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Sample records for circulation simulations applications

  1. Application of Land Surface Data Assimilation to Simulations of Sea Breeze Circulations

    NASA Technical Reports Server (NTRS)

    Mackaro, Scott; Lapenta, William M.; Blackwell, Keith; Suggs, Ron; McNider, Richard T.; Jedlovec, Gary; Kimball, Sytske

    2003-01-01

    A technique has been developed for assimilating GOES-derived skin temperature tendencies and insolation into the surface energy budget equation of a mesoscale model so that the simulated rate of temperature change closely agrees with the satellite observations. A critical assumption of the technique is that the availability of moisture (either from the soil or vegetation) is the least known term in the model's surface energy budget. Therefore, the simulated latent heat flux, which is a function of surface moisture availability, is adjusted based upon differences between the modeled and satellite- observed skin temperature tendencies. An advantage of this technique is that satellite temperature tendencies are assimilated in an energetically consistent manner that avoids energy imbalances and surface stability problems that arise from direct assimilation of surface shelter temperatures. The fact that the rate of change of the satellite skin temperature is used rather than the absolute temperature means that sensor calibration is not as critical. The sea/land breeze is a well-documented mesoscale circulation that affects many coastal areas of the world including the northern Gulf Coast of the United States. The focus of this paper is to examine how the satellite assimilation technique impacts the simulation of a sea breeze circulation observed along the Mississippi/Alabama coast in the spring of 2001. The technique is implemented within the PSUNCAR MM5 V3-5 and applied at spatial resolutions of 12- and 4-km. It is recognized that even 4-km grid spacing is too coarse to explicitly resolve the detailed, mesoscale structure of sea breezes. Nevertheless, the model can forecast certain characteristics of the observed sea breeze including a thermally direct circulation that results from differential low-level heating across the land-sea interface. Our intent is to determine the sensitivity of the circulation to the differential land surface forcing produced via the

  2. The Circulation Pattern in Simulated Contact Binaries

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Frank, J.; Tohline, J. E.

    2006-06-01

    We present a three-dimensional hydrodynamical simulation of an initially symmetric (equal mass) binary where both components are marginally in contact. The simulation evolves the binary through approximately 150 orbital periods and within the first 20 orbits, a global velocity field is established that carries material between both components. In the equatorial plane, the flow is along a figure eight pattern with streams of material sliding past one another in the neighborhood of the inner Lagrange point. For our chosen equation of state, mass transfer is ultimately unstable in this binary though the growth time is long compared to the orbital period. We are therefore able to observe that the circulation pattern, once established, is quite close to steady state. We explore the role that similar steady state flows may play in real contact systems.

  3. Application of a Coupled Multiscale Atmospheric-Land Surface Model to Simulate the Snow Circulation in a Mountain Basin

    NASA Astrophysics Data System (ADS)

    Herrera, E.; Pomeroy, J.; Pietroniro, A.

    2009-05-01

    Snow cover spatial variability and snowmelt runoff are greatly influenced by the snow advected due to the wind- flow in the atmospheric boundary layer. Typically this has been accomplished by considering the snow as a subgrid scale problem in the atmospheric models. However, this subgrid scale approach can not be sufficient to explain the snow dynamics. Therefore a multiscale strategy where the hydrological, climatological, meteorological and physiographic conditions of a basin are related should improve the understanding of snow dynamics. This methodology was developed coupling the Global Environmental Multiscale Limited Area Model (GEM-LAM) with the Cold Regions Hydrological Model (CRHM). The GEM-LAM was used on a one-way nesting configuration to simulate the atmospheric-land fields at 100m of resolution with the Interactions between Soil, Biosphere, and Atmosphere (ISBA) soil scheme. The CRHM is used as a snow transport model at the hydrometeorological stations located in the basin. The case of study is the 4th November 2007 at Marmot Creek (50° 57' N, 115° 10' W), Alberta, Canada. This strategy has proved to be a physics based procedure to describe the snow dynamics without interpolation methods.

  4. Numerical simulation of the world ocean circulation

    NASA Technical Reports Server (NTRS)

    Takano, K.; Mintz, Y.; Han, Y. J.

    1973-01-01

    A multi-level model, based on the primitive equations, is developed for simulating the temperature and velocity fields produced in the world ocean by differential heating and surface wind stress. The model ocean has constant depth, free slip at the lower boundary, and neglects momentum advection; so that there is no energy exchange between the barotropic and baroclinic components of the motion, although the former influences the latter through temperature advection. The ocean model was designed to be coupled to the UCLA atmospheric general circulation model, for the study of the dynamics of climate and climate changes. But here, the model is tested by prescribing the observed seasonally varying surface wind stress and the incident solar radiation, the surface air temperature and humidity, cloudiness and the surface wind speed, which, together with the predicted ocean surface temperature, determine the surface flux of radiant energy, sensible heat and latent heat.

  5. Anthropogenic forcing on the Hadley circulation in CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Tao, Lijun; Hu, Yongyun; Liu, Jiping

    2016-05-01

    Poleward expansion of the Hadley circulation has been an important topic in climate change studies in the past few years, and one of the critically important issues is how it is related to anthropogenic forcings. Using simulations from the coupled model intercomparison projection phase 5 (CMIP5), we study influences of anthropogenic forcings on the width and strength of the Hadley circulation. It is found that significant poleward expansion of the Hadley circulation can be reproduced in CMIP5 historical all-forcing simulations although the magnitude of trends is much weaker than observations. Simulations with individual forcings demonstrate that among three major types of anthropogenic forcings, increasing greenhouse gases (GHGs) and stratospheric ozone depletion all cause poleward expansion of the Hadley circulation, whereas anthropogenic aerosols do not have significant influences on the Hadley circulation. Increasing GHGs cause significant poleward expansion in both hemispheres, with the largest widening of the northern cell in boreal autumn. Stratospheric ozone depletion forces significant poleward expansion of the Hadley circulation for the southern cell in austral spring and summer and for the northern cell in boreal spring. In CMIP5 projection simulations for the twenty-first century, the magnitude of poleward expansion of the Hadley circulation increases with GHG forcing. On the other hand, ozone recovery competes with increasing GHGs in determining the width of the Hadley circulation, especially in austral summer. In both historical and projection simulations, the strength of the Hadley circulation shows significant weakening in winter in both hemispheres.

  6. 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

  7. Strengthening of the Walker circulation under globalwarming in an aqua-planet general circulation model simulation

    NASA Astrophysics Data System (ADS)

    Li, Tim; Zhang, Lei; Murakami, Hiroyuki

    2015-11-01

    Most climate models project a weakening of theWalker circulation under global warming scenarios. It is argued, based on a global averaged moisture budget, that this weakening can be attributed to a slower rate of rainfall increase compared to that of moisture increase, which leads to a decrease in ascending motion. Through an idealized aqua-planet simulation in which a zonal wavenumber-1 SST distribution is prescribed along the equator, we find that the Walker circulation is strengthened under a uniform 2-K SST warming, even though the global mean rainfall-moisture relationship remains the same. Further diagnosis shows that the ascending branch of the Walker cell is enhanced in the upper troposphere but weakened in the lower troposphere. As a result, a "double-cell" circulation change pattern with a clockwise (anti-clockwise) circulation anomaly in the upper (lower) troposphere forms, and the upper tropospheric circulation change dominates. The mechanism for the formation of the "double cell" circulation pattern is attributed to a larger (smaller) rate of increase of diabatic heating than static stability in the upper (lower) troposphere. The result indicates that the future change of the Walker circulation cannot simply be interpreted based on a global mean moisture budget argument.

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

    USGS Publications Warehouse

    McCabe, G.J., Jr.; 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

  9. 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.

  10. Numerical simulation of the circulation of the atmosphere of Titan

    NASA Technical Reports Server (NTRS)

    Hourdin, F.; Levan, P.; Talagrand, O.; Courtin, Regis; Gautier, Daniel; Mckay, Christopher P.

    1992-01-01

    A three dimensional General Circulation Model (GCM) of Titan's atmosphere is described. Initial results obtained with an economical two dimensional (2D) axisymmetric version of the model presented a strong superrotation in the upper stratosphere. Because of this result, a more general numerical study of superrotation was started with a somewhat different version of the GCM. It appears that for a slowly rotating planet which strongly absorbs solar radiation, circulation is dominated by global equator to pole Hadley circulation and strong superrotation. The theoretical study of this superrotation is discussed. It is also shown that 2D simulations systemically lead to instabilities which make 2D models poorly adapted to numerical simulation of Titan's (or Venus) atmosphere.

  11. Numerical simulation and prediction of coastal ocean circulation

    SciTech Connect

    Chen, P.

    1992-01-01

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

  12. Simulating effects of highway embankments on estuarine circulation

    USGS Publications Warehouse

    Lee, Jonathan K.; Schaffranek, Raymond W.; Baltzer, Robert A.

    1994-01-01

    A two-dimensional depth-averaged, finite-difference, numerical model was used to simulate tidal circulation and mass transport in the Port Royal Sound. South Carolina, estuarine system. The purpose of the study was to demonstrate the utility of the Surface-Water. Integrated. Flow and Transport model (SWIFT2D) for evaluating changes in circulation patterns and mass transport caused by highway-crossing embankments. A model of subregion of Port Royal Sound including the highway crossings and having a grid size of 61 m (200ft) was derived from a 183-m (600-ft) model of the entire Port Royal Sound estuarine system. The 183-m model was used to compute boundary-value data for the 61-m submodel, which was then used to simulate flow conditions with and without the highway embankments in place. The numerical simulations show that, with the highway embankment in place, mass transport between the Broad River and Battery Creek is reduced and mass transport between the Beaufort River and Battery Creek is increased. The net result is that mass transport into and out of upper Battery Creek is reduced. The presence of the embankments also alters circulation patterns within Battery Creek.

  13. Simulations of Tropical Circulation and Winter Precipitation Over North India: an Application of a Tropical Band Version of Regional Climate Model (RegT-Band)

    NASA Astrophysics Data System (ADS)

    Tiwari, P. R.; Kar, S. C.; Mohanty, U. C.; Dey, S.; Kumari, S.; Sinha, P.; Raju, P. V. S.; Shekhar, M. S.

    2016-02-01

    In the present study, simulations have been carried out to study the relationship between winter-time precipitations and the large-scale global forcing (ENSO) using the tropical band version of Regional Climate Model (RegT-Band) for 5 El Niño and 4 La Niña years. The RegT-Band model is integrated with the observed sea-surface temperature and lateral boundary conditions from National Center for Environmental Prediction (NCEP)-Department of Energy (DOE) reanalysis 2 (NCEP-DOE2). The model domain extends from 50°S to 50°N and covers the entire tropics at a grid spacing of 45 km, i.e., it includes lateral boundary forcing only at the southern and northern boundaries. The performance evaluation of the model in capturing the large-scale fields followed by ENSO response with winter-time precipitation has been carried out by using model simulations against NCEP-DOE2 and Global Precipitation Climatology Project (GPCP) precipitation data. The analysis suggests that the model is able to reproduce the upper airfields and large-scale precipitation during winter time, although the model has some systematic biases compared to the observations. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. It is noticed that the RegT-Band model simulations are able to bring out the observed features reasonably well. Therefore, this preliminary study indicates that the tropical band version of the regional climate model can be effectively used for the better understanding of the large-scale global forcing.

  14. Numerical Simulation of Regional Circulation in the Monterey Bay Region

    NASA Technical Reports Server (NTRS)

    Tseng, Y. H.; Dietrich, D. E.; Ferziger, J. H.

    2003-01-01

    The objective of this study is to produce a high-resolution numerical model of Mon- terey Bay area in which the dynamics are determined by the complex geometry of the coastline, steep bathymetry, and the in uence of the water masses that constitute the CCS. Our goal is to simulate the regional-scale ocean response with realistic dynamics (annual cycle), forcing, and domain. In particular, we focus on non-hydrostatic e ects (by comparing the results of hydrostatic and non-hydrostatic models) and the role of complex geometry, i.e. the bay and submarine canyon, on the nearshore circulation. To the best of our knowledge, the current study is the rst to simulate the regional circulation in the vicinity of Monterey Bay using a non-hydrostatic model. Section 2 introduces the high resolution Monterey Bay area regional model (MBARM). Section 3 provides the results and veri cation with mooring and satellite data. Section 4 compares the results of hydrostatic and non-hydrostatic models.

  15. The Agulhas circulation simulated by the global OGCM FESOM.

    NASA Astrophysics Data System (ADS)

    Sein, Dmitry; Wang, Qiang; Sidorenko, Dmitry; Harig, Sven; Durgadoo, Jonathan; Biastoch, Arne

    2015-04-01

    The Agulhas Current system, comprising of various components, is of relevance for global and regional climate on all timescales. Work undertaken in this area over the last few years have highlighted that this region is sensitive to changes of the global overturning circulation. In particular, an increase in the amount of the Indian Ocean waters entering the Atlantic has been attributed to the changes in the wind pattern in the Southern Hemisphere. Such intrusion of additional heat and salt into the Atlantic may potentially impact the stability of the meridional overturning circulation and the heat transport into the North Atlantic. We identify critical questions of both global and regional importance and aim to address them using a numerical modelling approach. The models employed are a next generation finite-element model (FESOM) developed in AWI and a state-of-the-art nested model (INALT01) developed in GEOMAR. Both models have approximately 8 km resolution in the Agulhas region. In addition the global FESOM resolution is adjusted to the sea surface height (SSH) variance obtained from the satellite observations (AVISO), i.e. the higher is the SSH variance, the higher is the FESOM resolution, varying from 6 to 100 km. The results obtained by FESOM are validated against observations, as well as against INATL01. We investigate the FESOM ability to simulate the Agulhas system, the influence of the locally eddy-permitting resolution on the general Atlantic Ocean circulation, in particular Atlantic Meridional Overturning, and the interaction of the Agulhas system with Antarctic Circumpolar Current.

  16. 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.

  17. Dynamic modeling for simulation and control of a circulating fluidized-bed combustor

    SciTech Connect

    Muir, J.R.; Brereton, C.; Grace, J.R.; Lim, C.J.

    1997-05-01

    A dynamic model has been developed to predict the transient behavior of the temperature, the heat removal rate by the in-bed heat exchanger, and the flue-gas oxygen concentration for a circulating fluidized-bed (CFB) combustor. The model was incorporated into a control simulator to reproduce the combustion process within the overall program. The simulator predicts the behavior of the combustor under manual or automatic control to allow testing of control strategies. The model is validated by comparison with step-response tests carried out on a pilot CFB combustor. Discrepancies are attributable to unmodeled disturbances. Further validation, necessary to ensure the applicability of the simulator to control development, is provided by comparing control models identified experimentally using the pilot CFB to those obtained by simulation. Favorable comparison suggests that the dynamic model is suitable for use in control simulation.

  18. 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.

  19. Modeling and simulation of circulating tumor cells in flow

    NASA Astrophysics Data System (ADS)

    Lee, Angela Meeyoun

    In this thesis, we mathematically model and computationally simulate several aspects associated with the dynamics of circulating tumor cells in the bloodstream. We focus on physical processes that initiate cancer metastasis, such as intravasation and the subsequent diffusion of thrombin by the expression of tissue factor (TF) on the surface of the circulating tumor cells that are of epithelial origin. In Part I, we develop a low-dimensional parametric deformation model of a cancer cell under shear flow. The surface deformation of MDA-MB-213 cells is imaged using DIC microscopy imaging techniques until the cell releases into the flow. We post-process the time sequence of images using an Active Shape Model (ASM) to obtain the principal components of deformation, which are then used as parameters in an empirical constitutive equation to model the cell deformations as a function of the fluid normal and shear forces imparted. The cell surface is modeled as a 2D Gaussian interface with three active parameters: height, x-width, and y-width. Fluid forces are calculated on the cell surface by discretizing the surface with regularized Stokeslets, and the flow is driven by a stochastically fluctuating pressure gradient. The Stokeslet strengths are obtained so that viscous boundary conditions are enforced on the surface of the cell and the surrounding plate. We show that the low-dimensional model is able to capture the principal deformations of the cell reasonably well and argue that Active Shape Models can be exploited further as a useful tool to bridge the gap between experiments, models, and numerical simulations in this biological setting. In Part II, we describe a mathematical and computational model for diffusion-limited procoagulant circulating tumor cells (CTCs) in flow. We first build a model based on an exact formulation of Green's function solutions for domains with a blood vessel wall and for closed domains. Time-dependent gradient trackers are used to highlight

  20. Self-biased circulators for high power applications

    NASA Astrophysics Data System (ADS)

    Sokolov, Alexander S.

    Self-biased circulators exploit the properties of high anisotropy magnetic field in hexagonal ferrites, thus allowing operation without biasing magnets and a significant size and weight reduction. Although first self-biased circulators were demonstrated more than 20 years ago, all the prototypes constructed so far are unsuitable for practical applications. An attempt to design a self-biased circulator from scratch was made. Novel exceptionally low dielectric loss and high heat conductivity ceramic materials were developed and innovative substrate synthesis techniques were employed. Low temperature cofiring of green body ferrite compacts and dielectric ceramic slurries were mastered, resulting in solid composite substrates. Original device design was developed. Key features (including wide coupling angles, wide microstriplines, thick substrate, and absence of impedance transformers) enable low insertion loss, broadband operation, high power handling, and compact size. Fabrication and testing of Ka band Y-junction self-biased circulator are reported herein. Furthermore, design approach and fabrication techniques developed here can be readily applied for the construction of X-band self-biased circulators, provided that suitable ferrite materials are available. Low temperature cofiring of ferrite and dielectric materials is especially beneficial for various RF and high-frequency applications. Multiple devices can be readily fabricated on a single wafer using conventional lithographic techniques, resulting in true microwave monolithic integrated circuit.

  1. VCSEL Applications and Simulation

    NASA Technical Reports Server (NTRS)

    Cheung, Samson; Goorjian, Peter; Ning, Cun-Zheng; Li, Jian-Zhong

    2000-01-01

    This viewgraph presentation gives an overview of Vertical Cavity Surface Emitting Laser (VCSEL) simulation and its applications. Details are given on the optical interconnection in information technology of VCSEL, the formulation of the simulation, its numeric algorithm, and the computational results.

  2. 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

  3. An interactive computer simulator of the circulation for knowledge acquisition in cardio-anesthesia.

    PubMed

    Popp, H J; Schecke, T; Rau, G; Käsmacher, H; Kalff, G

    1991-01-01

    Knowledge-based decision support systems for use in cardio-anesthesia can provide online support to the anesthesiologist by generating intelligent alarms. However, the acquisition and validation of a consistent knowledge base for this application bears problems related to the transfer of clinical experiences into a rule system. An interactive simulator of the human circulation is presented that supports the process of knowledge acquisition and testing. The simulator can be controlled in realtime by an anesthesiologist during the simulation run thus providing a basis for interdisciplinary discussion of routine as well as critical situations. The output data can be transferred to a knowledge-based system for test purposes. The simulator is currently being used for the development of the Anesthesia Expert Assist System AES-2. With regard to the special application a model of the heart-function was integrated which enables the simulation of heart insufficiency. Simulation runs under various conditions are presented and discussed. The simulator was implemented on an ATARI ST personal computer. PMID:1779177

  4. 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

  5. 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.

  6. Aspects of Numerical Simulation of Circulation Control Airfoils

    NASA Technical Reports Server (NTRS)

    Swanson, R. C.; Rumsey, C. L.; Anders, S. G.

    2005-01-01

    The mass-averaged compressible Navier-Stokes equations are solved for circulation control airfoils. Numerical solutions are computed with a multigrid method that uses an implicit approximate factorization smoother. The effects of flow conditions (e.g., free-stream Mach number, angle of attack, momentum coefficient) and mesh on the prediction of circulation control airfoil flows are considered. In addition, the impact of turbulence modeling, including curvature effects and modifications to reduce eddy viscosity levels in the wall jet (i.e., Coanda flow), is discussed. Computed pressure distributions are compared with available experimental data.

  7. Simulating the three-dimensional circulation and hydrography of Halifax Harbour using a multi-nested coastal ocean circulation model

    NASA Astrophysics Data System (ADS)

    Shan, Shiliang; Sheng, Jinyu; Thompson, Keith Richard; Greenberg, David Alexander

    2011-07-01

    Halifax Harbour is located on the Atlantic coast of Nova Scotia, Canada. It is one of the world's largest, ice-free natural harbours and of great economic importance to the region. A good understanding of the physical processes controlling tides, flooding, transport and dispersion, and hydrographic variability is required for pollution control and sustainable development of the Harbour. For the first time, a multi-nested, finite difference coastal ocean circulation model is used to reconstruct the three-dimensional circulation and hydrography of the Harbour and its variability on timescales of hours to months for 2006. The model is driven by tides, wind and sea level pressure, air-sea fluxes of heat, and terrestrial buoyancy fluxes associated with river and sewage discharge. The predictive skill of the model is assessed by comparing the model simulations with independent observations of sea level from coastal tide gauges and currents from moored instruments. The simulated hydrography is also compared against a new monthly climatology created from all available temperature and salinity observations made in the Harbour over the last century. It is shown that the model can reproduce accurately the main features of the observed tides and storm surge, seasonal mean circulation and hydrography, and wind driven variations. The model is next used to examine the main physical processes controlling the circulation and hydrography of the Harbour. It is shown that non-linear interaction between tidal currents and complex topography occurs over the Narrows. The overall circulation can be characterized as a two-layer estuarine circulation with seaward flow in the thin upper layer and landward flow in the broad lower layer. An important component of this estuarine circulation is a relatively strong, vertically sheared jet situated over a narrow sill connecting the inner Harbour to the deep and relatively quiescent Bedford Basin. Local wind driven variability is strongest in

  8. Circulation simulator method for evaluating bank note and optical feature durability

    NASA Astrophysics Data System (ADS)

    Bartz, William J.; Crane, Timothy T.

    2006-02-01

    Effective long-term authentication of optical security features on bank notes requires a sound substrate that can withstand the rigors of circulation. Crane & Co. has developed a test method that simulates the deterioration observed in actual circulated bank notes: soiling, creasing, tearing, edge tatteredness and limpness. The method relies on the physical degradation of note specimens that are weighted on each corner and tumbled in a medium of glass beads, metal discs and synthetic soil. Durability is judged by how well a note retains its initial optical and physical properties after being subjected to the conditions of the Circulation Simulator. Much of our early research was directed at improving the paper substrate, and evaluating surface treatments that resist soiling since excessive soiling is often the primary reason bank notes are removed from circulation. Recent work has examined the correlation between Circulation Simulator results and the properties of actual bank notes culled from circulation. We also are using the Circulation Simulator method to qualitatively evaluate the potential durability and effectiveness of optical security features such as electrotypes, watermarks, windowed threads, foils and inks. This paper provides a description of the testing and analysis methods.

  9. Simulating the impact of the large-scale circulation on the 2-m temperature and precipitation climatology

    NASA Astrophysics Data System (ADS)

    Bowden, Jared H.; Nolte, Christopher G.; Otte, Tanya L.

    2013-04-01

    The impact of the simulated large-scale atmospheric circulation on the regional climate is examined using the Weather Research and Forecasting (WRF) model as a regional climate model. The purpose is to understand the potential need for interior grid nudging for dynamical downscaling of global climate model (GCM) output for air quality applications under a changing climate. In this study we downscale the NCEP-Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis using three continuous 20-year WRF simulations: one simulation without interior grid nudging and two using different interior grid nudging methods. The biases in 2-m temperature and precipitation for the simulation without interior grid nudging are unreasonably large with respect to the North American Regional Reanalysis (NARR) over the eastern half of the contiguous United States (CONUS) during the summer when air quality concerns are most relevant. This study examines how these differences arise from errors in predicting the large-scale atmospheric circulation. It is demonstrated that the Bermuda high, which strongly influences the regional climate for much of the eastern half of the CONUS during the summer, is poorly simulated without interior grid nudging. In particular, two summers when the Bermuda high was west (1993) and east (2003) of its climatological position are chosen to illustrate problems in the large-scale atmospheric circulation anomalies. For both summers, WRF without interior grid nudging fails to simulate the placement of the upper-level anticyclonic (1993) and cyclonic (2003) circulation anomalies. The displacement of the large-scale circulation impacts the lower atmosphere moisture transport and precipitable water, affecting the convective environment and precipitation. Using interior grid nudging improves the large-scale circulation aloft and moisture transport/precipitable water anomalies, thereby improving the simulated 2-m temperature and precipitation

  10. Role of a cumulus parameterization scheme in simulating atmospheric circulation and rainfall in the nine-layer Goddard Laboratory for Atmospheres General Circulation Model

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Chao, Winston C.; Walker, G. K.

    1992-01-01

    The influence of a cumulus convection scheme on the simulated atmospheric circulation and hydrologic cycle is investigated by means of a coarse version of the GCM. Two sets of integrations, each containing an ensemble of three summer simulations, were produced. The ensemble sets of control and experiment simulations are compared and differentially analyzed to determine the influence of a cumulus convection scheme on the simulated circulation and hydrologic cycle. The results show that cumulus parameterization has a very significant influence on the simulation circulation and precipitation. The upper-level condensation heating over the ITCZ is much smaller for the experiment simulations as compared to the control simulations; correspondingly, the Hadley and Walker cells for the control simulations are also weaker and are accompanied by a weaker Ferrel cell in the Southern Hemisphere. Overall, the difference fields show that experiment simulations (without cumulus convection) produce a cooler and less energetic atmosphere.

  11. Seasonal changes in the atmospheric heat balance simulated by the GISS general circulation model

    NASA Technical Reports Server (NTRS)

    Stone, P. H.; Chow, S.; Helfand, H. M.; Quirk, W. J.; Somerville, R. C. J.

    1975-01-01

    Tests of the ability of numerical general circulation models to simulate the atmosphere have focussed so far on simulations of the January climatology. These models generally present boundary conditions such as sea surface temperature, but this does not prevent testing their ability to simulate seasonal changes in atmospheric processes that accompany presented seasonal changes in boundary conditions. Experiments to simulate changes in the zonally averaged heat balance are discussed since many simplified models of climatic processes are based solely on this balance.

  12. Postural reactions of circulation and its regulation during simulated weightlessness

    NASA Astrophysics Data System (ADS)

    Sokolov, V. I.; Valyev, V. A.; Kirillov, M. V.; Gornago, V. A.

    The extention and intensification of space exploration the influence of weightlessness on human organism and the formation of a new level of adaptation. The studies of blood circulation is very important because of freguent occurance of cardiovascular disorders in the middle age sudjects. In connection with extention and intensification of space exploration the influence of weightlessness on human organism and the formation of a new level of adaptation mechanisms acguires a special significance (5, 9, 10). The data obtained in recently undertaken model experiments (1, 5, 10), and also during space flights (5, 9) indicate that weightlessness in many ways affects various physiological systems of organism, and first of all cardiovascular system with the development of reflex, humoral and metabolic reactions. It also indicates, that the changes in functioning of cardiovascular system brings about the discruption of its regular responses, which is foremost expressed in decreased antigravitational response, which manifests itself in lowered orthostatic stability (2, 4, 6). It is worth mentioning, that the changes during previous investigations of haemodynamics were mainly carried out with the subjects under forty, therefore agerelated specific features of blood circulation system response are described in a few articles (5, 8). The studies of the kind are especially important because of frequent occurence of cardiovascular disorders such as heart and brain vessels atherosclerosis, hypertension in the middle age, which can to a great extent complicate and affect the "acute" period of adaptation to weightlessness and readaptation process.

  13. Numerical simulation of losses along a natural circulation helium loop

    NASA Astrophysics Data System (ADS)

    Knížat, Branislav; Urban, František; Mlkvik, Marek; RidzoÅ, František; Olšiak, Róbert

    2016-06-01

    A natural circulation helium loop appears to be a perspective passive method of a nuclear reactor cooling. When designing this device, it is important to analyze the mechanism of an internal flow. The flow of helium in the loop is set in motion due to a difference of hydrostatic pressures between cold and hot branch. Steady flow at a requested flow rate occurs when the buoyancy force is adjusted to resistances against the flow. Considering the fact that the buoyancy force is proportional to a difference of temperatures in both branches, it is important to estimate the losses correctly in the process of design. The paper deals with the calculation of losses in branches of the natural circulation helium loop by methods of CFD. The results of calculations are an important basis for the hydraulic design of both exchangers (heater and cooler). The analysis was carried out for the existing model of a helium loop of the height 10 m and nominal heat power 250 kW.

  14. Application of thermospheric general circulation models for space weather operations

    NASA Astrophysics Data System (ADS)

    Fuller-Rowell, T.; Minter, C.; Codrescu, M.

    Solar irradiance is the dominant source of heat, ionization, and dissociation of the thermosphere, and to a large extent drives the global dynamics, and controls the neutral composition and density structure. Neutral composition is important for space weather applications because of its impact on ionospheric loss rates, and neutral density is critical for satellite drag prediction. The future for thermospheric general circulation models for space weather operations lies in their use as state propagators in data assimilation techniques. The physical models can match empirical models in accuracy provided accurate drivers are available, but their true value comes when combined with data in an optimal way. Two such applications have recently been developed. The first utilizes a Kalman filter to combine space-based observation of airglow with physical model predictions to produce global maps of neutral composition. The output of the filter will be used within the GAIM (Global Assimilation of Ionospheric Measurement) model developed under a parallel effort. The second filter uses satellite tracking and remote sensing data for specification of neutral density. Both applications rely on accurate estimates of the solar EUV and magnetospheric drivers.

  15. Design and Application of Novel Horizontal Circulating Fluidized Bed Boiler

    NASA Astrophysics Data System (ADS)

    Lit, Q. H.; Zhang, Y. G.; Meng, A. H.

    The vertical circulating fluidized bed (CFB) boiler has been found wide application in power generation and tends to be enlarged in capacity. Because CFB is one of environment friendly and high efficiency combustion technologies, the CFB boiler has also been expected to be used in the industrial area, such as textile mill, region heating, brewery, seed drying and so on. However, the necessary height of furnace is hard to be implemented for CFB with especially small capacity. Thereby, a novel horizontal circulating fluidized bed boiler has been proposed and developed. The horizontal CFB is composed of primary combustion chamber, secondary combustion chamber, burnout chamber, cyclone, loop seal, heat recovery area. The primary combustion chamber is a riser like as that in vertical CFB, and the secondary combustion chamber is a downward passage that is a natural extension of the primary riser, which can reduce the overall height of the boiler. In some extent, the burnout chamber is also the extension of primary riser. The capacity of horizontal CFB is about 4.2-24.5MWth (6-35t/h) steam output or equivalent hot water supply. The hot water boiler of 7MWth and steam boilers of 4.2MWth (6t/h) and 10.5MWth (15t/h) are all designed and working well now. The three units of hot water horizontal CFB boiler were erected in the Neimenggu Autonomous Region, Huhehaote city for region heating. The three units of steam horizontal CFB has been installed in Yunnan, Jiang Xi and Guangdong provinces, respectively. The basic principle for horizontal CFB and experiences for designing and operating are presented in this paper. Some discussions are also given to demonstrate the promising future of horizontal CFB.

  16. Simulation and optimization of airlift external circulation membrane bioreactor using computational fluid dynamics.

    PubMed

    Qing, Zhang; Rongle, Xu; Xiang, Zheng; Yaobo, Fan

    2014-01-01

    The airlift external circulation membrane bioreactor (AEC-MBR) is a new MBR consisting of a separated aeration tank and membrane tank with circulating pipes fixed between the two tanks. The circulating pipe is called a H circulating pipe (HCP) because of its shape. With the complex configuration, it was difficult but necessary to master the AEC-MBR's hydraulic characteristics. In this paper, simulation and optimization of the AEC-MBR was performed using computational fluid dynamics. The distance from diffusers to membrane modules, i.e. the height of gas-liquid mixing zone (h(m)), and its effect on velocity distribution at membrane surfaces were studied. Additionally, the role of HCP and the effect of HCP's diameter on circulation were simulated and analyzed. The results showed that non-uniformity of cross-flow velocity existed in the flat-plate membrane modules, and the problem could be alleviated by increasing hm to an optimum range (h(m)/B ≥ 0.55; B is total static depth). Also, the low velocity in the boundary layer on the membrane surface was another reason for membrane fouling. The results also suggested that HCP was necessary and it had an optimum diameter to make circulation effective in the AEC-MBR. PMID:24804658

  17. Large eddy simulation using the general circulation model ICON

    NASA Astrophysics Data System (ADS)

    Dipankar, Anurag; Stevens, Bjorn; Heinze, Rieke; Moseley, Christopher; Zängl, Günther; Giorgetta, Marco; Brdar, Slavko

    2015-09-01

    ICON (ICOsahedral Nonhydrostatic) is a unified modeling system for global numerical weather prediction (NWP) and climate studies. Validation of its dynamical core against a test suite for numerical weather forecasting has been recently published by Zängl et al. (2014). In the present work, an extension of ICON is presented that enables it to perform as a large eddy simulation (LES) model. The details of the implementation of the LES turbulence scheme in ICON are explained and test cases are performed to validate it against two standard LES models. Despite the limitations that ICON inherits from being a unified modeling system, it performs well in capturing the mean flow characteristics and the turbulent statistics of two simulated flow configurations—one being a dry convective boundary layer and the other a cumulus-topped planetary boundary layer.

  18. Numerical Simulations of a Circulating Fluidized Bed with a Square Cross-Section

    SciTech Connect

    Li, Tingwen

    2011-01-01

    In this study, both 2D and 3D numerical simulations of a well-documented circulating fluidized bed with a square cross-section were conducted. With some assumptions, a series of 2D simulations was first carried out to study the influence of grid resolution, initial flow field, and boundary condition on the flow hydrodynamics. It was found that 2D simulations under-predicted the solids inventory even with the finest grid (10-particle-diameter grid size). On the other hand, a 3D simulation with relatively coarse grid was found in better agreement with the experimental data. Differences between 2D and 3D simulations were briefly discussed.

  19. Evaluating Parameterizations in General Circulation Models: Climate Simulation Meets Weather Prediction

    SciTech Connect

    Phillips, T J; Potter, G L; Williamson, D L; Cederwall, R T; Boyle, J S; Fiorino, M; Hnilo, J J; Olson, J G; Xie, S; Yio, J J

    2004-05-06

    To significantly improve the simulation of climate by general circulation models (GCMs), systematic errors in representations of relevant processes must first be identified, and then reduced. This endeavor demands that the GCM parameterizations of unresolved processes, in particular, should be tested over a wide range of time scales, not just in climate simulations. Thus, a numerical weather prediction (NWP) methodology for evaluating model parameterizations and gaining insights into their behavior may prove useful, provided that suitable adaptations are made for implementation in climate GCMs. This method entails the generation of short-range weather forecasts by a realistically initialized climate GCM, and the application of six-hourly NWP analyses and observations of parameterized variables to evaluate these forecasts. The behavior of the parameterizations in such a weather-forecasting framework can provide insights on how these schemes might be improved, and modified parameterizations then can be tested in the same framework. In order to further this method for evaluating and analyzing parameterizations in climate GCMs, the U.S. Department of Energy is funding a joint venture of its Climate Change Prediction Program (CCPP) and Atmospheric Radiation Measurement (ARM) Program: the CCPP-ARM Parameterization Testbed (CAPT). This article elaborates the scientific rationale for CAPT, discusses technical aspects of its methodology, and presents examples of its implementation in a representative climate GCM.

  20. Simulation of the Atlantic meridional overturning circulation at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Oka, A.; Hasumi, H.; Abe-Ouchi, A.

    2008-12-01

    The ocean circulation in the Atlantic deep ocean is characterized by thermohaline circulation driven by deep convection in northern high latitudes. The heat transport associated with this circulation is comparable to that by atmosphere and has a great role in the present climate. The Atlantic meridional overturning circulation (AMOC) is believed to change in past and future climate changes. Coupled model simulations suggest that the AMOC becomes weak in the future global warming climate. Geological evidence such as carbon isotope ratio indicates that the AMOC was weaker and shallower than the present at the Last Glacial Maximum (LGM). As for global warming climate, almost all model results reach consensus that the Atlantic deep circulation weakens in global warming climate. On the other hand, there is wide discrepancy in simulation of the Atlantic deep circulation at the LGM. Weber et al. (2007) report results of Paleoclimate Modeling Intercomparison Project where half of models reproduce the weakening of the Atlantic deep circulation but the other half simulates the strengthening. The reason for this disagreement between models has not been clarified yet, and investigation on the mechanism of weakening of the Atlantic deep circulation at the LGM is one of the most important topics in the paleoclimate studies. In this study, by using results of a coupled climate model (MIROC), we focus on role of changes in the sea surface heat and freshwater fluxes and investigate their role in controlling the AMOC at the LGM. In order to individually evaluate role of heat and freshwater fluxes, we conduct additional ocean general circulation model simulations under the sea surface heat/freshwater flux conditions obtained from the present and LGM simulations by MIROC. The results suggest that the freshwater flux changes contribute to weakening of the AMOC at the LGM, whereas the heat flux changes make the AMOC at the LGM stronger than the present. In the presentation, we are

  1. Simulation of West African monsoon circulation in four atmospheric general circulation models forced by prescribed sea surface temperature

    NASA Astrophysics Data System (ADS)

    Moron, Vincent; Philippon, Nathalie; Fontaine, Bernard

    2004-12-01

    The mean evolution of the West African monsoon (WAM) circulation and its interannual variability have been studied using an ensemble of 21 simulations (common period 1961-1994) performed with four different atmospheric general circulation models (AGCMs) (European Center/Hamburg (ECHAM) 3, ECHAM 4, Action de Recherche Petite Echelle Grande Echelle (ARPEGE), and Goddard Institute for Space Studies (GISS)) and forced by the same observed sea surface temperature (SST) data set. The results have been compared with European Centre for Medium-Range Weather Forecasts reanalyses (ERA-40). The climatological means of WAM winds for the AGCMs are similar to the ERA-40 ones. However, the AGCMs tend to underestimate the southern wind component at low levels around 10°N compared to the ERA-40. The simulated Tropical Easterly Jet (TEJ) is usually shifted northward and also too weak for ECHAM 3 and ECHAM 4 compared to ERA-40. The interannual variability of an atmospheric WAM index (WAMI) is quite successfully reproduced (the correlations between the mean ensemble of each AGCM and ERA-40 time series over 1961-1994 range between 0.51 and 0.64). In particular, the four AGCMs reproduce quite well the mean teleconnection structure with El Niño-Southern Oscillation, i.e., a strong (weak) monsoon during La Niña (El Niño) events, even if the largest absolute correlations between WAMI and SST in the eastern and central equatorial Pacific are weaker than in ERA-40. On a yearly basis, WAMI is more predictable and skillful during the cold ENSO years than during the warm ENSO ones. The unskillful warm ENSO events are associated with a significant cooling over the equatorial Atlantic and Western Pacific Ocean and a significant warming in the tropical Indian Ocean.

  2. Numerical simulation of Black Sea circulation and pollution propagation in coastal waters of the Great Sochi

    NASA Astrophysics Data System (ADS)

    Fomin, Vladimir; Gusev, Anatoly; Diansky, Nikolay

    2014-05-01

    The numerical modelling of the Black Sea (BS) is performed by using INMOM (Institute of Numerical Mathematics Ocean Model). The model is based on the primitive equations in spherical s-coordinate system with free surface boundary condition. The numerical algorithm is based on the method of multicomponent splitting and has a flexible modular structure. The splitting with respect to physical processes and spatial coordinate is used. A computational method is proposed of the polluting substances (PS) transport in the BS region adjacent to the Great Sochi. It is based on INMOM application for the BS in two versions: M1 and M2. In the M1 INMOM has a uniform spatial resolution ~4 km, while M2 has non-uniform one with refinement to 50 m in the BS region near Great Sochi coast. The M2 is used only during the periods of PS transport computation for which the initial hydrothermodynamic conditions are taken from M1. Both versions reveal complexity of the BS circulation nature, however, M2 more adequately reproduces eddy circulation due to higher horizontal resolution in its eastern part. Hence, a suggestion is made that BS eddy structure simulation requires model resolution ~1.5 km, and the major factor of quasistationary Batumi anti-cyclonic gyre formation is the topographical features in this part of the sea. A computation of PS distribution from the rivers Sochi, Host and Mzymta and from 18 pipes of deep-water sewage production was performed for the high-water period from 01.04.2007 to 30.04.2007. It is shown that the significant contribution to PS distribution from these punctual sources is made by whirlwind mesoscale formations generating complicated 3-dimensional PS distribution.

  3. Ensemble simulations of the magnetic field induced by global ocean circulation: Estimating the uncertainty

    NASA Astrophysics Data System (ADS)

    Irrgang, Christopher; Saynisch, Jan; Thomas, Maik

    2016-03-01

    The modeling of the ocean global circulation induced magnetic field is affected by various uncertainties that originate from errors in the input data and from the model itself. The amount of aggregated uncertainties and their effect on the modeling of electromagnetic induction in the ocean is unknown. For many applications, however, the knowledge of uncertainties in the modeling is essential. To investigate the uncertainty in the modeling of motional induction at the sea surface, simulation experiments are performed on the basis of different error scenarios and error covariance matrices. For these error scenarios, ensembles of an ocean general circulation model and an electromagnetic induction model are generated. This ensemble-based approach allows to estimate both the spatial distribution and temporal variation of the uncertainty in the ocean-induced magnetic field. The largest uncertainty in the ocean-induced magnetic field occurs in the area of the Antarctic Circumpolar Current. Local maxima reach values of up to 0.7 nT. The estimated global annual mean uncertainty in the ocean-induced magnetic field ranges from 0.1 to 0.4 nT. The relative amount of uncertainty reaches up to 30% of the signal strength with largest values in regions in the northern hemisphere. The major source of uncertainty is found to be introduced by wind stress from the atmospheric forcing of the ocean model. In addition, the temporal evolution of the uncertainty in the induced magnetic field shows distinct seasonal variations. Specific regions are identified which are robust with respect to the introduced uncertainties.

  4. A simulation of the winter and summer circulations with the NMC Global Spectral Model

    NASA Technical Reports Server (NTRS)

    Kinter, J. L., III; Shukla, J.; Marx, L.; Schneider, E. K.

    1988-01-01

    The medium range forecast model of the NMC has been integrated to produce winter and summer simulations. It is found that the model climatology is similar to that of the observed atmosphere as well as climatologies of other general circulation models. The stationary and transient features of the model circulation are described, including both tropical and extratropical regions. The model hydrological cycle, radiative balance, and surface heat budget are discussed. Comparison with observations shows that the model is colder than that observed in the troposphere and cools in the lower stratosphere in the tropics and near the poles in both simulations. It is suggested that the upper branch of the Hadley cell is poorly simulated in the integrated model. The simulations are in reasonable agreement with the observations in sea level pressure, the structure of the tropospheric zonal jets, and the winter hemispheric stationary waves.

  5. 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.

  6. MERIDIONAL CIRCULATION DYNAMICS FROM 3D MAGNETOHYDRODYNAMIC GLOBAL SIMULATIONS OF SOLAR CONVECTION

    SciTech Connect

    Passos, Dário; Charbonneau, Paul; Miesch, Mark

    2015-02-10

    The form of solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone at mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 R{sub ⊙}). We also provide physical arguments to justify this behavior. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.

  7. Variable-resolution frameworks for the simulation of tropical cyclones in global atmospheric general circulation models

    NASA Astrophysics Data System (ADS)

    Zarzycki, Colin

    The ability of atmospheric General Circulation Models (GCMs) to resolve tropical cyclones in the climate system has traditionally been difficult. The challenges include adequately capturing storms which are small in size relative to model grids and the fact that key thermodynamic processes require a significant level of parameterization. At traditional GCM grid spacings of 50-300 km tropical cyclones are severely under-resolved, if not completely unresolved. This thesis explores a variable-resolution global model approach that allows for high spatial resolutions in areas of interest, such as low-latitude ocean basins where tropical cyclogenesis occurs. Such GCM designs with multi-resolution meshes serve to bridge the gap between globally-uniform grids and limited area models and have the potential to become a future tool for regional climate assessments. A statically-nested, variable-resolution option has recently been introduced into the Department of Energy/National Center for Atmospheric Research (DoE/NCAR) Community Atmosphere Model's (CAM) Spectral Element (SE) dynamical core. Using an idealized tropical cyclone test, variable-resolution meshes are shown to significantly lessen computational requirements in regional GCM studies. Furthermore, the tropical cyclone simulations are free of spurious numerical errors at the resolution interfaces. Utilizing aquaplanet simulations as an intermediate test between idealized simulations and fully-coupled climate model runs, climate statistics within refined patches are shown to be well-matched to globally-uniform simulations of the same grid spacing. Facets of the CAM version 4 (CAM4) subgrid physical parameterizations are likely too scale sensitive for variable-resolution applications, but the newer CAM5 package is vastly improved in performance at multiple grid spacings. Multi-decadal simulations following 'Atmospheric Model Intercomparison Project' protocols have been conducted with variable-resolution grids. Climate

  8. 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.

  9. Modeling and simulation of liquid-solid circulating fluidized bed ion exchange system for continuous protein recovery.

    PubMed

    Mazumder, Jahirul; Zhu, Jingxu; Bassi, Amarjeet S; Ray, Ajay K

    2009-09-01

    Liquid-solid circulating fluidized bed (LSCFB) is an integrated two-column (downcomer and riser) system which can accommodate two separate processes (adsorption and desorption) in the same unit with continuous circulation of the solid particles between the two columns. In this study, a mathematical model based on the assumption of homogeneous fluidization was developed considering hydrodynamics, adsorption-desorption kinetics and liquid-solid mass transfer. The simulation results showed good agreement with the available experimental results for continuous protein recovery. A parametric sensitivity study was performed to better understand the influence of different operating parameters on the BSA adsorption and desorption capacity of the system. The model developed can easily be extended to other applications of LSCFB. PMID:19466748

  10. Numerical simulation of the general circulation of the atmosphere of Titan.

    PubMed

    Hourdin, F; Talagrand, O; Sadourny, R; Courtin, R; Gautier, D; McKay, C P

    1995-10-01

    The atmospheric circulation of Titan is investigated with a general circulation model. The representation of the large-scale dynamics is based on a grid point model developed and used at Laboratoire de Météorologie Dynamique for climate studies. The code also includes an accurate representation of radiative heating and cooling by molecular gases and haze as well as a parametrization of the vertical turbulent mixing of momentum and potential temperature. Long-term simulations of the atmospheric circulation are presented. Starting from a state of rest, the model spontaneously produces a strong superrotation with prograde equatorial winds (i.e., in the same sense as the assumed rotation of the solid body) increasing from the surface to reach 100 m sec-1 near the 1-mbar pressure level. Those equatorial winds are in very good agreement with some indirect observations, especially those of the 1989 occultation of Star 28-Sgr by Titan. On the other hand, the model simulates latitudinal temperature contrasts in the stratosphere that are significantly weaker than those observed by Voyager 1 which, we suggest, may be partly due to the nonrepresentation of the spatial and temporal variations of the abundances of molecular species and haze. We present diagnostics of the simulated atmospheric circulation underlying the importance of the seasonal cycle and a tentative explanation for the creation and maintenance of the atmospheric superrotation based on a careful angular momentum budget. PMID:11538593

  11. Large-Eddy Simulation of Mesoscale Circulations Forced by Inhomogeneous Urban Heat Island

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Wang, Xueyuan; Peng, Zhen

    2014-04-01

    The large-eddy simulation mode of the Weather Research and Forecasting model is employed to simulate the planetary boundary-layer characteristics and mesoscale circulations forced by an ideal urban heat island (UHI). In our simulations, the horizontal heterogeneity of the UHI intensity distribution in urban areas is considered and idealized as a cosine function. Results indicate that the UHI heating rate and the UHI intensity heterogeneity affect directly the spatial distribution of the wind field; a stronger UHI intensity produces a maximum horizontal wind speed closer to the urban centre. The strong advection of warm air from the urban area to the rural area in the upper part of the planetary boundary-layer causes a more stable atmospheric stratification over both the urban and rural areas. The mesoscale sensible heat flux caused by the UHI circulation increases with UHI intensity but vanishes when the background wind speed is sufficiently high 3.0.

  12. Numerical Study on an Autonomous Decentralized Model-Based Simulation of Resources Circulation Systems

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takuya; Tamaki, Hisashi; Murao, Hajime; Kitamura, Shinzo

    In this paper, a methodology for modeling and controlling of resources circulation systems is studied. We propose a model structure by introducing two kinds of sub-models: a physical model and an information model. The physical model is used for simulating the flow of materials, products and also money, while the information model is used for representing flow of information and decision-making on production, consumption, recycling/reuse, discard, etc. Moreover, we introduce an additional top-level component, a supervisor, who observes the global behavior of the system and controls it indirectly. Based on the proposed approach, we implement a prototype of simulation model including producers, consumers and recyclers. Through some computer simulations based on the model, it is shown that the model has price adjustment function and its global behavior is very complicated. Then, we examine influences of the informational as well as the physical indirect control on the resources circulation.

  13. 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.

  14. Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed

    NASA Astrophysics Data System (ADS)

    Zhu, Jianguo; Ouyang, Ziqu; Lu, Qinggang

    2013-06-01

    High temperature air combustion is a prospecting technology in energy saving and pollutants reduction. Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed was presented. The down-fired combustor, taken as the calculation domain, has the diameter of 220 mm and the height of 3000 mm. 2 cases with air staging combustion are simulated. Compared the simulation results with experimental data, there is a good agreement. It is found that the combustion model and NOx formation model are applicable to simulate the pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed. The results show that there is a uniform temperature profile along the axis of the down-fired combustor. The NOx emissions are lower than those of ordinary pulverized coal combustion, and the NOx emissions are 390 mg/m3 and 352 mg/m3 in Case 1 and Case 2, respectively. At the range of 300-600 mm below the nozzle, the NO concentration decreases, mainly resulting from some homogeneous reactions and heterogeneous reaction. NO concentration has a little increase at the position of 800 mm below the nozzle as the tertiary air supplied to the combustor at the position of 600 mm below the nozzle.

  15. Reproduction of links between circulation types and precipitation in Central Europe in regional climate model simulations

    NASA Astrophysics Data System (ADS)

    Plavcová, Eva; Kyselý, Jan; Štěpánek, Petr

    2014-05-01

    The study evaluates relationships between large-scale atmospheric circulation (represented by circulation indices and circulation types derived from gridded mean sea level pressure) and daily precipitation amounts over three regions in the Czech Republic (Central Europe) with different precipitation regimes. We examine how ENSEMBLES regional climate model (RCM) simulations driven by re-analysis reproduce the observed links and capture differences in the links between the regions (lowlands vs. highlands) and seasons. We study the links of circulation to (i) mean precipitation over the regions, (ii) probability of wet days, and (iii) probability of extreme daily precipitation (exceeding threshold defined by a high quantile of precipitation distribution in a given season). Relatively strong links between atmospheric circulation and the precipitation characteristics are found in the observed data. The links are generally more pronounced for highland than lowland regions. More wet days and higher precipitation amounts are found for cyclonic and stronger flows, and for westerly and north-easterly flows. The RCMs are generally able to capture basic features of the links; nevertheless, they have difficulties to reproduce some more specific features and differences in the links between the regions. The results also suggest that good performance in some precipitation characteristics may be due to compensating errors rather than model's perfection. Reference: Plavcová E., Kyselý J., Štěpánek P., 2014: Links between circulation types and precipitation in Central Europe in the observed data and regional climate model simulations. International Journal of Climatology, doi 10.1002/joc.3882.

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

    USGS Publications Warehouse

    McCabe, G.J., Jr.; 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

  17. Simulation of seasonal anomalies of atmospheric circulation using coupled atmosphere-ocean model

    NASA Astrophysics Data System (ADS)

    Tolstykh, M. A.; Diansky, N. A.; Gusev, A. V.; Kiktev, D. B.

    2014-03-01

    A coupled atmosphere-ocean model intended for the simulation of coupled circulation at time scales up to a season is developed. The semi-Lagrangian atmospheric general circulation model of the Hydrometeorological Centre of Russia, SLAV, is coupled with the sigma model of ocean general circulation developed at the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), INMOM. Using this coupled model, numerical experiments on ensemble modeling of the atmosphere and ocean circulation for up to 4 months are carried out using real initial data for all seasons of an annual cycle in 1989-2010. Results of these experiments are compared to the results of the SLAV model with the simple evolution of the sea surface temperature. A comparative analysis of seasonally averaged anomalies of atmospheric circulation shows prospects in applying the coupled model for forecasts. It is shown with the example of the El Niño phenomenon of 1997-1998 that the coupled model forecasts the seasonally averaged anomalies for the period of the nonstationary El Niño phase significantly better.

  18. 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.

  19. The Sensitivity of WRF Daily Summertime Simulations over West Africa to Alternative Parameterizations. Part 1: African Wave Circulation

    NASA Technical Reports Server (NTRS)

    Noble, Erik; Druyan, Leonard M.; Fulakeza, Matthew

    2014-01-01

    The performance of the NCAR Weather Research and Forecasting Model (WRF) as a West African regional-atmospheric model is evaluated. The study tests the sensitivity of WRF-simulated vorticity maxima associated with African easterly waves to 64 combinations of alternative parameterizations in a series of simulations in September. In all, 104 simulations of 12-day duration during 11 consecutive years are examined. The 64 combinations combine WRF parameterizations of cumulus convection, radiation transfer, surface hydrology, and PBL physics. Simulated daily and mean circulation results are validated against NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) and NCEP/Department of Energy Global Reanalysis 2. Precipitation is considered in a second part of this two-part paper. A wide range of 700-hPa vorticity validation scores demonstrates the influence of alternative parameterizations. The best WRF performers achieve correlations against reanalysis of 0.40-0.60 and realistic amplitudes of spatiotemporal variability for the 2006 focus year while a parallel-benchmark simulation by the NASA Regional Model-3 (RM3) achieves higher correlations, but less realistic spatiotemporal variability. The largest favorable impact on WRF-vorticity validation is achieved by selecting the Grell-Devenyi cumulus convection scheme, resulting in higher correlations against reanalysis than simulations using the Kain-Fritch convection. Other parameterizations have less-obvious impact, although WRF configurations incorporating one surface model and PBL scheme consistently performed poorly. A comparison of reanalysis circulation against two NASA radiosonde stations confirms that both reanalyses represent observations well enough to validate the WRF results. Validation statistics for optimized WRF configurations simulating the parallel period during 10 additional years are less favorable than for 2006.

  20. Application of long-circulating liposomes to cancer photodynamic therapy.

    PubMed

    Oku, N; Saito, N; Namba, Y; Tsukada, H; Dolphin, D; Okada, S

    1997-06-01

    Photodynamic therapy (PDT) as a cancer treatment is notable for its quite low side effects in comparison with those of chemotherapy and radiotherapy. However, the accumulation of porphyrin derivatives used in PDT into tumor tissues is rather low. Since long-circulating liposomes are known to accumulate passively into tumor tissues, we liposomalized a porphyrin derivative, benzoporphyrin derivative monoacid ring A (BPD-MA), and used these liposomes to investigate the usefulness of PDT for tumor-bearing mice. BPD-MA was liposomalized into glucuronate-modified liposomes, which are known to be long-circulating. These liposomes were injected i.v. into Balb/c mice bearing Meth A sarcoma, and tumor regression and survival time were monitored after irradiation with laser light. Tumor regression and complete curing of tumor (80% cure rate by the treatment with 6 mg/kg BPD-MA) were observed when long circulating liposomalized BPD-MA was injected and laser-irradiated. In contrast, only a 20% cure rate was obtained when the animals were treated with BPD-MA solution or BPD-MA entrapped in conventional liposomes. These results suggest that a long-circulating liposomal formulation of photo-sensitive agents is useful for PDT. PMID:9212988

  1. Numerical simulation on casing modification of a boiler water circulation pump

    NASA Astrophysics Data System (ADS)

    Li, Y. Z.; Fan, Y. Z.; Liu, S. H.; Wu, Y. L.; Zuo, Z. G.

    2012-11-01

    In this paper, hydraulic performance comparisons are made by numerical simulation method on boiler water circulation pump with casings of different shapes. The existing pump adopts a semispherical casing and a garlic-shaped casing. Results show that in the garlic-shaped casing noticeable swirling vortex can be found in the top region of the discharge nozzle, and semispherical casing has better performance in hydraulic efficiency and head.

  2. 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.

  3. Simulation of 18O in precipitation by the regional circulation model REMOiso

    NASA Astrophysics Data System (ADS)

    Sturm, Kristof; Hoffmann, Georg; Langmann, Bärbel; Stichler, Willibald

    2005-11-01

    The first results of a regional circulation model REMOiso fitted with water isotope diagnostics are compared with various isotope series from central Europe. A 2 year case study is conducted from March 1997 to February 1999 centred over Europe, analysing daily and monthly measurements. Isotope signals over Europe are dominated by the typical isotopic effects such as temperature, continental and altitude effects, both on annual and seasonal scales. These well-known isotopic effects are successfully reproduced by REMOiso, using two different boundary data sets. In a first simulation, the European Centre for Medium-range Weather Forecasts (ECMWF) analyses serve as boundary conditions, where water isotopes were parameterized by a simple temperature dependence. In a second simulation, boundary conditions both for climatic and isotopic variables are taken from the ECHAMiso general circulation model output. The comparison of both simulations shows a very high sensitivity of the simulated 18O signal to boundary conditions. The ECMWF-nested simulation shows an average offset of -4.5 in mean 18O values and exaggerated seasonal amplitude. The ECHAM-nested simulation represents correctly the observed mean 18O values, although with a dampened seasonality. REMOiso's isotope module is further validated against daily 18O measurements at selected stations (Nordeney, Arkona and Hohenpeissenberg) situated in Germany. Copyright

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

    USGS Publications Warehouse

    McKenna, J.E., Jr.; 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.

  5. Processes and Mechanisms in Simulations of the Mid-holocene African Summer Monsoon Circulation

    NASA Astrophysics Data System (ADS)

    Tomas, R. A.; Otto-Bliesner, B.

    2006-12-01

    Proxy reconstructions indicate that the Sahel and Sahara regions were considerably wetter during the early and middle Holocene (about 12 to 5 thousand years ago) than they are presently. Kutzbach (1981) and Kutzbach and Otto-Bliesner (1982) tested whether changes in the Earth's orbital parameters could have caused these climatic changes seen in the observed records. Using a low-resolution general circulation model and orbital parameters that describe conditions 9000 years ago, they found that the increased solar radiation during the summer months caused an intensified monsoon circulation over the African-Eurasian land mass. During the past 25 years, as general circulation models and coupled climate models have evolved, these experiments have been repeated, these results have been reconfirmed and our understanding of what parts of the climate system are important for the anomalous monsoon circulation has been refined. Yet, questions remain about the details of the processes and mechanisms that are important for producing the anomalous monsoon in climate model simulations and there are still some significant discrepancies between simulations and proxy records. We examine simulations of the African summer monsoon made using the latest version of the Community Climate System Model (CCSM3) developed at the National Center for Atmospheric Research (NCAR) forced with orbital parameters and greenhouse gas concentrations appropriate for 6 ka and pre-industrial periods following the protocols established by the Paleoclimate Modeling Intercomparison Project II (PMIP-2). Results from three sets of experiments are presented. In the first, we test to determine to what extent the SST's simulated by CCSM3 influence the anomalous monsoon circulation using a stand alone atmospheric model forced with 6ka orbital parameters but prescribed SST's taken from CCSM3 simulations of the 6ka and pre-industrial periods. In the second, we explore a more fundamental question regarding what

  6. 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.

  7. Fine-grid simulations of gas-solids flow in a circulating fluidized bed

    SciTech Connect

    Benyahia, S.

    2012-01-01

    This research note demonstrates that more accurate predictions of a two-fluid model for the riser section of a circulating fluidized bed are obtained as the grid size is equally refined along all the directions of the gas-particle flow. However, two-fluid simulations of large-scale fluidized beds with such a fine mesh are currently computationally prohibitive. Alternatively,subgrid models can significantly reduce the simulation time of multiphase flow by using coarse mesh, whereas maintaining a high level of accuracy.

  8. 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.

  9. Stationary eddies in the Mars general circulation as simulated by the NASA-Ames GCM

    NASA Technical Reports Server (NTRS)

    Barnes, J. R.; Pollack, J. B.; Haberle, Robert M.

    1993-01-01

    Quasistationary eddies are prominent in a large set of simulations of the Mars general circulation performed with the NASA-Ames GCM. Various spacecraft observations have at least hinted at the existence of such eddies in the Mars atmosphere. The GCM stationary eddies appear to be forced primarily by the large Mars topography, and (to a much lesser degree) by spatial variations in the surface albedo and thermal inertia. The stationary eddy circulations exhibit largest amplitudes at high altitudes (above 30-40 km) in the winter extratropical regions. In these regions they are of planetary scale, characterized largely by zonal wavenumbers 1 and 2. Southern Hemisphere winter appears to be dominated by a very strong wave 1 pattern, with both waves 1 and 2 being prominent in the Northern Hemisphere winter regime. This difference seems to be basically understandable in terms of differences in the topography in the two hemispheres. The stationary eddies in the northern winter extratropics are found to increase in amplitude with dust loading. This behavior appears to be at least partly associated with changes in the structure of the zonal-mean flow that favor a greater response to wave 1 topographic forcing. There are also strong stationary eddy circulations in the tropics and in the summer hemisphere. The eddies in the summer subtropics and extratropics arc substantially stronger in southern summer than in northern summer. The summer hemisphere stationary circulations are relatively shallow and are characterized by smaller zonal scales than those in the winter extratropics.

  10. Importance of a control state for simulating the Atlantic meridional overturning circulation at the LGM

    NASA Astrophysics Data System (ADS)

    Oka, A.; Abe-Ouchi, A.; Hasumi, H.

    2009-04-01

    The ocean circulation in the Atlantic deep ocean is characterized by thermohaline circulation driven by deep convection in northern high latitudes. The heat transport associated with this circulation is comparable to that by atmosphere and has a great role in the present climate. The Atlantic meridional overturning circulation (AMOC) is believed to change in past and future climate changes. Coupled model simulations suggest that the AMOC becomes weak in the future global warming climate. Geological evidence such as carbon isotope ratio indicates that the AMOC was weaker and shallower than the present at the Last Glacial Maximum (LGM). As for global warming climate, almost all model results reach consensus that the AMOC weakens in global warming climate. On the other hand, there is wide discrepancy in simulation of the AMOC at the LGM. Weber et al. (2007) report results of Paleoclimate Modeling Intercomparison Project where half of models reproduce the weakening of the AMOC but the other half simulates the strengthening. The reason for this disagreement between models has not been clarified yet, and investigation on the mechanism of weakening of the AMOC at the LGM is one of the most important topics in the paleoclimate studies. In this study, by using results of our coupled climate model (MIROC), we focus on role of changes in the sea surface heat and freshwater fluxes and investigate their role in controlling the AMOC at the LGM. In order to individually evaluate role of heat and freshwater fluxes, we conduct additional ocean general circulation model simulations under the sea surface heat/freshwater flux conditions obtained from the present and LGM simulations by MIROC. The results suggest that the freshwater flux changes contribute to weakening of the AMOC at the LGM, whereas the heat flux changes make the AMOC at the LGM stronger than the present. We found that reproducibility of the control state significantly affects response of the AMOC to heat and

  11. Reynolds-Averaged Navier-Stokes Simulation of a 2D Circulation Control Wind Tunnel Experiment

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Jones, Greg; Lin, John C.

    2011-01-01

    Numerical simulations are performed using a Reynolds-averaged Navier-Stokes (RANS) flow solver for a circulation control airfoil. 2D and 3D simulation results are compared to a circulation control wind tunnel test conducted at the NASA Langley Basic Aerodynamics Research Tunnel (BART). The RANS simulations are compared to a low blowing case with a jet momentum coefficient, C(sub u), of 0:047 and a higher blowing case of 0.115. Three dimensional simulations of the model and tunnel walls show wall effects on the lift and airfoil surface pressures. These wall effects include a 4% decrease of the midspan sectional lift for the C(sub u) 0.115 blowing condition. Simulations comparing the performance of the Spalart Allmaras (SA) and Shear Stress Transport (SST) turbulence models are also made, showing the SST model compares best to the experimental data. A Rotational/Curvature Correction (RCC) to the turbulence model is also evaluated demonstrating an improvement in the CFD predictions.

  12. Prediction of circulation control performance characteristics for Super STOL and STOL applications

    NASA Astrophysics Data System (ADS)

    Naqvi, Messam Abbas

    by the model. The same optimal configurations were then subjected to Super STOL cruise conditions to perform a trade off analysis between Takeoff and Cruise Performance. Supercritical airfoils modified for circulation control were also thoroughly analyzed for Takeoff and Cruise performance and may constitute a viable option for Super STOL & STOL Designs. The prediction capability produced by this research effort can be integrated with the current conceptual aircraft modeling & simulation framework. The prediction tool is applicable within the selected ranges of each variable, but methodology and formulation scheme adopted can be applied to any other design space exploration.

  13. The impact of a realistic vertical dust distribution on the simulation of the Martian General Circulation

    NASA Astrophysics Data System (ADS)

    Guzewich, Scott D.; Toigo, Anthony D.; Richardson, Mark I.; Newman, Claire E.; Talaat, Elsayed R.; Waugh, Darryn W.; McConnochie, Timothy H.

    2013-05-01

    Limb-scanning observations with the Mars Climate Sounder and Thermal Emission Spectrometer (TES) have identified discrete layers of enhanced dust opacity well above the boundary layer and a mean vertical structure of dust opacity very different from the expectation of well-mixed dust in the lowest 1-2 scale heights. To assess the impact of this vertical dust opacity profile on atmospheric properties, we developed a TES limb-scan observation-based three-dimensional and time-evolving dust climatology for use in forcing general circulation models (GCMs). We use this to force the MarsWRF GCM and compare with simulations that use a well-mixed (Conrath-ν) vertical dust profile and Mars Climate Database version 4 (MCD) horizontal distribution dust opacity forcing function. We find that simulated temperatures using the TES-derived forcing yield a 1.18 standard deviation closer match to TES temperature retrievals than a MarsWRF simulation using MCD forcing. The climatological forcing yields significant changes to many large-scale features of the simulated atmosphere. Notably the high-latitude westerly jet speeds are 10-20 m/s higher, polar warming collar temperatures are 20-30 K warmer near northern winter solstice and tilted more strongly poleward, the middle and lower atmospheric meridional circulations are partially decoupled, the migrating diurnal tide exhibits destructive interference and is weakened by 50% outside of equinox, and the southern hemisphere wave number 1 stationary wave is strengthened by up to 4 K (45%). We find the vertical dust distribution is an important factor for Martian lower and middle atmospheric thermal structure and circulation that cannot be neglected in analysis and simulation of the Martian atmosphere.

  14. Overview of CFD Validation Experiments for Circulation Control Applications at NASA

    NASA Technical Reports Server (NTRS)

    Jones, G. S.; Lin, J. C.; Allan, B. G.; Milholen, W. E.; Rumsey, C. L.; Swanson, R. C.

    2008-01-01

    Circulation control is a viable active flow control approach that can be used to meet the NASA Subsonic Fixed Wing project s Cruise Efficient Short Take Off and Landing goals. Currently, circulation control systems are primarily designed using empirical methods. However, large uncertainty in our ability to predict circulation control performance has led to the development of advanced CFD methods. This paper provides an overview of a systematic approach to developing CFD tools for basic and advanced circulation control applications. This four-step approach includes "Unit", "Benchmar", "Subsystem", and "Complete System" experiments. The paper emphasizes the ongoing and planned 2-D and 3-D physics orientated experiments with corresponding CFD efforts. Sample data are used to highlight the challenges involved in conducting circulation control computations and experiments.

  15. 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.

  16. Development of an Accident Reproduction Simulator System Using a Hemodialysis Extracorporeal Circulation System

    PubMed Central

    Nishite, Yoshiaki; Takesawa, Shingo

    2016-01-01

    Background: Accidents that occur during dialysis treatment are notified to the medical staff via alarms raised by the dialysis apparatus. Similar to such real accidents, apparatus activation or accidents can be reproduced by simulating a treatment situation. An alarm that corresponds to such accidents can be utilized in the simulation model. Objectives: The aim of this study was to create an extracorporeal circulation system (hereinafter, the circulation system) for dialysis machines so that it sets off five types of alarms for: 1) decreased arterial pressure, 2) increased arterial pressure, 3) decreased venous pressure, 4) increased venous pressure, and 5) blood leakage, according to the five types of accidents chosen based on their frequency of occurrence and the degree of severity. Materials and Methods: In order to verify the alarm from the dialysis apparatus connected to the circulation system and the accident corresponding to it, an evaluation of the alarm for its reproducibility of an accident was performed under normal treatment circumstances. The method involved testing whether the dialysis apparatus raised the desired alarm from the moment of control of the circulation system, and measuring the time it took until the desired alarm was activated. This was tested on five main models from four dialyzer manufacturers that are currently used in Japan. Results: The results of the tests demonstrated successful activation of the alarms by the dialysis apparatus, which were appropriate for each of the five types of accidents. The time between the control of the circulatory system to the alarm signal was as follows, 1) venous pressure lower limit alarm: 7 seconds; 2) venous pressure lower limit: 8 seconds; 3) venous pressure upper limit: 7 seconds; 4) venous pressure lower limit alarm: 2 seconds; and 5) blood leakage alarm: 19 seconds. All alarms were set off in under 20 seconds. Conclusions: Thus, we can conclude that a simulator system using an extracorporeal

  17. Multiscale dynamical analysis of a high-resolution numerical model simulation of the Solomon Sea circulation

    NASA Astrophysics Data System (ADS)

    Djath, Bughsin'; Verron, Jacques; Melet, Angelique; Gourdeau, Lionel; Barnier, Bernard; Molines, Jean-Marc

    2014-09-01

    A high 1/36° resolution numerical model is used to study the ocean circulation in the Solomon Sea. An evaluation of the model with (the few) available observation shows that the 1/36° resolution model realistically simulates the Solomon Sea circulations. The model notably reproduces the high levels of mesoscale eddy activity observed in the Solomon Sea. With regard to previous simulations at 1/12° resolution, the average eddy kinetic energy levels are increased by up to ˜30-40% in the present 1/36° simulation, and the enhancement extends at depth. At the surface, the eddy kinetic energy level is maximum in March-April-May and is minimum in December-January-February. The high subsurface variability is related to the variability of the western boundary current (New Guinea Coastal Undercurrent). Moreover, the emergence of submesoscales is clearly apparent in the present simulations. A spectral analysis is conducted in order to evidence and characterize the modeled submesoscale dynamics and to provide a spectral view of scales interactions. The corresponding spectral slopes show a strong consistency with the Surface Quasi-Geostrophic turbulence theory.

  18. A comparison between general circulation model simulations using two sea surface temperature datasets for January 1979

    NASA Technical Reports Server (NTRS)

    Ose, Tomoaki; Mechoso, Carlos; Halpern, David

    1994-01-01

    Simulations with the UCLA atmospheric general circulation model (AGCM) using two different global sea surface temperature (SST) datasets for January 1979 are compared. One of these datasets is based on Comprehensive Ocean-Atmosphere Data Set (COADS) (SSTs) at locations where there are ship reports, and climatology elsewhere; the other is derived from measurements by instruments onboard NOAA satellites. In the former dataset (COADS SST), data are concentrated along shipping routes in the Northern Hemisphere; in the latter dataset High Resolution Infrared Sounder (HIRS SST), data cover the global domain. Ensembles of five 30-day mean fields are obtained from integrations performed in the perpetual-January mode. The results are presented as anomalies, that is, departures of each ensemble mean from that produced in a control simulation with climatological SSTs. Large differences are found between the anomalies obtained using COADS and HIRS SSTs, even in the Northern Hemisphere where the datasets are most similar to each other. The internal variability of the circulation in the control simulation and the simulated atmospheric response to anomalous forcings appear to be linked in that the pattern of geopotential height anomalies obtained using COADS SSTs resembles the first empirical orthogonal function (EOF 1) in the control simulation. The corresponding pattern obtained using HIRS SSTs is substantially different and somewhat resembles EOF 2 in the sector from central North America to central Asia. To gain insight into the reasons for these results, three additional simulations are carried out with SST anomalies confined to regions where COADS SSTs are substantially warmer than HIRS SSTs. The regions correspond to warm pools in the northwest and northeast Pacific, and the northwest Atlantic. These warm pools tend to produce positive geopotential height anomalies in the northeastern part of the corresponding oceans. Both warm pools in the Pacific produce large

  19. A Solar Sailcraft Simulation Application

    ERIC Educational Resources Information Center

    Celeda, Tomáš

    2013-01-01

    An application was created to encourage students' practical knowledge of gravitational fields, the law of conservation of energy and other phenomena, such as gravitational slingshots. The educational software simulates the flight of a solar sail spacecraft between two planets of the Solar System using the laws of gravity and radiation…

  20. CMIP5 simulated change in the intensity of the Hadley and Walker circulations from the perspective of velocity potential

    NASA Astrophysics Data System (ADS)

    Zhou, Botao; Shi, Ying; Xu, Ying

    2016-07-01

    Based on the simulations of 31 global models in CMIP5, the performance of the models in simulating the Hadley and Walker circulations is evaluated. In addition, their change in intensity by the end of the 21st century (2080-2099) under the RCP4.5 and RCP8.5 scenarios, relative to 1986-2005, is analyzed from the perspective of 200 hPa velocity potential. Validation shows good performance of the individual CMIP5 models and the multi-model ensemble mean (MME) in reproducing the meridional (zonal) structure and magnitude of Hadley (Walker) circulation. The MME can also capture the observed strengthening tendency of the winter Hadley circulation and weakening tendency of the Walker circulation. Such secular trends can be simulated by 39% and 74% of the models, respectively. The MME projection indicates that the winter Hadley circulation and the Walker circulation will weaken under both scenarios by the end of the 21st century. The weakening amplitude is larger under RCP8.5 than RCP4.5, due to stronger external forcing. The majority of the CMIP5 models show the same projection as the MME. However, for the summer Hadley circulation, the MME shows little change under RCP4.5 and large intermodel spread is apparent. Around half of the models project an increase, and the other half project a decrease. Under the RCP8.5 scenario, the MME and 65% of the models project a weakening of the summer southern Hadley circulation.

  1. Synoptic-climatological applicability of multiple circulation classifications

    NASA Astrophysics Data System (ADS)

    Huth, Radan; Beck, Christoph; Cahynová, Monika

    2013-04-01

    The database of classifications of atmospheric circulation patterns, which was produced within the COST733 Action, consists in its version v2.0 of 423 different classifications for each of 12 domains over Europe. The classifications differ from each other in five characteristics: (i) the classification method used, (ii) the number of types, (iii) the classified variable, (iv) sequentiality (whether instantaneous circulation patterns or their 4-day sequences are classified), and (v) the seasonality of definition (whether classifications are defined for a whole year or separately for each season). The goal of the study is to evaluate how successful are the classifications in characterizing (stratifying) surface climate elements, viz., daily minimum and maximum temperature and precipitation. To this end, we employ several criteria: explained variance, pseudo-F statistic, and Kolmogorov-Smirnov statistic. Both station datasets (ECA&D) and reanalysis (ERA-40) are used. The classifications are ranked in each domain separately. This allows one to evaluate the effect the options (i) to (v) have on the quality of classifications in terms of the stratification of surface temperature and precipitation, to compare the performance among the criteria, and to assess the geographical dependence of the findings.

  2. A dynamic simulation model for power plants with atmospheric and pressurized circulating fluidized bed combustion -- Interactions of plant components and design studies

    SciTech Connect

    Glasmacher-Remberg, C.; Fett, F.N.

    1999-07-01

    Power plants with atmospheric or pressurized circulating fluidized bed combustion are complex technical systems. The operation characteristics of these power plants depend on the behavior of the single components and their interactions. The theoretical understanding of power plant processes of this kind as well as the design, the reliability and the practical operation can be enhanced by the application of mathematical models for the complete process. A dynamic simulation model for power plants with atmospheric circulating fluidized bed combustion (ACFBC) and pressurized circulating fluidized bed combustion (PCFBC) consisting of comprehensive submodels for the subsystems gas turbine, circulating fluidized bed combustor and water/steam cycle is presented. Apart from the investigation of the complete power plant, the simulation program enables the analysis of the three mentioned subsystems separately. Each subsystem is described by a set of unsteady-state differential and algebraic equations solved by an implicit Euler-method using a modified Newton-Raphson method. With the aid of the dynamic simulation program for a selected power plant, the effect of changes in plant operation will be examined for full and part load as well as the transient response of the system due to the carried out operation. Emphasis is laid on the characterization of the interactions between the subsystems. The dynamic simulation program can be used for design studies and it is investigated how changes of the plant design influence the operation characteristics of the example plant.

  3. MFIX simulation of NETL/PSRI challenge problem of circulating fluidized bed

    DOE PAGESBeta

    Li, Tingwen; Dietiker, Jean-François; Shahnam, Mehrdad

    2012-12-01

    In this paper, numerical simulations of NETL/PSRI challenge problem of circulating fluidized bed (CFB) using the open-source code Multiphase Flow with Interphase eXchange (MFIX) are reported. Two rounds of simulation results are reported including the first-round blind test and the second-round modeling refinement. Three-dimensional high fidelity simulations are conducted to model a 12-inch diameter pilot-scale CFB riser. Detailed comparisons between numerical results and experimental data are made with respect to axial pressure gradient profile, radial profiles of solids velocity and solids mass flux along different radial directions at various elevations for operating conditions covering different fluidization regimes. Overall, the numericalmore » results show that CFD can predict the complex gas–solids flow behavior in the CFB riser reasonably well. In addition, lessons learnt from modeling this challenge problem are presented.« less

  4. MFIX simulation of NETL/PSRI challenge problem of circulating fluidized bed

    SciTech Connect

    Li, Tingwen; Dietiker, Jean-François; Shahnam, Mehrdad

    2012-12-01

    In this paper, numerical simulations of NETL/PSRI challenge problem of circulating fluidized bed (CFB) using the open-source code Multiphase Flow with Interphase eXchange (MFIX) are reported. Two rounds of simulation results are reported including the first-round blind test and the second-round modeling refinement. Three-dimensional high fidelity simulations are conducted to model a 12-inch diameter pilot-scale CFB riser. Detailed comparisons between numerical results and experimental data are made with respect to axial pressure gradient profile, radial profiles of solids velocity and solids mass flux along different radial directions at various elevations for operating conditions covering different fluidization regimes. Overall, the numerical results show that CFD can predict the complex gas–solids flow behavior in the CFB riser reasonably well. In addition, lessons learnt from modeling this challenge problem are presented.

  5. 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.

  6. Large-eddy simulations of flow around a circulation control airfoil

    NASA Astrophysics Data System (ADS)

    Hahn, Seonghyeon; Shariff, Karim

    2008-11-01

    Circulation control, proposed in NASA's Cruise Efficient Short Take-off and Landing (CESTOL) concept, has the potential to increase air-traffic throughput and reduce the noise footprint. Circulation control obtains a substantial increase in lift coefficient by using a wall-jet that blows tangentially on a rounded (Coanda) surface deflected at the trailing edge. The flow has proven to be difficult to reliably predict using Reynolds-averaged models. We undertake large-eddy simulations to better understand underlying mechanisms and create a database for modelers. Simulations are patterned after Novak et al.'s (1987) experiment, which, despite its faults, is the best documented to date. A Reynolds number of 10̂6 and two cases with low and high blowing are considered using Stanford's unstructured solver CDP. The upper surface begins with laminar to turbulent transition following a region of weak shear stress. Then strong favorable pressure gradient as the jet slot is approached leads to a raised log-law. There exists a region over the Coanda surface where the mean flow development collapses very well in wall-jet similarity coordinates, indicating that a portion of the near-wall region maintains classical wall-jet characteristics. At the present time, the lower surface has delayed transition due to lack of tripping in the simulations and considerable discrepancies with the experiments for second-order statistics.

  7. Simulations of Flow Circulations and Atrazine Concentrations in a Midwest U.S. Reservoir

    NASA Astrophysics Data System (ADS)

    Zhao, Xianggui; Gu, Roy R.; Guo, Chuling; Wang, Kui; Li, Shijie

    Atrazine is the most commonly used herbicide in the spring for pre-emergent weed control in the corn cropping area in the Midwestern United States. A frequent high level of herbicide concentrations in reservoirs is a great concern for public health and aquatic ecosystems. In this study, a two-dimensional hydrodynamics and toxic contaminant transport model was applied to Saylorville Reservoir, Iowa, USA. The model simulates physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. Model results were validated by measured temperatures and atrazine concentrations. Simulated flow velocities, water temperatures, and chemical concentrations demonstrated that the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation patterns in the reservoir. In particular, the simulated fate and transport of atrazine showed the effect of flow circulation on spatial distribution of atrazine during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A thorough understanding of the fate and transport of atrazine in the reservoir can assist in developing operation and pollution prevention strategies with respect to timing, amount, and depth of withdrawal. The responses of atrazine transport to various boundary conditions provide useful information in assessing environmental impact of alternative upstream watershed management practices on the quality of reservoir water.

  8. 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.

  9. Circulation induced by subglacial discharge in glacial fjords: Results from idealized numerical simulations

    NASA Astrophysics Data System (ADS)

    Salcedo-Castro, Julio; Bourgault, Daniel; deYoung, Brad

    2011-09-01

    The flow caused by the discharge of freshwater underneath a glacier into an idealized fjord is simulated with a 2D non-hydrostatic model. As the freshwater leaves horizontally the subglacial opening into a fjord of uniformly denser water it spreads along the bottom as a jet, until buoyancy forces it to rise. During the initial rising phase, the plume meanders into complex flow patterns while mixing with the surrounding fluid until it reaches the surface and then spreads horizontally as a surface seaward flowing plume of brackish water. The process induces an estuarine-like circulation. Once steady-state is reached, the flow consists of an almost undiluted buoyant plume rising straight along the face of the glacier that turns into a horizontal surface layer thickening as it flows seaward. Over the range of parameters examined, the estuarine circulation is dynamically unstable with gradient Richardson number at the sheared interface having values of <1/4. The surface velocity and dilution factors are strongly and non-linearly related to the Froude number. It is the buoyancy flux that primarily controls the resulting circulation with the momentum flux playing a secondary role.

  10. Role of Eurasian snow cover in wintertime circulation: Decadal simulations forced with satellite observations

    NASA Astrophysics Data System (ADS)

    Orsolini, Yvan J.; Kvamstø, Nils G.

    2009-10-01

    We investigate the impact of the Eurasian snow cover extent on the Northern Hemisphere winter circulation by performing a suite of ensemble simulations with the Météo-France "Arpege Climat" atmospheric general circulation model, spanning 2 decades (1979-2000). Observed snow cover derived from satellite infrared and visible imagery has been forced weekly into the model. Variability in autumn-early winter snow cover extent over eastern Eurasia is linked to circulation anomalies over the North Pacific that are influencing the North Atlantic sector in late winter through the development of the Aleutian-Icelandic Low Seesaw teleconnection. The forcing of realistic snow cover in the model augments potential predictability over eastern Eurasia and the North Pacific and improves the hindcast skill score of the Aleutian-Icelandic Low Seesaw teleconnection. Enhanced eastern Eurasia snow cover is associated with an anomalous upper-tropospheric wave train across Eurasia, anomalously high upward wave activity flux, and a displaced stratospheric polar vortex.

  11. In Vitro Simulation and Validation of the Circulation with Congenital Heart Defects

    PubMed Central

    Figliola, Richard S.; Giardini, Alessandro; Conover, Tim; Camp, Tiffany A.; Biglino, Giovanni; Chiulli, John; Hsia, Tain-Yen

    2010-01-01

    Despite the recent advances in computational modeling, experimental simulation of the circulation with congenital heart defect using mock flow circuits remains an important tool for device testing, and for detailing the probable flow consequences resulting from surgical and interventional corrections. Validated mock circuits can be applied to qualify the results from novel computational models. New mathematical tools, coupled with advanced clinical imaging methods, allow for improved assessment of experimental circuit performance relative to human function, as well as the potential for patient-specific adaptation. In this review, we address the development of three in vitro mock circuits specific for studies of congenital heart defects. Performance of an in vitro right heart circulation circuit through a series of verification and validation exercises is described, including correlations with animal studies, and quantifying the effects of circuit inertiance on test results. We present our experience in the design of mock circuits suitable for investigations of the characteristics of the Fontan circulation. We use one such mock circuit to evaluate the accuracy of Doppler predictions in the presence of aortic coarctation. PMID:21218147

  12. 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.

  13. Simulation of hydrodynamics using large eddy simulation-second-order moment model in circulating fluidized beds

    NASA Astrophysics Data System (ADS)

    Juhui, Chen; Yanjia, Tang; Dan, Li; Pengfei, Xu; Huilin, Lu

    2013-07-01

    Flow behavior of gas and particles is predicted by the large eddy simulation of gas-second order moment of solid model (LES-SOM model) in the simulation of flow behavior in CFB. This study shows that the simulated solid volume fractions along height using a two-dimensional model are in agreement with experiments. The velocity, volume fraction and second-order moments of particles are computed. The second-order moments of clusters are calculated. The solid volume fraction, velocity and second order moments are compared at the three different model constants.

  14. Application of sonography for evaluation of posterior circulation disorders.

    PubMed

    Alpaidze, M; Janelidze, M

    2014-03-01

    Posterior circulation disorders (PCD) include a) vertebrobasilar insufficiency (VBI), which has a wide clinical manifestation such as vestibulocerebellar syndrome, cephalalgia, cochlear syndrome, vegetovascular dystonia, visual disturbances, "syndrome of vertebral artery compression" etc, b) vertebrobasilar TIA and c) stroke. All of them are caused by blood flow disturbances in vertebral (VA), basilar (BAS) and posterior cerebral arteries (PCA). Aim - evaluation of role of extracranial duplex-sonography (EDS), transcranial color-coded duplex-sonography (TCCD) and rotational functional tests (RFT) in PCD. 88 patients (age range 18-62y) with PCD and 20 healthy controls with relevant age range were examined using EDS, TCCD and RFT with measurement of vertebral arteries (VA) diameter, mean flow velocities (MFV) and pulsatility index (PI) in VA, basilar artery (BAS) and posterior cerebral arteries (PCA). For statistical analysis SPSS software (Version 11.5) was used. In 48 (54,5%) patients revealed unilateral narrowing (less than 2.5 mm in diameter) and deformation of vertebral artery associated with osteochondrosis or primary hypoplasia. In 11 (12,5%) patients revealed bilateral narrowing (less than 2.8 mm in diameter) and deformation of vertebral arteries. Ultrasound investigation showed a decrease of MFV (23 ± 1.4 cm/sec) in the intracranial length of vertebral artery and an increase of PI (3,2 ±0,3 p=0,002) in the extracranial segments (V1- V3). In 52 cases (59%) revealed decrease of MFV in BAS by 32.6 ± 4.7% and in 41 cases (46.5%) decrease of MFV in both PCA by 24.8 ± 5.2% (P<0.002). In 21 cases (23.8%) revealed concurrent development of vertebrogenic reflex vasoconstriction. In 18 patients (20.4%) exposed only deformation of vertebral arteries with local increase of MFV and normal values in intracranial segments. Rotational tests were positive in 42 (47.7%) patients and manifested high correlation with clinical data. EDS and TCCD are important tools for

  15. Simulation of Venus polar vortices with the non-hydrostatic general circulation model

    NASA Astrophysics Data System (ADS)

    Rodin, Alexander V.; Mingalev, Oleg; Orlov, Konstantin

    2012-07-01

    The dynamics of Venus atmosphere in the polar regions presents a challenge for general circulation models. Numerous images and hyperspectral data from Venus Express mission shows that above 60 degrees latitude atmospheric motion is substantially different from that of the tropical and extratropical atmosphere. In particular, extended polar hoods composed presumably of fine haze particles, as well as polar vortices revealing mesoscale wave perturbations with variable zonal wavenumbers, imply the significance of vertical motion in these circulation elements. On these scales, however, hydrostatic balance commonly used in the general circulation models is no longer valid, and vertical forces have to be taken into account to obtain correct wind field. We present the first non-hydrostatic general circulation model of the Venus atmosphere based on the full set of gas dynamics equations. The model uses uniform grid with the resolution of 1.2 degrees in horizontal and 200 m in the vertical direction. Thermal forcing is simulated by means of relaxation approximation with specified thermal profile and time scale. The model takes advantage of hybrid calculations on graphical processors using CUDA technology in order to increase performance. Simulations show that vorticity is concentrated at high latitudes within planetary scale, off-axis vortices, precessing with a period of 30 to 40 days. The scale and position of these vortices coincides with polar hoods observed in the UV images. The regions characterized with high vorticity are surrounded by series of small vortices which may be caused by shear instability of the zonal flow. Vertical velocity component implies that in the central part of high vorticity areas atmospheric flow is downwelling and perturbed by mesoscale waves with zonal wavenumbers 1-4, resembling observed wave structures in the polar vortices. Simulations also show the existence of areas with strong vertical flow, concentrated in spiral branches extending

  16. Decadal Variations of the Atlantic Meridional Overturning Circulation as simulated by the VIKING20 Model

    NASA Astrophysics Data System (ADS)

    Handmann, Patricia; Fischer, Jürgen; Visbeck, Martin; Behrens, Erik; Patara, Lavinia

    2015-04-01

    Time series of observed deep circulation transports and water mass properties in the subpolar North Atlantic are beginning to be long enough to investigate multiannual to decadal variability of the deep water. At the same time high resolution ocean circulation models (1/20° resolution VIKING20 model) can be used to compare observations with model simulation. The models also allow to diagnose the deep water circulation processes more completely and to relate local to basin scale signals. North Atlantic Deep Water (NADW) is a complex combination of water masses from different origins and pathways that meet at the exit of the Labrador Sea. The lower part of NADW is formed by water masses entering the subpolar basin over the Greenland-Scotland ridge. Iceland-Scotland Overflow Water (ISOW) from the eastern sills has the longest pathway and joins the densest deep water component from Denmark Strait (DSOW) after crossing the Mid-Atlantic-Ridge through Charlie-Gibbs Fracture Zone (CGFZ); together, they form the Lower NADW. The upper component of the NADW is composed of Labrador Sea Water (LSW), which is formed and modified through deep convection in the Labrador Sea. Using 60 year long time series of North Atlantic water masses and currents produced by the Viking20 model driven by observed monthly winds, a comparison of transport variability of observed and modeled data will be presented at three locations: Deep flow at the exit of the Labrador Sea at 53°N; upper layer transports between New Jersey and Bermuda (OLEANDER section) and between the southern tip of Greenland and Portugal (OVIDE section). Is the model reproducing the observed long-term behavior of the different components in phase and amplitude? Do the results permit identification of the processes leading to these variations in transport variability? Finally, is it possible to extend the observed variability pattern over the observed time span (15 years) to the total time range of the model simulations (60

  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. Numerical Simulation of the tidal effects on estuarine circulation in the San Juan Bay

    NASA Astrophysics Data System (ADS)

    Garcia, Edgardo; Canals, Miguel; Capella, Jorge; Morell, Julio; Leonardi, Stefano; Caribbean Coastal Ocean Observing System Collaboration

    2012-11-01

    The regional oceanic modeling system ROMS has been implemented in San Juan Bay, Puerto Rico, to investigate quantitatively the mixing processes and as a forecast tool to support emergency planning and resource management in the area. The response of the San Juan Bay circulation to both river discharges and tidal forcing has been investigated. A hind-cast simulation is performed and compared with time series measurements and hidrographic data to validate the model. Sensitivity studies to turbulence mixing parameterization have been carried out under different forcing scenarios. A simulation without river outflow but forced with tidal constituents along the open boundaries is performed. Good agreement has been found with coastal observations with amplitudes gauges and modeled amplitudes constituents. A numerical experiment of the response of the Bay's circulation to river discharge only is performed and compared with the tide plus river forcing and tidal forcing only scenarios. Salinity distributions and vertical mixing are affected by the proximity to deep waters of the San Juan Bay Estuary, also the bulge region and plume structure in the entrance of San Juan Bay are highly affected by the bottom friction for the case with tide forcing.

  19. The cyclonic circulation in the Australian-Antarctic basin simulated by an eddy-resolving general circulation model

    NASA Astrophysics Data System (ADS)

    Aoki, Shigeru; Sasai, Yoshikazu; Sasaki, Hideharu; Mitsudera, Humio; Williams, Guy D.

    2010-06-01

    Flow structure in the Australian-Antarctic basin is investigated using an eddy-resolving general ocean circulation model and validated with iceberg and middepth float trajectories. A cyclonic circulation system between the Antarctic Circumpolar Current and Antarctic Slope Current consists of a large-scale gyre in the west (80-110° E) and a series of eddies in the east (120-150° E). The western gyre has an annual mean westward transport of 22 Sv in the southern limb. Extending west through the Princess Elizabeth Trough, 5 Sv of the gyre recirculates off Prydz Bay and joins the western boundary current off the Kerguelen Plateau. Iceberg trajectories from QuickScat and ERS-1/2 support this recirculation and the overall structure of the Antarctic Slope Current against isobath in the model. Argo float trajectories also reveal a consistent structure of the deep westward slope current. This study indicates the presence of a large cyclonic circulation in this basin, which is comparable to the Weddell and Ross gyres.

  20. Single and two-phase natural circulation in Westinghouse pressurized water reactor simulators: Phenomena, analysis and scaling

    SciTech Connect

    Schultz, R.R.; Chapman, J.C.; Kukita, Y.; Motley, F.E.; Stumpf, H.; Chen, Y.S.; Tasaka, K.

    1987-01-01

    Natural circulation data obtained in the 1/48 scale W four loop PWR simulator - the Large Scale Test Facility (LSTF) are discussed and summarized. Core cooling modes, the primary fluid state, the primary loop mass flow and localized natural circulation phenomena occurring in the steam generator are presented. TRAC-PF1 LSTF model (using both a 1 U-tube and a 3 U-tube steam generator model) analyses of the LSTF natural circulation data including the SG recirculation patterns are presented and compared to the data. The LSTF data are then compared to similar natural circulation data obtained in the Primarkreislaufe (PKL) and the Semiscale facilities. Based on the 1/48 to 1/1705 scaling range which exists between the facilities, the implications of these data towrard natural circulation behavior in commercial plants are briefly discussed.

  1. Scaling laws for parametrizations of subgrid interactions in simulations of oceanic circulations.

    PubMed

    Kitsios, V; Frederiksen, J S; Zidikheri, M J

    2014-06-28

    Parametrizations of the subgrid eddy-eddy and eddy-meanfield interactions are developed for the simulation of baroclinic ocean circulations representative of an idealized Antarctic Circumpolar Current. Benchmark simulations are generated using a spectral spherical harmonic quasi-geostrophic model with maximum truncation wavenumber of T=504, which is equivalent to a resolution of 0.24° globally. A stochastic parametrization is used for the eddy-eddy interactions, and a linear deterministic parametrization for the eddy-meanfield interactions. The parametrization coefficients are determined from the statistics of benchmark simulations truncated back to the large eddy simulation (LES) truncation wavenumber, TRsimulations. PMID:24842029

  2. Scaling laws for parametrizations of subgrid interactions in simulations of oceanic circulations

    PubMed Central

    Kitsios, V.; Frederiksen, J. S.; Zidikheri, M. J.

    2014-01-01

    Parametrizations of the subgrid eddy–eddy and eddy–meanfield interactions are developed for the simulation of baroclinic ocean circulations representative of an idealized Antarctic Circumpolar Current. Benchmark simulations are generated using a spectral spherical harmonic quasi-geostrophic model with maximum truncation wavenumber of T=504, which is equivalent to a resolution of 0.24° globally. A stochastic parametrization is used for the eddy–eddy interactions, and a linear deterministic parametrization for the eddy–meanfield interactions. The parametrization coefficients are determined from the statistics of benchmark simulations truncated back to the large eddy simulation (LES) truncation wavenumber, TRsimulations. PMID:24842029

  3. Simulation of the equatorially asymmetric mode of the Hadley circulation in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Feng, Juan; Li, Jianping; Zhu, Jianlei; Li, Fei; Sun, Cheng

    2015-08-01

    The tropical Hadley circulation (HC) plays an important role in influencing the climate in the tropics and extra-tropics. The realism of the climatological characteristics, spatial structure, and temporal evolution of the long-term variation of the principal mode of the annual mean HC (i.e., the equatorially asymmetric mode, EAM) was examined in model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results showed that all the models are moderately successful in capturing the HC's climatological features, including the spatial pattern, meridional extent, and intensity, but not the spatial or temporal variation of the EAM. The possible reasons for the poor simulation of the long-term variability of the EAM were explored. None of the models can successfully capture the differences in the warming rate between the tropical Southern Hemisphere (SH) and Northern Hemisphere (NH), which is considered to be an important driver for the variation of the AM. Most of the models produce a faster warming in the NH than in the SH, which is the reverse of the observed trend. This leads to a reversed trend in the meridional gradient between the SH and NH, and contributes to the poor simulation of EAM variability. Thus, this aspect of the models should be improved to provide better simulations of the variability of the HC. This study suggests a possible reason for the poor simulation of the HC, which may be helpful for improving the skill of the CMIP5 models in the future.

  4. Inter-annual variability of the Mediterranean thermohaline circulation in Med-CORDEX simulations

    NASA Astrophysics Data System (ADS)

    Vittoria Struglia, Maria; Adani, Mario; Carillo, Adriana; Pisacane, Giovanna; Sannino, Gianmaria; Beuvier, Jonathan; Lovato, Tomas; Sevault, Florence; Vervatis, Vassilios

    2016-04-01

    Recent atmospheric reanalysis products, such as ERA40 and ERA-interim, and their regional dynamical downscaling prompted the HyMeX/Med-CORDEX community to perform hind-cast simulations of the Mediterranean Sea, giving the opportunity to evaluate the response of different ocean models to a realistic inter-annual atmospheric forcing. Ocean numerical modeling studies have been steadily improving over the last decade through hind-cast processing, and are complementary to observations in studying the relative importance of the mechanisms playing a role in ocean variability, either external forcing or internal ocean variability. This work presents a review and an inter-comparison of the most recent hind-cast simulations of the Mediterranean Sea Circulation, produced in the framework of the Med-CORDEX initiative, at resolutions spanning from 1/8° to 1/16°. The richness of the simulations available for this study is exploited to address the effects of increasing resolution, both of models and forcing, the initialization procedure, and the prescription of the atmospheric boundary conditions, which are particularly relevant in order to model a realistic THC, in the perspective of fully coupled regional ocean-atmosphere models. The mean circulation is well reproduced by all the simulations. However, it can be observed that the horizontal resolution of both atmospheric forcing and ocean model plays a fundamental role in the reproduction of some specific features of both sub-basins and important differences can be observed among low and high resolution atmosphere forcing. We analyze the mean circulation on both the long-term and decadal time scale, and the represented inter-annual variability of intermediate and deep water mass formation processes in both the Eastern and Western sub-basins, finding that models agree with observations in correspondence of specific events, such as the 1992-1993 Eastern Mediterranean Transient, and the 2005-2006 event in the Gulf of Lion. Long

  5. Research through simulation. [simulators and research applications at Langley

    NASA Technical Reports Server (NTRS)

    Copeland, J. L. (Compiler)

    1982-01-01

    The design of the computer operating system at Langley Research Center allows for concurrent support of time-critical simulations and background analytical computing on the same machine. Signal path interconnections between computing hardware and flight simulation hardware is provided to allow up to six simulation programs to be in operation at one time. Capabilities and research applications are discussed for the: (1) differential maneuvering simulator; (2) visual motion simulator; (3) terminal configured vehicle simulator; (4) general aviation aircraft simulator; (5) general purpose fixed based simulator; (6) transport simulator; (7) digital fly by wire simulator; (8) general purpose fighter simulator; and (9) the roll-up cockpit. The visual landing display system and graphics display system are described and their simulator support applications are listed.

  6. Use of an extracorporeal circulation perfusion simulator: evaluation of its accuracy and repeatability.

    PubMed

    Tokumine, Asako; Momose, Naoki; Tomizawa, Yasuko

    2013-12-01

    Medical simulators have mainly been used as educational tools. They have been used to train technicians and to educate potential users about safety. We combined software for hybrid-type extracorporeal circulation simulation (ECCSIM) with a CPB-Workshop console. We evaluated the performance of ECCSIM, including its accuracy and repeatability, during simulated ECC. We performed a detailed evaluation of the synchronization of the software with the console and the function of the built-in valves. An S-III heart–lung machine was used for the open circuit. It included a venous reservoir, an oxygenator (RX-25), and an arterial filter. The tubes for venous drainage and the arterial line were connected directly to the ports of the console. The ECCSIM recorded the liquid level of the reservoir continuously. The valve in the console controlled the pressure load of the arterial line. The software made any adjustments necessary to both arterial pressure load and the venous drainage flow volume. No external flowmeters were necessary during simulation. We found the CPB-Workshop to be convenient, reliable, and sufficiently exact. It can be used to validate procedures by monitoring the controls and responses by using a combination of qualitative measures. PMID:24022821

  7. Simulation study of autoregulation responses of peripheral circulation to systemic pulsatility

    PubMed Central

    Aletti, Federico; Lanzarone, Ettore; Costantino, Maria Laura; Baselli, Giuseppe

    2009-01-01

    Background This simulation study investigated potential modulations of total peripheral resistance (TPR), due to distributed peripheral vascular activity, by means of a lumped model of the arterial tree and a non linear model of microcirculation, inclusive of local controls of blood flow and tissue-capillary fluid exchange. Results Numerical simulations of circulation were carried out to compute TPR under different conditions of blood flow pulsatility, and to extract the pressure-flow characteristics of the cardiovascular system. Simulations showed that TPR seen by the large arteries was increased in absence of pulsatility, while it decreased with an augmented harmonic content. This is a typically non linear effect due to the contribution of active, non linear autoregulation of the peripheral microvascular beds, which also generated a nonlinear relationship between arterial blood pressure and cardiac output. Conclusion This simulation study, though focused on a simple effect attaining TPR modulation due to pulsatility, suggests that non-linear autoregulation mechanisms cannot be overlooked while studying the integrated behavior of the global cardiovascular system, including the arterial tree and the peripheral vascular bed. PMID:19630959

  8. Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation.

    PubMed

    Qureshi, M Umar; Vaughan, Gareth D A; Sainsbury, Christopher; Johnson, Martin; Peskin, Charles S; Olufsen, Mette S; Hill, N A

    2014-10-01

    A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281-1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of 'large' arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the 'smaller' arteries and veins of radii ≥ 50 μm. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung. PMID:24610385

  9. 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

  10. Simulation of NOx emission in circulating fluidized beds burning low-grade fuels

    SciTech Connect

    Afsin Gungor

    2009-05-15

    Nitrogen oxides are a major environmental pollutant resulting from combustion. This paper presents a modeling study of pollutant NOx emission resulting from low-grade fuel combustion in a circulating fluidized bed. The simulation model accounts for the axial and radial distribution of NOx emission in a circulating fluidized bed (CFB). The model results are compared with and validated against experimental data both for small-size and industrial-size CFBs that use different types of low-grade fuels given in the literature. The present study proves that CFB combustion demonstrated by both experimental data and model predictions produces low and acceptable levels of NOx emissions resulting from the combustion of low-grade fuels. Developed model can also investigate the effects of different operational parameters on overall NOx emission. As a result of this investigation, both experimental data and model predictions show that NOx emission increases with the bed temperature but decreases with excess air if other parameters are kept unchanged. 37 refs., 5 figs., 5 tabs.

  11. Investigation of sludge re-circulating clarifiers design and optimization through numerical simulation.

    PubMed

    Davari, S; Lichayee, M J

    2003-01-01

    In steam thermal power plants (TPP) with open re-circulating wet cooling towers, elimination of water hardness and suspended solids (SS) is performed in clarifiers. Most of these clarifiers are of high efficiency sludge re-circulating type (SRC) with capacity between 500-1,500 m3/hr. Improper design and/or mal-operation of clarifiers in TPPs results in working conditions below design capacity or production of soft water with improper quality (hardness and S.S.). This causes accumulation of deposits in heat exchangers, condenser tubes, cooling and service water pipes and boiler tubes as well as increasing the ionic load of water at the demineralizing system inlet. It also increases the amount of chemical consumptions and produces more liquid and solid waste. In this regard, a software program for optimal design and simulation of SRCs has been developed. Then design parameters of existing SRCs in four TPPs in Iran were used as inputs to developed software program and resulting technical specifications were compared with existing ones. In some cases improper design was the main cause of poor outlet water quality. In order to achieve proper efficiency, further investigations were made to obtain control parameters as well as design parameters for both mal-designed and/or mal-operated SRCs. PMID:14753549

  12. Simulated strengthening of the Atlantic Meridional Overturning Circulation in response to abyssal ocean warming around Antarctica

    NASA Astrophysics Data System (ADS)

    Patara, L.; Boning, C. W.

    2013-12-01

    Studies of repeat hydrographic observations have revealed a conspicuous multi-decadal warming, and partly, freshening, of the frigid abyssal ocean waters originating from the fringes of the Antarctic continent. The warming and contraction of Antarctic Bottom Water (AABW) represents one of the most prominent signals of change in Earth's climate and accounts for a substantial fraction of the present global energy and sea level budgets. Here we present a set of ocean model experiments demonstrating that the ongoing loss of AABW also has important dynamical consequences for the large-scale meridional overturning circulation in the Atlantic Ocean. In conjunction with a slowdown of the bottom cell, we find that the upper cell of the Atlantic Meridional Overturning Circulation (AMOC) progressively strengthens in response to changes in density gradients in the deep South Atlantic. Changes in the AMOC are tightly connected to increased meridional heat transport and therefore have a strong influence on global and regional climate patterns in the North Atlantic. The simulations suggest that the AABW-induced strengthening of the AMOC is already extending into the North Atlantic, progressing at a rate of about 0.2 Sv per decade, implying that the process may need to be taken into account in projections of future North Atlantic climate.

  13. Available energy of symmetric circulations with application to the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Codoban, Sorin

    We present a theory of available energy for symmetric circulations of a rotating, stratified fluid. The theory is a generalization of the classical theory of available potential energy (APE), in that it accounts for both the momentum and the thermal constraints on the circulation. The generalization relies on the Hamiltonian structure of the conservative dynamics, although (as with classical APE) it still defines the energetics in a non-conservative framework. The energy budget is derived for the circulation transverse to a given balanced reference flow. For a simple example, it is shown that by including momentum constraints, the available energy of the transverse circulation to a symmetrically stable flow is zero, while the energetics of a mechanically driven symmetric circulation properly reflect its causality. The theory is then applied in the context of the primitive equations in spherical coordinates, to diagnose the available energy of the residual mean meridional circulation of the middle atmosphere. Both simulated fields from the Canadian Middle Atmosphere Model and the ERA-40 re-analysis data are used for diagnostic comparison. With the non-resting reference state constructed using the radiative equilibrium temperature the available energy diagnostic robustly identifies the circulation as being thermally damped and mechanically forced, in both the stratosphere and mesosphere, which agrees with its causality. The boundary flux term and the thermal forcing are both negative, with the mechanical forcing, due to deposition of momentum by the waves breaking in-situ, being identified as the driving agent; this agrees with the gyroscopic pumping mechanism as the driving process of the middle atmosphere meridional circulation. In contrast, with the resting (Lorenz-like) reference state the thermal forcing is seen as driving the circulation in the stratosphere (along with the boundary flux), with mechanical forcing being identified as a damping. In the mesosphere

  14. Incorporating circulation statistics in bias correction of GCM ensembles: hydrological application for the Rhine basin

    NASA Astrophysics Data System (ADS)

    Photiadou, Christiana; van den Hurk, Bart; van Delden, Aarnout; Weerts, Albrecht

    2016-01-01

    An adapted statistical bias correction method is introduced to incorporate circulation-dependence of the model precipitation bias, and its influence on estimated discharges for the Rhine basin is analyzed for a historical period. The bias correction method is tailored to time scales relevant to flooding events in the basin. Large-scale circulation patterns (CPs) are obtained through Maximum Covariance Analysis using reanalysis sea level pressure and high-resolution precipitation observations. A bias correction using these CPs is applied to winter and summer separately, acknowledging the seasonal variability of the circulation regimes in North Europe and their correlation with regional precipitation rates over the Rhine basin. Two different climate model ensemble outputs are explored: ESSENCE and CMIP5. The results of the CP-method are then compared to observations and uncorrected model outputs. Results from a simple bias correction based on a delta factor (NoCP-method) are also used for comparison. For both summer and winter, the CP-method offers a statistically significant improvement of precipitation statistics for subsets of data dominated by particular circulation regimes, demonstrating the circulation-dependence of the precipitation bias. Uncorrected, CP and NoCP corrected model outputs were used as forcing to a hydrological model to simulate river discharges. The CP-method leads to a larger improvement in simulated discharge in the Alpine area in winter than in summer due to a stronger dependence of Rhine precipitation on atmospheric circulation in winter. However, the NoCP-method, in comparison to the CP-method, improves the discharge estimations over the entire Rhine basin.

  15. Large eddy simulation model for wind-driven sea circulation in coastal areas

    NASA Astrophysics Data System (ADS)

    Petronio, A.; Roman, F.; Nasello, C.; Armenio, V.

    2013-12-01

    In the present paper a state-of-the-art large eddy simulation model (LES-COAST), suited for the analysis of water circulation and mixing in closed or semi-closed areas, is presented and applied to the study of the hydrodynamic characteristics of the Muggia bay, the industrial harbor of the city of Trieste, Italy. The model solves the non-hydrostatic, unsteady Navier-Stokes equations, under the Boussinesq approximation for temperature and salinity buoyancy effects, using a novel, two-eddy viscosity Smagorinsky model for the closure of the subgrid-scale momentum fluxes. The model employs: a simple and effective technique to take into account wind-stress inhomogeneity related to the blocking effect of emerged structures, which, in turn, can drive local-scale, short-term pollutant dispersion; a new nesting procedure to reconstruct instantaneous, turbulent velocity components, temperature and salinity at the open boundaries of the domain using data coming from large-scale circulation models (LCM). Validation tests have shown that the model reproduces field measurement satisfactorily. The analysis of water circulation and mixing in the Muggia bay has been carried out under three typical breeze conditions. Water circulation has been shown to behave as in typical semi-closed basins, with an upper layer moving along the wind direction (apart from the anti-cyclonic veering associated with the Coriolis force) and a bottom layer, thicker and slower than the upper one, moving along the opposite direction. The study has shown that water vertical mixing in the bay is inhibited by a large level of stable stratification, mainly associated with vertical variation in salinity and, to a minor extent, with temperature variation along the water column. More intense mixing, quantified by sub-critical values of the gradient Richardson number, is present in near-coastal regions where upwelling/downwelling phenomena occur. The analysis of instantaneous fields has detected the presence of

  16. 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

  17. Application of Circulation Control Technology to Airframe Noise Reduction

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Sankar, L. N.; Englar, R. J.; Munro, Scott E.; Li, Yi; Gaeta, R. J.

    2003-01-01

    This report is a summary of the work performed by Georgia Tech Research Institute (GTRI) under NASA Langley Grant NAG-1-2146, which was awarded as a part of NASA's Breakthrough Innovative Technologies (BIT) initiative. This was a three-year program, with a one-year no-cost extension. Each year's study has been an integrated effort consisting of computational fluid dynamics, experimental aerodynamics, and detailed noise and flow measurements. Year I effort examined the feasibility of reducing airframe noise by replacing the conventional wing systems with a Circulation Control Wing (CCW), where steady blowing was used through the trailing edge of the wing over a Coanda surface. It was shown that the wing lift increases with CCW blowing and indeed for the same lift, a CCW wing was shown to produce less noise. Year 2 effort dealt with a similar study on the role of pulsed blowing on airframe noise. The main objective of this portion of the study was to assess whether pulse blowing from the trailing edge of a CCW resulted in more, less, or the same amount of radiated noise to the farfield. Results show that a reduction in farfield noise of up to 5 dB is measured when pulse flow is compared with steady flow for an equivalent lift configuration. This reduction is in the spectral region associated with the trailing edge jet noise. This result is due to the unique advantage that pulsed flow has over steady flow. For a range of frequencies, more lift is experienced with the same mass flow as the steady case. Thus, for an equivalent lift and slot height, the pulsed system can operate at lower jet velocities, and hence lower jet noise. The computational analysis showed that for a given time-averaged mass flow rate, pulsed jets give a higher value of C(sub l) and a higher L/D than equivalent steady jets. This benefit is attributable to higher instantaneous jet velocities, and higher instantaneous C(sub mu) values for the pulsed jet. Pulsed jet benefits increase at higher

  18. Natural circulation in a VVER reactor geometry: Experiments with the PACTEL facility and Cathare simulations

    SciTech Connect

    Raussi, P.; Kainulainen, S.; Kouhia, J.

    1995-09-01

    There are some 40 reactors based on the VVER design in use. Database available for computer code assessment for VVER reactors is rather limited. Experiments were conducted to study natural circulation behaviour in the PACTEL facility, a medium-scale integral test loop patterned after VVER pressurized water reactors. Flow behaviour over a range of coolant inventories was studied with a small-break experiment. In the small-break experiments, flow stagnation and system repressurization were observed when the water level in the upper plenum fell below the entrances to the hot legs. The cause was attributed to the hot leg loop seals, which are a unique feature of the VVER geometry. At low primary inventories, core cooling was achieved through the boiler-condenser mode. The experiment was simulated using French thermalhydraulic system code CATHARE.

  19. Simulating Titan’s tropospheric circulation with the Portable University Model of the Atmosphere

    NASA Astrophysics Data System (ADS)

    Grieger, B.; Segschneider, J.; Keller, H. U.; Rodin, A. V.; Lunkeit, F.; Kirk, E.; Fraedrich, K.

    2004-01-01

    The Portable University Model of the Atmosphere (PUMA) is a general circulation model of intermediate complexity. In the model setup used herein, the dynamics is driven by restoration to a prescribed temperature field. Given an observed three-dimensional field of restoration temperatures, the feedback of aerosol distribution to the radiation scheme and hence to the dynamics is excluded from calculations. PUMA is adapted to Titan conditions and used to carry out a series of experiments with temperature fields based on radio occultation and infrared spectroscopy measurements taken by Voyager 1 in 1980. The resultant winds are prograde with maximum wind speeds of about 14 m/s in the troposphere. This simulation demonstrates capabilities of a restricted complexity model and provides a contribution to the prediction of the descent trajectory of the Huygens lander in January 2005.

  20. Simulation Study of Effects of Solar Irradiance and Sea Surface Temperature on Monsoons and Global Circulation

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Walker, G. K.; Mehta, V.; Lau, W. K.-M.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    A recent version of the GEOS 2 GCM was used to isolate the roles of the annual cycles of solar irradiation and/or sea-surface temperatures (SSTs) on the simulated circulation and rainfall. Four 4-year long integrations were generated with the GCM. The first integration, called Control Case, used daily-interpolated SSTs from a 30 year monthly SST climatology that was obtained from the analyzed SST-data, while the solar irradiation at the top of the atmosphere was calculated normally at hourly intervals. The next two cases prescribed the SSTs or the incoming solar irradiance at the top of the atmosphere at their annual mean values, respectively while everything else was kept the same as in the Control Case. In this way the influence of the annual cycles of both external forcings was isolated.

  1. 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

  2. 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

  3. Martian atmospheric gravity waves simulated by a high-resolution general circulation model

    NASA Astrophysics Data System (ADS)

    Kuroda, Takeshi; Yiǧit, Erdal; Medvedev, Alexander S.; Hartogh, Paul

    2016-07-01

    Gravity waves (GWs) significantly affect temperature and wind fields in the Martian middle and upper atmosphere. They are also one of the observational targets of the MAVEN mission. We report on the first simulations with a high-resolution general circulation model (GCM) and present a global distributions of small-scale GWs in the Martian atmosphere. The simulated GW-induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km. For the northern winter solstice, the model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of GWs: mountainous regions and the meandering winter polar jet. Orographic GWs are filtered upon propagating upward, and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities. Wave fluxes are directed mainly against the local wind. GW dissipation in the upper mesosphere generates a body force per unit mass of tens of m s^{-1} per Martian solar day (sol^{-1}), which tends to close the simulated jets. The results represent a realistic surrogate for missing observations, which can be used for constraining GW parameterizations and validating GCMs.

  4. Commercial application of rainfall simulation

    NASA Astrophysics Data System (ADS)

    Loch, Rob J.

    2010-05-01

    Landloch Pty Ltd is a commercial consulting firm, providing advice on a range of land management issues to the mining and construction industries in Australia. As part of the company's day-to-day operations, rainfall simulation is used to assess material erodibility and to investigate a range of site attributes. (Landloch does carry out research projects, though such are not its core business.) When treated as an everyday working tool, several aspects of rainfall simulation practice are distinctively modified. Firstly, the equipment used is regularly maintained, and regularly upgraded with a primary focus on ease, safety, and efficiency of use and on reliability of function. As well, trained and experienced technical support is considered essential. Landloch's chief technician has over 10 years experience in running rainfall simulators at locations across Australia and in Africa and the Pacific. Secondly, the specific experimental conditions established for each set of rainfall simulator runs are carefully considered to ensure that they accurately represent the field conditions to which the data will be subsequently applied. Considerations here include: • wetting and drying cycles to ensure material consolidation and/or cementation if appropriate; • careful attention to water quality if dealing with clay soils or with amendments such as gypsum; • strong focus on ensuring that the erosion processes considered are those of greatest importance to the field situation of concern; and • detailed description of both material and plot properties, to increase the potential for data to be applicable to a wider range of projects and investigations. Other important company procedures include: • For each project, the scientist or engineer responsible for analysing and reporting rainfall simulator data is present during the running of all field plots, as it is essential that they be aware of any specific conditions that may have developed when the plots were subjected

  5. An Active Flow Circulation Controlled Flap Concept for General Aviation Aircraft Applications

    NASA Technical Reports Server (NTRS)

    Jones, Gregory S.; Viken, Sally A.; Washburn, Anthony E.; Jenkins, Luther N.; Cagle, C. Mark

    2002-01-01

    A recent focus on revolutionary aerodynamic concepts has highlighted the technology needs of general aviation and personal aircraft. New and stringent restrictions on these types of aircraft have placed high demands on aerodynamic performance, noise, and environmental issues. Improved high lift performance of these aircraft can lead to slower takeoff and landing speeds that can be related to reduced noise and crash survivability issues. Circulation Control technologies have been around for 65 years, yet have been avoided due to trade offs of mass flow, pitching moment, perceived noise etc. The need to improve the circulation control technology for general aviation and personal air-vehicle applications is the focus of this paper. This report will describe the development of a 2-D General Aviation Circulation Control (GACC) wing concept that utilizes a pulsed pneumatic flap.

  6. New Insights about Meridional Circulation Dynamics from 3D MHD Global Simulations of Solar Convection and Dynamo Action

    NASA Astrophysics Data System (ADS)

    Passos, D.; Charbonneau, P.; Miesch, M. S.

    2016-04-01

    The solar meridional circulation is a "slow", large scale flow that transports magnetic field and plasma throughout the convection zone in the (r,θ) plane and plays a crucial role in controlling the magnetic cycle solutions presented by flux transport dynamo models. Observations indicate that this flow speed varies in anti-phase with the solar cycle at the solar surface. A possible explanation for the source of this variation is based on the fact that inflows into active regions alter the global surface pattern of the meridional circulation. In this work we examine the meridional circulation profile that emerges from a 3D global simulation of the solar convection zone, and its associated dynamics. We find that at the bottom of the convection zone, in the region where the toroidal magnetic field accumulates, the meridional circulation is highly modulated through the action of a magnetic torques and thus provides evidence for a new mechanism to explain the observed cyclic variations.

  7. Numerical Studies on an Active Flow Circulation Controlled Flap Concept for Aeronautical Applications

    NASA Astrophysics Data System (ADS)

    Zacharos, Athanasios; Kontis, Konstantinos

    Four different circulation controlled airfoils have been numerically simulated. The baseline airfoil was a 17% thick supercritical airfoil. Different blowing rates have been examined by adjusting the slot height and blowing velocity. A number of turbulence models were employed, these were: Spalart-Allmaras, standard κ ɛ, realizable κ ɛ, SST κ ω and Reynolds stress model. The results from the numerical simulations were compared with experimental data at zero angle of attack. The solutions indicated that at momentum coefficients, Cμ=0.1 or greater, all isotropic turbulence models failed to capture the physics of the circulation control problem. The Reynolds stress model captured successfully the physics at Cμ=0.1. At greater values of momentum coefficient, the Reynolds stress model also failed to predict the experimentally measured lift coefficients because the jet remained attached to the surface of the airfoil. The Spalart-Allmaras model consistently predicted the right trend for lift variation with Cμ in all cases tested.

  8. Longitudinal biases in the Seychelles Dome simulated by 35 ocean-atmosphere coupled general circulation models

    NASA Astrophysics Data System (ADS)

    Nagura, Motoki; Sasaki, Wataru; Tozuka, Tomoki; Luo, Jing-Jia; Behera, Swadhin K.; Yamagata, Toshio

    2013-02-01

    Seychelles Dome refers to the shallow climatological thermocline in the southwestern Indian Ocean, where ocean wave dynamics efficiently affect sea surface temperature, allowing sea surface temperature anomalies to be predicted up to 1-2 years in advance. Accurate reproduction of the dome by ocean-atmosphere coupled general circulation models (CGCMs) is essential for successful seasonal predictions in the Indian Ocean. This study examines the Seychelles Dome as simulated by 35 CGCMs, including models used in phase five of the Coupled Model Intercomparison Project (CMIP5). Among the 35 CGCMs, 14 models erroneously produce an upwelling dome in the eastern half of the basin whereas the observed Seychelles Dome is located in the southwestern tropical Indian Ocean. The annual mean Ekman pumping velocity in these models is found to be almost zero in the southern off-equatorial region. This result is inconsistent with observations, in which Ekman upwelling acts as the main cause of the Seychelles Dome. In the models reproducing an eastward-displaced dome, easterly biases are prominent along the equator in boreal summer and fall, which result in shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and a spurious upwelling dome in the region. Compared to the CMIP3 models, the CMIP5 models are even worse in simulating the dome longitudes.

  9. Simulating the impact of the large-scale circulation on the 2-m temperature and precipitation climatology

    EPA Science Inventory

    The impact of the simulated large-scale atmospheric circulation on the regional climate is examined using the Weather Research and Forecasting (WRF) model as a regional climate model. The purpose is to understand the potential need for interior grid nudging for dynamical downscal...

  10. Internal versus SST-forced atmospheric variability as simulated by an atmospheric general circulation model

    SciTech Connect

    Harzallah, A.; Sadourny, R.

    1995-03-01

    The variability of atmospheric flow is analyzed by separating it into an internal part due to atmospheric dynamics only and an external (or forced) part due to the variability of sea surface temperature forcing. The two modes of variability are identified by performing an ensemble of seven independent long-term simulations of the atmospheric response to observed SST (1970-1988) with the LMD atmospheric general circulation model. The forced variability is defined from the analysis of the ensemble mean and the internal variability from the analysis of deviations from the ensemble mean. Emphasis is put on interannual variability of sea level pressure and 500-hPa geopotential height for the Northern Hemisphere winter. In view of the large systematic errors related to the relatively small number of realizations, unbiased variance estimators have been developed. Although statistical significance is not reached in some extratropical regions, large significant extratropical responses are found at the North Pacific-Alaska sector for SLP and over western Canada and the Aleutians for 500-hPa geopotential height. The influence of SST variations on internal variability is also examined by using a 7-year simulation using the climatological SST seasonal cycle. It is found that interannual SST changes strongly influence the geographical distribution of internal variability; in particular, it tends to increase it over oceans. EOF decompositions, showing that the model realistically simulates the leading observed variability modes. The geographical structure of internal variability patterns is found to be similar to that of total variability, although similar modes tend to evolve rather differently in time. The zonally symmetric seesaw dominates the internal variability for both observed and climatologically prescribed SST. 46 refs., 15 figs., 3 tabs.

  11. Future applications of simulators in process control

    SciTech Connect

    Ruppel, F.; Wysor, W.

    1997-03-21

    Future applications of simulators in process control will see activities with high return on investment in areas such as concurrent engineering, hardware-in-the-loop controller testing, process fault detection, and Internet-retrievable simulation models and tools. These applications are based on advancing technology in the field of simulation technology. In this paper, the advancing technology will be reviewed, and projections to future uses of simulators in process control will be made.

  12. Baroclinic internal wave energy distribution in the Baltic Sea derived from 45 years of circulation simulations

    NASA Astrophysics Data System (ADS)

    Rybin, Artem; Soomere, Tarmo; Kurkina, Oxana; Kurkin, Andrey; Rouvinskaya, Ekaterina; Markus Meier, H. E.

    2016-04-01

    Internal waves and internal tides are an essential component of the functioning of stratified shelf seas. They carry substantial amounts of energy through the water masses, drive key hydrophysical processes such as mixing and overturning and support the functioning of marine ecosystem in many ways. Their particular impact becomes evident near and at the bottom where they often create substantial loads to engineering structures and exert a wide range of impacts on the bottom sediments and evolution of the seabed. We analyse several properties of spatio-temporal distributions of energy of relatively long-period large-scale internal wave motions in the Baltic Sea. The analysis is based on numerically simulated pycnocline variations that are extracted from the hydrographic data calculated by the Rossby Centre Ocean circulation model (RCO) for the entire Baltic Sea for 1961-2005. This model has a horizontal resolution of 2 nautical miles and uses 41 vertical layers with a thickness between 3 m close to the surface and 12 m in 250 m depth. The model is forced with atmospheric data derived from the ERA-40 re-analysis using a regional atmosphere model with a horizontal resolution of 25 km. It also accounts for river inflow and water exchange through the Danish Straits. See (Meier, H.E.M., Höglund, A., 2013. Studying the Baltic Sea circulation with Eulerian tracers, in Soomere, T., Quak, E., eds., Preventive Methods for Coastal Protection, Springer, Cham, Heidelberg, 101-130) for a detailed description of the model and its forcing. The resolution of the model output used in this study (once in 6 hours) is sufficient for estimates of spectral amplitudes of the displacements of isopycnal surfaces with a typical period of 2-12 days. We provide the analysis of kinetic and potential energy of motions with these periods. The resulting maps of the maxima of energy and spatial distributions of near-bottom velocities have been evaluated for the entire simulation interval of 45

  13. An analysis of the synoptic and climatological applicability of circulation type classifications for Ireland

    NASA Astrophysics Data System (ADS)

    Broderick, Ciaran; Fealy, Rowan

    2013-04-01

    Circulation type classifications (CTCs) compiled as part of the COST733 Action, entitled 'Harmonisation and Application of Weather Type Classifications for European Regions', are examined for their synoptic and climatological applicability to Ireland based on their ability to characterise surface temperature and precipitation. In all 16 different objective classification schemes, representative of four different methodological approaches to circulation typing (optimization algorithms, threshold based methods, eigenvector techniques and leader algorithms) are considered. Several statistical metrics which variously quantify the ability of CTCs to discretize daily data into well-defined homogeneous groups are used to evaluate and compare different approaches to synoptic typing. The records from 14 meteorological stations located across the island of Ireland are used in the study. The results indicate that while it was not possible to identify a single optimum classification or approach to circulation typing - conditional on the location and surface variables considered - a number of general assertions regarding the performance of different schemes can be made. The findings for surface temperature indicate that that those classifications based on predefined thresholds (e.g. Litynski, GrossWetterTypes and original Lamb Weather Type) perform well, as do the Kruizinga and Lund classification schemes. Similarly for precipitation predefined type classifications return high skill scores, as do those classifications derived using some optimization procedure (e.g. SANDRA, Self Organizing Maps and K-Means clustering). For both temperature and precipitation the results generally indicate that the classifications perform best for the winter season - reflecting the closer coupling between large-scale circulation and surface conditions during this period. In contrast to the findings for temperature, spatial patterns in the performance of classifications were more evident for

  14. Simulation of Indian Monsoon Variability in the Medieval Warm Period using ECHAM5 General Circulation Model

    NASA Astrophysics Data System (ADS)

    Polanski, Stefan; Fallah, Bijan; Prasad, Sushma; Cubasch, Ulrich

    2013-04-01

    Within the framework of the DFG research group HIMPAC, the general circulation model ECHAM5 has been used to simulate the Indian monsoon and its variability during the Medieval Warm Period (MWP; 900-1100 AD) and for recent climate (REC; 1800-2000 AD). The focus is on the analysis of internal and external drivers leading to extreme rainfall events over India from interannual to multidecadal time scale. An evaluation of spatio-temporal monsoon patterns with present-day observation data is in agreement with other state-of-the-art monsoon modeling studies. The simulated monsoon intensity on multidecadal time scale is weakened (enhanced) in summer (winter) due to colder (warmer) SSTs in the Indian Ocean. Variations in solar insolation are the main drivers for these SST anomalies, verified by very high temporal correlations between Total Solar Irradiance and All-India-Monsoon-Rainfall in summer monsoon months (-0.95). The external solar forcing is coupled and overlain by internal climate modes of the Ocean (ENSO and IOD) with asynchronous intensities and lengths of periods. In addition, the model simulations have been compared with a relative moisture index derived from paleoclimatic reconstructions based on various proxies and archives in India (Anoop et al., 2012 (under revision); Bhattacharya et al., 2007; Chauhan et al., 2000; Denniston et al., 2000; Ely et al., 1999; Kar et al., 2002; Ponton et al., 2012; Prasad et al., 2012 (under revision)). In this context, the reconstructed climate of the well-dated Lonar record in Central India has been highlighted and evaluated the first time (Anoop et al., 2012 (under revision); Prasad et al., 2012 (under revision)). Particularly with regard to the long continuously chronology of the last 11000 years, the Lonar site gives a unique possibility for a comparison of long-term climate time series. The simulated relative annual rainfall anomalies ("MWP" minus "REC") are in agreement with the reconstructed moisture index. The dry

  15. A Variable Resolution Stretched Grid General Circulation Model: Regional Climate Simulation

    NASA Technical Reports Server (NTRS)

    Fox-Rabinovitz, Michael S.; Takacs, Lawrence L.; Govindaraju, Ravi C.; Suarez, Max J.

    2000-01-01

    The development of and results obtained with a variable resolution stretched-grid GCM for the regional climate simulation mode, are presented. A global variable resolution stretched- grid used in the study has enhanced horizontal resolution over the U.S. as the area of interest The stretched-grid approach is an ideal tool for representing regional to global scale interaction& It is an alternative to the widely used nested grid approach introduced over a decade ago as a pioneering step in regional climate modeling. The major results of the study are presented for the successful stretched-grid GCM simulation of the anomalous climate event of the 1988 U.S. summer drought- The straightforward (with no updates) two month simulation is performed with 60 km regional resolution- The major drought fields, patterns and characteristics such as the time averaged 500 hPa heights precipitation and the low level jet over the drought area. appear to be close to the verifying analyses for the stretched-grid simulation- In other words, the stretched-grid GCM provides an efficient down-scaling over the area of interest with enhanced horizontal resolution. It is also shown that the GCM skill is sustained throughout the simulation extended to one year. The developed and tested in a simulation mode stretched-grid GCM is a viable tool for regional and subregional climate studies and applications.

  16. Inertance estimation in a lumped-parameter hydraulic simulator of human circulation.

    PubMed

    Lanzarone, Ettore; Ruggeri, Fabrizio

    2013-06-01

    Pulsatile mock loop systems are largely used to investigate the cardiovascular system in vitro. They consist of a pump, which replicates the heart, coupled with a lumped-parameter hydraulic afterload, which simulates vasculature. An accurate dimensioning of components is required for a reliable mimicking of the physiopathological behavior of the system. However, it is not possible to create a component for the afterload inertance, and inertance contributions are present in the entire circuit. Hence, in the literature, inertance is neglected or qualitatively evaluated. In this paper, we propose two quantitative methods (Maximum-likelihood estimation (MLE) and Bayesian estimation) for estimating afterload inertance based on observed pressure and flow waveforms. These methods are also applied to a real mock loop system. Results show that the system has an inertance comparable with the literature reference value of the entire systemic circulation, and that the expected variations over inlet average flow and pulse frequency are in general confirmed. Comparing the methods, the Bayesian approach results in higher and more stable estimations than the classical MLE. PMID:23699724

  17. Large-eddy simulations of a turbulent Coanda jet on a circulation control airfoil

    NASA Astrophysics Data System (ADS)

    Nishino, Takafumi; Hahn, Seonghyeon; Shariff, Karim

    2010-12-01

    Large-eddy simulations are performed of a turbulent Coanda jet separating from a rounded trailing edge of a simplified circulation control airfoil model. The freestream Reynolds number based on the airfoil chord is 0.49×106, the jet Reynolds number based on the jet slot height is 4470, and the ratio of the peak jet velocity to the freestream velocity is 3.96. Three different grid resolutions are used to show that their effect is very small on the mean surface pressure distribution, which agrees very well with experiments, as well as on the mean velocity profiles over the Coanda surface. It is observed that the Coanda jet becomes fully turbulent just downstream of the jet exit, accompanied by asymmetric alternating vortex shedding behind a thin (but blunt) jet blade splitting the jet and the external flow. A number of "backward-tilted" hairpin vortices (i.e., the head of each hairpin being located upstream of the legs) are observed around the outer edge of the jet over the Coanda surface. These hairpins create strong upwash between the legs and weak downwash around them, contributing to turbulent mixing of the high-momentum jet below the hairpins and the low-momentum external flow above them. The probability density distribution of velocity fluctuations is shown to be highly asymmetric in this region, consistent with the observation that the hairpin vortices create strong upwash and weak downwash. Turbulent structures inside the jet, its spreading rate, and self-similarity are also discussed.

  18. Acute effects of a large bolide impact simulated by a global atmospheric circulation model

    NASA Technical Reports Server (NTRS)

    Thompson, Starley L.; Crutzen, P. J.

    1988-01-01

    The goal is to use a global three-dimensional atmospheric circulation model developed for studies of atmospheric effects of nuclear war to examine the time evolution of atmospheric effects from a large bolide impact. The model allows for dust and NOx injection, atmospheric transport by winds, removal by precipitation, radiative transfer effects, stratospheric ozone chemistry, and nitric acid formation and deposition on a simulated Earth having realistic geography. Researchers assume a modest 2 km-diameter impactor of the type that could have formed the 32 km-diameter impact structure found near Manson, Iowa and dated at roughly 66 Ma. Such an impact would have created on the order of 5 x 10 to the 10th power metric tons of atmospheric dust (about 0.01 g cm(-2) if spread globally) and 1 x 10 to the 37th power molecules of NO, or two orders of magnitude more stratospheric NO than might be produced in a large nuclear war. Researchers ignore potential injections of CO2 and wildfire smoke, and assume the direct heating of the atmosphere by impact ejecta on a regional scale is not large compared to absorption of solar energy by dust. Researchers assume an impact site at 45 N in the interior of present day North America.

  19. Mechanisms for decadal scale variability in a simulated Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Medhaug, I.; Langehaug, H. R.; Eldevik, T.; Furevik, T.; Bentsen, M.

    2012-07-01

    Variability in the Atlantic Meridional Overturning Circulation (AMOC) has been analysed using a 600-year pre-industrial control simulation with the Bergen Climate Model. The typical AMOC variability has amplitudes of 1 Sverdrup (1 Sv = 106 m3 s-1) and time scales of 40-70 years. The model is reproducing the observed dense water formation regions and has very realistic ocean transports and water mass distributions. The dense water produced in the Labrador Sea (1/3) and in the Nordic Seas, including the water entrained into the dense overflows across the Greenland-Scotland Ridge (GSR; 2/3), are the sources of North Atlantic Deep Water (NADW) forming the lower limb of the AMOC's northern overturning. The variability in the Labrador Sea and the Nordic Seas convection is driven by decadal scale air-sea fluxes in the convective region that can be related to opposite phases of the North Atlantic Oscillation. The Labrador Sea convection is directly linked to the variability in AMOC. Linkages between convection and water mass transformation in the Nordic Seas are more indirect. The Scandinavian Pattern, the third mode of atmospheric variability in the North Atlantic, is a driver of the ocean's poleward heat transport (PHT), the overall constraint on northern water mass transformation. Increased PHT is both associated with an increased water mass exchange across the GSR, and a stronger AMOC.

  20. General circulation model simulations of recent cooling in the east-central United States

    NASA Astrophysics Data System (ADS)

    Robinson, Walter A.; Reudy, Reto; Hansen, James E.

    2002-12-01

    In ensembles of retrospective general circulation model (GCM) simulations, surface temperatures in the east-central United States cool between 1951 and 1997. This cooling, which is broadly consistent with observed surface temperatures, is present in GCM experiments driven by observed time varying sea-surface temperatures (SSTs) in the tropical Pacific, whether or not increasing greenhouse gases and other time varying climate forcings are included. Here we focus on ensembles with fixed radiative forcing and with observed varying SST in different regions. In these experiments the trend and variability in east-central U.S. surface temperatures are tied to tropical Pacific SSTs. Warm tropical Pacific SSTs cool U.S. temperatures by diminishing solar heating through an increase in cloud cover. These associations are embedded within a year-round response to warm tropical Pacific SST that features tropospheric warming throughout the tropics and regions of tropospheric cooling in midlatitudes. Precipitable water vapor over the Gulf of Mexico and the Caribbean and the tropospheric thermal gradient across the Gulf Coast of the United States increase when the tropical Pacific is warm. In observations, recent warming in the tropical Pacific is also associated with increased precipitable water over the southeast United States. The observed cooling in the east-central United States, relative to the rest of the globe, is accompanied by increased cloud cover, though year-to-year variations in cloud cover, U.S. surface temperatures, and tropical Pacific SST are less tightly coupled in observations than in the GCM.

  1. Impacts of soil moisture content on simulated mesoscale circulations during the summer over eastern Spain

    NASA Astrophysics Data System (ADS)

    Gómez, I.; Caselles, V.; Estrela, M. J.

    2015-10-01

    The Regional Atmospheric Modeling System (RAMS) version 6.0 has been used to investigate the impact and influence of initial soil moisture distributions on mesoscale circulations. To do this, two different events have been selected from the 2011 summer season: one at the beginning of the season (June) and the other one at the end of the season (August). For each of these mesoscale frameworks a total of five distinct simulations were performed varying the initial soil moisture content: a control run and four additional sensitivity tests. The control run, corresponding to a low soil moisture content, is the one used within the real-time weather forecasting system implemented in the Valencia Region. In the corresponding sensitivity simulations this low value has been progressively increased in different steps until the original soil moisture content doubled. It has been found that high soil moisture is associated with colder near-surface temperature, a moister relative humidity and a slightly lower near-surface wind speed, whereas a drier soil resulted in a dryer relative humidity, warmer temperature and a slight low-level wind. In general, the highest soil moisture contents are required to reproduce the near-surface daily cycles of temperature and relative humidity through higher values of latent heat flux and lower values of sensible heat flux. In this regard, moistening the soil improves the previous results obtained using the RAMS configuration used within the operational forecasting system. However, the wind speed is not quite sensitive to changes in the soil moisture content over flatter terrain. Finally, although a warming and dryer mixing layer is obtained with the lowest soil moisture content, the mixing layer height remains practically unchanged when using the distinct configurations over flat terrain. These differences are enhanced over more complex terrain.

  2. Investigation of wellbore cooling by circulation and fluid penetration into the formation using a wellbore thermal simulator computer code

    SciTech Connect

    Duda, L.E.

    1987-01-01

    The high temperatures of geothermal wells present severe problems for drilling, logging, and developing these reservoirs. Cooling the wellbore is perhaps the most common method to solve these problems. However, it is usually not clear what may be the most effective wellbore cooling mechanism for a given well. In this paper, wellbore cooling by the use of circulation or by fluid injection into the surrounding rock is investigated using a wellbore thermal simulator computer code. Short circulation times offer no prolonged cooling of the wellbore, but long circulation times (greater than ten or twenty days) greatly reduce the warming rate after shut-in. The dependence of the warming rate on the penetration distance of cooler temperatures into the rock formation (as by fluid injection) is investigated. Penetration distances of greater than 0.6 m appear to offer a substantial reduction in the warming rate. Several plots are shown which demonstrate these effects.

  3. 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

  4. Synoptic-climatological applicability of classifications of circulation patterns from the COST733 collection

    NASA Astrophysics Data System (ADS)

    Huth, Radan; Cahynová, Monika

    2010-05-01

    The synoptic-climatological applicability of a classification of circulation patterns is defined as its ability to stratify surface climate elements. We analyze a large number of classifications of circulation patterns that have been produced and collected within the COST733 Action "Harmonization and Applications of Weather Types Classifications for European Regions" for 12 European domains as to their ability to stratify temperature and precipitation across Europe. The degree of stratification is quantified by conducting the Kolmogorov-Smirnov test between the distribution conditioned by a particular circulation type and the unconditional distribution. As the climate data, station series from the ECA&D database and gridded dataset produced in the ENSEMBLES project have been used. The results are sensitive to the number of classes (classifications with a lower number of classes tending to yield a better stratification) and depend on season. Although the overall ‘best' method (or a group of optimum methods) cannot be identified, methods with generally a better and worse performance can be determined. The participation of the Czech Republic in the COST733 Action is supported by the Ministry of Education, Youth, and Sports of the Czech Republic under contract OC115. Support from the Grant Agency of the Czech Academy of Sciences, project A300420805, is also acknowledged.

  5. Application of data to piloted simulators

    NASA Technical Reports Server (NTRS)

    Bray, Richard S.

    1987-01-01

    The application of a further developed analytical model and JAWS data to a piloted simulator is addressed. The Ames simulator provides a facility for the development of piloting procedures, and for the selection of training scenarios. The system is operational with the new wind shear models and comprehensive data output. The use of these models with the simulator is dicussed in detail.

  6. Effects of Solar Particle Event-Like Proton Radiation and/or Simulated Microgravity on Circulating Mouse Blood Cells.

    PubMed

    Romero-Weaver, Ana L; Lin, Liyong; Carabe-Fernandez, Alejandro; Kennedy, Ann R

    2014-08-01

    Astronauts traveling in space missions outside of low Earth orbit will be exposed for longer times to a microgravity environment. In addition, the increased travel time involved in exploration class missions will result in an increased risk of exposure to significant doses of solar particle event (SPE) radiation. Both conditions could significantly affect the number of circulating blood cells. Therefore, it is critical to determine the combined effects of exposure to both microgravity and SPE radiation. The purpose of the present study was to assess these risks by evaluating the effects of SPE-like proton radiation and/or microgravity, as simulated with the hindlimb unloading (HU) system, on circulating blood cells using mouse as a model system. The results indicate that exposure to HU alone caused minimal or no significant changes in mouse circulating blood cell numbers. The exposure of mice to SPE-like proton radiation with or without HU treatment caused a significant decrease in the number of circulating lymphocytes, granulocytes and platelets. The reduced numbers of circulating lymphocytes, granulocytes, and platelets, resulting from the SPE-like proton radiation exposure, with or without HU treatment, in mice suggest that astronauts participating in exploration class missions may be at greater risk of developing infections and thrombotic diseases; thus, countermeasures may be necessary for these biological endpoints. PMID:25360441

  7. Effects of Solar Particle Event-Like Proton Radiation and/or Simulated Microgravity on Circulating Mouse Blood Cells

    PubMed Central

    Romero-Weaver, Ana L.; Lin, Liyong; Carabe-Fernandez, Alejandro; Kennedy, Ann R.

    2014-01-01

    Astronauts traveling in space missions outside of low Earth orbit will be exposed for longer times to a microgravity environment. In addition, the increased travel time involved in exploration class missions will result in an increased risk of exposure to significant doses of solar particle event (SPE) radiation. Both conditions could significantly affect the number of circulating blood cells. Therefore, it is critical to determine the combined effects of exposure to both microgravity and SPE radiation. The purpose of the present study was to assess these risks by evaluating the effects of SPE-like proton radiation and/or microgravity, as simulated with the hindlimb unloading (HU) system, on circulating blood cells using mouse as a model system. The results indicate that exposure to HU alone caused minimal or no significant changes in mouse circulating blood cell numbers. The exposure of mice to SPE-like proton radiation with or without HU treatment caused a significant decrease in the number of circulating lymphocytes, granulocytes and platelets. The reduced numbers of circulating lymphocytes, granulocytes, and platelets, resulting from the SPE-like proton radiation exposure, with or without HU treatment, in mice suggest that astronauts participating in exploration class missions may be at greater risk of developing infections and thrombotic diseases; thus, countermeasures may be necessary for these biological endpoints. PMID:25360441

  8. Application of Molded Interconnect Device technology to the realization of a self-biased circulator

    NASA Astrophysics Data System (ADS)

    Laur, Vincent; Mattei, Jean-Luc; Vérissimo, Grégory; Queffelec, Patrick; Lebourgeois, Richard; Ganne, Jean-Pierre

    2016-04-01

    This paper describes the first electromagnetic characterization of a self-biased circulator in molded interconnect device (MID) technology. The circulator was designed using a 3D full-wave commercial simulator. It consists of microstrip access lines connected to a Y-junction in Substrate Integrated Waveguide (SIW) technology. Unlike classical technologies, the SIW Y-junction was not fabricated using metallic vias but by a Laser Direct Structuring (LDS) technique. A molded Cyclo-Olefin Polymer (COP) was used as a substrate and 3D metallized. The microwave properties of LDS-compatible COP are not well known so we investigated them through the use of cavity-perturbation and rectangular waveguide characterization methods. The device was then machined to insert a pre-oriented strontium hexaferrite puck doped with cobalt and lanthanum (Sr0,7La0,3Fe11,7Co0,3O19). The characteristics of the MID circulator were assessed between 28 and 32 GHz. Without magnets, insertion losses of 3.32 dB were measured at 30.7 GHz. At the same frequency, an isolation level of 13.89 dB and return losses of 19.89 dB were observed. These measurements demonstrate for the first time the high potential of MID technology for the realization of low-cost non-reciprocal devices.

  9. WHTSubmersible: a simulator for estimating transient circulation temperature in offshore wells with the semi-submersible platform

    NASA Astrophysics Data System (ADS)

    Song, Xun-cheng; Liu, Yong-wang; Guan, Zhi-chuan

    2015-10-01

    Offshore wellbore temperature field is significant to drilling fluids program, equipment selection, evaluations on potential risks caused by casing thermal stress, etc. This paper mainly describes the theoretical basis, module structure and field verification of the simulator WHTSubmersible. This computer program is a useful tool for estimating transient temperature distribution of circulating drilling fluid on semi-submersible platform. WHTSubmersible is based on a mathematical model which is developed to consider radial and axial two-dimensional heat exchange of the inner drill pipe, the annulus, the drill pipe wall, the sea water and the formation in the process of drilling fluid circulation. The solution of the discrete equations is based on finite volume method with an implicit scheme. This scheme serves to demonstrate the numerical solution procedure. Besides, the simulator also considers the heating generated by drilling fluid circulation friction, drill bit penetrating rocks, friction between the drill column and the borehole wall, and the temperature effect on thermal physical properties and rheology of the drilling fluid. These measures ensure more accurate results. The simulator has been programmed as a dynamic link library using Visual C++, the routine interface is simple, which can be connected with other computer programs conveniently. The simulator is validated with an actual well temperature filed developed on a semi-submersible platform in South China, and the error is less than 5 %.

  10. Observed and simulated variability of the Atlantic meridional overturning circulation and the deep western boundary current

    NASA Astrophysics Data System (ADS)

    Mielke, Charlotte; Frajka-Williams, Eleanor; Gary, Stefan; Shimizu, Kenji; Toole, John; Baehr, Johanna

    2014-05-01

    Despite the importance of Atlantic meridional overturnig circulation (AMOC) for the climate of Africa, America and Europe, continuous AMOC observations are at present restricted to two latitudes, and are available for less than ten years. We therefore investigate whether the AMOC's variability can be inferred from measurements of the deep western boundary current (DWBC), which are already available at several locations. To that end, we jointly analyze the available 26°N RAPID and the 41°N Argo-based AMOC estimates with RAPID and line W (40°N) DWBC estimates. We also compare them to a 60-year simulation with a high-resolution NCEP-forced ocean model. The DWBC and its layers are defined dynamically in the model based on a comparison of temperature-versus-salinity data in model and observations and the time-dependent velocity field. On the timescales where observations are available, the model is able to reproduce the variability of the DWBC and its individual layers at both locations. Our preliminary analysis of the observational data and model results suggests that different mechanisms dominate the DWBC's variability at different timescales. On sub-seasonal to seasonal timescales, the DWBC is mostly barotropic, and its variability is linked to local processes. Thus, the DWBC has a well-defined seasonal cycle which is opposite to the seasonal cycle of the non-Ekman component of the AMOC seasonal cycle. On interannual timescales, there is no obvious relation between AMOC and DWBC. However, on decadal timescales, our analysis indicates covariability between AMOC and DWBC. We conclude that although caution should be exercised on interannual timescales, the DWBC might be used as a proxy for long-term AMOC trends and possibly modulations of the AMOC's seasonal cycle.

  11. Simulation of three-dimensional circulation and hydrography over the Grand Banks of Newfoundland

    NASA Astrophysics Data System (ADS)

    Han, Guoqi; Ma, Zhimin; deYoung, Brad; Foreman, Mike; Chen, Nancy

    There are few ocean models that both adequately resolve the cross-shelf structure of the Labrador Current and have been sufficiently evaluated against in situ observations at tidal, synoptic and seasonal scales. We present a three-dimensional, high-resolution, prognostic, nonlinear circulation model for the Newfoundland offshore based on the finite volume coastal ocean model (FVCOM). The FVCOM uses unstructured grid in the horizontal and thus allows efficient and effective use of grid resolution to resolve coastal- and shelf-scale features. The model results are evaluated against current meter measurements, vessel-mounted acoustic Doppler current profiler (ADCP) data, and tide-gauge observations. The FVCOM climatological monthly-mean currents over the shelf and slope show good agreement with observations and substantial improvement over those from an earlier finite-element model. The simulated tidal elevations agree well (4 cm of the root-sum-square absolute error for the total tidal height) with observations, and show improvement over previous tidal models over the Labrador Shelf. The hindcasts for the spring to fall of 1999 show reasonable skill in reproducing temperature, salinity and currents. At station 27 the observed temperature and salinity have seasonal ranges of 14 °C and 1.5 psu near the surface from April to November; while the root-mean-square (RMS) differences are 2.1 °C and 0.3 psu between the model and observations. On the Flemish Cap transect the observed temperature and salinity range from -1.5 to 13.1 °C and from 31.3 to 34.9 psu on July 17-20, 1999; while the RMS differences are 1.0 °C and 0.2 psu. The model-observation velocity difference ratio is 0.53 on this transect on July 17-18, 1999.

  12. a Mesoscale Planetary Boundary Layer Numerical Model for Simulations of Topographically Induced Circulations.

    NASA Astrophysics Data System (ADS)

    Huang, Ching-Yuang Albert

    1990-01-01

    A mesoscale planetary boundary layer (PBL) numerical model is developed to investigate airflow over complex topography. The model physics includes PBL turbulent transfer, atmospheric longwave and shortwave radiation, diurnal energy budgets over ground, cloud microphysics and subgrid cumulus parameterization. The model utilizes a new fourth order Crowley advection scheme which preserves phase and amplitude much better than other Crowley schemes. Turbulence closures using the turbulent kinetic energy (TKE) and dissipation (varepsilon ) equations are investigated with the level 2.5 scheme of Mellor and Yamada (1982) to better determine eddy diffusivities. One-dimensional (1-D) model results show that the PBL flows under various stability conditions are not significantly sensitive to the modified Blackadar's and Kolmogorov's eddy mixing length formations, although the latter yields excessively large mixing lengths in the entrainment region of the upper PBL. With the same prognostic TKE equation, the model results show insensitivity of the 1-D flow to the details of diagnostic formulations in the closures and to eddy Prandtl numbers. A 2-D model is used to stimulate January 28 cold -air outbreak over the Gulf Stream region during the IOP -2 (Intensive Observation Period) of the 1986 Genesis of Atlantic Lows Experiment (GALE). The modeled 2-D circulation system is found to be sensitive to Prandtl number, in contrast to the 1-D model results. Prandtl number becomes increasingly important as the clouds begin to interact with the marine boundary layer (MBL). Using the E-varepsilon closure, the model predicts the observed MBL structure that includes a low level jet west of the Gulf Stream warm core and a constrained boundary layer height due to the middle-level stable layer. Two cases with 3-D idealized flow are also simulated for the same GALE IOP. For the easterly onshore ambient flow, a confluence zone appears near the coastline in response to the strong oceanic

  13. North and equatorial Pacific Ocean circulation in the CORE-II hindcast simulations

    NASA Astrophysics Data System (ADS)

    Tseng, Yu-heng; Lin, Hongyang; Chen, Han-ching; Thompson, Keith; Bentsen, Mats; Böning, Claus W.; Bozec, Alexandra; Cassou, Christophe; Chassignet, Eric; Chow, Chun Hoe; Danabasoglu, Gokhan; Danilov, Sergey; Farneti, Riccardo; Fogli, Pier Giuseppe; Fujii, Yosuke; Griffies, Stephen M.; Ilicak, Mehmet; Jung, Thomas; Masina, Simona; Navarra, Antonio; Patara, Lavinia; Samuels, Bonita L.; Scheinert, Markus; Sidorenko, Dmitry; Sui, Chung-Hsiung; Tsujino, Hiroyuki; Valcke, Sophie; Voldoire, Aurore; Wang, Qiang; Yeager, Steve G.

    2016-08-01

    We evaluate the mean circulation patterns, water mass distributions, and tropical dynamics of the North and Equatorial Pacific Ocean based on a suite of global ocean-sea ice simulations driven by the CORE-II atmospheric forcing from 1963-2007. The first three moments (mean, standard deviation and skewness) of sea surface height and surface temperature variability are assessed against observations. Large discrepancies are found in the variance and skewness of sea surface height and in the skewness of sea surface temperature. Comparing with the observation, most models underestimate the Kuroshio transport in the Asian Marginal seas due to the missing influence of the unresolved western boundary current and meso-scale eddies. In terms of the Mixed Layer Depths (MLDs) in the North Pacific, the two observed maxima associated with Subtropical Mode Water and Central Mode Water formation coalesce into a large pool of deep MLDs in all participating models, but another local maximum associated with the formation of Eastern Subtropical Mode Water can be found in all models with different magnitudes. The main model bias of deep MLDs results from excessive Subtropical Mode Water formation due to inaccurate representation of the Kuroshio separation and of the associated excessively warm and salty Kuroshio water. Further water mass analysis shows that the North Pacific Intermediate Water can penetrate southward in most models, but its distribution greatly varies among models depending not only on grid resolution and vertical coordinate but also on the model dynamics. All simulations show overall similar large scale tropical current system, but with differences in the structures of the Equatorial Undercurrent. We also confirm the key role of the meridional gradient of the wind stress curl in driving the equatorial transport, leading to a generally weak North Equatorial Counter Current in all models due to inaccurate CORE-II equatorial wind fields. Most models show a larger

  14. 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.

  15. 3D Simulation: Microgravity Environments and Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Steve L.; Dischinger, Charles; Estes, Samantha; Parker, Nelson C. (Technical Monitor)

    2001-01-01

    Most, if not all, 3-D and Virtual Reality (VR) software programs are designed for one-G gravity applications. Space environments simulations require gravity effects of one one-thousandth to one one-million of that of the Earth's surface (10(exp -3) - 10(exp -6) G), thus one must be able to generate simulations that replicate those microgravity effects upon simulated astronauts. Unfortunately, the software programs utilized by the National Aeronautical and Space Administration does not have the ability to readily neutralize the one-G gravity effect. This pre-programmed situation causes the engineer or analysis difficulty during micro-gravity simulations. Therefore, microgravity simulations require special techniques or additional code in order to apply the power of 3D graphic simulation to space related applications. This paper discusses the problem and possible solutions to allow microgravity 3-D/VR simulations to be completed successfully without program code modifications.

  16. The Response of the South Asian Summer Monsoon Circulation to Intensified Irrigation in Global Climate Model Simulations

    NASA Technical Reports Server (NTRS)

    Shukla, Sonali P.; Puma, Michael J.; Cook, Benjamin I.

    2013-01-01

    Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson's r = -0.66 and r = -0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = -0.72 and r = -0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by *40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with

  17. Observed and simulated inter-decadal changes in the structure of Southern Hemisphere large-scale circulation

    NASA Astrophysics Data System (ADS)

    Freitas, Ana C. V.; Frederiksen, Jorgen S.; Whelan, Jennifer; O'Kane, Terence J.; Ambrizzi, Tércio

    2015-12-01

    Several studies have identified that, in the mid-1970s to early 1980s, a major shift occurred in the structure of the large-scale circulation in both hemispheres. This work employs the CSIRO Mk3L general circulation model in ensemble simulations with observed sea surface temperatures (SSTs) and historical time-evolving carbon dioxide (CO2) concentrations to investigate the inter-decadal changes found observationally in the jet streams, temperature, Hadley circulation, mean sea level pressure and precipitation. First, the performance of the model in simulating these changes for the mean July climate fields of 1949-1968 and 1975-1994, in comparison with the corresponding observations (NCEP/NCAR Reanalysis I and the Twentieth Century Reanalysis V2), is investigated. We find that the model is quite skilful in reproducing the broad features of the important inter-decadal changes that occurred in the mid-1970s. The model simulations and the NCEP/NCAR and twentieth century reanalyses agree in the eastern hemisphere; whereas in the western hemisphere the reanalyses show differences, and the simulations combine aspects of these two datasets. The role of the direct radiative forcing due to CO2 in driving the inter-decadal changes is also examined. Results indicate that, in comparison with the indirect effect of CO2 carried by the changing SSTs, there is little additional impact of the direct radiative forcing due to CO2 on the changes in the latter period. However, our simulations with fixed CO2 concentration have shown clearly that the atmospheric simulations with historical time-evolving CO2 concentrations are more skilful in reproducing the inter-decadal changes. The sensitivity of the ensemble results to employing the same or different time evolving sea ice boundary conditions in the ensemble members is also studied. The contributions of internal and external variability are discussed.

  18. Simulated pre-industrial climate in Bergen Climate Model (version 2): model description and large-scale circulation features

    NASA Astrophysics Data System (ADS)

    Otterâ, O. H.; Bentsen, M.; Bethke, I.; Kvamstø, N. G.

    2009-11-01

    The Bergen Climate Model (BCM) is a fully-coupled atmosphere-ocean-sea-ice model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate. Here, a pre-industrial multi-century simulation with an updated version of BCM is described and compared to observational data. The model is run without any form of flux adjustments and is stable for several centuries. The simulated climate reproduces the general large-scale circulation in the atmosphere reasonably well, except for a positive bias in the high latitude sea level pressure distribution. Also, by introducing an updated turbulence scheme in the atmosphere model a persistent cold bias has been eliminated. For the ocean part, the model drifts in sea surface temperatures and salinities are considerably reduced compared to earlier versions of BCM. Improved conservation properties in the ocean model have contributed to this. Furthermore, by choosing a reference pressure at 2000 m and including thermobaric effects in the ocean model, a more realistic meridional overturning circulation is simulated in the Atlantic Ocean. The simulated sea-ice extent in the Northern Hemisphere is in general agreement with observational data except for summer where the extent is somewhat underestimated. In the Southern Hemisphere, large negative biases are found in the simulated sea-ice extent. This is partly related to problems with the mixed layer parametrization, causing the mixed layer in the Southern Ocean to be too deep, which in turn makes it hard to maintain a realistic sea-ice cover here. However, despite some problematic issues, the pre-industrial control simulation presented here should still be appropriate for climate change studies requiring multi-century simulations.

  19. Simulated pre-industrial climate in Bergen Climate Model (version 2): model description and large-scale circulation features

    NASA Astrophysics Data System (ADS)

    Otterå, O. H.; Bentsen, M.; Bethke, I.; Kvamstø, N. G.

    2009-05-01

    The Bergen Climate Model (BCM) is a fully-coupled atmosphere-ocean-sea-ice model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate. Here, a pre-industrial multi-century simulation with an updated version of BCM is described and compared to observational data. The model is run without any form of flux adjustments and is stable for several centuries. The simulated climate reproduces the general large scale circulation in the atmosphere reasonably well, except for a positive bias in the high latitude sea level pressures distribution. Also, by introducing an updated turbulence scheme in the atmosphere model a persistent cold bias has been eliminated. For the ocean part, the model drifts in sea surface temperatures and salinities are considerably reduced compared to earlier versions of BCM. Improved conservation properties in the ocean have contributed to this. Furthermore, by choosing a reference pressure at 2000 m and including thermobaric effects in the ocean model, a more realistic meridional overturning circulation is simulated in the Atlantic Ocean. The simulated sea-ice extent in the Northern Hemisphere is in general agreement with observational data except for summer where the extent is somewhat underestimated. In the Southern Hemisphere, large negative biases are found in the simulated sea-ice extent. This is partly related to problems with the mixed layer parametrization, causing the mixed layer in the Southern Ocean to be too deep, which in turn makes it hard to maintain a realistic sea-ice cover here. However, despite some problematic issues, the pre-industrial control simulation presented here should still be appropriate for climate change studies requiring multi-century simulations.

  20. The global distribution of natural tritium in precipitation simulated with an Atmospheric General Circulation Model and comparison with observations

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Jean-Baptiste, P.; Risi, C.; Fourré, É.; Stenni, B.; Landais, A.

    2015-10-01

    The description of the hydrological cycle in Atmospheric General Circulation Models (GCMs) can be validated using water isotopes as tracers. Many GCMs now simulate the movement of the stable isotopes of water, but here we present the first GCM simulations modelling the content of natural tritium in water. These simulations were obtained using a version of the LMDZ General Circulation Model enhanced by water isotopes diagnostics, LMDZ-iso. To avoid tritium generated by nuclear bomb testing, the simulations have been evaluated against a compilation of published tritium datasets dating from before 1950, or measured recently. LMDZ-iso correctly captures the observed tritium enrichment in precipitation as oceanic air moves inland (the so-called continental effect) and the observed north-south variations due to the latitudinal dependency of the cosmogenic tritium production rate. The seasonal variability, linked to the stratospheric intrusions of air masses with higher tritium content into the troposphere, is correctly reproduced for Antarctica with a maximum in winter. LMDZ-iso reproduces the spring maximum of tritium over Europe, but underestimates it and produces a peak in winter that is not apparent in the data. This implementation of tritium in a GCM promises to provide a better constraint on: (1) the intrusions and transport of air masses from the stratosphere, and (2) the dynamics of the modelled water cycle. The method complements the existing approach of using stable water isotopes.

  1. Simulation of the mantle and crustal Helium isotope signature in the Mediterranean Sea using a high resolution regional circulation model

    NASA Astrophysics Data System (ADS)

    Ayache, Mohamed; Dutay, Jean-claude; Jean-baptiste, Philippe

    2015-04-01

    Helium isotopes (3He, 4He) are useful tracers for investigating the deep ocean circulation and for evaluating ocean general circulation models, because helium is a stable and conservative nuclide that does not take part in any chemical or biological processes. Helium in the ocean originates from three different sources: namely, (i) gas dissolution in equilibrium with atmospheric helium, (ii) helium-3 addition by radioactive decay of tritium (called tritiugenic helium), and (iii) injection of helium-3 and helium-4 by the submarine volcanic activity which occurs mainly at plate boundaries, and also addition of helium-4 from the crust and sedimentary cover by α-decay of uranium and thorium contained in various minerals (called terrigenic helium). Here we present the first simulation of the helium isotope distribution in the whole Mediterranean Sea, using a high resolution model (NEMO-MED12). The simulation was produced by building a simple source function for helium produced by submarine volcanic degassing in the main active areas of the Mediterranean, and by crustal degassing at sea bottom, based on previous estimates of the total flux of helium into the oceans. In addition to providing constraints on the degassing flux, our work provides information on the variability of the thermohaline circulation and the ventilation of the deep waters to constrain the degree to which the NEMO-MED12 can reproduce correctly the main hydrographic features of the Mediterranean Sea circulation. This study is part of the work carried out to assess the robustness of the NEMO-MED12 model, which will be used to study the evolution of the climate and its effect on the biogeochemical cycles in the Mediterranean Sea, and to improve our ability to predict the future evolution of the Mediterranean Sea under the increasing anthropogenic pressure.

  2. 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.

  3. Simulations and Observations of Circulation in the Oregon Coastal Transition Zone during the 2002-2003 Downwelling Season

    NASA Astrophysics Data System (ADS)

    Springer, S. R.; Allen, J. S.; Samelson, R. M.; Kurapov, A. L.; Egbert, G. D.; Miller, R. N.; de Rada, S.

    2008-12-01

    In comparison with summertime, relatively little is known about the circulation off Oregon during wintertime. We conducted a hindcast simulation of the period from October 1, 2002 to May 1, 2003, which coincided with a major observational field program. A non-assimilating, one-way nested model obtained initial conditions and boundary conditions from a larger scale, assimilating California Current model, and it was forced by wind stress from a regional mesoscale model, rainfall and heat fluxes calculated from a coarse resolution atmospheric model, and observed coastal river flows. At the beginning of the period, an upwelling circulation established by predominantly southward winds during the previous summer is in place. Vigorous storms in December deepen, freshen, and cool the mixed layer in the simulation, consistent with measurements along the Newport hydrographic line (44.65° N). Sensitivity studies demonstrate the importance of both rainfall and coastal river freshwater input to upper ocean stratification. Predominantly northward wind stress near the coast establishes a downwelling circulation with onshore Ekman transport, which holds freshwater input by rivers near the coast. When the wind reverses to southward for several days in early February, offshore Ekman transport spreads this freshwater feature seaward in both model simulations and high resolution hydrographic observations. During the mid to late winter, wind stress switches between strongly downwelling-favorable and weakly upwelling-favorable intervals of approximately 10-14 day duration. Comparison with moored current meters on the outer and midshelf shows that the model reproduces the corresponding reversals of the depth-averaged alongshore currents. Coastal trapped wave energy originating to the south passes into the domain and contributes to the strength of the upwelling response on the central Oregon coast.

  4. Effect of simulated pulpal fluid circulation on intrapulpal temperature following irradiation with an Nd:YVO4 laser.

    PubMed

    Braun, Andreas; Kecsmar, Susann; Krause, Felix; Berthold, Michael; Frentzen, Matthias; Frankenberger, Roland; Schelle, Florian

    2015-05-01

    It is suggested that pulpal fluid circulation has an impact on pulp temperature increase during heat-generating dental treatment procedures. Thus, the aim of the study was to assess the effect of a simulated pulpal fluid circulation on temperature changes inside the pulp chamber following laser irradiation of the tooth surface. Twenty freshly extracted human multirooted teeth were included and cross-sectioned along the long axis exposing two root canals each. The pulp chamber and root canals were cleaned from remaining soft tissues to achieve access for a temperature sensor and two cannulas to allow fluid circulation. Cross sections were glued together, and the roots were encased with silicone impression material to ensure the position of the connected devices. Each tooth was irradiated by employing a neodymium-doped yttrium orthovanadate (Nd:YVO4) laser at 1,064 nm with a pulse duration of 9 ps and a repetition rate of 500 kHz. A commercially available scanning system (SCANcube 7, SCANLAB) deflected the beam by providing rectangular irradiated areas of 0.5 mm edge length. Measurements were performed with four different settings for fluid circulation: without any water and with water (23 °C) at a flow rate of 6, 3, and 0 ml/min. The primary outcome measure was the maximum temperature difference (ΔT) after laser irradiation. Highest temperature changes (median 3.6 K, range 0.5-7.1 K) could be observed without any fluid inside the pulp chamber. Water without circulation decreased ΔT values statistically significantly (median 1.4 K, range 0.2-4.9 K) (p < 0.05). Lowest temperature changes could be observed with a water flow rate of 6 ml/min (median 0.8 K, range 0.2-3.7 K) (p < 0.05). Pulpal fluid circulation has a cooling effect on temperature increase caused by laser irradiation of dental hard tissues. Studies on heat generation during dental treatment procedures should include this aspect to assess a potential thermal injury of pulp tissue. PMID:24578013

  5. Virtual environment application with partial gravity simulation

    NASA Technical Reports Server (NTRS)

    Ray, David M.; Vanchau, Michael N.

    1994-01-01

    To support manned missions to the surface of Mars and missions requiring manipulation of payloads and locomotion in space, a training facility is required to simulate the conditions of both partial and microgravity. A partial gravity simulator (Pogo) which uses pneumatic suspension is being studied for use in virtual reality training. Pogo maintains a constant partial gravity simulation with a variation of simulated body force between 2.2 and 10 percent, depending on the type of locomotion inputs. this paper is based on the concept and application of a virtual environment system with Pogo including a head-mounted display and glove. The reality engine consists of a high end SGI workstation and PC's which drive Pogo's sensors and data acquisition hardware used for tracking and control. The tracking system is a hybrid of magnetic and optical trackers integrated for this application.

  6. Circulating tumor cells: advances in isolation and analysis, and challenges for clinical applications

    PubMed Central

    Harouaka, Ramdane; Kang, Zhigang; Zheng, Siyang; Cao, Liang

    2013-01-01

    Circulating tumor cells (CTCs) are rare cancer cells released from tumors into the bloodstream that are thought to have a key role in cancer metastasis. The presence of CTCs has been associated with worse prognosis in several major cancer types, including breast, prostate and colorectal cancer. There is considerable interest in CTC research and technologies for their potential use as cancer biomarkers that may enhance cancer diagnosis and prognosis, facilitate drug development, and improve the treatment of cancer patients. This review provides an update on recent progress in CTC isolation and molecular characterization technologies. Furthermore, the review covers significant advances and limitations in the clinical applications of CTC-based assays for cancer prognosis, response to anti-cancer therapies, and exploratory studies in biomarkers predictive of sensitivity and resistance to cancer therapies. PMID:24134902

  7. Practical applications of a versatile geothermal simulator

    SciTech Connect

    Nixon, J.F.

    1983-12-01

    Since 1976, the author has programmed, developed and applied a versatile twodimensional geothermal simulator for many interesting applications in cold regions engineering. This paper concentrates on applications to problems which have not been hitherto easily solved by other available geothermal models. Some of the important capabilities of the HAL simulator are: radial or cartesian coordinate options, convective ground water flow component, simple data entry, ability to specify internal pipes, or areas of specified temperature, monthly surface temperature and snow cover inputs as boundary conditions. The first application involves a steel pile, embedded in warm permafrost. A circular cryogenic storage tank is studied next, and the effectiveness of an insulation layer is illustrated. The convection option in the program is invoked when studying the effects of ground water flow around a series of vertical freeze pipes. Finally, the thermal degradation beneath an Arctic lake is studied, and the subsequent refreezing and growth of a pingo has been simulated.

  8. Practical applications of a versatile geothermal simulator

    SciTech Connect

    Nixon, J.F.; Halliwell, D.H.

    1982-01-01

    Since 1976, the senior author has programmed, developed and applied a versatile two-dimensional geothermal simulator for many interesting applications in cold regions engineering. This paper concentrates on applications to problems which have not been hitherto easily solved by other available geothermal models. Some of the important capabilities of the Hardy Associates (1978) Ltd. (HAL) simulator are radial or cartesian coordinate options, convective ground water flow component, simple data entry, ability to specify internal ''pipes'', or areas of specified temperature, monthly surface temperature and snow cover inputs. The first application involves a steel pile, embedded in warm permafrost. A circular cryogenic storage tank is studied next, and the effectiveness of an insulation layer is illustrated. The convection option in the program is invoked when studying the effects of ground water flow around a series of vertical freeze pipes. Finally, the thermal degradation beneath an Arctic lake is studied, and the subsequent re-freezing and growth of a pingo has been simulated.

  9. The Simulation of Stationary and Transient Geopotential-Height Eddies in January and July with a Spectral General Circulation Model.

    NASA Astrophysics Data System (ADS)

    Malone, Robert C.; Pitcher, Eric J.; Blackmon, Maurice L.; Puri, Kamal; Bourke, William

    1984-04-01

    We examine the characteristics of stationary and transient eddies in the geopotential-height field as simulated by a spectral general circulation model. The model possesses a realistic distribution of continents and oceans and realistic, but smoothed, topography. Two simulations with perpetual January and July forcing by climatological sea surface temperatures, sea ice, and insulation were extended to 1200 days, of which the final 600 days were used for the results in this study.We find that the stationary waves are well simulated in both seasons in the Northern Hemisphere, where strong forcing by orography and land-sea thermal contrasts exists. However, in the Southern Hemisphere, where no continents are present in midlatitudes, the stationary waves have smaller amplitude than that observed in both seasons.In both hemispheres, the transient eddies are well simulated in the winter season but are too weak in the summer season. The model fails to generate a sufficiently intense summertime midlatitude jet in either hemisphere, and this results in a low level of transient activity. The variance in the tropical troposphere is very well simulated. We examine the geographical distribution and vertical structure of the transient eddies. Fourier analysis in zonal wavenumber and temporal filtering am used to display the wavelength and frequency characteristics of the eddies.

  10. Applications of Simulated Students: An Exploration.

    ERIC Educational Resources Information Center

    VanLehn, Kurt; And Others

    1994-01-01

    Explains the concept of a computerized simulated student as a model of human learning and explores three areas of application: for teachers, for students, and for instructional designers during formative evaluation. Technical limitations, existing prototype systems, and possible future systems are discussed for each area. (Contains 85 references.)…

  11. Long-circulating Janus nanoparticles made by electrohydrodynamic co-jetting for systemic drug delivery applications

    PubMed Central

    Rahmani, Sahar; Villa, Carlos H.; Dishman, Acacia F.; Grabowski, Marika E.; Pan, Daniel C.; Durmaz, Hakan; Misra, Asish C; Colón-Meléndez, Laura; Solomon, Michael J.; Muzykantov, Vladimir R.; Lahann, Joerg

    2016-01-01

    Background Nanoparticles with controlled physical properties have been widely used for controlled release applications. In addition to shape, the anisotropic nature of the particles can be an important design criterion to ensure selective surface modification or independent release of combinations of drugs. Purpose Electrohydrodynamic (EHD) co-jetting is used for the fabrication of uniform anisotropic nanoparticles with individual compartments and initial physicochemical and biological characterization is reported. Methods EHD co-jetting is used to create nanoparticles, which are characterized at each stage with scanning electron microscopy (SEM), structured illumination microscopy (SIM), dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Surface immobilization techniques are used to incorporate polyethylene glycol (PEG) and I125 radiolabels into the nanoparticles. Particles are injected in mice and the particle distribution after 1, 4 and 24 hours is assessed. Results and discussion Nanoparticles with an average diameter of 105.7 nm are prepared by EHD co-jetting. The particles contain functional chemical groups for further surface modification and radiolabeling. The density of PEG molecules attached to the surface of nanoparticles is determined to range between 0.02 and 6.04 ligands per square nanometer. A significant fraction of the nanoparticles (1.2% injected dose per mass of organ) circulates in the blood after 24 h. Conclusion EHD co-jetting is a versatile method for the fabrication of nanoparticles for drug delivery. Circulation of the nanoparticles for 24 h is a pre-requisite for subsequent studies to explore defined targeting of the nanoparticles to a specific anatomic site. PMID:26453170

  12. The use of a numerical model to simulate the cavo-pulmonary assistance in Fontan circulation: a preliminary verification.

    PubMed

    Di Molfetta, Arianna; Amodeo, Antonio; Fresiello, Libera; Filippelli, Sergio; Pilati, Mara; Iacobelli, Roberta; Adorisio, Rachele; Colella, Dionisio; Ferrari, Gianfranco

    2016-06-01

    The lack of an established experience on the use of VAD for the cavo-pulmonary assistance leads to the need of dedicated VADs development and animal experiments. A dedicated numerical model could support clinical and experimental strategies design and new VADs testing. The aim of this work is to perform a preliminary verification of a lumped parameter model of the cardiovascular system to simulate Fontan physiology and the effect of cavo-pulmonary assistance. Literature data of 4 pigs were used to simulate animals' baseline, and then the model was tested in simulating Fontan circulation and cavo-pulmonary-assisted condition comparing the simulation outcome (Sim) with measured literature data (Me). The results show that the numerical model can well reproduce experimental data in all three conditions (baseline, Fontan and assisted Fontan) [cardiac output (l/min): Me = 2.8 ± 1.7, Sim = 2.8 ± 1.8; ejection fraction (%): Me = 57 ± 17, Sim = 54 ± 17; arterial systemic pressure (mmHg): Me = 41.8 ± 18.6, Sim = 43.8 ± 18.1; pulmonary arterial pressure (mmHg): Me = 15.4 ± 8.9, Sim = 17.7 ± 9.9; caval pressure (mmHg): Me = 6.8 ± 4.1, Sim = 7 ± 4.6]. Systolic elastance, arterial systemic and arterial pulmonary resistances increase (10, 69, and 100 %) passing from the biventricular circulation to the Fontan physiology and then decrease (21, 39, and 50 %) once the VAD was implanted. The ventricular external work decreases (71 %) passing from the biventricular circulation to the Fontan physiology and it increases three times after the VAD implantation in parallel with the VAD power consumption. A numerical model could support clinicians in an innovative and challenging field as the use of VAD to assist the Fontan physiology and it could be helpful to personalize the VAD insertion on the base of ventricular systo-diastolic function, circulatory parameters and energetic variables. PMID:26545595

  13. Port-O-Sim Object Simulation Application

    NASA Technical Reports Server (NTRS)

    Lanzi, Raymond J.

    2009-01-01

    Port-O-Sim is a software application that supports engineering modeling and simulation of launch-range systems and subsystems, as well as the vehicles that operate on them. It is flexible, distributed, object-oriented, and realtime. A scripting language is used to configure an array of simulation objects and link them together. The script is contained in a text file, but executed and controlled using a graphical user interface. A set of modules is defined, each with input variables, output variables, and settings. These engineering models can be either linked to each other or run as standalone. The settings can be modified during execution. Since 2001, this application has been used for pre-mission failure mode training for many Range Safety Scenarios. It contains range asset link analysis, develops look-angle data, supports sky-screen site selection, drives GPS (Global Positioning System) and IMU (Inertial Measurement Unit) simulators, and can support conceptual design efforts for multiple flight programs with its capacity for rapid six-degrees-of-freedom model development. Due to the assembly of various object types into one application, the application is applicable across a wide variety of launch range problem domains.

  14. Fluid Simulation in the Movies: Navier and Stokes Must Be Circulating in Their Graves

    NASA Astrophysics Data System (ADS)

    Tessendorf, Jerry

    2010-11-01

    Fluid simulations based on the Incompressible Navier-Stokes equations are commonplace computer graphics tools in the visual effects industry. These simulations mostly come from custom C++ code written by the visual effects companies. Their significant impact in films was recognized in 2008 with Academy Awards to four visual effects companies for their technical achievement. However artists are not fluid dynamicists, and fluid dynamics simulations are expensive to use in a deadline-driven production environment. As a result, the simulation algorithms are modified to limit the computational resources, adapt them to production workflow, and to respect the client's vision of the film plot. Eulerian solvers on fixed rectangular grids use a mix of momentum solvers, including Semi-Lagrangian, FLIP, and QUICK. Incompressibility is enforced with FFT, Conjugate Gradient, and Multigrid methods. For liquids, a levelset field tracks the free surface. Smooth Particle Hydrodynamics is also used, and is part of a hybrid Eulerian-SPH liquid simulator. Artists use all of them in a mix and match fashion to control the appearance of the simulation. Specially designed forces and boundary conditions control the flow. The simulation can be an input to artistically driven procedural particle simulations that enhance the flow with more detail and drama. Post-simulation processing increases the visual detail beyond the grid resolution. Ultimately, iterative simulation methods that fit naturally in the production workflow are extremely desirable but not yet successful. Results from some efforts for iterative methods are shown, and other approaches motivated by the history of production are proposed.

  15. Zonal wavenumber three traveling waves in the northern hemisphere of Mars simulated with a general circulation model

    NASA Astrophysics Data System (ADS)

    Wang, Huiqun; Richardson, Mark I.; Toigo, Anthony D.; Newman, Claire E.

    2013-04-01

    Observations suggest a strong correlation between curvilinear shaped traveling dust storms (observed in wide angle camera images) and eastward traveling zonal wave number m = 3 waves (observed in thermal data) in the northern mid and high latitudes during the fall and winter. Using the MarsWRF General Circulation Model, we have investigated the seasonality, structure and dynamics of the simulated m = 3 traveling waves and tested the hypothesis that traveling dust storms may enhance m = 3 traveling waves under certain conditions. Our standard simulation using a prescribed "MGS dust scenario" can capture the observed major wave modes and strong near surface temperature variations before and after the northern winter solstice. The same seasonal pattern is also shown by the simulated near surface meridional wind, but not by the normalized surface pressure. The simulated eastward traveling 1.4 < T < 10 sol m = 3 waves are confined near the surface in terms of the temperature perturbation, EP flux and eddy available potential energy, and they extend higher in terms of the eddy winds and eddy kinetic energy. The signature of the simulated m = 3 traveling waves is stronger in the near surface meridional wind than in the near surface temperature field. Compared with the standard simulation, our test simulations show that the prescribed m = 3 traveling dust blobs can enhance the simulated m = 3 traveling waves during the pre- and post-solstice periods when traveling dust storms are frequently observed in images, and that they have negligible effect during the northern winter solstice period when traveling dust storms are absent. The enhancement is even greater in our simulation when dust is concentrated closer to the surface. Our simulations also suggest that dust within the 45-75°N band is most effective at enhancing the simulated m = 3 traveling waves. There are multiple factors influencing the strength of the simulated m = 3 traveling waves. Among those, our study

  16. Variability of the Martian thermosphere during eight Martian years as simulated by a ground-to-exosphere global circulation model

    NASA Astrophysics Data System (ADS)

    González-Galindo, F.; López-Valverde, M. A.; Forget, F.; García-Comas, M.; Millour, E.; Montabone, L.

    2015-11-01

    Using a ground-to-exosphere general circulation model for Mars we have simulated the variability of the dayside temperatures at the exobase during eight Martian years (MY, from MY24 to MY31, approximately from 1998 to 2013), taking into account the observed day-to-day solar and dust load variability. We show that the simulated temperatures are in good agreement with the exospheric temperatures derived from Precise Orbit Determination of Mars Global Surveyor. We then study the effects of the solar variability and of two planetary-encircling dust storms on the simulated temperatures. The seasonal effect produced by the large eccentricity of the Martian orbit translates in an aphelion-to-perihelion temperature contrast in every simulated year. However, the magnitude of this seasonal temperature variation is strongly affected by the solar conditions, ranging from 50 K for years corresponding to solar minimum conditions to almost 140 K during the last solar maximum. The 27 day solar rotation cycle is observed on the simulated temperatures at the exobase, with average amplitude of the temperature oscillation of 2.6 K but with a significant interannual variability. These two results highlight the importance of taking into account the solar variability when simulating the Martian upper atmosphere and likely have important implications concerning the atmospheric escape rate. We also show that the global dust storms in MY25 and MY28 have a significant effect on the simulated temperatures. In general, they increase the exospheric temperatures over the low latitude and midlatitude regions and decrease them in the polar regions.

  17. 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).

  18. Experiments in monthly mean simulation of the atmosphere with a coarse-mesh general circulation model

    NASA Technical Reports Server (NTRS)

    Lutz, R. J.; Spar, J.

    1978-01-01

    The Hansen atmospheric model was used to compute five monthly forecasts (October 1976 through February 1977). The comparison is based on an energetics analysis, meridional and vertical profiles, error statistics, and prognostic and observed mean maps. The monthly mean model simulations suffer from several defects. There is, in general, no skill in the simulation of the monthly mean sea-level pressure field, and only marginal skill is indicated for the 850 mb temperatures and 500 mb heights. The coarse-mesh model appears to generate a less satisfactory monthly mean simulation than the finer mesh GISS model.

  19. Simulation of the effects of proposed tide gates on circulation, flushing, and water quality in residential canals, Cape Coral Florida

    USGS Publications Warehouse

    Goodwin, Carl R.

    1991-01-01

    Decades of dredging and filling of Florida's low-lying coastal wetlands have produced thousands of miles of residential tidal canals and adjacent waterfront property. Typically, these canals are poorly flushed, and over time, accumulated organic-rich bottom materials, contribute to an increasingly severe degraded water quality. One-dimensional hydrodynamic and constituent-transport models were applied to two dead-end canal systems to determine the effects of canal system interconnection using tide gates on water circulation and constituent flushing. The model simulates existing and possible future circulation and flushing conditions in about 29 miles of the approximately 130 miles of tidally influenced canals in Cape Coral, located on the central west coast of peninsular Florida. Model results indicate that tidal water-level differences between the two canal systems can be converted to kinetic energy, in the form of increased water circulation, but the use of one-way tide gate interconnections. Computations show that construction of from one to four tide gates will cause replacement of a volume of water equivalent to the total volume of canals in both systems in 15 to 9 days, respectively. Because some canals flush faster than others, 47 and 21 percent of the original canal water will remain in both systems 50 days after start of operation of one and four tide gates, respectively. Some of the effects that such increased flushing are expected to have include reduced density stratification and associated dissolved-oxygen depletion in canal bottom waters, increased localized reaeration, and more efficient discharge of stormwater runoff entering the canals.

  20. Numerical simulation of the seasonal and interannual variability of the tropical Atlantic Ocean circulation during the 1980s

    SciTech Connect

    Huang, Bohua.

    1992-01-01

    A nine-year (1980-88) surface wind stress data set over the tropical Atlantic ocean is constructed based on the European Centre for Medium Range Weather Forecasts (ECMWF) twice-daily wind analysis. Its quality is checked against an independent data set by Servain et al. (1985) based on ship observations. A comprehensive analysis of these two data sets shows a strong seasonal cycle of the wind stress over the equatorial Atlantic ocean. Interannually, the stress field is dominated by a seesaw between the northeast and southeast trade winds, with anomalously strong (weak) southeast (northeast) trade winds during 1980-83 and a reversed pattern during 1984-88. Two nine-year simulations of the tropical Atlantic ocean circulation are performed with a general circulation model, one forced by the twice-daily, and the second by monthly averaged ECMWF surface wind stresses. Comparisons with available observations show that the seasonal ocean circulation and interannual signals of the sea surface temperature (SST), i.e., the dipole oscillation and abnormal warmings, are that the seasonal cycle of the subtropical and tropical Atlantic has an in-phase relationship with the seasonal change of the surface wind stress and the interannual SST dipole oscillation is generally in balance with the seesaw pattern of the trade wind systems although wave processes are important during the transition of phase. In 1984, the transition of the SST dipole from north-warm/south-cold to its opposite occurred during an equatorial warming event. This warming event was initiated by the relaxation of equatorial easterly wind, which stimulated heat transfer first eastward along the equator, then to the southern ocean and caused a deepening of the thermocline in the Gulf of Guinea and the southern ocean. Another warming event occurred in 1987-88, which restored the disappearing north cold/warm dipole.

  1. Mars' Thermal Structure From The Lower To Middle Atmosphere: NASA Ames Mars General Circulation Simulations

    NASA Astrophysics Data System (ADS)

    Brecht, A. S.; Hollingsworth, J. L.; Kahre, M. A.

    2014-07-01

    The NASA Ames Mars General Ciculation Model (MGCM) has been extended to incorporate the middle atmosphere (~80 km to ~120 km). The extended MGCM simulated thermal structure will be compared to MRO-MCS and MEx-SPICAM observations.

  2. Molecular dynamics simulations: advances and applications

    PubMed Central

    Hospital, Adam; Goñi, Josep Ramon; Orozco, Modesto; Gelpí, Josep L

    2015-01-01

    Molecular dynamics simulations have evolved into a mature technique that can be used effectively to understand macromolecular structure-to-function relationships. Present simulation times are close to biologically relevant ones. Information gathered about the dynamic properties of macromolecules is rich enough to shift the usual paradigm of structural bioinformatics from studying single structures to analyze conformational ensembles. Here, we describe the foundations of molecular dynamics and the improvements made in the direction of getting such ensemble. Specific application of the technique to three main issues (allosteric regulation, docking, and structure refinement) is discussed.

  3. A Third Note on Ageing in a Library Circulation Model: Applications to Future Use and Relegation.

    ERIC Educational Resources Information Center

    Burrell, Quentin L.

    1987-01-01

    Describes a circulation model for academic research libraries which uses the mixed Poisson model, incorporating ageing of library materials, to predict future use of monographs and to suggest weeding procedures based on frequency of circulation. Longitudinal studies are examined and statistical details are appended. (Author/LRW)

  4. Application of remote sensing to study nearshore circulation. [and the continental shelf

    NASA Technical Reports Server (NTRS)

    Zeigler, J.; Lobecker, R.; Stauble, D.; Welch, C.; Haas, L.; Fang, C. S.

    1974-01-01

    The research to use remote sensing techniques for studying the continental shelf is reported. The studies reported include: (1) nearshore circulation in the vincinity of a natural tidal inlet; (2) identification of indicators of biological activity; (3) remote navigation system for tracking free drifting buoys; (4) experimental design of an estuaring tidal circulation; and (5) Skylab support work.

  5. A new geometrical approach to Eulerian transport: an application to the ocean circulation; final report

    NASA Technical Reports Server (NTRS)

    McWilliams, J. C.; Chao, Y.

    2003-01-01

    The main objective of this work is to investigate the transport processes in the large-scale ocean circulations using the new transport theory. We focus on the mid-latitude ocean circulation, especially the Gulf Stream, because it is recognized as a most energetic ocean current and plays a crucial role in maintaining the earth's climate system.

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

    PubMed

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

    2007-08-15

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

  7. Modeling blood flow circulation in intracranial arterial networks: a comparative 3D/1D simulation study.

    PubMed

    Grinberg, L; Cheever, E; Anor, T; Madsen, J R; Karniadakis, G E

    2011-01-01

    We compare results from numerical simulations of pulsatile blood flow in two patient-specific intracranial arterial networks using one-dimensional (1D) and three-dimensional (3D) models. Specifically, we focus on the pressure and flowrate distribution at different segments of the network computed by the two models. Results obtained with 1D and 3D models with rigid walls show good agreement in massflow distribution at tens of arterial junctions and also in pressure drop along the arteries. The 3D simulations with the rigid walls predict higher amplitude of the flowrate and pressure temporal oscillations than the 1D simulations with compliant walls at various segments even for small time-variations in the arterial cross-sectional areas. Sensitivity of the flow and pressure with respect to variation in the elasticity parameters is investigated with the 1D model. PMID:20661645

  8. Comparison of spectral surface albedos and their impact on the general circulation model simulated surface climate

    NASA Astrophysics Data System (ADS)

    Roesch, A.; Wild, M.; Pinker, R.; Ohmura, A.

    2002-07-01

    This study investigates the impact of spectrally resolved surface albedo on the total surface albedo. The neglect of albedo variation within the shortwave spectrum may lead to substantial errors as the atmospheric water greatly influences the spectral distribution of the incoming radiation. It is shown that ignoring the spectral dependence of the surface albedo will affect the predicted climate. The study reveals substantial changes in the climate over northern Africa when modifying the surface albedo of the Sahara deserts. Detailed information is given how the European Center/Hamburg General Circulation Model (ECHAM4) can be extended to include surface boundary conditions for both the visible and near-infrared incoming radiation. This comprises global climatologies for both the visible and near-infrared albedo for snow-free conditions, as well as the corresponding albedo values over snow, land-/sea ice and over snow covered forests. Comparisons between several available surface albedo climatologies and a newly compiled albedo data set show substantial scatter in estimated albedos. The largest albedo differences are found in snow covered forest regions as well as in arid and semi-arid terrains.

  9. Multidecadal Variability Simulated With an Atmospheric General Circulation Model Forced With Observed Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Grosfeld, K.; Rimbu, N.; Lohmann, G.; Lunkeit, F.

    2002-12-01

    We investigate the response of an atmospheric general circulation model to observed sea surface temperature for the instrumental period 1856-2000. The model used is the {nderline P}ortable {nderline U}niversity {nderline M}odel of the {nderline A}tmosphere (PUMA) developed at the University of Hamburg for long-term climate studies. When the model is forced with global sea surface temperatures (SSTs) the model interdecadal variability is dominated by the Atlantic Interdecadal Mode (AIM) and its associated teleconnection patterns. The modeled interdecadal variability sea surface patterns are in good agreement with analysis of observational time series in an ensemble mode integration. Positive SST anomalies and a sea level pressure (SLP) dipole pattern dominate the North Atlantic while a strong positive anomaly in SLP is characteristic for the North Pacific Ocean. Although the observational database is short, investigations of the typical AIM patterns before and after the climate shift in the 1970's suggest an oscillatory multidecadal mode rather than a singular event for that period. Additional experiments with ''Atlantic only'' forcing depict strong sensitivities of the relative roles of Atlantic and Pacific SST data initiating variability at multidecadal time scales. Our results have implications for climate predictability on long time scales from observed SST data.

  10. Numerical Simulations of the Steady and Unsteady Aerodynamic Characteristics of a Circulation Control Wing Airfoil

    NASA Technical Reports Server (NTRS)

    Liu, Yi; Sankar, Lakshmi N.; Englar, Robert J.; Ahuja, Krishan K.

    2003-01-01

    The aerodynamic characteristics of a Circulation Control Wing (CCW) airfoil have been numerically investigated, and comparisons with experimental data have been made. The configuration chosen was a supercritical airfoil with a 30 degree dual-radius CCW flap. Steady and pulsed jet calculations were performed. It was found that the use of steady jets, even at very small mass flow rates, yielded a lift coefficient that is comparable or superior to conventional high-lift systems. The attached flow over the flap also gave rise to lower drag coefficients, and high L/D ratios. Pulsed jets with a 50% duty cycle were also studied. It was found that they were effective in generating lift at lower reduced mass flow rates compared to a steady jet, provided the pulse frequency was sufficiently high. This benefit was attributable to the fact that the momentum coefficient of the pulsed jet, during the portions of the cycle when the jet was on, was typically twice as much as that of a steady jet.

  11. 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.

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

    SciTech Connect

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

    1992-11-01

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

  13. Application of linear logic to simulation

    NASA Astrophysics Data System (ADS)

    Clarke, Thomas L.

    1998-08-01

    Linear logic, since its introduction by Girard in 1987 has proven expressive and powerful. Linear logic has provided natural encodings of Turing machines, Petri nets and other computational models. Linear logic is also capable of naturally modeling resource dependent aspects of reasoning. The distinguishing characteristic of linear logic is that it accounts for resources; two instances of the same variable are considered differently from a single instance. Linear logic thus must obey a form of the linear superposition principle. A proportion can be reasoned with only once, unless a special operator is applied. Informally, linear logic distinguishes two kinds of conjunction, two kinds of disjunction, and also introduces a modal storage operator that explicitly indicates propositions that can be reused. This paper discuses the application of linear logic to simulation. A wide variety of logics have been developed; in addition to classical logic, there are fuzzy logics, affine logics, quantum logics, etc. All of these have found application in simulations of one sort or another. The special characteristics of linear logic and its benefits for simulation will be discussed. Of particular interest is a connection that can be made between linear logic and simulated dynamics by using the concept of Lie algebras and Lie groups. Lie groups provide the connection between the exponential modal storage operators of linear logic and the eigen functions of dynamic differential operators. Particularly suggestive are possible relations between complexity result for linear logic and non-computability results for dynamical systems.

  14. Interannual Variability of Martian Global Dust Storms: Simulations with a Low-Order Model of the General Circulation

    NASA Technical Reports Server (NTRS)

    Pankine, A. A.; Ingersoll, Andrew P.

    2002-01-01

    We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good. Interannual variability of GDSs is possible in the IBM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up its a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.

  15. A general circulation model simulation of the springtime Antarctic ozone decrease and its impact on mid-latitudes

    SciTech Connect

    Cariolle, D.; Lasserre-Bigorry, A.; Royer, J.F. ); Geleyn, J.F. )

    1990-02-20

    Ozone is treated as an interactive variable calculated by means of a continuity equation which takes account of advection and photochemical production and loss. The ozone concentration is also used to compute the heating and cooling rates due to the absorption of solar ultraviolet radiation, and the infrared emission in the stratosphere. The daytime ozone decrease due to the perturbed chlorine chemistry found at high southern latitudes is introduced as an extra loss in the ozone continuity equation. Results of the perturbed simulation show a very good agreement with the ozone measurements made during spring 1987. The simulation also shows the development of a high-latitude anomalous circulation, with a warming of the upper stratosphere resulting mainly from dynamical heating. In addition, a substantial ozone decrease is found at mid-latitudes in a thin stratospheric layer located between the 390 and the 470 K {theta} surfaces. A significant residual ozone decrease is found at the end of the model integration, 7 months after the final warming and the vortex breakdown. If there is a significant residual ozone decrease in the atmosphere, the ozone trends predicted by photochemical models which do not take into account the high-latitude perturbed chemistry are clearly inadequate. Finally, it is concluded that further model simulations at higher horizontal resolution, possibly with a better representation of the heterogeneous chemistry, will be needed to evaluate with more confidence the magnitude of the mid-latitudinal ozone depletion induced by the ozone hole formation.

  16. Inter-comparison of the mean circulation in the Coral and Solomon Sea simulated by high resolution ocean models

    NASA Astrophysics Data System (ADS)

    Maes, C.; Durand, F.; Gasparin, F.; Melet, A.; Ganachaud, A.

    2010-12-01

    Of primary importance to the properties of water masses transported by the northern limb of the South Pacific subtropical gyre toward the equatorial band, the transfer within the Coral and, ultimately, the Solomon Sea is perturbed by the labyrinthine topography of the region. It results in highly energetic currents and complex pathways through the Vanuatu Archipelago and New Caledonia, at the entrance of the Coral Sea, and through the Solomon Sea once the flow has bifurcated northward along the coasts of Australia and of the Louisiade Archipelago of Papua New Guinea. In the Coral Sea, the existence of the North Vanuatu Jet and North Caledonian Jet is now well established but their variations as well as their detailed characteristics, including for instance their vertical extension, remain largely unknown. In this study, recourse to ocean simulations is made in order to highlight the representation of such complex circulation of the south western Pacific Ocean and to analyze the long term variability and physical mechanism implied in the jet dynamics. A brief overview of recent observations collected through the comprehensive observational SPICE program (CLIVAR/WCRP) will first be presented in order to set the context. Then, 6 different state-of-the-art numerical experiments with high horizontal resolution, ranging from 1/10 to 1/12 degree, and realistic topography regionally focused on the Coral and Solomon Sea or extracted from global experiments, are analyzed. Here, we will consider OGCMs forced by realistic and observed atmospheric fields but each model has its own strategy in terms of diffusion, topography representation and boundaries condition when appropriate. The focus is set primarily on the annual mean circulation of the upper ocean layers (above the 1000-m depth) and on the water mass transports simulated in the vicinity of the various topographic obstacles. The results will underline that most of high resolution numerical models have reached a high

  17. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    NASA Astrophysics Data System (ADS)

    Jöckel, P.; Tost, H.; Pozzer, A.; Brühl, C.; Buchholz, J.; Ganzeveld, L.; Hoor, P.; Kerkweg, A.; Lawrence, M. G.; Sander, R.; Steil, B.; Stiller, G.; Tanarhte, M.; Taraborrelli, D.; van Aardenne, J.; Lelieveld, J.

    2006-11-01

    The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model setup up to 0.01 hPa was used at spectral T42 resolution to simulate the lower and middle atmosphere. With the high vertical resolution the model simulates the Quasi-Biennial Oscillation. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. In the simulations presented here a Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998-2005. This allows an efficient and direct evaluation with satellite and in-situ data. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated well, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of inter-annual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the

  18. Communication Simulations for Power System Applications

    SciTech Connect

    Fuller, Jason C.; Ciraci, Selim; Daily, Jeffrey A.; Fisher, Andrew R.; Hauer, Matthew L.

    2013-05-29

    New smart grid technologies and concepts, such as dynamic pricing, demand response, dynamic state estimation, and wide area monitoring, protection, and control, are expected to require considerable communication resources. As the cost of retrofit can be high, future power grids will require the integration of high-speed, secure connections with legacy communication systems, while still providing adequate system control and security. While considerable work has been performed to create co-simulators for the power domain with load models and market operations, limited work has been performed in integrating communications directly into a power domain solver. The simulation of communication and power systems will become more important as the two systems become more inter-related. This paper will discuss ongoing work at Pacific Northwest National Laboratory to create a flexible, high-speed power and communication system co-simulator for smart grid applications. The framework for the software will be described, including architecture considerations for modular, high performance computing and large-scale scalability (serialization, load balancing, partitioning, cross-platform support, etc.). The current simulator supports the ns-3 (telecommunications) and GridLAB-D (distribution systems) simulators. Ongoing and future work will be described, including planned future expansions for a traditional transmission solver. A test case using the co-simulator, utilizing a transactive demand response system created for the Olympic Peninsula and AEP gridSMART demonstrations, requiring two-way communication between distributed and centralized market devices, will be used to demonstrate the value and intended purpose of the co-simulation environment.

  19. Numerical simulation of local atmospheric circulations in the pre-Alpine area between Lake Garda and Verona

    NASA Astrophysics Data System (ADS)

    Laiti, L.; Serafin, S.; Zardi, D.

    2010-09-01

    The pre-Alpine area between Lake Garda and Verona displays a very complex and heterogeneous territory, allowing the development of several interacting systems of thermally driven local winds, the major being the lake/land breeze system on the coasts of Lake Garda and the up/down-valley wind system between the plain and the river Adige Valley. In order to investigate the local wind patterns, a series of nested numerical simulations with a horizontal resolution of 500 m were carried out using the ARPS 5.2.9 model (Xue et al. 2000, 2001), considering a fair weather day suitable for a clear development of the expected circulations (15th July 2003). The simulated wind speed and direction, pressure, temperature and water vapour mixing ratio were compared to synoptic scale meteorological charts, to vertical profiles from radiosoundings taken at the major sounding stations of the alpine region and to local scale measurements performed at the surface station of Dolcè (at the inlet of the Adige Valley). Numerical results at all scales were found to be in very good agreement with the available sets of meteorological observations. The analysis of the diurnal evolution of the 3D fields of temperature, moisture content, wind and turbulent kinetic energy allowed the identification of a very shallow and clearly defined breeze front of cold and humid air moving from off-shore towards the Lake Garda coast, from the late morning (10:00 LST) until the evening (20:00 LST). The diurnal up-valley breeze was also well reproduced: the valley atmosphere displays a thick mixed layer dominated by shallow turbulent convection between 11:00 LST and 21:00 LST. Lateral slope winds were also recognized, as they created cross-valley convective cells. While no clear evidence of a nocturnal land breeze was found in the simulations, the nocturnal down-valley wind in the Adige Valley was clearly reproduced. Finally, a scalar transport equation was added to the ARPS model in order to simulate transport

  20. Developing emulators of a general circulation model for applications in Earth system modelling

    NASA Astrophysics Data System (ADS)

    Tran, Giang; Oliver, Kevin; Sobester, Andras; Toal, David; Holden, Philip; Marsh, Robert; Challenor, Peter; Edwards, Neil

    2015-04-01

    To study climate change on multi-millennial timescales, efficient models with simplified and parameterized processes are required. This is particularly important if observations are to be used effectively constrain models, an endeavour which demands large numbers of simulations. Unfortunately, the reduction in explicitly modelled processes can lead to underestimation of responses in the system that are essential to the understanding of palaeoclimate. To address this, we intend to replace a simple component of an efficient model with a statistical model (an emulator) of a more comprehensive one. Efficient construction of such an emulator is achieved by exploiting the relationship among different levels of the climate model hierarchy. Using a multi-level emulation technique, outputs from an atmospheric general circulation model (GCM), called PLASIM, are efficiently emulated by utilising the extra information gained from the computationally cheap atmosphere of an efficient model called GENIE-1. Even though the two atmospheric models chosen have large structural differences, useful links between them are identified and Gaussian process emulators of PLASIM 2-D surface air temperature and precipitation fields are successfully constructed. The result shows that the multi-level emulators of PLASIM's output fields can be built using only one third the amount of expensive data required by the normal single-level technique. The constructed emulators are shown to capture 95.4% and 80.3% of the variance in surface air temperature and precipitation, respectively, across a validation ensemble. GCM emulators constructed using the proposed method can potentially replace the current simple component of the efficient model, resulting in a higher fidelity version of the model without a significant increase in computational cost.

  1. Earth radiation budget and cloudiness simulations with a general circulation model

    NASA Technical Reports Server (NTRS)

    HARSHVARDHAN; Randall, David A.; Corsetti, Thomas G.; Dazlich, Donald A.

    1989-01-01

    A GCM with new parameterizations of solar and terrestrial radiation, parameterized cloud optical properties, and a simple representation of the cloud liquid water feedback is used with several observational data sets to analyze the effects of cloudiness on the earth's radiation budget. The January and July results from the model are in reasonable agreement with data from Nimbus-7. It is found that the simulated cloudiness overpredicts subtropical and midlatitude cloudiness. The simulated atmospheric cloud radiative forcing is examined. The clear-sky radiation fields obtained by two methods of Cess and Potter (1987) are compared. Also, a numerical experiment was performed to determine the effects of the water vapor continuum on the model results.

  2. A review of existing gas-cooled reactor circulators with application of the lessons learned to the new production reactor circulators

    SciTech Connect

    White, L.S.

    1990-07-01

    This report presents the results of a study of the lessons learned during the design, testing, and operation of gas-cooled reactor coolant circulators. The intent of this study is to identify failure modes and problem areas of the existing circulators so this information can be incorporated into the design of the circulators for the New Production Reactor (NPR)-Modular High-Temperature Gas Cooled Reactor (MHTGR). The information for this study was obtained primarily from open literature and includes data on high-pressure, high-temperature helium test loop circulators as well as the existing gas cooled reactors worldwide. This investigation indicates that trouble free circulator performance can only be expected when the design program includes a comprehensive prototypical test program, with the results of this test program factored into the final circulator design. 43 refs., 7 tabs.

  3. 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.

  4. Integral Circulation Experiment: Thermal-hydraulic simulator of a heavy liquid metal reactor

    NASA Astrophysics Data System (ADS)

    Tarantino, M.; Agostini, P.; Benamati, G.; Coccoluto, G.; Gaggini, P.; Labanti, V.; Venturi, G.; Class, A.; Liftin, K.; Forgione, N.; Moreau, V.

    2011-08-01

    In the frame of the IP-EUROTRANS (6th Framework Program EU), domain DEMETRA, ENEA was involved in the Work Package 4.5 " Large Scale Integral Test", devoted to characterize a relevant portion of a sub-critical ADS reactor block (core, internals, heat exchanger, cladding for fuel elements) in steady state, transient and accidental conditions. More in details ENEA assumed the commitment to perform an integral experiment aiming to reproduce the primary flow path of the " European Transmutation Demonstrator (ETD)" pool-type nuclear reactor, cooled by Lead Bismuth Eutectics (LBE). This experimental activity, called " Integral Circulation Experiment (ICE)", has been implemented merging the efforts of several research institutes, among which, besides ENEA, FZK, CRS4 and University of Pisa, allowing to design an appropriate test section to be installed in the CIRCE facility. The goal of the experiments is therefore to demonstrate the technological feasibility of a heavy liquid metal (HLM) nuclear system pool-type in a relevant scale (1 MW), investigating the related thermal-hydraulic behaviour (heat source and heat exchanger coupling, primary system and downcomer coupling, gas trapping into the main stream, thermal stratification in the pool, forced and mixed convection in rod bundle) under both steady state and transient conditions. Moreover the preliminary as well as the planned experiments aims to address performance and reliability tests of some prototypical components, such as heat source, heat exchanger, chemistry control system. The paper reports a detailed description of the experiment, the design performed for the test section and its main components as well as the preliminary experimental results carried out in the first experimental campaign run on the CIRCE pool, which consists of a full power steady state test. The preliminary experimental results carried out have demonstrate the proper design of the test section trough the experiment goals as well as the HLM

  5. Numerical simulation of 137Cs and (239,240)Pu concentrations by an ocean general circulation model.

    PubMed

    Tsumune, Daisuke; Aoyama, Michio; Hirose, Katsumi

    2003-01-01

    We simulated the spatial distributions and the temporal variations of 137Cs and (239,240)Pu concentrations in the ocean by using the ocean general circulation model which was developed by National Center of Atmospheric Research. These nuclides are introduced into seawaters from global fallout due to atmospheric nuclear weapons tests. The distribution of radioactive deposition on the world ocean is estimated from global precipitation data and observed values of annual deposition of radionuclides at the Meteorological Research Institute in Japan and several observed points in New Zealand. Radionuclides from global fallout have been transported by advection, diffusion and scavenging, and this concentration reduces by radioactive decay in the ocean. We verified the results of the model calculations by comparing simulated values of 137Cs and (239,240)Pu in seawater with the observed values included in the Historical Artificial Radionuclides in the HAM database, which has been constructed by the Meteorological Research Institute. The vertical distributions of the calculated 137Cs concentrations were in good agreement and are in good agreement with the observed profiles in the 1960s up to 250 m, in the 1970s up to 500 m, in the 1980s up to 750 m and in the 1990s up to 750 m. However, the calculated 137Cs concentrations were underestimated compared with the observed 137Cs at the deeper layer. This may suggest other transport processes of 137Cs to deep waters. The horizontal distributions of 137Cs concentrations in surface water could be simulated. A numerical tracer release experiment was performed to explain the horizontal distribution pattern. A maximum (239,240)Pu concentration layer occurs at an intermediate depth for both observed and calculated values, which is formed by particle scavenging. The horizontal distributions of the calculated (239,240)Pu concentrations in surface water could be simulated by considering the scavenging effect. PMID:12860090

  6. A nesting model for bias correction of variability at multiple time scales in general circulation model precipitation simulations

    NASA Astrophysics Data System (ADS)

    Johnson, Fiona; Sharma, Ashish

    2012-01-01

    Climate change impact assessments of water resources systems require simulations of precipitation and evaporation that exhibit distributional and persistence attributes similar to the historical record. Specifically, there is a need to ensure general circulation model (GCM) simulations of rainfall for the current climate exhibit low-frequency variability that is consistent with observed data. Inability to represent low-frequency variability in precipitation and flow leads to biased estimates of the security offered by water resources systems in a warmer climate. This paper presents a method to postprocess GCM precipitation simulations by imparting correct distributional and persistence attributes, resulting in sequences that are representative of observed records across a range of time scales. The proposed approach is named nesting bias correction (NBC), the rationale being to correct distributional and persistence bias from fine to progressively longer time scales. In the results presented here, distributional attributes have been represented by order 1 and 2 moments with persistence represented by lag 1 autocorrelation coefficients at monthly and annual time scales. The NBC method was applied to the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Mk3.5 and MIROC 3.2 hires rainfall simulations for Australia. It was found that the nesting method worked well to correct means, standard deviations, and lag 1 autocorrelations when the biases in the raw GCM outputs were not too large. While the bias correction improves the representation of distributional and persistence attributes at the time scales considered, there is room for representation of longer-term persistence by extending to time scales longer than a year.

  7. Simulations of the mesoscale circulation of the Greenland-Iceland-Norwegian Seas

    NASA Technical Reports Server (NTRS)

    Heburn, George W.; Johnson, Clifford D.

    1995-01-01

    The Greenland, Iceland, and Norwegian Seas provide the only link between the North Atlantic and the Arctic Oceans. This is a very dynamic region, rich in mesoscale variability. A two-layer, hydrodynamic version of the Navy layered ocean model is used to simulate the mesoscale frontal features and associated current systems. The model is wind-driven using monthly mean wind stresses and inflow/outflow mass flux from the Arctic and North Atlantic Oceans. The current transports from the model results compare favorably with transport measurements from a number of observational experiments.

  8. Multidecadal North Atlantic sea surface temperature and Atlantic meridional overturning circulation variability in CMIP5 historical simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Liping; Wang, Chunzai

    2013-10-01

    In this paper, simulated variability of the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC) and their relationship has been investigated. For the first time, climate models of the Coupled Model Intercomparison Project phase 5 (CMIP5) provided to the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC-AR5) in historical simulations have been used for this purpose. The models show the most energetic variability on the multidecadal timescale band both with respect to the AMO and AMOC, but with a large model spread in both amplitude and frequency. The relationship between the AMO and AMOC in most of the models resembles the delayed advective oscillation proposed for the AMOC on multidecadal timescales. A speed up (slow down) of the AMOC is in favor of generating a warm (cold) phase of the AMO by the anomalous northward (southward) heat transport in the upper ocean, which reversely leads to a weakening (strengthening) of the AMOC through changes in the meridional density gradient after a delayed time of ocean adjustment. This suggests that on multidecadal timescales the AMO and AMOC are related and interact with each other.

  9. Intercomparison of interannual variability of the global 200-hPa circulation for AMIP simulations

    SciTech Connect

    Boyle, J.S.

    1998-10-01

    The 200-hPa divergence and streamfunction from the 30 models of the Atmospheric Model Intercomparison Project (AMIP) are compared. The data used are in the form of monthly averages and are filtered to a spatial resolution of T10, although the actual spatial resolution of the models varies from R15 to T42. The tools of the analysis are principal components analysis (PCA) and common principal components (CPC). These analyses are carried out on the 120 months of data with the climatological annual cycle removed and in the case of the streamfunction with the zonal average also removed. The AMIP period (1979--88) encompasses two El Nino-Southern Oscillation (ENSO) events (1982--83 and 1986--87), and as could be expected the ENSO characteristic response has a prominent impact in the model simulations.

  10. Interannual tropical rainfall variability in general circulation model simulations associated with the atmospheric model intercomparison project

    SciTech Connect

    Sperber, K.R.; Palmer, T.N.

    1996-11-01

    The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 models for the period 1979 - 88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each model. This subset of models also had a rainfall climatology that was in better agreement with observations, indicating a link between systematic model error and the ability to simulate interannual variations. A suite of six European Centre for Medium-Range Weather Forecasts (ECMWF) AMIP runs (differing only in their initial conditions) have also been examined. As observed, all-India rainfall was enhanced in 1988 relative to 1987 in each of these realizations. All-India rainfall variability during other years showed little or no predictability, possibly due to internal chaotic dynamics associated with intraseasonal monsoon fluctuations and/or unpredictable land surface process interactions. The interannual variations of Nordeste rainfall were best represented. The State University of New York at Albany /National Center for Atmospheric Research Genesis model was run in five initial condition realizations. In this model, the Nordeste rainfall variability was also best reproduced. However, for all regions the skill was less than that of the ECMWF model. The relationships of the all-India and Sahel rainfall/SST teleconnections with horizontal resolution, convection scheme closure, and numerics have been evaluated. 64 refs., 13 figs., 3 tabs.

  11. GEOSSAV: a simulation tool for subsurface applications

    NASA Astrophysics Data System (ADS)

    Regli, Christian; Rosenthaler, Lukas; Huggenberger, Peter

    2004-04-01

    Geostatistical Environment fOr Subsurface Simulation And Visualization (GEOSSAV) is a tool for the integration of hard and soft data into stochastic simulation and visualization of distributions of geological structures and hydrogeological properties in the subsurface. GEOSSAV, as an interface to selected geostatistical modules (bicalib, gamv, vargplt, and sisim) from the Geostatistical Software LIBrary, GSLIB (GSLIB: Geostatistical Software Library and User's Guide, 2nd Edition, Oxford University Press, Oxford, 1998, 369pp), can be used for data analysis, variogram computation of regularly or irregularly spaced data, and sequential indicator simulation of subsurface heterogeneities. Sequential indicator simulation, based on various kriging techniques (simple, ordinary, and Bayesian), is suitable for the simulation of continuous variables such as hydraulic conductivity of an aquifer or chemical concentrations at a contaminated site, and categorical variables which indicate the presence or absence of a particular lithofacies. The software integration platform and development environment of GEOSSAV is Tool command language (Tcl) with its graphical user interface, Toolkit (Tk), and a number of Tcl/Tk extensions. The standard Open Graphics Library application programming interface is used for rendering three-dimensional (3D) data distributions and for slicing perpendicular to the main coordinate axis. Export options for finite-difference groundwater models allow either files that characterize single model layers (which are saved in ASCII matrix format) or files that characterize the complete 3D flow model setup for MODFLOW-based groundwater simulation systems (which are saved in block-centered flow package files (User's documentation for MODFLOW-96, an update to the US Geological Survey modular finite-difference ground-water flow model, Geological Survey Open-File Report 96-485, Reston, VA, 1996, 56pp)). GEOSSAV can be used whenever stochastic solutions are preferred

  12. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    NASA Astrophysics Data System (ADS)

    Jöckel, P.; Tost, H.; Pozzer, A.; Brühl, C.; Buchholz, J.; Ganzeveld, L.; Hoor, P.; Kerkweg, A.; Lawrence, M. G.; Sander, R.; Steil, B.; Stiller, G.; Tanarhte, M.; Taraborrelli, D.; van Aardenne, J.; Lelieveld, J.

    2006-07-01

    The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model version up to 0.01 hPa was used at T42 resolution (~2.8 latitude and longitude) to simulate the lower and middle atmosphere. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. A Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998-2005. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce the Quasi-Biennial Oscillation and major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated accurately, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of interannual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request.

  13. Multiyear Simulations of the Martian Water Cycle with the Ames General Circulation Model

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Schaeffer, J. R.; Nelli, S. M.; Murphy, J. R.

    2003-01-01

    Mars atmosphere is carbon dioxide dominated with non-negligible amounts of water vapor and suspended dust particles. The atmospheric dust plays an important role in the heating and cooling of the planet through absorption and emission of radiation. Small dust particles can potentially be carried to great altitudes and affect the temperatures there. Water vapor condensing onto the dust grains can affect the radiative properties of both, as well as their vertical extent. The condensation of water onto a dust grain will change the grain s fall speed and diminish the possibility of dust obtaining high altitudes. In this capacity, water becomes a controlling agent with regard to the vertical distribution of dust. Similarly, the atmosphere s water vapor holding capacity is affected by the amount of dust in the atmosphere. Dust is an excellent green house catalyst; it raises the temperature of the atmosphere, and thus, its water vapor holding capacity. There is, therefore, a potentially significant interplay between the Martian dust and water cycles. Previous research done using global, 3-D computer modeling to better understand the Martian atmosphere treat the dust and the water cycles as two separate and independent processes. The existing Ames numerical model will be employed to simulate the relationship between the Martian dust and water cycles by actually coupling the two cycles. Water will condense onto the dust, allowing the particle's radiative characteristics, fall speeds, and as a result, their vertical distribution to change. Data obtained from the Viking, Mars Pathfinder, and especially the Mars Global Surveyor missions will be used to determine the accuracy of the model results.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  15. Application of LANDSAT TM images to assess circulation and dispersion in coastal lagoons

    NASA Technical Reports Server (NTRS)

    Kjerfve, B.; Jensen, J. R.; Magill, K. E.

    1986-01-01

    The main objectives are formulated around a four pronged work approach, consisting of tasks related to: image processing and analysis of LANDSAT thematic mapping; numerical modeling of circulation and dispersion; hydrographic and spectral radiation field sampling/ground truth data collection; and special efforts to focus the investigation on turbid coastal/estuarine fronts.

  16. Computational prediction of human salivary proteins from blood circulation and application to diagnostic biomarker identification.

    PubMed

    Wang, Jiaxin; Liang, Yanchun; Wang, Yan; Cui, Juan; Liu, Ming; Du, Wei; Xu, Ying

    2013-01-01

    Proteins can move from blood circulation into salivary glands through active transportation, passive diffusion or ultrafiltration, some of which are then released into saliva and hence can potentially serve as biomarkers for diseases if accurately identified. We present a novel computational method for predicting salivary proteins that come from circulation. The basis for the prediction is a set of physiochemical and sequence features we found to be discerning between human proteins known to be movable from circulation to saliva and proteins deemed to be not in saliva. A classifier was trained based on these features using a support-vector machine to predict protein secretion into saliva. The classifier achieved 88.56% average recall and 90.76% average precision in 10-fold cross-validation on the training data, indicating that the selected features are informative. Considering the possibility that our negative training data may not be highly reliable (i.e., proteins predicted to be not in saliva), we have also trained a ranking method, aiming to rank the known salivary proteins from circulation as the highest among the proteins in the general background, based on the same features. This prediction capability can be used to predict potential biomarker proteins for specific human diseases when coupled with the information of differentially expressed proteins in diseased versus healthy control tissues and a prediction capability for blood-secretory proteins. Using such integrated information, we predicted 31 candidate biomarker proteins in saliva for breast cancer. PMID:24324552

  17. Thermoresponsive release of viable microfiltrated Circulating Tumor Cells (CTCs) for precision medicine applications.

    PubMed

    Ao, Zheng; Parasido, Erika; Rawal, Siddarth; Williams, Anthony; Schlegel, Richard; Liu, Stephen; Albanese, Chris; Cote, Richard J; Agarwal, Ashutosh; Datar, Ram H

    2015-11-21

    Stimulus responsive release of Circulating Tumor Cells (CTCs), with high recovery rates from their capture platform, is highly desirable for off-chip analyses. Here, we present a temperature responsive polymer coating method to achieve both release as well as culture of viable CTCs captured from patient blood samples. PMID:26426331

  18. 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.

  19. Application of Satellite Altimetry to Ocean Circulation Studies: 1987-1994

    NASA Technical Reports Server (NTRS)

    Fu, L. -L.; Cheney, R. E.

    1994-01-01

    Altimetric measurement of the height of the sea surface from space provides global observation of the world's oceans. The last eight years have witnessed a rapid growth in the use of altimetry data from the study of the ocean circulations, thanks to the multiyear data from the Geosat Mission.

  20. Properties of Tangential and Cyclic Polygons: An Application of Circulant Matrices

    ERIC Educational Resources Information Center

    Leung, Allen; Lopez-Real, Francis

    2003-01-01

    In this paper, the properties of tangential and cyclic polygons proposed by Lopez-Real are proved rigorously using the theory of circulant matrices. In particular, the concepts of slippable tangential polygons and conformable cyclic polygons are defined. It is shown that an n-sided tangential (or cyclic) polygon P[subscript n] with n even is…

  1. Importance of the Annual Cycles of SST and Solar Irradiance for Circulation and Rainfall: A Climate Model Simulation Study

    NASA Technical Reports Server (NTRS)

    Sud, Yogesh C.; Lau, William K. M.; Walker, G. K.; Mehta, V. M.

    2001-01-01

    Annual cycle of climate and precipitation is related to annual cycle of sunshine and sea-surface temperatures. Understanding its behavior is important for the welfare of humans worldwide. For example, failure of Asian monsoons can cause widespread famine and grave economic disaster in the subtropical regions. For centuries meteorologists have struggled to understand the importance of the summer sunshine and associated heating and the annual cycle of sea-surface temperatures (SSTs) on rainfall in the subtropics. Because the solar income is pretty steady from year to year, while SSTs depict large interannual variability as consequence of the variability of ocean dynamics, the influence of SSTs on the monsoons are better understood through observational and modeling studies whereas the relationship of annual rainfall to sunshine remains elusive. However, using NASA's state of the art climate model(s) that can generate realistic climate in a computer simulation, one can answer such questions. We asked the question: if there was no annual cycle of the sunshine (and its associated land-heating) or the SST and its associated influence on global circulation, what will happen to the annual cycle of monsoon rains? By comparing the simulation of a 4-year integration of a baseline Control case with two parallel anomaly experiments: 1) with annual mean solar and 2) with annual mean sea-surface temperatures, we were able to draw the following conclusions: (1) Tropical convergence zone and rainfall which moves with the Sun into the northern and southern hemispheres, specifically over the Indian, African, South American and Australian regions, is strongly modulated by the annual cycles of SSTs as well as solar forcings. The influence of the annual cycle of solar heating over land, however, is much stronger than the corresponding SST influence for almost all regions, particularly the subtropics; (2) The seasonal circulation patterns over the vast land-masses of the Northern

  2. The variability, structure and energy conversion of the northern hemisphere traveling waves simulated in a Mars general circulation model

    NASA Astrophysics Data System (ADS)

    Wang, Huiqun; Toigo, Anthony D.

    2016-06-01

    Investigations of the variability, structure and energetics of the m = 1-3 traveling waves in the northern hemisphere of Mars are conducted with the MarsWRF general circulation model. Using a simple, annually repeatable dust scenario, the model reproduces many general characteristics of the observed traveling waves. The simulated m = 1 and m = 3 traveling waves show large differences in terms of their structures and energetics. For each representative wave mode, the geopotential signature maximizes at a higher altitude than the temperature signature, and the wave energetics suggests a mixed baroclinic-barotropic nature. There is a large contrast in wave energetics between the near-surface and higher altitudes, as well as between the lower latitudes and higher latitudes at high altitudes. Both barotropic and baroclinic conversions can act as either sources or sinks of eddy kinetic energy. Band-pass filtered transient eddies exhibit strong zonal variations in eddy kinetic energy and various energy transfer terms. Transient eddies are mainly interacting with the time mean flow. However, there appear to be non-negligible wave-wave interactions associated with wave mode transitions. These interactions include those between traveling waves and thermal tides and those among traveling waves.

  3. Eddy-resolving simulations of the Fimbul Ice Shelf cavity circulation: Basal melting and exchange with open ocean

    NASA Astrophysics Data System (ADS)

    Hattermann, T.; Smedsrud, L. H.; Nøst, O. A.; Lilly, J. M.; Galton-Fenzi, B. K.

    2014-10-01

    Melting at the base of floating ice shelves is a dominant term in the overall Antarctic mass budget. This study applies a high-resolution regional ice shelf/ocean model, constrained by observations, to (i) quantify present basal mass loss at the Fimbul Ice Shelf (FIS); and (ii) investigate the oceanic mechanisms that govern the heat supply to ice shelves in the Eastern Weddell Sea. The simulations confirm the low melt rates suggested by observations and show that melting is primarily determined by the depth of the coastal thermocline, regulating deep ocean heat fluxes towards the ice. Furthermore, the uneven distribution of ice shelf area at different depths modulates the melting response to oceanic forcing, causing the existence of two distinct states of melting at the FIS. In the simulated present-day state, only small amounts of Modified Warm Deep Water enter the continental shelf, and ocean temperatures beneath the ice are close to the surface freezing point. The basal mass loss in this so-called state of “shallow melting” is mainly controlled by the seasonal inflow of solar-heated surface water affecting large areas of shallow ice in the upper part of the cavity. This is in contrast to a state of “deep melting”, in which the thermocline rises above the shelf break depth, establishing a continuous inflow of Warm Deep Water towards the deep ice. The transition between the two states is found to be determined by a complex response of the Antarctic Slope Front overturning circulation to varying climate forcings. A proper representation of these frontal dynamics in climate models will therefore be crucial when assessing the evolution of ice shelf basal melting along this sector of Antarctica.

  4. Large eddy simulation applications in gas turbines.

    PubMed

    Menzies, Kevin

    2009-07-28

    The gas turbine presents significant challenges to any computational fluid dynamics techniques. The combination of a wide range of flow phenomena with complex geometry is difficult to model in the context of Reynolds-averaged Navier-Stokes (RANS) solvers. We review the potential for large eddy simulation (LES) in modelling the flow in the different components of the gas turbine during a practical engineering design cycle. We show that while LES has demonstrated considerable promise for reliable prediction of many flows in the engine that are difficult for RANS it is not a panacea and considerable application challenges remain. However, for many flows, especially those dominated by shear layer mixing such as in combustion chambers and exhausts, LES has demonstrated a clear superiority over RANS for moderately complex geometries although at significantly higher cost which will remain an issue in making the calculations relevant within the design cycle. PMID:19531505

  5. Simulation Code Development and Its Applications

    NASA Astrophysics Data System (ADS)

    Li, Zenghai

    2015-10-01

    Under the support of the U.S. DOE SciDAC program, SLAC has been developing a suite of 3D parallel finite-element codes aimed at high-accuracy, high-fidelity electromagnetic and beam physics simulations for the design and optimization of next-generation particle accelerators. Running on the latest supercomputers, these codes have made great strides in advancing the state of the art in applied math and computer science at the petascale that enable the integrated modeling of electromagnetics, self-consistent Particle-In-Cell (PIC) particle dynamics as well as thermal, mechanical, and multi-physics effects. This paper will present the latest development and application of ACE3P to a wide range of accelerator projects.

  6. Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings, such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

  7. Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings. Such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

  8. Seasonal Simulations of the Planetary Boundary Layer and Boundary-Layer Stratocumulus Clouds with a General Circulation Model.

    NASA Astrophysics Data System (ADS)

    Randall, David A.; Abeles, James A.; Corsetti, Thomas G.

    1985-04-01

    The UCLA general circulation model (GCM) has been used to simulate the seasonally varying planetary boundary layer (PBL), as well as boundary-layer stratus and stratocumulus clouds. The PBL depth is a prognostic variable of the GCM, incorporated through the use of a vertical coordinate system in which the PBL is identified with the lowest model layer.Stratocumulus clouds are assumed to occur whenever the upper portion of the PBL becomes saturated, provided that the cloud-top entrainment instability does not occur. As indicated by Arakawa and Schubert, cumulus clouds are assumed to originate at the PBL top, and tend to make the PBL shallow by drawing on its mass.Results are presented from a three-year simulation, starting from a 31 December initial condition obtained from an earlier run with a different version of the model. The simulated seasonally varying climates of the boundary layer and free troposphere are realistic. The observed geographical and seasonal variations of stratocumulus cloudiness are fairly well simulated. The simulation of the stratocumulus clouds associated with wintertime cold-air outbreaks is particularly realistic. Examples are given of individual events. The positions of the subtropical marine stratocumulus regimes are realistically simulated, although their observed frequency of occurrence is seriously underpredicted. The observed summertime abundance of Arctic stratus clouds is also underpredicted.In the GCM results, the layer cloud instability appears to limit the extent of the marine subtropical stratocumulus regimes. The instability also frequently occurs in association with cumulus convection over land.Cumulus convection acts as a very significant sink of PBL mass throughout the tropics, and over the midlatitude continents in summer.Three experiments have been performed to investigate the sensitivity of the GCM results to aspects of the PBL and stratocumulus parameterizations. For all three experiments, the model was started from 1

  9. Large-Eddy Simulation of Aeroacoustic Applications

    NASA Technical Reports Server (NTRS)

    Pruett, C. David; Sochacki, James S.

    1999-01-01

    This report summarizes work accomplished under a one-year NASA grant from NASA Langley Research Center (LaRC). The effort culminates three years of NASA-supported research under three consecutive one-year grants. The period of support was April 6, 1998, through April 5, 1999. By request, the grant period was extended at no-cost until October 6, 1999. Its predecessors have been directed toward adapting the numerical tool of large-eddy simulation (LES) to aeroacoustic applications, with particular focus on noise suppression in subsonic round jets. In LES, the filtered Navier-Stokes equations are solved numerically on a relatively coarse computational grid. Residual stresses, generated by scales of motion too small to be resolved on the coarse grid, are modeled. Although most LES incorporate spatial filtering, time-domain filtering affords certain conceptual and computational advantages, particularly for aeroacoustic applications. Consequently, this work has focused on the development of subgrid-scale (SGS) models that incorporate time-domain filters.

  10. Characterization of Jupiter's Deep Circulation and Static Stability through Wide Channel Numerical Simulations of the Dynamics and Interactions of Southern Midlatitudes Vortices

    NASA Astrophysics Data System (ADS)

    Morales-Juberias, Raul; Dowling, T. E.

    2012-10-01

    Previous studies have shown that the observed features and dynamics of Jovian vortices are sensitive to the underlying environmental structure of Jupiter’s atmosphere, in particular to the vertical wind shear and the static stability, and that forward modeling techniques can be successfully used to eliminate a large range of possibilities in a self-consistent manner and hence constrain the atmospheric structure below the cloud regions (Youseff and Marcus 2003, Morales-Juberias et al. 2005). However, these studies have generally been done on a narrow latitude-band basis (˜15°). Here we present wide channel simulations (˜40°) of two major meteorological events observed in the southern atmosphere of Jupiter involving the interaction of the Great Red Spot (GRS) with other nearby vortices. Namely, the spots associated with the recirculation of the South Tropical Disturbance of 1979 (Smith et al. 1979) and the White Ovals (WOS) in 2000 when ovals BE and FA merged to form BA (Sanchez-Lavega et al. 2001). By studying these two events using wide channel simulations, not unlike the strategy used in terrestrial synoptic meteorology, we show that we can gain new insights into the patterns governing Jupiter's global circulations, drawing a coherent picture of the vertical structure of the atmosphere for the whole southern mid-latitudinal regions of Jupiter over time. In particular, we find that the model output best captures the dynamics of the individual vortices and the morphology of their interactions when the deformation length in this region is like that derived by Read et al. 2006 and the deep winds vary following a dependence like that derived by Dowling 1995 in which the westward jets remain constant with depth but the eastward jets increase with depth. Computational resources were provided by the New Mexico Computing Applications Center and NMT. This work was supported by PATM grants NNX08AE91G and NNX08AE64G.

  11. Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

    NASA Astrophysics Data System (ADS)

    Panther, Chad C.

    Vertical Axis Wind Turbines (VAWTs) have experienced a renewed interest in development for urban, remote, and offshore applications. Past research has shown that VAWTs cannot compete with Horizontals Axis Wind Turbines (HAWTs) in terms of energy capture efficiency. VAWT performance is plagued by dynamic stall (DS) effects at low tip-speed ratios (lambda), where each blade pitches beyond static stall multiple times per revolution. Furthermore, for lambda<2, blades operate outside of stall during over 70% of rotation. However, VAWTs offer many advantages such as omnidirectional operation, ground proximity of generator, lower sound emission, and non-cantilevered blades with longer life. Thus, mitigating dynamic stall and improving VAWT blade aerodynamics for competitive power efficiency has been a popular research topic in recent years and the directive of this study. Past research at WVU focused on the addition of circulation control (CC) technology to improve VAWT aerodynamics and expand the operational envelope. A novel blade design was generated from the augmentation of a NACA0018 airfoil to include CC capabilities. Static wind tunnel data was collected for a range of steady jet momentum coefficients (0.01≤ Cmu≤0.10) for analytical vortex model performance projections. Control strategies were developed to optimize CC jet conditions throughout rotation, resulting in improved power output for 2≤lambda≤5. However, the pumping power required to produce steady CC jets reduced net power gains of the augmented turbine by approximately 15%. The goal of this work was to investigate pulsed CC jet actuation to match steady jet performance with reduced mass flow requirements. To date, no experimental studies have been completed to analyze pulsed CC performance on a pitching airfoil. The research described herein details the first study on the impact of steady and pulsed jet CC on pitching VAWT blade aerodynamics. Both numerical and experimental studies were

  12. Application of circulation classifications from the COST733 collection to the detection of solar and geomagnetic effects on tropospheric circulation over Europe in winter

    NASA Astrophysics Data System (ADS)

    Huth, Radan; Cahynová, Monika; Kyselý, Jan

    2010-05-01

    Many studies of circulation classifications are biased by the fact that they are based on a single classification only; that is, their results are affected by the properties of a particular classification to an unknown extent. A large number of circulation classifications produced and collected in the COST733 database allows such a bias to be removed. As an example, we examine effects of solar activity variations on the frequency of circulation types, making use of more than sixty objective classifications for each of 12 domains, defined over Europe. To determine the solar effects, winter months (December to March) are divided into three classes according to the mean monthly solar activity, within which the frequencies of occurrence of circulation types are calculated. Circulation types coming from any classification with significant differences in frequency between high and low solar activity are identified. Current results generally confirm results of a previous study based on a single classification only (subjective Hess-Brezowsky) that (a) westerly types are more frequent under high than low solar activity; (b) northerly types are more frequent under low than high activity, and (iii) easterly and anticyclonic types are more frequent under low than moderate solar activity; the opposite holds for cyclonic types. The research is supported by the Ministry of Education, Youth, and Sports of the Czech Republic under contract OC115 and the Grant Agency of the Czech Academy of Sciences, project A300420805.

  13. Methods of sound simulation and applications in flight simulators

    NASA Technical Reports Server (NTRS)

    Gaertner, K. P.

    1980-01-01

    An overview of methods for electronically synthesizing sounds is presented. A given amount of hardware and computer capacity places an upper limit on the degree and fidelity of realism of sound simulation which is attainable. Good sound realism for aircraft simulators can be especially expensive because of the complexity of flight sounds and their changing patterns through time. Nevertheless, the flight simulator developed at the Research Institute for Human Engineering, West Germany, shows that it is possible to design an inexpensive sound simulator with the required acoustic properties using analog computer elements. The characteristics of the sub-sound elements produced by this sound simulator for take-off, cruise and approach are discussed.

  14. A new application of a finite element heat and mass transfer numerical modeling code (FEHM) to heat and fluid circulation in lava domes

    NASA Astrophysics Data System (ADS)

    Ball, J. L.; Stauffer, P. H.; Calder, E. S.

    2012-12-01

    those properties to dome material regions. Further modifications to the dome geometry and material properties were made to better simulate specific lava domes, including Santiaguito in Guatemala and Unzen in Japan. Preliminary results suggest that FEHM produces a reasonable simulation of fluid movement in a saturated, post-eruptive (cooling) lava dome, with recharge from meteoric water, over periods of years to decades. This model setup is applicable to the older lava domes at Santiaguito and the dome at Unzen. The simulations presented were restricted at this point to lower temperature materials (< 250°C) to avoid computationally more intensive phase change. A grid based on the geometry of the older Santiaguito lava domes has produced temperature gradients and fluid flow paths in a similar location to hot springs at the real dome complex.

  15. A revised linear ozone photochemistry parameterization for use in transport and general circulation models: multi-annual simulations

    NASA Astrophysics Data System (ADS)

    Cariolle, D.; Teyssèdre, H.

    2007-01-01

    This article describes the validation of a linear parameterization of the ozone photochemistry for use in upper tropospheric and stratospheric studies. The present work extends a previously developed scheme by improving the 2D model used to derive the coefficients of the parameterization. The chemical reaction rates are updated from a compilation that includes recent laboratory works. Furthermore, the polar ozone destruction due to heterogeneous reactions at the surface of the polar stratospheric clouds is taken into account as a function of the stratospheric temperature and the total chlorine content. Two versions of the parameterization are tested. The first one only requires the resolution of a continuity equation for the time evolution of the ozone mixing ratio, the second one uses one additional equation for a cold tracer. The parameterization has been introduced into the chemical transport model MOCAGE. The model is integrated with wind and temperature fields from the ECMWF operational analyses over the period 2000-2004. Overall, the results show a very good agreement between the modelled ozone distribution and the Total Ozone Mapping Spectrometer (TOMS) satellite data and the "in-situ" vertical soundings. During the course of the integration the model does not show any drift and the biases are generally small. The model also reproduces fairly well the polar ozone variability, with notably the formation of "ozone holes" in the southern hemisphere with amplitudes and seasonal evolutions that follow the dynamics and time evolution of the polar vortex. The introduction of the cold tracer further improves the model simulation by allowing additional ozone destruction inside air masses exported from the high to the mid-latitudes, and by maintaining low ozone contents inside the polar vortex of the southern hemisphere over longer periods in spring time. It is concluded that for the study of climatic scenarios or the assimilation of ozone data, the present

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

    PubMed

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

    2012-06-01

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

  17. Streamflow changes in the Sierra Nevada, California, simulated using a statistically downscaled general circulation model scenario of climate change

    USGS Publications Warehouse

    Wilby, Robert L.; Dettinger, Michael D.

    2000-01-01

    Simulations of future climate using general circulation models (GCMs) suggest that rising concentrations of greenhouse gases may have significant consequences for the global climate. Of less certainty is the extent to which regional scale (i.e., sub-GCM grid) environmental processes will be affected. In this chapter, a range of downscaling techniques are critiqued. Then a relatively simple (yet robust) statistical downscaling technique and its use in the modelling of future runoff scenarios for three river basins in the Sierra Nevada, California, is described. This region was selected because GCM experiments driven by combined greenhouse-gas and sulphate-aerosol forcings consistently show major changes in the hydro-climate of the southwest United States by the end of the 21st century. The regression-based downscaling method was used to simulate daily rainfall and temperature series for streamflow modelling in three Californian river basins under current-and future-climate conditions. The downscaling involved just three predictor variables (specific humidity, zonal velocity component of airflow, and 500 hPa geopotential heights) supplied by the U.K. Meteorological Office couple ocean-atmosphere model (HadCM2) for the grid point nearest the target basins. When evaluated using independent data, the model showed reasonable skill at reproducing observed area-average precipitation, temperature, and concomitant streamflow variations. Overall, the downscaled data resulted in slight underestimates of mean annual streamflow due to underestimates of precipitation in spring and positive temperature biases in winter. Differences in the skill of simulated streamflows amongst the three basins were attributed to the smoothing effects of snowpack on streamflow responses to climate forcing. The Merced and American River basins drain the western, windward slope of the Sierra Nevada and are snowmelt dominated, whereas the Carson River drains the eastern, leeward slope and is a mix of

  18. Genetic data simulators and their applications: an overview

    PubMed Central

    Peng, Bo; Chen, Huann-Sheng; Mechanic, Leah E.; Racine, Ben; Clarke, John; Gillanders, Elizabeth; Feuer, Eric J.

    2016-01-01

    Computer simulations have played an indispensable role in the development and application of statistical models and methods for genetic studies across multiple disciplines. The need to simulate complex evolutionary scenarios and pseudo-datasets for various studies has fueled the development of dozens of computer programs with varying reliability, performance, and application areas. To help researchers compare and choose the most appropriate simulators for their studies, we have created the Genetic Simulation Resources (GSR) website, which allows authors of simulation software to register their applications and describe them with more than 160 defined attributes. This article summarizes the properties of 93 simulators currently registered at GSR and provides an overview of the development and applications of genetic simulators. Unlike other review articles that address technical issues or compare simulators for particular application areas, we focus on software development, maintenance, and features of simulators, often from a historical perspective. Publications that cite these simulators are used to summarize both the applications of genetic simulations and the utilization of simulators. PMID:25504286

  19. Genetic data simulators and their applications: an overview.

    PubMed

    Peng, Bo; Chen, Huann-Sheng; Mechanic, Leah E; Racine, Ben; Clarke, John; Gillanders, Elizabeth; Feuer, Eric J

    2015-01-01

    Computer simulations have played an indispensable role in the development and applications of statistical models and methods for genetic studies across multiple disciplines. The need to simulate complex evolutionary scenarios and pseudo-datasets for various studies has fueled the development of dozens of computer programs with varying reliability, performance, and application areas. To help researchers compare and choose the most appropriate simulators for their studies, we have created the genetic simulation resources (GSR) website, which allows authors of simulation software to register their applications and describe them with more than 160 defined attributes. This article summarizes the properties of 93 simulators currently registered at GSR and provides an overview of the development and applications of genetic simulators. Unlike other review articles that address technical issues or compare simulators for particular application areas, we focus on software development, maintenance, and features of simulators, often from a historical perspective. Publications that cite these simulators are used to summarize both the applications of genetic simulations and the utilization of simulators. PMID:25504286

  20. Simulation of short-term pressure regulation during the tilt test in a coupled 3D-0D closed-loop model of the circulation.

    PubMed

    Lau, Kevin D; Figueroa, C Alberto

    2015-08-01

    Short-term fluctuations in arterial pressures arising from normal physiological function are buffered by a negative feedback system known as the arterial baroreflex. Initiated by altered biomechanical stretch in the vessel wall, the baroreflex coordinates a systemic response that alters heart rate, cardiac contractility and peripheral vessel vasoconstriction. In this work, a coupled 3D-0D formulation for the short-term pressure regulation of the systemic circulation is presented. Including the baroreflex feedback mechanisms, a patient-specific model of the large arteries is subjected to a simulated head up tilt test. Comparative simulations with and without baroreflex control highlight the critical role that the baroreflex has in regulating variations in pressures within the systemic circulation. PMID:25567754

  1. Narrowing of the Upwelling Branch of the Brewer-Dobson Circulation and Hadley Cell in Chemistry-Climate Model Simulations of the 21st Century

    NASA Technical Reports Server (NTRS)

    Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn

    2010-01-01

    Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley rising branch. Model results suggest that the narrowing of the Hadley cell ascent is also eddy-driven.

  2. Narrowing of the Upwelling Branch of the Brewer-Dobson Circulation and Hadley Cell in Chemistry-Climate Model Simulations of the 21st Century

    NASA Technical Reports Server (NTRS)

    Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn

    2010-01-01

    Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley cell's rising branch. Model results suggest that eddy forcing may also play a part in the narrowing of the rising branch of the Hadley cell.

  3. Circulating pump for high-pressure and high-temperature applications

    NASA Astrophysics Data System (ADS)

    Peleties, Fotos; Martin Trusler, J. P.; Goodwin, Anthony R. H.; Maitland, Geoffrey C.

    2005-10-01

    A high-pressure high-temperature magnetic circulating pump is described. The design is based on the concept of contactless bidirectional pumping action. This pump can deliver a continuous flow at temperatures up to 175°C and pressures up to 2000bars. Wetted parts are fabricated from stainless steels, there are no elastomeric seals or lubricants required, and the pump can be physically mobile during operation. Tests with toluene at ambient temperature and pressure showed that volumetric flow rates of up to 320cm3 min-1 and pressure heads of up to 2.2bars could be achieved.

  4. Aerosol-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

    NASA Astrophysics Data System (ADS)

    Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

    2012-02-01

    We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the roles of different forcing agents as drivers of summer rainfall trends in the Australasian region. Our results suggest that anthropogenic aerosols have contributed to the observed multi-decadal rainfall increase over north-western Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we performed multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. We also compare a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). Simulated aerosol-induced rainfall trends over the Indo-Pacific region for austral summer and boreal summer show a distinct contrast. In boreal summer, there is a southward shift of equatorial rainfall, consistent with the idea that anthropogenic aerosols have suppressed Asian monsoonal rainfall, and caused a southward shift of the local Hadley circulation. In austral summer, the aerosol-induced response more closely resembles a westward shift and strengthening of the upward branch of the Walker circulation, rather than a coherent southward shift of regional tropical rainfall. Thus the mechanism by which anthropogenic aerosols may affect Australian summer rainfall is unclear. Focusing on summer rainfall trends over north-western Australia (NWA), we find that CSIRO-Mk3.6 simulates a strong rainfall decrease in RCP4.5, whereas simulated trends in HIST are weak and insignificant during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol

  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. Microcomputer-based automatic regulation of extracorporeal circulation: a trial for the application of fuzzy inference.

    PubMed

    Anbe, J; Tobi, T; Nakajima, H; Akasaka, T; Okinaga, K

    1992-10-01

    Since its establishment many researchers have been trying to automate the process of extracorporeal circulation (ECC). We developed a preliminary experimental model of an automatic regulatory system for ECC. The purpose of the system was to regulate basic hemodynamic parameters such as pump flow and withdrawal blood volume. It was divided into three main components: data sampling unit, central processing unit, and controlling unit. Based on this model we were able to achieve autoregulation of ECC using minimum configuration; however, the system lacked smoothness. This was partly because it was based on a "static" regulation system which used conditional statements having multiple parameters. In this study, we applied fuzzy logic to the former model to achieve more accurate and reliable regulation. We report experimental results for the new system and compare the data between clinical circulation in 13 infants (mean body weight, 13.32 +/- 5.99 kg) and experimental regulation in 7 mongrel dogs (mean body weight, 11.9 +/- 2.53 kg). The comparative study revealed no statistical difference between the two groups. This result suggests that the automatic regulation of ECC may be an alternative to manual operation by a professional perfusionist in the near future. PMID:10078307

  7. On the reduced lifetime of nitrous oxide due to climate change induced acceleration of the Brewer-Dobson circulation as simulated by the MPI Earth System Model

    NASA Astrophysics Data System (ADS)

    Kracher, D.; Manzini, E.; Reick, C. H.; Schultz, M. G.; Stein, O.

    2014-12-01

    Greenhouse gas induced climate change will modify the physical conditions of the atmosphere. One of the projected changes is an acceleration of the Brewer-Dobson circulation in the stratosphere, as it has been shown in many model studies. This change in the stratospheric circulation consequently bears an effect on the transport and distribution of atmospheric components such as N2O. Since N2O is involved in ozone destruction, a modified distribution of N2O can be of importance for ozone chemistry. N2O is inert in the troposphere and decays only in the stratosphere. Thus, changes in the exchange between troposphere and stratosphere can also affect the stratospheric sink of N2O, and consequently its atmospheric lifetime. N2O is a potent greenhouse gas with a global warming potential of currently approximately 300 CO2-equivalents in a 100-year perspective. A faster decay in atmospheric N2O mixing ratios, i.e. a decreased atmospheric lifetime of N2O, will also reduce its global warming potential. In order to assess the impact of climate change on atmospheric circulation and implied effects on the distribution and lifetime of atmospheric N2O, we apply the Max Planck Institute Earth System Model, MPI-ESM. MPI-ESM consists of the atmospheric general circulation model ECHAM, the land surface model JSBACH, and MPIOM/HAMOCC representing ocean circulation and ocean biogeochemistry. Prognostic atmospheric N2O concentrations in MPI-ESM are determined by land N2O emissions, ocean-atmosphere N2O exchange and atmospheric tracer transport. As stratospheric chemistry is not explicitly represented in MPI-ESM, stratospheric decay rates of N2O are prescribed from a MACC MOZART simulation. Increasing surface temperatures and CO2 concentrations in the stratosphere impact atmospheric circulation differently. Thus, we conduct a series of transient runs with the atmospheric model of MPI-ESM to isolate different factors governing a shift in atmospheric circulation. From those transient

  8. Application of control theory to dynamic systems simulation

    NASA Technical Reports Server (NTRS)

    Auslander, D. M.; Spear, R. C.; Young, G. E.

    1982-01-01

    The application of control theory is applied to dynamic systems simulation. Theory and methodology applicable to controlled ecological life support systems are considered. Spatial effects on system stability, design of control systems with uncertain parameters, and an interactive computing language (PARASOL-II) designed for dynamic system simulation, report quality graphics, data acquisition, and simple real time control are discussed.

  9. Application of simulation models for the optimization of business processes

    NASA Astrophysics Data System (ADS)

    Jašek, Roman; Sedláček, Michal; Chramcov, Bronislav; Dvořák, Jiří

    2016-06-01

    The paper deals with the applications of modeling and simulation tools in the optimization of business processes, especially in solving an optimization of signal flow in security company. As a modeling tool was selected Simul8 software that is used to process modeling based on discrete event simulation and which enables the creation of a visual model of production and distribution processes.

  10. A revised linear ozone photochemistry parameterization for use in transport and general circulation models: multi-annual simulations

    NASA Astrophysics Data System (ADS)

    Cariolle, D.; Teyssèdre, H.

    2007-05-01

    This article describes the validation of a linear parameterization of the ozone photochemistry for use in upper tropospheric and stratospheric studies. The present work extends a previously developed scheme by improving the 2-D model used to derive the coefficients of the parameterization. The chemical reaction rates are updated from a compilation that includes recent laboratory work. Furthermore, the polar ozone destruction due to heterogeneous reactions at the surface of the polar stratospheric clouds is taken into account as a function of the stratospheric temperature and the total chlorine content. Two versions of the parameterization are tested. The first one only requires the solution of a continuity equation for the time evolution of the ozone mixing ratio, the second one uses one additional equation for a cold tracer. The parameterization has been introduced into the chemical transport model MOCAGE. The model is integrated with wind and temperature fields from the ECMWF operational analyses over the period 2000-2004. Overall, the results from the two versions show a very good agreement between the modelled ozone distribution and the Total Ozone Mapping Spectrometer (TOMS) satellite data and the "in-situ" vertical soundings. During the course of the integration the model does not show any drift and the biases are generally small, of the order of 10%. The model also reproduces fairly well the polar ozone variability, notably the formation of "ozone holes" in the Southern Hemisphere with amplitudes and a seasonal evolution that follow the dynamics and time evolution of the polar vortex. The introduction of the cold tracer further improves the model simulation by allowing additional ozone destruction inside air masses exported from the high to the mid-latitudes, and by maintaining low ozone content inside the polar vortex of the Southern Hemisphere over longer periods in spring time. It is concluded that for the study of climate scenarios or the assimilation of