the models include a lot of elements. Therefore, we proposed a complete circulation model as a lumped electrical circuit, which is comparatively simple. In this paper, we examine the effectiveness of the complete circulation model as a lumped electrical circuit. We use normal, angina pectoris, dilated cardiomyopathy and myocardial infarction for evaluation of the ventricular contraction function.

  4. DETECTORS AND EXPERIMENTAL METHODS: Circulation model for water circulation and purification in a water Cerenkov detector

    NASA Astrophysics Data System (ADS)

    Lu, Hao-Qi; Yang, Chang-Gen; Wang, Ling-Yu; Xu, Ji-Lei; Wang, Rui-Guang; Wang, Zhi-Min; Wang, Yi-Fang

    2009-07-01

    Owing to its low cost and good transparency, highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work, a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system.

  5. Modeling biomass gasification in circulating fluidized beds

    NASA Astrophysics Data System (ADS)

    Miao, Qi

    In this thesis, the modeling of biomass gasification in circulating fluidized beds was studied. The hydrodynamics of a circulating fluidized bed operating on biomass particles were first investigated, both experimentally and numerically. Then a comprehensive mathematical model was presented to predict the overall performance of a 1.2 MWe biomass gasification and power generation plant. A sensitivity analysis was conducted to test its response to several gasifier operating conditions. The model was validated using the experimental results obtained from the plant and two other circulating fluidized bed biomass gasifiers (CFBBGs). Finally, an ASPEN PLUS simulation model of biomass gasification was presented based on minimization of the Gibbs free energy of the reaction system at chemical equilibrium. Hydrodynamics plays a crucial role in defining the performance of gas-solid circulating fluidized beds (CFBs). A 2-dimensional mathematical model was developed considering the hydrodynamic behavior of CFB gasifiers. In the modeling, the CFB riser was divided into two regions: a dense region at the bottom and a dilute region at the top of the riser. Kunii and Levenspiel (1991)'s model was adopted to express the vertical solids distribution with some other assumptions. Radial distributions of bed voidage were taken into account in the upper zone by using Zhang et al. (1991)'s correlation. For model validation purposes, a cold model CFB was employed, in which sawdust was transported with air as the fluidizing agent. A comprehensive mathematical model was developed to predict the overall performance of a 1.2 MWe biomass gasification and power generation demonstration plant in China. Hydrodynamics as well as chemical reaction kinetics were considered. The fluidized bed riser was divided into two distinct sections: (a) a dense region at the bottom of the bed where biomass undergoes mainly heterogeneous reactions and (b) a dilute region at the top where most of homogeneous

  6. Design of the UCLA general circulation model

    NASA Technical Reports Server (NTRS)

    Arakawa, A.

    1972-01-01

    An edited version is reported of notes distributed at the Summer Workshop on the UCLA General Circulation Model in June 1971. It presents the computational schemes of the UCLA model, along with the mathematical and physical principles on which these schemes are based. Included are the finite difference schemes for the governing fluid-dynamical equations, designed to maintain the important integral constraints and dispersion characteristics of the motion. Also given are the principles of parameterization of cumulus convection by an ensemble of identical clouds. A model of the ground hydrology, involving the liquid, ice and snow states of water, is included. A short summary is given of the scheme for computing solar and infrared radiation transfers through clear and cloudy air.

  7. Thermohaline circulation and its box models simulation

    NASA Astrophysics Data System (ADS)

    Bazyura, Kateryna; Polonsky, Alexander; Sannikov, Viktor

    2014-05-01

    Ocean Thermochaline circulation (THC) is the part of large-scale World Ocean circulation and one of the main climate system components. It is generated by global meridional density gradients, which are controlled by surface heat and freshwater fluxes. THC regulates climate variability on different timescales (from decades to thousands years) [Stocker (2000), Clark (2002)]. Study of paleoclimatic evidences of abrupt and dramatic changes in ocean-atmosphere system in the past (such as, Dansgaard-Oeschger and Heinrich events or Younger Dryas, see e.g., [Rahmstorf (2002), Alley & Clark(1999)]) shows that these events are connected with THC regimes. At different times during last 120,000 years, three THC modes have prevailed in the Atlantic. They can be labeled as stadial, interstadial and Heinrich modes or as cold, warm and off mode. THC collapse (or thermohaline catastrophe) can be one of the consequences of global warming (including modern anthropogenic climate changes occurring at the moment). The ideas underlying different box-model studies, possibility of thermochaline catastrophe in present and past are discussed in this presentation. Response of generalized four box model of North Atlantic thermohaline circulation [developing the model of Griffies & Tzippermann (1995)] on periodic, stochastic and linear forcing is studied in details. To estimate climatic parameters of the box model we used monthly salinity and temperature data of ECMWF operational Ocean Reanalysis System 3 (ORA-S3) and data from atmospheric NCEP/NCAR reanalysis on precipitation, and heat fluxes for 1959-2011. Mean values, amplitude of seasonal cycle, amplitudes and periods of typical interdecadal oscillations, white noise level, linear trend coefficients and their significance level were estimated for every hydrophysical parameter. In response to intense freshwater or heat forcing, THC regime can change resulting in thermohaline catastrophe. We analyze relevant thresholds of external forcing in

  8. Modeling the circulation of the Dead Sea

    NASA Astrophysics Data System (ADS)

    Brenner, Steve; Lensky, Nadav; Gertman, Isaac

    2015-04-01

    The Dead Sea is a hypersaline, terminal lake located at the lowest point on the land surface of the Earth. Its current level is more than 429 m below MSL, and due to a negative water balance (mainly anthropogenic), the lake level has been dropping at an average rate of more than 1 m/yr for more than 30 years. The mean salinity has also been steadily increasing and today is close to 280 psu. The region of the Dead Sea is a unique landscape that has important historical, cultural, and economic value and therefore such an extreme change of the lake has significant environmental and economic consequences. In recent years there has been a notable increase in observing and monitoring of the lake through continuous measurements from several fixed buoys as well as during quasi-regular cruises. In order to complement the measurements and improve our understanding of the dynamics of this unique lake a three dimensional circulation model is being developed. Previous modeling efforts were limited mainly to a one dimensional column model which was coupled to a comprehensive physio-chemical model and used for long term multi-decadal simulations. In this study the focus is on understanding the dynamical processes that control the lake-wide circulation on time scales ranging from days to seasons. The first step was to replace the equation of state with an equation appropriate for the hypersaline conditions, in addition to some minor tuning of the turbulence closure scheme. Results will be presented from preliminary simulations of the wind driven circulation in various seasons. A case study of a recent unusual winter flooding event, during which the lake level rose by more than 20 cm over a two month period, will also be presented. The model successfully simulated the observed transition from holomictic to meromictic conditions and epilimnion dilution during this event, as well as the restoration of holomictic conditions when the level started to drop again. The relationship

  9. Snow hydrology in a general circulation model

    NASA Technical Reports Server (NTRS)

    Marshall, Susan; Roads, John O.; Glatzmaier, Gary

    1994-01-01

    A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas. The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snowpack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter. Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.

  10. COMPUTATIONAL MODELING OF CIRCULATING FLUIDIZED BED REACTORS

    SciTech Connect

    Ibrahim, Essam A

    2013-01-09

    Details of numerical simulations of two-phase gas-solid turbulent flow in the riser section of Circulating Fluidized Bed Reactor (CFBR) using Computational Fluid Dynamics (CFD) technique are reported. Two CFBR riser configurations are considered and modeled. Each of these two riser models consist of inlet, exit, connecting elbows and a main pipe. Both riser configurations are cylindrical and have the same diameter but differ in their inlet lengths and main pipe height to enable investigation of riser geometrical scaling effects. In addition, two types of solid particles are exploited in the solid phase of the two-phase gas-solid riser flow simulations to study the influence of solid loading ratio on flow patterns. The gaseous phase in the two-phase flow is represented by standard atmospheric air. The CFD-based FLUENT software is employed to obtain steady state and transient solutions for flow modulations in the riser. The physical dimensions, types and numbers of computation meshes, and solution methodology utilized in the present work are stated. Flow parameters, such as static and dynamic pressure, species velocity, and volume fractions are monitored and analyzed. The differences in the computational results between the two models, under steady and transient conditions, are compared, contrasted, and discussed.

  11. GPU Developments for General Circulation Models

    NASA Astrophysics Data System (ADS)

    Appleyard, Jeremy; Posey, Stan; Ponder, Carl; Eaton, Joe

    2014-05-01

    Current trends in high performance computing (HPC) are moving towards the use of graphics processing units (GPUs) to achieve speedups through the extraction of fine-grain parallelism of application software. GPUs have been developed exclusively for computational tasks as massively-parallel co-processors to the CPU, and during 2013 an extensive set of new HPC architectural features were developed in a 4th generation of NVIDIA GPUs that provide further opportunities for GPU acceleration of general circulation models used in climate science and numerical weather prediction. Today computational efficiency and simulation turnaround time continue to be important factors behind scientific decisions to develop models at higher resolutions and deploy increased use of ensembles. This presentation will examine the current state of GPU parallel developments for stencil based numerical operations typical of dynamical cores, and introduce new GPU-based implicit iterative schemes with GPU parallel preconditioning and linear solvers based on ILU, Krylov methods, and multigrid. Several GCMs show substantial gain in parallel efficiency from second-level fine-grain parallelism under first-level distributed memory parallel through a hybrid parallel implementation. Examples are provided relevant to science-scale HPC practice of CPU-GPU system configurations based on model resolution requirements of a particular simulation. Performance results compare use of the latest conventional CPUs with and without GPU acceleration. Finally a forward looking discussion is provided on the roadmap of GPU hardware, software, tools, and programmability for GCM development.

  12. Regional climates in the GISS global circulation model - Synoptic-scale circulation

    NASA Technical Reports Server (NTRS)

    Hewitson, B.; Crane, R. G.

    1992-01-01

    A major weakness of current general circulation models (GCMs) is their perceived inability to predict reliably the regional consequences of a global-scale change, and it is these regional-scale predictions that are necessary for studies of human-environmental response. For large areas of the extratropics, the local climate is controlled by the synoptic-scale atmospheric circulation, and it is the purpose of this paper to evaluate the synoptic-scale circulation of the Goddard Institute for Space Studies (GISS) GCM. A methodology for validating the daily synoptic circulation using Principal Component Analysis is described, and the methodology is then applied to the GCM simulation of sea level pressure over the continental United States (excluding Alaska). The analysis demonstrates that the GISS 4 x 5 deg GCM Model II effectively simulates the synoptic-scale atmospheric circulation over the United States. The modes of variance describing the atmospheric circulation of the model are comparable to those found in the observed data, and these modes explain similar amounts of variance in their respective datasets. The temporal behavior of these circulation modes in the synoptic time frame are also comparable.

  13. Enceladus' Interior: A Liquid Circulation Model

    NASA Astrophysics Data System (ADS)

    Matson, Dennis L.; Johnson, Torrence; Lunine, Jonathan; Castillo-Rogez, Julie

    We are studying a model for Enceladus' interior in which the water, gas, dust and heat are supplied to the plumes by a relatively deeply circulating brine solution. Data indicates such a source for the erupting material. On the basis of ammonia in the plume gas Waite et al. [1] suggested that the jets might originate from a liquid water region under Enceladus' icy surface. Postberg et al. [2] noted that the presence of ". . . grains that are rich in sodium salts (0.5-2 percent by mass). . . can arise only if the plumes originate from liquid water." Waite et al. [1] also regard the some of the plume chemicals as evidence for interactions with an ice layer presumably overlying the liquid water reservoir. They suggest that this could be in the form of dissociation of clathrate hydrates [3]. Additionally, there is a large heat flow of more than 15 GW [4, 5] coming out of Enceladus' south polar region. We consider a model that brings heat and chemical species up to the surface from a reservoir or "ocean" located below the ice crust that may be many tens of kilometers thick. Water transits to the surface via vertical conduits. The Cassini INMS data suggest that the water has a relatively large gas content of order a few percent. As the water travels upward and the pressure is released, exolving gases form bubbles. Since the bubbly liquid is less dense than the ice, it moves upward. (This part of the model is a variant of the "Perrier Ocean" Europa model of Crawford and Stevenson [6]. A similar model was studied for Ganymede by Murchie and Head [7].) Postberg et al. [2] model the plume eruptions that result from the water, gases, salts, and other chemicals that our circulation model provides. In the near-surface reservoir feeding the plumes, bubbles reaching the surface of the water pop and throw a very fine spray. Some of these very small droplets of brine exit with the plume gas and provide the observed salt-rich dust particles [2]. Much of the water-borne heat is

  14. Advanced Concept Modeling

    NASA Technical Reports Server (NTRS)

    Chaput, Armand; Johns, Zachary; Hodges, Todd; Selfridge, Justin; Bevirt, Joeben; Ahuja, Vivek

    2015-01-01

    Advanced Concepts Modeling software validation, analysis, and design. This was a National Institute of Aerospace contract with a lot of pieces. Efforts ranged from software development and validation for structures and aerodynamics, through flight control development, and aeropropulsive analysis, to UAV piloting services.

  15. A Model for Library Book Circulations Incorporating Loan Periods.

    ERIC Educational Resources Information Center

    Burrell, Quentin L.; Fenton, Michael R.

    1994-01-01

    Proposes and explains a modification of the mixed Poisson model for library circulations which takes into account the periods when a book is out on loan and therefore unavailable for borrowing. Highlights include frequency of circulation distributions; negative binomial distribution; and examples of the model at two universities. (Contains 34…

  16. Diversity of Planetary Atmospheric Circulations and Climates in a Simplified General Circulation Model

    NASA Astrophysics Data System (ADS)

    Wang, Yixiong; Read, Peter

    2014-04-01

    The parametric dependence of terrestrial planetary atmospheric circulations and climates on characteristic parameters is studied. A simplified general circulation model-PUMA is employed to investigate the dynamic effects of planetary rotation rate and equator-to-pole temperature difference on the circulation and climate of terrestrial planetary atmospheres. Five different types of circulation regime are identified by mapping the experimental results in a 2-D parameter space defined by thermal Rossby number and frictional Taylor number. The effect of the transfer and redistribution of radiative energy is studied by building up a new two-band semi-gray radiative-convective scheme, which is capable of modelling greenhouse and anti-greenhouse effects while keeping the tunable parameters as few as possible. The results will provide insights into predicting the habitability of terrestrial exoplanets.

  17. Modeling the impact of bay breeze circulations on nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Loughner, C. P.; Tzortziou, M.; Pickering, K. E.; Duffy, M.; Satam, C.

    2012-12-01

    Atmospheric gases and aerosols are deposited into watersheds and estuarine waters contributing to water quality degradation and affecting estuarine and coastal biogeochemical processes. Pollution that is deposited onto land can be transported into storm drains, groundwater, streams, and rivers where it is eventually transported into near-shore waters. Air quality models, which simulate the chemical transformation, atmospheric transport, and deposition of pollutants onto land and surface waters, can play an integral role in forecasting water quality, preparing water quality regulations and providing information on the sources of nutrients and pollutants for advanced estuarine biogeochemical models. Previous studies have found that Chesapeake Bay breezes cause localized areas of high air pollution concentrations and that model simulations with horizontal resolutions coarser than about 5 km are not able to capture bay breeze circulations. Here, we investigate the importance of capturing bay breeze circulations with high resolution model simulations (horizontal resolution of 1.33 km) to accurately simulate the spatial and temporal variability of nitrogen deposition into the Chesapeake Bay watershed. Nitrogen deposition into the watershed from air quality model simulations are compared with observed wet deposition and estimated dry deposition rates from the National Acid Deposition Program (NADP) and the Clean Air Status and Trends Network (CASTNET), respectively. The model simulation is conducted for the months of June and July 2011. Two concurrent air and water quality field campaigns, DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) and GeoCAPE-CBODAQ (Geostationary Coastal and Air Pollution Events-Chesapeake Bay Oceanographic Campaign with DISCOVER-AQ), were conducted in July 2011, and data obtained from these field experiments are used to evaluate the model simulations.

  18. ADCIRC: An advanced three-dimensional circulation model for shelves, coasts, and estuaries. Report 3. Development of a tidal constituent database for the western north Atlantic and Gulf of Mexico. Technical report

    SciTech Connect

    Westerink, J.J.; Luettich, R.A.; Scheffner, N.

    1993-06-01

    This report describes the application of model ADCIRC-2DDI, a two-dimensional, depth-integrated, finite-element-based hydrodynamic circulation code, to the western North Atlantic, Gulf of Mexico and Caribbean Sea in order to develop a tidal constituent database. Issues that are emphasized in the development of the Western North Atlantic Tidal (WNAT) model include the definition of hydrodynamically simple open ocean boundaries; the use of large domains; the importance of a high degree of grid resolution in coastal regions; and the use of finite element meshes with highly varying nodal densities in order to minimize the size of the discrete problem. The development of an optimal graded finite element mesh is based on regular and graded grid convergence studies using an M2 tidal forcing function on the boundary and within the domain. The optimal graded mesh is then forced for eight diurnal and semidiurnal astronomical tidal constituents (K1, O1, PI, Ql, M2, S2, N2, and K2) on the open ocean boundary by coupling to Schwiderski's (1979; 1981 a-g) global model results as well as within the interior domain using a tidal potential forcing function. The structure of the various tides is examined and results are compared to field data at 77 stations.... Bottom stress, Finite element method, Three-dimensional model, Circulation model, Hydrodynamic model, Two-dimensional model, Direct stress solution, Numerical model.

  19. Model-free adaptive control of supercritical circulating fluidized-bed boilers

    DOEpatents

    Cheng, George Shu-Xing; Mulkey, Steven L

    2014-12-16

    A novel 3-Input-3-Output (3.times.3) Fuel-Air Ratio Model-Free Adaptive (MFA) controller is introduced, which can effectively control key process variables including Bed Temperature, Excess O2, and Furnace Negative Pressure of combustion processes of advanced boilers. A novel 7-input-7-output (7.times.7) MFA control system is also described for controlling a combined 3-Input-3-Output (3.times.3) process of Boiler-Turbine-Generator (BTG) units and a 5.times.5 CFB combustion process of advanced boilers. Those boilers include Circulating Fluidized-Bed (CFB) Boilers and Once-Through Supercritical Circulating Fluidized-Bed (OTSC CFB) Boilers.

  20. CXCL10 Is a Circulating Inflammatory Marker in Patients with Advanced Heart Failure: a Pilot Study.

    PubMed

    Altara, Raffaele; Manca, Marco; Hessel, Marleen H; Gu, Yumei; van Vark, Laura C; Akkerhuis, K Martijn; Staessen, Jan A; Struijker-Boudier, Harry A J; Booz, George W; Blankesteijn, W Matthijs

    2016-08-01

    Chemokines are involved in the remodeling of the heart; however, their significance as biomarkers in heart failure is unknown. We observed that circulating CXCR3 receptor chemokines CXCL9 and CXCL10 in a rat model of heart failure were increased 1 week after myocardial infarction. CXCL10 was also increased in both remote and infarcted regions of the heart and remained elevated at 16 weeks; CXCL9 was elevated in the remote area at 1 week. In humans, hierarchical clustering and principal component analysis revealed that circulating CXCL10, MIP-1α, and CD40 ligand were the best indicators for differentiating healthy and heart failure subjects. Serum CXCL10 levels were increased in patients with symptomatic heart failure as indexed by NYHA classification II through IV. The presence of CXCL10, MIP-1α, and CD40 ligand appears to be dominant in patients with advanced heart failure. These findings identify a distinct profile of inflammatory mediators in heart failure patients. PMID:27271043

  1. CXCL10 Is a Circulating Inflammatory Marker in Patients with Advanced Heart Failure: a Pilot Study.

    PubMed

    Altara, Raffaele; Manca, Marco; Hessel, Marleen H; Gu, Yumei; van Vark, Laura C; Akkerhuis, K Martijn; Staessen, Jan A; Struijker-Boudier, Harry A J; Booz, George W; Blankesteijn, W Matthijs

    2016-08-01

    Chemokines are involved in the remodeling of the heart; however, their significance as biomarkers in heart failure is unknown. We observed that circulating CXCR3 receptor chemokines CXCL9 and CXCL10 in a rat model of heart failure were increased 1 week after myocardial infarction. CXCL10 was also increased in both remote and infarcted regions of the heart and remained elevated at 16 weeks; CXCL9 was elevated in the remote area at 1 week. In humans, hierarchical clustering and principal component analysis revealed that circulating CXCL10, MIP-1α, and CD40 ligand were the best indicators for differentiating healthy and heart failure subjects. Serum CXCL10 levels were increased in patients with symptomatic heart failure as indexed by NYHA classification II through IV. The presence of CXCL10, MIP-1α, and CD40 ligand appears to be dominant in patients with advanced heart failure. These findings identify a distinct profile of inflammatory mediators in heart failure patients.

  2. Seasonal overturning circulation in the Red Sea: 1. Model validation and summer circulation

    NASA Astrophysics Data System (ADS)

    Yao, Fengchao; Hoteit, Ibrahim; Pratt, Larry J.; Bower, Amy S.; Zhai, Ping; Köhl, Armin; Gopalakrishnan, Ganesh

    2014-04-01

    The overturning circulation in the Red Sea exhibits a distinct seasonally reversing pattern and is studied using high-resolution MIT general circulation model simulations. In the first part of this study, the vertical and horizontal structure of the summer overturning circulation and its dynamical mechanisms are presented from the model results. The seasonal water exchange in the Strait of Bab el Mandeb is successfully simulated, and the structures of the intruding subsurface Gulf of Aden intermediate water are in good agreement with summer observations in 2011. The model results suggest that the summer overturning circulation is driven by the combined effect of the shoaling of the thermocline in the Gulf of Aden resulting from remote winds in the Arabian Sea and an upward surface slope from the Red Sea to the Gulf of Aden set up by local surface winds in the Red Sea. In addition, during late summer two processes associated, respectively, with latitudinally differential heating and increased salinity in the southern Red Sea act together to cause the reversal of the contrast of the vertical density structure and the cessation of the summer overturning circulation. Dynamically, the subsurface northward pressure gradient force is mainly balanced by vertical viscosity resulting from the vertical shear and boundary friction in the Strait of Bab el Mandeb. Unlike some previous studies, the three-layer summer exchange flows in the Strait of Bab el Mandeb do not appear to be hydraulically controlled.

  3. Systemic modelling of human bioenergetics and blood circulation.

    PubMed

    Lim, K M; Yang, S-H; Shim, E B

    2012-10-01

    This work reviews the main aspects of human bioenergetics and the dynamics of the cardiovascular system, with emphasis on modelling their physiological characteristics. The methods used to study human bioenergetics and circulation dynamics, including the use of mathematical models, are summarised. The main characteristics of human bioenergetics, including mitochondrial metabolism and global energy balance, are first described, and the systemic aspects of blood circulation and related physiological issues are introduced. The authors also discuss the present status of studies of human bioenergetics and blood circulation. Then, the limitations of the existing studies are described in an effort to identify directions for future research towards integrated and comprehensive modelling. This review emphasises that a multi-scale and multi-physical approach to bioenergetics and blood circulation that considers multiple scales and physiological factors are necessary for the appropriate clinical application of computational models.

  4. Advances in circulating tumor cells (ACTC): from basic research to clinical practice

    PubMed Central

    2013-01-01

    The first 'Advances in Circulating Tumor Cells (ACTC): from Basic Research to Clinical Practice' meeting was held in Athens, Greece, September 26–29, 2012 (abstracts, presentations and a more detailed meeting report are freely available online: http://www.actc2012.org). We summarize in this report most major findings presented and the main conclusions derived during the expert panel sessions. PMID:24314311

  5. Modeling the Martian climate with a new general circulation model

    NASA Astrophysics Data System (ADS)

    Urata, R.; Toon, O. B.

    2009-12-01

    We have adapted the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM3.0) to Martian conditions. Several modifications to the original model have been made. These include adjusting the physical parameters to Mars-like values, changing atmospheric composition, changing the calendar to cover a Martian year, and the addition of a carbon dioxide condensation scheme. The Martian atmosphere is composed of 95% carbon dioxide, and as much as 25% of the atmosphere can condense out at the winter pole so it is important to include the carbon dioxide condensation in the model. We plan to use the model to simulate impacts on Mars during the late Noachian. As a reference point we have performed some climate simulations with a 500 mbar carbon dioxide atmosphere. The results will be presented at the meeting. Currently a few general circulation models are available for Mars. However instead of using one of these previously developed models, we have chosen to develop our own based off of CAM3 for a number of reasons. These include the model’s support for multi-processor runs, the model’s compatibility with other models including land, aerosol, and chemistry, and the fact many in our group already use the Earth version of this model, so we are familiar with it. During the development of our model, we have been in contact with NCAR, and have plans to make the model readily available to the public through NCAR.

  6. Modelling the Seasonal Overturning Circulation in the Red Sea

    NASA Astrophysics Data System (ADS)

    Yao, Fengchao; Hoteit, Ibrahim; Pratt, Larry; Bower, Amy; Koehl, Armin; Gopalakrishnan, Ganesh

    2015-04-01

    The overturning circulation in the Red Sea exhibits a distinct seasonally reversing pattern and is studied using 50-year, high-resolution MIT general circulation model simulations. The seasonal water exchange in the Strait of Bab el Mandeb is successfully simulated, and the structures of the intruding subsurface Gulf of Aden intermediate water are in good agreement with summer observations in 2011. The model results suggest that the summer overturning circulation is driven by the combined effect of the shoaling of the thermocline in the Gulf of Aden resulting from remote winds in the Arabian Sea and an upward surface slope from the Red Sea to the Gulf of Aden set up by local surface winds in the Red Sea. For the winter overturning circulation, the climatological model mean results suggest that the surface inflow intensifies in a western boundary current in the southern Red Sea that switches to an eastern boundary current north of 24°N. The overturning is accomplished through a cyclonic recirculation and a cross-basin overturning circulation in the northern Red Sea, with major sinking occurring along a narrow band of width about 20 km along the eastern boundary and weaker upwelling along the western boundary. The northward pressure gradient force, strong vertical mixing, and horizontal mixing near the boundary are the essential dynamical components in the model's winter overturning circulation.

  7. System model of a natural circulation integral test facility

    NASA Astrophysics Data System (ADS)

    Galvin, Mark R.

    The Department of Nuclear Engineering and Radiation Health Physics (NE/RHP) at Oregon State University (OSU) has been developing an innovative modular reactor plant concept since being initiated with a Department of Energy (DoE) grant in 1999. This concept, the Multi-Application Small Light Water Reactor (MASLWR), is an integral pressurized water reactor (PWR) plant that utilizes natural circulation flow in the primary and employs advanced passive safety features. The OSU MASLWR test facility is an electrically heated integral effects facility, scaled from the MASLWR concept design, that has been previously used to assess the feasibility of the concept design safety approach. To assist in evaluating operational scenarios, a simulation tool that models the test facility and is based on both test facility experimental data and analytical methods has been developed. The tool models both the test facility electric core and a simulated nuclear core, allowing evaluation of a broad spectrum of operational scenarios to identify those scenarios that should be explored experimentally using the test facility or design-quality multi-physics tools. Using the simulation tool, the total cost of experimentation and analysis can be reduced by directing time and resources towards the operational scenarios of interest.

  8. High pressure experiments with a Mars general circulation model

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Pollack, J. B.; Murphy, J. R.; Schaeffer, J.; Lee, H.

    1992-01-01

    The interaction of three physical processes will determine the stability of the Martian polar caps as the surface pressure increases: the greenhouse effect, atmospheric heat transport, and the change in the CO2 frost point temperature. The contribution of each is readily determined in the Mars general circulation model (GCM). Therefore, we have initiated experiments with the GCM to determine how these processes interact, and how the atmosphere-polar cap system responds to increasing surface pressure. The experiments are carried out for northern winter solstice and generally assume the atmosphere to be free of dust. Each experiment starts from resting isothermal conditions and runs for 50 Mars days. Mars' current orbital parameters are used. The experiments are for surface pressures of 120, 480, and 960 mb, which represent 16, 64, and 128 times the current value. To date we have analyzed the 120 mb experiment and the results indicate the contrary to the simpler models, the polar caps actually advance instead of retreat. Other aspects of this investigation are presented.

  9. A Cost Effectiveness Model for Comparing Various Circulation Systems

    ERIC Educational Resources Information Center

    Burgess, Thomas K.

    1973-01-01

    Two models for circulation systems (manual and automated) costing are presented. Validation tests for the model assumptions are devised and explained. Use of the models for cost effectiveness comparison and for cost prediction are discussed and examples are given showing their application. (10 references) (Author/SJ)

  10. Advanced Chemistry Basins Model

    SciTech Connect

    William Goddard; Mario Blanco; Lawrence Cathles; Paul Manhardt; Peter Meulbroek; Yongchun Tang

    2002-11-10

    The DOE-funded Advanced Chemistry Basin model project is intended to develop a public domain, user-friendly basin modeling software under PC or low end workstation environment that predicts hydrocarbon generation, expulsion, migration and chemistry. The main features of the software are that it will: (1) afford users the most flexible way to choose or enter kinetic parameters for different maturity indicators; (2) afford users the most flexible way to choose or enter compositional kinetic parameters to predict hydrocarbon composition (e.g., gas/oil ratio (GOR), wax content, API gravity, etc.) at different kerogen maturities; (3) calculate the chemistry, fluxes and physical properties of all hydrocarbon phases (gas, liquid and solid) along the primary and secondary migration pathways of the basin and predict the location and intensity of phase fractionation, mixing, gas washing, etc.; and (4) predict the location and intensity of de-asphaltene processes. The project has be operative for 36 months, and is on schedule for a successful completion at the end of FY 2003.

  11. Advanced geothermal hydraulics model -- Phase 1 final report, Part 2

    SciTech Connect

    W. Zheng; J. Fu; W. C. Maurer

    1999-07-01

    An advanced geothermal well hydraulics model (GEODRIL) is being developed to accurately calculate bottom-hole conditions in these hot wells. In Phase 1, real-time monitoring and other improvements were added to GEODRIL. In Phase 2, GEODRIL will be integrated into Marconi's Intelligent Drilling Monitor (IDM) that will use artificial intelligence to detect lost circulation, fluid influxes and other circulation problems in geothermal wells. This software platform has potential for significantly reducing geothermal drilling costs.

  12. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Richard Dimenna, R; David Tamburello, D

    2008-11-13

    (50,000 to 300,000) with a relative standard deviation of {+-} 11.83%. An improved correlation including the effect of circulation time was proposed by Grenville and Tilton [11] via a better fit of mixing time data for turbulent jet mixing under a wider range of jet Reynolds numbers (50,000 to 300,000). The circulation time was defined as the liquid volume divided by the entrained flow rate. They assumed that the mixing rate at the end of the jet length controls the mixing time for the entire tank by estimating the kinetic energy dissipation rate as discussed earlier. They predicted that for a given volume, an optimum geometry exists for a mixing vessel, allowing a desired mixing time to be achieved for a minimum power input. The current work will compare their correlation of the jet mixing time with CFD modeling results for their experimental tanks in an attempt to achieve a fundamental understanding of the turbulent jet mixing and to establish mixing indicators.

  13. Cloud Feedback in Atmospheric General Circulation Models: An Update

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M. H.; Ingram, W. J.; Potter, G. L.; Alekseev, V.; Barker, H. W.; Cohen-Solal, E.; Colman, R. A.; Dazlich, D. A.; DelGenio, A. D.; Dix, M. R.; Dymnikov, V.; Esch, M.; Fowler, L. D.; Fraser, J. R.; Galin, V.; Gates, W. L.; Hack, J. J.; Kiehl, J. T.; LeTreut, H.

    1996-01-01

    Six years ago, we compared the climate sensitivity of 19 atmospheric general circulation models and found a roughly threefold variation among the models; most of this variation was attributed to differences in the models' depictions of cloud feedback. In an update of this comparison, current models showed considerably smaller differences in net cloud feedback, with most producing modest values. There are, however, substantial differences in the feedback components, indicating that the models still have physical disagreements.

  14. Data Collection and Cost Modeling for Library Circulation Systems.

    ERIC Educational Resources Information Center

    Bourne, Charles P.

    The objectives of the study leading to this report were to review, analyze and summarize published library cost data; and to develop a cost model and a methodology for reporting data in a more consistent and useful way. The cost model and reporting procedure were developed and tested on the circulation system of three libraries: a large university…

  15. Optimal control of CPR procedure using hemodynamic circulation model

    DOEpatents

    Lenhart, Suzanne M.; Protopopescu, Vladimir A.; Jung, Eunok

    2007-12-25

    A method for determining a chest pressure profile for cardiopulmonary resuscitation (CPR) includes the steps of representing a hemodynamic circulation model based on a plurality of difference equations for a patient, applying an optimal control (OC) algorithm to the circulation model, and determining a chest pressure profile. The chest pressure profile defines a timing pattern of externally applied pressure to a chest of the patient to maximize blood flow through the patient. A CPR device includes a chest compressor, a controller communicably connected to the chest compressor, and a computer communicably connected to the controller. The computer determines the chest pressure profile by applying an OC algorithm to a hemodynamic circulation model based on the plurality of difference equations.

  16. Thermospheric tides simulated by the national center for atmospheric research thermosphere-ionosphere general circulation model at equinox

    SciTech Connect

    Fesen, C.G. ); Roble, R.G.; Ridley, E.C. )

    1993-05-01

    The authors use the National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM) to model tides and dynamics in the thermosphere. This model incorporates the latest advances in the thermosphere general circulation model. Model results emphasized the 70[degree] W longitude region to overlap a series of incoherent radar scatter installations. Data and the model are available on data bases. The results of this theoretical modeling are compared with available data, and with prediction of more empirical models. In general there is broad agreement within the comparisons.

  17. Stratospheric General Circulation with Chemistry Model (SGCCM)

    NASA Technical Reports Server (NTRS)

    Rood, Richard B.; Douglass, Anne R.; Geller, Marvin A.; Kaye, Jack A.; Nielsen, J. Eric; Rosenfield, Joan E.; Stolarski, Richard S.

    1990-01-01

    In the past two years constituent transport and chemistry experiments have been performed using both simple single constituent models and more complex reservoir species models. Winds for these experiments have been taken from the data assimilation effort, Stratospheric Data Analysis System (STRATAN).

  18. The Martian Atmosphere, Climate, and General Circulation Models

    NASA Astrophysics Data System (ADS)

    Richardson, M. I.

    2004-05-01

    Our understanding of the Martian atmosphere, and the embodiment of this understanding in GCM models, sits part way between that of the Earth's atmosphere and that of the other planets in the solar system. Compared to the Earth, it is incomplete even as it applies to certain basic, elementary components and it is studied by a very limited community. Compared to the other planets in the solar system, most elements of the circulation are understood in outline, the data sets are vast and rich, and a number of well-staffed, competing modeling groups exist. Given this ``middle sibling'' status of Martian atmospheric science, an obvious issue arises as to whom it should be compared: Is the paucity of our understanding compared to the Earth motivation for redoubled efforts, or advanced state of knowledge cause to refocus on other planetary bodies? In this presentation, I will review the components of the Martian circulation and the progress that has been made in their understanding through the synthesis of data with GCMs. I will also review the aspects of Martian climate that uniquely influence the atmosphere. These include the lofting of dust by large-scale winds and thermal convection, resulting in a permanent (if varying) dust haze that significantly increases atmospheric temperatures, and occasionally leading to the generation of global dust storms. The spontaneous generation of such storms in a GCM has only very recently been accomplished. The condensation of the major atmospheric constituent (CO2) onto the surface to form massive seasonal ice caps in the frigid polar winter also generates a significant climate signal and a pole-to-pole condensation flow. Finally, Mars possesses an active water cycle with the development of clouds, formation of seasonal water ice deposits, and storage of water in the near-sub surface as adsorbate. The water cycle is fundamentally driven by exchange with a residual water ice cap at the northern (and not the southern) pole. Such

  19. Modeling of Antarctic sea ice in a general circulation model

    SciTech Connect

    Wu, Xingren; Budd, W.F.; Simmonds, I.

    1997-04-01

    A dynamic-thermodynamic sea ice model is developed and coupled with the Melbourne University general circulation model to simulate the seasonal cycle of the Antarctic sea ice distributions The model is efficient, rapid to compute, and useful for a range of climate studies. The thermodynamic part of the sea ice model is similar to that developed by Parkinson and Washington, the dynamics contain a simplified ice rheology that resists compression. The thermodynamics is based on energy conservation at the top surface of the ice/snow, the ice/water interface, and the open water area to determine the ice formation, accretion, and ablation. A lead parameterization is introduced with an effective partitioning scheme for freezing between and under the ice floes. The dynamic calculation determines the motion of ice, which is forced with the atmospheric wind, taking account of ice resistance and rafting. The simulated sea ice distribution compares reasonably well with observations. The seasonal cycle of ice extent is well simulated in phase as well as in magnitude. Simulated sea ice thickness and concentration are also in good agreement with observations over most regions and serve to indicate the importance of advection and ocean drift in the determination of the sea ice distribution. 64 refs., 15 figs., 2 tabs.

  20. 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.

  1. Hemodynamic changes in the hepatic circulation after the modulation of the splenic circulation in an in vivo human experimental model.

    PubMed

    Akamatsu, Nobuhisa; Sugawara, Yasuhiko; Satou, Shouichi; Mitsui, Tetsuya; Ninomiya, Riki; Komagome, Masahiko; Ozawa, Fumiaki; Beck, Yoshifumi

    2014-01-01

    Recent advances in liver surgery have highlighted the effects of the splenic circulation on the hepatic circulation with respect to the hepatic arterial buffer response (HABR). The aim of the present study was to investigate the actual hemodynamic effects of splenic artery embolization/ligation and splenectomy on the hepatic circulation in patients who underwent pancreaticoduodenectomy through in vivo experimental models. In vivo models of splenic artery embolization/ligation (only splenic artery clamping) and splenectomy (simultaneous clamping of both the splenic artery and the splenic vein) were created in 40 patients who underwent pancreaticoduodenectomy for various reasons. The portal venous flow velocity, the portal venous flow volume, the hepatic arterial flow velocity, and the hepatic arterial resistance index were measured with color Doppler ultrasonography. Clamping of the splenic artery induced an immediate and significant increase (16%) in the hepatic artery velocity (P < 0.001), and the portal venous flow also decreased significantly (10%, P = 0.03). Fifteen minutes after the clamping of the splenic artery, the hepatic artery velocity remained significantly increased at the level of the initial clamping, and the portal venous flow significantly decreased (16%, P < 0.001). Clamping of the splenic vein, which was performed after the clamping of the splenic artery, resulted in an immediate and significant decrease (30%) in the portal venous flow (P < 0.001), but the hepatic arterial flow was not affected. Fifteen minutes after the clamping of the splenic vein, there was no change in the portal flow, which remained significantly lower (28%) than the flow in controls, whereas the hepatic arterial flow further significantly increased (31%, P < 0.001). In conclusion, our findings indicate that both splenic artery embolization/ligation and splenectomy are effective for increasing hepatic arterial flow and decreasing portal flow, with splenectomy providing a

  2. 14C-age tracers in global ocean circulation models

    NASA Astrophysics Data System (ADS)

    Koeve, W.; Wagner, H.; Kähler, P.; Oschlies, A.

    2014-10-01

    The natural abundance of 14C in total CO2 dissolved in seawater is a property applied to evaluate the water age structure and circulation in the ocean and in ocean models. In this study we use three different representations of the global ocean circulation augmented with a suite of idealised tracers to study the potential and limitations of using natural 14C to determine water age, the time elapsed since a body of water had contact with the atmosphere. We find that, globally, bulk 14C-age is dominated by two equally important components, one associated with aging, i.e. the time component of circulation and one associated with a "preformed 14C-age". This latter quantity exists because of the slow and incomplete atmosphere/ocean equilibration of 14C in particular in high latitudes where many water masses form. The relative contribution of the preformed component to bulk 14C-age varies regionally within a given model, but also between models. Regional variability, e.g. in the Atlantic Ocean is associated with the mixing of waters with very different end members of preformed 14C-age. In the Atlantic, variations in the preformed component over space and time mask the circulation component to an extent that its patterns are not detectable from bulk 14C-age alone. Between models the variability of age can also be considerable (factor of 2), related to the combinations of physical model parameters, which influence circulation dynamics, and gas exchange in the models. The preformed component was found to be very sensitive to gas exchange and moderately sensitive to ice cover. In our model evaluation exercise, the choice of the gas exchange constant from within the current range of uncertainty had such a strong influence on preformed and bulk 14C-age that if model evaluation would be based on bulk 14C-age it could easily impair the evaluation and tuning of a models circulation on global and regional scales. Based on the results of this study, we propose that considering

  3. Interactions Between the Thermohaline Circulation and Tropical Atlantic SST in a Coupled General Circulation Model

    NASA Technical Reports Server (NTRS)

    Miller, Ron; Jiang, Xing-Jian; Travis, Larry (Technical Monitor)

    2001-01-01

    Tropical Atlantic SST shows a (statistically well-defined) decadal time scale in a 104-year simulation of unforced variability by a coupled general circulation model (CGCM). The SST anomalies superficially resemble observed Tropical Atlantic variability (TAV), and are associated with changes in the atmospheric circulation. Brazilian rainfall is modulated with a decadal time scale, along with the strength of the Atlantic trade winds, which are associated with variations in evaporation and the net surface heat flux. However, in contrast to observed tropical Atlantic variability, the trade winds damp the associated anomalies in ocean temperature, indicating a negative feedback. Tropical SST anomalies in the CGCM, though opposed by the surface heat flux, are advected in from the Southern Hemisphere mid-latitudes. These variations modulate the strength of the thermohaline circulation (THC): warm, salty anomalies at the equator sink drawing cold, fresh mid-latitude water. Upon reaching the equator, the latter inhibit vertical overturning and advection from higher latitudes, which allows warm, salty anomalies to reform, returning the cycle to its original state. Thus, the cycle results from advection of density anomalies and the effect of these anomalies upon the rate of vertical overturning and surface advection. This decadal modulation of Tropical Atlantic SST and the thermohaline circulation is correlated with ocean heat transport to the Northern Hemisphere high latitudes and Norwegian Sea SST. Because of the central role of equatorial convection, we question whether this mechanism is present in the current climate, although we speculate that it may have operated in palaeo times, depending upon the stability of the tropical water column.

  4. 14C-age tracers in global ocean circulation models

    NASA Astrophysics Data System (ADS)

    Koeve, W.; Wagner, H.; Kähler, P.; Oschlies, A.

    2015-07-01

    The natural abundance of 14C in total CO2 dissolved in seawater (DIC) is a property applied to evaluate the water age structure and circulation in the ocean and in ocean models. In this study we use three different representations of the global ocean circulation augmented with a suite of idealised tracers to study the potential and limitations of using natural 14C to determine water age, which is the time elapsed since a body of water has been in contact with the atmosphere. We find that, globally, bulk 14C-age is dominated by two equally important components, one associated with ageing, i.e. the time component of circulation, and one associated with a "preformed 14C-age". The latter quantity exists because of the slow and incomplete atmosphere-ocean equilibration of 14C particularly in high latitudes where many water masses form. In the ocean's interior, preformed 14C-age behaves like a passive tracer. The relative contribution of the preformed component to bulk 14C-age varies regionally within a given model, but also between models. Regional variability in the Atlantic Ocean is associated with the mixing of waters with very different end members of preformed 14C-age. Here, variations in the preformed component over space and time mask the circulation component to an extent that its patterns are not detectable from bulk 14C-age. Between models, the variability of preformed 14C-age can also be considerable (factor of 2), related to the combination of physical model parameters, which influence circulation dynamics or gas exchange. The preformed component was found to be very sensitive to gas exchange and moderately sensitive to ice cover. In our model evaluation, the choice of the gas-exchange constant from within the currently accepted range of uncertainty had such a strong influence on preformed and bulk 14C-age that if model evaluation would be based on bulk 14C-age, it could easily impair the evaluation and tuning of a model's circulation on global and regional

  5. General circulation model sensitivity experiments with pole-centered supercontinents

    SciTech Connect

    Crowley, T.J.; Baum, S.K.; Kim, Kwang-Yul )

    1993-05-20

    The authors present model studies related to the general question of whether there could have been nearly ice-free climates in the past history of the Earth. Energy balance models and general circulation model calculations have addressed this question. In general this appears impossible, even with moving continents around, without postulating enhanced levels of CO[sub 2]. Early work indicated that pole centered continents could have snow free summers, but later work, with models with better physics, but poorer resolution seemed to contradict this conclusion. The authors apply the GENESIS (ver 1.02) general circulation model to this problem. Their conclusion is that with certain modifications to the application of this model, they could find pole-centered supercontinents which would be snow free in the summer.

  6. Development of a hydraulic model of the human systemic circulation

    NASA Technical Reports Server (NTRS)

    Sharp, M. K.; Dharmalingham, R. K.

    1999-01-01

    Physical and numeric models of the human circulation are constructed for a number of objectives, including studies and training in physiologic control, interpretation of clinical observations, and testing of prosthetic cardiovascular devices. For many of these purposes it is important to quantitatively validate the dynamic response of the models in terms of the input impedance (Z = oscillatory pressure/oscillatory flow). To address this need, the authors developed an improved physical model. Using a computer study, the authors first identified the configuration of lumped parameter elements in a model of the systemic circulation; the result was a good match with human aortic input impedance with a minimum number of elements. Design, construction, and testing of a hydraulic model analogous to the computer model followed. Numeric results showed that a three element model with two resistors and one compliance produced reasonable matching without undue complication. The subsequent analogous hydraulic model included adjustable resistors incorporating a sliding plate to vary the flow area through a porous material and an adjustable compliance consisting of a variable-volume air chamber. The response of the hydraulic model compared favorably with other circulation models.

  7. Asian Summer Monsoon Intraseasonal Variability in General Circulation Models

    SciTech Connect

    Sperber, K R; Annamalai, H

    2004-02-24

    The goals of this report are: (1) Analyze boreal summer Asian monsoon intraseasonal variability general circulation models--How well do the models represent the eastward and northward propagating components of the convection and how well do the models represent the interactive control that the western tropical Pacific rainfall exerts on the rainfall over India and vice-versa? (2) Role of air-sea interactions--prescribed vs. interactive ocean; and (3) Mean monsoon vs. variability.

  8. Continued Development and Application of Circulation Control Pneumatic Technology to Advanced Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Englar, Robert J.

    1998-01-01

    Personnel of the Georgia Tech Research Institute (GTRI) Aerospace and Transportation Lab have completed a four-year grant program to develop and evaluate the pneumatic aerodynamic technology known as Circulation Control (CC) or Circulation Control Wing (CCW) for advanced transport aircraft. This pneumatic technology, which employs low-level blowing from tangential slots over round or near-round trailing edges of airfoils, greatly augments the circulation around a lifting or control surface and thus enhances the aerodynamic forces and moments generated by that surface. Two-dimensional force augmentations as high as 80 times the input blowing momentum coefficient have been recorded experimentally for these blown devices, thus providing returns of 8000% on the jet momentum expended. A further benefit is the absence of moving parts such as mechanical flaps, slats, spoilers, ailerons, elevators and rudders from these pneumatic surfaces, or the use of only very small, simple, blown aerodynamic surfaces on synergistic designs which integrate the lift, drag and control surfaces. The application of these devices to advanced aircraft can offer significant benefits in their performance, efficiency, simplicity, reliability, economic cost of operation, noise reduction, and safety of flight. To further develop and evaluate this potential, this research effort was conducted by GTRI under grant for the NASA Langley Research Center, Applied Aerodynamics Division, Subsonic Aerodynamics Branch, between June 14, 1993 and May 31, 1997.

  9. Using the Gamma-Poisson Model to Predict Library Circulations.

    ERIC Educational Resources Information Center

    Burrell, Quentin L.

    1990-01-01

    Argues that the gamma mixture of Poisson processes, for all its perceived defects, can be used to make predictions regarding future library book circulations of a quality adequate for general management requirements. The use of the model is extensively illustrated with data from two academic libraries. (Nine references) (CLB)

  10. A general circulation model (GCM) parameterization of Pinatubo aerosols

    SciTech Connect

    Lacis, A.A.; Carlson, B.E.; Mishchenko, M.I.

    1996-04-01

    The June 1991 volcanic eruption of Mt. Pinatubo is the largest and best documented global climate forcing experiment in recorded history. The time development and geographical dispersion of the aerosol has been closely monitored and sampled. Based on preliminary estimates of the Pinatubo aerosol loading, general circulation model predictions of the impact on global climate have been made.

  11. Model-free adaptive control of advanced power plants

    SciTech Connect

    Cheng, George Shu-Xing; Mulkey, Steven L.; Wang, Qiang

    2015-08-18

    A novel 3-Input-3-Output (3.times.3) Model-Free Adaptive (MFA) controller with a set of artificial neural networks as part of the controller is introduced. A 3.times.3 MFA control system using the inventive 3.times.3 MFA controller is described to control key process variables including Power, Steam Throttle Pressure, and Steam Temperature of boiler-turbine-generator (BTG) units in conventional and advanced power plants. Those advanced power plants may comprise Once-Through Supercritical (OTSC) Boilers, Circulating Fluidized-Bed (CFB) Boilers, and Once-Through Supercritical Circulating Fluidized-Bed (OTSC CFB) Boilers.

  12. Relations between winter precipitation and atmospheric circulation simulated by the Geophysical Fluid Dynamics Laboratory general circulation model

    USGS Publications Warehouse

    McCabe, G.J.; Dettinger, M.D.

    1995-01-01

    General circulation model (GCM) simulations of atmospheric circulation are more reliable than GCM simulations of temperature and precipitation. In this study, temporal correlations between 700 hPa height anomalies simulated winter precipitation at eight locations in the conterminous United States are compared with corresponding correlations in observations. The objectives are to 1) characterize the relations between atmospheric circulation and winter precipitation simulated by the GFDL, GCM for selected locations in the conterminous USA, ii) determine whether these relations are similar to those found in observations of the actual climate system, and iii) determine if GFDL-simulated precipitation is forced by the same circulation patterns as in the real atmosphere. -from Authors

  13. Simulations of the Amazon basin circulation with a regional model

    SciTech Connect

    Horel, J.D.; Pechmann, J.B.; Hahmann, A.N.; Geisler, J.E. )

    1994-01-01

    Numerical simulations of the atmospheric circulation over tropical South America are performed with a regional model developed at the Pennsylvania State University and the National Center for Atmospheric Research and commonly referred to as the MM4. The authors focus on a 5-day period beginning at 1200 UTC 27 February 1990. The observed circulation is evaluated in terms of initialized analysis of standard meterological variables from the National Meteorological Center, outgoing longwave radiation from polar orbiting satellites, and surface observations. The NMC analysis are also used to specify the initial conditions, as well as provide the lateral boundary conditions, for the 5-day simulations. The impacts on the simulated circulation of major changes to the standard MM4 are assessed. When an improved treatment of radiative processes is included, excessive rainfall develops over then Andes Mountains and over the Amazon Basin. The excessive rainfall is concentrated in gridpoint' storms that are not climated when the surface physical parameterizations are improved. Modifications to the treatment of the vertical transport of moisture are required to diminish the excessive rainfall. Even with these and other changes included in the model, the simulated basin-averaged rainfall continues to exhibit unrealistic features. The improved, thought still imperfect, model simulations are used to diagnose the temporal and spatial evolution of the circulation with an emphasis on equatorial-subtropical interactions.

  14. Hemodynamic modeling of the intrarenal circulation.

    PubMed

    M'rabet Bensalah, K; Uehlinger, D; Kalicki, R; Czerwinska, J

    2013-12-01

    Three dimensional, time dependent numerical simulations of healthy and pathological conditions in a model kidney were performed. Blood flow in a kidney is not commonly investigated by computational approach, in contrast for example, to the flow in a heart. The flow in a kidney is characterized by relatively small Reynolds number (100 < Re < 0.01-laminar regime). The presented results give insight into the structure of such flow, which is hard to measure in vivo. The simulations have suggested that venous thrombosis is more likely than arterial thrombosis-higher shear rate observed. The obtained maximum velocity, as a result of the simulations, agrees with the observed in vivo measurements. The time dependent simulations show separation regimes present in the vicinity of the maximum pressure value. The pathological constriction introduced to the arterial geometry leads to the changes in separation structures. The constriction of a single vessel affects flow in the whole kidney. Pathology results in different flow rate values in healthy and affected branches, as well as, different pulsate cycle characteristic for the whole system.

  15. Integrated and spectral energetics of the GLAS general circulation model

    NASA Technical Reports Server (NTRS)

    Tenenbaum, J.

    1981-01-01

    Integrated and spectral error energetics of the Goddard Laboratory for Atmospheric Sciences (GLAS) general circulation model are compared with observations for periods in January 1975, 1976, and 1977. For two cases the model shows significant skill in predicting integrated energetics quantities out to two weeks, and for all three cases, the integrated monthly mean energetics show qualitative improvements over previous versions of the model in eddy kinetic energy and barotropic conversions. Fundamental difficulties remain with leakage of energy to the stratospheric level. General circulation model spectral energetics predictions are compared with the corresponding observational spectra on a day by day basis. Eddy kinetic energy can be correct while significant errors occur in the kinetic energy of wavenumber three. Single wavenumber dominance in eddy kinetic energy and the correlation of spectral kinetic and potential energy are demonstrated.

  16. Seasonal circulations in the Malay Peninsula Eastern continental shelf from a wave-tide-circulation coupled model

    NASA Astrophysics Data System (ADS)

    Tangang, Fredolin T.; Xia, Changsui; Qiao, Fangli; Juneng, Liew; Shan, Feng

    2011-09-01

    A wave-tide-circulation coupled model based on Princeton Ocean Model is established to study the seasonal circulation in the Malay Peninsula Eastern Continental Shelf region. The model successfully reconstructs the observed seasonal variation of the circulation in the region, as well as the main currents. The simulated tidal harmonic constants, sea surface temperature, and sea surface height anomaly agree with the observations well. The model results show that the upper-layer circulation in the region is mainly controlled by the monsoon winds, while there are two transitions in spring and fall. An anti-cyclonic eddy is present off the Peninsular Malaysia's east coast in summer, centered at 5°N and 105.5°E, both in the TOPEX/Poseidon data and in the model. Numerical experiments show that the wind stress curl and bathymetry steering are responsible for its formation.

  17. Reproducibility of Digital PCR Assays for Circulating Tumor DNA Analysis in Advanced Breast Cancer

    PubMed Central

    Hrebien, Sarah; O’Leary, Ben; Beaney, Matthew; Schiavon, Gaia; Fribbens, Charlotte; Bhambra, Amarjit; Johnson, Richard; Turner, Nicholas

    2016-01-01

    Circulating tumor DNA (ctDNA) analysis has the potential to allow non-invasive analysis of tumor mutations in advanced cancer. In this study we assessed the reproducibility of digital PCR (dPCR) assays of circulating tumor DNA in a cohort of patients with advanced breast cancer and assessed delayed plasma processing using cell free DNA preservative tubes. We recruited a cohort of 96 paired samples from 71 women with advanced breast cancer who had paired blood samples processed either immediately or delayed in preservative tubes with processing 48–72 hours after collection. Plasma DNA was analysed with multiplex digital PCR (mdPCR) assays for hotspot mutations in PIK3CA, ESR1 and ERBB2, and for AKT1 E17K. There was 94.8% (91/96) agreement in mutation calling between immediate and delayed processed tubes, kappa 0.88 95% CI 0.77–0.98). Discordance in mutation calling resulted from low allele frequency and likely stochastic effects. In concordant samples there was high correlation in mutant copies per ml plasma (r2 = 0.98; p<0.0001). There was elevation of total cell free plasma DNA concentrations in 10.3% of delayed processed tubes, although overall quantification of total cell free plasma DNA had similar prognostic effects in immediate (HR 3.6) and delayed (HR 3.0) tubes. There was moderate agreement in changes in allele fraction between sequential samples in quantitative mutation tracking (r = 0.84, p = 0.0002). Delayed processing of samples using preservative tubes allows for centralized ctDNA digital PCR mutation screening in advanced breast cancer. The potential of preservative tubes in quantitative mutation tracking requires further research. PMID:27760227

  18. Treatment of cloud radiative effects in general circulation models

    SciTech Connect

    Wang, W.C.; Dudek, M.P.; Liang, X.Z.; Ding, M.

    1996-04-01

    We participate in the Atmospheric Radiation Measurement (ARM) program with two objectives: (1) to improve the general circulation model (GCM) cloud/radiation treatment with a focus on cloud verticle overlapping and layer cloud optical properties, and (2) to study the effects of cloud/radiation-climate interaction on GCM climate simulations. This report summarizes the project progress since the Fourth ARM Science Team meeting February 28-March 4, 1994, in Charleston, South Carolina.

  19. Mars atmospheric dynamics as simulated by the NASA AMES General Circulation Model. I - The zonal-mean circulation

    NASA Astrophysics Data System (ADS)

    Haberle, R. M.; Pollack, J. B.; Barnes, J. R.; Zurek, R. W.; Leovy, C. B.; Murphy, J. R.; Lee, H.; Schaeffer, J.

    1993-02-01

    The characteristics of the zonal-mean circulation and how it responds to seasonal variations and dust loading are described. This circulation is the main momentum-containing component of the general circulation, and it plays a dominant role in the budgets of heat and momentum. It is shown that in many ways the zonal-mean circulation on Mars, at least as simulated by the model, is similar to that on earth, having Hadley and Ferrel cells and high-altitude jet streams. However, the Martian systems tend to be deeper, more intense, and much more variable with season. Furthermore, the radiative effects of suspended dust particles, even in small amounts, have a major influence on the general circulation.

  20. Contribution towards statistical intercomparison of general circulation models

    SciTech Connect

    Sengupta, S.; Boyle, J.

    1995-06-01

    The Atmospheric Model Intercomparison Project (AMIP) of the World Climate Research Programme`s Working Group on Numerical Experimentation (WGNE) is an ambitious attempt to comprehensively intercompare atmospheric General Circulation Models (GCMs). The participants in AMIP simulate the global atmosphere for the decade 1979 to 1988 using, a common solar constant and Carbon Dioxide(CO{sub 2}) concentration and a common monthly averaged sea surface temperature (SST) and sea ice data set. In this work we attempt to present a statistical framework to address the difficult task of model intercomparison and verification.

  1. Comparing a quasi-3D to a full 3D nearshore circulation model: SHORECIRC and ROMS

    USGS Publications Warehouse

    Haas, K.A.; Warner, J.C.

    2009-01-01

    Predictions of nearshore and surf zone processes are important for determining coastal circulation, impacts of storms, navigation, and recreational safety. Numerical modeling of these systems facilitates advancements in our understanding of coastal changes and can provide predictive capabilities for resource managers. There exists many nearshore coastal circulation models, however they are mostly limited or typically only applied as depth integrated models. SHORECIRC is an established surf zone circulation model that is quasi-3D to allow the effect of the variability in the vertical structure of the currents while maintaining the computational advantage of a 2DH model. Here we compare SHORECIRC to ROMS, a fully 3D ocean circulation model which now includes a three dimensional formulation for the wave-driven flows. We compare the models with three different test applications for: (i) spectral waves approaching a plane beach with an oblique angle of incidence; (ii) monochromatic waves driving longshore currents in a laboratory basin; and (iii) monochromatic waves on a barred beach with rip channels in a laboratory basin. Results identify that the models are very similar for the depth integrated flows and qualitatively consistent for the vertically varying components. The differences are primarily the result of the vertically varying radiation stress utilized by ROMS and the utilization of long wave theory for the radiation stress formulation in vertical varying momentum balance by SHORECIRC. The quasi-3D model is faster, however the applicability of the fully 3D model allows it to extend over a broader range of processes, temporal, and spatial scales. ?? 2008 Elsevier Ltd.

  2. Advanced Chemistry Basins Model

    SciTech Connect

    Blanco, Mario; Cathles, Lawrence; Manhardt, Paul; Meulbroek, Peter; Tang, Yongchun

    2003-02-13

    The objective of this project is to: (1) Develop a database of additional and better maturity indicators for paleo-heat flow calibration; (2) Develop maturation models capable of predicting the chemical composition of hydrocarbons produced by a specific kerogen as a function of maturity, heating rate, etc.; assemble a compositional kinetic database of representative kerogens; (3) Develop a 4 phase equation of state-flash model that can define the physical properties (viscosity, density, etc.) of the products of kerogen maturation, and phase transitions that occur along secondary migration pathways; (4) Build a conventional basin model and incorporate new maturity indicators and data bases in a user-friendly way; (5) Develop an algorithm which combines the volume change and viscosities of the compositional maturation model to predict the chemistry of the hydrocarbons that will be expelled from the kerogen to the secondary migration pathways; (6) Develop an algorithm that predicts the flow of hydrocarbons along secondary migration pathways, accounts for mixing of miscible hydrocarbon components along the pathway, and calculates the phase fractionation that will occur as the hydrocarbons move upward down the geothermal and fluid pressure gradients in the basin; and (7) Integrate the above components into a functional model implemented on a PC or low cost workstation.

  3. Advanced Turbulence Modeling Concepts

    NASA Technical Reports Server (NTRS)

    Shih, Tsan-Hsing

    2005-01-01

    The ZCET program developed at NASA Glenn Research Center is to study hydrogen/air injection concepts for aircraft gas turbine engines that meet conventional gas turbine performance levels and provide low levels of harmful NOx emissions. A CFD study for ZCET program has been successfully carried out. It uses the most recently enhanced National combustion code (NCC) to perform CFD simulations for two configurations of hydrogen fuel injectors (GRC- and Sandia-injector). The results can be used to assist experimental studies to provide quick mixing, low emission and high performance fuel injector designs. The work started with the configuration of the single-hole injector. The computational models were taken from the experimental designs. For example, the GRC single-hole injector consists of one air tube (0.78 inches long and 0.265 inches in diameter) and two hydrogen tubes (0.3 inches long and 0.0226 inches in diameter opposed at 180 degree). The hydrogen tubes are located 0.3 inches upstream from the exit of the air element (the inlet location for the combustor). To do the simulation, the single-hole injector is connected to a combustor model (8.16 inches long and 0.5 inches in diameter). The inlet conditions for air and hydrogen elements are defined according to actual experimental designs. Two crossing jets of hydrogen/air are simulated in detail in the injector. The cold flow, reacting flow, flame temperature, combustor pressure and possible flashback phenomena are studied. Two grid resolutions of the numerical model have been adopted. The first computational grid contains 0.52 million elements, the second one contains over 1.3 million elements. The CFD results have shown only about 5% difference between the two grid resolutions. Therefore, the CFD result obtained from the model of 1.3-million grid resolution can be considered as a grid independent numerical solution. Turbulence models built in NCC are consolidated and well tested. They can handle both coarse and

  4. A parallel coupled oceanic-atmospheric general circulation model

    SciTech Connect

    Wehner, M.F.; Bourgeois, A.J.; Eltgroth, P.G.; Duffy, P.B.; Dannevik, W.P.

    1994-12-01

    The Climate Systems Modeling group at LLNL has developed a portable coupled oceanic-atmospheric general circulation model suitable for use on a variety of massively parallel (MPP) computers of the multiple instruction, multiple data (MIMD) class. The model is composed of parallel versions of the UCLA atmospheric general circulation model, the GFDL modular ocean model (MOM) and a dynamic sea ice model based on the Hiber formulation extracted from the OPYC ocean model. The strategy to achieve parallelism is twofold. One level of parallelism is accomplished by applying two dimensional domain decomposition techniques to each of the three constituent submodels. A second level of parallelism is attained by a concurrent execution of AGCM and OGCM/sea ice components on separate sets of processors. For this functional decomposition scheme, a flux coupling module has been written to calculate the heat, moisture and momentum fluxes independent of either the AGCM or the OGCM modules. The flux coupler`s other roles are to facilitate the transfer of data between subsystem components and processors via message passing techniques and to interpolate and aggregate between the possibly incommensurate meshes.

  5. Obliquity Experiments with a Mars General Circulation Model

    NASA Technical Reports Server (NTRS)

    Harberle, R. M.; Schaeffer, J.; Cuzzi, Jeffery N. (Technical Monitor)

    1995-01-01

    We have simulated the seasonal variation of the general circulation on Mars for obliquities of 0deg and 60deg. These obliquities represent the minimum and maximum values the planet has experienced during the past 10(exp 7) years (e.g., Laskar and Robutel, 1993, Nature, 361, 608-614). The model we use is the NASA/Ames Mars General Circulation Model (Pollack et al., 1993, J. Geophys. Res. 98, 3149-3181). We vary only the obliquity; all other model parameters are as in Pollack et al. At high obliquity, the model shows dramatic seasonal variations in the polar caps and in the structure and intensity of the circulation. At the solstices the winter cap extends to the equator. Thus, surface temperatures throughout the entire winter hemisphere are fixed at the CO2 frost point. During summer surface temperatures at the poles reach 269K in the north and 295K in the south. The most notable changes to the circulation at solstice compared to our standard runs are a general weakening of the winter westerlies, a Hadley cell of greater latitudinal extent, and the development of very strong, possibly unstable, low-level jets in midlatitudes of the summer hemisphere. Surface stresses associated with these jets are sufficient to raise dust continuously. Thus, dust storms should be frequent features of the high obliquity climate. This result is independent of any desorbed regolith CO2 which would raise mean surface pressures. At zero obliquity the structure of the circulation resembles that of present day equinox conditions modulated by the varying insolation associated with orbital eccentricity. Notable features include equatorial superrotation, asymmetric Hadley cells, and stronger poleward heat fluxes in the northern hemisphere. Since the poles do not receive solar energy at any time of year, permanent caps form which extend to about 70deg in each hemisphere. However, the north permanent cap is growing at a rate 40% faster than the south cap. This is due to the differences in

  6. Tropical disturbances in relation to general circulation modeling

    NASA Technical Reports Server (NTRS)

    Estoque, M. A.

    1982-01-01

    The initial results of an evaluation of the performance of the Goddard Laboratory of Atmospheric Simulation general circulation model depicting the tropical atmosphere during the summer are presented. Because the results show the existence of tropical wave disturbances throughout the tropics, the characteristics of synoptic disturbances over Africa were studied and a synoptic case study of a selected disturbance in this area was conducted. It is shown that the model is able to reproduce wave type synoptic disturbances in the tropics. The findings show that, in one of the summers simulated, the disturbances are predominantly closed vortices; in another summer, the predominant disturbances are open waves.

  7. Modelling wildfire activity in Iberia with different Atmospheric Circulation WTs

    NASA Astrophysics Data System (ADS)

    Sousa, P. M.; Trigo, R.; Pereira, M. G.; Rasilla, D.; Gouveia, C.

    2012-04-01

    This work focuses on the spatial and temporal variability of burnt area (BA) for the entire Iberian Peninsula (IP) and on the construction of statistical models to reproduce the inter-annual variability, based on Weather Types Classification (WTC). A common BA dataset was assembled for the first time for the entire Iberian Peninsula, by merging BA records for the 66 administrative regions of Portugal and Spain. A normalization procedure was then applied to the various size regions before performing a k-means cluster analysis to identify large areas characterized by similar fire regimes. The most compelling results were obtained for 4 clusters (Northwestern, Northern, Southwestern and Eastern) whose spatial patterns and seasonal fire regimes are shown to be related with constraining factors such as topography, vegetation cover and climate conditions. The response of fire burnt surface at monthly time scales to both long-term climatic pre-conditions and short-term synoptic forcing was assessed through correlation and regression analysis using: (i) temperature and precipitation from 2 to 7 months in advance to fire peak season; (ii) synoptic weather patterns derived from 11 distinct classifications derived under the COSTaction-733. Different responses were obtained for each of the considered regions: (i) a relevant link between BA and short-term synoptic forcing (represented by monthly frequencies of WTC) was identified for all clusters; (ii) long-term climatic preconditioning was relevant for all but one cluster (Northern). Taking into account these links, we developed stepwise regression models with the aim of reproducing the observed BA series (i.e. in hindcast mode). These models were based on the best climatic and synoptic circulation predictors identified previously. All models were cross-validated and their performance varies between clusters, though models exclusively based on WTCs tend to better reproduce annual BA time series than those only based on pre

  8. Relaxation oscillations in an idealized ocean circulation model

    NASA Astrophysics Data System (ADS)

    Roberts, Andrew; Saha, Raj

    2016-06-01

    This work is motivated by a desire to understand transitions between stable equilibria observed in Stommel's 1961 thermohaline circulation model. We adapt the model, including a forcing parameter as a dynamic slow variable. The resulting model is a piecewise-smooth, three time-scale system. The model is analyzed using geometric singular perturbation theory to demonstrate the existence of attracting periodic orbits. The system is capable of producing classical relaxation oscillations as expected, but there is also a parameter regime in which the model exhibits small amplitude oscillations known as canard cycles. Forcing the model with obliquity variations from the last 100,000 years produces oscillations that are modulated in amplitude and frequency. The output shows similarities with important features of the climate proxy data of the same period.

  9. Analysis of snow feedbacks in 14 general circulation models

    NASA Technical Reports Server (NTRS)

    Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Chalita, S.; Colman, R.; Dazlich, D. A.; Del Genio, A. D.; Keup, E.; Lacis, A.; Le Treut, H.

    1994-01-01

    Snow feedbacks produced by 14 atmospheric general circulation models have been analyzed through idealized numerical experiments. Included in the analysis is an investigation of the surface energy budgets of the models. Negative or weak positive snow feedbacks occurred in some of the models, while others produced strong positive snow feedbacks. These feedbacks are due not only to melting snow, but also to increases in boundary temperature, changes in air temperature, changes in water vapor, and changes in cloudiness. As a result, the net response of each model is quite complex. We analyze in detail the responses of one model with a strong positive snow feedback and another with a weak negative snow feedback. Some of the models include a temperature dependence of the snow albedo, and this has significantly affected the results.

  10. Integrated and spectral energetics of the GLAS general circulation model

    NASA Technical Reports Server (NTRS)

    Tenenbaum, J.

    1982-01-01

    Integrated and spectral error energetics of the GLAS General circulation model are compared with observations for periods in January 1975, 1976, and 1977. For two cases the model shows significant skill in predicting integrated energetics quantities out to two weeks, and for all three cases, the integrated monthly mean energetics show qualitative improvements over previous versions of the model in eddy kinetic energy and barotropic conversions. Fundamental difficulties remain with leakage of energy to the stratospheric level, particularly above strong initial jet streams associated in part with regions of steep terrain. The spectral error growth study represents the first comparison of general circulation model spectral energetics predictions with the corresponding observational spectra on a day by day basis. The major conclusion is that eddy kinetics energy can be correct while significant errors occur in the kinetic energy of wavenumber 3. Both the model and observations show evidence of single wavenumber dominance in eddy kinetic energy and the correlation of spectral kinetics and potential energy.

  11. Ocean General Circulation From a Global Eddy-Resolving Model

    NASA Astrophysics Data System (ADS)

    Semtner, Albert J.; Chervin, Robert M.

    1992-04-01

    A concerted effort has been made to simulate the global ocean circulation with resolved eddies, using a highly optimized model on the best available supercomputer. An earlier 20-year spin-up has been extended for 12.5 additional years: the first 2.5 with continued annual mean forcing and the final 10.0 with climatological monthly forcing. Model output archived at 3-day intervals has been analyzed into mean fields, standard deviations, products, and covariances on monthly, annual, and multiyear time scales. The multiyear results are examined here in order to give insight into the general circulation of the world ocean. The three-dimensional flow fields of the model are quite realistic, even though resolution of eddies in high latitudes is marginal with a 0.5°, 20-level grid. The use of seasonal forcing improves the simulation, especially in the tropics and high northern latitudes. Mid-latitude gyre circulations, western boundary currents, zonal equatorial flows, and the Antarctic Circumpolar Current (ACC) all show mean and eddy characteristics similar to those observed. There is also some indication of eddy intensification of the mean flow of the ACC and of separated boundary jets. A global thermohaline circulation of North Atlantic Deep Water is identified in deep western boundary currents connected by the ACC. This deep circulation rises mainly in the equatorial Pacific. Several zonal jets are an integral part of this circulation near the equator. The deep flow rises toward the surface in a series of switchbacks. Much of the thermohaline return flow then follows an eddy-rich warm-water route through the Indonesian archipelago and around the southern tip of Africa. However, some intermediate level portions of the thermohaline circulation return south into the ACC and follow a cold water route through the Drake Passage. The representation of a global "conveyor belt" circulation with narrow and relatively high-speed currents along most of its path may be the most

  12. Numerical Model Studies of the Martian Mesoscale Circulations

    NASA Technical Reports Server (NTRS)

    Segal, Moti; Arritt, Raymond W.

    1997-01-01

    The study objectives were to evaluate by numerical modeling various possible mesoscale circulation on Mars and related atmospheric boundary layer processes. The study was in collaboration with J. Tillman of the University of Washington (who supported the study observationally). Interaction has been made with J. Prusa of Iowa State University in numerical modeling investigation of dynamical effects of topographically-influenced flow. Modeling simulations included evaluations of surface physical characteristics on: (i) the Martian atmospheric boundary layer and (ii) their impact on thermally and dynamically forced mesoscale flows. Special model evaluations were made in support of selection of the Pathfinder landing sites. J. Tillman's finding of VL-2 inter-annual temperature difference was followed by model simulations attempting to point out the forcing for this feature. Publication of the results in the reviewed literature in pending upon completion of the manuscripts in preparation as indicated later.

  13. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Dimenna, R; Tamburello, D

    2011-02-14

    height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. One of the main objectives in the waste processing is to provide feed of a uniform slurry composition at a certain weight percentage (e.g. typically {approx}13 wt% at SRS) over an extended period of time. In preparation of the sludge for slurrying, several important questions have been raised with regard to sludge suspension and mixing of the solid suspension in the bulk of the tank: (1) How much time is required to prepare a slurry with a uniform solid composition? (2) How long will it take to suspend and mix the sludge for uniform composition in any particular waste tank? (3) What are good mixing indicators to answer the questions concerning sludge mixing stated above in a general fashion applicable to any waste tank/slurry pump geometry and fluid/sludge combination?

  14. (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.

  15. Using a Gravity Model to Predict Circulation in a Public Library System.

    ERIC Educational Resources Information Center

    Ottensmann, John R.

    1995-01-01

    Describes the development of a gravity model based upon principles of spatial interaction to predict the circulation of libraries in the Indianapolis-Marion County Public Library (Indiana). The model effectively predicted past circulation figures and was tested by predicting future library circulation, particularly for a new branch library.…

  16. Circulation Control Model Experimental Database for CFD Validation

    NASA Technical Reports Server (NTRS)

    Paschal, Keith B.; Neuhart, Danny H.; Beeler, George B.; Allan, Brian G.

    2012-01-01

    A 2D circulation control wing was tested in the Basic Aerodynamic Research Tunnel at the NASA Langley Research Center. A traditional circulation control wing employs tangential blowing along the span over a trailing-edge Coanda surface for the purpose of lift augmentation. This model has been tested extensively at the Georgia Tech Research Institute for the purpose of performance documentation at various blowing rates. The current study seeks to expand on the previous work by documenting additional flow-field data needed for validation of computational fluid dynamics. Two jet momentum coefficients were tested during this entry: 0.047 and 0.114. Boundary-layer transition was investigated and turbulent boundary layers were established on both the upper and lower surfaces of the model. Chordwise and spanwise pressure measurements were made, and tunnel sidewall pressure footprints were documented. Laser Doppler Velocimetry measurements were made on both the upper and lower surface of the model at two chordwise locations (x/c = 0.8 and 0.9) to document the state of the boundary layers near the spanwise blowing slot.

  17. Modeling waves and circulation in Lake Pontchartrain, Louisiana

    USGS Publications Warehouse

    Signell, Richard P.; List, Jeffrey H.

    1997-01-01

    The U.S. Geological Survey is conducting a study of storm-driven sediment resuspension and transport in Lake Pontchartrain, Louisiana. Two critical processes related to sediment transport in the lake are (1) the resuspension of sediments due to wind-generated storm waves and (2) the movement of resuspended material by lake currents during storm wind events. The potential for sediment resuspension is being studied with the wave prediction model which simulates local generation of waves by wind and shallow-water effects on waves (refraction, shoaling, bottom friction, and breaking). Long-term wind measurements are then used to determine the regional "climate" of bottom orbital velocity (showing the spatial and temporal variability of wave-induced currents at the bottom). The circulation of the lake is being studied with a three-dimensional hydrodynamic model. Results of the modeling effort indicate that remote forcing due to water levels in Mississippi Sound dominate the circulation near the passes in the eastern end of the lake, while local wind forcing dominates water movement in the western end. During typical storms with winds from the north-northeast or the south-southeast, currents along the south coast near New Orleans generally transport material westward, while material in the central region moves against the wind. When periods of sustained winds are followed by a drop in coastal sea level, a large amount of suspended sediment can be flushed from the lake.

  18. 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.

  19. Circulation and rainfall climatology of a 10-year (1979 - 1988) integration with the Goddard Laboratory for atmospheres general circulation model

    NASA Technical Reports Server (NTRS)

    Kim, J.-H.; Sud, Y. C.

    1993-01-01

    A 10-year (1979-1988) integration of Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) under Atmospheric Model Intercomparison Project (AMIP) is analyzed and compared with observation. The first momentum fields of circulation variables and also hydrological variables including precipitation, evaporation, and soil moisture are presented. Our goals are (1) to produce a benchmark documentation of the GLA GCM for future model improvements; (2) to examine systematic errors between the simulated and the observed circulation, precipitation, and hydrologic cycle; (3) to examine the interannual variability of the simulated atmosphere and compare it with observation; and (4) to examine the ability of the model to capture the major climate anomalies in response to events such as El Nino and La Nina. The 10-year mean seasonal and annual simulated circulation is quite reasonable compared to the analyzed circulation, except the polar regions and area of high orography. Precipitation over tropics are quite well simulated, and the signal of El Nino/La Nina episodes can be easily identified. The time series of evaporation and soil moisture in the 12 biomes of the biosphere also show reasonable patterns compared to the estimated evaporation and soil moisture.

  20. A river flow routing scheme for general circulation models

    NASA Astrophysics Data System (ADS)

    Arora, Vivek K.; Chiew, Francis H. S.; Grayson, Rodger B.

    1999-06-01

    The routing of runoff estimates from General Circulation Models (GCMs) is important to model river flow from large river basins and to estimate freshwater inflow into the oceans. Present routing approaches use arbitrary constants and empirical equations to determine travel times between the GCM grid cells. A new river flow routing scheme is developed, which uses physical catchment and river channel information and river discharge data. The scheme uses surface runoff and deep percolation data from land surface parameterization schemes, and routing is performed via linear surface and groundwater reservoirs. Geomorphological relationships between mean annual river discharge and other physical variables are used to interpolate existing information to define the channel morphology for the digital river networks at the routing model resolution. Applications of the routing scheme to the Mississippi and Amazon River Basins indicate that it performs adequately. The scheme does not require the calibration of parameters and can thus be easily used in GCMs.

  1. 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.

  2. Multi-purpose utility of circulating plasma DNA testing in patients with advanced cancers.

    PubMed

    Perkins, Geraldine; Yap, Timothy A; Pope, Lorna; Cassidy, Amy M; Dukes, Juliet P; Riisnaes, Ruth; Massard, Christophe; Cassier, Philippe A; Miranda, Susana; Clark, Jeremy; Denholm, Katie A; Thway, Khin; Gonzalez De Castro, David; Attard, Gerhardt; Molife, L Rhoda; Kaye, Stan B; Banerji, Udai; de Bono, Johann S

    2012-01-01

    Tumor genomic instability and selective treatment pressures result in clonal disease evolution; molecular stratification for molecularly targeted drug administration requires repeated access to tumor DNA. We hypothesized that circulating plasma DNA (cpDNA) in advanced cancer patients is largely derived from tumor, has prognostic utility, and can be utilized for multiplex tumor mutation sequencing when repeat biopsy is not feasible. We utilized the Sequenom MassArray System and OncoCarta panel for somatic mutation profiling. Matched samples, acquired from the same patient but at different time points were evaluated; these comprised formalin-fixed paraffin-embedded (FFPE) archival tumor tissue (primary and/or metastatic) and cpDNA. The feasibility, sensitivity, and specificity of this high-throughput, multiplex mutation detection approach was tested utilizing specimens acquired from 105 patients with solid tumors referred for participation in Phase I trials of molecularly targeted drugs. The median cpDNA concentration was 17 ng/ml (range: 0.5-1600); this was 3-fold higher than in healthy volunteers. Moreover, higher cpDNA concentrations associated with worse overall survival; there was an overall survival (OS) hazard ratio of 2.4 (95% CI 1.4, 4.2) for each 10-fold increase in cpDNA concentration and in multivariate analyses, cpDNA concentration, albumin, and performance status remained independent predictors of OS. These data suggest that plasma DNA in these cancer patients is largely derived from tumor. We also observed high detection concordance for critical 'hot-spot' mutations (KRAS, BRAF, PIK3CA) in matched cpDNA and archival tumor tissue, and important differences between archival tumor and cpDNA. This multiplex sequencing assay can be utilized to detect somatic mutations from plasma in advanced cancer patients, when safe repeat tumor biopsy is not feasible and genomic analysis of archival tumor is deemed insufficient. Overall, circulating nucleic acid

  3. Circulating fluidized bed tehnology in biomass combustion-performance, advances and experiences

    SciTech Connect

    Mutanen, K.I.

    1995-11-01

    Development of fluidized bed combustion (FBC) was started both in North America and in Europe in the 1960`s. In Europe and especially in Scandinavia the major driving force behind the development was the need to find new more efficient technologies for utilization of low-grade fuels like different biomasses and wastes. Both bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) technologies were under intensive R&D,D efforts and have now advanced to dominating role in industrial and district heating power plant markets in Europe. New advanced CFB designs are now entering the markets. In North America and especially in the US the driving force behind the FBC development was initially the need to utilize different types of coals in a more efficient and environmentally acceptable way. The present and future markets seem to be mainly in biomass and multifuel applications where there is benefit from high combustion efficiency, high fuel flexibility and low emissions such as in the pulp and paper industry. The choice between CFB technology and BFB technology is based on selected fuels, emission requirements, plant size and on technical and economic feasibility. Based on Scandinavian experience there is vast potential in the North American industry to retrofit existing oil fired, pulverized coal fired, chemical recovery or grate fired boilers with FBC systems or to build a new FBC based boiler plant. This paper will present the status of CFB technologies and will compare technical and economic feasibility of CFB technology to CFB technology to BFB and also to other combustion methods. Power plant projects that are using advanced CFB technology e.g. Ahlstrom Pyroflow Compact technology for biomass firing and co-firing of biomass with other fuels will also be introduced.

  4. Advanced glycation end products, carotid atherosclerosis, and circulating endothelial progenitor cells in patients with end-stage renal disease.

    PubMed

    Ueno, Hiroki; Koyama, Hidenori; Fukumoto, Shinya; Tanaka, Shinji; Shoji, Takuhito; Shoji, Tetsuo; Emoto, Masanori; Tahara, Hideki; Inaba, Masaaki; Kakiya, Ryusuke; Tabata, Tsutomu; Miyata, Toshio; Nishizawa, Yoshiki

    2011-04-01

    Numbers of endothelial progenitor cells (EPCs) have been shown to be decreased in subjects with end-stage renal disease (ESRD), the mechanism of which remained poorly understood. In this study, mutual association among circulating EPC levels, carotid atherosclerosis, serum pentosidine, and skin autofluorescence, a recently established noninvasive measure of advanced glycation end products accumulation, was examined in 212 ESRD subjects undergoing hemodialysis. Numbers of circulating EPCs were measured as CD34+ CD133+ CD45(low) VEGFR2+ cells and progenitor cells as CD34+ CD133+ CD45(low) fraction by flow cytometry. Skin autofluorescence was assessed by the autofluorescence reader; and serum pentosidine, by enzyme-linked immunosorbent assay. Carotid atherosclerosis was determined as intimal-medial thickness (IMT) measured by ultrasound. Circulating EPCs were significantly and inversely correlated with skin autofluorescence in ESRD subjects (R = -0.216, P = .002), but not with serum pentosidine (R = -0.079, P = .25). Circulating EPCs tended to be inversely associated with IMT (R = -0.125, P = .069). Intimal-medial thickness was also tended to be correlated positively with skin autofluorescence (R = 0.133, P = .054) and significantly with serum pentosidine (R = 0.159, P = .019). Stepwise multiple regression analyses reveal that skin autofluorescence, but not serum pentosidine and IMT, was independently associated with low circulating EPCs. Of note, skin autofluorescence was also inversely and independently associated with circulating progenitor cells. Thus, tissue accumulated, but not circulating, advanced glycation end products may be a determinant of a decrease in circulating EPCs in ESRD subjects.

  5. Advanced glycation end products, carotid atherosclerosis, and circulating endothelial progenitor cells in patients with end-stage renal disease.

    PubMed

    Ueno, Hiroki; Koyama, Hidenori; Fukumoto, Shinya; Tanaka, Shinji; Shoji, Takuhito; Shoji, Tetsuo; Emoto, Masanori; Tahara, Hideki; Inaba, Masaaki; Kakiya, Ryusuke; Tabata, Tsutomu; Miyata, Toshio; Nishizawa, Yoshiki

    2011-04-01

    Numbers of endothelial progenitor cells (EPCs) have been shown to be decreased in subjects with end-stage renal disease (ESRD), the mechanism of which remained poorly understood. In this study, mutual association among circulating EPC levels, carotid atherosclerosis, serum pentosidine, and skin autofluorescence, a recently established noninvasive measure of advanced glycation end products accumulation, was examined in 212 ESRD subjects undergoing hemodialysis. Numbers of circulating EPCs were measured as CD34+ CD133+ CD45(low) VEGFR2+ cells and progenitor cells as CD34+ CD133+ CD45(low) fraction by flow cytometry. Skin autofluorescence was assessed by the autofluorescence reader; and serum pentosidine, by enzyme-linked immunosorbent assay. Carotid atherosclerosis was determined as intimal-medial thickness (IMT) measured by ultrasound. Circulating EPCs were significantly and inversely correlated with skin autofluorescence in ESRD subjects (R = -0.216, P = .002), but not with serum pentosidine (R = -0.079, P = .25). Circulating EPCs tended to be inversely associated with IMT (R = -0.125, P = .069). Intimal-medial thickness was also tended to be correlated positively with skin autofluorescence (R = 0.133, P = .054) and significantly with serum pentosidine (R = 0.159, P = .019). Stepwise multiple regression analyses reveal that skin autofluorescence, but not serum pentosidine and IMT, was independently associated with low circulating EPCs. Of note, skin autofluorescence was also inversely and independently associated with circulating progenitor cells. Thus, tissue accumulated, but not circulating, advanced glycation end products may be a determinant of a decrease in circulating EPCs in ESRD subjects. PMID:20494372

  6. A stratiform cloud parameterization for General Circulation Models

    SciTech Connect

    Ghan, S.J.; Leung, L.R.; Chuang, C.C.; Penner, J.E.; McCaa, J.

    1994-05-01

    The crude treatment of clouds in General Circulation Models (GCMs) is widely recognized as a major limitation in the application of these models to predictions of global climate change. The purpose of this project is to develop a paxameterization for stratiform clouds in GCMs that expresses stratiform clouds in terms of bulk microphysical properties and their subgrid variability. In this parameterization, precipitating cloud species are distinguished from non-precipitating species, and the liquid phase is distinguished from the ice phase. The size of the non-precipitating cloud particles (which influences both the cloud radiative properties and the conversion of non-precipitating cloud species to precipitating species) is determined by predicting both the mass and number concentrations of each species.

  7. Validation of winter atmospheric circulation over Europe and the North Atlantic in CMIP5 global circulation model outputs

    NASA Astrophysics Data System (ADS)

    Stryhal, Jan; Huth, Radan

    2016-04-01

    An analysis of winter atmospheric circulation over Europe is carried out based on outputs of historical runs of thirty-two CMIP5 global circulation models (GCMs) (1961-2000). GCMs are validated against five reanalysis datasets, in terms of the frequency and persistence of circulation types (CTs). Previous research has shown that diverse results can be obtained if different classification methods are employed. Therefore, to achieve reliable results, CTs are successively defined by eight methods included in the COST733 software and for four domains (Europe, British Isles, Central Europe, and Eastern Mediterranean). The multi-model ensemble median in most cases shows an overestimation of CTs with (south)western advection over Europe, and over- and underestimation of cyclonic and anticyclonic types, respectively, both in their frequency and spatial extent of the respective pressure systems. The size and significance of these biases are, however, considerably dependent on the chosen classification method, domain, and even the reanalysis dataset.

  8. A hierarchy of thermohaline circulation models. Final report

    SciTech Connect

    Cessi, P.; Young, W.R.

    1998-04-01

    The objectives of this effort were: (1) to understand the variability caused by the competitive roles of salt and heat in the ocean circulation; (2) to understand the effect of differential advection of active tracers, such as temperature, salinity and angular momentum; and (3) to improve the parametrization of convection in models of the ocean circulation. One result of the project is the discovery that the characteristics of the quasi-periodic centennial and millennial oscillations found in OGCM`s, associated with alternating suppression and activation of high latitude convection, are extremely sensitive to the salinity flux and specific choice of convective adjustment scheme. In particular, the period of the oscillation depends crucially on the salinity fluxes (whether deterministic or with a stochastic component) and can be arbitrarily long. This result has clarified that these long-period oscillations (termed flushes) are not the result of the excitation of an intrinsic linear eigenmode of the system, but rather are relaxation-oscillations towards one of the several equilibria available to the system. This implies that it is the amplitude, rather than the period, of the oscillation which is almost independent of the salinity flux.

  9. Climate predictability experiments with a general circulation model

    NASA Astrophysics Data System (ADS)

    Bengtsson, L.; Arpe, K.; Roeckner, E.; Schulzweida, U.

    1996-03-01

    The atmospheric response to the evolution of the global sea surface temperatures from 1979 to 1992 is studied using the Max-Planck-Institut 19 level atmospheric general circulation model, ECHAM3 at T 42 resolution. Five separate 14-year integrations are performed and results are presented for each individual realization and for the ensemble-averaged response. The results are compared to a 30-year control integration using a climate monthly mean state of the sea surface temperatures and to analysis data. It is found that the ECHAM3 model, by and large, does reproduce the observed response pattern to El Nino and La Niña. During the El Nino events, the subtropical jet streams in both hemispheres are intensified and displaced equatorward, and there is a tendency towards weak upper easterlies over the equator. The Southern Oscillation is a very stable feature of the integrations and is accurately reproduced in all experiments. The inter-annual variability at middle- and high-latitudes, on the other hand, is strongly dominated by chaotic dynamics, and the tropical SST forcing only modulates the atmospheric circulation. The potential predictability of the model is investigated for six different regions. Signal to noise ratio is large in most parts of the tropical belt, of medium strength in the western hemisphere and generally small over the European area. The ENSO signal is most pronounced during the boreal spring. A particularly strong signal in the precipitation field in the extratropics during spring can be found over the southern United States. Western Canada is normally warmer during the warm ENSO phase, while northern Europe is warmer than normal during the ENSO cold phase. The reason is advection of warm air due to a more intense Pacific low than normal during the warm ENSO phase and a more intense Icelandic low than normal during the cold ENSO phase, respectively.

  10. 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).

  11. The Madden-Julian Oscillation in General Circulation Models

    SciTech Connect

    Sperber, K R; Gleckler, P J; Doutriaux, C; Groups, A M; Groups, C M; Slingo, J M; Inness, P M; Gualdi, S; Li, W

    2003-10-27

    A methodology is utilized to analyze in a standardized fashion the Madden-Julian Oscillation (MJO) in general circulation models. This is attained by projecting 20-100 day bandpass filtered outgoing longwave radiation (OLR) from the models onto the two leading empirical orthogonal functions (EOF's) of observed OLR that characterize the propagation of MJO convection from the Indian Ocean to the central Pacific Ocean. The resulting principal component time series are then screened to isolate boreal winters during which they exhibit a lead-lag relationship consistent with observations. This PC subset is used for linear regression to determine the ability of the models to simulate the observed spacetime variability of the MJO. The vast majority of models underestimate the amplitude of the MJO convective anomalies by a factor of two or more, and the eastward propagation of convection is less coherent than observed, typically. For a given family of models, coupling to an ocean leads to better organization of the large-scale convection. The low-level moisture convergence mechanism for eastward propagation is represented in limited cases, as is the vertical structure of the MJO.

  12. Sensitivity simulations of superparameterised convection in a general circulation model

    NASA Astrophysics Data System (ADS)

    Rybka, Harald; Tost, Holger

    2015-04-01

    Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation. This study presents different simulations of an adapted Earth System Model (ESM) connected to a CRM which acts as a superparameterisation. Simulations have been performed with the ECHAM/MESSy atmospheric chemistry (EMAC) model comparing conventional GCM runs (including convection and large-scale cloud parameterisations) with the improved superparameterised EMAC (SP-EMAC) modeling one year with prescribed sea surface temperatures and sea ice content. The sensitivity of atmospheric temperature, precipiation patterns, cloud amount and types is observed changing the embedded CRM represenation (orientation, width, no. of CRM cells, 2D vs. 3D). Additionally, we also evaluate the radiation balance with the new model configuration, and systematically analyse the impact of tunable parameters on the radiation budget and hydrological cycle. Furthermore, the subgrid

  13. Venusian Polar Vortex reproduced by a general circulation model

    NASA Astrophysics Data System (ADS)

    Ando, Hiroki; Sugimoto, Norihiko; Takagi, Masahiro

    2016-10-01

    Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the mid-latitudes at cloud-top levels (~65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ~60 degree latitude, which is a unique feature called 'cold collar' in the Venus atmosphere [e.g. Taylor et al. 1980; Piccioni et al. 2007]. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. In addition, an axi-asymmetric feature is always seen in the warm polar vortex. It changes temporally and sometimes shows a hot polar dipole or S-shaped structure as shown by a lot of infrared measurements [e.g. Garate-Lopez et al. 2013; 2015]. However, its vertical structure has not been investigated. To solve these problems, we performed a numerical simulation of the Venus atmospheric circulation using a general circulation model named AFES for Venus [Sugimoto et al. 2014] and reproduced these puzzling features.And then, the reproduced structures of the atmosphere and the axi-asymmetirc feature are compared with some previous observational results.In addition, the quasi-periodical zonal-mean zonal wind fluctuation is also seen in the Venus polar vortex reproduced in our model. This might be able to explain some observational results [e.g. Luz et al. 2007] and implies that the polar vacillation might also occur in the Venus atmosphere, which is silimar to the Earth's polar atmosphere. We will also show some initial results about this point in this presentation.

  14. Comparison of Cenozoic atmospheric general circulation model simulations

    SciTech Connect

    Barron, E.J.

    1985-01-01

    Paleocene, Eocene, Miocene and present day (with polar ice) geography are specified as the lower boundary condition in a mean annual, energy balance ocean version of the Community Climate Model (CCM), a spectral General Circulation Model of the Atmosphere developed at the National Center for Atmospheric Research. This version of the CCM has a 4.5/sup 0/ latitudinal and 7.5/sup 0/ longitudinal resolution with 9 vertical levels and includes predictions for pressure, winds, temperature, evaporation, precipitation, cloud cover, snow cover and sea ice. The model simulations indicate little geographically-induced climates changes from the Paleocene to the Miocene, but substantial differences between the Miocene and the present simulations. The simulated climate differences between the Miocene and present day include: 1) cooler present temperatures (2/sup 0/C in tropics, 15-35 C in polar latitudes) with the exception of warmer subtropical desert conditions, 2) a generally weaker present hydrologic cycle, with greater subtropical aridity, 3) strengthened present day westerly jets with a slight poleward displacement, and 4) the largest regional climate changes associated with Antarctica. The results of the climate model sensitivity experiments have considerable implications for understanding how geography influences climate.

  15. Advanced Modeling of Micromirror Devices

    NASA Technical Reports Server (NTRS)

    Michalicek, M. Adrian; Sene, Darren E.; Bright, Victor M.

    1995-01-01

    The flexure-beam micromirror device (FBMD) is a phase only piston style spatial light modulator demonstrating properties which can be used for phase adaptive corrective optics. This paper presents a complete study of a square FBMD, from advanced model development through final device testing and model verification. The model relates the electrical and mechanical properties of the device by equating the electrostatic force of a parallel-plate capacitor with the counter-acting spring force of the device's support flexures. The capacitor solution is derived via the Schwartz-Christoffel transformation such that the final solution accounts for non-ideal electric fields. The complete model describes the behavior of any piston-style device, given its design geometry and material properties. It includes operational parameters such as drive frequency and temperature, as well as fringing effects, mirror surface deformations, and cross-talk from neighboring devices. The steps taken to develop this model can be applied to other micromirrors, such as the cantilever and torsion-beam designs, to produce an advanced model for any given device. The micromirror devices studied in this paper were commercially fabricated in a surface micromachining process. A microscope-based laser interferometer is used to test the device in which a beam reflected from the device modulates a fixed reference beam. The mirror displacement is determined from the relative phase which generates a continuous set of data for each selected position on the mirror surface. Plots of this data describe the localized deflection as a function of drive voltage.

  16. Advanced Mirror & Modelling Technology Development

    NASA Technical Reports Server (NTRS)

    Effinger, Michael; Stahl, H. Philip; Abplanalp, Laura; Maffett, Steven; Egerman, Robert; Eng, Ron; Arnold, William; Mosier, Gary; Blaurock, Carl

    2014-01-01

    The 2020 Decadal technology survey is starting in 2018. Technology on the shelf at that time will help guide selection to future low risk and low cost missions. The Advanced Mirror Technology Development (AMTD) team has identified development priorities based on science goals and engineering requirements for Ultraviolet Optical near-Infrared (UVOIR) missions in order to contribute to the selection process. One key development identified was lightweight mirror fabrication and testing. A monolithic, stacked, deep core mirror was fused and replicated twice to achieve the desired radius of curvature. It was subsequently successfully polished and tested. A recently awarded second phase to the AMTD project will develop larger mirrors to demonstrate the lateral scaling of the deep core mirror technology. Another key development was rapid modeling for the mirror. One model focused on generating optical and structural model results in minutes instead of months. Many variables could be accounted for regarding the core, face plate and back structure details. A portion of a spacecraft model was also developed. The spacecraft model incorporated direct integration to transform optical path difference to Point Spread Function (PSF) and between PSF to modulation transfer function. The second phase to the project will take the results of the rapid mirror modeler and integrate them into the rapid spacecraft modeler.

  17. Angular momentum conservation in a simplified Venus General Circulation Model

    NASA Astrophysics Data System (ADS)

    Lee, C.; Richardson, M. I.

    2012-11-01

    Angular momentum (AM) conservation and transport are critical components of all General Circulation Model (GCM) simulations, and particularly for simulations of the Venus atmosphere. We show that a Venus GCM based upon the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS) GCM conserves angular momentum to better than 2% per 1000 Venus years (≈225,000 Earth days) of integration under the extreme conditions of a simplified Venus simulation with low surface torques. With no topography in the GCM, physical torques due to surface/atmosphere frictional interactions dominate the acceleration of an initially stationary atmosphere and provide more than four times the angular momentum of solid body co-rotation over an integration period of 100 Venus years. During the subsequent steady state period of 200 Venus years negligible mean physical torques cause variation in the total angular momentum of less than 5% and produce a stable multi-century simulation. Diffusion and damping processes within the GCM account for AM losses of less than 0.2% per 1000 Venus years. This study provides a stable comparison point for other GCMs by employing a simplified forcing scheme. The diagnostics and analysis require little or no modification to the core GCM and are sufficiently robust to allow easy model inter-comparison.

  18. Correcting precipitation feature location in general circulation models

    NASA Astrophysics Data System (ADS)

    Levy, Adam A. L.; Jenkinson, Mark; Ingram, William; Allen, Myles

    2014-12-01

    There is much evidence that precipitation responses to global warming involve wet regions becoming wetter and dry regions drier. This presents challenges for the interpretation of projections from general circulation models (GCMs) which have substantial biases in the location of precipitation features. While improving GCM simulated precipitation is the most desirable solution, adaptation and mitigation decisions must be made with the models already available. Many techniques have been developed to correct biases in grid point precipitation intensities, but few have been introduced to correct for location biases. Here, we describe a new technique for correcting the spatial and seasonal location of climatological precipitation features. We design this technique to respect the geometry of the problem (spherical spatial dimensions, with cyclic seasons), while conserving either precipitation intensities, or integrated precipitation amount. We discuss the mathematical basis of the technique and investigate its behaviour in different regimes. We find that the resulting warps depend smoothly on the most influential parameter, which determines the balance between smoothness and closeness of fit. We show that the technique is capable of removing more than half the RMS error in a model's climatology, obtaining consistently better results when conserving integrated precipitation. To demonstrate the ability of the new technique to improve simulated precipitation changes, we apply our transformations to historical anomalies and show that RMS error is reduced relative to GPCP's anomalies by approximately 10% for both types of warp. This verifies that errors in precipitation changes can be reduced by correcting underlying location errors in a GCM's climatology.

  19. The response of an ocean general circulation model to surface wind stress produced by an atmospheric general circulation model

    SciTech Connect

    Huang, B.; Schneider, E.K.

    1995-10-01

    Two surface wind stress datasets for 1979-91, one based on observations and the other from an investigation of the COLA atmospheric general circulation model (AGCM) with prescribed SST, are used to drive the GFDL ocean general circulation model. These two runs are referred to as the control and COLA experiments, respectively. Simulated SST and upper-ocean heat contents (HC) in the tropical Pacific Ocean are compared with observations and between experiments. Both simulation reproduced the observed mean SST and HC fields as well as their annual cycles realistically. Major errors common to both runs are colder than observed SST in the eastern equatorial ocean and HC in the western Pacific south of the equator, with errors generally larger in the COLA experiment. New errors arising from the AGCM wind forcing include higher SST near the South American coast throughout the year and weaker HC gradients along the equator in boreal spring. The former is associated with suppressed coastal upwelling by weak along shore AGCM winds, and the latter is caused by weaker equatorial easterlies in boreal spring. The low-frequency ENSO fluctuations are also realistic for both runs. Correlations between the observed and simulated SST anomalies from the COLA simulation are as high as those from the control run in the central equatorial Pacific. A major problem in the COLA simulation is the appearance of unrealistic tropical cold anomalies during the boreal spring of mature El Nino years. These anomalies propagate along the equator from the western Pacific to the eastern coast in about three months, and temporarily eliminate the warm SST and HC anomalies in the eastern Pacific. This erroneous oceanic response in the COLA simulation is caused by a reversal of the westerly wind anomalies on the equator, associated with an unrealistic southward shift of the ITCZ in boreal spring during El Nino events. 66 refs., 16 figs.

  20. Modeling Tool Advances Rotorcraft Design

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Continuum Dynamics Inc. (CDI), founded in 1979, specializes in advanced engineering services, including fluid dynamic modeling and analysis for aeronautics research. The company has completed a number of SBIR research projects with NASA, including early rotorcraft work done through Langley Research Center, but more recently, out of Ames Research Center. NASA Small Business Innovation Research (SBIR) grants on helicopter wake modeling resulted in the Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM), a tool for studying helicopter and tiltrotor unsteady free wake modeling, including distributed and integrated loads, and performance prediction. Application of the software code in a blade redesign program for Carson Helicopters, of Perkasie, Pennsylvania, increased the payload and cruise speeds of its S-61 helicopter. Follow-on development resulted in a $24 million revenue increase for Sikorsky Aircraft Corporation, of Stratford, Connecticut, as part of the company's rotor design efforts. Now under continuous development for more than 25 years, CHARM models the complete aerodynamics and dynamics of rotorcraft in general flight conditions. CHARM has been used to model a broad spectrum of rotorcraft attributes, including performance, blade loading, blade-vortex interaction noise, air flow fields, and hub loads. The highly accurate software is currently in use by all major rotorcraft manufacturers, NASA, the U.S. Army, and the U.S. Navy.

  1. Arctic Storms in a Regionally Refined Atmospheric General Circulation Model

    NASA Astrophysics Data System (ADS)

    Roesler, E. L.; Taylor, M.; Boslough, M.; Sullivan, S.

    2014-12-01

    Regional refinement in an atmospheric general circulation model is a new tool in atmospheric modeling. A regional high-resolution solution can be obtained without the computational cost of running a global high-resolution simulation as global climate models have increasing ability to resolve smaller spatial scales. Previous work has shown high-resolution simulations, i.e. 1/8 degree, and variable resolution utilities have resolved more fine-scale structure and mesoscale storms in the atmosphere than their low-resolution counterparts. We will describe an experiment designed to identify and study Arctic storms at two model resolutions. We used the Community Atmosphere Model, version 5, with the Spectral Element dynamical core at 1/8-degree and 1 degree horizontal resolutions to simulate the climatological year of 1850. Storms were detected using a low-pressure minima and vorticity maxima - finding algorithm. It was found the high-resolution 1/8-degree simulation had more storms in the Northern Hemisphere than the low-resolution 1-degree simulation. A variable resolution simulation with a global low resolution of 1-degree and a high-resolution refined region of 1/8 degree over a region in the Arctic is planned. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND NO. 2014-16460A

  2. Correlations between the modelled potato crop yield and the general atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Sepp, Mait; Saue, Triin

    2012-07-01

    Biology-related indicators do not usually depend on just one meteorological element but on a combination of several weather indicators. One way to establish such integral indicators is to classify the general atmospheric circulation into a small number of circulation types. The aim of present study is to analyse connections between general atmospheric circulation and potato crop yield in Estonia. Meteorologically possible yield (MPY), calculated by the model POMOD, is used to characterise potato crop yield. Data of three meteorological stations and the biological parameters of two potato sorts were applied to the model, and 73 different classifications of atmospheric circulation from catalogue 1.2 of COST 733, domain 05 are used to qualify circulation conditions. Correlation analysis showed that there is at least one circulation type in each of the classifications with at least one statistically significant (99%) correlation with potato crop yield, whether in Kuressaare, Tallinn or Tartu. However, no classifications with circulation types correlating with MPY in all three stations at the same time were revealed. Circulation types inducing a decrease in the potato crop yield are more clearly represented. Clear differences occurred between the observed geographical locations as well as between the seasons: derived from the number of significant circulation types, summer and Kuressaare stand out. Of potato varieties, late 'Anti' is more influenced by circulation. Analysis of MSLP maps of circulation types revealed that the seaside stations (Tallinn, Kuressaare) suffer from negative effects of anti-cyclonic conditions (drought), while Tartu suffers from the cyclonic activity (excessive water).

  3. Limited genomic heterogeneity of circulating melanoma cells in advanced stage patients

    NASA Astrophysics Data System (ADS)

    Ruiz, Carmen; Li, Julia; Luttgen, Madelyn S.; Kolatkar, Anand; Kendall, Jude T.; Flores, Edna; Topp, Zheng; Samlowski, Wolfram E.; McClay, Edward; Bethel, Kelly; Ferrone, Soldano; Hicks, James; Kuhn, Peter

    2015-02-01

    Purpose. Circulating melanoma cells (CMCs) constitute a potentially important representation of time-resolved tumor biology in patients. To date, genomic characterization of CMCs has been limited due to the lack of a robust methodology capable of identifying them in a format suitable for downstream characterization. Here, we have developed a methodology to detect intact CMCs that enables phenotypic, morphometric and genomic analysis at the single cell level. Experimental design. Blood samples from 40 metastatic melanoma patients and 10 normal blood donors were prospectively collected. A panel of 7 chondroitin sulfate proteoglycan 4 (CSPG4)-specific monoclonal antibodies (mAbs) was used to immunocytochemically label CMCs. Detection was performed by automated digital fluorescence microscopy and multi-parametric computational analysis. Individual CMCs were captured by micromanipulation for whole genome amplification and copy number variation (CNV) analysis. Results. Based on CSPG4 expression and nuclear size, 1-250 CMCs were detected in 22 (55%) of 40 metastatic melanoma patients (0.5-371.5 CMCs ml-1). Morphometric analysis revealed that CMCs have a broad spectrum of morphologies and sizes but exhibit a relatively homogeneous nuclear size that was on average 1.5-fold larger than that of surrounding PBMCs. CNV analysis of single CMCs identified deletions of CDKN2A and PTEN, and amplification(s) of TERT, BRAF, KRAS and MDM2. Furthermore, novel chromosomal amplifications in chr12, 17 and 19 were also found. Conclusions. Our findings show that CSPG4 expressing CMCs can be found in the majority of advanced melanoma patients. High content analysis of this cell population may contribute to the design of effective personalized therapies in patients with melanoma.

  4. Limited Genomic Heterogeneity of Circulating Melanoma Cells in Advanced Stage Patients

    PubMed Central

    Ruiz, Carmen; Li, Julia; Luttgen, Madelyn S.; Kolatkar, Anand; Kendall, Jude T.; Flores, Edna; Topp, Zheng; Samlowski, Wolfram E.; McClay, Ed; Bethel, Kelly; Ferrone, Soldano; Hicks, James; Kuhn, Peter

    2015-01-01

    Purpose Circulating melanoma cells (CMCs) constitute a potentially important representation of time-resolved tumor biology in patients. To date, genomic characterization of CMCs has been limited due to the lack of a robust methodology capable of identifying them in a format suitable for downstream characterization. Here, we have developed a methodology to detect intact CMCs that enables phenotypic, morphometric and genomic analysis at the single cell level. Experimental design Blood samples from 40 metastatic melanoma patients and 10 normal blood donors (NBD) were prospectively collected. A panel of 7 chondroitin sulfate proteoglycan 4 (CSPG4)-specific monoclonal antibodies (mAb) was used to immunocytochemically label CMCs. Detection was performed by automated digital fluorescence microscopy and multi-parametric computational analysis. Individual CMCs were captured by micromanipulation for whole genome amplification (WGA) and copy number variation (CNV) analysis. Results Based on CSPG4 expression and nuclear size, 1 to 250 CMCs were detected in 22 (55%) of 40 metastatic melanoma patients (0.5 to 371.5 CMCs/ml). Morphometric analysis revealed that CMCs have a broad spectrum of morphologies and sizes but exhibit a relatively homogeneous nuclear size that was on average 1.5-fold larger than that of surrounding PBMCs. CNV analysis of single CMCs identified deletions of CDKN2A and PTEN, and amplification(s) of TERT, BRAF, KRAS and MDM2. Furthermore, novel chromosomal amplifications in chr12, 17 and 19 were also found. Conclusions Our findings show that CSPG4 expressing CMCs can be found in the majority of advanced melanoma patients. High content analysis of this population may contribute to develop effective therapeutic strategies. PMID:25574741

  5. Hospitable archean climates simulated by a general circulation model.

    PubMed

    Wolf, E T; Toon, O B

    2013-07-01

    Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model.

  6. Modelling mixing and circulation in subglacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Thoma, Malte; Grosfeld, Klaus; Mayer, Christoph

    2007-12-01

    Lake Vostok, isolated from direct exchange with the atmosphere by about 4 km of ice for millions of years, provides a unique environment. This inaccessibility raises the importance of numerical models to investigate the physical conditions within the lake. Using a three-dimensional numerical model and the best available geometry, we test different parameter settings to define a standard model configuration suitable for studying flow in this subglacial lake. From our model runs we find a baroclinic circulation within the lake that splits into three different parts: Along a topographic ridge in the northern part of Lake Vostok, bottom water masses are transported eastward, diverging away from the ridge. In the lake’s surface layer, the flow in these two vertical overturning cells has opposite directions. In the southern part of the lake, where freezing occurs across about 3,500 km2, two opposing gyres split the water column vertically. The general flow is stronger in the southern basin with horizontal velocities in the order of 1 mm/s. The strongest upwelling, found in the eastern part of this basin, is about 25 μm/s. We estimate the lower limit of the overturning timescale to be about 2.5 years vertically and 8.6 years horizontally. The basal mass loss of ice from the ice sheet floating on the lake is 5.6 mm/year (equivalent to a fresh water flux of 2.78 m3/s, or a basal ice loss of 0.09 km3/year). This imbalance indicates either a constant growth of the lake or its continuous (or periodical) discharge into a subglacial drainage system.

  7. Hospitable archean climates simulated by a general circulation model.

    PubMed

    Wolf, E T; Toon, O B

    2013-07-01

    Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model. PMID:23808659

  8. Numerical Modelling of Circulation and Exchange through Singapore Straits

    NASA Astrophysics Data System (ADS)

    Liu, G.; Xu, M.; Chua, V. P.

    2014-12-01

    The circulation in the Singapore coastal region is complicated and influenced by the combination of tidal forcing of the surrounding seas, complex bathymetry, irregular coastlines, and seasonal monsoon and local winds. An unstructured-grid SUNTANS (Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator) model is employed to perform three-dimensional simulations of flow in Singapore coastal waters. The unstructured-grid has an average resolution of 50 - 100 m around Singapore and in areas close to the shoreline, while a coarse grid resolution is employed in the open waters. The model is tidally forced at the three open boundaries, located to the west, south and east of Singapore, using the 8 main tidal constituents as derived from the OSU Tidal Prediction Software (OTPS). A detailed calibration is performed, and the model-predicted water levels and currents compare well with observed data throughout the model domain. We examine the individual and combined effects of tidal and wind forcing by performing simulations with (1) tides only, (2) winds only and (3) both tides and wind. The exchange through Singapore Strait is investigated by computing volume fluxes and transport pathways at four transects, namely the Malacca Strait, Java Sea, South China Sea and Singapore transects. The transport pathways are computed by releasing particles on each side of the transects, and identifying the spatial distribution of the particles over one tidal cycle. Our results show that tidal forcing is predominant in Singapore Strait, and wind forcing is an important mechanism during the monsoon season. The residual effects, attributed to nonlinear interactions between tidal and wind forcing, is dominant during the inter-monsoon season.

  9. Late Early Silurian (Wenlockian) paleoclimate using a general circulation model

    SciTech Connect

    Moore, G.T.; Hayashida, D.N.; Jacobson, S.R. ) Ross, C.A. )

    1992-01-01

    The Silurian Period (439--409 Ma) is synonymous with organic-rich, graptolitic, black shales. The physical conditions that prevailed during the Mid-Silurian drove the paleoclimate and controlled the deposition of this globally ubiquitous, lithotope. The paleoclimate in turn concomitantly created a paleoceanic environment favorable for the generation, deposition, and preservation of phytoplankton. A study of the relationship of the paleogeographic framework on the paleoclimate conditions that forced the deposition of this unique rock type is a problem suitable for study with a general circulation model. For this study the authors chose the Wenlockian Stage (430--424 Ma), the late Early Silurian. The Wenlockian physical world was composed of an oceanic northern hemisphere and a southern hemisphere dominated by the giant continent of Gondwana. The high latitude position of Gondwana placed much of its extensive margin in the mid-latitudes. Laurentia and Baltica occupied a tropical position while Siberia and Kazakh laid to the north. The Silurian fits a paleoatmosphere with an elevated greenhouse effect. Estimated Silurian values of atmospheric CO[sub 2] vary. They chose 1,120 ppm CO[sub 2], a value of 4[times] that of the pre-industrial level. The overall paleoclimate is forced by the diverse paleogeography of the two hemispheres. The northern hemisphere is dominated by strong zonality in all seasons. In contrast, the continental southern hemisphere reactors to the summer heating and winter cooling of Gondwana.

  10. Barotropic-Baroclinic Time Splitting for Ocean Circulation Modeling

    NASA Astrophysics Data System (ADS)

    Higdon, Robert L.; de Szoeke, Roland A.

    1997-07-01

    Numerical models of ocean circulation admit motions varying on a wide range of time scales. These motions include fast external gravity waves, which are approximately independent of depth, and slower internal motions which are fully three-dimensional. Explicit time discretizations are impractical for these systems, due to the short timesteps dictated by the fast waves. A commonly used alternative is to confine the fast waves to a two-dimensional system, via vertical averaging, and then to compute the remaining motions explicitly with a long time step. However, this procedure can lead to numerical instability if the latter system admits sufficiently large residual fast motions due to an inexact splitting. In this paper we modify a method developed by R. Bleck and L. T. Smith ( J. Geophys. Res. C95,3273, 1990) in order to obtain a more precise splitting into fast and slow subsystems. In the vertically averaged momentum equation, we use the exact vertical average of the horizontal pressure gradient in place of the approximation used in op cit.We then apply natural time discretizations and show that the modified splitting produces considerable improvements in stability.

  11. Solar terminator wave in a Mars general circulation model

    NASA Astrophysics Data System (ADS)

    Forbes, J. M.; Moudden, Y.

    2009-09-01

    A solar terminator wave (TW) is found in high-resolution general circulation model (GCM) simulations of Mars' atmosphere. In the horizontal plane at 160 km the wave fronts follow the westward-moving dusk terminator, exhibit a horizontal wavelength of order 1800-3600 km, and are oriented about 10°-30° with respect to the terminator. The disturbance originates in the lower atmosphere due to dust absorption of solar radiation, propagates upward with an effective vertical wavelength of order 60 km, and increases in amplitude as the assumed dust distribution extends further away from the surface. The TW density amplitudes for low and elevated dust layers (both with opacities = 1.0) are of order ±15-20% and ±30% at 160 km. Temperature and wind perturbations for the former case are of order ±10-20K and ±30-75 m/s. The Mars TW shares many common features with a TW recently observed in Earth's thermosphere and simulated with a terrestrial GCM.

  12. Multivariate autoregressive modelling combined with transcephalic electrical impedance: method to relate neonatal systemic circulation and respiration to cerebral circulation.

    PubMed

    Grönlund, J U; Jalonen, J; Korhonen, I; Rolfe, P; Välimäki, I A

    1995-05-01

    We studied the pulsatile component of cerebral circulation with transcephalic electrical impedance (delta Z) in six preterm newborns, three of whom had severe cerebral bleeding, peri-intraventricular haemorrhage (PIVH). The transcephalic electrical impedance delta Z signal, ECG, arterial blood pressure, (aBP) and respirogram were recorded on analogue magnetic tape for 30 min. Artefact-free stationary segments (lasting for 2 min) of the four signals were digitised. A digital multivariate autoregressive (MAR) model was used to study frequency-specific variability in the signals and to quantify interrelations between the variabilities of delta Z, HR, aBP and respiratory signals. MAR modelling describes a system where all the signals simultaneously explain each other. The inherent variability of delta Z was lower and the influences of respiration and aBP on delta Z significantly greater in infants with severe PIVH than in controls. These changes were observed at high frequencies corresponding to respiration and heart rate. This may be interpreted as a marker of pressure passivism in the cerebral circulation following PIVH. We conclude that in preterm babies the application of MAR modelling, together with transcephalic impedance, may be a new, helpful and quantitative method for the study of simultaneous interrelations between variables of cerebral and systemic circulations and respiration.

  13. Modeling mantle circulation and density distributions in subduction zones: Implications for seismic studies

    NASA Astrophysics Data System (ADS)

    Kincaid, C. R.; Druken, K. A.; Griffiths, R. W.; Long, M. D.; Behn, M. D.; Hirth, G.

    2009-12-01

    Subduction of ocean lithosphere drives plate tectonics, large-scale mantle circulation and thermal-chemical recycling processes through arcs. Seismologists have made important advances in our ability to map circulation patterns in subduction zones though anisotropy data/methods and in providing detailed images of mantle density fields. Increasingly, seismic and geodynamic disciplines are combining to extend our understanding of time varying subduction processes and associated vertical mass and energy fluxes. We use laboratory experiments to characterize three-dimensional flow fields in convergent margins for a range in plate forcing conditions and background, buoyancy-driven flow scenarios. Results reveal basic patterns in circulation, buoyant flow morphologies and density distributions that have implications for reconciling seismic data with mantle convection models. Models utilize a glucose working fluid with a temperature dependent viscosity to represent the upper 2000km of the mantle. Subducting lithosphere is modeled with a Phenolic plate and back-arc extension is produced using Mylar sheets. We recreate basic subduction styles observed in previous dynamic subduction models using simplified, kinematic forcing. Slab plate segments, driven by hydraulic pistons, move with various combinations of downdip, rollback and steepening motion. Neutral density finite strain markers are distributed throughout the fluid and used as proxies for tracking the evolution of olivine alignment through space and time in the evolving flow fields. Particle image velocimetry methods are also used to track time varying 3D velocity fields for use in directly calculating anisotropy patterns. Results show that complex plate motions (rollback, steepening, back-arc extension) in convergent margins produce relatively simple anisotropy patterns (e.g., trench-normal alignments) and underscore the importance of initial strain marker orientations on alignment patterns in the wedge. Results also

  14. Serum cytokines are increased and circulating micronutrients are not altered in subjects with early compared to advanced knee osteoarthritis.

    PubMed

    Barker, Tyler; Rogers, Victoria E; Henriksen, Vanessa T; Aguirre, Dale; Trawick, Roy H; Rasmussen, G Lynn; Momberger, Nathan G

    2014-08-01

    Knee osteoarthritis (OA) is a leading cause of physical disability. At the early stage of knee OA, the increase in synovial fluid cytokine concentrations could contribute to the pathogenesis of OA by degrading articular cartilage. It is unknown, however, if inflammatory cytokines increase systemically at the early or advanced stage of knee OA. The systemic increase of inflammatory cytokines could be detrimental to the endogenous status of micronutrients that protect against excessive inflammation and cytokine-mediated events. The purpose of this study was to test the hypothesis that an increase in serum cytokines associate with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA. Advanced knee OA subjects (n=14) displayed radiographic, pain, and muscular weakness symptoms of knee OA. Early knee OA subjects (n=14) were matched (age, gender, and body mass index) to the advanced OA group and displayed one or two of the aforementioned symptoms of knee OA. Inflammatory cytokines, vitamins C (ascorbic acid), D (25-hydroxyvitamin D), and E (α- and γ-tocopherols), and β-carotene were measured in fasting blood samples. In the early OA group, serum tumor necrosis factor (TNF)-α, interleukin (IL)-5, IL-6, IL-12, and IL-13 concentrations were significantly (all p<0.05) increased. Circulating ascorbic acid, 25-hydroxyvitamin D, α- and γ-tocopherol's, and β-carotene concentrations were not significantly different between groups. Based on these preliminary results, we conclude that the systemic increase of inflammatory cytokines is not associated with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA.

  15. Adaptive Error Estimation in Linearized Ocean General Circulation Models

    NASA Technical Reports Server (NTRS)

    Chechelnitsky, Michael Y.

    1999-01-01

    Data assimilation methods are routinely used in oceanography. The statistics of the model and measurement errors need to be specified a priori. This study addresses the problem of estimating model and measurement error statistics from observations. We start by testing innovation based methods of adaptive error estimation with low-dimensional models in the North Pacific (5-60 deg N, 132-252 deg E) to TOPEX/POSEIDON (TIP) sea level anomaly data, acoustic tomography data from the ATOC project, and the MIT General Circulation Model (GCM). A reduced state linear model that describes large scale internal (baroclinic) error dynamics is used. The methods are shown to be sensitive to the initial guess for the error statistics and the type of observations. A new off-line approach is developed, the covariance matching approach (CMA), where covariance matrices of model-data residuals are "matched" to their theoretical expectations using familiar least squares methods. This method uses observations directly instead of the innovations sequence and is shown to be related to the MT method and the method of Fu et al. (1993). Twin experiments using the same linearized MIT GCM suggest that altimetric data are ill-suited to the estimation of internal GCM errors, but that such estimates can in theory be obtained using acoustic data. The CMA is then applied to T/P sea level anomaly data and a linearization of a global GFDL GCM which uses two vertical modes. We show that the CMA method can be used with a global model and a global data set, and that the estimates of the error statistics are robust. We show that the fraction of the GCM-T/P residual variance explained by the model error is larger than that derived in Fukumori et al.(1999) with the method of Fu et al.(1993). Most of the model error is explained by the barotropic mode. However, we find that impact of the change in the error statistics on the data assimilation estimates is very small. This is explained by the large

  16. Structure and predictability of the El Nino/Southern Oscillation phenomenon in a coupled ocean-atmosphere general circulation model

    SciTech Connect

    Latif, M.; Sterl, A.; Maier-Reimer, E.; Junge, M.M. )

    1993-04-01

    The space-time structure and predictability of the El Nino/Southern Oscillation (ENSO) phenomenon was investigated. Two comprehensive datasets were analyzed by means of an advanced statistical method, one based on observational data and other on data derived from an extended-range integration performed with a coupled ocean atmosphere general circulation model. It is shown that a considerable portion of the ENSO related low-frequency climate variability in both datasets is associated with a cycle implies the possibility of climate predictions in the tropics up to lead times of about one year. This is shown by conducting an ensemble of predictions with our coupled general circulation model. For the first time a coupled model of this type was successfully applied to ENSO predictions. 34 refs., 6 figs.

  17. Documentation of the GLAS fourth order general circulation model. Volume 1: Model documentation

    NASA Technical Reports Server (NTRS)

    Kalnay, E.; Balgovind, R.; Chao, W.; Edelmann, J.; Pfaendtner, J.; Takacs, L.; Takano, K.

    1983-01-01

    The volume 1, of a 3 volume technical memoranda which contains a documentation of the GLAS Fourth Order General Circulation Model is presented. Volume 1 contains the documentation, description of the stratospheric/tropospheric extension, user's guide, climatological boundary data, and some climate simulation studies.

  18. Preliminary regime diagram on a sphere with a simplified general circulation model

    NASA Technical Reports Server (NTRS)

    Pitcher, E. J.; Geisler, J. E.; Malone, R. C.

    1981-01-01

    Numerical model studies useful design considerations and which can be accumulated to form the body of basic knowledge necessary for application of the atmospheric general circulation experiment (AGCE) data to understanding of atmospheric problems are reported. The most efficient way to obtain a computer model suitable for this objective is to modify an existing general circulation model (GCM) of the atmosphere rather than to develop such a model from first principles. The GCM and its modification is outlined.

  19. Numerical modelling of geothermal and reflux circulation in Enewetak Atoll: Implications for dolomitization

    USGS Publications Warehouse

    Jones, G.; Whitaker, F.; Smart, P.; Sanford, W.

    2000-01-01

    Two types of regional-scale seawater circulation have been proposed to explain the formation of Enewetak Atoll dolomites: geothermal and reflux circulation. We have used a finite element groundwater flow model to examine the pattern, magnitude and dynamic interaction of these two different circulation mechanisms in Enewetak Atoll. Geothermal circulation is concentrated around the atoll-margin whereas refluxing mesosaline brines flow from the atoll interior towards the margin to restrict and eventually shut off geothermal circulation. Refluxing brines of 36-80??? can account for the salinity signature recorded in dolomite fluid inclusions. Distributions of fluid flux and Mg mass-balance calculations suggest that both geothermal and reflux circulation mechanisms could account for the observed distribution of dolomite in Enewetak Atoll. Furthermore, the atoll interior may be extensively dolomitized as observed in other atolls. (C) 2000 Elsevier Science B.V. All rights reserved.Two types of regional-scale seawater circulation have been proposed to explain the formation of Enewetak Atoll dolomites: geothermal and reflux circulation. We have used a finite element groundwater flow model to examine the pattern, magnitude and dynamic interaction of these two different circulation mechanisms in Enewetak Atoll. Geothermal circulation is concentrated around the atoll-margin whereas refluxing mesosaline brines flow from the atoll interior towards the margin to restrict and eventually shut off geothermal circulation. Refluxing brines of 36-80 per mil can account for the salinity signature recorded in dolomite fluid inclusions. Distributions of fluid flux and Mg mass-balance calculations suggest that both geothermal and reflux circulation mechanisms could account for the observed distribution of dolomite in Enewetak Atoll. Furthermore, the atoll interior may be extensively dolomitized as observed in other atolls.

  20. A simple biosphere model (SiB) for use within general circulation models

    NASA Technical Reports Server (NTRS)

    Sellers, P. J.; Mintz, Y.; Sud, Y. C.; Dalcher, A.

    1986-01-01

    A simple realistic biosphere model for calculating the transfer of energy, mass and momentum between the atmosphere and the vegetated surface of the earth has been developed for use in atmospheric general circulation models. The vegetation in each terrestrial model grid is represented by an upper level, representing the perennial canopy of trees and shrubs, and a lower level, representing the annual cover of grasses and other heraceous species. The vegetation morphology and the physical and physiological properties of the vegetation layers determine such properties as: the reflection, transmission, absorption and emission of direct and diffuse radiation; the infiltration, drainage, and storage of the residual rainfall in the soil; and the control over the stomatal functioning. The model, with prescribed vegetation parameters and soil interactive soil moisture, can be used for prediction of the atmospheric circulation and precipitaion fields for short periods of up to a few weeks.

  1. Advances in Watershed Models and Modeling

    NASA Astrophysics Data System (ADS)

    Yeh, G. T.; Zhang, F.

    2015-12-01

    The development of watershed models and their applications to real-world problems has evolved significantly since 1960's. Watershed models can be classified based on what media are included, what processes are dealt with, and what approaches are taken. In term of media, a watershed may include segregated overland regime, river-canal-open channel networks, ponds-reservoirs-small lakes, and subsurface media. It may also include integrated media of all these or a partial set of these as well as man-made control structures. In term of processes, a watershed model may deal with coupled or decoupled hydrological and biogeochemical cycles. These processes include fluid flow, thermal transport, salinity transport, sediment transport, reactive transport, and biota and microbe kinetics. In terms of approaches, either parametric or physics-based approach can be taken. This talk discusses the evolution of watershed models in the past sixty years. The advances of watershed models center around their increasing design capability to foster these segregated or integrated media and coupled or decoupled processes. Widely used models developed by academia, research institutes, government agencies, and private industries will be reviewed in terms of the media and processes included as well as approaches taken. Many types of potential benchmark problems in general can be proposed and will be discussed. This presentation will focus on three benchmark problems of biogeochemical cycles. These three problems, dealing with water quality transport, will be formulated in terms of reactive transport. Simulation results will be illustrated using WASH123D, a watershed model developed and continuously updated by the author and his PhD graduates. Keywords: Hydrological Cycles, Biogeochemical Cycles, Biota Kinetics, Parametric Approach, Physics-based Approach, Reactive Transport.

  2. Demand Models for Books in Library Circulation Systems. Final Report.

    ERIC Educational Resources Information Center

    Lazorick, Gerald J.

    This research is a study of demands for books in library circulation systems. Demand data for random samples of books were collected and fitted to various standard distributions. The numbers of demands for collections of books are shown to be Negative Binomially distributed. As is shown, this implies that the numbers of demands for individual…

  3. Mesozoic climates: General circulation models and the rock record

    NASA Astrophysics Data System (ADS)

    Sellwood, Bruce W.; Valdes, Paul J.

    2006-08-01

    General circulation models (GCMs) use the laws of physics and an understanding of past geography to simulate climatic responses. They are objective in character. However, they tend to require powerful computers to handle vast numbers of calculations. Nevertheless, it is now possible to compare results from different GCMs for a range of times and over a wide range of parameterisations for the past, present and future (e.g. in terms of predictions of surface air temperature, surface moisture, precipitation, etc.). GCMs are currently producing simulated climate predictions for the Mesozoic, which compare favourably with the distributions of climatically sensitive facies (e.g. coals, evaporites and palaeosols). They can be used effectively in the prediction of oceanic upwelling sites and the distribution of petroleum source rocks and phosphorites. Models also produce evaluations of other parameters that do not leave a geological record (e.g. cloud cover, snow cover) and equivocal phenomena such as storminess. Parameterisation of sub-grid scale processes is the main weakness in GCMs (e.g. land surfaces, convection, cloud behaviour) and model output for continental interiors is still too cold in winter by comparison with palaeontological data. The sedimentary and palaeontological record provides an important way that GCMs may themselves be evaluated and this is important because the same GCMs are being used currently to predict possible changes in future climate. The Mesozoic Earth was, by comparison with the present, an alien world, as we illustrate here by reference to late Triassic, late Jurassic and late Cretaceous simulations. Dense forests grew close to both poles but experienced months-long daylight in warm summers and months-long darkness in cold snowy winters. Ocean depths were warm (8 °C or more to the ocean floor) and reefs, with corals, grew 10° of latitude further north and south than at the present time. The whole Earth was warmer than now by 6 °C or

  4. Hierarchical framework for coupling a biogeochemical trace gas model to a general circulation model

    SciTech Connect

    Miller, N.L.; Foster, I.T.

    1994-04-01

    A scheme is described for the computation of terrestrial biogeochemical trace gas fluxes in the context of a general circulation model. This hierarchical system flux scheme (HSFS) incorporates five major components: (1) a general circulation model (GCM), which provides a medium-resolution (i.e., 1{degrees} by 1{degrees}) simulation of the atmospheric circulation; (2) a procedure for identifying regions of defined homogeneity of surface type within GCM grid cells; (3) a set of surface process models, to be run within each homogeneous region, which include a biophysical model, the Biosphere Atmospheric Transfer Scheme (BATS), and a biogeochemical model (BGCM); (4) an interpolation/integration system that transfers information between the GCM and surface process models with finer resolution; and (5) an interactive data array based on a geographic information system (GIS), which provides land characteristic information via the interpolator. The goals of this detailed investigation are to compute the local and global sensitivities of trace gas fluxes to GCM and BATS variables, the effects of trace gas fluxes on global climate, and the effects of global climate on specific biomes.

  5. Venusian Polar Vortex reproduced in an Atmospheric General Circulation Model

    NASA Astrophysics Data System (ADS)

    Ando, Hiroki; Imamura, Takeshi; Takagi, Masahiro; Sugimoto, Norihiko; Kashimura, Hiroki

    The Venus atmosphere has a polar vortex rotating in the retrograde direction with a period of about three days. The vortex has a warm feature surrounded by a cold collar (e.g., Taylor et al. 1980; Piccioni et al. 2006). Although the Venusian polar vortex has been reported by many observations, its mechanism is still unknown. Elson (1982, 1989) examined the structure of the polar vortex by linear calculations. However, the background zonal wind assumed in the calculations was much stronger or weaker than those retrieved in the previous measurements (e.g., Peralta et al. 2008; Kouyama et al. 2012). Lee et al. (2010) and Yamamoto and Takahashi (2012) performed numerical simulations with general circulation models (GCMs) of the Venus atmosphere and obtained vertical structure in the polar region. However, the models included artificial forcing of Kelvin and/or Rossby waves. We have developed a new Venusian GCM by modifying the Atmospheric GCM For the Earth Simulator (Sugimoto et al. 2012; 2013). The basic equations of the GCM are primitive ones in the sigma coordinate on a sphere without topography. The model resolution is T42 (i.e., about 2.8 deg x 2.8 deg grids) and L60 (Deltaz is about 2 km). Rayleigh friction (sponge layer) in the upper layer (>80 km) is applied to prevent the reflection of waves, whose effect increases gradually with height. In the model, the atmosphere is dry and forced by the solar heating and Newtonian cooling. The vertical profile of the solar heating is based on Crisp (1986), and zonally averaged distribution is used. In addition diurnal component of the solar heating, which excites the diurnal and semi-diurnal tides, is also included. Newtonian cooling relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers, and its coefficient is based on Crisp (1986). To prevent numerical instability, the biharmonic hyper-diffusion is included with 0.8 days of e-folding time

  6. Using Advanced Data Assimilation For Assessing The Capabilities And Limits Of Using The GOCE Geoid To Improve The Shelf And Coastal Ocean Low-Frequency Circulations

    NASA Astrophysics Data System (ADS)

    Julien, L.; Pierre J., D.; Guilhem, M.; Georges, B.; Matthieu, L.; Muriel, L.; Roger, H.; Catherine, B.

    2008-12-01

    Realistic ocean modelling is part of the new challenges that has arisen in the past decade in order to access precise and accurate knowledge of the ocean circulation, especially at regional and coastal scales. An efficient ocean modelling system is now built both on both a hydrodynamic model and a data assimilation technique. Altimetric data plays a central role because of their relative abundance, coverage and repetitive sampling. At the large scales, using a geostrophic balance equation, the upper-layer ocean circulation could be approximately retrieved from the ocean surface topography, assuming that the ocean surface reference level, given by the geoid, is known with sufficient accuracy. However the geoid solutions do not contain the smaller scales characterizing coastal dynamics. More generally, the lack of control over the permanent circulations is a serious limitation for the regional ocean modelling and forecasting. The need for better ocean geoids has then been identified for a long time, and the recent gravimetric satellite missions are a first step to solve the problem. The GOCE satellite, developed at ESA and scheduled for lift- off in September 2008, will operate between two and two and a half years. Its main objective is to further improve our knowledge of the geopotential in providing a higher resolution static model for a variety of applications, especially in oceanography. The scientific community expects that the improved geoid model from GOCE will significantly advance our skill at modelling the mean ocean circulation, by using (1) precise geocentric sea surface elevations obtained from global altimetric measurements, (2) a mean geoid model with an accuracy of the order of one centimeter on spatial scales down to the width of boundary currents, (3) additional oceanographic data sets required to constrain ocean circulation models with data assimilation. The study presented here aims to assess the capabilities and the limits of the use of the GOCE

  7. Numerical modeling of intrinsically and extrinsically forced seasonal circulation in the China Seas: A kinematic study

    NASA Astrophysics Data System (ADS)

    Gan, Jianping; Liu, Zhiqiang; Liang, Linlin

    2016-07-01

    We developed a new three-dimensional, high-resolution ocean circulation model for the entire China Seas (CS) region. The model considered the linked physics associated with the western boundary current, monsoonal wind, and tidal forcings, and topography in both the CS and the adjacent oceans. From this well-validated model, we derived new insights into the three-dimensional seasonal circulation of the CS in response to the intrinsic forcing of monsoonal winds and extrinsic forcing of flow exchange with adjacent oceans through the straits and over the slope around the periphery of the CS. Besides the East Asian monsoon forcing, we found that the extrinsic forcings interact coherently with each other and with the interior circulation to jointly shape the CS circulation. Specifically, we revealed rotating layered circulation in the CS. The circulation in the South China Sea has a vertical cyclonic-anticyclonic-cyclonic pattern in the upper-middle-lower layers, which we relate to the inflow-outflow-inflow transport in those layers in the Luzon Strait. The circulation in the East China Sea (ECS) is characterized by a vertically variable cyclonically rotating flow, and the circulation in the Yellow Sea (YS) is represented by a cyclonic movement in the upper layer and an anticyclonic movement in the lower layer. We attribute the cross-shelf variation of the along-shelf current to the ECS circulation pattern, while the vertically variable intrusive current at the central trough, together with the seasonally varied west and east coastal currents, shape the two-layer circulation in the YS.

  8. Numerical modelling of the circulation of superrotating atmospheres: Venus and Titan

    NASA Technical Reports Server (NTRS)

    Hourding, F.; Talagrand, O.; Menou, K.; Fournier, R.; Dufresnes, J.-L.; Gautier, D.; Courtin, R.; Bezard, B.; McKay, C. P.

    1996-01-01

    Atmospheric superrotation is known to exist on Venus where the cloud cover, at 70 km above the surface, rotates about 60 times faster than the solid planet. Superrotation is strongly suspected on Titan on the basis of numerical studies and observations. The numerical simulation of superrotation is described. It is shown how the general circulation models, originally developed for terrestrial meteorology and climatology, can be used to infer the circulation in such atmospheres. The emphasis is on the case of Titan for which a specific general circulation model was developed.

  9. A Wind Tunnel Model to Explore Unsteady Circulation Control for General Aviation Applications

    NASA Technical Reports Server (NTRS)

    Cagle, Christopher M.; Jones, Gregory S.

    2002-01-01

    Circulation Control airfoils have been demonstrated to provide substantial improvements in lift over conventional airfoils. The General Aviation Circular Control model is an attempt to address some of the concerns of this technique. The primary focus is to substantially reduce the amount of air mass flow by implementing unsteady flow. This paper describes a wind tunnel model that implements unsteady circulation control by pulsing internal pneumatic valves and details some preliminary results from the first test entry.

  10. Prognostic value of circulating VEGFR2+ bone marrow-derived progenitor cells in patients with advanced cancer.

    PubMed

    Massard, Christophe; Borget, Isabelle; Le Deley, Marie Cécile; Taylor, Melissa; Gomez-Roca, Carlos; Soria, Jean Charles; Farace, Françoise

    2012-06-01

    We hypothesised that host-related markers, possibly reflecting tumour aggressiveness, such as circulating endothelial cells (CEC) and circulating VEGFR2(+) bone marrow-derived (BMD) progenitor cells, could have prognostic value in patients with advanced cancer enrolled in early anticancer drug development trials. Baseline CECs (CD45(-)CD31(+)CD146(+)7AAD(-) cells) and circulating VEGFR2(+)-BMD progenitor cells (defined as CD45(dim)CD34(+)VEGFR2(+)7AAD(-) cells) were measured by flow-cytometry in 71 and 58 patients included in phase 1 trials testing novel anti-vascular or anti-angiogenic agents. Correlations between levels of CECs, circulating VEGFR2(+)-BMD progenitor cells, clinical and biological prognostic factors (i.e. the Royal Marsden Hospital (RMH) score), and overall survival (OS) were studied. The median value of CECs was 12 CEC/ml (range 0-154/ml). The median level of VEGFR2(+)-BMD progenitor cells was 1.3% (range 0-32.5%) of circulating BMD-CD34(+) progenitors. While OS was not correlated with CEC levels, it was significantly worse in patients with high VEGFR2(+)-BMD progenitor levels (>1%) (median OS 9.0 versus 17.0 months), and with a RMH prognostic score >0 (median OS 9.0 versus 24.2 months). The prognostic value of VEGFR2(+)-BMD progenitor levels remained significant (hazard ratio (HR) = 2.3, 95% confidence interval (CI), 1.1-4.6, p = 0.02) after multivariate analysis. A composite VEGFR2(+)-BMD progenitor level/RHM score ≥ 2 was significantly associated with an increased risk of death compared to scores of 0 or 1 (median OS 9.0 versus 18.4 months, HR = 2.6 (95%CI, 1.2-5.8, p = 0.02)). High circulating VEGFR2(+)-BMD progenitor levels are associated with poor prognostics and when combined to classical clinical and biological parameters could provide a new tool for patient selection in early anticancer drug trials. PMID:22370181

  11. Platelet proteomics and its advanced application for research of blood stasis syndrome and activated blood circulation herbs of Chinese medicine.

    PubMed

    Liu, Yue; Yin, Huijun; Chen, Keji

    2013-11-01

    The development of novel and efficient antiplatelet agents that have few adverse effects and methods that improve antiplatelet resistance has long been the focus of international research on the prevention and treatment of cardiovascular and cerebrovascular diseases. Recent advances in platelet proteomics have provided a technology platform for high-quality research of platelet pathophysiology and the development of new antiplatelet drugs. The study of blood stasis syndrome (BSS) and activated blood circulation of traditional Chinese medicine (TCM) is one of the most active fields where the integration of TCM and western medicine in China has been successful. Activated blood circulation herbs (ABC herbs) of Chinese medicine are often used in the treatment of BSS. Most ABC herbs have antiplatelet and anti-atherosclerosis activity, but knowledge about their targets is lacking. Coronary heart disease (CHD), BSS, and platelet activation are closely related. By screening and identifying activated platelet proteins that are differentially expressed in BSS of CHD, platelet proteomics has helped researchers interpret the antiplatelet mechanism of action of ABC herbs and provided many potential biomarkers for BSS that could be used to evaluate the clinical curative effect of new antiplatelet drugs. In this article the progress of platelet proteomics and its advanced application for research of BSS and ABC herbs of Chinese medicine are reviewed.

  12. Use of weather types to disaggregate general circulation model predictions

    USGS Publications Warehouse

    Hay, L.E.; McCabe, G.J.; Wolock, D.M.; Ayers, M.A.

    1992-01-01

    A method has been developed that uses weather-type analysis as a tool to spatially disaggregate GCM predictions to make them useful for water resource studies. The method has been applied to the Delaware River basin to predict the effects of doubling atmospheric carbon dioxide on precipitation patterns in the region. An application of the technique to the Delaware River basin indicates that future climate conditions will show minimal changes in weather-type frequency, implying that air circulation patterns will remain unchanged -from Authors

  13. Characterizing the circulation off the Kenyan-Tanzanian coast using an ocean model

    NASA Astrophysics Data System (ADS)

    Gabriela Mayorga-Adame, C.; Ted Strub, P.; Batchelder, Harold P.; Spitz, Yvette H.

    2016-02-01

    The Kenyan-Tanzanian coastal region in the western Indian Ocean faces several environmental challenges including coral reef conservation, fisheries management, coastal erosion, and nearshore pollution. The region lacks hydrodynamic records and oceanographic studies at adequate spatial and temporal scales to provide information relevant to the local environmental issues. We have developed a 4 km horizontal resolution ocean circulation model of the region: the Kenyan-Tanzanian Coastal Model (KTCM) that provides coastal circulation and hydrography with higher resolution than previous models and observational studies of this region. Comparisons to temperature profiles, satellite-derived sea surface temperature and sea surface height anomaly fields, indicate that the model reproduces the main features of the regional circulation, while greatly increasing the details of the nearshore circulation. We describe the seasonal ocean circulation and hydrography of the Kenyan-Tanzanian coastal region based on a climatology of 8 years (2000-2007) of the KTCM simulations. The regional monsoon seasonality produces two distinct coastal circulation regimes: (1) during December-March, there are relatively sluggish shelf flows and (2) during April-November, there are strong northward transports. Simulations from the model will be useful for examining dispersal of pollutants and spatial connectivity of coral reef species.

  14. Exploring the Impact of Students' Learning Approach on Collaborative Group Modeling of Blood Circulation

    ERIC Educational Resources Information Center

    Lee, Shinyoung; Kang, Eunhee; Kim, Heui-Baik

    2015-01-01

    This study aimed to explore the effect on group dynamics of statements associated with deep learning approaches (DLA) and their contribution to cognitive collaboration and model development during group modeling of blood circulation. A group was selected for an in-depth analysis of collaborative group modeling. This group constructed a model in a…

  15. An advanced method for classifying atmospheric circulation types based on prototypes connectivity graph

    NASA Astrophysics Data System (ADS)

    Zagouras, Athanassios; Argiriou, Athanassios A.; Flocas, Helena A.; Economou, George; Fotopoulos, Spiros

    2012-11-01

    Classification of weather maps at various isobaric levels as a methodological tool is used in several problems related to meteorology, climatology, atmospheric pollution and to other fields for many years. Initially the classification was performed manually. The criteria used by the person performing the classification are features of isobars or isopleths of geopotential height, depending on the type of maps to be classified. Although manual classifications integrate the perceptual experience and other unquantifiable qualities of the meteorology specialists involved, these are typically subjective and time consuming. Furthermore, during the last years different approaches of automated methods for atmospheric circulation classification have been proposed, which present automated and so-called objective classifications. In this paper a new method of atmospheric circulation classification of isobaric maps is presented. The method is based on graph theory. It starts with an intelligent prototype selection using an over-partitioning mode of fuzzy c-means (FCM) algorithm, proceeds to a graph formulation for the entire dataset and produces the clusters based on the contemporary dominant sets clustering method. Graph theory is a novel mathematical approach, allowing a more efficient representation of spatially correlated data, compared to the classical Euclidian space representation approaches, used in conventional classification methods. The method has been applied to the classification of 850 hPa atmospheric circulation over the Eastern Mediterranean. The evaluation of the automated methods is performed by statistical indexes; results indicate that the classification is adequately comparable with other state-of-the-art automated map classification methods, for a variable number of clusters.

  16. Axisymmetric circulations forced by heat and momentum sources - A simple model applicable to the Venus atmosphere

    NASA Technical Reports Server (NTRS)

    Hou, A. Y.

    1984-01-01

    A simple mechanistic model of a zonally averaged circulation forced by heat and momentum sources is developed and applied to the Venus atmosphere in the light of recent data. Basic equations for a steady-state axisymmetric circulation are discussed, and the parametric dependence of a nearly inviscid Hadley circulation in the absence of eddy forcing is examined and extended to a wide range of thermal Rossby numbers. The effect of diffusion is considered and found to be small for the Venus cloud region. The zonally averaged eddy sources and sinks required to support the zonal superrotation on Venus are determined.

  17. Interpretation of cloud-climate feedback as produced by 14 atmospheric general circulation models.

    PubMed

    Cess, R D; Potter, G L; Blanchet, J P; Boer, G J; Ghan, S J; Kiehl, J T; LE Treut, H; Li, Z X; Liang, X Z; Mitchell, J F; Morcrette, J J; Randall, D A; Riches, M R; Roeckner, E; Schlese, U; Slingo, A; Taylor, K E; Washington, W M; Wetherald, R T; Yagai, I

    1989-08-01

    Understanding the cause of differences among general circulation model projections of carbon dioxide-induced climatic change is a necessary step toward improving the models. An intercomparison of 14 atmospheric general circulation models, for which sea surface temperature perturbations were used as a surrogate climate change, showed that there was a roughly threefold variation in global climate sensitivity. Most of this variation is attributable to differences in the models' depictions of cloud-climate feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as climatic predictors.

  18. Interpretation of cloud-climate feedback as produced by 14 atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Potter, G. L.; Ghan, S. J.; Blanchet, J. P.; Boer, G. J.

    1989-01-01

    Understanding the cause of differences among general circulation model projections of carbon dioxide-induced climatic change is a necessary step toward improving the models. An intercomparison of 14 atmospheric general circulation models, for which sea surface temperature perturbations were used as a surrogate climate change, showed that there was a roughly threefold variation in global climate sensitivity. Most of this variation is attributable to differences in the models' depictions of cloud-climate feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as climatic predictors.

  19. Numerical Model Studies of the Martian Mesoscale Circulations

    NASA Technical Reports Server (NTRS)

    Segal, M.; Arritt, R. W.

    1996-01-01

    Studies concerning mesoscale topographical effects on Martian flows examined low-level jets in the near equatorial latitudes and the dynamical intensification of flow by steep terrain. Continuation of work from previous years included evaluating the dissipation of cold air mass outbreaks due to enhanced sensible heat flux, further sensitivity and scaling evaluations for generalization of the characteristics of Martian mesoscale circulation caused by horizontal sensible heat-flux gradients, and evaluations of the significance that non-uniform surface would have on enhancing the polar CO2 ice sublimation during the spring. The sensitivity of maximum and minimum atmospheric temperatures to changes in wind speed, surface albedo, and deep soil temperature was investigated.

  20. Chemical Kinetic Modeling of Advanced Transportation Fuels

    SciTech Connect

    PItz, W J; Westbrook, C K; Herbinet, O

    2009-01-20

    Development of detailed chemical kinetic models for advanced petroleum-based and nonpetroleum based fuels is a difficult challenge because of the hundreds to thousands of different components in these fuels and because some of these fuels contain components that have not been considered in the past. It is important to develop detailed chemical kinetic models for these fuels since the models can be put into engine simulation codes used for optimizing engine design for maximum efficiency and minimal pollutant emissions. For example, these chemistry-enabled engine codes can be used to optimize combustion chamber shape and fuel injection timing. They also allow insight into how the composition of advanced petroleum-based and non-petroleum based fuels affect engine performance characteristics. Additionally, chemical kinetic models can be used separately to interpret important in-cylinder experimental data and gain insight into advanced engine combustion processes such as HCCI and lean burn engines. The objectives are: (1) Develop detailed chemical kinetic reaction models for components of advanced petroleum-based and non-petroleum based fuels. These fuels models include components from vegetable-oil-derived biodiesel, oil-sand derived fuel, alcohol fuels and other advanced bio-based and alternative fuels. (2) Develop detailed chemical kinetic reaction models for mixtures of non-petroleum and petroleum-based components to represent real fuels and lead to efficient reduced combustion models needed for engine modeling codes. (3) Characterize the role of fuel composition on efficiency and pollutant emissions from practical automotive engines.

  1. Advancements in engineering turbulence modeling

    NASA Technical Reports Server (NTRS)

    Shih, T.-H.

    1991-01-01

    Some new developments in two-equation models and second order closure models are presented. Two-equation models (k-epsilon models) have been widely used in computational fluid dynamics (CFD) for engineering problems. Most of low-Reynolds number two-equation models contain some wall-distance damping functions to account for the effect of wall on turbulence. However, this often causes the confusion and difficulties in computing flows with complex geometry and also needs an ad hoc treatment near the separation and reattachment points. A set of modified two-equation models is proposed to remove the aforementioned shortcomings. The calculations using various two-equation models are compared with direct numerical simulations of channel flow and flat boundary layers. Development of a second order closure model is also discussed with emphasis on the modeling of pressure related correlation terms and dissipation rates in the second moment equations. All the existing models poorly predict the normal stresses near the wall and fail to predict the 3-D effect of mean flow on the turbulence (e.g. decrease in the shear stress caused by the cross flow in the boundary layer). The newly developed second order near-wall turbulence model is described and is capable of capturing the near-wall behavior of turbulence as well as the effect of 3-D mean flow on the turbulence.

  2. The application of Seasat-1 radar altimetry to continental shelf circulation modeling

    NASA Technical Reports Server (NTRS)

    Cornillon, P.; Reed, M.; Spaulding, M.; Swanson, C.

    1980-01-01

    Seasat-1 radar altimetry data have been used to verify a continental shelf circulation model subjected to tidal forcing on the open boundary. The model makes use of the semi-implicit mode of time integration, removing the surface gravity wave time step restriction. Both the altimetry and the model predictions are compared with empirically determined tidal fluctuations and generally good agreement is obtained.

  3. Standpipe models for diagnostics and control of a circulating fluidized bed

    SciTech Connect

    Ludlow, James C.; Panday, Rupen

    2013-01-01

    Two models for a Circulating Fluidized Bed (CFB) standpipe were formulated, implemented and validated to estimate critical CFB operational parameters. The first model continuously estimates standpipe bed height using incremental pressure measurements within the standpipe. The second model estimates variations in the void fraction along the standpipe using the Ergun equation in conjunction with the overall pressure drop across the bed, solids circulation rate and the standpipe aeration flows introduced at different locations of the pipe. The importance of different standpipe parameters obtained from these models is discussed in terms of successful operation of the overall CFB system. Finally, the applications of these models are shown in improving the solids circulation rate measurement and in calculating riser inventory.

  4. Left ventricular finite element model bounded by a systemic circulation model.

    PubMed

    Veress, A I; Raymond, G M; Gullberg, G T; Bassingthwaighte, J B

    2013-05-01

    A series of models were developed in which a circulatory system model was coupled to an existing series of finite element (FE) models of the left ventricle (LV). The circulatory models were used to provide realistic boundary conditions for the LV models. This was developed for the JSim analysis package and was composed of a systemic arterial, capillary, and venous system in a closed loop with a varying elastance LV and left atria to provide the driving pressures and flows matching those of the FE model. Three coupled models were developed, a normal LV under normotensive aortic loading (116/80 mm Hg), a mild hypertension (137/89 mm Hg) model, and a moderate hypertension model (165/100 mm Hg). The initial step in the modeling analysis was that the circulation was optimized to the end-diastolic pressure and volume values of the LV model. The cardiac FE models were then optimized to the systolic pressure/volume characteristics of the steady-state JSim circulatory model solution. Comparison of the stress predictions for the three models indicated that the mild hypertensive case produced a 21% increase in the average fiber stress levels, and the moderate hypertension case had a 36% increase in average stress. The circulatory work increased by 18% and 43% over that of the control for the mild and moderate hypertensive cases, respectively.

  5. Modeling of Spacecraft Advanced Chemical Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Benfield, Michael P. J.; Belcher, Jeremy A.

    2004-01-01

    This paper outlines the development of the Advanced Chemical Propulsion System (ACPS) model for Earth and Space Storable propellants. This model was developed by the System Technology Operation of SAIC-Huntsville for the NASA MSFC In-Space Propulsion Project Office. Each subsystem of the model is described. Selected model results will also be shown to demonstrate the model's ability to evaluate technology changes in chemical propulsion systems.

  6. 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.

  7. Water circulation and global mantle dynamics: Insight from numerical modeling

    NASA Astrophysics Data System (ADS)

    Nakagawa, Takashi; Nakakuki, Tomoeki; Iwamori, Hikaru

    2015-05-01

    We investigate water circulation and its dynamical effects on global-scale mantle dynamics in numerical thermochemical mantle convection simulations. Both dehydration-hydration processes and dehydration melting are included. We also assume the rheological properties of hydrous minerals and density reduction caused by hydrous minerals. Heat transfer due to mantle convection seems to be enhanced more effectively than water cycling in the mantle convection system when reasonable water dependence of viscosity is assumed, due to effective slab dehydration at shallow depths. Water still affects significantly the global dynamics by weakening the near-surface oceanic crust and lithosphere, enhancing the activity of surface plate motion compared to dry mantle case. As a result, including hydrous minerals, the more viscous mantle is expected with several orders of magnitude compared to the dry mantle. The average water content in the whole mantle is regulated by the dehydration-hydration process. The large-scale thermochemical anomalies, as is observed in the deep mantle, is found when a large density contrast between basaltic material and ambient mantle is assumed (4-5%), comparable to mineral physics measurements. Through this study, the effects of hydrous minerals in mantle dynamics are very important for interpreting the observational constraints on mantle convection.

  8. Mapping tidal residual circulations in the outer Xiangshan Bay using a numerical model

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Mao, Xinyan; Jiang, Wensheng

    2016-02-01

    Xiangshan Bay, which is elongated and semi-enclosed, is characterized by strong tides. The original understanding of the tidal residual circulation in the bay was based on the Eulerian time-mean method. However, it has been theoretically proved that the Lagrangian time-mean method rather than the Eulerian one should be employed to detide. This knowledge motivated us to remap the tidal residual circulation in the bay. A three-dimensional numerical model with a Lagrangian particle-tracking module was used to simulate tides, from which the Lagrangian and Eulerian tidal residual circulations were produced. The Lagrangian residual circulation exhibited a two-branch pattern that connected the southern and northern outer seas of Xiangshan Bay, whereas the Eulerian residual circulation was characterized by eddies that are not favorable for water exchange. Through comparing to the observed salinity distribution, the Lagrangian residual current presented a reasonable spatial pattern which could explain the inter-tidal mass transport. Furthermore, the Lagrangian residual current performed better in sustaining the mass conservation as predicted by theory. A series of sensitivity experiments were conducted to investigate the effect of nonlinear mechanisms on the Lagrangian residual circulation. The results showed that nonlinear advection is dominant while the time-varying width and depth play a minor role, and the quadratic bottom friction has no influence with only M2 tide driving the model.

  9. A long term model of circulation. [human body

    NASA Technical Reports Server (NTRS)

    White, R. J.

    1974-01-01

    A quantitative approach to modeling human physiological function, with a view toward ultimate application to long duration space flight experiments, was undertaken. Data was obtained on the effect of weightlessness on certain aspects of human physiological function during 1-3 month periods. Modifications in the Guyton model are reviewed. Design considerations for bilateral interface models are discussed. Construction of a functioning whole body model was studied, as well as the testing of the model versus available data.

  10. Mars Global Surveyor: Aerobraking and Observations Support Using a Mars Global Circulation Model

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Harberle, Robert M.

    1997-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. Using a global atmospheric circulation model for Mars, the focus of this JRI has been to provide support for the Mars Global Surveyor (MGS) spacecraft aerobraking activities and interpretation guidance of preliminary observations. ne primary atmospheric model applied in this investigation has been a high-top version of the NASA Ames Mars general circulation model (MGCM). Comparisons with an atmospheric model designed primarily for engineering purposes (Mars-GRAM) has also been carried out. From a suite of MGCM simulations, we have assessed plausible spatial and temporal variability in atmospheric density at high altitudes (e.g., 70-110 km) for seasonal dates and locations during Phase 1 aerobraking. Diagnostic tools have been developed to analyze circulation fields from the MGCM simulations, and these tools have been applied in the creation of a Mars climate catalogue database. Throughout Phase 1 aerobraking activities, analysis products have been provided to the MGS aerobraking atmospheric advisory group (AAG). Analyses of circulation variability at the coupling level between the MGCM and a Mars thermospheric global circulation model (MTGCM) has also been assessed. Finally, using a quasi-geostrophic dynamical formulation with the MGCM simulations, diagnosis of breaking planetary (Rossby) waves in Mars' middle atmosphere has been carried out. Titles of papers presented at scientific workshops and seminars, and a publication in the scientific literature are provided.

  11. Mars Global Surveyor: Aerobraking and Observations Support Using a Mars Global Circulation Model

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1997-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. Using a global atmospheric circulation model for Mars, the focus of this JRI has been to provide support for the Mars Global Surveyor (MGS) spacecraft aerobraking activities and interpretation guidance of preliminary observations. The primary atmospheric model applied in this investigation has been a high-top version of the NASA Ames Mars general circulation model (MGCM). Comparisons with an atmospheric model designed primarily for engineering purposes (Mars-GRAM) has also been carried out. From a suite of MGCM simulations, we have assessed plausible spatial and temporal variability in atmospheric density at high altitudes (e.g., 70-110 km) for seasonal dates and locations during Phase I aerobraking. Diagnostic tools have been developed to analyze circulation fields from the MGCM simulations, and these tools have been applied in the creation of a Mars climate catalogue database. Throughout Phase I aerobraking activities, analysis products have been provided to the MGS aerobraking atmospheric advisory group (AAG). Analyses of circulation variability at the coupling level between the MGCM and a Mars thermospheric global circulation model (MTGCM) has also been assessed. Finally, using a quasi-geostrophic dynamical formulation with the MGCM simulations, diagnosis of breaking planetary (Rossby) waves in Mars' middle atmosphere has been carried out. Titles of papers presented at scientific workshops and seminars, and a publication in the scientific literature are provided.

  12. Mars Global Surveyor: Aerobraking and Observations Support Using a Mars Global Circulation Model

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1997-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. Using a global atmospheric circulation model for Mars, the focus of this JRI has been to provide support for the Mars Global Surveyor (MGS) spacecraft aerobraking activities and interpretation guidance of preliminary observations. The primary atmospheric model applied in this investigation has been a high-top version of the NASA Ames Mars general circulation model (MGCM). Comparisons with an atmospheric model designed primarily for engineering purposes (Mars-GRAM) has also been carried out. From a suite of MGCM simulations, we have assessed plausible spatial and temporal variability in atmospheric density at high altitudes (e.g., 70-1 10 km) for seasonal dates and locations during Phase 1 aerobraking. Diagnostic tools have been developed to analyze circulation fields from the MGCM simulations, and these tools have been applied in the creation of a Mars climate catalogue database. Throughout Phase I aerobraking activities, analysis products have been provided to the MGS aerobraking atmospheric advisory group (AAG). Analyses of circulation variability at the coupling level between the MGCM and a Mars thermospheric global circulation model (MTGCM) has also been assessed. Finally, using a quasi-geostrophic dynamical formulation with the MGCM simulations, diagnosis of breaking planetary (Rossby) waves in Mars middle atmosphere has been carried out. Titles of papers presented at scientific workshops and seminars, and a publication in the scientific literature are provided.

  13. Modeling the 1998-2003 summer circulation and thermal structure in Lake Michigan

    NASA Astrophysics Data System (ADS)

    Beletsky, Dmitry; Schwab, David; McCormick, Michael

    2006-10-01

    A three-dimensional primitive equation numerical model was applied to Lake Michigan on a 2 km grid for 6 consecutive years to study interannual variability of summer circulation and thermal structure in 1998-2003. The model results were compared to long-term observations of currents and temperature at seven moorings and two NOAA buoys. The accuracy of modeled currents improved considerably relative to previous summer circulation modeling done on a 5 km grid, while the accuracy of temperature simulations remained the same. Particle trajectory model results were also compared with satellite-tracked surface drifter observations. Large-scale circulation patterns tend to be more cyclonic (counterclockwise) toward the end of summer as the thermocline deepens and density effects become more important. Circulation in southern Lake Michigan appears to be more variable than circulation in northern Lake Michigan. An important new feature not previously seen in observations was found in southern Lake Michigan: an anticyclonic gyre extending northward from the southern shore of Lake Michigan, sometimes occupying the entire southern basin.

  14. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Cen- ter and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical "cores" of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. ne two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical "simple physics" parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  15. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical "cores" of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. The two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical "simple physics" parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  16. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical 'cores' of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. The two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical 'simple physics' parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  17. Identification of liver CYP51 as a gene responsive to circulating cholesterol in a hamster model.

    PubMed

    Huang, Haiqiu; Xie, Zhuohong; Yokoyama, Wallace; Yu, Liangli; Wang, Thomas T Y

    2016-01-01

    Hypercholesterolaemia is a risk factor for CVD, which is a leading cause of death in industrialised societies. The biosynthetic pathways for cholesterol metabolism are well understood; however, the regulation of circulating cholesterol by diet is still not fully elucidated. The present study aimed to gain more comprehensive understanding of the relationship between circulating cholesterol levels and molecular effects in target tissues using the hamster model. Male golden Syrian hamsters were fed with chow or diets containing 36 % energy from fat with or without 1 % cholesteyramine (CA) as a modulator of circulating cholesterol levels for 35 d. It was revealed that the expression of lanosterol 14α-demethylase (CYP51) instead of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase mRNA expression was responsive to circulating cholesterol in hamsters fed hypercholesterolaemic diets. The high-fat diet increased circulating cholesterol and down-regulated CYP51, but not HMG-CoA reductase. The CA diet decreased cholesterol and increased CYP51 expression, but HMG-CoA reductase expression was not affected. The high-fat diet and CA diet altered the expression level of cholesterol, bile acids and lipid metabolism-associated genes (LDL receptor, cholesterol 7α-hydroxylase (CYP7A1), liver X receptor (LXR) α, and ATP-binding cassette subfamily G member 5/8 (ABCG5/8)) in the liver, which were significantly correlated with circulating cholesterol levels. Correlation analysis also showed that circulating cholesterol levels were regulated by LXR/retinoid X receptor and PPAR pathways in the liver. Using the hamster model, the present study provided additional molecular insights into the influence of circulating cholesterol on hepatic cholesterol metabolism pathways during hypercholesterolaemia. PMID:27110359

  18. The influence of the tropics upon the prediction of the Southern Hemisphere circulation within the GLAS GCM. [Goddard Laboratory for Atmospheric Sciences General Circulation Model

    NASA Technical Reports Server (NTRS)

    Baker, W. E.; Paegle, J.

    1983-01-01

    An examination is undertaken of the sensitivity of short term Southern Hemisphere circulation prediction to tropical wind data and tropical latent heat release. The data assimilation experiments employ the Goddard Laboratory for Atmospheric Sciences' fourth-order general circulation model. Two of the experiments are identical, but for the fact that one uses tropical wind data while the other does not. A third experiment contains the identical initial conditions of forecasts with tropical winds, while suppressing tropical latent heat release.

  19. Computational models of the pulmonary circulation: Insights and the move towards clinically directed studies

    PubMed Central

    Tawhai, Merryn H.; Clark, Alys R.; Burrowes, Kelly S.

    2011-01-01

    Biophysically-based computational models provide a tool for integrating and explaining experimental data, observations, and hypotheses. Computational models of the pulmonary circulation have evolved from minimal and efficient constructs that have been used to study individual mechanisms that contribute to lung perfusion, to sophisticated multi-scale and -physics structure-based models that predict integrated structure-function relationships within a heterogeneous organ. This review considers the utility of computational models in providing new insights into the function of the pulmonary circulation, and their application in clinically motivated studies. We review mathematical and computational models of the pulmonary circulation based on their application; we begin with models that seek to answer questions in basic science and physiology and progress to models that aim to have clinical application. In looking forward, we discuss the relative merits and clinical relevance of computational models: what important features are still lacking; and how these models may ultimately be applied to further increasing our understanding of the mechanisms occurring in disease of the pulmonary circulation. PMID:22034608

  20. Regional climates in the GISS general circulation model: Surface air temperature

    NASA Technical Reports Server (NTRS)

    Hewitson, Bruce

    1994-01-01

    One of the more viable research techniques into global climate change for the purpose of understanding the consequent environmental impacts is based on the use of general circulation models (GCMs). However, GCMs are currently unable to reliably predict the regional climate change resulting from global warming, and it is at the regional scale that predictions are required for understanding human and environmental responses. Regional climates in the extratropics are in large part governed by the synoptic-scale circulation and the feasibility of using this interscale relationship is explored to provide a way of moving to grid cell and sub-grid cell scales in the model. The relationships between the daily circulation systems and surface air temperature for points across the continental United States are first developed in a quantitative form using a multivariate index based on principal components analysis (PCA) of the surface circulation. These relationships are then validated by predicting daily temperature using observed circulation and comparing the predicted values with the observed temperatures. The relationships predict surface temperature accurately over the major portion of the country in winter, and for half the country in summer. These relationships are then applied to the surface synoptic circulation of the Goddard Institute for Space Studies (GISS) GCM control run, and a set of surface grid cell temperatures are generated. These temperatures, based on the larger-scale validated circulation, may now be used with greater confidence at the regional scale. The generated temperatures are compared to those of the model and show that the model has regional errors of up to 10 C in individual grid cells.

  1. Advanced Space Shuttle simulation model

    NASA Technical Reports Server (NTRS)

    Tatom, F. B.; Smith, S. R.

    1982-01-01

    A non-recursive model (based on von Karman spectra) for atmospheric turbulence along the flight path of the shuttle orbiter was developed. It provides for simulation of instantaneous vertical and horizontal gusts at the vehicle center-of-gravity, and also for simulation of instantaneous gusts gradients. Based on this model the time series for both gusts and gust gradients were generated and stored on a series of magnetic tapes, entitled Shuttle Simulation Turbulence Tapes (SSTT). The time series are designed to represent atmospheric turbulence from ground level to an altitude of 120,000 meters. A description of the turbulence generation procedure is provided. The results of validating the simulated turbulence are described. Conclusions and recommendations are presented. One-dimensional von Karman spectra are tabulated, while a discussion of the minimum frequency simulated is provided. The results of spectral and statistical analyses of the SSTT are presented.

  2. Uncertainties in carbon dioxide radiative forcing in atmospheric general circulation models.

    PubMed

    Cess, R D; Zhang, M H; Potter, G L; Barker, H W; Colman, R A; Dazlich, D A; Del Genio, A D; Esch, M; Fraser, J R; Galin, V; Gates, W L; Hack, J J; Ingram, W J; Kiehl, J T; Lacis, A A; Le Treut, H; Li, Z X; Liang, X Z; Mahfouf, J F; McAvaney, B J; Meleshko, V P; Morcrette, J J; Randall, D A; Roeckner, E; Royer, J F; Sokolov, A P; Sporyshev, P V; Taylor, K E; Wang, W C; Wetherald, R T

    1993-11-19

    Global warming caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  3. A MODEL FOR FINE PARTICLE AGGLOMERATION IN CIRCULATING FLUIDIZED BED ABSORBERS

    EPA Science Inventory

    A model for fine particle agglomeration in circulating fluidized bed absorbers (CFBAS) has been developed. It can model the influence of different factors on agglomeration, such as the geometry of CFBAs, superficial gas velocity, initial particle size distribution, and type of ag...

  4. Documentation of the GLAS fourth order general circulation model. Volume 2: Scalar code

    NASA Technical Reports Server (NTRS)

    Kalnay, E.; Balgovind, R.; Chao, W.; Edelmann, D.; Pfaendtner, J.; Takacs, L.; Takano, K.

    1983-01-01

    Volume 2, of a 3 volume technical memoranda contains a detailed documentation of the GLAS fourth order general circulation model. Volume 2 contains the CYBER 205 scalar and vector codes of the model, list of variables, and cross references. A variable name dictionary for the scalar code, and code listings are outlined.

  5. Numerical modeling of circulation in high-energy estuaries: A Columbia River estuary benchmark

    NASA Astrophysics Data System (ADS)

    Kärnä, Tuomas; Baptista, António M.; Lopez, Jesse E.; Turner, Paul J.; McNeil, Craig; Sanford, Thomas B.

    2015-04-01

    Numerical modeling of three-dimensional estuarine circulation is often challenging due to complex flow features and strong density gradients. In this paper the skill of a specific model is assessed against a high-resolution data set, obtained in a river-dominated mesotidal estuary with autonomous underwater vehicles and a shipborne winched profiler. The measurements provide a detailed view of the salt wedge dynamics of the Columbia River estuary. Model skill is examined under contrasting forcing conditions, covering spring freshet and autumn low flow conditions, as well as spring and neap tides. The data set provides a rigorous benchmark for numerical circulation models. This benchmark is used herein to evaluate an unstructured grid circulation model, based on linear finite element and finite volume formulations. Advection of momentum is treated with an Eulerian-Lagrangian scheme. After the model's sensitivity to grid resolution and time step is examined, a detailed skill assessment is provided for the best model configuration. The simulations reproduce the timing and tidal asymmetry of salinity intrusion. Sharp density gradients, however, tend to be smoothed out affecting vertical mixing and gravitational circulation. We show that gravitational salt transport is underestimated in the model, but is partially compensated through tidal effects. The discrepancy becomes most pronounced when the stratification is strongest, i.e., under high river discharge and neap tide conditions.

  6. Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M.-H.; Potter, G. L.; Gates, W. L.; Taylor, K. E.; Barker, H. W.; Colman, R. A.; Fraser, J. R.; McAvaney, B. J.; Dazlich, D. A.; Randall, D. A.; DelGenio, A. D.; Lacis, A. A.; Esch, M.; Roeckner, E.; Galin, V.; Hack, J. J.; Kiehl, J. T.; Ingram, W. J.; LeTreut, H.

    1993-01-01

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  7. Micromechanical modeling of advanced materials

    SciTech Connect

    Silling, S.A.; Taylor, P.A.; Wise, J.L.; Furnish, M.D.

    1994-04-01

    Funded as a laboratory-directed research and development (LDRD) project, the work reported here focuses on the development of a computational methodology to determine the dynamic response of heterogeneous solids on the basis of their composition and microstructural morphology. Using the solid dynamics wavecode CTH, material response is simulated on a scale sufficiently fine to explicitly represent the material`s microstructure. Conducting {open_quotes}numerical experiments{close_quotes} on this scale, the authors explore the influence that the microstructure exerts on the material`s overall response. These results are used in the development of constitutive models that take into account the effects of microstructure without explicit representation of its features. Applying this methodology to a glass-reinforced plastic (GRP) composite, the authors examined the influence of various aspects of the composite`s microstructure on its response in a loading regime typical of impact and penetration. As a prerequisite to the microscale modeling effort, they conducted extensive materials testing on the constituents, S-2 glass and epoxy resin (UF-3283), obtaining the first Hugoniot and spall data for these materials. The results of this work are used in the development of constitutive models for GRP materials in transient-dynamics computer wavecodes.

  8. Modeling Advance Life Support Systems

    NASA Technical Reports Server (NTRS)

    Pitts, Marvin; Sager, John; Loader, Coleen; Drysdale, Alan

    1996-01-01

    Activities this summer consisted of two projects that involved computer simulation of bioregenerative life support systems for space habitats. Students in the Space Life Science Training Program (SLSTP) used the simulation, space station, to learn about relationships between humans, fish, plants, and microorganisms in a closed environment. One student complete a six week project to modify the simulation by converting the microbes from anaerobic to aerobic, and then balancing the simulation's life support system. A detailed computer simulation of a closed lunar station using bioregenerative life support was attempted, but there was not enough known about system restraints and constants in plant growth, bioreactor design for space habitats and food preparation to develop an integrated model with any confidence. Instead of a completed detailed model with broad assumptions concerning the unknown system parameters, a framework for an integrated model was outlined and work begun on plant and bioreactor simulations. The NASA sponsors and the summer Fell were satisfied with the progress made during the 10 weeks, and we have planned future cooperative work.

  9. Accurate mask model for advanced nodes

    NASA Astrophysics Data System (ADS)

    Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Ndiaye, El Hadji Omar; Mishra, Kushlendra; Paninjath, Sankaranarayanan; Bork, Ingo; Buck, Peter; Toublan, Olivier; Schanen, Isabelle

    2014-07-01

    Standard OPC models consist of a physical optical model and an empirical resist model. The resist model compensates the optical model imprecision on top of modeling resist development. The optical model imprecision may result from mask topography effects and real mask information including mask ebeam writing and mask process contributions. For advanced technology nodes, significant progress has been made to model mask topography to improve optical model accuracy. However, mask information is difficult to decorrelate from standard OPC model. Our goal is to establish an accurate mask model through a dedicated calibration exercise. In this paper, we present a flow to calibrate an accurate mask enabling its implementation. The study covers the different effects that should be embedded in the mask model as well as the experiment required to model them.

  10. Modeling tidal circulation and stratification in Skagit River estuary using an unstructured grid ocean model

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoqing; Khangaonkar, Tarang

    Tidal circulation and river plume dynamics in shallow-water estuarine systems with large intertidal zones are complex. Strong asymmetries in tidal currents and stratification often occur in the intertidal zones and subtidal channels over a tidal cycle. The Skagit River is the largest estuary with respect to the discharge of a significant amount of freshwater and sediment into Puget Sound, Washington. It consists of a large intertidal zone with multiple tidal channels near the mouth of the estuary. To simulate the tidal circulation and salinity stratification accurately in the intertidal region, an unstructured grid numerical model with wetting-drying capability and the capability to accurately represent the bathymetry of tidal flats and the geometry of shallow distributary channels is necessary. In this paper, a modeling study for the Skagit River estuary using a three-dimensional unstructured grid, finite-volume coastal ocean model (FVCOM) supported by high-resolution LIDAR data is presented. The hydrodynamic model was validated with observed water surface elevation, velocity, and salinity data over spring and neap tidal cycles under low-river-flow and high-river-flow conditions. Wetting and drying processes in the intertidal zone and strong stratification in the estuary were simulated successfully by the model. Model results indicate that the Skagit River estuary is a highly stratified estuary, but destratification can occur during flood tide. Tides and baroclinic motion are the dominant forcing in the Skagit River estuary, but strong wind events can affect the currents in the intertidal zone significantly. Preliminary analysis also indicated that the salinity intrusion length scale is proportional to the river flow to the -¼ power.

  11. A vertically averaged spectral model for tidal circulation in estuaries

    USGS Publications Warehouse

    Burau, J.R.; Cheng, R.T.

    1989-01-01

    A frequency dependent computer model based on the two-dimensional vertically averaged shallow-water equations is described for general purpose application in tidally dominated embayments. This model simulates the response of both tides and tidal currents to user-specified geometries and boundary conditions. The mathematical formulation and practical application of the model are discussed in detail. Salient features of the model include the ability to specify: (1) stage at the open boundaries as well as within the model grid, (2) velocities on open boundaries (river inflows and so forth), (3) spatially variable wind stress, and (4) spatially variable bottom friction. Using harmonically analyzed field data as boundary conditions, this model can be used to make real time predictions of tides and tidal currents. (USGS)

  12. Idealised modelling of ocean circulation driven by geothermal and hydrothermal fluxes at the seabed

    NASA Astrophysics Data System (ADS)

    Barnes, Jowan; Morales Maqueda, Miguel; Polton, Jeff

    2016-04-01

    There are two distinct processes by which heat is transferred from the solid Earth into the abyssal ocean. The first is conductive geothermal heating and the second is hydrothermal heating, involving advection of heated water from within the Earth's crust. Here, the noticeably different impacts of these two physical systems on ocean circulation are investigated. Previous modelling studies have applied geothermal heat fluxes at the seabed and shown discrepancies in circulation compared to cases which neglected heat from the Earth in their boundary conditions. The true heat flux in the ocean, however, is not entirely geothermal. From areas where the crust is younger a significant proportion of the heat input from the Earth could be in the form of fluid flow from hydrothermal vents, introducing forcing to the circulation which has previously been unaccounted for. In this study a set of idealised modelling experiments are run in order to investigate the effects of changing the balance of the total heat flux from purely geothermal to purely hydrothermal, via intermediate states in which the two boundary conditions are combined in different ratios. By performing such experiments it will be shown which of the two processes is dominant in its effects on circulation driven by heating at the seabed, and whether neglecting the hydrothermal advection in favour of a fully conductive geothermal boundary condition is justifiable. The results will inform the construction of boundary conditions for future circulation models involving ocean floor heat fluxes, specifically a regional study of geothermal and hydrothermal contributions within the Panama Basin.

  13. A Hydrodynamic Model of The Human Leg Circulation.

    ERIC Educational Resources Information Center

    Klabunde, Richard E.; McDowell, Donald E.

    1984-01-01

    Describes the construction and use of a life-size model which shows blood flow under normal and pathological conditions. Four experimental procedures (single vessel occlusion, dilation of distal vascular bed, single artery stenosis, and multiple artery stenoses) typical of those demonstrated by the model are discussed and diagrammed. (DH)

  14. 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.

  15. Recent results from the GISS model of the global atmosphere. [circulation simulation for weather forecasting

    NASA Technical Reports Server (NTRS)

    Somerville, R. C. J.

    1975-01-01

    Large numerical atmospheric circulation models are in increasingly widespread use both for operational weather forecasting and for meteorological research. The results presented here are from a model developed at the Goddard Institute for Space Studies (GISS) and described in detail by Somerville et al. (1974). This model is representative of a class of models, recently surveyed by the Global Atmospheric Research Program (1974), designed to simulate the time-dependent, three-dimensional, large-scale dynamics of the earth's atmosphere.

  16. A Simplified Teaching Model of the Heart and Circulation

    ERIC Educational Resources Information Center

    Rodbard, Simon; And Others

    1976-01-01

    Diagrams and explains the construction of a model for the heart and its valves and function of the atria and ventricles, using the contraction of a student's hand to simulate heart contraction. Approximate cost $125. (CS)

  17. Prediction of cloud droplet number in a general circulation model

    SciTech Connect

    Ghan, S.J.; Leung, L.R.

    1996-04-01

    We have applied the Colorado State University Regional Atmospheric Modeling System (RAMS) bulk cloud microphysics parameterization to the treatment of stratiform clouds in the National Center for Atmospheric Research Community Climate Model (CCM2). The RAMS predicts mass concentrations of cloud water, cloud ice, rain and snow, and number concnetration of ice. We have introduced the droplet number conservation equation to predict droplet number and it`s dependence on aerosols.

  18. Modeling of clouds and radiation for developing parameterizations for general circulation models. Annual report, 1995

    SciTech Connect

    Toon, O.B.; Westphal, D.L.

    1996-07-01

    We have used a hierarchy of numerical models for cirrus and stratus clouds and for radiative transfer to improve the reliability of general circulation models. Our detailed cloud microphysical model includes all of the physical processes believed to control the lifecycles of liquid and ice clouds in the troposphere. We have worked on specific GCM parameterizations for the radiative properties of cirrus clouds, making use of a mesocale model as the test-bed for the parameterizations. We have also modeled cirrus cloud properties with a detailed cloud physics model to better understand how the radiatively important properties of cirrus are controlled by their environment. We have used another cloud microphysics model to investigate of the interactions between aerosols and clouds. This work is some of the first to follow the details of interactions between aerosols and cloud droplets and has shown some unexpected relations between clouds and aerosols. We have also used line-by- line radiative transfer results verified with ARM data, to derive a GCMS.

  19. Modeling and model validation of wind-driven circulation in Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Cheng, R.T.; Gartner, J.W.; Wood, T.

    2005-01-01

    The hydrodynamics in the Upper Klamath Lake (UKL) plays a significant role in the water quality conditions of the lake. In order to provide a quantitative evaluation of the impacts of hydrodynamics on water quality in UKL, a detailed hydrodynamic model was implemented using an unstructured grid 3-D hydrodynamic model known as the UnTRIM model. The circulation in UKL is driven primarily by wind. Wind speed and direction time-series records were used as input, the numerical model reproduced the wind "set-up" and "set-down" at down wind and upwind ends of the lake, respectively. Of the two acoustic Doppler current profiler (ADCP) records, the UnTRIM model reproduced the measured velocity at the deep station. At the shallow station, the model results showed diurnal patterns that correlated well with wind variations, but the measured velocity showed water velocity sustained at 3 to 5 cm/sec or above. Discrepancies between the model results and observations at the shallow ADCP station is discussed on the basis of correct physics. If the field measurements are inconsistent with the known physics, there exists the possibility that the field data are suspect or the field data are revealing some physical processes that are not yet understood. Copyright ASCE 2005.

  20. Land-Atmosphere Interactions and Mesoscale Circulations in an Idealized Modeling Framework

    NASA Astrophysics Data System (ADS)

    Grant, L. D.; van den Heever, S. C.; Lu, L.

    2012-12-01

    Many studies have shown that land-atmosphere interactions and feedbacks have important implications for regional climate systems. For instance, clouds and precipitation alter radiation stream profiles, both of which influence land surface fluxes and change the partition between latent and sensible heating. This directly influences boundary layer temperature and moisture regimes and thus subsequent cloud and precipitation formation. Heterogeneous land surface characteristics, due for example to desertification, deforestation, or biomass burning -- all of which occur in Africa -- can also induce mesoscale circulations. Mesoscale circulations spatially impact boundary layer structure and convective initiation. We are investigating these interactions and feedbacks under an idealized framework using the Regional Atmospheric Modeling System (RAMS) version 6.0 and the Land Ecosystem-Atmosphere Feedback (LEAF) model version 3. Several-month simulations have been conducted at convection-resolving scales using periodic boundary conditions and different land surface types representative of surface characteristics in Africa. Results from these idealized simulations will be presented, with a focus on: (1) the influence of land surface properties including albedo, roughness length, soil moisture, and leaf area index on resultant mesoscale circulations and cloudy and precipitating regions; and (2) subsequent feedbacks to surface energy fluxes, shortwave and longwave radiation streams, and heating rates. Preliminary results indicate that both shallower boundary layer and deeper, more elevated mesoscale circulations are present due to the contrasting land surfaces. The circulations vary by season and influence convective development, precipitation, and surface and atmospheric thermodynamic structure. Potential implications for water cycle dynamics in Africa will be discussed.

  1. Improvement in Geoid Models for Ocean Circulation Studies

    NASA Technical Reports Server (NTRS)

    Tapley, Byron D.; Chambers, Don P.; Poole, Steve; Ries, John c.

    2003-01-01

    At wavelengths of 500 km and longer, the GRACE GGM01 Model produces a significantly better marine geoid than any previous model. This conclusion follows from evaluating the geostrophic currents determined by combining the model with a mean sea surface from altimetry. The agreement with currents computed from a traditional hydrographic map is very close, which suggests that one of the primary missions of the TOPEX/POSEIDON mission, to determine the absolute dynamic ocean topography, may soon be met. This solution has been made available to the public at http://www.csr.utexs.edu/grace/gravity. The results reported in this paper have been presented at the 2003 EGS-AGU-EUG Joint Assembly. Two articles are currently being prepared for Geophysical Research Letters to summarize these results.

  2. Recent advances in modeling stellar interiors (u)

    SciTech Connect

    Guzik, Joyce Ann

    2010-01-01

    Advances in stellar interior modeling are being driven by new data from large-scale surveys and high-precision photometric and spectroscopic observations. Here we focus on single stars in normal evolutionary phases; we will not discuss the many advances in modeling star formation, interacting binaries, supernovae, or neutron stars. We review briefly: (1) updates to input physics of stellar models; (2) progress in two and three-dimensional evolution and hydrodynamic models; (3) insights from oscillation data used to infer stellar interior structure and validate model predictions (asteroseismology). We close by highlighting a few outstanding problems, e.g., the driving mechanisms for hybrid {gamma} Dor/{delta} Sct star pulsations, the cause of giant eruptions seen in luminous blue variables such as {eta} Car and P Cyg, and the solar abundance problem.

  3. Residual estuarine circulation in the Mandovi, a monsoonal estuary: A three-dimensional model study

    NASA Astrophysics Data System (ADS)

    Vijith, V.; Shetye, S. R.; Baetens, K.; Luyten, P.; Michael, G. S.

    2016-05-01

    Observations in the Mandovi estuary, located on the central west coast of India, have shown that the salinity field in this estuary is remarkably time-dependent and passes through all possible states of stratification (riverine, highly-stratified, partially-mixed and well-mixed) during a year as the runoff into the estuary varies from high values (∼1000 m3 s-1) in the wet season to negligible values (∼1 m3 s-1) at end of the dry season. The time-dependence is forced by the Indian Summer Monsoon (ISM) and hence the estuary is referred to as a monsoonal estuary. In this paper, we use a three-dimensional, open source, hydrodynamic, numerical model to reproduce the observed annual salinity field in the Mandovi. We then analyse the model results to define characteristics of residual estuarine circulation in the Mandovi. Our motivation to study this aspect of the Mandovi's dynamics is derived from the following three considerations. First, residual circulation is important to long-term evolution of an estuary; second, we need to understand how this circulation responds to strongly time-dependent runoff forcing experienced by a monsoonal estuary; and third, Mandovi is among the best studied estuaries that come under the influence of ISM, and has observations that can be used to validate the model. Our analysis shows that the residual estuarine circulation in the Mandovi shows four distinct phases during a year: a river like flow that is oriented downstream throughout the estuary; a salt-wedge type circulation, with flow into the estuary near the bottom and out of the estuary near the surface restricted close to the mouth of the estuary; circulation associated with a partially-mixed estuary; and, the circulation associated with a well-mixed estuary. Dimensional analysis of the field of residual circulation helped us to establish the link between strength of residual circulation at a location and magnitude of river runoff and rate of mixing at the location. We then

  4. Intermediate Models of Planetary Circulations in the Atmosphere and Ocean.

    NASA Astrophysics Data System (ADS)

    McWilliams, James C.; Gent, Peter R.

    1980-08-01

    Large-scale extratropical motions (with dimensions comparable to, or somewhat smaller than, the planetary radius) in the atmosphere and ocean exhibit a more restricted range of phenomena than are admissible in the primitive equations for fluid motions, and there have been many previous proposals for simpler, more phenomenologically limited models of these motions. The oldest and most successful of these is the quasi-geostrophic model. An extensive discussion is made of models intermediate between the quasi-geostrophic and primitive ones, some of which have been previously proposed [e.g., the balance equations (BE), where tendencies in the equation for the divergent component of velocity are neglected, or the geostrophic momentum approximation (GM), where ageostrophic accelerations are neglected relative to geostrophic ones] and some of which are derived here. Virtues of these models are assessed in the dual measure of nearly geostrophic momentum balance (i.e., small Rossby number) and approximate frontal structure (i.e., larger along-axis velocities and length scales than their cross-axis counterparts), since one or both of these circumstances is usually characteristic of planetary motions. Consideration is also given to various coordinate transformations, since they can yield simpler expressions for the governing differential equations of the intermediate models. In particular, a new set of coordinates is proposed, isentropic geostrophic coordinates,(IGC), which has the advantage of making implicit the advections due to ageostrophic horizontal and vertical velocities under various approximations. A generalization of quasi-geostrophy is made. named hypo-geostrophy (HG), which is an asymptotic approximation of one higher order accuracy in Rossby number. The governing equations are simplest in IGC for both HG and GM; we name the latter in these coordinates isentropic semi-geostrophy (ISG), in analogy to Hoskins' (1975) semi-geostrophy (SG). HG, GM and BE are, in our

  5. METC Gasifier Advanced Simulation (MGAS) model

    SciTech Connect

    Syamlal, M.; Bissett, L.A.

    1992-01-01

    Morgantown Energy Technology Center is developing an advanced moving-bed gasifier, which is the centerpiece of the Integrated Gasifier Combined-Cycle (IGCC) system, with the features of good efficiency, low cost, and minimal environmental impact. A mathematical model of the gasifier, the METC-Gasifier Advanced Simulation (MGAS) model, has been developed for the analysis and design of advanced gasifiers and other moving-bed gasifiers. This report contains the technical and the user manuals of the MGAS model. The MGAS model can describe the transient operation of coflow, counterflow, or fixed-bed gasifiers. It is a one-dimensional model and can simulate the addition and withdrawal of gas and solids at multiple locations in the bed, a feature essential for simulating beds with recycle. The model describes the reactor in terms of a gas phase and a solids (coal or char) phase. These phases may exist at different temperatures. The model considers several combustion, gasification, and initial stage reactions. The model consists of a set of mass balances for 14 gas species and three coal (pseudo-) species and energy balances for the gas and the solids phases. The resulting partial differential equations are solved using a finite difference technique.

  6. Evaluation of a stratiform cloud parameterization for general circulation models

    SciTech Connect

    Ghan, S.J.; Leung, L.R.; McCaa, J.

    1996-04-01

    To evaluate the relative importance of horizontal advection of cloud versus cloud formation within the grid cell of a single column model (SCM), we have performed a series of simulations with our SCM driven by a fixed vertical velocity and various rates of horizontal advection.

  7. A 1D model of the arterial circulation in mice.

    PubMed

    Aslanidou, Lydia; Trachet, Bram; Reymond, Philippe; Fraga-Silva, Rodrigo A; Segers, Patrick; Stergiopulos, Nikolaos

    2016-01-01

    At a time of growing concern over the ethics of animal experimentation, mouse models are still an indispensable source of insight into the cardiovascular system and its most frequent pathologies. Nevertheless, reference data on the murine cardiovascular anatomy and physiology are lacking. In this work, we developed and validated an in silico, one dimensional model of the murine systemic arterial tree consisting of 85 arterial segments. Detailed aortic dimensions were obtained in vivo from contrast-enhanced micro-computed tomography in 3 male, C57BL/6J anesthetized mice and 3 male ApoE(-/-) mice, all 12-weeks old. Physiological input data were gathered from a wide range of literature data. The integrated form of the Navier-Stokes equations was solved numerically to yield pressures and flows throughout the arterial network. The resulting model predictions have been validated against invasive pressure waveforms and non-invasive velocity and diameter waveforms that were measured in vivo on an independent set of 47 mice. In conclusion, we present a validated one-dimensional model of the anesthetized murine cardiovascular system that can serve as a versatile tool in the field of preclinical cardiovascular research.

  8. Advances in scientific balloon thermal modeling

    NASA Astrophysics Data System (ADS)

    Bohaboj, T.; Cathey, H.

    The National Aeronautics and Space Administration's Balloon Program Office has long acknowledged that the accurate modeling of balloon performance and flight prediction is dependant on how well the balloon is thermally modeled. This ongoing effort is focused on developing accurate balloon thermal models that can be used to quickly predict balloon temperatures and balloon performance. The ability to model parametric changes is also a driver for this effort. This paper will present the most recent advances made in this area. This research effort continues to utilize the ``Thermal Desktop'' addition to AUTO CAD for the modeling. Recent advances have been made by using this analytical tool. A number of analyses have been completed to test the applicability of this tool to the problem with very positive results. Progressively detailed models have been developed to explore the capabilities of the tool as well as to provide guidance in model formulation. A number of parametric studies have been completed. These studies have varied the shape of the structure, material properties, environmental inputs, and model geometry. These studies have concentrated on spherical ``proxy models'' for the initial development stages and then to transition to the natural shaped zero pressure and super pressure balloons. An assessment of required model resolution has also been determined. Model solutions have been cross checked with known solutions via hand calculations. The comparison of these cases will also be presented. One goal is to develop analysis guidelines and an approach for modeling balloons for both simple first order estimates and detailed full models. This paper presents the step by step advances made as part of this effort, capabilities, limitations, and the lessons learned. Also presented are the plans for further thermal modeling work.

  9. A Nd Isotopic Composition Modeling Approach of the Oceanic Thermohaline Circulation Change During LGM

    NASA Astrophysics Data System (ADS)

    Arsouze, T.; Dutay, J.; Lacan, F.; Jeandel, C.; Alkama, R.; Kageyama, M.; Piotrowski, A.

    2006-12-01

    The role of thermohaline circulation in climate change has been a matter of debate for a long time. Proxies of past ocean circulation such as δ13C or 231Pa/230Th suggest a relationship between North Atlantic Deep Water (NADW) strength and rapid climate change. Neodymium isotopic composition (Nd IC) is a quasi conservative geochemical tracer of water masses in the ocean interior and thus can be used as a proxy for NADW. Seawater Nd IC being recorded in marine sediments, this proxy is used to infer paleo-circulations on various time scales. Recent studies of Nd IC records, in the ferromanganese oxide components of a South Atlantic core, confirm the close relation between thermohaline circulation and North Atlantic climate changes through the last deglaciation (Piotrowski et al., 2004). Our purpose here is to model the Nd IC during the LGM and the Holocene with the Ocean Global Circulation Model NEMO, in the ORCA2 (2°) configuration. The explicit simulation of this proxy in the model allows to investigate and quantify the circulation change that corresponds to the Nd isotopic composition variation recorded in the sediments. We consider that the main source of Nd into the ocean is the interaction between water masses and continental margins (Boundary Exchange process; (Lacan and Jeandel, 2005). Boundary exchange is parameterized using a relaxing term (Arsouze et al., 2006). Simulated Nd IC distributions are evaluated by comparison with available records for the LGM and Holocene. References: Arsouze, T., Dutay, J.-C., Lacan, F. and Jeandel, C., 2006. Modeling the neodymium isotopic composition with a global ocean circulation model Chemical Geology, in press. Lacan, F. and Jeandel, C., 2005. Neodymium isotopes as a new tool for quantifying exchange fluxes at the continent - ocean interface. Earth and Planetary Science Letters, 232(3-4): 245-257. Piotrowski, A.M., Goldstein, S.L., Hemming, S.R. and Fairbanks, R.G., 2004. Intensification and variability of ocean

  10. Modeling of clouds and radiation for developing parameterizations for general circulation models. Annual report, 1994

    SciTech Connect

    1994-12-31

    We are using a hierarchy of numerical models of cirrus and stratus clouds and radiative transfer to improve the reliability of general circulation models. Our detailed cloud microphysical model includes all of the physical processes believed to control the lifecycle of liquid and ice clouds in the troposphere. In our one-dimensional cirrus studies, we find that the ice crystal number and size in cirrus clouds are not very sensitive to the number of condensation nuclei which are present. We have compared our three-dimensional meoscale simulations of cirrus clouds with radar, lidar satellite and other observations of water vapor and cloud fields and find that the model accurately predicts the characteristics of a cirrus cloud system. The model results reproduce several features detected by remote sensing (lidar and radar) measurements, including the appearance of the high cirrus cloud at about 15 UTC and the thickening of the cloud at 20 UTC. We have developed a new parameterizations for production of ice crystals based on the detailed one-dimensional cloud model, and are presently testing the parameterization in three-dimensional simulations of the FIRE-II November 26 case study. We have analyzed NWS radiosonde humidity data from FIRE and ARM and found errors, biases, and uncertainties in the conversion of the sensed resistance to humidity.

  11. A simple hydrologically based model of land surface water and energy fluxes for general circulation models

    NASA Technical Reports Server (NTRS)

    Liang, XU; Lettenmaier, Dennis P.; Wood, Eric F.; Burges, Stephen J.

    1994-01-01

    A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described. The new model is comprised of a two-layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max-Planck-Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long-term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment (FIFE) intensive field campaigns in the summer-fall of 1987 to validate the surface energy fluxes.

  12. Center for Advanced Modeling and Simulation Intern

    ScienceCinema

    Gertman, Vanessa

    2016-07-12

    Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

  13. Center for Advanced Modeling and Simulation Intern

    SciTech Connect

    Gertman, Vanessa

    2010-01-01

    Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

  14. An implementation of a barotropic quasigeostrophic model of ocean circulation on the MPP

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.; Fatoohi, R.

    1987-01-01

    The implementation on the Massively Parallel Processor (MPP) of a barotropic quasigeostrophic model of ocean circulation is discussed. The mathematical model, including scalings and boundary conditions is discussed. The numerical scheme, which uses compact differencing is also discussed. The implementation of this model on the MPP is then presented. Finally, some performance results are given and compared to results obtained using the VPS-32 and one processor of a CRAY-2.

  15. Development of the Circulation Control Flow Scheme Used in the NTF Semi-Span FAST-MAC Model

    NASA Technical Reports Server (NTRS)

    Jones, Gregory S.; Milholen, William E., II; Chan, David T.; Allan, Brian G.; Goodliff, Scott L.; Melton, Latunia P.; Anders, Scott G.; Carter, Melissa B.; Capone, Francis J.

    2013-01-01

    The application of a circulation control system for high Reynolds numbers was experimentally validated with the Fundamental Aerodynamic Subsonic Transonic Modular Active Control semi-span model in the NASA Langley National Transonic Facility. This model utilized four independent flow paths to modify the lift and thrust performance of a representative advanced transport type of wing. The design of the internal flow paths highlights the challenges associated with high Reynolds number testing in a cryogenic pressurized wind tunnel. Weight flow boundaries for the air delivery system were identified at mildly cryogenic conditions ranging from 0.1 to 10 lbm/sec. Results from the test verified system performance and identified solutions associated with the weight-flow metering system that are linked to internal perforated plates used to achieve flow uniformity at the jet exit.

  16. Observations and Modeling of the Transient General Circulation of the North Pacific Basin

    NASA Technical Reports Server (NTRS)

    McWilliams, James C.

    2000-01-01

    Because of recent progress in satellite altimetry and numerical modeling and the accumulation and archiving of long records of hydrographic and meteorological variables, it is becoming feasible to describe and understand the transient general circulation of the ocean (i.e., variations with spatial scales larger than a few hundred kilometers and time scales of seasonal and longer-beyond the mesoscale). We have carried out various studies in investigation of the transient general circulation of the Pacific Ocean from a coordinated analysis of satellite altimeter data, historical hydrographic gauge data, scatterometer wind observations, reanalyzed operational wind fields, and a variety of ocean circulation models. Broadly stated, our goal was to achieve a phenomenological catalogue of different possible types of large-scale, low-frequency variability, as a context for understanding the observational record. The approach is to identify the simplest possible model from which particular observed phenomena can be isolated and understood dynamically and then to determine how well these dynamical processes are represented in more complex Oceanic General Circulation Models (OGCMs). Research results have been obtained on Rossby wave propagation and transformation, oceanic intrinsic low-frequency variability, effects of surface gravity waves, pacific data analyses, OGCM formulation and developments, and OGCM simulations of forced variability.

  17. Variational Data Assimilative Modeling of the Gulf of Maine Circulation in Spring and Summer 2010

    PubMed Central

    Li, Yizhen; He, Ruoying; Chen, Ke; McGillicuddy, Dennis J.

    2016-01-01

    A data assimilative ocean circulation model is used to hindcast the Gulf of Maine (GOM) circulation in spring and summer 2010. Using the recently developed incremental strong constraint 4D Variational data assimilation algorithm, the model assimilates satellite sea surface temperature and in situ temperature and salinity profiles measured by expendable bathythermograph, Argo floats, and shipboard CTD casts. Validation against independent observations shows that the model skill is significantly improved after data assimilation. The data-assimilative model hindcast reproduces the temporal and spatial evolution of the ocean state, showing that a sea level depression southwest of the Scotian Shelf played a critical role in shaping the gulf-wide circulation. Heat budget analysis further demonstrates that both advection and surface heat flux contribute to temperature variability. The estimated time scale for coastal water to travel from the Scotian Shelf to the Jordan Basin is around 60 days, which is consistent with previous estimates based on in situ observations. Our study highlights the importance of resolving upstream and offshore forcing conditions in predicting the coastal circulation in the GOM. PMID:27239401

  18. Selected translated abstracts of Russian-language climate-change publications. 4: General circulation models

    SciTech Connect

    Burtis, M.D.; Razuvaev, V.N.; Sivachok, S.G.

    1996-10-01

    This report presents English-translated abstracts of important Russian-language literature concerning general circulation models as they relate to climate change. Into addition to the bibliographic citations and abstracts translated into English, this report presents the original citations and abstracts in Russian. Author and title indexes are included to assist the reader in locating abstracts of particular interest.

  19. Modelling circulating tumour cells for personalised survival prediction in metastatic breast cancer.

    PubMed

    Ascolani, Gianluca; Occhipinti, Annalisa; Liò, Pietro

    2015-05-01

    Ductal carcinoma is one of the most common cancers among women, and the main cause of death is the formation of metastases. The development of metastases is caused by cancer cells that migrate from the primary tumour site (the mammary duct) through the blood vessels and extravasating they initiate metastasis. Here, we propose a multi-compartment model which mimics the dynamics of tumoural cells in the mammary duct, in the circulatory system and in the bone. Through a branching process model, we describe the relation between the survival times and the four markers mainly involved in metastatic breast cancer (EPCAM, CD47, CD44 and MET). In particular, the model takes into account the gene expression profile of circulating tumour cells to predict personalised survival probability. We also include the administration of drugs as bisphosphonates, which reduce the formation of circulating tumour cells and their survival in the blood vessels, in order to analyse the dynamic changes induced by the therapy. We analyse the effects of circulating tumour cells on the progression of the disease providing a quantitative measure of the cell driver mutations needed for invading the bone tissue. Our model allows to design intervention scenarios that alter the patient-specific survival probability by modifying the populations of circulating tumour cells and it could be extended to other cancer metastasis dynamics.

  20. Simulation of the Low-Level-Jet by general circulation models

    SciTech Connect

    Ghan, S.J.

    1996-04-01

    To what degree is the low-level jet climatology and it`s impact on clouds and precipitation being captured by current general circulation models? It is hypothesised that a need for a pramaterization exists. This paper describes this parameterization need.

  1. Modelling Circulating Tumour Cells for Personalised Survival Prediction in Metastatic Breast Cancer

    PubMed Central

    2015-01-01

    Ductal carcinoma is one of the most common cancers among women, and the main cause of death is the formation of metastases. The development of metastases is caused by cancer cells that migrate from the primary tumour site (the mammary duct) through the blood vessels and extravasating they initiate metastasis. Here, we propose a multi-compartment model which mimics the dynamics of tumoural cells in the mammary duct, in the circulatory system and in the bone. Through a branching process model, we describe the relation between the survival times and the four markers mainly involved in metastatic breast cancer (EPCAM, CD47, CD44 and MET). In particular, the model takes into account the gene expression profile of circulating tumour cells to predict personalised survival probability. We also include the administration of drugs as bisphosphonates, which reduce the formation of circulating tumour cells and their survival in the blood vessels, in order to analyse the dynamic changes induced by the therapy. We analyse the effects of circulating tumour cells on the progression of the disease providing a quantitative measure of the cell driver mutations needed for invading the bone tissue. Our model allows to design intervention scenarios that alter the patient-specific survival probability by modifying the populations of circulating tumour cells and it could be extended to other cancer metastasis dynamics. PMID:25978366

  2. On the design of an interactive biosphere for the GLAS general circulation model

    NASA Technical Reports Server (NTRS)

    Mintz, Y.; Sellers, P. J.; Willmott, C. J.

    1983-01-01

    Improving the realism and accuracy of the GLAS general circulation model (by adding an interactive biosphere that will simulate the transfers of latent and sensible heat from land surface to atmosphere as functions of the atmospheric conditions and the morphology and physiology of the vegetation) is proposed.

  3. Documentation of a ground hydrology parameterization for use in the GISS atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Lin, J. D.; Aleano, J.; Bock, P.

    1978-01-01

    The moisture transport processes related to the earth's surface relevant to the ground circulation model GCM are presented. The GHM parametrizations considered are: (1) ground wetness and soil parameters; (2) precipitation; (3) evapotranspiration; (4) surface storage of snow and ice; and (5) runout. The computational aspects of the GHM using computer programs and flow charts are described.

  4. Tropospheric energy cascades in a global circulation model

    NASA Astrophysics Data System (ADS)

    Brune, Sebastian; Becker, Erich

    2010-05-01

    The global horizontal kinetic energy (KE) spectrum and its budget are analyzed using results from a mechanistic GCM. The model has a standard spectral dynamical core with very high vertikal resolution up to the middle stratosphere (T330/L100). As a turbulence model we combine the Smagorinsky scheme with an energy conserving hyperdiffusion that is applied for the very smallest resolved scales. The simulation confirms a slope of the KE spectrum close to -3 in the synoptic regime where the KE is dominated by vortical modes. Towards the mesoscales the spectrum flattens and assumes a slope close to -5/3. Here divergent modes become increasingly important and even dominate the KE. Our complete analysis of the sinks and sources in the spectral KE budget reveals the overall energy fluxes through the spectrum. For the upper troposphere, the change of KE due to horizontal advection is negative for large synoptic scales. It is positive for the planetary scale, as expected, and for the mesoscales as well. This implies that the mesoscales, which include the dynamical sources of tropospheric gravity waves, are in fact sustained by the energy injection at the baroclinic scale (forward energy cascade). We find an enstrophy cascade in accordance with 2D turbulence, but zero downscaling of energy due to the vortical modes alone. In other words, the forward energy cascade in the synoptic and mesoscale regime is solely due to the divergent modes and their nonlinear interaction with the vortical modes. This picture, derived form a mechanistic model, not only lends further evidence for a generally forward energy cascade in the upper tropospheric away from the baroclinic scale. It also extends the picture proposed earlier by Tung and Orlando: The transition from a -3 to a -5/3 slope in the tropospheric macroturbulence spectrum reflects the fact, that the energy cascade due to the horizontally divergent (3D) modes is hidden behind the (2D) enstrophy cascade in the synoptic regime but

  5. A January angular momentum balance in the OSU two-level atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Kim, J.-W.; Grady, W.

    1982-01-01

    The present investigation is concerned with an analysis of the atmospheric angular momentum balance, based on the simulation data of the Oregon State University two-level atmospheric general circulation model (AGCM). An attempt is also made to gain an understanding of the involved processes. Preliminary results on the angular momentum and mass balance in the AGCM are shown. The basic equations are examined, and questions of turbulent momentum transfer are investigated. The methods of analysis are discussed, taking into account time-averaged balance equations, time and longitude-averaged balance equations, mean meridional circulation, the mean meridional balance of relative angular momentum, and standing and transient components of motion.

  6. Atmospheric circulation modeling of super Earths and terrestrial extrasolar planets using the SPARC/MITgcm

    NASA Astrophysics Data System (ADS)

    Kataria, T.; Showman, A. P.; Haberle, R. M.; Marley, M. S.; Fortney, J. J.; Freedman, R. S.

    2013-12-01

    The field of exoplanets continues to be a booming field of research in astronomy and planetary science, with numerous ground-based (e.g., SuperWASP, HARPS-N and S) and space-based surveys (e.g., Kepler) that detect and characterize planets ranging from hot Jupiters, Jovian-sized planets orbiting less than 0.1 AU from their star, to super Earths and terrestrial exoplanets, planets that have masses equal to or less than 10 times that of Earth with a range of orbital distances. Atmospheric circulation modeling plays an important role in the characterization of these planets, helping to constrain observations that probe their atmospheres. These models have proven successful in understanding observations of transiting exoplanets (when the planet passes in front of the star along our line of sight) particularly when the planet is passing through secondary eclipse (when the planet's dayside is visible). In modeling super Earths and terrestrial exoplanets, we must consider not only planets with thick fluid envelopes, but also traditional terrestrial planets with solid surfaces and thinner atmospheres. To that end, we present results from studies investigating the atmospheric circulation of these classes of planets using the SPARC/MITgcm, a state-of-the-art model which couples the MIT General Circulation Model with a plane-parallel, two-stream, non-gray radiative transfer model. We will present results from two studies, the first focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth ground-based survey, and a second study which explores the circulation of terrestrial exoplanets orbiting M-dwarfs.

  7. The Early Jurassic climate: General circulation model simulations and the paleoclimate record

    SciTech Connect

    Chandler, M.A.

    1992-01-01

    This thesis presents the results of several general circulation model simulations of the Early Jurassic climate. The general circulation model employed was developed at the Goddard Institute for Space Studies while most paleoclimate data were provided by the Paleographic Atlas Project of the University of Chicago. The first chapter presents an Early Jurassic base simulation, which uses detailed reconstructions of paleogeography, vegetation, and sea surface temperature as boundary condition data sets. The resulting climatology reveals an Earth 5.2[degrees]C warmer, globally, than at present and a latitudinal temperature gradient dominated by high-latitude warming (+20[degrees]C) and little tropical change (+1[degrees]C). Comparisons show a good correlation between simulated results and paleoclimate data. Sensitivity experiments are used to investigate any model-data mismatches. Chapters two and three discuss two important aspects of Early Jurassic climate, continental aridity and global warming. Chapter two focuses on the hydrological capabilities of the general circulation model. The general circulation model's hydrologic diagnostics are evaluated, using the distribution of modern deserts and Early Jurassic paleoclimate data as validating constraints. A new method, based on general circulation model diagnostics and empirical formulae, is proposed for evaluating moisture balance. Chapter three investigates the cause of past global warming, concentrating on the role of increased ocean heat transport. Early Jurassic simulations show that increased ocean heat transports may have been a major factor in past climates. Increased ocean heat transports create latitudinal temperature gradients that closely approximate paleoclimate data and solve the problem of tropical overheating that results from elevated atmospheric carbon dioxide. Increased carbon dioxide cannot duplicate the Jurassic climate without also including increased ocean heat transports.

  8. The Venus nitric oxide night airglow - Model calculations based on the Venus Thermospheric General Circulation Model

    NASA Astrophysics Data System (ADS)

    Bougher, S. W.; Gerard, J. C.; Stewart, A. I. F.; Fessen, C. G.

    1990-05-01

    The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General Circulation Model (Dickinson et al., 1984), modified to include simple odd nitrogen chemistry. Results obtained for the solar maximum conditions indicate that the recently revised dark-disk average NO intensity at 198.0 nm, based on statistically averaged OUVS measurements, can be reproduced with minor modifications in chemical rate coefficients. The results imply a nightside hemispheric downward N flux of (2.5-3) x 10 to the 9th/sq cm sec, corresponding to the dayside net production of N atoms needed for transport.

  9. The Venus nitric oxide night airglow - Model calculations based on the Venus Thermospheric General Circulation Model

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; Gerard, J. C.; Stewart, A. I. F.; Fesen, C. G.

    1990-01-01

    The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General Circulation Model (Dickinson et al., 1984), modified to include simple odd nitrogen chemistry. Results obtained for the solar maximum conditions indicate that the recently revised dark-disk average NO intensity at 198.0 nm, based on statistically averaged OUVS measurements, can be reproduced with minor modifications in chemical rate coefficients. The results imply a nightside hemispheric downward N flux of (2.5-3) x 10 to the 9th/sq cm sec, corresponding to the dayside net production of N atoms needed for transport.

  10. The NASA/Ames Mars General Circulation Model: Model Improvements and Comparison with Observations

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Hollingsworth, J. L.; Colaprete, A.; Bridger, A. F. C.; McKay, C. P.; Murphy, J. R.; Schaeffer, J.; Freedman, R.; Fonda, Mark (Technical Monitor)

    2003-01-01

    For many years, the NASA/Ames Mars General Circulation Model (GCM) has been built around the UCLA B-grid dynamical core. An attached tracer transport scheme based on the aerosol microphysical model of Toon et al. (1988) provided a tool for studying dust storm transport and feedbacks (Murphy et al., 1995). While we still use a B-grid version of the model, the Ames group is now transitioning to the ARIES/GEOS Goddard C-grid dynamical core (Suarez and Takacs, 1995). The C-grid produces smoother fields when the model top is raised above 50 km, and has a built in transport scheme for an arbitrary number of tracers. All of our transport simulations are now carried out with the C-grid. We have also been updating our physics package. Several years ago we replaced our bulk boundary layer scheme with a level 2 type diffusive scheme, and added a multi-level soil model (Haberle et al., 2000). More recently we replaced our radiation code with a more generalized two-stream code that accounts for aerosol multiple scattering and gaseous absorption. This code gives us much more flexibility in choosing aerosol optical properties and radiatively active gases.

  11. On a sparse pressure-flow rate condensation of rigid circulation models.

    PubMed

    Schiavazzi, D E; Hsia, T Y; Marsden, A L

    2016-07-26

    Cardiovascular simulation has shown potential value in clinical decision-making, providing a framework to assess changes in hemodynamics produced by physiological and surgical alterations. State-of-the-art predictions are provided by deterministic multiscale numerical approaches coupling 3D finite element Navier Stokes simulations to lumped parameter circulation models governed by ODEs. Development of next-generation stochastic multiscale models whose parameters can be learned from available clinical data under uncertainty constitutes a research challenge made more difficult by the high computational cost typically associated with the solution of these models. We present a methodology for constructing reduced representations that condense the behavior of 3D anatomical models using outlet pressure-flow polynomial surrogates, based on multiscale model solutions spanning several heart cycles. Relevance vector machine regression is compared with maximum likelihood estimation, showing that sparse pressure/flow rate approximations offer superior performance in producing working surrogate models to be included in lumped circulation networks. Sensitivities of outlets flow rates are also quantified through a Sobol׳ decomposition of their total variance encoded in the orthogonal polynomial expansion. Finally, we show that augmented lumped parameter models including the proposed surrogates accurately reproduce the response of multiscale models they were derived from. In particular, results are presented for models of the coronary circulation with closed loop boundary conditions and the abdominal aorta with open loop boundary conditions. PMID:26671219

  12. Century-scale variability in a randomly forced, two-dimensional thermohaline ocean circulation model

    SciTech Connect

    Mysak, L.A.; Stocker, T.F.; Huang, F.

    1993-01-01

    The response of a two-dimensional thermohaline ocean circulation model to a random freshwater flux superimposed on the usual mixed boundary conditions for temperature and salinity is considered. It is shown that for a wide range of vertical and horizontal diffusivities and a box geometry that approximates the Atlantic Ocean, 200-300 yr period oscillations exist in the basic-state, interhemispheric meridional overturning circulation with deep convection in the north. These fluctuations can also be described in terms of propagating salinity anomalies which travel in the direction of the thermohaline flow. For large horizontal (K{sub h} = 15 x 10{sup 3} m{sup 2}/s) and small vertical (K{sub v}=0.5 x 10{sup -4}m{sup 2}/s) diffusivities, the random forcing also excites deca-millennial oscillations in the basic structure of the thermohaline circulation. In this case, the meridional circulation pattern slowly oscillates between three different stages: a large positive cell, with deep convection in the North Atlantic and upwelling in the south; a symmetric two-cell circulation, with deep convection in both polar regions and upwelling near the equator; and a large negative cell, with deep convection in the South Atlantic and upwelling in the north. Each state can persist for 0 (10 kyr).

  13. The puzzling Venusian polar atmospheric structure reproduced by a general circulation model.

    PubMed

    Ando, Hiroki; Sugimoto, Norihiko; Takagi, Masahiro; Kashimura, Hiroki; Imamura, Takeshi; Matsuda, Yoshihisa

    2016-01-01

    Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the midlatitudes at cloud-top levels (∼65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ∼60° latitude, which is a unique feature called 'cold collar' in the Venus atmosphere. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. Here we perform numerical simulations of the Venus atmospheric circulation using a general circulation model, and succeed in reproducing these puzzling features in close agreement with the observations. The cold collar and warm polar region are attributed to the residual mean meridional circulation enhanced by the thermal tide. The present results strongly suggest that the thermal tide is crucial for the structure of the Venus upper polar atmosphere at and above cloud levels. PMID:26832195

  14. The puzzling Venusian polar atmospheric structure reproduced by a general circulation model

    PubMed Central

    Ando, Hiroki; Sugimoto, Norihiko; Takagi, Masahiro; Kashimura, Hiroki; Imamura, Takeshi; Matsuda, Yoshihisa

    2016-01-01

    Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the midlatitudes at cloud-top levels (∼65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ∼60° latitude, which is a unique feature called ‘cold collar' in the Venus atmosphere. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. Here we perform numerical simulations of the Venus atmospheric circulation using a general circulation model, and succeed in reproducing these puzzling features in close agreement with the observations. The cold collar and warm polar region are attributed to the residual mean meridional circulation enhanced by the thermal tide. The present results strongly suggest that the thermal tide is crucial for the structure of the Venus upper polar atmosphere at and above cloud levels. PMID:26832195

  15. The Venus nitric oxide night airglow: Model calculations based on the Venus thermospheric general circulation model

    SciTech Connect

    Bougher, S.W. ); Gerard, J.C. ); Stewart, A.I.F.; Fesen, C.G. )

    1990-05-01

    Pioneer Venus (PV) orbiter ultraviolet spectrometer (OUVS) images of the nightside airglow in the (0, 1) {delta} band of nitric oxide showed a maximum whose average location was at 0200 local solar time just south of the equator. The average airglow brightness calculated over a portion of the nightside for 35 early orbits during the Pioneer Venus mission was a factor of 4 lower than this maximum. Recent recalibration of the PV OUVS instrument and reanalysis of the data yield new values for this statistical maximum (1.9 {plus minus} 0.6 kR) and the nightside average (400-460 {plus minus} 120 R) nightglow. This emission is produced by radiative recombination of N and O atoms transported from their source on the dayside to the nightside by the Venus thermospheric circulation. The Venus Thermospheric General Circulation Model (VTGCM) has been extended to incorporate odd nitrogen chemistry in order to examine the dynamical and chemical processes required to give rise to this emission. Its predictions of dayside N atom densities are also compared with empirical models based on Pioneer Venus measurements. Calculations are presented corresponding to OUVS data taken during solar maximum. The average production of nitrogen atoms on the dayside is about 9.0 {times} 10{sup 9} atoms cm{sup {minus}2} s{sup {minus}1}. Approximately 30% of this dayside source is required for transport to the nightside to yield the observed dark-disk nightglow features. The statistical location and intensity of the bright spot are well reproduced, as well as the altitude of the airglow layer. The importance of the large-scale transport and eddy diffusion on the global N({sup 4}S) distribution is also evaluated.

  16. On the validation of a code and a turbulence model appropriate to circulation control airfoils

    NASA Technical Reports Server (NTRS)

    Viegas, J. R.; Rubesin, M. W.; Maccormack, R. W.

    1988-01-01

    A computer code for calculating flow about a circulation control airfoil within a wind tunnel test section has been developed. This code is being validated for eventual use as an aid to design such airfoils. The concept of code validation being used is explained. The initial stages of the process have been accomplished. The present code has been applied to a low-subsonic, 2-D flow about a circulation control airfoil for which extensive data exist. Two basic turbulence models and variants thereof have been successfully introduced into the algorithm, the Baldwin-Lomax algebraic and the Jones-Launder two-equation models of turbulence. The variants include adding a history of the jet development for the algebraic model and adding streamwise curvature effects for both models. Numerical difficulties and difficulties in the validation process are discussed. Turbulence model and code improvements to proceed with the validation process are also discussed.

  17. Intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Potter, G. L.; Blanchet, J. P.; Boer, G. J.; Del Genio, A. D.

    1990-01-01

    The present study provides an intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models. This intercomparison uses sea surface temperature change as a surrogate for climate change. The interpretation of cloud-climate interactions is given special attention. A roughly threefold variation in one measure of global climate sensitivity is found among the 19 models. The important conclusion is that most of this variation is attributable to differences in the models' depiction of cloud feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as reliable climate predictors. It is further emphazied that cloud feedback is the consequence of all interacting physical and dynamical processes in a general circulation model. The result of these processes is to produce changes in temperature, moisture distribution, and clouds which are integrated into the radiative response termed cloud feedback.

  18. Combustion modeling in advanced gas turbine systems

    SciTech Connect

    Smoot, L.D.; Hedman, P.O.; Fletcher, T.H.; Brewster, B.S.; Kramer, S.K.

    1995-12-31

    Goal of DOE`s Advanced Turbine Systems program is to develop and commercialize ultra-high efficiency, environmentally superior, cost competitive gas turbine systems for base-load applications in utility, independent power producer, and industrial markets. Primary objective of the program here is to develop a comprehensive combustion model for advanced gas turbine combustion systems using natural gas (coal gasification or biomass fuels). The efforts included code evaluation (PCGC-3), coherent anti-Stokes Raman spectroscopy, laser Doppler anemometry, and laser-induced fluorescence.

  19. Validation of Atmospheric Dynamics (VADY) - representation of circulation types/dynamical modes in the decadal-prediction model system of MPI-ESM

    NASA Astrophysics Data System (ADS)

    Lang, Benjamin; Jacobeit, Jucundus; Beck, Christoph; Philipp, Andreas

    2016-04-01

    The climate research program "Medium-range Climate Predictions" (MiKlip), funded by the Federal Ministry of Education and Research in Germany (BMBF), has the aim to improve a climate model system (MPI-ESM) in such a way that it can provide reliable decadal predictions of climate, including extreme weather events. A substantial part of the development process is a comprehensive model validation. Within MiKlip, it includes comparisons of model simulations and observations in order to allow statements about the performance of the model and to give particular recommendations for the further development of the model. The research project "Validation of Atmospheric Dynamics" (VADY), conducted by the cooperation partners "Institute of Geography at the University of Augsburg" (IGUA) and the "German Aerospace Centre" (DLR), contributes to model validation within MiKlip with a special focus on atmospheric waves (DLR) and circulation dynamics (IGUA). Within the framework of VADY, DLR validates the representation of atmospheric waves on different levels and scales based on suitable activity indices (e.g. the so-called large-scale dynamical activity index (LDAI), which is a measure for the activity of planetary waves). The focus of IGUA is on the model validation with respect to the representation of atmospheric circulation types, dynamical modes and the teleconnectivity of the atmospheric circulation. The present contribution provides results of the model validation concerning circulation types/dynamical modes. Results are shown for both the frequency of occurrence and internal characteristics (e. g. persistence or intensity), and for different classification methods (e. g. based on PCA or clustering techniques). The representation of circulation types/dynamical modes will be compared for different generations of the MPI-ESM decadal-prediction model (baseline0, baseline1, prototype) in order to clarify both advances and limitations in the development of the model. Furthermore

  20. Circulation of carbon dioxide in the mantle: multiscale modeling

    NASA Astrophysics Data System (ADS)

    Morra, G.; Yuen, D. A.; Lee, S.

    2012-12-01

    Much speculation has been put forward on the quantity and nature of carbon reservoirs in the deep Earth, because of its involvement in the evolution of life at the surface and inside planetary interiors. Carbon penetrates into the Earth's mantle mostly during subduction of oceanic crust, which contains carbonate deposits [1], however the form that it assumes at lower mantle depths is scarcely understood [2], hampering our ability to estimate the amount of carbon in the entire mantle by orders of magnitude. We present simulations of spontaneous degassing of supercritical CO2 using in-house developed novel implementations of the Fast-Multipole Boundary Element Method suitable for modeling two-phase flow (here mantle mineral and free CO2 fluid) through disordered materials such as porous rocks. Because the mutual interaction of droplets immersed either in a fluid or a solid matrix and their weakening effect to the host rock alters the strength of the mantle rocks, at the large scale the fluid phases in the mantle may control the creeping of mantle rocks [3]. In particular our study focuses on the percolation of supercritical CO2, estimated through the solution of the Laplace equation in a porous system, stochastically generated through a series of random Karhunen-Loeve decomposition. The model outcome is employed to extract the transmissivity of supercritical fluids in the mantle from the lowest scale up to the mantle scale and in combination with the creeping flow of the convecting mantle. The emerging scenarios on the global carbon cycle are finally discussed. [1] Boulard, E., et al., New host for carbon in the deep Earth. Proceedings of the National Academy of Sciences, 2011. 108(13): p. 5184-5187. [2] Walter, M.J., et al., Deep Mantle Cycling of Oceanic Crust: Evidence from Diamonds and Their Mineral Inclusions. Science, 2011. 334(6052): p. 54-57. [3] Morra, G., et al., Ascent of Bubbles in Magma Conduits Using Boundary Elements and Particles. Procedia Computer

  1. Computer simulation of the cooling effect due to circulation in four geothermal well models

    SciTech Connect

    Duda, L.E.

    1984-11-01

    Computer calculations of wellbore transient temperatures, using the geothermal wellbore thermal simulator code GEOTEMP2, were made on four well models. The well models studied were from the Baca geothermal area, the East Mesa geothermal area, and a shallow and a deep well from the Salton Sea geothermal area. Calculations for one day of water circulation followed by one day of shut-in at flow rates of 100, 250, 500, and 1000 gpm were made to investigate the cooling effects produced by the circulation. Additional calculations were made using the Baca and Salton Sea well models. In the former, the effect on the cooling due to different soil thermal conductivity values and different circulating fluids (a high viscosity mud and air) were investigated. In the latter, the number of casings in the wellbore and the diameter of the tubing were notified. Plots of the calculated temperatures as a function of circulation and shut-in time and depth are given for each case.

  2. On the relevance of tidal forcing in modelling the Mediterranean thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Sannino, G.; Carillo, A.; Pisacane, G.; Naranjo, C.

    2015-05-01

    The four dominant constituents of the semi-diurnal and diurnal tides have been implemented in a regional eddy-resolving Mediterranean version of the Massachusetts Institute of Technology general circulation model to assess the role played by tides on the simulated Mediterranean thermohaline circulation. To this aim we have compared two 10-year hindcast simulations differing only for the inclusion/omission of tidal forcing. Following the recent recommendations suggested by Sannino et al. (2014) both simulations use the same model having a substantial increment of the horizontal resolution in the region of the Strait of Gibraltar. The results suggest that application of explicit tidal forcing in a Mediterranean model has non negligible effects on the simulated circulation in addition to the expected intensification of local mixing processes. The western basin exhibits an immediate response to the different characteristics of the inflowing AW observable in the modified deep water convection processes in the Gulf of Lion. The inclusion of tidal forcing also induces changes in the intermediate circulation of the Tyrrhenian Sea bringing to a better representation of local structures and a reinforcement of the global thermohaline cell. LIW dispersal paths in the eastern basin are also affected by tides.

  3. Effects of implementing the Simple Biosphere Model in a general circulation model

    NASA Technical Reports Server (NTRS)

    Sato, N.; Sellers, P. J.; Randall, D. A.; Schneider, E. K.; Shukla, J.

    1989-01-01

    The Simple Biosphere Model (SiB) of Sellers et al., was designed to simulate the interactions between the earth's land surface and the atmosphere by treating the vegetation explicitly and realistically, thereby incorporating the biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. This paper describes the steps taken to implement SiB in a modified version of the National Meteorological Center's global spectral general circulation model (GCM) and explores the impact of the implementation on the simulated land surface fluxes and near-surface meteorological conditions. The coupled model (SiB-GCM) was used to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter simulations for comparison. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM, produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in a much deeper daytime planetary boundary layer and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream was slightly weakened in the SiB-GCM relative to the Ctl-GCM results and analyses made from observations.

  4. Maturity Model for Advancing Smart Grid Interoperability

    SciTech Connect

    Knight, Mark; Widergren, Steven E.; Mater, J.; Montgomery, Austin

    2013-10-28

    Abstract—Interoperability is about the properties of devices and systems to connect and work properly. Advancing interoperability eases integration and maintenance of the resulting interconnection. This leads to faster integration, lower labor and component costs, predictability of projects and the resulting performance, and evolutionary paths for upgrade. When specifications are shared and standardized, competition and novel solutions can bring new value streams to the community of stakeholders involved. Advancing interoperability involves reaching agreement for how things join at their interfaces. The quality of the agreements and the alignment of parties involved in the agreement present challenges that are best met with process improvement techniques. The GridWise® Architecture Council (GWAC) sponsored by the United States Department of Energy is supporting an effort to use concepts from capability maturity models used in the software industry to advance interoperability of smart grid technology. An interoperability maturity model has been drafted and experience is being gained through trials on various types of projects and community efforts. This paper describes the value and objectives of maturity models, the nature of the interoperability maturity model and how it compares with other maturity models, and experiences gained with its use.

  5. Circulating Tumour Cells as an Independent Prognostic Factor in Patients with Advanced Oesophageal Squamous Cell Carcinoma Undergoing Chemoradiotherapy.

    PubMed

    Su, Po-Jung; Wu, Min-Hsien; Wang, Hung-Ming; Lee, Chia-Lin; Huang, Wen-Kuan; Wu, Chiao-En; Chang, Hsien-Kun; Chao, Yin-Kai; Tseng, Chen-Kan; Chiu, Tzu-Keng; Lin, Nina Ming-Jung; Ye, Siou-Ru; Lee, Jane Ying-Chieh; Hsieh, Chia-Hsun

    2016-01-01

    The role of circulating tumour cells (CTCs) in advanced oesophageal cancer (EC) patients undergoing concurrent chemoradiotherapy (CCRT) remains uncertain. A negative selection protocol plus flow cytometry was validated to efficiently identify CTCs. The CTC number was calculated and analysed for survival impact. The protocol's efficacy in CTC identification was validated with a recovery rate of 44.6 ± 9.1% and a coefficient of variation of 20.4%. Fifty-seven patients and 20 healthy donors were enrolled. Initial staging, first response to CRT, and surgery after CRT were prognostic for overall survival, with P values of <0.0001, <0.0001, and <0.0001, respectively. The CTC number of EC patients is significantly higher (P = 0.04) than that of healthy donors. Multivariate analysis for disease-specific progression-free survival showed that surgery after response to CCRT, initial stage, and CTC number (≥21.0 cells/mL) played independent prognostic roles. For overall survival, surgery after CCRT, performance status, initial stage, and CTC number were significant independent prognostic factors. In conclusion, a negative selection plus flow cytometry protocol efficiently detected CTCs. The CTC number before CCRT was an independent prognostic factor in patients with unresectable oesophageal squamous cell carcinoma. Further large-scale prospective studies for validation are warranted. PMID:27530152

  6. Circulating Tumour Cells as an Independent Prognostic Factor in Patients with Advanced Oesophageal Squamous Cell Carcinoma Undergoing Chemoradiotherapy

    PubMed Central

    Su, Po-Jung; Wu, Min-Hsien; Wang, Hung-Ming; Lee, Chia-Lin; Huang, Wen-Kuan; Wu, Chiao-En; Chang, Hsien-Kun; Chao, Yin-Kai; Tseng, Chen-Kan; Chiu, Tzu-Keng; Lin, Nina Ming-Jung; Ye, Siou-Ru; Lee, Jane Ying-Chieh; Hsieh, Chia-Hsun

    2016-01-01

    The role of circulating tumour cells (CTCs) in advanced oesophageal cancer (EC) patients undergoing concurrent chemoradiotherapy (CCRT) remains uncertain. A negative selection protocol plus flow cytometry was validated to efficiently identify CTCs. The CTC number was calculated and analysed for survival impact. The protocol’s efficacy in CTC identification was validated with a recovery rate of 44.6 ± 9.1% and a coefficient of variation of 20.4%. Fifty-seven patients and 20 healthy donors were enrolled. Initial staging, first response to CRT, and surgery after CRT were prognostic for overall survival, with P values of <0.0001, <0.0001, and <0.0001, respectively. The CTC number of EC patients is significantly higher (P = 0.04) than that of healthy donors. Multivariate analysis for disease-specific progression-free survival showed that surgery after response to CCRT, initial stage, and CTC number (≥21.0 cells/mL) played independent prognostic roles. For overall survival, surgery after CCRT, performance status, initial stage, and CTC number were significant independent prognostic factors. In conclusion, a negative selection plus flow cytometry protocol efficiently detected CTCs. The CTC number before CCRT was an independent prognostic factor in patients with unresectable oesophageal squamous cell carcinoma. Further large-scale prospective studies for validation are warranted. PMID:27530152

  7. Advancing Material Models for Automotive Forming Simulations

    NASA Astrophysics Data System (ADS)

    Vegter, H.; An, Y.; ten Horn, C. H. L. J.; Atzema, E. H.; Roelofsen, M. E.

    2005-08-01

    Simulations in automotive industry need more advanced material models to achieve highly reliable forming and springback predictions. Conventional material models implemented in the FEM-simulation models are not capable to describe the plastic material behaviour during monotonic strain paths with sufficient accuracy. Recently, ESI and Corus co-operate on the implementation of an advanced material model in the FEM-code PAMSTAMP 2G. This applies to the strain hardening model, the influence of strain rate, and the description of the yield locus in these models. A subsequent challenge is the description of the material after a change of strain path. The use of advanced high strength steels in the automotive industry requires a description of plastic material behaviour of multiphase steels. The simplest variant is dual phase steel consisting of a ferritic and a martensitic phase. Multiphase materials also contain a bainitic phase in addition to the ferritic and martensitic phase. More physical descriptions of strain hardening than simple fitted Ludwik/Nadai curves are necessary. Methods to predict plastic behaviour of single-phase materials use a simple dislocation interaction model based on the formed cells structures only. At Corus, a new method is proposed to predict plastic behaviour of multiphase materials have to take hard phases into account, which deform less easily. The resulting deformation gradients create geometrically necessary dislocations. Additional micro-structural information such as morphology and size of hard phase particles or grains is necessary to derive the strain hardening models for this type of materials. Measurements available from the Numisheet benchmarks allow these models to be validated. At Corus, additional measured values are available from cross-die tests. This laboratory test can attain critical deformations by large variations in blank size and processing conditions. The tests are a powerful tool in optimising forming simulations

  8. Mercury exosphere I. Global circulation model of its sodium component

    NASA Astrophysics Data System (ADS)

    Leblanc, Francois; Johnson, R. E.

    2010-10-01

    Our understanding of Mercury's sodium exosphere has improved considerably in the last 5 years thanks to new observations (Schleicher, H., Wiedemann, G., Wöhl, H., Berkefeld, T., Soltau, D. [2004]. Astron. Astrophys. 425, 1119-1124) and to the publication of a summary of the large set of ground based observations (Potter, A.E., Killen, R.M., Morgan, T.H. [2007]. Icarus 186, 571-580; Potter, A.E., Killen, R.M. [2008]. Icarus 194, 1-12; Potter et al., 2009). In particular, the non-uniformity in longitude of the dayside sodium distribution (the dawn/dusk asymmetry) has now been clearly observed. This suggests that Mercury's sodium exosphere is partly driven by a global day to nightside migration of the volatiles. One of the key questions remaining is the nature of the prevailing sodium ejection mechanisms. Because of the uncertain parameters for each ejection mechanisms, solving this problem has been difficult as indicated by the numerous papers over the last 15 years with very different conclusions. In addition, the variation of the size and of the spatial distribution of the surface reservoir (Leblanc, F., Johnson, R.E. [2003]. Icarus 164, 261-281) varies with distance from the Sun affecting the importance of each ejection mechanism on Mercury's orbital position. We here present an updated version of the Leblanc and Johnson (Leblanc, F., Johnson, R.E. [2003]. Icarus 164, 261-281) model. We take into account the two populations of sodium in the surface reservoir (Hunten, D.M., Morgan, T.M., Shemansky, D.M. [1988]. The Mercury atmosphere. In: Vilas, F., Chapman, C., Matthews, M. (Eds.), Mercury. University of Arizona Press, Tucson, pp. 562-612), one ambient population (physisorbed in the regolith with low binding energy) and one source population (chemisorbed coming from grain interior or from fresh dust brought to the surface and characterized by a higher binding energy). We also incorporate a better description of the solar wind sputtering variation with solar

  9. The Probability of the Collapse of the Thermohaline Circulation in an Intermediate Complexity Model

    NASA Astrophysics Data System (ADS)

    Challenor, P.; Hankin, R.; Marsh, R.

    2005-12-01

    If the thermohaline circulation were to collapse we could see very rapid climate changes, with North West Europe becoming much cooler and widespread impacts across the globe. The risk of such an event has two aspects: the first is the impact of a collapse in the circulation and the second is the probability that it will happen. In this paper we look at latter problem. In particular we investigate the probability that the thermohaline circulation will collapse by the end of the century. To calculate the probability of thermohaline collapse we use a Monte Carl method. We simulate from a climate model with uncertain parameters and estimate the probability from the number of times the model collapses compared to the number of runs. We use an intermediate complexity climate model, C-GOLDSTEIN, which includes a 3-d ocean, an energy balance atmosphere and, in the version we use, a parameterised carbon cycle. Although C-GOLDSTEIN runs quickly for a climate model it is still too slow to allow the thousands of runs needed for the Monte Carlo calculations. We therefore build an emulator of the model. An emulator is a statistical approximation to the full climate model that gives an estimate of the model output and an uncertainty measure. We use a Gaussian process as our emulator. A limited number of model runs are used to build the emulator which is then used for the simulations. We produce estimates of the probability of the collapse of the thermohaline circulation corresponding to the indicative SRES emission scenarios: A1, A1FI, A1T, A2, B1 and B2.

  10. Land surface hydrology parameterization for atmospheric general circulation models including subgrid scale spatial variability

    NASA Technical Reports Server (NTRS)

    Entekhabi, D.; Eagleson, P. S.

    1989-01-01

    Parameterizations are developed for the representation of subgrid hydrologic processes in atmospheric general circulation models. Reasonable a priori probability density functions of the spatial variability of soil moisture and of precipitation are introduced. These are used in conjunction with the deterministic equations describing basic soil moisture physics to derive expressions for the hydrologic processes that include subgrid scale variation in parameters. The major model sensitivities to soil type and to climatic forcing are explored.

  11. A Modeling Study of Hydrodynamic Circulation in a Fjord of the Pacific Northwest

    SciTech Connect

    Wang, Taiping; Yang, Zhaoqing

    2012-10-01

    Increased eutrophication and degraded water quality in estuarine and coastal waters have been a worldwide environmental concern. While it is commonly accepted that anthropogenic impact plays a major role in many emerging water quality issues, natural conditions such as restricted water circulations controlled by geometry may also substantially contribute to unfavorable water quality in certain ecosystems. To elucidate the contributions from different factors, a hydrodynamic-water quality model that integrates both physical transport and pollutant loadings is particularly warranted. A preliminary modeling study using the Environmental Fluid Dynamic Code (EFDC) is conducted to investigate hydrodynamic circulation and low dissolved oxygen (DO) in Hood Canal, a representative fjord in the U.S. Pacific Northwest. Because the water quality modeling work is still ongoing, this paper focuses on the progress in hydrodynamic modeling component. The hydrodynamic model has been set up using the publicly available forcing data and was calibrated against field observations or NOAA predictions for tidal elevation, current, salinity and temperature. The calibrated model was also used to estimate physical transport timescales such as residence time in the estuary. The preliminary model results demonstrate that the EFDC Hood Canal model is capable of capturing the general circulation patterns in Hood Canal, including weak tidal current and strong vertical stratification. The long residence time (i.e., on the order of 100 days for the entire estuary) also indicates that restricted water circulation could contribute to low DO in the estuary and also makes the system especially susceptible to anthropogenic disturbance, such as excess nutrient input.

  12. Advances in Computationally Modeling Human Oral Bioavailability

    PubMed Central

    Wang, Junmei; Hou, Tingjun

    2015-01-01

    Although significant progress has been made in experimental high throughput screening (HTS) of ADME (absorption, distribution, metabolism, excretion) and pharmacokinetic properties, the ADME and Toxicity (ADME-Tox) in silico modeling is still indispensable in drug discovery as it can guide us to wisely select drug candidates prior to expensive ADME screenings and clinical trials. Compared to other ADME-Tox properties, human oral bioavailability (HOBA) is particularly important but extremely difficult to predict. In this paper, the advances in human oral bioavailability modeling will be reviewed. Moreover, our deep insight on how to construct more accurate and reliable HOBA QSAR and classification models will also discussed. PMID:25582307

  13. Ross ice shelf cavity circulation, residence time, and melting: Results from a model of oceanic chlorofluorocarbons

    NASA Astrophysics Data System (ADS)

    Reddy, Tasha E.; Holland, David M.; Arrigo, Kevin R.

    2010-04-01

    Despite their harmful effects in the upper atmosphere, anthropogenic chlorofluorocarbons dissolved in seawater are extremely useful for studying ocean circulation and ventilation, particularly in remote locations. Because they behave as a passive tracer in seawater, and their atmospheric concentrations are well-mixed, well-known, and have changed over time, they are ideal for gaining insight into the oceanographic characteristics of the isolated cavities found under Antarctic ice shelves, where direct observations are difficult to obtain. Here we present results from a modeling study of air-sea chlorofluorocarbon exchange and ocean circulation in the Ross Sea, Antarctica. We compare our model estimates of oceanic CFC-12 concentrations along an ice shelf edge transect to field data collected during three cruises spanning 16 yr. Our model produces chlorofluorocarbon concentrations that are quite similar to those measured in the field, both in magnitude and distribution, showing high values near the surface, decreasing with depth, and increasing over time. After validating modeled circulation and air-sea gas exchange through comparison of modeled temperature, salinity, and chlorofluorocarbons with field data, we estimate that the residence time of water in the Ross Ice Shelf cavity is approximately 2.2 yr and that basal melt rates for the ice shelf average 10 cm yr -1. The model predicts a seasonal signature to basal melting, with highest melt rates in the spring and also the fall.

  14. Advanced Technology System Scheduling Governance Model

    SciTech Connect

    Ang, Jim; Carnes, Brian; Hoang, Thuc; Vigil, Manuel

    2015-06-11

    In the fall of 2005, the Advanced Simulation and Computing (ASC) Program appointed a team to formulate a governance model for allocating resources and scheduling the stockpile stewardship workload on ASC capability systems. This update to the original document takes into account the new technical challenges and roles for advanced technology (AT) systems and the new ASC Program workload categories that must be supported. The goal of this updated model is to effectively allocate and schedule AT computing resources among all three National Nuclear Security Administration (NNSA) laboratories for weapons deliverables that merit priority on this class of resource. The process outlined below describes how proposed work can be evaluated and approved for resource allocations while preserving high effective utilization of the systems. This approach will provide the broadest possible benefit to the Stockpile Stewardship Program (SSP).

  15. Early warning signals of Atlantic Meridional Overturning Circulation collapse in a fully coupled climate model

    PubMed Central

    Boulton, Chris A.; Allison, Lesley C.; Lenton, Timothy M.

    2014-01-01

    The Atlantic Meridional Overturning Circulation (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general circulation model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached. PMID:25482065

  16. Calculation of a residual mean meridional circulation for a zonal-mean tracer transport model

    SciTech Connect

    Choi, W.K.; Rotman, D.A.; Wuebbles, D.J.

    1995-04-01

    Because of their computational advantages, zonally-averaged chemical-radiative-transport models are widely used to investigate the distribution of chemical species and their change due to the anthropogenic chemicals in the lower and middle atmosphere. In general, the Lagrangian-mean formulation would be ideal to treat transport due to the zonal mean circulation and eddies. However, the Lagrangian formulation is difficult to use in practical applications. The most widely-used formulation for treating global atmospheric dynamics in two-dimensional models is the transformed Eulerian mean (TEM) equations. The residual mean meridional circulation (RMMC) in the TEM system is used to advect tracers. In this study, the authors describe possible solution techniques for obtaining the RMMC in the LLNL two-dimensional chemical-radiative-transport model. In the first section, the formulation will be described. In sections 3 and 4, possible solution procedures will be described for a diagnostic and prognostic case, respectively.

  17. Early warning signals of Atlantic Meridional Overturning Circulation collapse in a fully coupled climate model.

    PubMed

    Boulton, Chris A; Allison, Lesley C; Lenton, Timothy M

    2014-01-01

    The Atlantic Meridional Overturning Circulation (AMOC) exhibits two stable states in models of varying complexity. Shifts between alternative AMOC states are thought to have played a role in past abrupt climate changes, but the proximity of the climate system to a threshold for future AMOC collapse is unknown. Generic early warning signals of critical slowing down before AMOC collapse have been found in climate models of low and intermediate complexity. Here we show that early warning signals of AMOC collapse are present in a fully coupled atmosphere-ocean general circulation model, subject to a freshwater hosing experiment. The statistical significance of signals of increasing lag-1 autocorrelation and variance vary with latitude. They give up to 250 years warning before AMOC collapse, after ~550 years of monitoring. Future work is needed to clarify suggested dynamical mechanisms driving critical slowing down as the AMOC collapse is approached. PMID:25482065

  18. 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.

  19. 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.

  20. Seasonal variation of Titan's atmospheric structure simulated by a general circulation model.

    PubMed

    Tokano, T; Neubauer, F M; Laube, M; McKay, C P

    1999-01-01

    The seasonal variation of Titan's atmospheric structure with emphasis on the stratosphere is simulated by a three-dimensional general circulation model. The model includes the transport of haze particles by the circulation. The likely pattern of meridional circulation is reconstructed by a comparison of simulated and observed haze and temperature distribution. The GCM produces a weak zonal circulation with a small latitudinal temperature gradient, in conflict with observation. The direct reason is found to be the excessive meridional circulation. Under uniformly distributed opacity sources, the model predicts a pair of symmetric Hadley cells near the equinox and a single global cell with the rising branch in the summer hemisphere below about z = 230 km and a thermally indirect cell above the direct cell near the solstice. The interhemispheric circulation transports haze particles from the summer to the winter hemisphere, causing a maximum haze opacity contrast near the solstice and a smaller contrast near the equinox, contrary to observation. On the other, if the GCM is run under modified cooling rate in order to account for the enhancement in nitrites and some hydrocarbons in the northern hemisphere near the vernal equinox, the meridional cell at the equinox becomes a single cell with rising motions in the autumn hemisphere. A more realistic haze opacity distribution can be reproduced at the equinox. However, a pure transport effect (without particle growth by microphysics, etc.) would not be able to cause the observed discontinuity of the global haze opacity distribution at any location. The stratospheric temperature asymmetry can be explained by a combination of asymmetric radiative heating rates and adiabatic heating due to vertical motion within the thermally indirect cell. A seasonal variation of haze particle number density is unlikely to be responsible for this asymmetry. It is likely that a thermally indirect cell covers the upper portion of the main haze

  1. Advanced glycation end products and their circulating receptors predict cardiovascular disease mortality in older community-dwelling women

    PubMed Central

    Semba, Richard D.; Ferrucci, Luigi; Sun, Kai; Beck, Justine; Dalal, Mansi; Varadhan, Ravi; Walston, Jeremy; Guralnik, Jack M.; Fried, Linda P.

    2008-01-01

    Objective To characterize the relationship between advanced glycation end products (AGEs) and circulating receptors for AGEs (RAGE) with cardiovascular disease mortality. Methods The relationships between serum AGEs, total RAGE (sRAGE), and endogenous secretory RAGE (esRAGE), and mortality were characterized in 559 community-dwelling women, ≥65 years, in Baltimore, Maryland. Results During 4.5 years of follow-up, 123 (22%) women died, of whom 54 died with cardiovascular disease. The measure of serum AGEs was carboxymethyl-lysine (CML), a dominant AGE. Serum CML predicted cardiovascular disease mortality (Hazards Ratio [H.R.] for highest versus lower three quartiles 1.94, 95% Confidence Interval [C.I.] 1.08-3.48, P = 0.026), after adjusting for age, race, body mass index, and renal insufficiency. Serum sRAGE (ng/mL) and esRAGE (ng/mL) predicted cardiovascular disease mortality (H.R. per 1 Standard Deviation [S.D.] 1.27, 95% C.I. 0.98-1.65, P = 0.07; H.R. 1.28, 95% C.I. 1.02-1.63, P = 0.03), after adjusting for the same covariates. Among non-diabetic women, serum CML, sRAGE, and esRAGE, respectively, predicted cardiovascular disease mortality (H.R. for highest versus lower three quartiles, 2.29, 95% C.I. 1.21-4.34, P = 0.01; H.R. per 1 S.D., 1.24, 95% C.I. 0.92-1.65, P = 0.16; H.R. per 1 S.D. 1.45, 95% C.I. 1.08-1.93, P = 0.01), after adjusting for the same covariates. Conclusions High circulating AGEs and RAGE predict cardiovascular disease mortality among older community-dwelling women. AGEs are a potential target for interventions, as serum AGEs can be lowered by change in dietary pattern and pharmacological treatment. PMID:19448391

  2. Combustion modeling in advanced gas turbine systems

    SciTech Connect

    Smoot, L.D.; Hedman, P.O.; Fletcher, T.H.

    1995-10-01

    The goal of the U.S. Department of Energy`s Advanced Turbine Systems (ATS) program is to help develop and commercialize ultra-high efficiency, environmentally superior, and cost competitive gas turbine systems for base-load applications in the utility, independent power producer, and industrial markets. Combustion modeling, including emission characteristics, has been identified as a needed, high-priority technology by key professionals in the gas turbine industry.

  3. A simple-physics global circulation model for Venus: Sensitivity assessments of atmospheric superrotation

    NASA Astrophysics Data System (ADS)

    Hollingsworth, J. L.; Young, R. E.; Schubert, G.; Covey, C.; Grossman, A. S.

    2007-03-01

    A 3D global circulation model is adapted to the atmosphere of Venus to explore the nature of the planet's atmospheric superrotation. The model employs the full meteorological primitive equations and simplified forms for diabatic and other nonconservative forcings. It is therefore economical for performing very long simulations. To assess circulation equilibration and the occurrence of atmospheric superrotation, the climate model is run for 10,000-20,000 day integrations at 4° × 5° latitude-longitude horizontal resolution, and 56 vertical levels (denoted L56). The sensitivity of these simulations to imposed Venus-like diabatic heating rates, momentum dissipation rates, and various other key parameters (e.g., near-surface momentum drag), in addition to model configuration (e.g., low versus high vertical domain and number of atmospheric levels), is examined. We find equatorial superrotation in several of our numerical experiments, but the magnitude of superrotation is often less than observed. Further, the meridional structure of the mean zonal overturning (i.e., Hadley circulation) can consist of numerous cells which are symmetric about the equator and whose depth scale appears sensitive to the number of vertical layers imposed in the model atmosphere. We find that when realistic diabatic heating is imposed in the lowest several scales heights, only extremely weak atmospheric superrotation results.

  4. Advanced Atmospheric Modeling for Emergency Response.

    NASA Astrophysics Data System (ADS)

    Fast, Jerome D.; O'Steen, B. Lance; Addis, Robert P.

    1995-03-01

    Atmospheric transport and diffusion models are an important part of emergency response systems for industrial facilities that have the potential to release significant quantities of toxic or radioactive material into the atmosphere. An advanced atmospheric transport and diffusion modeling system for emergency response and environmental applications, based upon a three-dimensional mesoscale model, has been developed for the U.S. Department of Energy's Savannah River Site so that complex, time-dependent flow fields not explicitly measured can be routinely simulated. To overcome some of the current computational demands of mesoscale models, two operational procedures for the advanced atmospheric transport and diffusion modeling system are described including 1) a semiprognostic calculation to produce high-resolution wind fields for local pollutant transport in the vicinity of the Savannah River Site and 2) a fully prognostic calculation to produce a regional wind field encompassing the southeastern United States for larger-scale pollutant problems. Local and regional observations and large-scale model output are used by the mesoscale model for the initial conditions, lateral boundary conditions, and four-dimensional data assimilation procedure. This paper describes the current status of the modeling system and presents two case studies demonstrating the capabilities of both modes of operation. While the results from the case studies shown in this paper are preliminary and certainly not definitive, they do suggest that the mesoscale model has the potential for improving the prognostic capabilities of atmospheric modeling for emergency response at the Savannah River Site. Long-term model evaluation will be required to determine under what conditions significant forecast errors exist.

  5. A computational model of the fetal circulation to quantify blood redistribution in intrauterine growth restriction.

    PubMed

    Garcia-Canadilla, Patricia; Rudenick, Paula A; Crispi, Fatima; Cruz-Lemini, Monica; Palau, Georgina; Camara, Oscar; Gratacos, Eduard; Bijnens, Bart H; Bijens, Bart H

    2014-06-01

    Intrauterine growth restriction (IUGR) due to placental insufficiency is associated with blood flow redistribution in order to maintain delivery of oxygenated blood to the brain. Given that, in the fetus the aortic isthmus (AoI) is a key arterial connection between the cerebral and placental circulations, quantifying AoI blood flow has been proposed to assess this brain sparing effect in clinical practice. While numerous clinical studies have studied this parameter, fundamental understanding of its determinant factors and its quantitative relation with other aspects of haemodynamic remodeling has been limited. Computational models of the cardiovascular circulation have been proposed for exactly this purpose since they allow both for studying the contributions from isolated parameters as well as estimating properties that cannot be directly assessed from clinical measurements. Therefore, a computational model of the fetal circulation was developed, including the key elements related to fetal blood redistribution and using measured cardiac outflow profiles to allow personalization. The model was first calibrated using patient-specific Doppler data from a healthy fetus. Next, in order to understand the contributions of the main parameters determining blood redistribution, AoI and middle cerebral artery (MCA) flow changes were studied by variation of cerebral and peripheral-placental resistances. Finally, to study how this affects an individual fetus, the model was fitted to three IUGR cases with different degrees of severity. In conclusion, the proposed computational model provides a good approximation to assess blood flow changes in the fetal circulation. The results support that while MCA flow is mainly determined by a fall in brain resistance, the AoI is influenced by a balance between increased peripheral-placental and decreased cerebral resistances. Personalizing the model allows for quantifying the balance between cerebral and peripheral-placental remodeling

  6. A Computational Model of the Fetal Circulation to Quantify Blood Redistribution in Intrauterine Growth Restriction

    PubMed Central

    Garcia-Canadilla, Patricia; Rudenick, Paula A.; Crispi, Fatima; Cruz-Lemini, Monica; Palau, Georgina; Camara, Oscar; Gratacos, Eduard; Bijens, Bart H.

    2014-01-01

    Intrauterine growth restriction (IUGR) due to placental insufficiency is associated with blood flow redistribution in order to maintain delivery of oxygenated blood to the brain. Given that, in the fetus the aortic isthmus (AoI) is a key arterial connection between the cerebral and placental circulations, quantifying AoI blood flow has been proposed to assess this brain sparing effect in clinical practice. While numerous clinical studies have studied this parameter, fundamental understanding of its determinant factors and its quantitative relation with other aspects of haemodynamic remodeling has been limited. Computational models of the cardiovascular circulation have been proposed for exactly this purpose since they allow both for studying the contributions from isolated parameters as well as estimating properties that cannot be directly assessed from clinical measurements. Therefore, a computational model of the fetal circulation was developed, including the key elements related to fetal blood redistribution and using measured cardiac outflow profiles to allow personalization. The model was first calibrated using patient-specific Doppler data from a healthy fetus. Next, in order to understand the contributions of the main parameters determining blood redistribution, AoI and middle cerebral artery (MCA) flow changes were studied by variation of cerebral and peripheral-placental resistances. Finally, to study how this affects an individual fetus, the model was fitted to three IUGR cases with different degrees of severity. In conclusion, the proposed computational model provides a good approximation to assess blood flow changes in the fetal circulation. The results support that while MCA flow is mainly determined by a fall in brain resistance, the AoI is influenced by a balance between increased peripheral-placental and decreased cerebral resistances. Personalizing the model allows for quantifying the balance between cerebral and peripheral-placental remodeling

  7. Circulation and effluent dilution modeling in Massachusetts Bay : model implementation, verification and results

    USGS Publications Warehouse

    Signell, Richard P.; Jenter, Harry L.; Blumberg, Alan F.

    1996-01-01

    A three-dimensional hydrodynamic model was developed as part of a cooperative U.S. Geological Survey/Massachusetts Water Resources Authority program to study contaminated sediment accumulation and transport in Massachusetts Bay. This report details the development of the model and assesses how well the model represents observed currents and water properties in the bay. It also summarizes circulation and comparative effluent dilution simulations from existing and future Boston sewage outfalls over a three-year period from October 1, 1989 to December 31, 1992. The ECOM-si model, a semi-implicit version of the Blumberg and Mellor (1987) Estuarine, Coastal and Ocean Model, is shown to reproduce many of the important hydrodynamical features of Massachusetts Bay: the seasonal evolution of the pycnocline, the mean flow pattern, and the strength of sub-tidal current fluctuations. Throughout the simulation period, during both vertically well-mixed and stratified conditions, the seasonal statistics of observed currents are well-represented by the model. The model is therefore appropriate for studying the average dilution of sewage effluent and other continuously discharged substances over seasonal time scales. The ability of the model to reproduce individual flow events varies with season and location within the bay. Flow events during unstratified conditions in western Massachusetts Bay are particularly well-represented, indicating that the model is appropriate for studying processes such as the transport of suspended material from the future outfall site due to winter storms. Individual flow events during stratified conditions and in the offshore Stellwagen Bank region, however, are less well-represented due to small length scales (caused by upwelling and river discharge events) coupled with insufficient data to specify open boundary forcing from the Gulf of Maine. Thus while the model might be used to answer issues such as the frequency with which Gulf of Maine river

  8. Past Asian Monsoon circulation from multiple tree-ring proxies and models (Invited)

    NASA Astrophysics Data System (ADS)

    Anchukaitis, K. J.; Herzog, M.; Hernandez, M.; Martin-Benito, D.; Gagen, M.; LeGrande, A. N.; Ummenhofer, C.; Buckley, B.; Cook, E. R.

    2013-12-01

    The Asian monsoon can be characterized in terms of precipitation variability as well as features of regional atmospheric circulation across a range of spatial and temporal scales. While multicentury time series of tree-ring widths at hundreds of sites across Asia provide estimates of past rainfall, the oxygen isotope ratios of annual rings at some of these sites can reveal broader regional atmosphere-ocean dynamics. Here we present a replicated, multicentury stable isotope series from Vietnam that integrates the influence of monsoon circulation on water isotopes. Stronger (weaker) monsoon flow over Indochina is associated with lower (higher) oxygen isotope values in our long-lived tropical conifers. Ring width and isotopes show particular coherence at multidecadal time scales, and together allow past precipitation amount and circulation strength to be disentangled. Combining multiple tree-ring proxies with simulations from isotope-enabled and paleoclimate general circulation models allows us to independently assess the mechanisms responsible for proxy formation and to evaluate how monsoon rainfall is influenced by ocean-atmosphere interactions at timescales from interannual to multidecadal.

  9. Two regimes of the Arctic's circulation from ocean models with ice and contaminants.

    PubMed

    Proshutinsky, A Y; Johnson, M

    2001-01-01

    A two-dimensional barotropic, coupled, ocean-ice model with a space resolution of 55.5 km and driven by atmospheric forces, river run-off, and sea-level slope between the Pacific and the Arctic Oceans, has been used to simulate the vertically averaged currents and ice drift in the Arctic Ocean. Results from 43 years of numerical simulations of water and ice motions demonstrate that two wind-driven circulation regimes are possible in the Arctic, a cyclonic and an anti-cyclonic circulation. These two regimes appear to alternate at 5-7 year intervals with the 10-15 year period. It is important to pollution studies to understand which circulation regime prevails at any time. It is anticipated that 1995 is a year with a cyclonic regime, and during this cyclonic phase and possibly during past cyclonic regimes as well, pollutants may reach the Alaskan shelf. The regime shifts demonstrated in this paper are fundamentally important to understanding the Arctic's general circulation and particularly important for estimating pollution transport. PMID:11601534

  10. CISOCUR - Hydrodynamic circulation in the Curonian Lagoon inferred through stable isotope measurements and numerical modelling

    NASA Astrophysics Data System (ADS)

    Umgiesser, Georg; Razinkovas-Baziukas, Arturas; Barisevičiūtė, Ruta; Baziukė, Dalia; Ertürk, Ali; Gasiūnaitė, Jovita; Gulbinskas, Saulius; Lubienė, Irma; Maračkinaite, Jurgita; Petkuvienė, Jolita; Pilkaitytė, Renata; Ruginis, Tomas; Zemlys, Petras; Žilius, Mindaugas

    2013-04-01

    The spatial pattern of the hydrodynamic circulation of the Curonian lagoon, the largest European coastal lagoon, is still little understood. In absence of automatic current registration data all the existing models relied mostly on such data as water levels leaving high level of uncertainty. Here we present CISOCUR, a new project financed by the European Social Fund under the Global Grant measure. The project applies a new methodology that uses the carbon stable isotope (SI) ratio of C12 and C13 that characterize different water sources entering the lagoon and may be altered by internal kinetic processes. Through the tracing of these isotope ratios different water masses can be identified. This gives the possibility to validate several hypotheses of water circulation and validate hydrodynamic models. In particular it will be possible to 1) trace water masses entering the lagoon through the Nemunas and the Klaipeda strait; 2) test the hypothesis of sediment transport mechanisms inside the lagoon; 3) evaluate the importance of physical forcing on the lagoon circulation. The use of a hydrodynamic finite element model, coupled with the SI method, will allow for a realistic description of the transport processes inside the Curonian lagoon. So the main research goal is to apply the stable isotope tracers and a finite element model to determine the circulation patterns in the Curonian lagoon. Overall, the project will develop according to 4 main phases: 1) A pilot study to measure the isotope composition of different carbon compounds (dissolved and suspended) in different water bodies that feed water into the central lagoon. Through this pilot study the optimal study sites for the seasonal campaign will be identified as well. 2) Seasonal field campaigns in the monitoring stations identified in phase 1 to measure the carbon isotope ratio. 3) Development of a model that describes the kinetics of carbon isotopes and its transformation. 4) Application of a hydrodynamic model

  11. Modeling the periodic stratification and gravitational circulation in San Francisco Bay, California

    USGS Publications Warehouse

    Cheng, Ralph T.; Casulli, Vincenzo

    1996-01-01

    A high resolution, three-dimensional (3-D) hydrodynamic numerical model is applied to San Francisco Bay, California to simulate the periodic tidal stratification caused by tidal straining and stirring and their long-term effects on gravitational circulation. The numerical model is formulated using fixed levels in the vertical and uniform computational mesh on horizontal planes. The governing conservation equations, the 3-D shallow water equations, are solved by a semi-implicit finite-difference scheme. Numerical simulations for estuarine flows in San Francisco Bay have been performed to reproduce the hydrodynamic properties of tides, tidal and residual currents, and salt transport. All simulations were carried out to cover at least 30 days, so that the spring-neap variance in the model results could be analyzed. High grid resolution used in the model permits the use of a simple turbulence closure scheme which has been shown to be sufficient to reproduce the tidal cyclic stratification and well-mixed conditions in the water column. Low-pass filtered 3-D time-series reveals the classic estuarine gravitational circulation with a surface layer flowing down-estuary and an up-estuary flow near the bottom. The intensity of the gravitational circulation depends upon the amount of freshwater inflow, the degree of stratification, and spring-neap tidal variations.

  12. An analytical and experimental investigation of natural circulation transients in a model pressurized water reactor

    SciTech Connect

    Massoud, M

    1987-01-01

    Natural Circulation phenomena in a simulated PWR was investigated experimentally and analytically. The experimental investigation included determination of system characteristics as well as system response to the imposed transient under symmetric and asymmetric operations. System characteristics were used to obtain correlation for heat transfer coefficient in heat exchangers, system flow resistance, and system buoyancy heat. Asymmetric transients were imposed to study flow oscillation and possible instability. The analytical investigation encompassed development of mathematical model for single-phase, steady-state and transient natural circulation as well as modification of existing model for two-phase flow analysis of phenomena such as small break LOCA, high pressure coolant injection and pump coast down. The developed mathematical model for single-phase analysis was computer coded to simulate the imposed transients. The computer program, entitled ''Symmetric and Asymmetric Analysis of Single-Phase Flow (SAS),'' were employed to simulate the imposed transients. It closely emulated the system behavior throughout the transient and subsequent steady-state. Modifications for two-phase flow analysis included addition of models for once-through steam generator and electric heater rods. Both programs are faster than real time. Off-line, they can be used for prediction and training applications while on-line they serve for simulation and signal validation. The programs can also be used to determine the sensitivity of natural circulation behavior to variation of inputs such as secondary distribution and power transients.

  13. A Analytical and Experimental Investigation of Natural Circulation Transients in a Model Pressurized Water Reactor

    NASA Astrophysics Data System (ADS)

    Massoud, Mahmoud

    Natural Circulation phenomena in a simulated PWR was investigated experimentally and analytically. The experimental investigation included determination of system characteristics as well as system response to the imposed transient under symmetric and asymmetric operations. System characteristics were used to obtain correlation for heat transfer coefficient in heat exchangers, system flow resistance, and system buoyancy head. Asymmetric transients were imposed to study flow oscillation and possible instability. The analytical investigation encompassed development of mathematical model for single-phase, steady-state and transient natural circulation as well as modification of existing model for two-phase flow analysis of phenomena such as small break LOCA, high pressure coolant injection and pump coast down. The developed mathematical model for single-phase analysis was computer coded to simulate the imposed transients. The computer program, entitled "Symmetric and Asymmetric Analysis of Single-Phase Flow (SAS)," were employed to simulate the imposed transients. It closely emulated the system behavior throughout the transient and subsequent steady -state. Modifications for two-phase flow analysis included addition of models for once-through steam generator and electric heater rods. Both programs are faster than real time. Off-line, they can be used for prediction and training applications while on-line they serve for simulation and signal validation. The programs can also be used to determine the sensitivity of natural circulation behaviour to variation of inputs such as secondary distribution and power transients.

  14. Stratospheric wind errors, initial states and forecast skill in the GLAS general circulation model

    NASA Technical Reports Server (NTRS)

    Tenenbaum, J.

    1983-01-01

    Relations between stratospheric wind errors, initial states and 500 mb skill are investigated using the GLAS general circulation model initialized with FGGE data. Erroneous stratospheric winds are seen in all current general circulation models, appearing also as weak shear above the subtropical jet and as cold polar stratospheres. In this study it is shown that the more anticyclonic large-scale flows are correlated with large forecast stratospheric winds. In addition, it is found that for North America the resulting errors are correlated with initial state jet stream accelerations while for East Asia the forecast winds are correlated with initial state jet strength. Using 500 mb skill scores over Europe at day 5 to measure forecast performance, it is found that both poor forecast skill and excessive stratospheric winds are correlated with more anticyclonic large-scale flows over North America. It is hypothesized that the resulting erroneous kinetic energy contributes to the poor forecast skill, and that the problem is caused by a failure in the modeling of the stratospheric energy cycle in current general circulation models independent of vertical resolution.

  15. Accelerating advances in continental domain hydrologic modeling

    USGS Publications Warehouse

    Archfield, Stacey A.; Clark, Martyn; Arheimer, Berit; Hay, Lauren E.; McMillan, Hilary; Kiang, Julie E.; Seibert, Jan; Hakala, Kirsti; Bock, Andrew R.; Wagener, Thorsten; Farmer, William H.; Andreassian, Vazken; Attinger, Sabine; Viglione, Alberto; Knight, Rodney; Markstrom, Steven; Over, Thomas M.

    2015-01-01

    In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.

  16. Accelerating advances in continental domain hydrologic modeling

    NASA Astrophysics Data System (ADS)

    Archfield, Stacey A.; Clark, Martyn; Arheimer, Berit; Hay, Lauren E.; McMillan, Hilary; Kiang, Julie E.; Seibert, Jan; Hakala, Kirsti; Bock, Andrew; Wagener, Thorsten; Farmer, William H.; Andréassian, Vazken; Attinger, Sabine; Viglione, Alberto; Knight, Rodney; Markstrom, Steven; Over, Thomas

    2015-12-01

    In the past, hydrologic modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity among the catchment, global water security, and land surface modeling communities such that these communities are converging toward continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community toward this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or reanalysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behavior; (3) maintaining a balance between model complexity and data availability as well as uncertainties; and (4) quantifying and communicating significant advancements toward these modeling goals.

  17. Interdecadal variations of the thermohaline circulation in a coupled ocean-atmosphere model

    SciTech Connect

    Delworth, T.; Manabe, S.; Stouffer, R.J. )

    1993-11-01

    A fully coupled ocean-atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the NOrth Atlantic Ocean with a time scale of approximately 50 years. The irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation (approximately 52[degrees]N to 72[degrees]N) combined with much smaller density anomalies of opposite sign in the broad, rising region. The spatial pattern of sea surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the North Atlantic. The anomalies of sea surface temperature induce model surface air temperature anomalies over the northern North Atlantic, Arctic, and northwestern Europe. 21 refs., 28 figs.

  18. Crystal balls into the future: are global circulation and water balance models ready?

    NASA Astrophysics Data System (ADS)

    Fekete, Balázs M.; Pisacane, Giovanna; Wisser, Dominik

    2016-10-01

    Variabilities and changes due to natural and anthropogenic causes in the water cycle always presented a challenge for water management planning. Practitioners traditionally coped with variabilities in the hydrological processes by assuming stationarity in the probability distributions and attempted to address non-stationarity by revising this probabilistic properties via continued hydro-climatological observations. Recently, this practice was questioned and more reliance on Global Circulation Models was put forward as an alternative for water management plannig. This paper takes a brief assessment of the state of Global Circulation Models (GCM) and their applications by presenting case studies over Global, European and African domains accompanied by literature examples. Our paper demonstrates core deficiencies in GCM based water resources assessments and articulates the need for improved Earth system monitoring that is essential not only for water managers, but to aid the improvements of GCMs in the future.

  19. Verification of the isotopic composition of precipitation simulated by a regional isotope circulation model over Japan.

    PubMed

    Tanoue, Masahiro; Ichiyanagi, Kimpei; Yoshimura, Kei

    2016-01-01

    The isotopic composition (δ(18)O and δ(2)H) of precipitation simulated by a regional isotope circulation model with a horizontal resolution of 10, 30 and 50 km was compared with observations at 56 sites over Japan in 2013. All simulations produced reasonable spatio-temporal variations in δ(18)O in precipitation over Japan, except in January. In January, simulated δ(18)O values in precipitation were higher than observed values on the Pacific side of Japan, especially during an explosively developing extratropical cyclone event. This caused a parameterisation of precipitation formulation about the large fraction of precipitated water to liquid detrained water in the lower troposphere. As a result, most water vapour that transported from the Sea of Japan precipitated on the Sea of Japan side. The isotopic composition of precipitation was a useful verification tool for the parameterisation of precipitation formulation as well as large-scale moisture transport processes in the regional isotope circulation model.

  20. Derivation of revised formulae for eddy viscous forces used in the ocean general circulation model

    NASA Technical Reports Server (NTRS)

    Chou, Ru Ling

    1988-01-01

    Presented is a re-derivation of the eddy viscous dissipation tensor commonly used in present oceanographic general circulation models. When isotropy is imposed, the currently-used form of the tensor fails to return to the laplacian operator. In this paper, the source of this error is identified in a consistent derivation of the tensor in both rectangular and earth spherical coordinates, and the correct form of the eddy viscous tensor is presented.

  1. Characterizing the surface circulation in Ebro Delta (NW Mediterranean) with HF radar and modeled current data

    NASA Astrophysics Data System (ADS)

    Lorente, P.; Piedracoba, S.; Sotillo, M. G.; Aznar, R.; Amo-Balandron, A.; Pascual, A.; Soto-Navarro, J.; Alvarez-Fanjul, E.

    2016-11-01

    Quality-controlled current observations from a High Frequency radar (HFR) network deployed in the Ebro River Delta (NW Mediterranean) were combined with outputs from IBI operational ocean forecasting system in order to comprehensively portray the ocean state and its variability during 2014. Accurate HFR data were used as benchmark for a rigorous validation of the Iberia-Biscay-Ireland (IBI) regional system, routinely operated in the frame of the Copernicus Marine Environment Monitoring Service (CMEMS). The analysis of skill metrics and monthly averaged current maps showed that IBI reasonably captured the prevailing dynamic features of the coastal circulation previously observed by the HFR, according to the moderate resemblance found in circulation patterns and the spatial distribution of eddy kinetic energy. The model skill assessment was completed with an exploration of dominant modes of spatiotemporal variability. The EOF analysis confirmed that the modeled surface current field evolved both in space and time according to three significantly dominant modes of variability which accounted for the 49.2% of the total variance, in close agreement with the results obtained for HFR (46.1%). The response of the subtidal surface current field to prevailing wind regime in the study area was examined in terms of induced circulation structures and immediacy of reaction by performing a conditional averaging approach and a time-lagged vector correlation analysis, respectively. This observations-model synergistic strategy has proved to be valid to operationally monitor the complex coastal circulation in Ebro Delta despite the observed model drawbacks in terms of reduced energy content in surface currents and some inaccuracies in the wind-driven low frequency response. This integrated methodology aids to improve the prognostic capabilities of IBI ocean forecasting system and also to facilitate high-stakes decision-making for coastal management in the Ebro River Delta marine

  2. Use of Ocean Remote Sensing Data to Enhance Predictions with a Coupled General Circulation Model

    NASA Technical Reports Server (NTRS)

    Rienecker, Michele M.

    1999-01-01

    Surface height, sea surface temperature and surface wind observations from satellites have given a detailed time sequence of the initiation and evolution of the 1997/98 El Nino. The data have beet complementary to the subsurface TAO moored data in their spatial resolution and extent. The impact of satellite observations on seasonal prediction in the tropical Pacific using a coupled ocean-atmosphere general circulation model will be presented.

  3. Characterizing the surface circulation in the Ebro Delta using a HF radar data-model approach

    NASA Astrophysics Data System (ADS)

    Lorente Jimenez, Pablo; Piedracoba Varela, Silvia; Soto-Navarro, Javier; Garcia-Sotillo, Marcos; Alvarez Fanjul, Enrique

    2016-04-01

    One year-long (2014) quality-controlled current observations from a CODAR SeaSonde High Frequency (HF) radar network deployed in the Ebro Delta (northwestern Mediterranean) were combined with operational products provided by a regional ocean forecasting system named IBI (Iberia-Biscay-Ireland) in order to comprehensively portray the ocean state and its variability. First, accurate HF radar data were used as benchmark for the rigorous validation of IBI performance by means of the computation of skill metrics and quality indicators. The analysis of the monthly averaged current maps for 2014 showed that IBI properly captured the prevailing dynamic features of the coastal circulation observed by the HF radar, according to the resemblance of circulation patterns and the eddy kinetic energy spatial distribution. The model skill assessment was completed with an exploration of dominant modes of variability both in time and space. The EOF analysis confirmed that the modeled surface current field evolved in space and time according to three significantly dominant modes of variability which accounted for the 49.2% of the total variance, in close agreement with the results obtained for the HF radar (46.1%). The response of the subtidal surface current field to prevalent wind regimes in the study area was examined in terms of induced circulation structures by performing a conditional averaging approach. This data-model synergistic approach has proved to be valid to operationally monitor and describe the complex coastal circulation in Ebro Delta despite the observed model drawbacks in terms of reduced energy content in surface currents and some inaccuracies in the wind-driven low frequency response. This integrated methodology constitutes a powerful tool for improving operational ocean forecasting systems at European level within the frame of the Copernicus Marine Environment Monitoring Service (CMEMS). It also facilitates high-stakes decision-making for coastal management and

  4. Impacts of Large-Scale Circulation on Convection: A 2-D Cloud Resolving Model Study

    NASA Technical Reports Server (NTRS)

    Li, X; Sui, C.-H.; Lau, K.-M.

    1999-01-01

    Studies of impacts of large-scale circulation on convection, and the roles of convection in heat and water balances over tropical region are fundamentally important for understanding global climate changes. Heat and water budgets over warm pool (SST=29.5 C) and cold pool (SST=26 C) were analyzed based on simulations of the two-dimensional cloud resolving model. Here the sensitivity of heat and water budgets to different sizes of warm and cold pools is examined.

  5. Spectral analysis of CFB data: Predictive models of Circulating Fluidized Bed combustors

    SciTech Connect

    Gamwo, I.K.; Miller, A.; Gidaspow, D.

    1992-04-01

    The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. Spectral analysis of CFB data obtained at Illinois Institute of Technology shows that the frequencies of pressure oscillations are less than 0.1 Hertz and that they increase with solids volume fraction to the usual value of one Hertz obtained in bubbling beds. These data are consistent with the kinetic theory interpretation of density wave propagation.

  6. Turbulence, superrotation, and general circulation models of the atmosphere of Venus

    NASA Astrophysics Data System (ADS)

    Izakov, M. N.

    2016-09-01

    The data obtained in space-borne measurements and the findings of turbulence theory show that turbulence, of both small and large scales, has a decisive influence on the structure and dynamics of the atmosphere of Venus. The small-scale turbulence generates anomalous convection, while large-scale turbulence induces the return spectral flux of energy that is the main element of the superrotation mechanism in the atmosphere. Ways for improving the general circulation model of the atmosphere of Venus are proposed.

  7. Advanced Small Modular Reactor Economics Model Development

    SciTech Connect

    Harrison, Thomas J.

    2014-10-01

    The US Department of Energy Office of Nuclear Energy’s Advanced Small Modular Reactor (SMR) research and development activities focus on four key areas: Developing assessment methods for evaluating advanced SMR technologies and characteristics; and Developing and testing of materials, fuels and fabrication techniques; and Resolving key regulatory issues identified by US Nuclear Regulatory Commission and industry; and Developing advanced instrumentation and controls and human-machine interfaces. This report focuses on development of assessment methods to evaluate advanced SMR technologies and characteristics. Specifically, this report describes the expansion and application of the economic modeling effort at Oak Ridge National Laboratory. Analysis of the current modeling methods shows that one of the primary concerns for the modeling effort is the handling of uncertainty in cost estimates. Monte Carlo–based methods are commonly used to handle uncertainty, especially when implemented by a stand-alone script within a program such as Python or MATLAB. However, a script-based model requires each potential user to have access to a compiler and an executable capable of handling the script. Making the model accessible to multiple independent analysts is best accomplished by implementing the model in a common computing tool such as Microsoft Excel. Excel is readily available and accessible to most system analysts, but it is not designed for straightforward implementation of a Monte Carlo–based method. Using a Monte Carlo algorithm requires in-spreadsheet scripting and statistical analyses or the use of add-ons such as Crystal Ball. An alternative method uses propagation of error calculations in the existing Excel-based system to estimate system cost uncertainty. This method has the advantage of using Microsoft Excel as is, but it requires the use of simplifying assumptions. These assumptions do not necessarily bring into question the analytical results. In fact, the

  8. Modeling 1993-2008 climatology of seasonal general circulation and thermal structure in the Great Lakes using FVCOM

    NASA Astrophysics Data System (ADS)

    Bai, Xuezhi; Wang, Jia; Schwab, David J.; Yang, Yi; Luo, Lin; Leshkevich, George A.; Liu, Songzhi

    2013-05-01

    An unstructured Finite Volume Coastal Ocean Model was applied to all five Great Lakes simultaneously to simulate circulation and thermal structure from 1993 to 2008. Model results are compared to available observations of currents and temperature and previous modeling work. Maps of climatological circulation for all five Great lakes are presented. Winter currents show a two-gyre type circulation in Lakes Ontario and Erie and one large-scale cyclonic circulation in Lakes Michigan, Huron, and Superior. During the summer, a cyclonic circulation remains in Lakes Superior; a primarily cyclonic circulation dominates upper and central Lake Huron; Lake Ontario has a single cyclonic circulation, while circulation in the central basin of Lake Erie remains two-gyre type; Lake Michigan has a cyclonic gyre in the north and an anti-cyclonic one in the south. The temperature profile during the summer is well simulated when a surface wind-wave mixing scheme is included in the model. Main features of the seasonal evolution of water temperature, such as inverse temperature stratification during the winter, the spring and autumn overturn, the thermal bar, and the stratification during summer are well reproduced. The lakes exhibit significant annual and interannual variations in current speed and temperature.

  9. Ocean Circulation Modeling for Aquatic Dispersion of Liquid Radioactive Effluents from Nuclear Power Plants

    SciTech Connect

    Chung, Y.G.; Lee, G.B.; Bang, S.Y.; Choi, S.B.; Lee, S.U.; Yoon, J.H.; Nam, S.Y.; Lee, H.R.

    2006-07-01

    Recently, three-dimensional models have been used for aquatic dispersion of radioactive effluents in relation to nuclear power plant siting based on the Notice No. 2003-12 'Guideline for investigating and assessing hydrological and aquatic characteristics of nuclear facility site' of the Ministry of Science and Technology (MOST) in Korea. Several nuclear power plants have been under construction or planed, which are Shin-Kori Unit 1 and 2, Shin-Wolsong Unit 1 and 2, and Shin-Ulchin Unit 1 and 2. For assessing the aquatic dispersion of radionuclides released from the above nuclear power plants, it is necessary to know the coastal currents around sites which are affected by circulation of East Sea. In this study, a three dimensional hydrodynamic model for the circulation of the East Sea of Korea has been developed as the first phase, which is based on the RIAMOM (Research Institute of Applied Mechanics' Ocean Model, Kyushu University, Japan). The model uses the primitive equation with hydrostatic approximation, and uses Arakawa-B grid system horizontally and Z coordinate vertically. Model domain is 126.5 deg. E to 142.5 deg. E of east longitude and 33 deg. N and 52 deg. N of the north latitude. The space of the horizontal grid was 1/12 deg. to longitude and latitude direction and vertical level was divided to 20. This model uses Generalized Arakawa Scheme, Slant Advection, and Mode-Splitting Method. The input data were from JODC (Japan Oceanographic Data Center), KNFRDI (Korea National Fisheries Research and Development Institute), and ECMWF (European Center for Medium-Range Weather Forecasts). The modeling results are in fairly good agreement with schematic patterns of the surface circulation in the East Sea/Japan Sea. The local current model and aquatic dispersion model of the coastal region will be developed as the second phase. The oceanic dispersion experiments will be also carried out by using ARGO Drifter around a nuclear power plant site. (authors)

  10. MODELING STRATEGIES TO COMPUTE NATURAL CIRCULATION USING CFD IN A VHTR AFTER A LOFA

    SciTech Connect

    Yu-Hsin Tung; Richard W. Johnson; Ching-Chang Chieng; Yuh-Ming Ferng

    2012-11-01

    A prismatic gas-cooled very high temperature reactor (VHTR) is being developed under the next generation nuclear plant program (NGNP) of the U.S. Department of Energy, Office of Nuclear Energy. In the design of the prismatic VHTR, hexagonal shaped graphite blocks are drilled to allow insertion of fuel pins, made of compacted TRISO fuel particles, and coolant channels for the helium coolant. One of the concerns for the reactor design is the effects of a loss of flow accident (LOFA) where the coolant circulators are lost for some reason, causing a loss of forced coolant flow through the core. In such an event, it is desired to know what happens to the (reduced) heat still being generated in the core and if it represents a problem for the fuel compacts, the graphite core or the reactor vessel (RV) walls. One of the mechanisms for the transport of heat out of the core is by the natural circulation of the coolant, which is still present. That is, how much heat may be transported by natural circulation through the core and upwards to the top of the upper plenum? It is beyond current capability for a computational fluid dynamic (CFD) analysis to perform a calculation on the whole RV with a sufficiently refined mesh to examine the full potential of natural circulation in the vessel. The present paper reports the investigation of several strategies to model the flow and heat transfer in the RV. It is found that it is necessary to employ representative geometries of the core to estimate the heat transfer. However, by taking advantage of global and local symmetries, a detailed estimate of the strength of the resulting natural circulation and the level of heat transfer to the top of the upper plenum is obtained.

  11. Ocean circulation model predicts high genetic structure observed in a long-lived pelagic developer.

    PubMed

    Sunday, J M; Popovic, I; Palen, W J; Foreman, M G G; Hart, M W

    2014-10-01

    Understanding the movement of genes and individuals across marine seascapes is a long-standing challenge in marine ecology and can inform our understanding of local adaptation, the persistence and movement of populations, and the spatial scale of effective management. Patterns of gene flow in the ocean are often inferred based on population genetic analyses coupled with knowledge of species' dispersive life histories. However, genetic structure is the result of time-integrated processes and may not capture present-day connectivity between populations. Here, we use a high-resolution oceanographic circulation model to predict larval dispersal along the complex coastline of western Canada that includes the transition between two well-studied zoogeographic provinces. We simulate dispersal in a benthic sea star with a 6-10 week pelagic larval phase and test predictions of this model against previously observed genetic structure including a strong phylogeographic break within the zoogeographical transition zone. We also test predictions with new genetic sampling in a site within the phylogeographic break. We find that the coupled genetic and circulation model predicts the high degree of genetic structure observed in this species, despite its long pelagic duration. High genetic structure on this complex coastline can thus be explained through ocean circulation patterns, which tend to retain passive larvae within 20-50 km of their parents, suggesting a necessity for close-knit design of Marine Protected Area networks.

  12. Modeling circulation and thermal structure in Lake Michigan: Annual cycle and interannual variability

    NASA Astrophysics Data System (ADS)

    Beletsky, Dmitry; Schwab, David J.

    2001-09-01

    A three-dimensional primitive equation numerical model was applied to Lake Michigan for the periods 1982-1983 and 1994-1995 to study seasonal and interannual variability of lake-wide circulation and thermal structure in the lake. The model was able to reproduce all of the basic features of the thermal structure in Lake Michigan: spring thermal bar, full stratification, deepening of the thermocline during the fall cooling, and finally, an overturn in the late fall. Large-scale circulation patterns tend to be cyclonic (counterclockwise), with cyclonic circulation within each subbasin. The largest currents and maximum cyclonic vorticity occur in the fall and winter when temperature gradients are low but wind stresses are strongest. The smallest currents and minimum cyclonic vorticity occur in spring and summer when temperature gradients are strong but wind stresses are weakest. All these facts are in agreement with observations. The main shortcoming of the model was that it tended to predict a more diffuse thermocline than was indicated by observations and explained only up to half of the variance observed in horizontal currents at timescales shorter than a day.

  13. Ocean circulation model predicts high genetic structure observed in a long-lived pelagic developer.

    PubMed

    Sunday, J M; Popovic, I; Palen, W J; Foreman, M G G; Hart, M W

    2014-10-01

    Understanding the movement of genes and individuals across marine seascapes is a long-standing challenge in marine ecology and can inform our understanding of local adaptation, the persistence and movement of populations, and the spatial scale of effective management. Patterns of gene flow in the ocean are often inferred based on population genetic analyses coupled with knowledge of species' dispersive life histories. However, genetic structure is the result of time-integrated processes and may not capture present-day connectivity between populations. Here, we use a high-resolution oceanographic circulation model to predict larval dispersal along the complex coastline of western Canada that includes the transition between two well-studied zoogeographic provinces. We simulate dispersal in a benthic sea star with a 6-10 week pelagic larval phase and test predictions of this model against previously observed genetic structure including a strong phylogeographic break within the zoogeographical transition zone. We also test predictions with new genetic sampling in a site within the phylogeographic break. We find that the coupled genetic and circulation model predicts the high degree of genetic structure observed in this species, despite its long pelagic duration. High genetic structure on this complex coastline can thus be explained through ocean circulation patterns, which tend to retain passive larvae within 20-50 km of their parents, suggesting a necessity for close-knit design of Marine Protected Area networks. PMID:25231198

  14. Global QBO in circulation and ozone. Part 2: A simple mechanistic model

    SciTech Connect

    Tung, K.K.; Yang, H.

    1994-10-01

    Although the phenomenon of equatorial quasi-biennial oscillation is relatively well understood, the problem of how the equatorially confined quasi-biennial oscillation (QBO) wave forcing can induce a signal in the extratropics of comparable or larger magnitude remains unsolved. A simple mechanistic model is constructed to provide a quantitative test of the hypothesis that the phenomenon of extratropical QBO is mainly caused by an anomalous seasonal circulation induced by an anomalous Eliassen-Palm (E-P) flux divergence. The anomaly in E-P flux divergence may be caused in turn by the relative poleward and downward shift of the region of irreversible mixing (breaking) of the extratropical planetary waves during the easterly phase of the equatorial QBO as compared to its westerly phase. The hemispheric nature of the anomaly wave forcing in solstice seasons (viz., no wave breaking in the summer hemisphere) induces a global circulation anomaly that projects predominantly into the first few zonal Hough modes of Plumb. Such a global QBO circulation pattern, although difficult to measure directly, is reflected in the distribution of stratospheric tracers transported by it. Our model produces a global pattern of QBO anomaly in column ozone that appears to account for much of the unfiltered interannual variability in the column ozone observed by the total ozone mapping spectrometer (TOMS) instrument aboard the Nimbus satellite. Furthermore, the model produces the characteristic spectrum of the observation with peaks at periods of 20 and 30 months.

  15. A heuristic simulation model of Lake Ontario circulation and mass balance transport

    USGS Publications Warehouse

    McKenna, J.E.; Chalupnicki, M.A.

    2011-01-01

    The redistribution of suspended organisms and materials by large-scale currents is part of natural ecological processes in large aquatic systems but can contribute to ecosystem disruption when exotic elements are introduced into the system. Toxic compounds and planktonic organisms spend various lengths of time in suspension before settling to the bottom or otherwise being removed. We constructed a simple physical simulation model, including the influence of major tributaries, to qualitatively examine circulation patterns in Lake Ontario. We used a simple mass balance approach to estimate the relative water input to and export from each of 10 depth regime-specific compartments (nearshore vs. offshore) comprising Lake Ontario. Despite its simplicity, our model produced circulation patterns similar to those reported by more complex studies in the literature. A three-gyre pattern, with the classic large counterclockwise central lake circulation, and a simpler two-gyre system were both observed. These qualitative simulations indicate little offshore transport along the south shore, except near the mouths of the Niagara River and Oswego River. Complex flow structure was evident, particularly near the Niagara River mouth and in offshore waters of the eastern basin. Average Lake Ontario residence time is 8 years, but the fastest model pathway indicated potential transport of plankton through the lake in as little as 60 days. This simulation illustrates potential invasion pathways and provides rough estimates of planktonic larval dispersal or chemical transport among nearshore and offshore areas of Lake Ontario. ?? 2011 Taylor & Francis.

  16. A zonally symmetric model for the monsoon-Hadley circulation with stochastic convective forcing

    NASA Astrophysics Data System (ADS)

    De La Chevrotière, Michèle; Khouider, Boualem

    2016-09-01

    Idealized models of reduced complexity are important tools to understand key processes underlying a complex system. In climate science in particular, they are important for helping the community improve our ability to predict the effect of climate change on the earth system. Climate models are large computer codes based on the discretization of the fluid dynamics equations on grids of horizontal resolution in the order of 100 km, whereas unresolved processes are handled by subgrid models. For instance, simple models are routinely used to help understand the interactions between small-scale processes due to atmospheric moist convection and large-scale circulation patterns. Here, a zonally symmetric model for the monsoon circulation is presented and solved numerically. The model is based on the Galerkin projection of the primitive equations of atmospheric synoptic dynamics onto the first modes of vertical structure to represent free tropospheric circulation and is coupled to a bulk atmospheric boundary layer (ABL) model. The model carries bulk equations for water vapor in both the free troposphere and the ABL, while the processes of convection and precipitation are represented through a stochastic model for clouds. The model equations are coupled through advective nonlinearities, and the resulting system is not conservative and not necessarily hyperbolic. This makes the design of a numerical method for the solution of this system particularly difficult. Here, we develop a numerical scheme based on the operator time-splitting strategy, which decomposes the system into three pieces: a conservative part and two purely advective parts, each of which is solved iteratively using an appropriate method. The conservative system is solved via a central scheme, which does not require hyperbolicity since it avoids the Riemann problem by design. One of the advective parts is a hyperbolic diagonal matrix, which is easily handled by classical methods for hyperbolic equations, while

  17. CMIP: a study of climate variability and predictability according to general circulation models

    SciTech Connect

    Covey, C.; Santer, B.D.; Cohen-Solal, E.

    1996-09-01

    Coupled ocean-atmosphere general circulation models are used to predict future global changes, such as warming due to anthropogenic greenhouse gases (Houghton et al., 1996). In addition, coupled-GCM simulations of the natural climate (without human interference) can be compared with observations over the past century. Recent work along such lines concludes that an anthropogenic signal of global warming is emerging from natural variability `noise` (ibid.). More careful and systematic examination of the models seems warranted, however. Toward that end the World Climate Research Program has begun the Coupled ocean-atmosphere Model Intercomparison Project.

  18. a General Circulation Model Investigation of the Atmospheric Response to EL Nino

    NASA Astrophysics Data System (ADS)

    de Aragao, Jose Oribe Rocha

    The observed atmospheric response to sea surface temperature (SST) anomalies associated with El Nino episodes is simulated with the use of a general circulation model (GCM) of the atmosphere. A series of experiments has been performed with the Rasmusson and Carpenter six-episode (El Nino) composite SST anomaly (SSTA) in the tropical Pacific superimposed upon the prescribed climatological SST (CSST). Five independent 400-day runs were made beginning in April of the El Nino year (Year 0) and ending in May of the year after the maximum SSTA in the tropical Pacific (Year +1). Each of the integrations started from different initial conditions selected from different years in a 20 -year control run. The five-year El Nino integration was compared with the control run by analyzing the ensemble monthly, seasonal and annual mean statistics. The model's tropical response resembles the anomalous features found in previous studies. Some features are expected from the constraint imposed by the vorticity balance in the linear theory. For example, the upper level anticyclone pair and the lower level cyclonic circulation centers in the central Pacific are present for almost all months. These responses are significant and seem to be related to the location of both the maximum in CSST and the maximum in SSTA. An anomalous Walker Circulation is found in the vertical plane along the equatorial region. Rainfall departures from the long-term mean are associated with the anomalous Walker Circulation. An analysis of rainfall data over Northeast Brazil reveals sup- pressed rainfall in this area during the rainy season of Year(+1). Significant lower-than-normal rainfall is also found in the model's response during that period. This reduction in precipitation is associated with the downward branch of the anomalous Walker Circulation. The model's extratropical response is weaker than the tropical response and is not well organized. A Pacific/North American (PNA) pattern is present during the

  19. A zonally averaged, three-basin ocean circulation model for climate studies

    SciTech Connect

    Hovine, S.; Fichefet, T.

    1994-09-01

    A two-dimensional, three-basin ocean model suitable for long-term climate studies is developed. The model is based on the zonally averaged form of the primitive equations written in spherical coordinates. The east-west density difference which arises upon averaging the momentum equations is taken to be proportional to the meridional density gradient. Lateral exchanges of heat and salt between the basins are explicitly resolved. Moreover, the model includes bottom topography and has representations of the Arctic Ocean and of the Weddell and Ross seas. Under realistic restoring boundary conditions, the model reproduces the global conveyor belt: deep water is formed in the Atlantic between 60 and 70{degree}N at a rate of about 17 Sv (1 Sv=10{sup 6} m{sup 3}S{sup {minus}1}) and in the vicinity of the Antarctic continent, while the Indian and Pacific basins show broad upwelling. Superimposed on this thermohaline circulation are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed meridional heat transport compare reasonably well with the observational estimates. When mixed boundary conditions i.e., a restoring condition no sea-surface temperature and flux condition on sea-surface salinity are applied, the model exhibits an irregular behavior before reaching a steady state characterized by self-sustained oscillations of 8.5-y period. The conveyor-belt circulation always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state circulations under mixed boundary conditions. Finally, the model sensitivity to various factors is examined. This sensitivity study reveals that the bottom topography and the presence of a submarine meridional ridge in the zone of the Drake passage play a crucial role in determining the properties of the model bottom-water masses. The importance of the seasonality of the surface forcing is also stressed.

  20. Physical mechanisms controlling the initiation of convective self-aggregation in a General Circulation Model

    NASA Astrophysics Data System (ADS)

    Coppin, David; Bony, Sandrine

    2015-12-01

    Cloud-resolving models have shown that under certain conditions, the Radiative-Convective Equilibrium (RCE) could become unstable and lead to the spontaneous organization of the atmosphere into dry and wet areas, and the aggregation of convection. In this study, we show that this "self-aggregation" behavior also occurs in nonrotating RCE simulations performed with the IPSL-CM5A-LR General Circulation Model (GCM), and that it exhibits a strong dependence on sea surface temperature (SST). We investigate the physical mechanisms that control the initiation of self-aggregation in this model, and their dependence on temperature. At low SSTs, the onset of self-aggregation is primarily controlled by the coupling between low-cloud radiative effects and shallow circulations and the formation of "radiatively driven cold pools" in areas devoid of deep convection, while at high SSTs it is primarily controlled by the coupling between surface fluxes and circulation within convective areas. At intermediate temperatures, the occurrence of self-aggregation is less spontaneous and depends on initial conditions, but it can arise through a combination of both mechanisms. Through their coupling to circulation and surface fluxes, the radiative effects of low-level clouds play a critical role in both initiation mechanisms, and the sensitivity of boundary layer clouds to surface temperature explains to a large extent the temperature dependence of convective self-aggregation. At any SST, the presence of cloud-radiative effects in the free troposphere is necessary to the initiation, growth, and maintenance of convective aggregation.

  1. Vertical heat flux in the ocean: Estimates from observations and from a coupled general circulation model

    NASA Astrophysics Data System (ADS)

    Cummins, Patrick F.; Masson, Diane; Saenko, Oleg A.

    2016-06-01

    The net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically. Generally, it is necessary to rely on global climate models to study these processes in detail. In the present study, it is shown that a key component of the vertical heat flux, namely that associated with the large-scale mean vertical circulation, can be diagnosed over extra-tropical regions from global observational data sets. This component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance, combined with estimates of absolute geostrophic flow. Results are compared with the output of a non-eddy resolving, coupled atmosphere-ocean general circulation model. Reasonable agreement is found in the latitudinal distribution of the vertical heat flux, as well as in the area-integrated flux below about 250 m depth. The correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation. The vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the Southern Hemisphere, in particular the Southern Ocean. This is driven by the Ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth. The results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean.

  2. Refining the Subseafloor Circulation Model of the Middle Valley Hydrothermal System Using Fluid Geochemistry

    NASA Astrophysics Data System (ADS)

    Inderbitzen, K. E.; Wheat, C. G.; Baker, P. A.; Fisher, A. T.

    2014-12-01

    Currently, fluid circulation patterns and the evolution of rock/fluid compositions as circulation occurs in subseafloor hydrothermal systems are poorly constrained. Sedimented spreading centers provide a unique opportunity to study subsurface flow because sediment acts as an insulating blanket that traps heat from the cooling magma body and limits: (a) potential flow paths for seawater to recharge the aquifer in permeable upper basaltic basement and (b) points of altered fluid egress. This also allows for a range of thermal and geochemical gradients to exist near the sediment-water interface. Models of fluid circulation patterns in this type of hydrologic setting have been generated (eg. Stein and Fisher, 2001); however fluid chemistry datasets have not previously been used to test the model's viability. We address this issue by integrating the existing circulation model with fluid compositional data collected from sediment pore waters and high temperature hydrothermal vents located in Middle Valley on the Juan de Fuca Ridge. Middle Valley hosts a variety of hydrologic regimes: including areas of fluid recharge (Site 855), active venting (Site 858/1036; Dead Dog vent field), recent venting (Site 856/1035; Bent Hill Massive Sulfide deposit) and a section of heavily sedimented basement located between recharge and discharge sites (Site 857). We will present new results based on thermal and geochemical data from the area of active venting (Sites 858 and 1036), that was collected during Ocean Drilling Program Legs 139 and 169 and a subsequent heat flow/gravity coring effort. These results illuminate fine scale controls on secondary recharge and fluid flow within the sediment section at Site 858/1036. The current status of high temperature vents in this area (based on observations made in July, 2014) will also be outlined.

  3. On the tidally driven circulation in the South China Sea: modeling and analysis

    NASA Astrophysics Data System (ADS)

    Nelko, Varjola; Saha, Abhishek; Chua, Vivien P.

    2014-03-01

    The South China Sea is a large marginal sea surrounded by land masses and island chains, and characterized by complex bathymetry and irregular coastlines. An unstructured-grid SUNTANS model is employed to perform depth-averaged simulations of the circulation in the South China Sea. The model is tidally forced at the open ocean boundaries using the eight main tidal constituents as derived from the OSU Tidal Prediction Software. The model simulations are performed for the year 2005 using a time step of 60 s. The model reproduces the spring-neap and diurnal and semidiurnal variability in the observed data. Skill assessment of the model is performed by comparing model-predicted surface elevations with observations. For stations located in the central region of the South China Sea, the root mean squared errors (RMSE) are less than 10 % and the Pearson's correlation coefficient ( r) is as high as 0.9. The simulations show that the quality of the model prediction is dependent on the horizontal grid resolution, coastline accuracy, and boundary locations. The maximum RMSE errors and minimum correlation coefficients occur at Kaohsiung (located in northern South China Sea off Taiwan coast) and Tioman (located in southern South China Sea off Malaysia coast). This may be explained with spectral analysis of sea level residuals and winds, which reveal dynamics at Kaohsiung and Tioman are strongly influenced by the seasonal monsoon winds. Our model demonstrates the importance of tidally driven circulation in the central region of the South China Sea.

  4. Large-scale circulation patterns, instability factors and global precipitation modeling as influenced by external forcing

    NASA Astrophysics Data System (ADS)

    Bundel, A.; Kulikova, I.; Kruglova, E.; Muravev, A.

    2003-04-01

    The scope of the study is to estimate the relationship between large-scale circulation regimes, various instability indices and global precipitation with different boundary conditions, considered as external forcing. The experiments were carried out in the ensemble-prediction framework of the dynamic-statistical monthly forecast scheme run in the Hydrometeorological Research Center of Russia every ten days. The extension to seasonal intervals makes it necessary to investigate the role of slowly changing boundary conditions among which the sea surface temperature (SST) may be defined as the most effective factor. Continuous integrations of the global spectral T41L15 model for the whole year 2000 (starting from January 1) were performed with the climatic SST and the Reynolds Archive SSTs. Monthly values of the SST were projected on the year days using spline interpolation technique. First, the global precipitation values in experiments were compared to the GPCP (Global Precipitation Climate Program) daily observation data. Although the global mean precipitation is underestimated by the model, some large-scale regional amounts correspond to the real ones (e.g. for Europe) fairly well. On the whole, however, anomaly phases failed to be reproduced. The precipitation averaged over the whole land revealed a greater sensitivity to the SSTs than that over the oceans. The wavelet analysis was applied to separate the low- and high-frequency signal of the SST influence on the large-scale circulation and precipitation. A derivative of the Wallace-Gutzler teleconnection index for the East-Atlantic oscillation was taken as the circulation characteristic. The daily oscillation index values and precipitation amounts averaged over Europe were decomposed using wavelet approach with different “mother wavelets” up to approximation level 3. It was demonstrated that an increase in the precipitation amount over Europe was associated with the zonal flow intensification over the

  5. The spread amongst ENSEMBLES regional scenarios: regional climate models, driving general circulation models and interannual variability

    NASA Astrophysics Data System (ADS)

    Déqué, M.; Somot, S.; Sanchez-Gomez, E.; Goodess, C. M.; Jacob, D.; Lenderink, G.; Christensen, O. B.

    2012-03-01

    Various combinations of thirteen regional climate models (RCM) and six general circulation models (GCM) were used in FP6-ENSEMBLES. The response to the SRES-A1B greenhouse gas concentration scenario over Europe, calculated as the difference between the 2021-2050 and the 1961-1990 means can be viewed as an expected value about which various uncertainties exist. Uncertainties are measured here by variance explained for temperature and precipitation changes over eight European sub-areas. Three sources of uncertainty can be evaluated from the ENSEMBLES database. Sampling uncertainty is due to the fact that the model climate is estimated as an average over a finite number of years (30) despite a non-negligible interannual variability. Regional model uncertainty is due to the fact that the RCMs use different techniques to discretize the equations and to represent sub-grid effects. Global model uncertainty is due to the fact that the RCMs have been driven by different GCMs. Two methods are presented to fill the many empty cells of the ENSEMBLES RCM × GCM matrix. The first one is based on the same approach as in FP5-PRUDENCE. The second one uses the concept of weather regimes to attempt to separate the contribution of the GCM and the RCM. The variance of the climate response is analyzed with respect to the contribution of the GCM and the RCM. The two filling methods agree that the main contributor to the spread is the choice of the GCM, except for summer precipitation where the choice of the RCM dominates the uncertainty. Of course the implication of the GCM to the spread varies with the region, being maximum in the South-western part of Europe, whereas the continental parts are more sensitive to the choice of the RCM. The third cause of spread is systematically the interannual variability. The total uncertainty about temperature is not large enough to mask the 2021-2050 response which shows a similar pattern to the one obtained for 2071-2100 in PRUDENCE. The uncertainty

  6. Mars Pathfinder meteorological observations on the basis of results of an atmospheric global circulation model

    NASA Technical Reports Server (NTRS)

    Forget, Francois; Hourdin, F.; Talagrand, O.

    1994-01-01

    The Mars Pathfinder Meteorological Package (ASI/MET) will measure the local pressure, temperature, and winds at its future landing site, somewhere between the latitudes 0 deg N and 30 deg N. Comparable measurements have already been obtained at the surface of Mars by the Viking Landers at 22 deg N (VL1) and 48 deg N (VL2), providing much useful information on the martian atmosphere. In particular the pressure measurements contain very instructive information on the global atmospheric circulation. At the Laboratoire de Meteorologie Dynamique (LMD), we have analyzed and simulated these measurements with a martian atmospheric global circulation model (GCM), which was the first to simulate the martian atmospheric circulation over more than 1 year. The model is able to reproduce rather accurately many observed features of the martian atmosphere, including the long- and short-period oscillations of the surface pressure observed by the Viking landers. From a meteorological point of view, we think that a landing site located near or at the equator would be an interesting choice.

  7. Study of natural circulation in a VHTR after a LOFA using different turbulence models

    SciTech Connect

    Yu-Hsin Tung; Yuh-Ming Ferng; Richard W. Johnson; Ching-Chang Chieng

    2013-10-01

    Natural convection currents in the core are anticipated in the event of the failure of the gas circulator in a prismatic gas-cooled very high temperature reactor (VHTR). The paths that the helium coolant takes in forming natural circulation loops and the effective heat transport are of interest. The heated flow in the reactor core is turbulent during normal operating conditions and at the beginning of the LOFA with forced convection, but the flow may significantly be slowed down after the event and laminarized with mixed convection. In the present study, the potential occurrence and effective heat transport of natural circulation are demonstrated using computational fluid dynamic (CFD) calculations with different turbulence models as well as laminar flow. Validations and recommendation on turbulence model selection are conducted. The study concludes that large loop natural convection is formed due to the enhanced turbulence levels by the buoyancy effect and the turbulent regime near the interface of upper plenum and flow channels increases the flow resistance for channel flows entering upper plenum and thus less heat can be removed from the core than the prediction by laminar flow assumption.

  8. An Improved Heat Budget Estimation Including Bottom Effects for General Ocean Circulation Models

    NASA Technical Reports Server (NTRS)

    Carder, Kendall; Warrior, Hari; Otis, Daniel; Chen, R. F.

    2001-01-01

    This paper studies the effects of the underwater light field on heat-budget calculations of general ocean circulation models for shallow waters. The presence of a bottom significantly alters the estimated heat budget in shallow waters, which affects the corresponding thermal stratification and hence modifies the circulation. Based on the data collected during the COBOP field experiment near the Bahamas, we have used a one-dimensional turbulence closure model to show the influence of the bottom reflection and absorption on the sea surface temperature field. The water depth has an almost one-to-one correlation with the temperature rise. Effects of varying the bottom albedo by replacing the sea grass bed with a coral sand bottom, also has an appreciable effect on the heat budget of the shallow regions. We believe that the differences in the heat budget for the shallow areas will have an influence on the local circulation processes and especially on the evaporative and long-wave heat losses for these areas. The ultimate effects on humidity and cloudiness of the region are expected to be significant as well.

  9. Numerical Simulations and Tracer Studies as a Tool to Support Water Circulation Modeling in Breeding Reservoirs

    NASA Astrophysics Data System (ADS)

    Zima, Piotr

    2014-12-01

    The article presents a proposal of a method for computer-aided design and analysis of breeding reservoirs in zoos and aquariums. The method applied involves the use of computer simulations of water circulation in breeding pools. A mathematical model of a pool was developed, and a tracer study was carried out. A simplified model of two-dimensional flow in the form of a biharmonic equation for the stream function (converted into components of the velocity vector) was adopted to describe the flow field. This equation, supplemented by appropriate boundary conditions, was solved numerically by the finite difference method. Next, a tracer migration equation was solved, which was a two-dimensional advection-dispersion equation describing the unsteady transport of a non-active, permanent solute. In order to obtain a proper solution, a tracer study (with rhodamine WT as a tracer) was conducted in situ. The results of these measurements were compared with numerical solutions obtained. The results of numerical simulations made it possible to reconstruct water circulation in the breading pool and to identify still water zones, where water circulation was impeded.

  10. Rapid implementation of advanced constitutive models

    NASA Astrophysics Data System (ADS)

    Starman, Bojan; Halilovič, Miroslav; Vrh, Marko; Štok, Boris

    2013-12-01

    This paper presents a methodology based on the NICE integration scheme [1, 2] for simple and rapid numerical implementation of a class of plasticity constitutive models. In this regard, an algorithm is purposely developed for the implementation of newly developed advanced constitutive models into explicit finite element framework. The methodology follows the organization of the problem state variables into an extended form, which allows the constitutive models' equations to be organized in such a way, that the algorithm can be optionally extended with minimal effort to integrate also evolution equations related to a description of other specific phenomena, such as damage, distortional hardening, phase transitions, degradation etc. To confirm simplicity of the program implementation, computational robustness, effectiveness and improved accuracy of the implemented integration algorithm, a deep drawing simulation of the cylindrical cup is considered as the case study, performed in ABAQUS/Explicit. As a fairly complex considered model, the YLD2004-18p model [3, 4] is first implemented via external subroutine VUMAT. Further, to give additional proof of the simplicity of the proposed methodology, a combination of the YLD2004-18p model and Gurson-Tvergaard-Needleman model (GTN) is considered. As demonstrated, the implementation is really obtained in a very simple way.

  11. Variational data assimilation system with nesting model for high resolution ocean circulation

    NASA Astrophysics Data System (ADS)

    Ishikawa, Yoichi; In, Teiji; Nakada, Satoshi; Nishina, Kei; Igarashi, Hiromichi; Hiyoshi, Yoshimasa; Sasaki, Yuji; Wakamatsu, Tsuyoshi; Awaji, Toshiyuki

    2015-10-01

    To obtain the high-resolution analysis fields for ocean circulation, a new incremental approach is developed using a four-dimensional variational data assimilation system with nesting models. The results show that there are substantial biases when using a classical method combined with data assimilation and downscaling, caused by different dynamics resulting from the different resolutions of the models used within the nesting models. However, a remarkable reduction in biases of the low-resolution model relative to the high-resolution model was observed using our new approach in narrow strait regions, such as the Tsushima and Tsugaru straits, where the difference in the dynamics represented by the high- and low-resolution models is substantial. In addition, error reductions are demonstrated in the downstream region of these narrow channels associated with the propagation of information through the model dynamics.

  12. Numerical model of circulation and residence times in the Persian Gulf

    NASA Astrophysics Data System (ADS)

    O'Donncha, Fearghal; Ragnoli, Emanuele

    2014-05-01

    The Persian Gulf is a semi-enclosed, marginal sea that is exposed to arid, subtropical climate. As a consequence of the extreme climate, evaporation is greater than freshwater inflow resulting in a net loss of water and associated, reverse flow, estuarine circulation as the highly saline waters exit the basin through the Straits of Hormuz, into the Gulf of Oman. Because of their consistent direction, these density currents are central in the distribution and removal of pollutants from the gulf. Tidal forcing impacts circulation in the region, particularly on smaller scales of length and time. Wind forcing can be significant, particularly the Shamal weather phenomenon; wind that sets in with great abruptness and force, and is related to synoptic weather systems to the Northwest. Output from high resolution (~1km) numerical simulations, using NEMO (Nucleus for European Modelling of the Ocean), provide insight into the physical oceanography of the region. The model was forced by 0.75° European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric data and tidal constituents extracted from the Oregon State University Tidal Prediction Software (OTPS/TPXO). Model results permit a detailed examination of the three primary forcing processes, namely: tidal forces, wind forces, and density differences. To assess fundamental model performance, results are compared with two historical observation datasets: (1) a comprehensive dataset of velocity and CTD measurements collected by Reynolds (1993) and (2) time series measurements recorded in the Strait of Hormuz from December 1996 to March 1998 by Johns et al. (2003). Model results exhibit close agreement to field values validating the model for a more detailed analysis of circulations patterns within the gulf. To better elucidate the dominant forcing processes, classical tidal analysis decomposed the flow currents by fitting the flow profile to a finite set of sinusoids at specific frequencies related to astronomical

  13. A 3D, finite element model for baroclinic circulation on the Vancouver Island continental shelf

    USGS Publications Warehouse

    Walters, R.A.; Foreman, M.G.G.

    1992-01-01

    This paper describes the development and application of a 3-dimensional model of the barotropic and baroclinic circulation on the continental shelf west of Vancouver Island, Canada. A previous study with a 2D barotropic model and field data revealed that several tidal constituents have a significant baroclinic component (the K1 in particular). Thus we embarked on another study with a 3D model to study the baroclinic effects on the residual and several selected tidal constituents. The 3D model uses a harmonic expansion in time and a finite element discretization in space. All nonlinear terms are retained, including quadratic bottom stress, advection and wave transport (continuity nonlinearity). The equations are solved as a global and a local problem, where the global problem is the solution of the wave equation formulation of the shallow water equations, and the local problem is the solution of the momentum equation for the vertical velocity profile. These equations are coupled to the advection-diffusion equation for density so that density gradient forcing is included in the momentum equations. However, the study presented here describes diagnostic calculations for the baroclinic residual circulation only. The model is sufficiently efficient that it encourages sensitivity testing with a large number of model runs. In this sense, the model is akin to an extension of analytical solutions to the domain of irregular geometry and bottom topography where this parameter space can be explored in some detail. In particular, the consequences of the sigma coordinate system used by the model are explored. Test cases using an idealized representation of the continental shelf, shelf break and shelf slope, lead to an estimation of the velocity errors caused by interpolation errors inherent in the sigma coordinate system. On the basis of these estimates, the computational grid used in the 2D model is found to have inadequate resolution. Thus a new grid is generated with increased

  14. Responses of estuarine circulation and salinity to the loss of intertidal flats - A modeling study

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoqing; Wang, Taiping

    2015-12-01

    Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existing baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Lastly, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.

  15. Responses of estuarine circulation and salinity to the loss of intertidal flats – A modeling study

    DOE PAGES

    Yang, Zhaoqing; Wang, Taiping

    2015-08-25

    Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existingmore » baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.« less

  16. Responses of estuarine circulation and salinity to the loss of intertidal flats – A modeling study

    SciTech Connect

    Yang, Zhaoqing; Wang, Taiping

    2015-08-25

    Intertidal flats in estuaries are coastal wetlands that provide critical marine habitats to support wide ranges of marine species. Over the last century many estuarine systems have experienced significant loss of intertidal flats due to anthropogenic impacts. This paper presents a modeling study conducted to investigate the responses of estuarine hydrodynamics to the loss of intertidal flats caused by anthropogenic actions in Whidbey Basin of Puget Sound on the northwest coast of North America. Changes in salinity intrusion limits in the estuaries, salinity stratification, and circulation in intertidal flats and estuaries were evaluated by comparing model results under the existing baseline condition and the no-flat condition. Model results showed that loss of intertidal flats results in an increase in salinity intrusion, stronger mixing, and a phase shift in salinity and velocity fields in the bay front areas. Model results also indicated that loss of intertidal flats enhances two-layer circulation, especially the bottom water intrusion. Loss of intertidal flats increases the mean salinity but reduces the salinity range in the subtidal flats over a tidal cycle because of increased mixing. Salinity intrusion limits extend upstream in all three major rivers discharging into Whidbey Basin when no intertidal flats are present. Changes in salinity intrusion and estuarine circulation patterns due to loss of intertidal flats affect the nearshore habitat and water quality in estuaries and potentially increase risk of coastal hazards, such as storm surge and coastal flooding. Furthermore, model results suggested the importance of including intertidal flats and the wetting-and-drying process in hydrodynamic simulations when intertidal flats are present in the model domain.

  17. Circulating Tumor Cells from Patients with Advanced Prostate and Breast Cancer Display Both Epithelial and Mesenchymal Markers

    PubMed Central

    Armstrong, Andrew J.; Marengo, Matthew S.; Oltean, Sebastian; Kemeny, Gabor; Bitting, Rhonda L.; Turnbull, James; Herold, Christina I.; Marcom, Paul K.; George, Daniel; Garcia-Blanco, Mariano A.

    2011-01-01

    During cancer progression malignant cells undergo epithelial-mesenchymal transitions (EMTs) and mesenchymal-epithelial transitions (METs) as part of a broad invasion and metastasis program. We previously observed MET events among lung metastases in a preclinical model of prostate adenocarcinoma that suggested a relationship between epithelial plasticity and metastatic spread. We thus sought to translate these findings into clinical evidence by examining the existence of EMT in circulating tumor cells (CTCs) from patients with progressive metastatic solid tumors, with a focus on men with castration-resistant prostate cancer (CRPC) and women with metastatic breast cancer (BC). We show that the majority (>80%) of these CTCs in patients with metastatic CRPC co-express epithelial proteins such as EpCAM, CK, and E-cadherin, mesenchymal proteins, including vimentin, N-cadherin, and O-cadherin, and the stem cell marker CD133. Equally, we find that over 75% of CTCs from women with metastatic BC co-express cytokeratin, vimentin, and N-cadherin. The existence and high frequency of these CTCs co-expressing epithelial, mesenchymal, and stem-cell markers in patients with progressive metastases has important implications for the application and interpretation of approved methods to detect CTCs. PMID:21665936

  18. Advances in Sun-Earth Connection Modeling

    NASA Astrophysics Data System (ADS)

    Ganguli, S. B.; Gavrishchaka, V. V.

    2003-06-01

    Space weather forecasting is a focus of a multidisciplinary research effort motivated by a sensitive dependence of many modern technologies on geospace conditions. Adequate understanding of the physics of the Sun-Earth connection and associated multi-scale magnetospheric and ionospheric processes is an essential part of this effort. Modern physical simulation models such as multimoment multifluid models with effective coupling from small-scale kinetic processes can provide valuable insight into the role of various physical mechanisms operating during geomagnetic storm/substorm activity. However, due to necessary simplifying assumptions, physical models are still not well suited for accurate real-time forecasting. Complimentary approach includes data-driven models capable of efficient processing of multi-scale spatio-temporal data. However, the majority of advanced nonlinear algorithms, including neural networks (NN), can encounter a set of problems called dimensionality curse when applied to high-dimensional data. Forecasting of rare/extreme events such as large geomagnetic storms/substorms is of the most practical importance but is also very challenging for many existing models. A very promising algorithm that combines the power of the best nonlinear techniques and tolerance to high-dimensional and incomplete data is support vector machine (SVM). We have summarized advantages of the SVM and described a hybrid model based on SVM and extreme value theory (EVT) for rare event forecasting. Results of the SVM application to substorm forecasting and future directions are discussed.

  19. Water-Ice Clouds in the LMDs Martian General Circulation Model

    NASA Technical Reports Server (NTRS)

    Montmessin, F.; Forget, F.; Haberle, R. M.; Rannou, P.; Cabane, M.

    2003-01-01

    The interest for Martian water ice clouds has recently taken a new extent given their likely involvement both in climate and in the hydrological cycle. Previous related microphysical studies have already discussed the complex interactions between airborne dust and clouds [2]. Whereas water ice mantles upon dust cores enhance sedimentation rates and thus possibly change the vertical distribution of dust and water, the advection of clouds by winds could also modulate the geographical distribution of volatiles. Within this context, only 3D modeling based on the use of Martian General Circulation Models (MGCM) is able to give us a consistent clue of the global climatic aspects of Martian clouds.

  20. Experience with a vectorized general circulation weather model on Star-100

    NASA Technical Reports Server (NTRS)

    Soll, D. B.; Habra, N. R.; Russell, G. L.

    1977-01-01

    A version of an atmospheric general circulation model was vectorized to run on a CDC STAR 100. The numerical model was coded and run in two different vector languages, CDC and LRLTRAN. A factor of 10 speed improvement over an IBM 360/95 was realized. Efficient use of the STAR machine required some redesigning of algorithms and logic. This precludes the application of vectorizing compilers on the original scalar code to achieve the same results. Vector languages permit a more natural and efficient formulation for such numerical codes.

  1. Electrodynamic effects of thermospheric winds from the NCAR thermospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Richmond, A. D.; Roble, R. G.

    1987-01-01

    Electrodynamic effects of thermospheric winds simulated with the NCAR thermospheric general circulation model (TGCM) were modeled and compared with observations for equinox solar minimum conditions. Two TGCM wind simulations were used: one driven only by in situ solar UV heating, the other also including lower boundary forcing that mimics the effects of upward propagating semidiurnal tides. It was found that, without tidal forcing, the TGCM winds produce ground magnetic variations that have the general pattern of observed Sq variations, but are only about half as strong. The addition of tidal forcing improved the agreement between calculated and observed magnetic variations and between calculated and observed electric fields.

  2. General circulation model simulations of winter and summer sea-level pressures over North America

    USGS Publications Warehouse

    McCabe, G.J.; Legates, D.R.

    1992-01-01

    In this paper, observed sea-level pressures were used to evaluate winter and summer sea-level pressures over North America simulated by the Goddard Institute for Space Studies (GISS) and the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation models. The objective of the study is to determine how similar the spatial and temporal distributions of GCM-simulated daily sea-level pressures over North America are to observed distributions. Overall, both models are better at reproducing observed within-season variance of winter and summer sea-level pressures than they are at simulating the magnitude of mean winter and summer sea-level pressures. -from Authors

  3. Numerical Modeling of Water Circulation and Pollutant Transport in a Shallow Basin

    NASA Astrophysics Data System (ADS)

    Charafi, My. M.; Sadok, A.; Kamal, A.; Menai, A.

    A two-dimensional numerical model was developed1-3 to simulate the sediment and pollutant transport in a shallow basin. The developed model consist of two modules: Hydrodynamic module and sediment/pollutant transport module. A numerical hydrodynamic module based on the Saint-Venant equations, is resolved by a MacCormack numerical scheme and is used to simulate the circulation pattern in the basin. The obtained flow circulation is used as an input to the sediment/pollutant transport module to simulate the transport and dispersion of a pollutant emitted into the basin. To calibrate the numerical model, the distorted scale model of the Windermere Basin4 was used. In this physical model, the flow visualization and pollutant transport experiments provide a good calibration. The simulated results were found to be in good agreement with the experimental measurements and the results in Ref. 4. With the aid of the validated model, the influence of the construction of dikes on the residence time distributions in the basin was examined.

  4. On the comparison between seasonal predictive skill of global circulation models: Coupled versus uncoupled

    NASA Astrophysics Data System (ADS)

    Beraki, Asmerom F.; Landman, Willem A.; DeWitt, David

    2015-11-01

    The study compares one- and two-tiered forecasting systems as represented by the South African Weather Service Coupled Model and its atmosphere-only version. In this comparative framework, the main difference between these global climate models (GCMs) resides in the manner in which the sea surface temperature (SST) is represented. The models are effectively kept similar in all other aspects. This strategy may allow the role of coupling on the predictive skill differences to be better distinguished. The result reveals that the GCMs differ widely in their performances and the issue of superiority of one model over the other is mostly dependent on the ability to a priori determine an optimal global SST field for forcing the atmospheric general circulation model (AGCM). Notwithstanding, the AGCM's fidelity is reasonably reduced when the AGCM is constrained with persisting SST anomalies to the extent to which the coupled general circulation model's superiority becomes noticeable. The result suggests that the boundary forcing coming from the optimal SST field plays a significant role in leveraging a reasonable equivalency in the predictive skill of the two GCM configurations.

  5. CMIP: A study of climate variability and predictability according to general circulation models

    SciTech Connect

    Covey, C.; Santer, B.D.; Cohen-Solal, E.

    1997-11-01

    The Coupled ocean-atmosphere Model Intercomparison Project (CMIP) is very briefly described, and preliminary results are presented. The goal of CMIP is to comprehensively study to behavior of global coupled models of the atmosphere, ocean, and sea ice. CMIP is presently examining control runs in which external forcing terms are held constant. CMIP has received output from 17 different coupled general circulation model control runs. For the shortest time scale examined, the seasonal cycle, the modeled surface air temperature agrees fairly well with observations. This is a nontrivial result because about half the models examined refrain from using flux correction to move their results closer to observations. Power spectra of the globally and annually averaged surface air temperature are presented, and reveal substantial differences in interannual variability among the models. 3 refs., 1 fig., 1 tab.

  6. Spherical harmonic analysis of a synoptic climatology generated with a global general circulation model

    NASA Technical Reports Server (NTRS)

    Christidis, Z. D.; Spar, J.

    1980-01-01

    Spherical harmonic analysis was used to analyze the observed climatological (C) fields of temperature at 850 mb, geopotential height at 500 mb, and sea level pressure. The spherical harmonic method was also applied to the corresponding "model climatological" fields (M) generated by a general circulation model, the "GISS climate model." The climate model was initialized with observed data for the first of December 1976 at 00. GMT and allowed to generate five years of meteorological history. Monthly means of the above fields for the five years were computed and subjected to spherical harmonic analysis. It was found from the comparison of the spectral components of both sets, M and C, that the climate model generated reasonable 500 mb geopotential heights. The model temperature field at 850 mb exhibited a generally correct structure. However, the meridional temperature gradient was overestimated and overheating of the continents was observed in summer.

  7. Advanced modeling of prompt fission neutrons

    SciTech Connect

    Talou, Patrick

    2009-01-01

    Theoretical and numerical studies of prompt fission neutrons are presented. The main results of the Los Alamos model often used in nuclear data evaluation work are reviewed briefly, and a preliminary assessment of uncertainties associated with the evaluated prompt fission neutron spectrum for n (0.5 MeV)+{sup 239}Pu is discussed. Advanced modeling of prompt fission neutrons is done by Monte Carlo simulations of the evaporation process of the excited primary fission fragments. The successive emissions of neutrons are followed in the statistical formalism framework, and detailed information, beyond average quantities, can be inferred. This approach is applied to the following reactions: {sup 252}Cf (sf), n{sub th} + {sup 239}Pu, n (0.5 MeV)+{sup 235}U, and {sup 236}Pu (sf). A discussion on the merits and present limitations of this approach concludes this presentation.

  8. Prospects for Advanced RF Theory and Modeling

    SciTech Connect

    Batchelor, D.B.

    1999-04-12

    This paper represents an attempt to express in print the contents of a rather philosophical review talk. The charge for the talk was not to summarize the present status of the field and what we can do, but to assess what we will need to do in the future and where the gaps are in fulfilling these needs. The objective was to be complete, covering all aspects of theory and modeling in all frequency regimes, although in the end the talk mainly focussed on the ion cyclotron range of frequencies (ICRF). In choosing which areas to develop, it is important to keep in mind who the customers for RF modeling are likely to be and what sorts of tasks they will need for RF to do. This occupies the first part of the paper. Then we examine each of the elements of a complete RF theory and try to identify the kinds of advances needed.

  9. Cross-shelf exchange in a model of the Ross Sea circulation and biogeochemistry

    NASA Astrophysics Data System (ADS)

    Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.

    2003-11-01

    Transport of warm, nutrient-rich Circumpolar Deep Water (CDW) onto Antarctic continental shelves and coastal seas has important effects on physical and biological processes. The present study investigates the locations of this transport and its dynamics in the Ross Sea with a high-resolution three-dimensional numerical model. The model circulation is forced by daily wind stress along with heat and salt fluxes calculated from atmospheric climatologies by bulk formulae. All surface fluxes are modified by an imposed climatological ice cover. Waters under the Ross Ice Shelf are not included explicitly, but their effect on temperature and salinity is imposed in a buffer zone at the southern end of the model domain. A simple nutrient uptake is calculated based on the climatological chlorophyll distribution and Monod uptake kinetics. Model circulation is strongly affected by bottom topography, due to weak stratification, and agrees with schematics of the general flow and long-term current measurements except near the southern boundary. The sea-surface temperature is similar to satellite estimates except that the warmest simulated temperatures are slightly higher than observations. There is a significant correlation between the curvature of the shelf break and the transport across the shelf break. A momentum term balance shows that momentum advection helps to force flow across the shelf break in specific locations due to the curvature of the bathymetry (that is, the isobaths curve in front of the flow). For the model to create a strong intrusion of CDW onto the shelf, it appears two mechanisms are necessary. First, CDW is driven onto the shelf at least partially due to momentum advection and the curvature of the shelf break; then, the general circulation on the shelf takes the CDW into the interior.

  10. Development of numerical model for material circulation around seabed sediment at coastal area

    NASA Astrophysics Data System (ADS)

    Tsukahara, Y.; Nakatani, N.; Yamazaki, T.

    2012-12-01

    In enclosed coastal seas, many organic matters are deposited at the seabed because of excessive pollution load from rivers. Organic materials are decomposed by several bacteria with consumption of dissolved oxygen in the bottom water. Consequently, dysoxic water mass are formed and aerobium decreases drastically. Due to dysoxic water mass, some environmental problems are posed such as eluting hydrogen sulfide and blue tide. It is essential to grasp an understanding for decomposition of organic material and exchange of nutrients and oxygen between the seabed sediment and the bottom water. To clarify material circulation in seabed sediment, it is effective and useful to simulation using numerical model. Fossing et al. (2004) constructed numerical model represented material circulation included phosphorus dynamic state around the seabed sediment in Arhus Bay. Alternatively, Nagao et al. (2008) and Irie et al. (2010) estimated elution rate based on numerical model using Fossing's model. However, it is incomplete to describe the vertical profiles and elution rate of some materials. These results are thought to be due to lack of knowledge for degradation processes in the seabed and other chemical reactions. In this research, dynamic state of each material circulation is investigated using an experimental aquarium that enable to sampling pore water in seabed sediment intermittently. In additional approach, field work is conducted in Amagasaki Bay regarded as coastal area polluted significantly. Authors modified more precisely Fossing's model by comparing and applying these results of experiment and field works. Results of our research can accumulate a scientific knowledge about effect of deposition in the seabed sediment to coastal area.;

  11. Advancing an Information Model for Environmental Observations

    NASA Astrophysics Data System (ADS)

    Horsburgh, J. S.; Aufdenkampe, A. K.; Hooper, R. P.; Lehnert, K. A.; Schreuders, K.; Tarboton, D. G.; Valentine, D. W.; Zaslavsky, I.

    2011-12-01

    have been modified to support data management for the Critical Zone Observatories (CZOs). This paper will present limitations of the existing information model used by the CUAHSI HIS that have been uncovered through its deployment and use, as well as new advances to the information model, including: better representation of both in situ observations from field sensors and observations derived from environmental samples, extensibility in attributes used to describe observations, and observation provenance. These advances have been developed by the HIS team and the broader scientific community and will enable the information model to accommodate and better describe wider classes of environmental observations and to better meet the needs of the hydrologic science and CZO communities.

  12. Impact of fluorescent silicon nanoparticles on circulating hemolymph and hematopoiesis in an invertebrate model organism.

    PubMed

    Xing, Rui; Li, Kai-Le; Zhou, Yan-Feng; Su, Yuan-Yuan; Yan, Si-Qi; Zhang, Kai-Long; Wu, Si-Cong; Sima, Yang-Hu; Zhang, Ke-Qin; He, Yao; Xu, Shi-Qing

    2016-09-01

    Silicon nanoparticles (SiNPs) have attractive potential applications in biological and medical fields, and yet their impact on animals is still controversial, and there have been no reports of their effects on hematopoiesis. In this study, the effects of SiNPs on hemocytes and hematopoiesis were investigated by administering SiNPs via a vascular injection into an invertebrate model, the silkworm. Our results show that the ability of SiNPs to enter different types of circulating hemocytes and their impact on those hemocytes differed significantly. Rapid accumulation of SiNPs was observed in granulocytes, oenocytoids, and spherulocytes, which have immune functions in the circulating hemolymph, whereas SiNPs did not easily enter prohemocytes, which can differentiate into granulocytes, oenocytoids, and spherulocytes and replenish them. The SiNPs that entered the hemocytes initiated autophagy and apoptosis via the lysosomal/mitochondrial pathway. High-dose SiNPs weakly stimulated lysosomal activity in hematopoietic organs, but did not lead to a significant increase in reactive oxygen species or severe autophagy or apoptosis in the organ tissues. We suggest that the damage caused by high-dose SiNPs to hematopoiesis is self-healing, because few SiNPs entered the hematopoietic stem cells in the circulating hemolymph, so the damage to the hematopoietic tissues was limited. PMID:27348562

  13. General circulation modeling of the thermosphere-ionosphere during a geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yiǧit, Erdal; Immel, Thomas; Ridley, Aaron; Frey, Harald U.; Moldwin, Mark

    2016-07-01

    Using a three-dimensional general circulation model (GCM) of the upper atmosphere, we investigate the response of the thermosphere-ionosphere system to the August 2011 major geomagnetic storm. The GCM is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to ~150%. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20% increase in high-latitude mean temperature, respectively. The global mean Joule heating of the neutral atmosphere increases by more than a factor of three. There are distinct hemispheric differences in the magnitude and morphology of the horizontal ion flows and thermospheric circulation during the different phases of the storm. The thermospheric circulation demonstrates the largest amount of hemispheric differences during the later stages of the storm. Dynamical diagnostics show that advective forcing contributes to hemispheric differences.

  14. Haemodynamic modeling of the cardiovascular system using mock circulation loops to test cardiovascular devices.

    PubMed

    Timms, Daniel L; Gregory, Shaun D; Stevens, Michael C; Fraser, John F

    2011-01-01

    Comprehensive testing and evaluation of cardiovascular device function and performance is required prior to clinical implementation. Initial proof of concept investigations are conducted within in-vitro mock circulation loops, before proof of principle is demonstrated via in-vivo animal testing. To facilitate the rapid transition of cardiovascular devices through this development period, a testing apparatus was developed that closely models the natural human cardiovascular system haemodynamics. This mock circulation system accurately replicates cardiac function, coupled to systemic and pulmonary circulations. The physiological response produced by a number of clinical cardiovascular conditions can be actively controlled by variable parameters such as vascular resistance, arterial/venous compliance, ventricle contractility, heart rate, and heart /vascular volumes, while anatomical variations such as valve regurgitation and septal defects can be included. Auto-regulation of these parameters was attempted to reproduce the Frank-Starling mechanism, baroreceptor reflex, skeletal muscle pump, and postural changes. Steady state validation of loop performance was achieved by replicating the progression of a patient's clinical haemodynamics from heart failure, through VAD support, to heart transplantation. The system has been used to evaluate pulsatile and non-pulsatile ventricular assist devices, counter pulsation devices, non-invasive cardiac output monitors and cardiovascular stents. The interaction of these devices with the cardiovascular system was also investigated with regards to physiological control strategies and cannula placement. The system is a valuable tool for the accelerated progression of cardiovascular device development.

  15. Advances in Homology Protein Structure Modeling

    PubMed Central

    Xiang, Zhexin

    2007-01-01

    Homology modeling plays a central role in determining protein structure in the structural genomics project. The importance of homology modeling has been steadily increasing because of the large gap that exists between the overwhelming number of available protein sequences and experimentally solved protein structures, and also, more importantly, because of the increasing reliability and accuracy of the method. In fact, a protein sequence with over 30% identity to a known structure can often be predicted with an accuracy equivalent to a low-resolution X-ray structure. The recent advances in homology modeling, especially in detecting distant homologues, aligning sequences with template structures, modeling of loops and side chains, as well as detecting errors in a model, have contributed to reliable prediction of protein structure, which was not possible even several years ago. The ongoing efforts in solving protein structures, which can be time-consuming and often difficult, will continue to spur the development of a host of new computational methods that can fill in the gap and further contribute to understanding the relationship between protein structure and function. PMID:16787261

  16. Enhanced evidence in climate models for changes in extratropical atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Paeth, Heiko; Pollinger, Felix

    2010-10-01

    We investigate changes in extratropical atmospheric circulation as derived from the most recent multi-model ensemble of global climate projections. This internationally coordinated systematic data base allows for an accurate assessment of climate change signals against the background of model uncertainty. The multi-model mean time series of the northern-hemisphere (NAM) and southern-hemisphere (SAM) annular modes and of the North Atlantic Oscillation (NAO) are in line with the observed positive trends during the second half of the 20th century and project a further strengthening until the end of the 21st century. For SAM and NAM the simulated changes are unambiguously related to anthropogenic forcing and outperform the level of model uncertainty. This result may imply an enhanced probability for some severe regional impacts of climate change, in particular over extratropical land masses. The climate change signals are noticeably weaker under the B1 mitigation scenario than under the A2 business-as-usual scenario. Ozone forcing has a significant impact on the amplitude of future circulation changes, whereas no systematic effect is found with respect to the models' top-of-the-atmosphere.

  17. Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Xue, Z.; He, R.; Fennel, K.; Cai, W.-J.; Lohrenz, S.; Hopkinson, C.

    2013-05-01

    A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient input from major rivers. A 7 yr model hindcast (2004-2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in-situ observations including coastal sea-level, ocean temperature, salinity, and nutrient concentration. The model hindcast revealed clear seasonality in nutrient, phytoplankton and zooplankton distributions in the GoM. An Empirical Orthogonal Function analysis indicated a phase-locked pattern among nutrient, phytoplankton and zooplankton concentrations. The GoM shelf nutrient budget was also quantified, revealing that on an annual basis ~80% of nutrient input was denitrified on the shelf and ~17% was exported to the deep ocean.

  18. Modeling ocean circulation and biogeochemical variability in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Xue, Z.; He, R.; Fennel, K.; Cai, W.-J.; Lohrenz, S.; Hopkinson, C.

    2013-11-01

    A three-dimensional coupled physical-biogeochemical model is applied to simulate and examine temporal and spatial variability of circulation and biogeochemical cycling in the Gulf of Mexico (GoM). The model is driven by realistic atmospheric forcing, open boundary conditions from a data assimilative global ocean circulation model, and observed freshwater and terrestrial nitrogen input from major rivers. A 7 yr model hindcast (2004-2010) was performed, and validated against satellite observed sea surface height, surface chlorophyll, and in situ observations including coastal sea level, ocean temperature, salinity, and dissolved inorganic nitrogen (DIN) concentration. The model hindcast revealed clear seasonality in DIN, phytoplankton and zooplankton distributions in the GoM. An empirical orthogonal function analysis indicated a phase-locked pattern among DIN, phytoplankton and zooplankton concentrations. The GoM shelf nitrogen budget was also quantified, revealing that on an annual basis the DIN input is largely balanced by the removal through denitrification (an equivalent of ~ 80% of DIN input) and offshore exports to the deep ocean (an equivalent of ~ 17% of DIN input).

  19. An eddy-permitting oceanic general circulation model and its preliminary evaluation

    NASA Astrophysics Data System (ADS)

    Liu, Hailong; Zhang, Xuehong; Li, Wei; Yu, Yongqiang; Yu, Rucong

    2004-10-01

    An eddy-permitting, quasi-global oceanic general circulation model, LICOM (LASG/IAP (State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics) Climate System Ocean Model), with a uniform grid of 0.5° × 0.5° is established. Forced by wind stresses from Hellerman and Rosenstain (1983), a 40-yr integration is conducted with sea surface temperature and salinity being restored to the Levitus 94 datasets. The evaluation of the annual mean climatology of the LICOM control run shows that the large-scale circulation can be well reproduced. A comparison between the LICOM control run and a parallel integration of L30T63, which has the same framework but a coarse resolution, is also made to confirm the impact of resolution on the model performance. On account of the reduction of horizontal viscosity with the enhancement of the horizontal resolution, LICOM improves the simulation with respect to not only the intensity of the large scale circulations, but also the magnitude and structure of the Equatorial Undercurrent and South Equatorial Current. Taking advantage of the fine grid size, the pathway of the Indonesian Throughflow (ITF) is better represented in LICOM than in L30T63. The transport of ITF in LICOM is more convergent in the upper layer. As a consequence, the Indian Ocean tends to get warmer in LICOM. The poleward heat transports for both the global and individual basins are also significantly improved in LICOM. A decomposed analysis indicates that the transport due to the barotropic gyre, which primarily stands for the barotropic effect of the western boundary currents, plays a crucial role in making the difference.

  20. THOR-ISO: a Global Circulation Model for Exoplanets on an Icosahedral Grid

    NASA Astrophysics Data System (ADS)

    Mendonca, J.; Grimm, S.; Heng, K.

    2015-10-01

    In this presentation I will describe the details and first results of our new dynamical code for exoplanet atmospheres. This model is part of the Exoclimes Simulation Platform (ESP), and is a project of the Exoplanet and Exoclimes Group (see www.exoclime.org). The model I will present solves the complex physical and dynamical equations that include fundamental principles of atmospheric fluid dynamics and various idealisations of radiative transfer and dry convection, among others. I will also show the results of the first successful benchmark tests for this model, where we explore the results of the model for Earth-like and Hot-Jupiter like conditions. The analysis of the results from this complex and detailed model, will help us to have a better understanding of the diversity of climates and atmospheric circulations that we expect to find in the multitude of exoplanets already discovered.

  1. Tracer water transport and subgrid precipitation variation within atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Koster, Randal D.; Eagleson, Peter S.; Broecker, Wallace S.

    1988-01-01

    A capability is developed for monitoring tracer water movement in the three-dimensional Goddard Institute for Space Science Atmospheric General Circulation Model (GCM). A typical experiment with the tracer water model follows water evaporating from selected grid squares and determines where this water first returns to the Earth's surface as precipitation or condensate, thereby providing information on the lateral scales of hydrological transport in the GCM. Through a comparison of model results with observations in nature, inferences can be drawn concerning real world water transport. Tests of the tracer water model include a comparison of simulated and observed vertically-integrated vapor flux fields and simulations of atomic tritium transport from the stratosphere to the oceans. The inter-annual variability of the tracer water model results is also examined.

  2. An approach for modeling thermal destruction of hazardous wastes in circulating fluidized bed incinerator.

    PubMed

    Patil, M P; Sonolikar, R L

    2008-10-01

    This paper presents a detailed computational fluid dynamics (CFD) based approach for modeling thermal destruction of hazardous wastes in a circulating fluidized bed (CFB) incinerator. The model is based on Eular - Lagrangian approach in which gas phase (continuous phase) is treated in a Eularian reference frame, whereas the waste particulate (dispersed phase) is treated in a Lagrangian reference frame. The reaction chemistry hasbeen modeled through a mixture fraction/ PDF approach. The conservation equations for mass, momentum, energy, mixture fraction and other closure equations have been solved using a general purpose CFD code FLUENT4.5. Afinite volume method on a structured grid has been used for solution of governing equations. The model provides detailed information on the hydrodynamics (gas velocity, particulate trajectories), gas composition (CO, CO2, O2) and temperature inside the riser. The model also allows different operating scenarios to be examined in an efficient manner. PMID:19697764

  3. Puchezh-Katunki Impact Crater: Preliminary Model of Hydrothermal Circulation System

    NASA Astrophysics Data System (ADS)

    Masaitis, V. L.; Naumov, M. V.

    1993-07-01

    Research (using the results of deep drilling) of hydrothermal alteration in the Puchezh-Katunki Crater [1,2] enables us to construct a preliminary model of a hot-water circulation system in this giant astrobleme. Unlike previous reconstructions [3] that consider a circulation system originated in connection with the mass of impact melt in an ideal astrobleme, we examine this process in the impact crater as a whole. Considerable hydrothermal alteration of rocks is restricted by central uplift of the Puchezh-Katunki Crater. The preimpact temperature of the uplift's crystalline rocks (those that occur at 5-6 km in depth before impact) could be more than 100 degrees C. The principal factors that caused the creation of the circulation system are (1) the thermal field of the massif of brecciated and heated rocks and (2) crater lake formation. Shock- and friction-enhanced heating coupled with the influence of injecting impact melt masses generated an ellipsoidal-shaped thermal anomaly for 5-6 km in depth and near 600 km in volume. The heated massif was characterized by temperature values after equilibration from 500 degrees-600 degrees C in the center to 100 degrees-200 degrees C at the edges. The porosity of rocks decreased at depth and outward from the center as well. Hydrothermal convection took place when water from a ring trough lake infiltrated the lens of hot and porous impact breccia and basement rocks, reaching the surface at the uplift's margins and in the bottom of the central pit. A meteoric origin of circulated water is corroborated by isotopic values of fracture-filling calcite (delta ^18O = 21-24 per mil SMOW; delta ^13C = -20-3 per mil PDB) and anhydrite (delta ^18O = 8-10 per mil SMOW). There is no reliable information about addition of any juvenile substance in the circulation system. These facts support the subsurface origin of hydrothermal circulation. The united regressive hydrothermal process may be subdivided into three successive stages (Fig. 1): 1

  4. A Distributed Water Circulation Model Incorporating Large Irrigation Schemes for Paddy Areas

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Masumoto, T.; Kudo, R.; Horikawa, N.

    2010-12-01

    Water intake for paddy irrigation in Japan accounts for approximately 70% of total intake. Spatial and temporal variation of precipitation and river flow changes, likely to be caused by climate changes, directly affect paddy irrigation and its management schemes. Previous studies show that potential water stresses were estimated in the framework of grid-based distributed water circulation models, in which water availability and demand were roughly compared in large-scale grids of 10~100km. However, in mid and small-scale basins, where we carry out impact assessment studies of 1~10km grids, we need schemes to couple the irrigation intake and its allocation, because agricultural water is highly dependent on human decision making processes. Then, we have developed a model that couples natural hydrological behaviors of a basin and artificial irrigation systems. A distributed water circulation model, which explains natural hydrological behaviors of a basin, consists of approximately 1km square gridded meshes. Infiltration and saturation-excess flow and water requirements of irrigated paddy fields on any grid are calculated. The generated surface flow is routed by a kinematic wave equation so that daily flow rate can be calculated at any point of interest. The core of the model is water allocation and management scheme that exploit the spatial database of irrigation facilities and beneficiary areas. This analysis consists of new modeled plane for irrigation, which is calculated independently from the surface plain of the distributed water circulation model. Following the configuration of the water allocation and management schemes, the model is coupled with the distributed water circulation model. The reservoir operation scheme is an algorithm to determine the reservoir releases for irrigation based on requirement and flow rate at downstream diversion weirs. Diversion weirs intake water from associated rivers at the maximum rate, if water is available. The integrated

  5. Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA)

    NASA Technical Reports Server (NTRS)

    Lichtwardt, Jonathan; Paciano, Eric; Jameson, Tina; Fong, Robert; Marshall, David

    2012-01-01

    With the very recent advent of NASA's Environmentally Responsible Aviation Project (ERA), which is dedicated to designing aircraft that will reduce the impact of aviation on the environment, there is a need for research and development of methodologies to minimize fuel burn, emissions, and reduce community noise produced by regional airliners. ERA tackles airframe technology, propulsion technology, and vehicle systems integration to meet performance objectives in the time frame for the aircraft to be at a Technology Readiness Level (TRL) of 4-6 by the year of 2020 (deemed N+2). The proceeding project that investigated similar goals to ERA was NASA's Subsonic Fixed Wing (SFW). SFW focused on conducting research to improve prediction methods and technologies that will produce lower noise, lower emissions, and higher performing subsonic aircraft for the Next Generation Air Transportation System. The work provided in this investigation was a NASA Research Announcement (NRA) contract #NNL07AA55C funded by Subsonic Fixed Wing. The project started in 2007 with a specific goal of conducting a large-scale wind tunnel test along with the development of new and improved predictive codes for the advanced powered-lift concepts. Many of the predictive codes were incorporated to refine the wind tunnel model outer mold line design. The large scale wind tunnel test goal was to investigate powered lift technologies and provide an experimental database to validate current and future modeling techniques. Powered-lift concepts investigated were Circulation Control (CC) wing in conjunction with over-the-wing mounted engines to entrain the exhaust to further increase the lift generated by CC technologies alone. The NRA was a five-year effort; during the first year the objective was to select and refine CESTOL concepts and then to complete a preliminary design of a large-scale wind tunnel model for the large scale test. During the second, third, and fourth years the large-scale wind

  6. A global multiscale mathematical model for the human circulation with emphasis on the venous system.

    PubMed

    Müller, Lucas O; Toro, Eleuterio F

    2014-07-01

    We present a global, closed-loop, multiscale mathematical model for the human circulation including the arterial system, the venous system, the heart, the pulmonary circulation and the microcirculation. A distinctive feature of our model is the detailed description of the venous system, particularly for intracranial and extracranial veins. Medium to large vessels are described by one-dimensional hyperbolic systems while the rest of the components are described by zero-dimensional models represented by differential-algebraic equations. Robust, high-order accurate numerical methodology is implemented for solving the hyperbolic equations, which are adopted from a recent reformulation that includes variable material properties. Because of the large intersubject variability of the venous system, we perform a patient-specific characterization of major veins of the head and neck using MRI data. Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins, validation is carried out through a detailed comparison of simulation results against patient-specific phase-contrast MRI flow quantification data. A merit of our model is its global, closed-loop character; the imposition of highly artificial boundary conditions is avoided. Applications in mind include a vast range of medical conditions. Of particular interest is the study of some neurodegenerative diseases, whose venous haemodynamic connection has recently been identified by medical researchers. PMID:24431098

  7. Reconciling the observed and modeled Southern Hemisphere circulation response to volcanic eruptions

    NASA Astrophysics Data System (ADS)

    McGraw, Marie C.; Barnes, Elizabeth A.; Deser, Clara

    2016-07-01

    Confusion exists regarding the tropospheric circulation response to volcanic eruptions, with models and observations seeming to disagree on the sign of the response. The forced Southern Hemisphere circulation response to the eruptions of Pinatubo and El Chichón is shown to be a robust positive annular mode, using over 200 ensemble members from 38 climate models. It is demonstrated that the models and observations are not at odds, but rather, internal climate variability is large and can overwhelm the forced response. It is further argued that the state of the El Niño-Southern Oscillation can at least partially explain the sign of the observed anomalies and may account for the perceived discrepancy between model and observational studies. The eruptions of both El Chichón and Pinatubo occurred during El Niño events, and it is demonstrated that the Southern Annular Mode anomalies following volcanic eruptions are weaker during El Niño events compared to La Niña events.

  8. A global multiscale mathematical model for the human circulation with emphasis on the venous system.

    PubMed

    Müller, Lucas O; Toro, Eleuterio F

    2014-07-01

    We present a global, closed-loop, multiscale mathematical model for the human circulation including the arterial system, the venous system, the heart, the pulmonary circulation and the microcirculation. A distinctive feature of our model is the detailed description of the venous system, particularly for intracranial and extracranial veins. Medium to large vessels are described by one-dimensional hyperbolic systems while the rest of the components are described by zero-dimensional models represented by differential-algebraic equations. Robust, high-order accurate numerical methodology is implemented for solving the hyperbolic equations, which are adopted from a recent reformulation that includes variable material properties. Because of the large intersubject variability of the venous system, we perform a patient-specific characterization of major veins of the head and neck using MRI data. Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins, validation is carried out through a detailed comparison of simulation results against patient-specific phase-contrast MRI flow quantification data. A merit of our model is its global, closed-loop character; the imposition of highly artificial boundary conditions is avoided. Applications in mind include a vast range of medical conditions. Of particular interest is the study of some neurodegenerative diseases, whose venous haemodynamic connection has recently been identified by medical researchers.

  9. Coupling of river flow and inundation analysis in a distributed water circulation model

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Masumoto, T.; Horikawa, N.

    2011-12-01

    The increasing recognition of the importance of inundation hazards has stimulated recent progress in distributed hydrological models in analyzing flood inundation with basin-scale hydrological cycles. One of the major handicaps facing inundation analysis, however, is the lack of precise topographical and river course data to describe inundated areas especially in low-lying areas in developing countries. On the other hand, high-resolution raster Digital Elevation Models, which are becoming available on a global scale, provide practical information on detailed topographical features in grid-cells of distributed hydrological models. In this study, we developed a model of inundation process integrated with a basin-scale distributed hydrological model that incorporates a sub-model of cropping area and agricultural water use analysis. First, we configured a distributed water circulation model. The model was based on grid-cells of approximately 2 km, each of which consisted of 3 soil layers for runoff calculation. The surface flow model consists of a one-dimensional kinematic wave approximation of channel flow and a simple representation of inundated area. In addition to calculation of river discharges, the model explicitly represents water cycles in paddy areas, which enables us to assess cropping situation in the basin. The procedure applied to assess the flood hazard uses simple model that assumes the inundated area is a reservoir, in which water levels for the inundation in the surrounding areas are equivalent. Because the inundated area is almost flat, no active flood movement is assumed in the inundated area. The inundated volume is calculated with a continuous equation with H-V relations in the area, in which excess rate of surface flow above the maximum capacity of conveyance of rivers is input by utilization the distributed water circulation model. To apply this inundation model, we used ASTER GDEM. We applied the model to the Xebanfai River in the Laos PDR

  10. Upper-Ocean Heat Balance Processes and the Walker Circulation in CMIP5 Model Projections

    NASA Technical Reports Server (NTRS)

    Robertson, F. R.; Roberts, J. B.; Funk, C.; Lyon, B.; Ricciardulli, L.

    2012-01-01

    Considerable uncertainty remains as to the importance of mechanisms governing decadal and longer variability of the Walker Circulation, its connection to the tropical climate system, and prospects for tropical climate change in the face of anthropogenic forcing. Most contemporary climate models suggest that in response to elevated CO2 and a warmer but more stratified atmosphere, the required upward mass flux in tropical convection will diminish along with the Walker component of the tropical mean circulation as well. Alternatively, there is also evidence to suggest that the shoaling and increased vertical stratification of the thermocline in the eastern Pacific will enable a muted SST increase there-- preserving or even enhancing some of the dynamical forcing for the Walker cell flow. Over the past decade there have been observational indications of an acceleration in near-surface easterlies, a strengthened Pacific zonal SST gradient, and globally-teleconnected dislocations in precipitation. But is this evidence in support of an ocean dynamical thermostat process posited to accompany anthropogenic forcing, or just residual decadal fluctuations associated with variations in warm and cold ENSO events and other stochastic forcing? From a modeling perspective we try to make headway on this question by examining zonal variations in surface energy fluxes and dynamics governing tropical upper ocean heat content evolution in the WCRP CMIP5 model projections. There is some diversity among model simulations; for example, the CCSM4 indicates net ocean warming over the IndoPacific region while the CSIRO model concentrates separate warming responses over the central Pacific and Indian Ocean regions. The models, as with observations, demonstrate strong local coupling between variations in column water vapor, downward surface longwave radiation and SST; but the spatial patterns of changes in the sign of this relationship differ among models and, for models as a whole, with

  11. A Transient Model of Induced Natural Circulation Thermal Cycling for Hydrogen Isotope Separation

    SciTech Connect

    SHADDAY, MARTIN

    2005-07-12

    The property of selective temperature dependence of adsorption and desorption of hydrogen isotopes by palladium is used for isotope separation. A proposal to use natural circulation of nitrogen to alternately heat and cool a packed bed of palladium coated beads is under active investigation, and a device consisting of two interlocking natural convection loops is being designed. A transient numerical model of the device has been developed to aid the design process. It is a one-dimensional finite-difference model, using the Boussinesq approximation. The thermal inertia of the pipe walls and other heat structures as well as the heater control logic is included in the model. Two system configurations were modeled and results are compared.

  12. Modified graphical autocatalytic set model of combustion process in circulating fluidized bed boiler

    NASA Astrophysics Data System (ADS)

    Yusof, Nurul Syazwani; Bakar, Sumarni Abu; Ismail, Razidah

    2014-07-01

    Circulating Fluidized Bed Boiler (CFB) is a device for generating steam by burning fossil fuels in a furnace operating under a special hydrodynamic condition. Autocatalytic Set has provided a graphical model of chemical reactions that occurred during combustion process in CFB. Eight important chemical substances known as species were represented as nodes and catalytic relationships between nodes are represented by the edges in the graph. In this paper, the model is extended and modified by considering other relevant chemical reactions that also exist during the process. Catalytic relationship among the species in the model is discussed. The result reveals that the modified model is able to gives more explanation of the relationship among the species during the process at initial time t.

  13. Two-Layer Variable Infiltration Capacity Land Surface Representation for General Circulation Models

    NASA Technical Reports Server (NTRS)

    Xu, L.

    1994-01-01

    A simple two-layer variable infiltration capacity (VIC-2L) land surface model suitable for incorporation in general circulation models (GCMs) is described. The model consists of a two-layer characterization of the soil within a GCM grid cell, and uses an aerodynamic representation of latent and sensible heat fluxes at the land surface. The effects of GCM spatial subgrid variability of soil moisture and a hydrologically realistic runoff mechanism are represented in the soil layers. The model was tested using long-term hydrologic and climatalogical data for Kings Creek, Kansas to estimate and validate the hydrological parameters. Surface flux data from three First International Satellite Land Surface Climatology Project Field Experiments (FIFE) intensive field compaigns in the summer and fall of 1987 in central Kansas, and from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) in Brazil were used to validate the mode-simulated surface energy fluxes and surface temperature.

  14. Space-time spectral structure of a GLAS general circulation model and a comparison with observations

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Shukla, J.

    1981-01-01

    The wavenumber-frequency spectra of geopotential height computed from a winter simulation of a general circulation model are compared with the observed winter spectra averaged over 15 winters. The space and time scales studied include: (1) stationary planetary waves; (2) stationary synoptic-scale waves; (3) low-frequency planetary waves; (4) low frequency synoptic-scale waves; (5) medium-frequency planetary waves; and (6) medium frequency synoptic-scale waves. Variances in these categories are presented and their distributions with latitude and height are discussed.

  15. Orthotopic mouse models of tumor metastasis expressing fluorescent reporters produce imageable circulating tumor cells.

    PubMed

    Hoffman, Robert M

    2014-12-01

    Circulating tumor cells (CTC) are of high importance, since they are potential metastatic precursors and are readily available for prognostic analysis and treatment testing. In this review, we demonstrate the great power that green fluorescent protein (GFP) labeling and orthotopic mouse models of cancer confer to the study of CTCs for isolation and characterization, including metastatic testing in mice and the chick embryo as well as drug response testing in vitro. We also describe a facile method to label patient CTCs ex vivo using a telomerase-expressing GFP-containing adenovirus that will allow the CTC studies described in this review to be translated clinically.

  16. Mars atmospheric dynamics as simulated by the NASA AMES General Circulation Model. II - Transient baroclinic eddies

    NASA Astrophysics Data System (ADS)

    Barnes, J. R.; Pollack, J. B.; Haberle, R. M.; Leovy, C. B.; Zurek, R. W.; Lee, H.; Schaeffer, J.

    1993-02-01

    A large set of experiments performed with the NASA Ames Mars General Circulation Model is analyzed to determine the properties, structure, and dynamics of the simulated transient baroclinic eddies. There is strong transient baroclinic eddy activity in the extratropics of the Northern Hemisphere during the northern autumn, winter, and spring seasons. The eddy activity remains strong for very large dust loadings, though it shifts northward. The eastward propagating eddies are characterized by zonal wavenumbers of 1-4 and periods of about 2-10 days. The properties of the GCM baroclinic eddies in the northern extratropics are compared in detail with analogous properties inferred from Viking Lander meteorology observations.

  17. Computational design of the basic dynamical processes of the UCLA general circulation model

    NASA Technical Reports Server (NTRS)

    Arakawa, A.; Lamb, V. R.

    1977-01-01

    The 12-layer UCLA general circulation model encompassing troposphere and stratosphere (and superjacent 'sponge layer') is described. Prognostic variables are: surface pressure, horizontal velocity, temperature, water vapor and ozone in each layer, planetary boundary layer (PBL) depth, temperature, moisture and momentum discontinuities at PBL top, ground temperature and water storage, and mass of snow on ground. Selection of space finite-difference schemes for homogeneous incompressible flow, with/without a free surface, nonlinear two-dimensional nondivergent flow, enstrophy conserving schemes, momentum advection schemes, vertical and horizontal difference schemes, and time differencing schemes are discussed.

  18. 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.

  19. Technical Report Series on Global Modeling and Data Assimilation. Volume 16; Filtering Techniques on a Stretched Grid General Circulation Model

    NASA Technical Reports Server (NTRS)

    Takacs, Lawrence L.; Sawyer, William; Suarez, Max J. (Editor); Fox-Rabinowitz, Michael S.

    1999-01-01

    This report documents the techniques used to filter quantities on a stretched grid general circulation model. Standard high-latitude filtering techniques (e.g., using an FFT (Fast Fourier Transformations) to decompose and filter unstable harmonics at selected latitudes) applied on a stretched grid are shown to produce significant distortions of the prognostic state when used to control instabilities near the pole. A new filtering technique is developed which accurately accounts for the non-uniform grid by computing the eigenvectors and eigenfrequencies associated with the stretching. A filter function, constructed to selectively damp those modes whose associated eigenfrequencies exceed some critical value, is used to construct a set of grid-spaced weights which are shown to effectively filter without distortion. Both offline and GCM (General Circulation Model) experiments are shown using the new filtering technique. Finally, a brief examination is also made on the impact of applying the Shapiro filter on the stretched grid.

  20. Discussion on climate oscillations: CMIP5 general circulation models versus a semi-empirical harmonic model based on astronomical cycles

    NASA Astrophysics Data System (ADS)

    Scafetta, Nicola

    2013-11-01

    Power spectra of global surface temperature (GST) records (available since 1850) reveal major periodicities at about 9.1, 10-11, 19-22 and 59-62 years. Equivalent oscillations are found in numerous multisecular paleoclimatic records. The Coupled Model Intercomparison Project 5 (CMIP5) general circulation models (GCMs), to be used in the IPCC Fifth Assessment Report (AR5, 2013), are analyzed and found not able to reconstruct this variability. In particular, from 2000 to 2013.5 a GST plateau is observed while the GCMs predicted a warming rate of about 2 °C/century. In contrast, the hypothesis that the climate is regulated by specific natural oscillations more accurately fits the GST records at multiple time scales. For example, a quasi 60-year natural oscillation simultaneously explains the 1850-1880, 1910-1940 and 1970-2000 warming periods, the 1880-1910 and 1940-1970 cooling periods and the post 2000 GST plateau. This hypothesis implies that about 50% of the ~ 0.5 °C global surface warming observed from 1970 to 2000 was due to natural oscillations of the climate system, not to anthropogenic forcing as modeled by the CMIP3 and CMIP5 GCMs. Consequently, the climate sensitivity to CO2 doubling should be reduced by half, for example from the 2.0-4.5 °C range (as claimed by the IPCC, 2007) to 1.0-2.3 °C with a likely median of ~ 1.5 °C instead of ~ 3.0 °C. Also modern paleoclimatic temperature reconstructions showing a larger preindustrial variability than the hockey-stick shaped temperature reconstructions developed in early 2000 imply a weaker anthropogenic effect and a stronger solar contribution to climatic changes. The observed natural oscillations could be driven by astronomical forcings. The ~ 9.1 year oscillation appears to be a combination of long soli-lunar tidal oscillations, while quasi 10-11, 20 and 60 year oscillations are typically found among major solar and heliospheric oscillations driven mostly by Jupiter and Saturn movements. Solar models based

  1. Mixed boundary conditions in ocean general circulation models and their influence on the stability of the model`s conveyor belt

    SciTech Connect

    Mikolajewicz, U.; Maier-reimer, E.

    1994-11-01

    When driven under `mixed boundary conditions` coarse resolution ocean general circulation models (OGCMs) generally show a high sensitivity of the present-day thermohaline circulation against perturbations. We will show that an alternative formulation of the boundary condition for temperature, a mixture of prescribed heat fluxes and additional restoring of the sea surface temperature to a climatological boundary temperature with a longer time constant, drastically alters the stability of the modes of the thermohaline circulation. The results from simulations with the Hamburg large-scale geostrophic OGCM indicate that the stability of the mode of the thermohaline circulation with formation of North Atlantic deepwater increases, if the damping of sea surface temperature anomalies is reduced, whereas the opposite is true for the mode without North Atlantic deep water formation. It turns out that the formulation of the temperature boundary condition also affects the variability of the model.

  2. 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.

  3. Constraining a Martian general circulation model with the MAVEN/IUVS observations in the thermosphere

    NASA Astrophysics Data System (ADS)

    Moeckel, Chris; Medvedev, Alexander; Nakagawa, Hiromu; Evans, Scott; Kuroda, Takeshi; Hartogh, Paul; Yiğit, Erdal; Jain, Sonal; Lo, Daniel; Schneider, Nicholas M.; Jakosky, Bruce

    2016-10-01

    The recent measurements of the number density of atomic oxygen by Mars Atmosphere and Volatile EvolutioN/ Imaging UltraViolet Spectrograph (MAVEN/IUVS) have been implemented for the first time into a global circulation model to quantify the effect on the Martian thermosphere. The number density has been converted to 1D volume mixing ratio and this profile is compared to the atomic oxygen scenarios based on chemical models. Simulations were performed with the Max Planck Institute Martian General Circulation Model (MPI-MGCM). The simulations closely emulate the conditions at the time of observations. The results are compared to the IUVS-measured CO2 number density and temperature above 130 km to gain knowledge of the processes in the upper atmosphere and further constrain them in MGCMs. The presentation will discuss the role and importance in the thermosphere of the following aspects: (a) impact of the observed atomic oxygen, (b) 27-day solar cycle variations, (c) varying dust load in the lower atmosphere, and (d) gravity waves.

  4. Model representation of salinity anomalies and the stability of the North Atlantic overturning circulation

    NASA Astrophysics Data System (ADS)

    Megann, A.; New, A.; Blaker, A.

    2012-04-01

    Vellinga and Wu (2004) and others have identified feedback cycles governing the decadal variability of the North Atlantic overturning circulation, in which modulation of tropical rainfall creates near-surface salinity anomalies that propagate northward to the winter convection regions, where they affect the wintertime convection through changes in surface density. Freshwater "hosing" experiments, in which 0.1 Sv of extra freshwater is added to the convection region, are described using two climate models: the UK Met Office's HadCM3; and CHIME, which is identical to HadCM3 except for the replacement of the z-coordinate ocean component of HadCM3 with the hybrid isopycnic model HYCOM. While HadCM3 shows an unambiguous weakening of the meridional overturning circulation (MOC) by 5 Sv, the MOC in CHIME initially starts to decrease but returns to a value close to that in the control experiment after 40-50 years even though the hosing flux is still being applied. It will be shown that the recovery of the overturning in CHIME is mainly due to enhanced advective transport of salt from the subtropics by salinity anomalies. These are found to be substantially more coherent meridionally in CHIME than in HadCM3, consistent with the known superior ability of the isopycnic model formulation to preserve watermass properties over long distances.

  5. Snowline instability in a general circulation model: application to Carboniferous glaciation

    SciTech Connect

    Crowley, T.J.; Yip, Kuor-Kier, J.; Baum, S.K.

    1994-11-01

    For over twenty years it has been known that energy balance models (EBMs) with snow-albedo feedback are characterized by unstable behavior in some areas of parameter space. This behaviour leads to rapid changes in snow area due to small changes in forcing, and has been termed the small ice cap instability (SICI). It has never been clarified whether this behaviour reflects a real feature of the climate system or a limitation in EBMs. In this study we demonstrate that evidence for similar unstable behavior can also be found in an atmospheric general circulation model (GCM), using a realistic set of boundary conditions for the Carboniferous (300 Ma), one of the most extensive periods of glaciation in Earth history. When solar luminosity is sequentially lowered to near values appropriate for the Carboniferous, there is a discontinuous increase in summer snow area. The instability occurs in approximately the same area of parameter space as one previously found in an EBM. Analysis of selected fields indicates that the circulation is primarily affected in the area of snow increase; far-field effects are minimal. There is good agreement between model-generated summer snowcover and one reconstruction of Carboniferous ice cover. Although more work is required on this topic, our results provide increased support for the possibility that the snowline instability represents a real feature of the climate system, and that it may help explain some cases of glacial inception and abrupt transitions in Earth history. 63 refs., 20 figs.

  6. Integrated cumulus ensemble and turbulence (ICET): An integrated parameterization system for general circulation models (GCMs)

    SciTech Connect

    Evans, J.L.; Frank, W.M.; Young, G.S.

    1996-04-01

    Successful simulations of the global circulation and climate require accurate representation of the properties of shallow and deep convective clouds, stable-layer clouds, and the interactions between various cloud types, the boundary layer, and the radiative fluxes. Each of these phenomena play an important role in the global energy balance, and each must be parameterized in a global climate model. These processes are highly interactive. One major problem limiting the accuracy of parameterizations of clouds and other processes in general circulation models (GCMs) is that most of the parameterization packages are not linked with a common physical basis. Further, these schemes have not, in general, been rigorously verified against observations adequate to the task of resolving subgrid-scale effects. To address these problems, we are designing a new Integrated Cumulus Ensemble and Turbulence (ICET) parameterization scheme, installing it in a climate model (CCM2), and evaluating the performance of the new scheme using data from Atmospheric Radiation Measurement (ARM) Program Cloud and Radiation Testbed (CART) sites.

  7. Improved short-term variability in the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model

    NASA Astrophysics Data System (ADS)

    Häusler, K.; Hagan, M. E.; Baumgaertner, A. J. G.; Maute, A.; Lu, G.; Doornbos, E.; Bruinsma, S.; Forbes, J. M.; Gasperini, F.

    2014-08-01

    We report on a new source of tidal variability in the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM). Lower boundary forcing of the TIME-GCM for a simulation of November-December 2009 based on 3-hourly Modern-Era Retrospective Analysis for Research and Application (MERRA) reanalysis data includes day-to-day variations in both diurnal and semidiurnal tides of tropospheric origin. Comparison with TIME-GCM results from a heretofore standard simulation that includes climatological tropospheric tides from the global-scale wave model reveal evidence of the impacts of MERRA forcing throughout the model domain, including measurable tidal variability in the TIME-GCM upper thermosphere. Additional comparisons with measurements made by the Gravity field and steady-state Ocean Circulation Explorer satellite show improved TIME-GCM capability to capture day-to-day variations in thermospheric density for the November-December 2009 period with the new MERRA lower boundary forcing.

  8. Tidally averaged circulation in Puget Sound sub-basins: Comparison of historical data, analytical model, and numerical model

    SciTech Connect

    Khangaonkar, Tarang; Yang, Zhaoqing; Kim, Tae Yun; Roberts, Mindy

    2011-07-20

    Through extensive field data collection and analysis efforts conducted since the 1950s, researchers have established an understanding of the characteristic features of circulation in Puget Sound. The pattern ranges from the classic fjordal behavior in some basins, with shallow brackish outflow and compensating inflow immediately below, to the typical two-layer flow observed in many partially mixed estuaries with saline inflow at depth. An attempt at reproducing this behavior by fitting an analytical formulation to past data is presented, followed by the application of a three-dimensional circulation and transport numerical model. The analytical treatment helped identify key physical processes and parameters, but quickly reconfirmed that response is complex and would require site-specific parameterization to include effects of sills and interconnected basins. The numerical model of Puget Sound, developed using unstructured-grid finite volume method, allowed resolution of the sub-basin geometric features, including presence of major islands, and site-specific strong advective vertical mixing created by bathymetry and multiple sills. The model was calibrated using available recent short-term oceanographic time series data sets from different parts of the Puget Sound basin. The results are compared against (1) recent velocity and salinity data collected in Puget Sound from 2006 and (2) a composite data set from previously analyzed historical records, mostly from the 1970s. The results highlight the ability of the model to reproduce velocity and salinity profile characteristics, their variations among Puget Sound subbasins, and tidally averaged circulation. Sensitivity of residual circulation to variations in freshwater inflow and resulting salinity gradient in fjordal sub-basins of Puget Sound is examined.

  9. AFDM: An Advanced Fluid-Dynamics Model

    SciTech Connect

    Bohl, W.R.; Parker, F.R. ); Wilhelm, D. . Inst. fuer Neutronenphysik und Reaktortechnik); Berthier, J. ); Goutagny, L. . Inst. de Protection et de Surete Nucleaire); Ninokata,

    1990-09-01

    AFDM, or the Advanced Fluid-Dynamics Model, is a computer code that investigates new approaches simulating the multiphase-flow fluid-dynamics aspects of severe accidents in fast reactors. The AFDM formalism starts with differential equations similar to those in the SIMMER-II code. These equations are modified to treat three velocity fields and supplemented with a variety of new models. The AFDM code has 12 topologies describing what material contacts are possible depending on the presence or absence of a given material in a computational cell, on the dominant liquid, and on the continuous phase. Single-phase, bubbly, churn-turbulent, cellular, and dispersed flow regimes are permitted for the pool situations modeled. Virtual mass terms are included for vapor in liquid-continuous flow. Interfacial areas between the continuous and discontinuous phases are convected to allow some tracking of phenomenological histories. Interfacial areas are also modified by models of nucleation, dynamic forces, turbulence, flashing, coalescence, and mass transfer. Heat transfer is generally treated using engineering correlations. Liquid-vapor phase transitions are handled with the nonequilibrium, heat-transfer-limited model, whereas melting and freezing processes are based on equilibrium considerations. Convection is treated using a fractional-step method of time integration, including a semi-implicit pressure iteration. A higher-order differencing option is provided to control numerical diffusion. The Los Alamos SESAME equation-of-state has been implemented using densities and temperatures as the independent variables. AFDM programming has vectorized all computational loops consistent with the objective of producing an exportable code. 24 refs., 4 figs.

  10. Nonlinear Dynamic Models in Advanced Life Support

    NASA Technical Reports Server (NTRS)

    Jones, Harry

    2002-01-01

    To facilitate analysis, ALS systems are often assumed to be linear and time invariant, but they usually have important nonlinear and dynamic aspects. Nonlinear dynamic behavior can be caused by time varying inputs, changes in system parameters, nonlinear system functions, closed loop feedback delays, and limits on buffer storage or processing rates. Dynamic models are usually cataloged according to the number of state variables. The simplest dynamic models are linear, using only integration, multiplication, addition, and subtraction of the state variables. A general linear model with only two state variables can produce all the possible dynamic behavior of linear systems with many state variables, including stability, oscillation, or exponential growth and decay. Linear systems can be described using mathematical analysis. Nonlinear dynamics can be fully explored only by computer simulations of models. Unexpected behavior is produced by simple models having only two or three state variables with simple mathematical relations between them. Closed loop feedback delays are a major source of system instability. Exceeding limits on buffer storage or processing rates forces systems to change operating mode. Different equilibrium points may be reached from different initial conditions. Instead of one stable equilibrium point, the system may have several equilibrium points, oscillate at different frequencies, or even behave chaotically, depending on the system inputs and initial conditions. The frequency spectrum of an output oscillation may contain harmonics and the sums and differences of input frequencies, but it may also contain a stable limit cycle oscillation not related to input frequencies. We must investigate the nonlinear dynamic aspects of advanced life support systems to understand and counter undesirable behavior.

  11. Using Green's Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model

    NASA Astrophysics Data System (ADS)

    Brix, H.; Menemenlis, D.; Hill, C.; Dutkiewicz, S.; Jahn, O.; Wang, D.; Bowman, K.; Zhang, H.

    2015-11-01

    The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas

  12. The zonally averaged transport characteristics of the atmosphere as determined by a general circulation model

    NASA Technical Reports Server (NTRS)

    Plumb, R. A.

    1985-01-01

    Two dimensional modeling has become an established technique for the simulation of the global structure of trace constituents. Such models are simpler to formulate and cheaper to operate than three dimensional general circulation models, while avoiding some of the gross simplifications of one dimensional models. Nevertheless, the parameterization of eddy fluxes required in a 2-D model is not a trivial problem. This fact has apparently led some to interpret the shortcomings of existing 2-D models as indicating that the parameterization procedure is wrong in principle. There are grounds to believe that these shortcomings result primarily from incorrect implementations of the predictions of eddy transport theory and that a properly based parameterization may provide a good basis for atmospheric modeling. The existence of these GCM-derived coefficients affords an unprecedented opportunity to test the validity of the flux-gradient parameterization. To this end, a zonally averaged (2-D) model was developed, using these coefficients in the transport parameterization. Results from this model for a number of contrived tracer experiments were compared with the parent GCM. The generally good agreement substantially validates the flus-gradient parameterization, and thus the basic principle of 2-D modeling.

  13. Electrodynamic effects of thermospheric winds from the NCAR thermospheric general circulation model

    SciTech Connect

    Richmond, A.D.; Roble, R.G.

    1987-11-01

    The ionospheric electric fields and currents and the associated ground magnetic variations, generated by the dynamo action of winds simulated with the National Center for Atmospheric Research, Boulder, Colo. (NCAR) Thermospheric General Circulation Model (TGCM), are modelled and compared with observations for equinox solar minimum conditions. The dynamo model uses a tilted dipole geomagnetic field and allows for field-aligned current flow between conjugate points, but no magnetospheric dynamo effects are included. Two TGCM wind simulations are used, one of which is driven only by in situ solar ultraviolet heating and the other of which includes lower boundary forcing that mimics the effects of upward propagating semidiurnal tides, as described by Fesen et al. (1986). Without tidal forcing, the TGCM winds produce ground magnetic variations that have the general pattern of observed Sq variations but are only about half as strong.

  14. The January and July performance of the OSU two-level atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Schlesinger, M. E.; Gates, W. L.

    1980-01-01

    A modified version of the two-level atmospheric general circulation model has been developed and employed in the simulation of January and July global climates. The overall physical and numerical formation of the Oregon State University model is the same as that described by Gates and Schlesinger (1977), but in the new version water vapor at the upper level has been made a prognostic variable, the parameterizations of cumulus convection, large-scale condensation and evaporation, clouds, and radiative transfer have been changed, the surface snow mass and ground temperature have been made prognostic variables, and the treatment of the surface boundary layer has been revised. It is found that the model simulates most features of the large-scale distributions of observed January and July climate more accurately than before.

  15. A search for short-term meteorological effects of solar variability in an atmospheric circulation model

    NASA Technical Reports Server (NTRS)

    Somerville, R. C. J.; Quirk, W. J.; Hansen, J. E.; Lacis, A. A.; Stone, P. H.

    1976-01-01

    A set of numerical experiments is carried out to test the short-range sensitivity of the Goddard Institute for Space Studies global atmospheric general-circulation model to changes in solar constant and ozone amount. These experiments consist of forecasts initiated with actual atmospheric data. One set of forecasts is made with a standard version of the model; another set uses the model modified by very different values of the solar constant (two-thirds and three-halves of the standard value) and of the ozone amount (zero and twice the standard amount). Twelve-day integrations with these very large variations show such small effects that the effects of realistic variations would almost certainly be insignificant meteorologically on this time scale.

  16. Aggregation of wet and dry land surfaces in interception schemes for general circulation models

    SciTech Connect

    Taylor, C.

    1995-03-01

    This paper investigates the parameterization of rainfall interception by a vegetation canopy in general circulation models (GCMs). Recent land surface schemes have introduced canopy water balance equations, which include sub-grid scale rainfall variability. However, current models do not distinguish between wet and dry areas when solving the set of energy balance equations. An alternative method is set out here that solves one set of surface flux equations for the wet area and one for the dry area. The approximation of using a single surface temperature to determine the surface fluxes is shown to overestimate the wet canopy evaporation from a forest by typically 30%. When implemented in the single column version of the U.K. Meteorological Office (UKMO) GCM, this excessive evaporation leads to significant overprediction of modeled interception loss from Amazonian rain forest.

  17. Interpretation of snow-climate feedback as produced by 17 general circulation models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M.-H.; Potter, G. L.; Blanchet, J.-P.; Chalita, S.; Colman, R.; Dazlich, D. A.; Del Genio, A. D.; Lacis, A. A.; Dymnikov, V.

    1991-01-01

    Snow feedback is expected to amplify global warming caused by increasing concentrations of atmospheric greenhouse gases. The conventional explanation is that a warmer earth will have less snow cover, resulting in a darker planet that absorbs more solar radiation. An intercomparison of 17 general circulation models, for which perturbations of sea surface temperature were used as a surrogate climate change, suggests that this explanation is overly simplistic. The results instead indicate that additional amplification or moderation may be caused both by cloud interactions and longwave radiation. One measure of this net effect of snow feedback was found to differ markedly among the 17 climate models, ranging from weak negative feedback in some models to strong positive feedback in others.

  18. A three-dimensional, finite element model for coastal and estuarine circulation

    USGS Publications Warehouse

    Walters, R.A.

    1992-01-01

    This paper describes the development and application of a three-dimensional model for coastal and estuarine circulation. The model uses a harmonic expansion in time and a finite element discretization in space. All nonlinear terms are retained, including quadratic bottom stress, advection and wave transport (continuity nonlinearity). The equations are solved as a global and a local problem, where the global problem is the solution of the wave equation formulation of the shallow water equations, and the local problem is the solution of the momentum equation for the vertical velocity profile. These equations are coupled to the advection-diffusion equation for salt so that density gradient forcing is included in the momentum equations. The model is applied to a study of Delaware Bay, U.S.A., where salinity intrusion is the primary focus. ?? 1991.

  19. Parameterization of the evaporation of rainfall for use in general circulation models

    SciTech Connect

    Feingold, G. )

    1993-10-15

    A parameterization of evaporation losses below cloud base is presented for use in general circulation models to assist in quantification of water content in the hydrological cycle. The scheme is based on detailed model calculations of the evolution of raindrop spectra below cloud base and includes the processes of collision coalescence/breakup. Evaporation is expressed as a percentage decrease in the liquid water ;mixing ratio, and the parameterization is formulated as an algebraic equation in (i) the cloud-base values o the mixing ratio and the drop concentration, (ii) the fall distance, and (iii) the lapse rate of temperature in the subcloud environment. Results show that when compared to the detailed model calculations, good estimates of evaporation (usually within 20% and often within 10%) are obtained for a wide range of conditions. An analysis of the errors in evaporation calculations associated with errors in the parameterization variables is performed. 29 refs., 34 figs., 3 tabs.

  20. Surface Lander Missions to Mars: Support via Analysis of the NASA Ames Mars General Circulation Model

    NASA Technical Reports Server (NTRS)

    Murphy, James R.; Bridger, Alison F.C.; Haberle, Robert M.

    1997-01-01

    We have characterized the near-surface martian wind environment as calculated with a set of numerical simulations carried out with the NASA Ames Mars General Circulation Model (Mars GCM). These wind environments are intended to offer future spacecraft missions to the martian surface a data base from which to choose those locations which meet the mission's criteria for minimal near surface winds to enable a successful landing. We also became involved in the development and testing of the wind sensor which is currently onboard the Mars-bound Pathfinder lander. We began this effort with a comparison of Mars GCM produced winds with those measured by the Viking landers during their descent through the martian atmosphere and their surface wind measurements during the 3+ martian year lifetime of the mission. Unexpected technical difficulties in implementing the sophisticated Planetary Boundary Layer (PBL) scheme of Haberle et al. (1993) within the Mars GCM precluded our carrying out this investigation with the desired improvement to the model's treatment of the PBL. Thus, our results from this effort are not as conclusive as we had anticipated. As it turns out, similar difficulties have been experienced by other Mars modelling groups in attempting to implement very similar PBL routines into their GCMs (Mars General Circulation Model Intercomparison Workshop, held at Oxford University, United Kingdom, July 22-24, 1996; organized by J. Murphy, J. Hollingsworth, M. Joshi). These problems, which arise due to the nature of the time stepping in each of the models, are near to being resolved at the present. The model discussions which follow herein are based upon results using the existing, less sophisticated PBL routine. We fully anticipate implementing the tools we have developed in the present effort to investigate GCM results with the new PBL scheme implemented, and thereafter producing the technical document detailing results from the analysis tools developed during this

  1. Advanced Combustion Modeling for Complex Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Ham, Frank Stanford

    2005-01-01

    The next generation of aircraft engines will need to pass stricter efficiency and emission tests. NASA's Ultra-Efficient Engine Technology (UEET) program has set an ambitious goal of 70% reduction of NO(x) emissions and a 15% increase in fuel efficiency of aircraft engines. We will demonstrate the state-of-the-art combustion tools developed a t Stanford's Center for Turbulence Research (CTR) as part of this program. In the last decade, CTR has spear-headed a multi-physics-based combustion modeling program. Key technologies have been transferred to the aerospace industry and are currently being used for engine simulations. In this demo, we will showcase the next-generation combustion modeling tools that integrate a very high level of detailed physics into advanced flow simulation codes. Combustor flows involve multi-phase physics with liquid fuel jet breakup, evaporation, and eventual combustion. Individual components of the simulation are verified against complex test cases and show excellent agreement with experimental data.

  2. Geochemical constraints on ocean general circulation models. Final report, May 1, 1995--April 30, 1997

    SciTech Connect

    Broecker, W.S.

    1998-05-17

    A better understanding of the manner in which the ocean operates is essential to the preparation for the consequences of the generation of CO{sub 2} by fossil fuel burning. Examples are as follows: (1) the ocean will ultimately take up a major fraction of the CO{sub 2} produced, but this uptake is retarded by the slow mixing rates, in order to predict the uptake, researchers must develop and validate general circulation models for the ocean; (2) during glacial time large global climate changes occurred. The changes were abrupt happening in a few decades. The trigger for these changes appears to have been reorganizations of the large-scale thermohaline circulation of the ocean. Models suggest that if the CO{sub 2} content of the atmosphere rises to more than 700 ppm, then a possibility exists that another such reorganization might occur. Hence, researchers must learn more about the factors influencing deep-water formation both in the northern Atlantic and in the Souther Ocean. The thrust of this research was to develop constraints based on the distributions of chemicals and tracers in the sea. The accomplishments are outlined in this report.

  3. Climatic Signal and Climatic Noise in Lorenz's Low Order Model of the Atmospheric Circulation

    NASA Astrophysics Data System (ADS)

    Freire, J.; Dacamara, C.; Corte-Real, J.; Gallas, J. A. C.

    2003-04-01

    The climate state may be defined by a set of statistics computed over a very large number of replicas of the Atmosphere (ensemble), each replica evolving independently of each other, but all replicas subject to the same boundary conditions (external forcing). Such dynamic approach of the climate state is particulary adequate to define the concepts of climatic signal (linked to external forcing) and climatic noise (associated to distinct events of the same climatic state). Lorenz's low-order model of the general circulation is a useful tool to study the atmospheric signal and noise when the system is subject to prescribed forcing (e.g. seasonal forcing). This is due to the richness of the model as a dynamical system together with its low computacional cost that allows building ensembles with a large number of replicas. In our study we analyse the dynamical behavior of the atmospheric circulation based on a large set of numerical integrations (≈10000). The climate state is analysed and particular attention is devoted to the problem of separating the climatic signal from the climatic noise for different types of seasonal forcing.

  4. Simulating Titan's methane cycle with the TitanWRF General Circulation Model

    NASA Astrophysics Data System (ADS)

    Newman, Claire E.; Richardson, Mark I.; Lian, Yuan; Lee, Christopher

    2016-03-01

    Observations provide increasing evidence of a methane hydrological cycle on Titan. Earth-based and Cassini-based monitoring has produced data on the seasonal variation in cloud activity and location, with clouds being observed at increasingly low latitudes as Titan moved out of southern summer. Lakes are observed at high latitudes, with far larger lakes and greater areal coverage in the northern hemisphere, where some shorelines extend down as far as 50°N. Rainfall at some point in the past is suggested by the pattern of flow features on the surface at the Huygens landing site, while recent rainfall is suggested by surface change. As with the water cycle on Earth, the methane cycle on Titan is both impacted by tropospheric dynamics and likely able to impact this circulation via feedbacks. Here we use the 3D TitanWRF General Circulation Model (GCM) to simulate Titan's methane cycle. In this initial work we use a simple large-scale condensation scheme with latent heat feedbacks and a finite surface reservoir of methane, and focus on large-scale dynamical interactions between the atmospheric circulation and methane, and how these impact seasonal changes and the long term (steady state) behavior of the methane cycle. We note five major conclusions: (1) Condensation and precipitation in the model is sporadic in nature, with interannual variability in its timing and location, but tends to occur in association with both (a) frequent strong polar upwelling during spring and summer in each hemisphere, and (b) the Inter-Tropical Convergence Zone (ITCZ), a region of increased convergence and upwelling due to the seasonally shifting Hadley cells. (2) An active tropospheric methane cycle affects the stratospheric circulation, slightly weakening the stratospheric superrotation produced. (3) Latent heating feedback strongly influences surface and near-surface temperatures, narrowing the latitudinal range of the ITCZ, and changing the distribution - and generally weakening the

  5. Venus atmosphere simulated by a high-resolution general circulation model

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko

    2016-07-01

    An atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) have been developed (e.g., Sugimoto et al., 2014a) and a very high-resolution simulation is performed. The highest resolution of the model is T319L120; 960 times 480 horizontal grids (grid intervals are about 40 km) with 120 vertical layers (layer intervals are about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal and semi-diurnal components. The infrared radiative process is simplified by adopting Newtonian cooling approximation. The temperature is relaxed to a prescribed horizontally uniform temperature distribution, in which a layer with almost neutral static stability observed in the Venus atmosphere presents. A fast zonal wind in a solid-body rotation is given as the initial state. Starting from this idealized superrotation, the model atmosphere reaches a quasi-equilibrium state within 1 Earth year and this state is stably maintained for more than 10 Earth years. The zonal-mean zonal flow with weak midlatitude jets has almost constant velocity of 120 m/s in latitudes between 45°S and 45°N at the cloud top levels, which agrees very well with observations. In the cloud layer, baroclinic waves develop continuously at midlatitudes and generate Rossby-type waves at the cloud top (Sugimoto et al., 2014b). At the polar region, warm polar vortex zonally surrounded by a cold latitude band (cold collar) is well reproduced (Ando et al., 2016). As for horizontal kinetic energy spectra, divergent component is broadly (k>10) larger than rotational component compared with that on Earth (Kashimura et al., in preparation). Finally, recent results for thermal tides and small-scale waves will be shown in the presentation. Sugimoto, N. et al. (2014a), Baroclinic modes in the Venus atmosphere simulated by GCM, Journal of Geophysical Research: Planets, Vol. 119, p1950-1968. Sugimoto, N. et al. (2014b), Waves in a Venus general

  6. Overly persistent circulation in climate models contributes to overestimated frequency and duration of heat waves and cold spells

    NASA Astrophysics Data System (ADS)

    Plavcová, Eva; Kyselý, Jan

    2016-05-01

    The study examines links of summer heat waves and winter cold spells in Central Europe to atmospheric circulation and specifically its persistence in an ensemble of regional climate models (RCMs). We analyse 13 RCMs driven by the ERA-40 reanalysis and compare them against observations over reference period 1971-2000. Using objective classification of circulation types and an efficiency coefficient with a block resampling test, we identify circulation types significantly conducive to heat waves and cold spells. We show that the RCMs have a stronger tendency to group together days with very high or low temperature and tend to simulate too many heat waves and cold spells, especially those lasting 5 days and more. Circulation types conducive to heat waves in summer are characterized by anticyclonic, southerly and easterly flow, with increasing importance of warm advection during heat waves. Winter cold spells are typically associated with easterly and anticyclonic flow, and the onset of cold spells tends to be linked to northerly and cyclonic flow with cold advection. The RCMs are generally able to reproduce the links between circulation and heat waves or cold spells, including the radiation-to-advection effect for heat waves and the opposite advection-to-radiation effect for cold spells. They capture relatively well also changes of mean temperature anomalies during sequences of given circulation types, namely the tendency towards temperature increase (decrease) during those types conducive to heat waves (cold spells). Since mean lengths of all circulation supertypes are overestimated in the RCMs, we conclude that the overly persistent circulation in climate models contributes to the overestimated frequency of long heat waves and cold spells. As these biases are rather general among the examined RCMs and similar drawbacks are likely to be manifested in climate model simulations for the twenty-first century, the results also suggest that climate change scenarios for

  7. A System of Conservative Regridding for Ice-Atmosphere Coupling in a General Circulation Model (GCM)

    NASA Technical Reports Server (NTRS)

    Fischer, R.; Nowicki, S.; Kelley, M.; Schmidt, G. A.

    2014-01-01

    The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere-ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

  8. Complex mean circulation over the inner shelf south of Martha's Vineyard revealed by observations and a high-resolution model

    USGS Publications Warehouse

    Ganju, Neil K.; Lentz, Steven J.; Kirincich, Anthony R.; Farrar, J. Thomas

    2011-01-01

    Inner-shelf circulation is governed by the interaction between tides, baroclinic forcing, winds, waves, and frictional losses; the mean circulation ultimately governs exchange between the coast and ocean. In some cases, oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow. Recent observational and modeling efforts in an overlapping domain centered on the Martha's Vineyard Coastal Observatory (MVCO) provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf. ADCP and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross-shore directions. Nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter-clockwise gyre near the MVCO. The loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients (Δh/h), which is important for representing nonlinear interactions between currents and bathymetry. The modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances, suggesting that observed inner-shelf momentum balances may be confounded. Given the available observational and modeling data, this work defines the spatially variable mean circulation and its formation mechanism—tidal rectification—and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast. The results of this study have implications for future observational and modeling studies near the MVCO and other inner-shelf locations with alongshore bathymetric variability.

  9. Advanced Modeling, Simulation and Analysis (AMSA) Capability Roadmap Progress Review

    NASA Technical Reports Server (NTRS)

    Antonsson, Erik; Gombosi, Tamas

    2005-01-01

    Contents include the following: NASA capability roadmap activity. Advanced modeling, simulation, and analysis overview. Scientific modeling and simulation. Operations modeling. Multi-special sensing (UV-gamma). System integration. M and S Environments and Infrastructure.

  10. Prospective assessment of the prognostic value of circulating tumor cells and their clusters in patients with advanced-stage breast cancer.

    PubMed

    Mu, Zhaomei; Wang, Chun; Ye, Zhong; Austin, Laura; Civan, Jesse; Hyslop, Terry; Palazzo, Juan P; Jaslow, Rebecca; Li, Bingshan; Myers, Ronald E; Jiang, Juntao; Xing, Jinliang; Yang, Hushan; Cristofanilli, Massimo

    2015-12-01

    The enumeration of circulating tumor cells (CTCs) provides important prognostic values in patients with metastatic breast cancer. Recent studies indicate that individual CTCs form clusters and these CTC-clusters play an important role in tumor metastasis. We aimed to assess whether quantification of CTC-clusters provides additional prognostic value over quantification of individual CTCs alone. In 115 prospectively enrolled advanced-stage (III and IV) breast cancer patients, CTCs and CTC-clusters were counted in 7.5 ml whole blood using the CellSearch system at baseline before first-line therapy. The individual and joint effects of CTC and CTC cluster counts on patients' progression-free survival (PFS) were analyzed using Cox proportional hazards modeling. Of the 115 patients, 36 (31.3 %) had elevated baseline CTCs (≥5 CTCs/7.5 ml) and 20 (17.4 %) had CTC-clusters (≥2 CTCs/7.5 ml). Patients with elevated CTCs and CTC-clusters both had worse PFS with a hazard ratio (HR) of 2.76 [95 % confidence interval (CI) 1.57-4.86, P log-rank = 0.0005] and 2.83 (1.48-5.39, P log-rank = 0.001), respectively. In joint analysis, compared with patients with <5 CTCs and without CTC-clusters, patients with elevated CTCs but without clusters, and patients with elevated CTCs and with clusters, had an increasing trend of progression risk, with an HR of 2.21 (1.02-4.78) and 3.32 (1.68-6.55), respectively (P log-rank = 0.0006, P trend = 0.0002). The additional prognostic value of CTC-clusters appeared to be more pronounced in patients with inflammatory breast cancer (IBC), the most aggressive form of breast cancer with the poorest survival. Baseline counts of both individual CTCs and CTC-clusters were associated with PFS in advanced-stage breast cancer patients. CTC-clusters might provide additional prognostic value compared with CTC enumeration alone, in patients with elevated CTCs.

  11. Advances in Modelling of Valley Glaciers

    NASA Astrophysics Data System (ADS)

    Adhikari, Surendra

    For glaciological conditions typical of valley glaciers, the central idea of this research lies in understanding the effects of high-order mechanics and parameterizing these for simpler dynamical and statistical methods in glaciology. As an effective tool for this, I formulate a new brand of dynamical models that describes distinct physical processes of deformational flow. Through numerical simulations of idealized glacier domains, I calculate empirical correction factors to capture the effects of longitudinal stress gradients and lateral drag for simplified dynamical models in the plane-strain regime. To get some insights into real glacier dynamics, I simulate Haig Glacier in the Canadian Rocky Mountains. As geometric effects overshadow dynamical effects in glacier retreat scenarios, it appears that high-order physics are not very important for Haig Glacier, particularly for evaluating its fate. Indeed, high-order and reduced models all predict that Haig Glacier ceases to exist by about AD2080 under ongoing climate warming. This finding regarding the minimal role of high-order physics may not be broadly valid, as it is not true in advance scenarios at Haig Glacier and it may not be representative of other glaciological settings. Through a 'bulk' parameterization of high-order physics, geometric and climatic settings, sliding conditions, and transient effects, I also provide new insights into the volume-area relation, a widely used statistical method for estimating glacier volume. I find a steady-state power-law exponent of 1:46, which declines systematically to 1:38 after 100 years of sustained retreat, in good accord with the observations. I recommend more accurate scaling relations through characterization of individual glacier morphology and degree of climatic disequilibrium. This motivates a revision of global glacier volume estimates, of some urgency in sea level rise assessments.

  12. A three-dimensional coupled ice-ocean model of coastal circulation

    NASA Astrophysics Data System (ADS)

    Ikeda, Motoyoshi

    1988-09-01

    A coupled ice-ocean model is employed to examine roles of ocean circulation on sea ice formation and distribution along the east coasts of North America and Greenland. The model has a flat bottom and a rectangular domain with a coastal boundary to the west, an artificial solid boundary to the north, and open eastern and southern boundaries. The model is driven by idealized alongshore wind stress and atmospheric cooling; the wind stress decays northward and southward with a maximum amplitude at the middle. The open water heat flux is locally specified with both seaward and southward decay, and the heat flux through ice is taken to be inversely proportional to the ice thickness. Ice internal stresses are simplified under the assumption that the major strain is cross-shore shear deformation. The ocean model has three levels: the surface mixed layer and two levels in the lower ocean. Linear momentum equations are used, and a geostrophic cross-shore momentum balance is assumed. Vertical viscosity is represented only by the surface and bottom Ekman flow. Equations for temperature and salinity retain advection and diffusion terms in both vertical and horizontal directions. The model reveals the following important roles of the ocean: northerly wind induces shoreward Ekman flow and southward barotropic flow, which develops only to the southern (downstream in the sense of long coastal-trapped wave propagation) side of wind forcing region and merges westward owing to the β-effect. Coastal downwelling produces additional baroclinic alongshore flow, intensifying (weakening) the southward flow in the upper (lower) ocean. Cyclonic circulation is generated by differences in Ekman flow between the ice-covered onshore area and open-water offshore area. Ice, which occupies the coastal area, is narrowed dynamically by the shoreward Ekman flow and thermodynamically by the warm offshore water in the Ekman flow. Ice is also advected southward by the alongshore current, associated with

  13. Exploring Secondary Students' Epistemological Features Depending on the Evaluation Levels of the Group Model on Blood Circulation

    ERIC Educational Resources Information Center

    Lee, Shinyoung; Kim, Heui-Baik

    2014-01-01

    The purpose of this study is to identify the epistemological features and model qualities depending on model evaluation levels and to explore the reasoning process behind high-level evaluation through small group interaction about blood circulation. Nine groups of three to four students in the eighth grade participated in the modeling practice.…

  14. First results of a general circulation model applied to the SST-NOx problem. [ozone decomposition

    NASA Technical Reports Server (NTRS)

    Cunnold, D. M.; Alyea, F. N.; Phillips, N. A.; Prinn, R. G.

    1974-01-01

    Results of model runs, one using two-dimensional distribution of NO2 in the unperturbed stratosphere and another including an additional localized source of NO2 to approximate the effect of SSTs, are reported. The general circulation model and chemical reactions are described, and corrections in the previous latitudinal and seasonal gradients of total columnar ozone and the diffusion coefficient in the neighborhood of the tropopause are noted. Excellent agreement with previous observations was obtained. Global distributions of ozone and NO2 are described and represented in graphs. Results indicate ozone reduction of approximately 16% in the Northern Hemisphere and approximately 8% in the Southern Hemisphere, with the mid-latitude source of NO2 apparently having a blocking effect on the horizontal transport of ozone, resulting in larger reductions of ozone at high latitudes than at low ones.

  15. Assimilating NOAA SST data into BSH operational circulation model for North and Baltic Seas

    NASA Astrophysics Data System (ADS)

    Losa, Svetlana; Schroeter, Jens; Nerger, Lars; Janjic, Tijana; Danilov, Sergey; Janssen, Frank

    A data assimilation (DA) system is developed for BSH operational circulation model in order to improve forecast of current velocities, sea surface height, temperature and salinity in the North and Baltic Seas. Assimilated data are NOAA sea surface temperature (SST) data for the following period: 01.10.07 -30.09.08. All data assimilation experiments are based on im-plementation of one of the so-called statistical DA methods -Singular Evolutive Interpolated Kalman (SEIK) filter, -with different ways of prescribing assumed model and data errors statis-tics. Results of the experiments will be shown and compared against each other. Hydrographic data from MARNET stations and sea level at series of tide gauges are used as independent information to validate the data assimilation system. Keywords: Operational Oceanography and forecasting

  16. Effects of Southern Hemisphere Wind Changes on the Meridional Overturning Circulation in Ocean Models.

    PubMed

    Gent, Peter R

    2016-01-01

    Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow meridional overturning circulation (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability.

  17. Dust Emissions, Transport, and Deposition Simulated with the NASA Finite-Volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Colarco, Peter; daSilva, Arlindo; Ginoux, Paul; Chin, Mian; Lin, S.-J.

    2003-01-01

    Mineral dust aerosols have radiative impacts on Earth's atmosphere, have been implicated in local and regional air quality issues, and have been identified as vectors for transporting disease pathogens and bringing mineral nutrients to terrestrial and oceanic ecosystems. We present for the first time dust simulations using online transport and meteorological analysis in the NASA Finite-Volume General Circulation Model (FVGCM). Our dust formulation follows the formulation in the offline Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport Model (GOCART) using a topographical source for dust emissions. We compare results of the FVGCM simulations with GOCART, as well as with in situ and remotely sensed observations. Additionally, we estimate budgets of dust emission and transport into various regions.

  18. Characteristics modeling for supercritical circulating fluidized bed boiler working in oxy-combustion technology

    NASA Astrophysics Data System (ADS)

    Balicki, Adrian; Bartela, Łukasz

    2014-06-01

    Among the technologies which allow to reduce greenhouse gas emission, mainly carbon dioxide, special attention deserves the idea of `zeroemission' technology based on boilers working in oxy-combustion technology. In the paper the results of analyses of the influence of changing two quantities, namely oxygen share in oxidant produced in the air separation unit, and oxygen share in oxidant supplied to the furnace chamber on the selected characteristics of a steam boiler including the degree of exhaust gas recirculation, boiler efficiency and adiabatic flame temperature, was examined. Due to the possibility of the integration of boiler model with carbon dioxide capture, separation and storage installation, the subject of the analysis was also to determine composition of the flue gas at the outlet of a moisture condensation installation. Required calculations were made using a model of a supercritical circulating fluidized bed boiler working in oxy-combustion technology, which was built in a commercial software and in-house codes.

  19. Intercomparison and interpretation of surface energy fluxes in atmospheric general circulation models

    NASA Technical Reports Server (NTRS)

    Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Boer, G. J.; Dazlich, D. A.; Del Genio, A. D.; Deque, M.; Dymnikov, V.; Galin, V.; Ghan, S. J.

    1992-01-01

    Responses of the surface energy budgets and hydrologic cycles of 19 atmospheric general circulation models to an imposed, globally uniform sea surface temperature perturbation of 4 K were analyzed. The responses of the simulated surface energy budgets are extremely diverse and are closely linked to the responses of the simulated hydrologic cycles. The response of the net surface energy flux is not controlled by cloud effects; instead, it is determined primarily by the response of the latent heat flux. The prescribed warming of the oceans leads to major increases in the atmospheric water vapor content and the rates of evaporation and precipitation. The increased water vapor amount drastically increases the downwelling IR radiation at the earth's surface, but the amount of the change varies dramatically from one model to another.

  20. Simulation of the great plains low-level jet and associated clouds by general circulation models

    SciTech Connect

    Ghan, S.J.; Bian, X.; Corsetti, L.

    1996-07-01

    The low-level jet frequently observed in the Great Plains of the United States forms preferentially at night and apparently influences the timing of the thunderstorms in the region. The authors have found that both the European Centre for Medium-Range Weather Forecasts general circulation model and the National Center for Atmospheric Research Community Climate Model simulate the low-level jet rather well, although the spatial distribution of the jet frequency simulated by the two GCM`s differ considerably. Sensitivity experiments have demonstrated that the simulated low-level jet is surprisingly robust, with similar simulations at much coarser horizontal and vertical resolutions. However, both GCM`s fail to simulate the observed relationship between clouds and the low-level jet. The pronounced nocturnal maximum in thunderstorm frequency associated with the low-level jet is not simulated well by either GCM, with only weak evidence of a nocturnal maximum in the Great Plains. 36 refs., 20 figs.

  1. The water cycle in the general circulation model of the martian atmosphere

    NASA Astrophysics Data System (ADS)

    Shaposhnikov, D. S.; Rodin, A. V.; Medvedev, A. S.

    2016-03-01

    Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature regime on Mars through the use of physical parameterizations typical of both terrestrial and Martian models. We have achieved stable computation for three Martian years, while maintaining a conservative advection scheme taking into account the water-ice phase transitions, water exchange between the atmosphere and surface, and corrections for the vertical velocities of ice particles due to sedimentation. The studies show a strong dependence of the amount of water that is actively involved in the water cycle on the initial data, model temperatures, and the mechanism of water exchange between the atmosphere and the surface. The general pattern and seasonal asymmetry of the water cycle depends on the size of ice particles, the albedo, and the thermal inertia of the planet's surface. One of the modeling tasks, which results from a comparison of the model data with those of the TES experiment on board Mars Global Surveyor, is the increase in the total mass of water vapor in the model in the aphelion season and decrease in the mass of water ice clouds at the poles. The surface evaporation scheme, which takes into account the turbulent rise of water vapor, on the one hand, leads to the most complete evaporation of ice from the surface in the summer season in the northern hemisphere and, on the other hand, supersaturates the atmosphere with ice due to the vigorous evaporation, which leads to worse consistency between the amount of the precipitated atmospheric ice and the experimental data. The full evaporation of ice from the surface increases the model sensitivity to the size of the polar cap; therefore, the increase in the

  2. 3D Simulations of the Early Mars Climate with a General Circulation Model

    NASA Technical Reports Server (NTRS)

    Forget, F.; Haberle, R. M.; Montmessin, F.; Cha, S.; Marcq, E.; Schaeffer, J.; Wanherdrick, Y.

    2003-01-01

    The environmental conditions that existed on Mars during the Noachian period are subject to debate in the community. In any case, there are compelling evidence that these conditions were different than what they became later in the amazonian and possibly the Hesperian periods. Indeed, most of the old cratered terrains are disected by valley networks (thought to have been carved by flowing liquid water), whereas younger surface are almost devoid of such valleys. In addition, there are evidence that the erosion rate was much higher during the early noachian than later. Flowing water is surprising on early Mars because the solar luminosity was significantly lower than today. Even with the thick atmosphere (up to several bars).To improve our understanding of the early Mars Climate, we have developed a 3D general circulation model similar to the one used on current Earth or Mars to study the details of the climate today. Our first objective is to answer the following questions : how is the Martian climate modified if 1) the surface pressure is increased up to several bars (our baseline: 2 bars) and 2) if the sun luminosity is decreased by 25 account the heat possibly released by impacts during short periods, although it may have played a role .For this purpose, we have coupled the Martian General Circulation model developed at LMD with a sophisticated correlated k distribution model developped at NASA Ames Research Center. It is a narrow band model which computes the radiative transfer at both solar and thermal wavelengths (from 0.3 to 250 microns).

  3. Local and Global Views of Systematic Errors of Atmosphere-Ocean General Circulation Models

    NASA Astrophysics Data System (ADS)

    Mechoso, C. Roberto; Wang, Chunzai; Lee, Sang-Ki; Zhang, Liping; Wu, Lixin

    2014-05-01

    Coupled Atmosphere-Ocean General Circulation Models (CGCMs) have serious systematic errors that challenge the reliability of climate predictions. One major reason for such biases is the misrepresentations of physical processes, which can be amplified by feedbacks among climate components especially in the tropics. Much effort, therefore, is dedicated to the better representation of physical processes in coordination with intense process studies. The present paper starts with a presentation of these systematic CGCM errors with an emphasis on the sea surface temperature (SST) in simulations by 22 participants in the Coupled Model Intercomparison Project phase 5 (CMIP5). Different regions are considered for discussion of model errors, including the one around the equator, the one covered by the stratocumulus decks off Peru and Namibia, and the confluence between the Angola and Benguela currents. Hypotheses on the reasons for the errors are reviewed, with particular attention on the parameterization of low-level marine clouds, model difficulties in the simulation of the ocean heat budget under the stratocumulus decks, and location of strong SST gradients. Next the presentation turns to a global perspective of the errors and their causes. It is shown that a simulated weak Atlantic Meridional Overturning Circulation (AMOC) tends to be associated with cold biases in the entire Northern Hemisphere with an atmospheric pattern that resembles the Northern Hemisphere annular mode. The AMOC weakening is also associated with a strengthening of Antarctic bottom water formation and warm SST biases in the Southern Ocean. It is also shown that cold biases in the tropical North Atlantic and West African/Indian monsoon regions during the warm season in the Northern Hemisphere have interhemispheric links with warm SST biases in the tropical southeastern Pacific and Atlantic, respectively. The results suggest that improving the simulation of regional processes may not suffice for a more

  4. A fracture-loop thermal balance model of black smoker circulation

    NASA Astrophysics Data System (ADS)

    Strens, M. R.; Cann, J. R.

    1986-02-01

    This time-dependent model examines the thermal balance between hot rocks and hydrothermal circulation during the formation of volcanogenic ore deposits, in order to establish whether the major heat supply to black smoker systems comes from the rock or from an underlying magma chamber. Flow is modelled as an open thermosyphon in a single fault, which is parallel and very close to the mid-ocean ridge axis. This configuration is based on seafloor and ophiolite evidence of black smoker systems and their structural location. The fault is represented in the model by a series of pipes carrying turbulent flow, which is driven by the buoyancy difference between upflow and downflow. Hydraulic resistance to flow is predominantly in the discharge zone. The fault is allowed to propagate downwards. The horizontal conductive heat flux from the rock is computed analytically, with the water flow treated digitally, so that the heat exchange at the rock-water interface at every position in the loop can be calculated for each time step. The model thus provides the exit water temperature and mass flow rate throughout the lifespan of a hot spring, enabling the resulting ore mass to be estimated. Results show that this system cannot obtain sufficient heat from a thin layer of rock (such as the 1-2 km thick layer of lavas and dykes overlying an axial magma chamber) to sustain long-lived, ore-forming black smokers. If the circulation penetrates through a greater volume of hot rock to the base of a recently-solidified magma chamber, ore masses of a few million tonnes can be formed if conditions are particularly favourable. We conclude that systems producing larger ore masses must tap a magmatic heat supply.

  5. Putative circulating markers of the early and advanced stages of breast cancer identified by high-resolution label-free proteomics.

    PubMed

    Panis, Carolina; Pizzatti, Luciana; Herrera, Ana Cristina; Cecchini, Rubens; Abdelhay, Eliana

    2013-03-01

    This study evaluated the plasmatic proteomic profile of breast cancer patients in the early (ED) and advanced (AD) stages, employing high-throughput proteomics. We identified 92 differentially expressed proteins in ED and 73 proteins in AD patients. Gelsolin, lumican, clusterin, SALL4 and PMS2, as well hTERT, TNF-α and GRHL3 were chosen for further investigation. ED presented augmented expression of GRHL3 and reduced circulating TNF-α with high expression of GRHL3 in tumors. AD displayed high TNF-α and a significant expression of PMS2 in tumors. These findings suggest processes enrolling stem cell division in ED, with TNF-α signaling and DNA mismatch repair in the advanced stage.

  6. Effective use of general circulation model outputs for forecasting monthly rainfalls to long lead times

    NASA Astrophysics Data System (ADS)

    Hawthorne, Sandra; Wang, Q. J.; Schepen, Andrew; Robertson, David

    2013-09-01

    Long lead rainfall forecasts are highly valuable for planning and management of water resources and agriculture. In this study, we establish multiple statistical calibration and bridging models that use general circulation model (GCM) outputs as predictors to produce monthly rainfall forecasts for Australia with lead times up to 8 months. The statistical calibration models make use of raw forecasts of rainfall from a coupled GCM, and the statistical bridging models make use of sea surface temperature (SST) forecasts of the GCM. The forecasts from the multiple models are merged through Bayesian model averaging to take advantage of the strengths of individual models. The skill of monthly rainfall forecasts is generally low. Compared to forecasting seasonal rainfall totals, it is more challenging to forecast monthly rainfall. However, there are regions and months for which forecasts are skillful. In particular, there are months of the year for which forecasts can be skillfully made at long lead times. This is most evident for the period of November and December. Using GCM forecasts of SST through bridging clearly improves monthly rainfall forecasts. For lead time 0, the improvement is particularly evident for February to March, July and October to December. For longer lead times, the benefit of bridging is more apparent. As lead time increases, bridging is able to maintain forecast skill much better than when only calibration is applied.

  7. Generation of Prostate Cancer Patient Derived Xenograft Models from Circulating Tumor Cells.

    PubMed

    Williams, Estrelania S; Rodriguez-Bravo, Veronica; Rodriquez-Bravo, Veronica; Chippada-Venkata, Uma; De Ia Iglesia-Vicente, Janis; Gong, Yixuan; Galsky, Matthew; Oh, William; Cordon-Cardo, Carlos; Domingo-Domenech, Josep

    2015-10-20

    Patient derived xenograft (PDX) models are gaining popularity in cancer research and are used for preclinical drug evaluation, biomarker identification, biologic studies, and personalized medicine strategies. Circulating tumor cells (CTC) play a critical role in tumor metastasis and have been isolated from patients with several tumor types. Recently, CTCs have been used to generate PDX experimental models of breast and prostate cancer. This manuscript details the method for the generation of prostate cancer PDX models from CTCs developed by our group. Advantages of this method over conventional PDX models include independence from surgical sample collection and generating experimental models at various disease stages. Density gradient centrifugation followed by red blood cell lysis and flow cytometry depletion of CD45 positive mononuclear cells is used to enrich CTCs from peripheral blood samples collected from patients with metastatic disease. The CTCs are then injected into immunocompromised mice; subsequently generated xenografts can be used for functional studies or harvested for molecular characterization. The primary limitation of this method is the negative selection method used for CTC enrichment. Despite this limitation, the generation of PDX models from CTCs provides a novel experimental model to be applied to prostate cancer research.

  8. Extending the NASA Ames Mars General Circulation Model to Explore Mars’ Middle Atmosphere

    NASA Astrophysics Data System (ADS)

    Brecht, Amanda; Hollingsworth, J.; Kahre, M.; Schaeffer, J.

    2013-10-01

    The NASA Ames Mars General Circulation Model (MGCM) upper boundary has been extended to ~120 km altitude (p ~10-5 mbar). The extension of the MGCM upper boundary initiates the ability to understand the connection between the lower and upper atmosphere of Mars through the middle atmosphere 70 - 120 km). Moreover, it provides the opportunity to support future missions (i.e. the 2013 MAVEN mission). A major factor in this extension is the incorporation of the Non-Local Thermodynamic Equilibrium (NLTE) heating (visible) and cooling (infrared). This modification to the radiative transfer forcing (i.e., RT code) has been significantly tested in a 1D vertical column and now has been ported to the full 3D Mars GCM. Initial results clearly show the effects of NLTE in the upper middle atmosphere. Diagnostic of seasonal mean fields and large-scale wave activity will be shown with insight into circulation patterns in the middle atmosphere. Furthermore, sensitivity tests with the resolution of the pressure and temperature grids, in which the k-coefficients are calculated upon, have been performed in the 1D RT code. Our progress on this research will be presented. Brecht is supported by NASA’s Postdoctoral Program at the Ames Research Center, administered by Oak Ridge Associated Universities through a contract with NASA.

  9. Climate Dynamics and Global Change: Temperature, Precipitation, and Circulation in GFDL Aqua-Planet Model

    NASA Astrophysics Data System (ADS)

    Dinh, T.; Fueglistaler, S.

    2015-12-01

    Numerical experiments are carried out using the GFDL General Circulation Model to assess climate sensitivity associated with CO2 increase and surface warming. This work is motivated by the calculation by Cess and Potter (1988, JGR), who proposed that surface temperature perturbations may be used as a surrogate for climate change induced by CO2 increase.We compare climatic changes due to CO2 increase in slab-ocean simulations with changes forced by surface warming in prescribed-surface-temperature simulations with fixed CO2 (Cess-type experiments). We found that slab-ocean and Cess-type experiments give the same rates of change per degree surface warming for the global atmosphere temperature and circulation strength. However, the global precipitation increases almost twice as slowly in slab-ocean runs (1.5%/K) when compared to Cess-type runs (2.8%/K). Therefore, we caution that Cess-type experiments may not be suitable for studying global precipitation change under climate change.

  10. The Influence of Locally Increased Gravity Wave Drag on the Middle Atmosphere Circulation - A Model Study

    NASA Astrophysics Data System (ADS)

    Lilienthal, Friederike; Sacha, Petr; Jacobi, Christoph; Pisoft, Petr

    2016-04-01

    Internal gravity waves (GW) are one of the most dominant features in the middle atmosphere. They are a main contributor for energy and angular momentum transport and thus play an important role for atmospheric dynamics such as the Quasi Biennial Oscillation or the Brewer-Dobson circulation (BDC). GPS radio occultation measurements (e.g. Sacha et al., 2015) have shown that GW can appear in local hotspots, e.g. in the lower stratosphere of the Eastern Asia/North-western Pacific (EA/NP) region. Using these data as an input for the GW parameterization of a 3D primitive equation model for the middle and upper atmosphere (MUAM) we study the dynamical effects of such a localized breaking region. We further introduce an additional artificial GW drag in the lower stratosphere EA/NP region and show that a localized GW forcing is more efficient in creating planetary waves (PWs) than zonally uniform GW forcing. We observe PWs propagating both equatorward and poleward and upward along the edge of the polar vortex. Possible consequences for the polar vortex stability and stratosphere-troposphere exchange in the tropical region are discussed. Finally, applying 3D wave activity flux and 3D residual circulation diagnostics, we investigated the possible role of this area in the longitudinal variability of the BDC with a hypothesis of its enhanced downwelling branch in this region.

  11. Numerical Models of Human Circulatory System under Altered Gravity: Brain Circulation

    NASA Technical Reports Server (NTRS)

    Kim, Chang Sung; Kiris, Cetin; Kwak, Dochan; David, Tim

    2003-01-01

    A computational fluid dynamics (CFD) approach is presented to model the blood flow through the human circulatory system under altered gravity conditions. Models required for CFD simulation relevant to major hemodynamic issues are introduced such as non-Newtonian flow models governed by red blood cells, a model for arterial wall motion due to fluid-wall interactions, a vascular bed model for outflow boundary conditions, and a model for auto-regulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models are solved iteratively using the pseudocompressibility method and dual time stepping. Moving wall boundary conditions from the first-order fluid-wall interaction model are used to study the influence of arterial wall distensibility on flow patterns and wall shear stresses during the heart pulse. A vascular bed modeling utilizing the analogy with electric circuits is coupled with an auto-regulation algorithm for multiple outflow boundaries. For the treatment of complex geometry, a chimera overset grid technique is adopted to obtain connectivity between arterial branches. For code validation, computed results are compared with experimental data for steady and unsteady non-Newtonian flows. Good agreement is obtained for both cases. In sin-type Gravity Benchmark Problems, gravity source terms are added to the Navier-Stokes equations to study the effect of gravitational variation on the human circulatory system. This computational approach is then applied to localized blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other model using an anatomical data set. A three- dimensional anatomical Circle of Willis configuration is reconstructed from human-specific magnetic resonance images using an image segmentation method. The blood flow through these Circle of Willis models is simulated to provide means for studying gravitational effects on the brain

  12. Circulating tumor cells exhibit stem cell characteristics in an orthotopic mouse model of colorectal cancer

    PubMed Central

    Niemietz, Thomas; Betzler, Alexander M.; Nanduri, Lahiri K.; Bork, Ulrich; Kahlert, Christoph; Thepkaysone, May-Linn; Swiersy, Anka; Büchler, Markus W.; Reissfelder, Christoph; Weitz, Jürgen; Rahbari, Nuh N.

    2016-01-01

    The prognosis of colorectal cancer (CRC) is closely linked to the occurrence of distant metastases, which putatively develop from circulating tumor cells (CTCs) shed into circulation by the tumor. As far more CTCs are shed than eventually metastases develop, only a small subfraction of CTCs harbor full tumorigenic potential. The aim of this study was to further characterize CRC-derived CTCs to eventually identify the clinically relevant subfraction of CTCs. We established an orthotopic mouse model of CRC which reliably develops metastases and CTCs. We were able to culture the resulting CTCs in vitro, and demonstrated their tumor-forming capacity when re-injected into mice. The CTCs were then subjected to qPCR expression profiling, revealing downregulation of epithelial and proliferation markers. Genes associated with cell-cell adhesion (claudin-7, CD166) were significantly downregulated, indicating a more metastatic phenotype of CTCs compared to bulk tumor cells derived from hepatic metastases. The stem cell markers DLG7 and BMI1 were significantly upregulated in CTC, indicating a stem cell-like phenotype and increased capacity of tumor formation and self-renewal. In concert with their in vitro and in vivo tumorigenicity, these findings indicate stem cell properties of mouse-derived CTCs. In conclusion, we developed an orthotopic mouse model of CRC recapitulating the process of CRC dissemination. CTCs derived from this model exhibit stem-cell like characteristics and are able to form colonies in vitro and tumors in vivo. Our results provide new insight into the biology of CRC-derived CTCs and may provide new therapeutic targets in the metastatic cascade of CRC. PMID:27029058

  13. The Tropical Subseasonal Variability Simulated in the NASA GISS General Circulation Model

    NASA Technical Reports Server (NTRS)

    Kim, Daehyun; Sobel, Adam H.; DelGenio, Anthony D.; Chen, Yonghua; Camargo, Suzana J.; Yao, Mao-Sung; Kelley, Maxwell; Nazarenko, Larissa

    2012-01-01

    The tropical subseasonal variability simulated by the Goddard Institute for Space Studies general circulation model, Model E2, is examined. Several versions of Model E2 were developed with changes to the convective parameterization in order to improve the simulation of the Madden-Julian oscillation (MJO). When the convective scheme is modified to have a greater fractional entrainment rate, Model E2 is able to simulate MJO-like disturbances with proper spatial and temporal scales. Increasing the rate of rain reevaporation has additional positive impacts on the simulated MJO. The improvement in MJO simulation comes at the cost of increased biases in the mean state, consistent in structure and amplitude with those found in other GCMs when tuned to have a stronger MJO. By reinitializing a relatively poor-MJO version with restart files from a relatively better-MJO version, a series of 30-day integrations is constructed to examine the impacts of the parameterization changes on the organization of tropical convection. The poor-MJO version with smaller entrainment rate has a tendency to allow convection to be activated over a broader area and to reduce the contrast between dry and wet regimes so that tropical convection becomes less organized. Besides the MJO, the number of tropical-cyclone-like vortices simulated by the model is also affected by changes in the convection scheme. The model simulates a smaller number of such storms globally with a larger entrainment rate, while the number increases significantly with a greater rain reevaporation rate.

  14. The annual pressure cycle on Mars: Results from the LMD Martian atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Hourdin, Frederic; Forget, Francois; Talagrand, O.

    1993-01-01

    We have been developing a General Circulation Model (GCM) of the martian atmosphere since 1989. The model has been described rather extensively elsewhere and only the main characteristics are given here. The dynamical part of the model, adapted from the LMD terrestrial climate model, is based on a finite-difference formulation of the classical 'primitive equations of meteorology.' The radiative transfer code includes absorption and emission by CO2 (carefully validated by comparison to line-by-line calculations) and dust in the thermal range and absorption and scattering by dust in the visible range. Other physical parameterizations are included: modeling of vertical turbulent mixing, dry convective adjustment (in order to prevent vertical unstable temperature profiles), and a multilayer model of the thermal conduction in the soil. Finally, the condensation-sublimation of CO2 is introduced through specification of a pressure-dependent condensation temperature. The atmospheric and surface temperatures are prevented from falling below this critical temperature by condensation and direct precipitation onto the surface of atmospheric CO2. The only prespecified spatial fields are the surface thermal inertia, albedo, and topography.

  15. Secular Trends and Climate Drift in Coupled Ocean-Atmosphere General Circulation Models

    SciTech Connect

    Covey, C C; Gleckler, P J; Phillips, T J; Bader, D C

    2004-11-23

    Coupled ocean-atmosphere general circulation models (coupled GCMs) with interactive sea ice are the primary tool for investigating possible future global warming and numerous other issues in climate science. A long-standing problem with such models is that when different components of the physical climate system are linked together, the simulated climate can drift away from observations unless constrained by ad hoc adjustments to interface fluxes. However, eleven modern coupled GCMs--including three that do not employ flux adjustments--behave much better in this respect than the older generation of models. Surface temperature trends in control run simulations (with external climate forcing such as solar brightness and atmospheric carbon dioxide held constant) are small compared with observed trends, which include 20th century climate change due to both anthropogenic and natural factors. Sea ice changes in the models are dominated by interannual variations. Deep ocean temperature and salinity trends are small enough for model control runs to extend over 1000 simulated years or more, but trends in some regions, most notably the Arctic, are inconsistent among the models and may be problematic.

  16. Bivariate spatial analysis of temperature and precipitation from general circulation models and observation proxies

    NASA Astrophysics Data System (ADS)

    Philbin, R.; Jun, M.

    2015-05-01

    This study validates the near-surface temperature and precipitation output from decadal runs of eight atmospheric ocean general circulation models (AOGCMs) against observational proxy data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis temperatures and Global Precipitation Climatology Project (GPCP) precipitation data. We model the joint distribution of these two fields with a parsimonious bivariate Matern spatial covariance model, accounting for the two fields' spatial cross-correlation as well as their own smoothnesses. We fit output from each AOGCM (30-year seasonal averages from 1981 to 2010) to a statistical model on each of 21 land regions. Both variance and smoothness values agree for both fields over all latitude bands except southern mid-latitudes. Our results imply that temperature fields have smaller smoothness coefficients than precipitation fields, while both have decreasing smoothness coefficients with increasing latitude. Models predict fields with smaller smoothness coefficients than observational proxy data for the tropics. The estimated spatial cross-correlations of these two fields, however, are quite different for most GCMs in mid-latitudes. Model correlation estimates agree well with those for observational proxy data for Australia, at high northern latitudes across North America, Europe and Asia, as well as across the Sahara, India, and Southeast Asia, but elsewhere, little consistent agreement exists.

  17. Simulations of the Amazon Basin circulation using the Pennsylvania State University/National Center for Atmospheric Research mesoscale model

    SciTech Connect

    Hahmann, A.N.

    1992-01-01

    A regional model has been used to investigate dynamical processes that control the circulation over the Amazon Basin. The application of a regional model to the Amazon Basin is unique and the method in which the model output is diagnosed is distinct. Two synoptic cases describe the ability of the regional model to simulate the circulation over the Amazon Basin. The first case, 15-17 April 1990, represents an example of the dominant circulation over the basin during the summer. The second case study occurs 27 February-1 March 1990. At the onset of this period, a vigorous trough is located in the subtropical westerlies of the Southern Hemisphere, which promotes advection of drier air by the low-level southerly flow into the southern part of the Basin. There is limited agreement between the observed circulation and the model simulations for the case studies. The model appears to simulate a number of dynamical processes known to take place. The timing of individual rain bands and their locations differ significantly from those observed. The sensitivity of the model simulation to the size of the grid spacing and the domain reveal that the regional circulation is most economically simulated with a nested domain and 60 km grid spacing. Larger grid spacings lead to excessive rainfall totals near the Andes Mountains and circulations that are unrealistic. Restricted domains (Amazon Basin only) produce excessive precipitation along the horizontal boundaries. Model simulations using several different combinations of convective and explicit precipitation parameterizations are performed. Experiments using the explicit moisture scheme without a cumulus parameterization scheme show the development of grid point instabilities. These instabilities result from interaction processes among latent heat release, large-scale moisture convergence, and surface pressure. When the Kuo-Anthes cumulus parameterization is included, grid point instabilities are substantially reduced.

  18. Thrust Removal Scheme for the FAST-MAC Circulation Control Model Tested in the National Transonic Facility

    NASA Technical Reports Server (NTRS)

    Chan, David T.; Milholen, William E., II; Jones, Gregory S.; Goodliff, Scott L.

    2014-01-01

    A second wind tunnel test of the FAST-MAC circulation control semi-span model was recently completed in the National Transonic Facility at the NASA Langley Research Center. The model allowed independent control of four circulation control plenums producing a high momentum jet from a blowing slot near the wing trailing edge that was directed over a 15% chord simple-hinged flap. The model was configured for transonic testing of the cruise configuration with 0deg flap deflection to determine the potential for drag reduction with the circulation control blowing. Encouraging results from analysis of wing surface pressures suggested that the circulation control blowing was effective in reducing the transonic drag on the configuration, however this could not be quantified until the thrust generated by the blowing slot was correctly removed from the force and moment balance data. This paper will present the thrust removal methodology used for the FAST-MAC circulation control model and describe the experimental measurements and techniques used to develop the methodology. A discussion on the impact to the force and moment data as a result of removing the thrust from the blowing slot will also be presented for the cruise configuration, where at some Mach and Reynolds number conditions, the thrust-removed corrected data showed that a drag reduction was realized as a consequence of the blowing.

  19. Detecting thermohaline circulation changes from ocean properties in a coupled model

    NASA Astrophysics Data System (ADS)

    Hu, Aixue; Meehl, Gerald A.; Han, Weiqing

    2004-07-01

    Significant changes of the thermohaline circulation (THC) are likely to cause abrupt climate change. Here we intend to find a simple measure to detect changes in THC through examining several factors proposed to control the THC variations using a coupled climate model. These factors are equatorial-South Atlantic upper ocean temperature, Southern Ocean freshening, inter-basin sea surface salinity contrast, and meridional steric height gradient. Three experiments are analyzed - a present-day control run, a freshwater hosing run and a 1% CO2 run. Results show that if freshwater flux is the primary cause, all examined factors can predict the THC changes. If both thermal and haline forcings are involved, only the Atlantic meridional steric height gradient gives a consistent measure of the THC variations. A new result presented here is that the inter-basin sea surface temperature contrast between North Atlantic and North Pacific is found to be an indicator of THC changes.

  20. Greenhouse gas-induced climate change simulated with the CCS second-generation general circulation model

    SciTech Connect

    Boer, G.J.; Mcfarlane, N.A.; Lazare, M. )

    1992-10-01

    The Canadian Climate Centre second-generation atmospheric general circulation model coupled to a mixed-layer ocean incorporating thermodynamic sea ice is used to simulate the equilibrium climate response to a doubling of CO[sub 2]. The results of the simulation indicate a global annual warming of 3.5 C with enhanced warming found over land and at higher latitudes. Precipitation and evaporation rates increase by about 4 percent, and cloud cover decreases by 2.2 percent. Soil moisture decreases over continental Northern Hemisphere land areas in summer. The frozen component of soil moisture decreases and the liquid component increases in association with the increase of temperature at higher latitudes. The simulated accumulation rate of permanent snow cover decreases markedly over Greenland and increases slightly over Antarctica. Seasonal snow and sea ice boundaries retreat, but local decreases in planetary albedo are counteracted by tropical increases, so there is little change in the global average. 39 refs.

  1. Oceanic circulation models help to predict global biogeography of pelagic yellow-bellied sea snake.

    PubMed

    Brischoux, François; Cotté, Cédric; Lillywhite, Harvey B; Bailleul, Frédéric; Lalire, Maxime; Gaspar, Philippe

    2016-08-01

    It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied sea snake (Hydrophis [Pelamis] platurus). State-of-the-art world ocean circulation models show how H. platurus, the only pelagic species of sea snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth's circumference. The very close association of these snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of sea snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large. PMID:27555651

  2. The sensitivity of latent heat flux to the air humidity approximations used in ocean circulation models

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Niiler, Pearn P.

    1990-01-01

    In deriving the surface latent heat flux with the bulk formula for the thermal forcing of some ocean circulation models, two approximations are commonly made to bypass the use of atmospheric humidity in the formula. The first assumes a constant relative humidity, and the second supposes that the sea-air humidity difference varies linearly with the saturation humidity at sea surface temperature. Using climatological fields derived from the Marine Deck and long time series from ocean weather stations, the errors introduced by these two assumptions are examined. It is shown that the errors reach above 100 W/sq m over western boundary currents and 50 W/sq m over the tropical ocean. The two approximations also introduce erroneous seasonal and spatial variabilities with magnitudes over 50 percent of the observed variabilities.

  3. Land-atmosphere CO2 exchange simulated by a land surface process model coupled to an atmospheric general circulation model

    NASA Astrophysics Data System (ADS)

    Bonan, Gordon B.

    1995-02-01

    CO2 uptake during plant photosynthesis and CO2 loss during plant and microbial respiration were added to a land surface process model to simulate the diurnal and annual cycles of biosphere-atmosphere CO2 exchange. The model was coupled to a modified version of the National Center for Atmospheric Research (NCAR) Community Climate Model version 2 (CCM2), and the coupled model was run for 5 years. The geographic patterns of annual net primary production are qualitatively similar to other models. When compared by vegetation type, annual production and annual microbial respiration are consistent with other models, except for needleleaf evergreen tree vegetation, where production is too high, and semidesert vegetation, where production and microbial respiration are too low. The seasonality of the net CO2 flux agrees with other models in the southern hemisphere and the tropics. The diurnal range is large for photosynthesis and lower for plant and microbial respiration, which agrees with qualitative expectations. The simulation of the central United States is poor due to temperature and precipitation biases in the coupled model. Despite these deficiencies the current approach is a promising means to include terrestrial CO2 fluxes in a climate system model that simulates atmospheric CO2 concentrations, because it alleviates important parameterization discrepancies between standard biogeochemical models and the land surface models typically used in general circulation models, and because the model resolves the diurnal range of CO2 exchange, which can be large (15 - 45 micromol CO2 sq m/s).

  4. Response of the Tropical Atmospheric Circulation to Glacial Boundary Conditions Simulated by an Ensemble of Coupled Climate Models

    NASA Astrophysics Data System (ADS)

    di Nezio, P. N.; Clement, A. C.; Vecchi, G. A.

    2009-12-01

    The response of the tropical atmospheric circulation to Last Glacial Maximum (LGM) boundary conditions is analyzed using an ensemble of coordinated climate model experiments performed for the Paleoclimate Modelling Intercomparison Project Phase II. The multi-model changes in the surface circulation of the Tropical Pacific are dominated by cross-equatorial winds flowing from the Northern hemisphere (NH) to the Southern hemisphere (SH) along with a strengthening of the easterlies over the equatorial Pacific. The anomalous cross-equatorial winds have been typically associated with an anomalous Hadley cell with the ascending branch in the SH and the descending branch in the NH compensating changes in atmospheric heat transport. However, in this ensemble of coupled General Circulation Models (GCMs) the changes in the tropical circulation result from different forcing in each hemisphere. In the NH hemisphere the changes are dominated by the topography of the ice sheets, while in the SH the changes result from cooling due to decreased CO2. The changes in circulation due to the topography of the icesheets are diagnosed using a steady s-coordinate primitive equation model linearized about a zonally symmetric basic state that solves for the eddy component of the circulation. The solutions from this model for each GCM indicate that differences in the simulation of the mean climate result in differences in the response to LGM topography. The multi-model atmospheric response in the NH is analogous to the expansion of the Aleutian low during boreal winter in the present climate, when the NH subtropical high is squeezed southeastward by an expanded Aleutian low. In the SH the models simulate an eastward expansion of the South Pacific Convergence Zone and contraction of the eastern Pacific dry zone consistent with reduced subsidence associated with a slowing down of the SH Hadley cell. This eastward shift in the mean climatology results in weakened trade winds. In addition to the

  5. AFES (Atmospheric general circulation model For the Earth Simulator) simulation for Venus

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko; Imamura, Takeshi; Takagi, Masahiro; Matsuda, Yoshihisa; Ando, Hiroki; Kashimura, Hiroki; Ohfuchi, Wataru; Enomoto, Takeshi; Takahashi, Yoshiyuki O.; Hayashi, Yoshi-Yuki

    We have developed an atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) and performed a very high-resolution simulation. The highest model resolution is T159L120; 0.75 degree times 0.75 degree latitude and longitude grids with 120 vertical layers (Δz is about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal change and Newtonian cooling that relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers. A fast zonal wind in a solid-body rotation is given as the initial state. In this paper, we will report several results newly obtained by this model. 1. Baroclinic instability appears in the cloud layer with small static stability and large vertical shear of the zonal flow. 2. Polar vortex is self-consistently generated by barotropic instability whose horizontal and vertical structure is consistent with the previous observations. 3. Kinetic energy spectra decreases by -5/3 power law in a range from wavenumber 4 to 45, whose range is different from that on Earth. Finally, we are now constructing the accurate radiation model of the Venus atmosphere.

  6. Application of Local Discretization Methods in the NASA Finite-Volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Yeh, Kao-San; Lin, Shian-Jiann; Rood, Richard B.

    2002-01-01

    We present the basic ideas of the dynamics system of the finite-volume General Circulation Model developed at NASA Goddard Space Flight Center for climate simulations and other applications in meteorology. The dynamics of this model is designed with emphases on conservative and monotonic transport, where the property of Lagrangian conservation is used to maintain the physical consistency of the computational fluid for long-term simulations. As the model benefits from the noise-free solutions of monotonic finite-volume transport schemes, the property of Lagrangian conservation also partly compensates the accuracy of transport for the diffusion effects due to the treatment of monotonicity. By faithfully maintaining the fundamental laws of physics during the computation, this model is able to achieve sufficient accuracy for the global consistency of climate processes. Because the computing algorithms are based on local memory, this model has the advantage of efficiency in parallel computation with distributed memory. Further research is yet desirable to reduce the diffusion effects of monotonic transport for better accuracy, and to mitigate the limitation due to fast-moving gravity waves for better efficiency.

  7. Global environmental effects of impact-generated aerosols: Results from a general circulation model, revision 1

    NASA Technical Reports Server (NTRS)

    Covey, Curt; Ghan, Steven J.; Walton, John J.; Weissman, Paul R.

    1989-01-01

    Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to our three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans substantially mitigates land surface cooling, an effect that one-dimensional models cannot quantify. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stage of cooling than in the one-dimensional model study. These two differences between three-dimensional and one-dimensional model simulations were noted previously in studies of nuclear winter; GCM-simulated climatic changes in the Alvarez-inspired scenario of asteroid/comet winter, however, are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though less severe, climatic changes, according to our GCM. Our conclusion is that it is difficult to imagine an asteroid or comet impact leading to anything approaching complete global freezing, but quite reasonable to assume that impacts at the Alvarez level, or even smaller, dramatically alter the climate in at least a patchy sense.

  8. 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.

  9. 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.

  10. Modeled alongshore circulation and morphologic evolution onshore of a large submarine canyon

    NASA Astrophysics Data System (ADS)

    Hansen, J. E.; Raubenheimer, B.; List, J. H.; Elgar, S.; Guza, R. T.; Lippmann, T. C.

    2012-12-01

    Alongshore circulation and morphologic evolution observed at an ocean beach during the Nearshore Canyon Experiment, onshore of a large submarine canyon in San Diego, CA (USA), are investigated using a two-dimensional depth-averaged numerical model (Delft3D). The model is forced with waves observed in ~500 m water depth and tidal constituents derived from satellite altimetry. Consistent with field observations, the model indicates that refraction of waves over the canyon results in wave focusing ~500 m upcoast of the canyon and shadowing onshore of the canyon. The spatial variability in the modeled wave field results in a corresponding non-uniform alongshore circulation field. In particular, when waves approach from the northwest the alongshore flow converges near the wave focal zone, while waves that approach from the southwest result in alongshore flow that diverges away from the wave focal zone. The direction and magnitude of alongshore flows are determined by a balance between the (often opposing) radiation stress and alongshore pressure gradients, consistent with observations and previous results. The largest observed morphologic evolution, vertical accretion of about 1.5 m in about 3 m water depth near the wave focal zone, occurred over a one-week period when waves from the northwest reached heights of 1.8 m. The model, with limited tuning, replicates the magnitude and spatial extent of the observed accretion and indicates that net accretion of the cross-shore profile was owing to alongshore transport from converging alongshore flows. The good agreement between the observed and modeled morphology change allows for an in-depth examination of the alongshore force balance that resulted in the sediment convergence. These results indicate that, at least in this case, a depth-averaged hydrodynamic model can replicate observed surfzone morphologic change resulting from forcing that is strongly non-uniform in the alongshore. Funding was provided by the Office of Naval

  11. 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

  12. Impact of boundary regions on the interior circulation of the California Current System in a regional modeling framework

    NASA Astrophysics Data System (ADS)

    Veneziani, M.; Edwards, C.; Moore, A.

    2008-12-01

    We use the Regional Ocean Modeling System (ROMS) to model the circulation of the California Current System (CCS) using ECCO-GODAE products to force the model at the open boundaries of the domain. We investigate the impact that lateral boundary forcing (and the boundary region in general) has on particular metrics of the interior circulation by adopting both an adjoint model and a traditional sensitivity approach. Adjoint methods are naturally suited to sensitivity studies as they provide the direct dependencies of circulation metrics on uncertainties of the model initial conditions, surface and lateral external forcing, and model parameters, but their results are only valid within the time scale during which the linearity assumption underlying adjoint models can be considered to hold. More traditional sensitivity studies must be conducted to investigate longer time scales. We describe the adjoint model results for two metrics that represent the upwelling processes of the Central California region and the mean sea level field of the coastal circulation, respectively. The spatial distribution of the adjoint sensitivity fields allows us to quantify the contribution of the boundary regions over a biweekly time scale. We investigate longer time scales by adopting two methods: 1) apply different ECCO products at the open boundaries and evaluate mean stratification changes in the CalCOFI coastal region; 2) release passive tracers at the boundaries and calculate ventilation time scales and pathways from the boundary areas to the CCS interior.

  13. 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.

  14. 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

  15. 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

  16. A dynamic opto-physiological model to effectively interpret retinal microvascular circulation

    NASA Astrophysics Data System (ADS)

    Hassan, Harnani; Hu, Sijung; Dwyer, Vincent M.

    2015-03-01

    The demand of non-invasive ocular screening is rapidly growing due to an increase of age related eye diseases worldwide. An indeed in-depth understanding of optical properties is required to elucidate nature of retinal tissue. The research aims to investigate an effective biomedical engineering approach to allow process region of interests (ROIs) in eyes to reveal physiological status. A dynamic opto-physiological model (DOPM) representing retinal microvascular circulation underlying a diffusion approximation to solve radiative transport theorem (RTT) has being developed to interpret patho-physiological phenomena. DOPM is being applied in imaging photoplethysmography (iPPG) to extract PPG signals from a series of 2D matrix images to access blood perfusion and oxygen saturation distributions. A variation of microvascular circulation could be mapped for an effectively diagnostic screening. The work presents mathematical modelling based ten layers of ocular tissue tested with four set of controlled parameters demontrated detection ratio between normal tissue damage or abnormal tissue and significant change of AC signal amplitude in these tissues. The result shows signicant change of AC signal amplitude in abnormal tissue. The preliminary results show extractable PPG signals from eye fundus video; experimented at five ROIs: whole fundus, optical disk, main vein vessel, lesion area and affected area. The outcome shows optical disk region gave a better performance compared to whole fundus region and main vein vessel. The robustness, miniaturization and artefact reduction capability of DOPM to discriminate oxygenation levels in retina could offer a new insight to access retinal patho-physiological status.

  17. Modeling the effect of Causeways on Circulation in the Banana River

    NASA Astrophysics Data System (ADS)

    Saberi, A.; Weaver, R. J.

    2015-12-01

    The Indian River Lagoon (IRL) is a restricted estuary along the east coast of Florida. Although Banana River, a 50 km long sub-basin of IRL, has an outlet to the ocean through the Port Canaveral locks, the locks remain closed when there is no passing vessel. The lack of direct ocean connection results in limited circulation, long flushing time and poor water quality. Existence of the causeways limits the circulation even more. In this study, the impact of the causeways on flushing time is studied. This study also examines the extent to which constructing a low crested weir adjacent to Port Canaveral can improve flushing in this region. ADCIRC 2DDI is forced with meteorological inputs as well as tides to simulate the hydrodynamic properties of the study area and determine the 2D depth-averaged velocity field for four separate cases: Existing System with and without consideration of the causeways, and modified system (adding a weir near port Canaveral) with and without consideration of the causeways. Passive particles are placed in Banana River, and their movement is tracked using a Lagrangian Particle Tracking Model (LPTM). Transport timescales are then computed, and residence time contours as well as pathlines of selected particles are plotted. Results indicate that the narrow raised pathway section of the causeways acts as a plate which diverts the flow direction and generates eddies in the downstream which causes the particles in the vicinity of the causeways remain in the domain for a longer duration. There is a longer residence time for the case in which the causeways are considered. The results with the added weir suggest a noticeable improvement in flushing time and residence time even for the case in which the causeways are considered in the model.

  18. 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.

  19. A GENERAL CIRCULATION MODEL FOR GASEOUS EXOPLANETS WITH DOUBLE-GRAY RADIATIVE TRANSFER

    SciTech Connect

    Rauscher, Emily; Menou, Kristen

    2012-05-10

    We present a new version of our code for modeling the atmospheric circulation on gaseous exoplanets, now employing a 'double-gray' radiative transfer scheme, which self-consistently solves for fluxes and heating throughout the atmosphere, including the emerging (observable) infrared flux. We separate the radiation into infrared and optical components, each with its own absorption coefficient, and solve standard two-stream radiative transfer equations. We use a constant optical absorption coefficient, while the infrared coefficient can scale as a power law with pressure; however, for simplicity, the results shown in this paper use a constant infrared coefficient. Here we describe our new code in detail and demonstrate its utility by presenting a generic hot Jupiter model. We discuss issues related to modeling the deepest pressures of the atmosphere and describe our use of the diffusion approximation for radiative fluxes at high optical depths. In addition, we present new models using a simple form for magnetic drag on the atmosphere. We calculate emitted thermal phase curves and find that our drag-free model has the brightest region of the atmosphere offset by {approx}12 Degree-Sign from the substellar point and a minimum flux that is 17% of the maximum, while the model with the strongest magnetic drag has an offset of only {approx}2 Degree-Sign and a ratio of 13%. Finally, we calculate rates of numerical loss of kinetic energy at {approx}15% for every model except for our strong-drag model, where there is no measurable loss; we speculate that this is due to the much decreased wind speeds in that model.

  20. Overly persistent circulation in climate models contributes to overestimated frequency and duration of heat waves and cold spells

    NASA Astrophysics Data System (ADS)

    Plavcova, Eva; Kysely, Jan

    2016-04-01

    The study examines links of summer heat waves and winter cold spells in Central Europe to atmospheric circulation and specifically its persistence in an ensemble of regional climate models (RCMs). We analyse 13 RCMs driven by the ERA-40 reanalysis and compare them against observations over 1971-2000. Using objective classification of circulation types and an efficiency coefficient with a block resampling test, we identify circulation types significantly conducive to heat waves and cold spells. We show that the RCMs have a stronger tendency to group together days with very high or low temperature and tend to simulate too many heat waves and cold spells, especially those lasting 5 days and more. Circulation types conducive to heat waves in summer are characterized by anticyclonic, southerly and easterly flow, with increasing importance of warm advection during heat waves. Winter cold spells are typically associated with easterly and anticyclonic flow, and the onset of cold spells tends to be linked to northerly and cyclonic flow with cold advection. The RCMs are generally able to reproduce the links between circulation and heat waves or cold spells, including the radiation-to-advection effect for heat waves and the opposite advection-to-radiation effect for cold spells. They capture relatively well also changes of mean temperature anomalies during sequences of given circulation types, namely the tendency towards an increase (decrease) of temperature during the types conducive to heat waves (cold spells). Since mean lengths of all circulation supertypes are overestimated in the RCMs, we conclude that the overly persistent circulation in climate models contributes to the overestimated frequency of long heat waves and cold spells. As these biases are rather general among the examined RCMs and similar drawbacks are likely to be manifested in climate model simulations for the 21st century, the results also suggest that climate change scenarios for spells of days with high

  1. Hurricane Forecasting with the High-resolution NASA Finite-volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Atlas, R.; Reale, O.; Shen, B.-W.; Lin, S.-J.; Chern, J.-D.; Putman, W.; Lee, T.; Yeh, K.-S.; Bosilovich, M.; Radakovich, J.

    2004-01-01

    A high-resolution finite-volume General Circulation Model (fvGCM), resulting from a development effort of more than ten years, is now being run operationally at the NASA Goddard Space Flight Center and Ames Research Center. The model is based on a finite-volume dynamical core with terrain-following Lagrangian control-volume discretization and performs efficiently on massive parallel architectures. The computational efficiency allows simulations at a resolution of a quarter of a degree, which is double the resolution currently adopted by most global models in operational weather centers. Such fine global resolution brings us closer to overcoming a fundamental barrier in global atmospheric modeling for both weather and climate, because tropical cyclones and even tropical convective clusters can be more realistically represented. In this work, preliminary results of the fvGCM are shown. Fifteen simulations of four Atlantic tropical cyclones in 2002 and 2004 are chosen because of strong and varied difficulties presented to numerical weather forecasting. It is shown that the fvGCM, run at the resolution of a quarter of a degree, can produce very good forecasts of these tropical systems, adequately resolving problems like erratic track, abrupt recurvature, intense extratropical transition, multiple landfall and reintensification, and interaction among vortices.

  2. The extratropical 40-day oscillation in the UCLA general circulation model. Part 1: Atmospheric angular momentum

    NASA Technical Reports Server (NTRS)

    Marcus, S. L.; Ghil, M.; Dickey, J. O.

    1994-01-01

    Variations in atmospheric angular momentum (AAM) are examined in a three-year simulation of the large-scale atmosphere with perpetual January forcing. The simulation is performed with a version of the University of California at Los Angeles (UCLA) general circulation model that contains no tropical Madden-Julian Oscillation (MJO). In addition, the results of three shorter experiments with no topography are analyzed. The three-year standard topography run contains no significant intraseasonal AAM periodicity in the tropics, consistent with the lack of the MJO, but produces a robust, 42-day AAM oscillation in the Northern Hemisphere (NH) extratropics. The model tropics undergoes a barotropic, zonally symmetric oscillation, driven by an exchange of mass with the NH extratropics. No intraseasonal periodicity is found in the average tropical latent heating field, indicating that the model oscillation is dynamically rather than thermodynamically driven. The no-mountain runs fail to produce an intraseasonal AAM oscillation, consistent with a topographic origin for the NH extratropical oscillation in the standard model. The spatial patterns of the oscillation in the 500-mb height field, and the relationship of the extratropical oscillation to intraseasonal variations in the tropics, will be discussed in Part 2 of this study.

  3. Global environmental effects of impact-generated aerosols: Results from a general circulation model

    NASA Technical Reports Server (NTRS)

    Covey, Curt; Ghan, Steven J.; Walton, John J.; Weissman, Paul R.

    1989-01-01

    Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to the three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans, not included in the one-dimensional model, substantially mitigates land surface cooling. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stages of cooling than in the one-dimensional model study. GCM-simulated climatic changes in the scenario of asteroid/comet winter are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though of course less severe, climatic changes, according to the GCM. An asteroid or comet impact would not lead to anything approaching complete global freezing, but quite reasonable to assume that impacts would dramatically alter the climate in at least a patchy sense.

  4. Modeling of a horizontal circulation open loop in two-phase helium

    NASA Astrophysics Data System (ADS)

    Bertrand, Baudouy; Anne, Bessette; Aurélien, Four

    2013-01-01

    In the process of the cryogenic cooling system design of the superconducting magnet of the R3B spectrometer, heat and mass transfer in a two-phase He I natural circulation loop with a horizontal heated section has been investigated experimentally. The experiments were conducted on a 2 m high experimental loop with a copper tube of 10 mm inner diameter uniformly heated over a length of 4 m. All data were obtained near atmospheric pressure. Evolution of the mass flow rates as a function of heat flux in steady state condition are presented and compared to a numerical model that have been developed to assist the design of such a cooling scheme. The model is based on a one-dimensional equations system, which includes mass, momentum and energy balances. It is based on the homogeneous model with a specific friction coefficient for the horizontal heated section. The model reproduces with an acceptable accuracy the experimental results and now serves as a tool for the design.

  5. The GEOS-5 Atmospheric General Circulation Model: Mean Climate and Development from MERRA to Fortuna

    NASA Technical Reports Server (NTRS)

    Molod, Andrea; Takacs, Lawrence; Suarez, Max; Bacmeister, Julio; Song, In-Sun; Eichmann, Andrew

    2012-01-01

    This report is a documentation of the Fortuna version of the GEOS-5 Atmospheric General Circulation Model (AGCM). The GEOS-5 AGCM is currently in use in the NASA Goddard Modeling and Assimilation Office (GMAO) for simulations at a wide range of resolutions, in atmosphere only, coupled ocean-atmosphere, and data assimilation modes. The focus here is on the development subsequent to the version that was used as part of NASA s Modern-Era Retrospective Analysis for Research and Applications (MERRA). We present here the results of a series of 30-year atmosphere-only simulations at different resolutions, with focus on the behavior of the 1-degree resolution simulation. The details of the changes in parameterizations subsequent to the MERRA model version are outlined, and results of a series of 30-year, atmosphere-only climate simulations at 2-degree resolution are shown to demonstrate changes in simulated climate associated with specific changes in parameterizations. The GEOS-5 AGCM presented here is the model used for the GMAO s atmosphere-only and coupled CMIP-5 simulations.

  6. A circulation modeling approach for evaluating the conditions for shoreline instabilities

    USGS Publications Warehouse

    List, Jeffrey H.; Ashton, Andrew D.

    2007-01-01

    Analytical models predict the growth (instability) of shoreline salients when deep-water waves approach the coast from highly oblique angles, contrary to classical shoreline change models in which shoreline salients can only dissipate. Using the process-based wave, circulation, and sediment transport model Delft3D, we test this prediction for simulated bathymetric and wave characteristics approximating the open-ocean conditions at Duck, North Carolina. We consider two cases: a uniform coast with a varying wave approach angle, and a bathymetry with coastal salients and a single high-angle boundary wave condition. Incident wave conditions include a swell case with no wind and a wind-wave case with active local wave regeneration by wind. The uniform-coast tests predict transport maxima at oblique wave angles for both wave cases, indicating the potential for shoreline instabilities, similar to the analytical models. However, the critical angle for instability is much higher in the wind-wave case. Our tests with coastal salients agree with previous findings that a minimum salient length scale may be required for the instability effect to be active. Here, a salient with a longshore scale of 4 km results in transport divergence (erosion; no instability) at the salient crest while an 8 km salient results in transport convergence (accretion; instability) at the crest.

  7. Regional intercomparisons of General Circulation Model predictions and historical climate data: CO/sub 2/

    SciTech Connect

    Grotch, S.L.

    1988-04-01

    This study is a detailed intercomparsion of the results produced by four different General Circulation Models (GCMs) that have been used to project the climatic consequences of a doubling of the atmospheric CO/sub 2/ concentration. The results for the models developed by groups at the National Center for Atmospheric Research (NCARCCM, Washington and Meehl, 1984), the Geophysical Fluid Dynamics Laboratory of NOAA (GFDL, Manable and Wetherald, 1987), and the Goddard Institute for Space Studies of NASA (GISS, Hansen, et al., 1984) have been described by Schlesinger and Mitchell (1985) in the DOE state-of-art (SOA) report, ''Projecting the Climatic Effects of Increasing Carbon Dioxide''. The fourth model examined here is the Oregon State University GCM (OSU, Schlesinger, 1986), results for which did not become available until after publication of the SOA. We have chosen to examine only two model variables here: (1) surface air temperature, and (2) precipation. We consider these variables for both seasonally and annually averaged periods, for both the current climatic conditions and the predicted equilibrium changes after a doubling of the CO/sub 2/ concentration. The major conclusion of this study is that, although the models often agree well comparing seasonal or annual averages over the large areas, substanial disagreements become apparent as the spatial extent is reduced, particularly when detailed regional distributions are examined. At scales below continental, the correlations observed between different model predictions are often very poor, particularly for land gridpoints during the Northern Hemisphere (NH) summer, with differences of as much as 5/degree/C between models and observations and between one model and another over relatively large areas.

  8. Evaluation of the Surface Representation of the Greenland Ice Sheet in a General Circulation Model

    NASA Technical Reports Server (NTRS)

    Cullather, Richard I.; Nowicki, Sophie M. J.; Zhao, Bin; Suarez, Max J.

    2014-01-01

    Simulated surface conditions of the Goddard Earth Observing System model, version 5 (GEOS 5) atmospheric general circulation model (AGCM) are examined for the contemporary Greenland Ice Sheet (GrIS). A surface parameterization that explicitly models surface processes including snow compaction, meltwater percolation and refreezing, and surface albedo is found to remedy an erroneous deficit in the annual net surface energy flux and provide an adequate representation of surface mass balance (SMB) in an evaluation using simulations at two spatial resolutions. The simulated 1980-2008 GrIS SMB average is 24.7+/-4.5 cm yr(- 1) water-equivalent (w.e.) at.5 degree model grid spacing, and 18.2+/-3.3 cm yr(- 1) w.e. for 2 degree grid spacing. The spatial variability and seasonal cycle of the simulation compare favorably to recent studies using regional climate models, while results from 2 degree integrations reproduce the primary features of the SMB field. In comparison to historical glaciological observations, the coarser resolution model overestimates accumulation in the southern areas of the GrIS, while the overall SMB is underestimated. These changes relate to the sensitivity of accumulation and melt to the resolution of topography. The GEOS-5 SMB fields contrast with available corresponding atmospheric models simulations from the Coupled Model Intercomparison Project (CMIP5). It is found that only a few of the CMIP5 AGCMs examined provide significant summertime runoff, a dominant feature of the GrIS seasonal cycle. This is a condition that will need to be remedied if potential contributions to future eustatic change from polar ice sheets are to be examined with GCMs.

  9. Space weather circulation model of plasma clouds as background radiation medium of space environment.

    NASA Astrophysics Data System (ADS)

    Kalu, A. E.

    A model for Space Weather (SW) Circulation with Plasma Clouds as background radiation medium of Space Environment has been proposed and discussed. Major characteristics of the model are outlined and the model assumes a baroclinic Space Environment in view of observed pronounced horizontal electron temperature gradient with prevailing weak vertical temperature gradient. The primary objective of the study is to be able to monitor and realistically predict on real- or near real-time SW and Space Storms (SWS) affecting human economic systems on Earth as well as the safety and Physiologic comfort of human payload in Space Environment in relation to planned increase in human space flights especially with reference to the ISS Space Shuttle Taxi (ISST) Programme and other prolonged deep Space Missions. Although considerable discussions are now available in the literature on SW issues, routine Meteorological operational applications of SW forecast data and information for Space Environment are still yet to receive adequate attention. The paper attempts to fill this gap in the literature of SW. The paper examines the sensitivity and variability in 3-D continuum of Plasmas in response to solar radiation inputs into the magnetosphere under disturbed Sun condition. Specifically, the presence of plasma clouds in the form of Coronal Mass Ejections (CMEs) is stressed as a major source of danger to Space crews, spacecraft instrumentation and architecture charging problems as well as impacts on numerous radiation - sensitive human economic systems on Earth. Finally, the paper considers the application of model results in the form of effective monitoring of each of the two major phases of manned Spaceflights - take-off and re-entry phases where all-time assessment of spacecraft transient ambient micro-incabin and outside Space Environment is vital for all manned Spaceflights as recently evidenced by the loss of vital information during take-off of the February 1, 2003 US Columbia

  10. Modelling study of three-dimensional circulation and particle movement over the Sable Gully of Nova Scotia

    NASA Astrophysics Data System (ADS)

    Shan, Shiliang; Sheng, Jinyu; Greenan, Blair John William

    2014-01-01

    The Sable Gully is a broad deep underwater canyon located to the east of Sable Island on the edge of the Scotian Shelf. Being the home of many marine species including the endangered Northern Bottlenose Whale, the Gully was designated as a marine protected area (MPA) in 2004. Better understanding of physical environmental conditions over this MPA is needed for sustainable ecosystem management. In this study, a multi-nested ocean circulation model and a particle tracking model are used to examine the three-dimensional (3D) circulation and movement of particles carried passively by the flow over the Sable Gully. The 3D circulation model is driven by tides, wind, and surface heat/freshwater fluxes. The model performance is assessed by comparing the results with the previous numerical tidal results and current meter observations made in the Gully. The simulated tidal circulation over the Gully and adjacent waters is relatively strong on shallow banks and relatively weak on the continental slope. Below the depth of the Gully rim ( ˜ 200 m), the tidal currents are constrained by the thalweg of the Gully and amplified toward the Gully head. The simulated subtidal circulation in the Gully has a complex spatial structure and significant seasonal variability. The simulated time-dependent 3D flow fields are then used in a particle tracking model to study the particle movements, downstream and upstream areas, and residence time of the Gully. Based on the movements of particles released at the depth of the Gully rim and tracked forward in time, the e-folding residence time is estimated to be about 7 and 13 days in February and August 2006, respectively. The Gully flanks are identified as high retention areas with the typical residence time of 10 and 20 days in February and August 2006, respectively. Tracking particles with and without tides reveals that tidal circulation reduces the value of residence time in the Gully, particularly along the Gully flanks.

  11. Adaptive scaling model of the main pycnocline and the associated overturning circulation

    NASA Astrophysics Data System (ADS)

    Fuckar, Neven-Stjepan

    This thesis examines a number of crucial factors and processes that control the structure of the main pycnocline and the associated overturning circulation that maintains the ocean stratification. We construct an adaptive scaling model: a semi-empirical low-order theory based on the total transformation balance that linearly superimposes parameterized transformation rate terms of various mechanisms that participate in the water-mass conversion between the warm water sphere and the cold water sphere. The depth of the main pycnocline separates the light-water domain from the dense-water domain beneath the surface, hence we introduce a new definition in an integral form that is dynamically based on the large-scale potential vorticity (i.e., vertical density gradient is selected for the kernel function of the normalized vertical integral). We exclude the abyssal pycnocline from our consideration and limit our domain of interest to the top 2 km of water column. The goal is to understand the controlling mechanisms, and analytically predict and describe a wide spectrum of ocean steady states in terms of key large-scale indices relevant for understanding the ocean's role in climate. A devised polynomial equation uses the average depth of the main pycnocline as a single unknown (the key vertical scale of the upper ocean stratification) and gives us an estimate for the northern hemisphere deep water production and export across the equator from the parts of this equation. The adaptive scaling model aims to elucidate the roles of a limited number of dominant processes that determine some key upper ocean circulation and stratification properties. Additionally, we use a general circulation model in a series of simplified single-basin ocean configurations and surface forcing fields to confirm the usefulness of our analytical model and further clarify several aspects of the upper ocean structure. An idealized numerical setup, containing all the relevant physical and dynamical

  12. Short ensembles: An Efficient Method for Discerning Climate-relevant Sensitivities in Atmospheric General Circulation Models

    SciTech Connect

    Wan, Hui; Rasch, Philip J.; Zhang, Kai; Qian, Yun; Yan, Huiping; Zhao, Chun

    2014-09-08

    This paper explores the feasibility of an experimentation strategy for investigating sensitivities in fast components of atmospheric general circulation models. The basic idea is to replace the traditional serial-in-time long-term climate integrations by representative ensembles of shorter simulations. The key advantage of the proposed method lies in its efficiency: since fewer days of simulation are needed, the computational cost is less, and because individual realizations are independent and can be integrated simultaneously, the new dimension of parallelism can dramatically reduce the turnaround time in benchmark tests, sensitivities studies, and model tuning exercises. The strategy is not appropriate for exploring sensitivity of all model features, but it is very effective in many situations. Two examples are presented using the Community Atmosphere Model version 5. The first example demonstrates that the method is capable of characterizing the model cloud and precipitation sensitivity to time step length. A nudging technique is also applied to an additional set of simulations to help understand the contribution of physics-dynamics interaction to the detected time step sensitivity. In the second example, multiple empirical parameters related to cloud microphysics and aerosol lifecycle are perturbed simultaneously in order to explore which parameters have the largest impact on the simulated global mean top-of-atmosphere radiation balance. Results show that in both examples, short ensembles are able to correctly reproduce the main signals of model sensitivities revealed by traditional long-term climate simulations for fast processes in the climate system. The efficiency of the ensemble method makes it particularly useful for the development of high-resolution, costly and complex climate models.

  13. Modeling the hydrothermal circulation and the hydrogen production at the Rainbow site with Cast3M

    NASA Astrophysics Data System (ADS)

    Perez, F.; Mügler, C.; Charlou, J.; Jean-baptiste, P.

    2012-12-01

    On the Mid-Atlantic Ridge, the Rainbow venting site is described as an ultramafic-hosted active hydrothermal site and releases high fluxes of methane and hydrogen [1, 2]. This behavior has first been interpreted as the result of serpentinization processes. But geochemical reactions involving olivine and plagioclase assemblages, and leading to chlorite, tremolite, talc and magnetite assemblages, could contribute to the observed characteristics of the exiting fluid [2]. The predominance of one of these geochemical reactions or their coexistence strongly depend on the hydrothermal fluid circulation. We developed and validated a 2D/3D numerical model using a Finite Volume method to simulate heat driven fluid flows in the framework of the Cast3M code [3, 4]. We also developed a numerical model for hydrogen production and transport that is based on experimental studies of the serpentinization processes [5-6]. This geochemical model takes into account the exothermic and water-consuming behavior of the serpentinization reaction and it can be coupled to our thermo-hydrogeological model. Our simulations provide temperatures, mass fluxes and venting surface areas very close to those estimated in-situ [7]. We showed that a single-path model [8] was necessary to simulate high values such as the in-situ measured temperatures and estimated water mass fluxes of the Rainbow site [7]. This single-path model will be used to model the production and transport of hydrogen at the Rainbow hydrothermal site. References [1]Charlou et al. (2010) AGU Monograph series. [2]Seyfried et al. (2011) Geochim. Cosmochim. Acta 75, 1574-1593. [3]http://www-cast3m.cea.fr. [4]Martin & Fyfe (1970) Chem. Geol. 6, 185-202. [5] Marcaillou et al. (2011) Earth and Planet. Sci. Lett. 303, 281-290. [6]Malvoisin et al. (2012) JGR, 117, B01104. [7]Perez et al. (2012) submited to Computational Geosciences. [8]Lowell & Germanovich (2004) AGU, Washington DC, USA.

  14. A Tailored Computation of the Mean Dynamic Topography for a Consistent Integration into Ocean Circulation Models

    NASA Astrophysics Data System (ADS)

    Becker, S.; Losch, M.; Brockmann, J. M.; Freiwald, G.; Schuh, W.-D.

    2014-11-01

    Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography—the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99-110, 2012; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie 2012). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the

  15. Successive bifurcations in a shallow-water model applied to the wind-driven ocean circulation

    NASA Astrophysics Data System (ADS)

    Speich, S.; Dijkstra, H.; Ghil, M.

    Climate - the "coarse-gridded" state of the coupled ocean - atmosphere system - varies on many time and space scales. The challenge is to relate such variation to specific mechanisms and to produce verifiable quantitative explanations. In this paper, we study the oceanic component of the climate system and, in particular, the different circulation regimes of the mid-latitude win driven ocean on the interannual time scale. These circulations are dominated by two counterrotating, basis scale gyres: subtropical and subpolar. Numerical techniques of bifurcation theory are used to stud the multiplicity and stability of the steady-state solution of a wind-driven, double-gyre, reduced-gravity, shallow water model. Branches of stationary solutions and their linear stability are calculated systematically as parameter are varied. This is one of the first geophysical studies i which such techniques are applied to a dynamical system with tens of thousands of degrees of freedom. Multiple stationary solutions obtain as a result of nonlinear interactions between the two main recirculating cell (cyclonic and anticyclonic) of the large- scale double-gyre flow. These equilibria appear for realistic values of the forcing and dissipation parameters. They undergo Hop bifurcation and transition to aperiodic solutions eventually occurs. The periodic and chaotic behaviour is probably related to an increased number of vorticity cells interaction with each other. A preliminary comparison with observations of the Gulf Stream and Kuroshio Extensions suggests that the intern variability of our simulated mid-latitude ocean is a important factor in the observed interannual variability o these two current systems.

  16. Jupiter Thermospheric General Circulation Model (JTGCM): Global Structure and Dynamics Driven by Auroral and Joule Heating

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; J. Il. Waite, Jr.; Majeed, T.

    2005-01-01

    A growing multispectral database plus recent Galileo descent measurements are being used to construct a self-consistent picture of the Jupiter thermosphere/ionosphere system. The proper characterization of Jupiter s upper atmosphere, embedded ionosphere, and auroral features requires the examination of underlying processes, including the feedbacks of energetics, neutral-ion dynamics, composition, and magnetospheric coupling. A fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) has been developed and exercised to address global temperatures, three-component neutral winds, and neutral-ion species distributions. The domain of this JTGCM extends from 20-microbar (capturing hydrocarbon cooling) to 1.0 x 10(exp -4) nbar (including aurora/Joule heating processes). The resulting JTGCM has been fully spun-up and integrated for greater than or equal to40 Jupiter rotations. Results from three JTGCM cases incorporating moderate auroral heating, ion drag, and moderate to strong Joule heating processes are presented. The neutral horizontal winds at ionospheric heights vary from 0.5 km/s to 1.2 km/s, atomic hydrogen is transported equatorward, and auroral exospheric temperatures range from approx.1200-1300 K to above 3000 K, depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo AS1 data set. The best fit to the Galileo data implies that the major energy source for maintaining the equatorial temperatures is due to dynamical heating induced by the low-latitude convergence of the high-latitude-driven thermospheric circulation. Overall, the Jupiter thermosphere/ionosphere system is highly variable and is shown to be strongly dependent on magnetospheric coupling which regulates Joule heating.

  17. Correction of Excessive Precipitation Over Steep and High Mountains in a General Circulation Model

    NASA Technical Reports Server (NTRS)

    Chao, Winston C.

    2012-01-01

    Excessive precipitation over steep and high mountains (EPSM) is a well-known problem in GCMs and meso-scale models. This problem impairs simulation and data assimilation products. Among the possible causes investigated in this study, we found that the most important one, by far, is a missing upward transport of heat out of the boundary layer due to the vertical circulations forced by the daytime upslope winds, which are forced by the heated boundary layer on subgrid-scale slopes. These upslope winds are associated with large subgrid-scale topographic variation, which is found over steep and high mountains. Without such subgridscale heat ventilation, the resolvable-scale upslope flow in the boundary layer generated by surface sensible heat flux along the mountain slopes is excessive. Such an excessive resolvablescale upslope flow combined with the high moisture content in the boundary layer results in excessive moisture transport toward mountaintops, which in turn gives rise to EPSM. Other possible causes of EPSM that we have investigated include 1) a poorly-designed horizontal moisture flux in the terrain-following coordinates, 2) the condition for cumulus convection being too easily satisfied at mountaintops, 3) the presence of conditional instability of the computational kind, and 4) the absence of blocked flow drag. These are all minor or inconsequential. We have parameterized the ventilation effects of the subgrid-scale heated-slope-induced vertical circulation (SHVC) by removing heat from the boundary layer and depositing it in layers higher up when the topographic variance exceeds a critical value. Test results using NASA/Goddard's GEOS-S GCM have shown that this largely solved the EPSM problem.

  18. Understanding Thiel embalming in pig kidneys to develop a new circulation model.

    PubMed

    Willaert, Wouter; De Vos, Marie; Van Hoof, Tom; Delrue, Louke; Pattyn, Piet; D'Herde, Katharina

    2015-01-01

    The quality of tissue preservation in Thiel embalmed bodies varies. Research on the administered embalming volume and its vascular distribution may elucidate one of the mechanisms of tissue preservation and allow for new applications of Thiel embalming. Vascular embalming with (group 1, n = 15) or without (group 2, n = 20) contrast agent was initiated in pig kidneys. The distribution of Thiel embalming solution in group 1 was visualized using computed tomography. The kidneys in both groups were then immersed in concentrated salt solutions to reduce their weight and volume. Afterwards, to mimic a lifelike circulation in the vessels, group 2 underwent pump-driven reperfusion for 120 minutes with either paraffinum perliquidum or diluted polyethylene glycol. The circulation was imaged with computed tomography. All of the kidneys were adequately preserved. The embalming solution spread diffusely in the kidney, but fluid accumulation was present. Subsequent immersion in concentrated salt solutions reduced weight (P < 0.01) and volume (P < 0.01). Reperfusion for 120 minutes was established in group 2. Paraffinum perliquidum filled both major vessels and renal tissue, whereas diluted polyethylene glycol spread widely in the kidney. There were no increases in weight (P = 0.26) and volume (P = 0.79); and pressure further decreased (P = 0.032) after more than 60 minutes of reperfusion with paraffinum perliquidum, whereas there were increases in weight (P = 0.005), volume (P = 0.032) and pressure (P < 0.0001) after reperfusion with diluted polyethylene glycol. Arterial embalming of kidneys results in successful preservation due to complete parenchymatous spreading. More research is needed to determine whether other factors affect embalming quality. Dehydration is an effective method to regain the organs' initial status. Prolonged vascular reperfusion with paraffinum perliquidum can be established in this model without increases in weight, volume and pressure.

  19. Understanding Thiel Embalming in Pig Kidneys to Develop a New Circulation Model

    PubMed Central

    Willaert, Wouter; De Vos, Marie; Van Hoof, Tom; Delrue, Louke; Pattyn, Piet; D’Herde, Katharina

    2015-01-01

    The quality of tissue preservation in Thiel embalmed bodies varies. Research on the administered embalming volume and its vascular distribution may elucidate one of the mechanisms of tissue preservation and allow for new applications of Thiel embalming. Vascular embalming with (group 1, n = 15) or without (group 2, n = 20) contrast agent was initiated in pig kidneys. The distribution of Thiel embalming solution in group 1 was visualized using computed tomography. The kidneys in both groups were then immersed in concentrated salt solutions to reduce their weight and volume. Afterwards, to mimic a lifelike circulation in the vessels, group 2 underwent pump-driven reperfusion for 120 minutes with either paraffinum perliquidum or diluted polyethylene glycol. The circulation was imaged with computed tomography. All of the kidneys were adequately preserved. The embalming solution spread diffusely in the kidney, but fluid accumulation was present. Subsequent immersion in concentrated salt solutions reduced weight (P < 0.01) and volume (P < 0.01). Reperfusion for 120 minutes was established in group 2. Paraffinum perliquidum filled both major vessels and renal tissue, whereas diluted polyethylene glycol spread widely in the kidney. There were no increases in weight (P = 0.26) and volume (P = 0.79); and pressure further decreased (P = 0.032) after more than 60 minutes of reperfusion with paraffinum perliquidum, whereas there were increases in weight (P = 0.005), volume (P = 0.032) and pressure (P < 0.0001) after reperfusion with diluted polyethylene glycol. Arterial embalming of kidneys results in successful preservation due to complete parenchymatous spreading. More research is needed to determine whether other factors affect embalming quality. Dehydration is an effective method to regain the organs’ initial status. Prolonged vascular reperfusion with paraffinum perliquidum can be established in this model without increases in weight, volume and pressure. PMID:25806527

  20. On the dynamics of droughts in northeast Brazil - Observations, theory and numerical experiments with a general circulation model

    NASA Technical Reports Server (NTRS)

    Moura, A. D.; Shukla, J.

    1981-01-01

    The establishment of a thermally direct local circulation which has its ascending branch at about 10 deg N and its descending branch over northeast Brazil and the adjoining oceanic region is proposed as a possible mechanism for the occurrence of severe droughts over this Brazilian region. The driving for this anomalous circulation is provided by enhanced moist convection due to the effect of warmer sea surface anomalies over the northern tropical Atlantic and cooling associated with colder sea surface temperature anomalies in the southern tropical Atlantic. A simple primitive equation model is used to calculate the frictionally-controlled and thermally-driven circulation due to a prescribed heating function in a resting atmosphere, and a series of numerical experiments are carried out to test the sensitivity of the Goddard Laboratory's model to prescribed sea surface temperature anomalies over the tropical Atlantic.

  1. A Python Implementation of an Intermediate-Level Tropical Circulation Model and Implications for How Modeling Science is Done

    NASA Astrophysics Data System (ADS)

    Lin, J. W. B.

    2015-12-01

    Historically, climate models have been developed incrementally and in compiled languages like Fortran. While the use of legacy compiledlanguages results in fast, time-tested code, the resulting model is limited in its modularity and cannot take advantage of functionalityavailable with modern computer languages. Here we describe an effort at using the open-source, object-oriented language Pythonto create more flexible climate models: the package qtcm, a Python implementation of the intermediate-level Neelin-Zeng Quasi-Equilibrium Tropical Circulation model (QTCM1) of the atmosphere. The qtcm package retains the core numerics of QTCM1, written in Fortran, to optimize model performance but uses Python structures and utilities to wrap the QTCM1 Fortran routines and manage model execution. The resulting "mixed language" modeling package allows order and choice of subroutine execution to be altered at run time, and model analysis and visualization to be integrated in interactively with model execution at run time. This flexibility facilitates more complex scientific analysis using less complex code than would be possible using traditional languages alone and provides tools to transform the traditional "formulate hypothesis → write and test code → run model → analyze results" sequence into a feedback loop that can be executed automatically by the computer.

  2. North Atlantic Circulation

    NASA Astrophysics Data System (ADS)

    Molinari, R.; Bryan, K.; Schott, F.

    The intensity of the North Atlantic winddriven and thermohaline circulation and the close proximity of many oceanographic installations make the North Atlantic a particularly favored region of the world ocean from the standpoint of research in ocean circulation. Recent increases in available data and advances in numerical modeling techniques served as the impetus to convene a joint workshop of modelers and observers working on the North Atlantic with the Scientific Committee on Oceanic Research (SCOR) Working Group (WG) 68 (“North Atlantic Circulation”). Goals of the workshop were to provide an update on data sets and models and to discuss the poleward heat flux problem and possible monitoring strategies. The joint Workshop/SCOR WG-68 meeting was convened by F. Schott (chairman of the working group; Rosenstiel School of Marine and Atmospheric Science, Miami, Fla.), K. Bryan (National Oceanic and Atmospheric Administration/ Geophysical Fluid Dynamics Laboratory (NOAA/GFDL)), and R. Molinari (NOAA/Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML)).

  3. A numerical model of stratified circulation in Indian Arm, British Columbia

    NASA Astrophysics Data System (ADS)

    Dunbar, Donald S.; Burling, R. W.

    1987-11-01

    A laterally integrated numerical model has been developed for the study of stratified circulation in inlets. The model is time dependent and includes advective terms, horizontal and vertical turbulent diffusion of momentum and salt, and variations in width and depth. Initial and boundary conditions based on winter measurements in Burrard Inlet and Indian Arm were used to study the inlet's response to tidal forcing. The friction term was tuned to match calculated and observed dissipation rates. Evidence for a standing wave pattern in the response of the M2 and K1 tidal constituents is discussed. A comparison of model results with cyclesonde current meter time series at two locations in Indian Arm is consistent with resonance. A modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes, with the former dominating near the sill and the latter dominating in the deep basin. Second-mode energy was significant for the K1 at some locations.

  4. The implementation and validation of improved land-surface hydrology in an atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Johnson, Kevin D.; Entekhabi, Dara; Eagleson, Peter S.

    1993-01-01

    New land-surface hydrologic parameterizations are implemented into the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: 1) runoff and evapotranspiration functions that include the effects of subgrid-scale spatial variability and use physically based equations of hydrologic flux at the soil surface and 2) a realistic soil moisture diffusion scheme for the movement of water and root sink in the soil column. A one-dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three-dimensional GCM. Results of the final simulation with the GISS GCM and the new land-surface hydrology indicate that the runoff rate, especially in the tropics, is significantly improved. As a result, the remaining components of the heat and moisture balance show similar improvements when compared to observations. The validation of model results is carried from the large global (ocean and land-surface) scale to the zonal, continental, and finally the regional river basin scales.

  5. A logistic model for the detection of circulating tumour cells in human metastatic colorectal cancer

    PubMed Central

    Barbazán, Jorge; Vieito, María; Abalo, Alicia; Alonso-Alconada, Lorena; Muinelo-Romay, Laura; Alonso-Nocelo, Marta; León, Luís; Candamio, Sonia; Gallardo, Elena; Anido, Urbano; Doll, Andreas; los Ángeles Casares, María; Gómez-Tato, Antonio; Abal, Miguel; López-López, Rafael

    2012-01-01

    The accuracy in the diagnosis of metastatic colorectal cancer (mCRC) represents one of the challenges in the clinical management of patients. The detection of circulating tumour cells (CTC) is becoming a promising alternative to current detection techniques, as it focuses on one of the players of the metastatic disease and it should provide with more specific and sensitive detection rates. Here, we describe an improved method of detection of CTC from mCRC patients by combining immune-enrichment, optimal purification of RNA from very low cell numbers, and the selection of accurate PCR probes. As a result, we obtained a logistic model that combines GAPDH and VIL1 normalized to CD45 rendering powerful results in the detection of CTC from mCRC patients (AUROC value 0.8599). We further demonstrated the utility of this model at the clinical setting, as a reliable prognosis tool to determine progression-free survival in mCRC patients. Overall, we developed a strategy that ameliorates the specificity and sensitivity in the detection of CTC, resulting in a robust and promising logistic model for the clinical management of metastatic colorectal cancer patients. PMID:22304365

  6. Modelling monthly precipitation with circulation weather types for a dense network of stations over Iberia

    NASA Astrophysics Data System (ADS)

    Cortesi, N.; Trigo, R. M.; Gonzalez-Hidalgo, J. C.; Ramos, A. M.

    2013-02-01

    Precipitation over the Iberian Peninsula (IP) is highly variable and shows large spatial contrasts between wet mountainous regions to the north, and dry regions in the inland plains and southern areas. In this work, we modelled the relationship between atmospheric circulation weather types (WTs) and monthly precipitation for the wet half of the year (October to May) using a 10 km grid derived from a high-density dataset for the IP (3030 precipitation series, overall mean density one station each 200 km2). We detected two spatial gradients in the relationship between WTs and precipitation. The percentage of monthly precipitation explained by WTs varies from northwest (higher variance explained) to southeast (lower variance explained). Additionally, in the IP the number of WTs that contribute significantly to monthly precipitation increase systematically from east to west. Generally speaking, the model performance is better to the west than to the east where the WTs approach produce the less accurate results. We applied the WTs modelling approach to reconstruct the long-term precipitation time series for three major stations of Iberia (Lisbon, Madrid, Valencia).

  7. Tropical precipitation regimes and mechanisms of regime transitions: contrasting two aquaplanet general circulation models

    NASA Astrophysics Data System (ADS)

    Oueslati, Boutheina; Bellon, Gilles

    2013-05-01

    The atmospheric general circulation models ARPEGE-climate and LMDz are used in an aquaplanet configuration to study the response of a zonally symmetric atmosphere to a range of sea surface temperature (SST) forcing. We impose zonally-symmetric SST distributions that are also symmetric about the equator, with varying off-equatorial SST gradients. In both models, we obtain the characteristic inter-tropical convergence zone (ITCZ) splitting that separates two regimes of equilibrium (in terms of precipitations): one with one ITCZ over the equator for large SST gradients in the tropics, and one with a double ITCZ for small tropical SST gradients. Transition between these regimes is mainly driven by changes in the low-level convergence that are forced by the SST gradients. Model-dependent, dry and moist feedbacks intervene to reinforce or weaken the effect of the SST forcing. In ARPEGE, dry advective processes reinforce the SST forcing, while a competition between sensible heat flux and convective cooling provides a complex feedback on the SST forcing in the LMDz. It is suggested that these feedbacks influence the location of the transition in the parameter range.

  8. A Comparison between a GFDL General Circulation Model and Observations using Harmonic Analysis

    NASA Astrophysics Data System (ADS)

    Taghavi, F.

    2010-09-01

    One of the most important features in analyzing the climatology of any region is to study the precipitation and its periodicity of different harmonics in order to investigate the behavior of the observed data. In this study using precipitation values obtained from the 20C3M (run1) experiment of the GFDL general circulation model (CM2.1) and CPC Merged Analysis of Precipitation (CMAP) from NCEP, harmonic analysis has been employed to study the seasonal variation of precipitation over the Middle East (20°-40°N, 30°-65°E).The monthly precipitation values were averaged over a 25-year integration, producing a dataset 12 monthly for each grid locations. The annual mean and seasonal variance for each grid obtained from two dataset. Maps of the first, second and third harmonic amplitudes and phases provide a useful source of comparison between model output and observational data. Results show that the method of harmonic analysis allows a more analytical comparison between model predictions and data than the conventional approach of representing the annual march in the form of a curve of mean monthly rainfall amounts. The method delineates regional boundaries of the various precipitation regimes in the Middle East.A comparison of the simulated and observed values indicate that the GCM fails to capture a significant amount of the regional detail in precipitation climatology in the South of Middle East when its results are decomposed by harmonic analysis.

  9. GCM (general circulation model)-data intercomparison: The good news and the bad

    SciTech Connect

    Grotch, S.L.

    1990-09-01

    General circulation models (GCMs) are being actively used to assess possible climate change due to increasing greenhouse gas concentrations. Because such simulations provide detailed climatic predictions at a wide range of scales, they are of particular interest to those making regional assessments of climatic change. It is especially important that workers using the results of such simulations be aware of some of the limitations of these results. In this study some of the positive results from these model simulations will be shown and some of the deficiencies will also be highlighted. Following an introductory section describing the nature of GCM climate simulations the issue of the spatial scales of such simulations is examined. A comparison of the results of seven GCM simulations of the current climate and the predictions of these models for the changes due to a doubling of CO{sub 2} will be discussed. In these intercomparisons, the spatial scale over which the results are compared varies from global to zonal (longitudinally averaged at a given latitude) to individual slices through the data along specified latitudes or longitudes. Finally, the dangers and pitfalls of relying on simple averages will be highlighted. 19 refs., 9 figs., 1 tab.

  10. The annual cycle of stratospheric water vapor in a general circulation model

    NASA Technical Reports Server (NTRS)

    Mote, Philip W.

    1995-01-01

    The application of general circulation models (GCM's) to stratospheric chemistry and transport both permits and requires a thorough investigation of stratospheric water vapor. The National Center for Atmospheric Research has redesigned its GCM, the Community Climate Model (CCM2), to enable studies of the chemistry and transport of tracers including water vapor; the importance of water vapor to the climate and chemistry of the stratosphere requires that it be better understood in the atmosphere and well represented in the model. In this study, methane is carried as a tracer and converted to water; this simple chemistry provides an adequate representation of the upper stratospheric water vapor source. The cold temperature bias in the winter polar stratosphere, which the CCM2 shares with other GCM's, produces excessive dehydration in the southern hemisphere, but this dry bias can be ameliorated by setting a minimum vapor pressure. The CCM2's water vapor distribution and seasonality compare favorably with observations in many respects, though seasonal variations including the upper stratospheric semiannual oscillation are generally too small. Southern polar dehydration affects midlatitude water vapor mixing ratios by a few tenths of a part per million, mostly after the demise of the vortex. The annual cycle of water vapor in the tropical and northern midlatitude lower stratosphere is dominated by drying at the tropical tropopause. Water vapor has a longer adjustment time than methane and had not reached equilibrium at the end of the 9 years simulated here.

  11. Wave intensity analysis of a computational model of the pulmonary circulation

    NASA Astrophysics Data System (ADS)

    Hill, Nicholas A.; Qureshi, Muhammad Umar

    2015-11-01

    A multiscale computational model has been developed to predict flow and pressure in the pulmonary circulation, in which the flow and pressure in the smaller blood vessels are described using linearised equations in pairs of asymmetric structured trees joined at the roots. The geometric and elastic properties of all the blood vessels are described by physiological parameters. Magnetic resonance imaging (MRI) is used to determine the geometry of the large pulmonary arteries and veins, and to measure the cardiac output from the right ventricle. The flow in the large blood vessels is solved using a Lax-Wendroff scheme, and the admittances of the structured trees provide the boundary conditions linking each large artery to its respective large vein. The results of simulating various pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment of circulatory diseases within the lung. We use wave intensity analysis to study the propagation of forward and backward, compression and decompression waves in our model. The approximations for the pulse wave velocity used in experiments on wave intensity analysis are assessed, and reflected waves lower the peak pressure in the right ventricle.

  12. The implementation and validation of improved landsurface hydrology in an atmospheric general circulation model

    NASA Technical Reports Server (NTRS)

    Johnson, Kevin D.; Entekhabi, Dara; Eagleson, Peter S.

    1991-01-01

    Landsurface hydrological parameterizations are implemented in the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: (1) runoff and evapotranspiration functions that include the effects of subgrid scale spatial variability and use physically based equations of hydrologic flux at the soil surface, and (2) a realistic soil moisture diffusion scheme for the movement of water in the soil column. A one dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three dimensional GCM. Results of the final simulation with the GISS GCM and the new landsurface hydrology indicate that the runoff rate, especially in the tropics is significantly improved. As a result, the remaining components of the heat and moisture balance show comparable improvements when compared to observations. The validation of model results is carried from the large global (ocean and landsurface) scale, to the zonal, continental, and finally the finer river basin scales.

  13. The Advancement Value Chain: An Exploratory Model

    ERIC Educational Resources Information Center

    Leonard, Edward F., III

    2005-01-01

    Since the introduction of the value chain concept in 1985, several varying, yet virtually similar, value chains have been developed for the business enterprise. Shifting to higher education, can a value chain be found that links together the various activities of advancement so that an institution's leaders can actually look at the philanthropic…

  14. Predicting Career Advancement with Structural Equation Modelling

    ERIC Educational Resources Information Center

    Heimler, Ronald; Rosenberg, Stuart; Morote, Elsa-Sofia

    2012-01-01

    Purpose: The purpose of this paper is to use the authors' prior findings concerning basic employability skills in order to determine which skills best predict career advancement potential. Design/methodology/approach: Utilizing survey responses of human resource managers, the employability skills showing the largest relationships to career…

  15. Advanced Placement: Model Policy Components. Policy Analysis

    ERIC Educational Resources Information Center

    Zinth, Jennifer

    2016-01-01

    Advanced Placement (AP), launched in 1955 by the College Board as a program to offer gifted high school students the opportunity to complete entry-level college coursework, has since expanded to encourage a broader array of students to tackle challenging content. This Education Commission of the State's Policy Analysis identifies key components of…

  16. Influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.

    2007-11-01

    Satellite imagery shows that there was substantial variability in the sea ice extent in the Ross Sea during 2001-2003. Much of this variability is thought to be due to several large icebergs that moved through the area during that period. The effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model. It would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs. Here, sea ice concentration is specified from satellite observations. To examine the effects of changes in sea ice due to iceberg C-19, simulations were performed using either climatological ice concentrations or the observed ice for that period. The heat balance around the Ross Sea Polynya (RSP) shows that the dominant term in the surface heat budget is the net exchange with the atmosphere, but advection of oceanic warm water is also important. The area average annual basal melt rate beneath the Ross Ice Shelf is reduced by 12% in the observed sea ice simulation. The observed sea ice simulation also creates more High-Salinity Shelf Water. Another simulation was performed with observed sea ice and a fixed iceberg representing B-15A. There is reduced advection of warm surface water during summer from the RSP into McMurdo Sound due to B-15A, but a much stronger reduction is due to the late opening of the RSP in early 2003 because of C-19.

  17. Numerical Modeling of Reactive Multiphase Flow for FCC and Hot Gas Desulfurization Circulating Fluidized Beds

    SciTech Connect

    2005-07-01

    This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFB riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.

  18. Role of wetlands in attenuation of storm surges using coastal circulation model (ADCIRC), Chesapeake Bay region

    NASA Astrophysics Data System (ADS)

    Deb, Mithun; Ferreira, Celso; Lawler, Seth

    2014-05-01

    The Chesapeake Bay, Virginia is subject to storm surge from extreme weather events nearly year-round; from tropical storms and hurricanes during the summer and fall, (e.g., hurricanes Isabel [2003] and Sandy [2012]), and from nor'easters during the winter (e.g., winter storms Nemo and Saturn [2013]). Coastal wetlands can deliver acute fortification against incoming hurricane storm surges. Coastal wetlands and vegetation shape the hydrodynamics of storm surge events by retaining water and slowing the propagation of storm surge, acting as a natural barrier to flooding. Consequently, a precise scheme to quantify the effect of wetlands on coastal surge levels was also prerequisite. Two wetland sites were chosen in the Chesapeake Bay region for detailed cataloging of vegetation characteristics, including: height, stem diameter, and density. A framework was developed combining these wetlands characterizations with numerical simulations. Storms surges were calculated using Coastal circulation model (ADCIRC) coupled to a wave model (SWAN) forced by an asymmetric hurricane vortex model using an unstructured mesh (comprised of 1.8 million nodes) under a High Performance Computing environment. The Hurricane Boundary Layer (HBL) model was used to compute wind and pressure fields for historical tropical storms and for all of the synthetic storms. Wetlands were characterized in the coupled numerical models by bathymetric and frictional resistance. Multiple model simulations were performed using historical hurricane data and hypothetical storms to compare the predicted storm surge inundation resulting from various levels of wetlands expansion or reduction. The results of these simulations demonstrate the efficacy of wetlands in storm surge attenuation and also the outcome will scientifically support planning of wetlands restoration projects with multi-objective benefits for society.

  19. The Madden-Julian oscillation in ECHAM4 coupled and uncoupled general circulation models

    DOE PAGES

    Sperber, Kenneth R.; Gualdi, Silvio; Legutke, Stephanie; Gayler, Veronika

    2005-06-29

    The Madden-Julian oscillation (MJO) dominates tropical variability on timescales of 30–70 days. During the boreal winter/spring, it is manifested as an eastward propagating disturbance, with a strong convective signature over the eastern hemisphere. The space–time structure of the MJO is analyzed using simulations with the ECHAM4 atmospheric general circulation model run with observed monthly mean sea-surface temperatures (SSTs), and coupled to three different ocean models. The coherence of the eastward propagation of MJO convection is sensitive to the ocean model to which ECHAM4 is coupled. For ECHAM4/OPYC and ECHO-G, models for which ~100 years of daily data is available, Montemore » Carlo sampling indicates that their metrics of eastward propagation are different at the 1% significance level. The flux-adjusted coupled simulations, ECHAM4/OPYC and ECHO-G, maintain a more realistic mean-state, and have a more realistic MJO simulation than the nonadjusted scale interaction experiment (SINTEX) coupled runs. The SINTEX model exhibits a cold bias in Indian Ocean and tropical West Pacific Ocean sea-surface temperature of ~0.5°C. This cold bias affects the distribution of time-mean convection over the tropical eastern hemisphere. Furthermore, the eastward propagation of MJO convection in this model is not as coherent as in the two models that used flux adjustment or when compared to an integration of ECHAM4 with prescribed observed SST. This result suggests that simulating a realistic basic state is at least as important as air–sea interaction for organizing the MJO. While all of the coupled models simulate the warm (cold) SST anomalies that precede (succeed) the MJO convection, the interaction of the components of the net surface heat flux that lead to these anomalies are different over the Indian Ocean. The ECHAM4/OPYC model in which the atmospheric model is run at a horizontal resolution of T42, has eastward propagating zonal wind anomalies and latent heat

  20. The Madden-Julian oscillation in ECHAM4 coupled and uncoupled general circulation models

    SciTech Connect

    Sperber, Kenneth R.; Gualdi, Silvio; Legutke, Stephanie; Gayler, Veronika

    2005-06-29

    The Madden-Julian oscillation (MJO) dominates tropical variability on timescales of 30–70 days. During the boreal winter/spring, it is manifested as an eastward propagating disturbance, with a strong convective signature over the eastern hemisphere. The space–time structure of the MJO is analyzed using simulations with the ECHAM4 atmospheric general circulation model run with observed monthly mean sea-surface temperatures (SSTs), and coupled to three different ocean models. The coherence of the eastward propagation of MJO convection is sensitive to the ocean model to which ECHAM4 is coupled. For ECHAM4/OPYC and ECHO-G, models for which ~100 years of daily data is available, Monte Carlo sampling indicates that their metrics of eastward propagation are different at the 1% significance level. The flux-adjusted coupled simulations, ECHAM4/OPYC and ECHO-G, maintain a more realistic mean-state, and have a more realistic MJO simulation than the nonadjusted scale interaction experiment (SINTEX) coupled runs. The SINTEX model exhibits a cold bias in Indian Ocean and tropical West Pacific Ocean sea-surface temperature of ~0.5°C. This cold bias affects the distribution of time-mean convection over the tropical eastern hemisphere. Furthermore, the eastward propagation of MJO convection in this model is not as coherent as in the two models that used flux adjustment or when compared to an integration of ECHAM4 with prescribed observed SST. This result suggests that simulating a realistic basic state is at least as important as air–sea interaction for organizing the MJO. While all of the coupled models simulate the warm (cold) SST anomalies that precede (succeed) the MJO convection, the interaction of the components of the net surface heat flux that lead to these anomalies are different over the Indian Ocean. The ECHAM4/OPYC model in which the atmospheric model is run at a horizontal resolution of T42, has eastward propagating zonal wind anomalies and latent heat flux

  1. Treatment of advanced solid tumours with NSAIDs: Correlation of quantitative monitoring of circulating tumour cells and positron emission tomography-computed tomography imaging

    PubMed Central

    Willecke-Hochmuth, Regina; Pachmann, Katharina; Drevs, Joachim

    2016-01-01

    The detection and characterisation of tumour-derived circulating epithelial tumor cells (CETCs) or circulating tumor cells (CTCs) have been a main focus of basic oncological research over previous years. Numerous studies in the past decade have shown that CTCs are a promising tool for the estimation of the risk for metastatic relapse. The present observational study describes treatment results using tumour imaging and the quantification of CTCs. A group of 14 patients with advanced carcinomas was followed during their anticancer treatments. CTC numbers were serially detected and treatment success was estimated by positron emission tomography-computed tomography. A connection was found between tumour remission and a decreasing CTC count in 83%, a connection between stable disease and stable CTC numbers in 78% and a connection between progressive disease (PD) and an increase in CTC count in 50% of cases. In the patients with PD, an incomplete response was observed affecting the CTCs, but not the solid region of the tumour. As a result of this study, it may be concluded that patients with solid tumours benefit from serial quantification of CTCs in addition to imaging, as this combination of techniques provides a more sensitive result than imaging alone. PMID:27588120

  2. Evaluation of Cloud Parameterizations in a High Resolution Atmospheric General Circulation Model Using ARM Data

    SciTech Connect

    Govindasamy, B; Duffy, P

    2002-04-12

    Typical state of th