COCOA: Simulating Observations of Star Cluster Simulations
NASA Astrophysics Data System (ADS)
Askar, Abbas; Giersz, Mirek; Pych, Wojciech; Dalessandro, Emanuele
2017-03-01
COCOA (Cluster simulatiOn Comparison with ObservAtions) creates idealized mock photometric observations using results from numerical simulations of star cluster evolution. COCOA is able to present the output of realistic numerical simulations of star clusters carried out using Monte Carlo or N-body codes in a way that is useful for direct comparison with photometric observations. The code can simulate optical observations from simulation snapshots in which positions and magnitudes of objects are known. The parameters for simulating the observations can be adjusted to mimic telescopes of various sizes. COCOA also has a photometry pipeline that can use standalone versions of DAOPHOT (ascl:1104.011) and ALLSTAR to produce photometric catalogs for all observed stars.
Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations
NASA Astrophysics Data System (ADS)
Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr
2016-08-01
We present analysis of global three-dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single-species model with simplified neutral-plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self-consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate.
Tullis, Terry. E.; Richards-Dinger, Keith B.; Barall, Michael; Dieterich, James H.; Field, Edward H.; Heien, Eric M.; Kellogg, Louise; Pollitz, Fred F.; Rundle, John B.; Sachs, Michael K.; Turcotte, Donald L.; Ward, Steven N.; Yikilmaz, M. Burak
2012-01-01
In order to understand earthquake hazards we would ideally have a statistical description of earthquakes for tens of thousands of years. Unfortunately the ∼100‐year instrumental, several 100‐year historical, and few 1000‐year paleoseismological records are woefully inadequate to provide a statistically significant record. Physics‐based earthquake simulators can generate arbitrarily long histories of earthquakes; thus they can provide a statistically meaningful history of simulated earthquakes. The question is, how realistic are these simulated histories? This purpose of this paper is to begin to answer that question. We compare the results between different simulators and with information that is known from the limited instrumental, historic, and paleoseismological data.As expected, the results from all the simulators show that the observational record is too short to properly represent the system behavior; therefore, although tests of the simulators against the limited observations are necessary, they are not a sufficient test of the simulators’ realism. The simulators appear to pass this necessary test. In addition, the physics‐based simulators show similar behavior even though there are large differences in the methodology. This suggests that they represent realistic behavior. Different assumptions concerning the constitutive properties of the faults do result in enhanced capabilities of some simulators. However, it appears that the similar behavior of the different simulators may result from the fault‐system geometry, slip rates, and assumed strength drops, along with the shared physics of stress transfer.This paper describes the results of running four earthquake simulators that are described elsewhere in this issue of Seismological Research Letters. The simulators ALLCAL (Ward, 2012), VIRTCAL (Sachs et al., 2012), RSQSim (Richards‐Dinger and Dieterich, 2012), and ViscoSim (Pollitz, 2012) were run on our most recent all‐California fault
AMR Studies of Star Formation: Simulations and Simulated Observations
NASA Astrophysics Data System (ADS)
Offner, Stella; McKee, C. F.; Klein, R. I.
2009-01-01
Molecular clouds are typically observed to be approximately virialized with gravitational and turbulent energy in balance, yielding a star formation rate of a few percent. The origin and characteristics of the observed supersonic turbulence are poorly understood, and without continued energy injection the turbulence is predicted to decay within a cloud dynamical time. Recent observations and analytic work have suggested a strong connection between the initial stellar mass function, the core mass function, and turbulence characteristics. The role of magnetic fields in determining core lifetimes, shapes, and kinematic properties remains hotly debated. Simulations are a formidable tool for studying the complex process of star formation and addressing these puzzles. I present my results modeling low-mass star formation using the ORION adaptive mesh refinement (AMR) code. I investigate the properties of forming cores and protostars in simulations in which the turbulence is driven to maintain virial balance and where it is allowed to decay. I will discuss simulated observations of cores in dust emission and in molecular tracers and compare to observations of local star-forming clouds. I will also present results from ORION cluster simulations including flux-limited diffusion radiative transfer and show that radiative feedback, even from low-mass stars, has a significant effect on core fragmentation, disk properties, and the IMF. Finally, I will discuss the new simulation frontier of AMR multigroup radiative transfer.
Observing Galaxy Mergers in Simulations
NASA Astrophysics Data System (ADS)
Snyder, Gregory
2018-01-01
I will describe results on mergers and morphology of distant galaxies. By mock-observing 3D cosmological simulations, we aim to contrast theory with data, design better diagnostics of physical processes, and examine unexpected signatures of galaxy formation. Recently, we conducted mock surveys of the Illustris Simulations to learn how mergers would appear in deep HST and JWST surveys. With this approach, we reconciled merger rates estimated using observed close galaxy pairs with intrinsic merger rates predicted by theory. This implies that the merger-pair observability time is probably shorter in the early universe, and therefore that major mergers are more common than implied by the simplest arguments. Further, we show that disturbance-based diagnostics of late-stage mergers can be improved significantly by combining multi-dimensional image information with simulated merger identifications to train automated classifiers. We then apply these classifiers to real measurements from the CANDELS fields, recovering a merger fraction increasing with redshift in broad agreement with pair fractions and simulations, and with statistical errors smaller by a factor of two than classical morphology estimators. This emphasizes the importance of using robust training sets, including cosmological simulations and multidimensional data, for interpreting observed processes in galaxy evolution.
NASA Astrophysics Data System (ADS)
Palmroth, Minna; Rami, Vainio; Archer, Martin; Hietala, Heli; Afanasiev, Alexandr; Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian
2015-04-01
For decades, a certain type of ultra low frequency waves with a period of about 30 seconds have been observed in the Earth's quasi-parallel foreshock. These waves, with a wavelength of about an Earth radius, are compressive and propagate with an average angle of 20 degrees with respect of the interplanetary magnetic field (IMF). The latter property has caused trouble to scientists as the growth rate for the instability causing the waves is maximized along the magnetic field. So far, these waves have been characterized by single or multi-spacecraft methods and 2-dimensional hybrid-PIC simulations, which have not fully reproduced the wave properties. Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves the six-dimensional phase space utilising the Vlasov equation for protons, while electrons are a charge-neutralising fluid. The outcome of the simulation is a global reproduction of ion-scale physics in a holistic manner where the generation of physical features can be followed in time and their consequences can be quantitatively characterised. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global scale magnetospheric scale with a resolution of a couple of hundred kilometres in the ordinary space and 20 km/s in the velocity space. We run Vlasiator under a radial IMF in five dimensions consisting of the three-dimensional velocity space embedded in the ecliptic plane. We observe the generation of the 30-second ULF waves, and characterize their evolution and physical properties in time. We compare the results both to THEMIS observations and to the quasi-linear theory. We find that Vlasiator reproduces the foreshock ULF waves in all reported observational aspects, i.e., they are of the observed size in wavelength and period, they are compressive and propagate obliquely to the IMF. In particular, we discuss the issues related to the long-standing question of oblique propagation.
Minerva exoplanet detection sensitivity from simulated observations
NASA Astrophysics Data System (ADS)
McCrady, Nate; Nava, C.
2014-01-01
Small rocky planets induce radial velocity signals that are difficult to detect in the presence of stellar noise sources of comparable or larger amplitude. Minerva is a dedicated, robotic observatory that will attain 1 meter per second precision to detect these rocky planets in the habitable zone around nearby stars. We present results of an ongoing project investigating Minerva’s planet detection sensitivity as a function of observational cadence, planet mass, and orbital parameters (period, eccentricity, and argument of periastron). Radial velocity data is simulated with realistic observing cadence, accounting for weather patterns at Mt. Hopkins, Arizona. Instrumental and stellar noise are added to the simulated observations, including effects of oscillation, jitter, starspots and rotation. We extract orbital parameters from the simulated RV data using the RVLIN code. A Monte Carlo analysis is used to explore the parameter space and evaluate planet detection completeness. Our results will inform the Minerva observing strategy by providing a quantitative measure of planet detection sensitivity as a function of orbital parameters and cadence.
Simulability of observables in general probabilistic theories
NASA Astrophysics Data System (ADS)
Filippov, Sergey N.; Heinosaari, Teiko; Leppäjärvi, Leevi
2018-06-01
The existence of incompatibility is one of the most fundamental features of quantum theory and can be found at the core of many of the theory's distinguishing features, such as Bell inequality violations and the no-broadcasting theorem. A scheme for obtaining new observables from existing ones via classical operations, the so-called simulation of observables, has led to an extension of the notion of compatibility for measurements. We consider the simulation of observables within the operational framework of general probabilistic theories and introduce the concept of simulation irreducibility. While a simulation irreducible observable can only be simulated by itself, we show that any observable can be simulated by simulation irreducible observables, which in the quantum case correspond to extreme rank-1 positive-operator-valued measures. We also consider cases where the set of simulators is restricted in one of two ways: in terms of either the number of simulating observables or their number of outcomes. The former is seen to be closely connected to compatibility and k compatibility, whereas the latter leads to a partial characterization for dichotomic observables. In addition to the quantum case, we further demonstrate these concepts in state spaces described by regular polygons.
Observing System Simulation Experiments: An Overview
NASA Technical Reports Server (NTRS)
Prive, Nikki C.; Errico, Ronald M.
2016-01-01
An overview of Observing System Simulation Experiments (OSSEs) will be given, with focus on calibration and validation of OSSE frameworks. Pitfalls and practice will be discussed, including observation error characteristics, incestuousness, and experimental design. The potential use of OSSEs for investigation of the behaviour of data assimilation systems will be explored, including some results from experiments using the NASAGMAO OSSE.
MOCCA code for star cluster simulation: comparison with optical observations using COCOA
NASA Astrophysics Data System (ADS)
Askar, Abbas; Giersz, Mirek; Pych, Wojciech; Olech, Arkadiusz; Hypki, Arkadiusz
2016-02-01
We introduce and present preliminary results from COCOA (Cluster simulatiOn Comparison with ObservAtions) code for a star cluster after 12 Gyr of evolution simulated using the MOCCA code. The COCOA code is being developed to quickly compare results of numerical simulations of star clusters with observational data. We use COCOA to obtain parameters of the projected cluster model. For comparison, a FITS file of the projected cluster was provided to observers so that they could use their observational methods and techniques to obtain cluster parameters. The results show that the similarity of cluster parameters obtained through numerical simulations and observations depends significantly on the quality of observational data and photometric accuracy.
NASA Technical Reports Server (NTRS)
Berchem, J.; Raeder, J.; Ashour-Abdalla, M.; Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Yamamoto, T.; Lepping, R. P.
1998-01-01
This paper reports a comparison between Geotail observations of plasmas and magnetic fields at 200 R(sub E) in the Earth's magnetotail with results from a time-dependent, global magnetohydrodynamic simulation of the interaction of the solar wind with the magnetosphere. The study focuses on observations from July 7, 1993, during which the Geotail spacecraft crossed the distant tail magnetospheric boundary several times while the interplanetary magnetic field (IMF) was predominantly northward and was marked by slow rotations of its clock angle. Simultaneous IMP 8 observations of solar wind ions and the IMF were used as driving input for the MHD simulation, and the resulting time series were compared directly with those from the Geotail spacecraft. The very good agreement found provided the basis for an investigation of the response of the distant tail associated with the clock angle of the IMF. Results from the simulation show that the stresses imposed by the draping of magnetosheath field lines and the asymmetric removal of magnetic flux tailward of the cusps altered considerably the shape of the distant tail as the solar wind discontinuities convected downstream of Earth. As a result, the cross section of the distant tail was considerably flattened along the direction perpendicular to the IMF clock angle, the direction of the neutral sheet following that of the IMF. The simulation also revealed that the combined action of magnetic reconnection and the slow rotation of the IMF clock angle led to a braiding of the distant tail's magnetic field lines along the axis of the tail, with the plane of the braid lying in the direction of the IMF.
Observing system simulation experiments with multiple methods
NASA Astrophysics Data System (ADS)
Ishibashi, Toshiyuki
2014-11-01
An observing System Simulation Experiment (OSSE) is a method to evaluate impacts of hypothetical observing systems on analysis and forecast accuracy in numerical weather prediction (NWP) systems. Since OSSE requires simulations of hypothetical observations, uncertainty of OSSE results is generally larger than that of observing system experiments (OSEs). To reduce such uncertainty, OSSEs for existing observing systems are often carried out as calibration of the OSSE system. The purpose of this study is to achieve reliable OSSE results based on results of OSSEs with multiple methods. There are three types of OSSE methods. The first one is the sensitivity observing system experiment (SOSE) based OSSE (SOSEOSSE). The second one is the ensemble of data assimilation cycles (ENDA) based OSSE (ENDA-OSSE). The third one is the nature-run (NR) based OSSE (NR-OSSE). These three OSSE methods have very different properties. The NROSSE evaluates hypothetical observations in a virtual (hypothetical) world, NR. The ENDA-OSSE is very simple method but has a sampling error problem due to a small size ensemble. The SOSE-OSSE requires a very highly accurate analysis field as a pseudo truth of the real atmosphere. We construct these three types of OSSE methods in the Japan meteorological Agency (JMA) global 4D-Var experimental system. In the conference, we will present initial results of these OSSE systems and their comparisons.
Simulated GOLD Observations of Atmospheric Waves
NASA Astrophysics Data System (ADS)
Correira, J.; Evans, J. S.; Lumpe, J. D.; Rusch, D. W.; Chandran, A.; Eastes, R.; Codrescu, M.
2016-12-01
The Global-scale Observations of the Limb and Disk (GOLD) mission will measure structures in the Earth's airglow layer due to dynamical forcing by vertically and horizontally propagating waves. These measurements focus on global-scale structures, including compositional and temperature responses resulting from dynamical forcing. Daytime observations of far-UV emissions by GOLD will be used to generate two-dimensional maps of the ratio of atomic oxygen and molecular nitrogen column densities (ΣO/N2 ) as well as neutral temperature that provide signatures of large-scale spatial structure. In this presentation, we use simulations to demonstrate GOLD's capability to deduce periodicities and spatial dimensions of large-scale waves from the spatial and temporal evolution observed in composition and temperature maps. Our simulations include sophisticated forward modeling of the upper atmospheric airglow that properly accounts for anisotropy in neutral and ion composition, temperature, and solar illumination. Neutral densities and temperatures used in the simulations are obtained from global circulation and climatology models that have been perturbed by propagating waves with a range of amplitudes, periods, and sources of excitation. Modeling of airglow emission and predictions of ΣO/N2 and neutral temperatures are performed with the Atmospheric Ultraviolet Radiance Integrated Code (AURIC) and associated derived product algorithms. Predicted structure in ΣO/N2 and neutral temperature due to dynamical forcing by propagating waves is compared to existing observations. Realistic GOLD Level 2 data products are generated from simulated airglow emission using algorithm code that will be implemented operationally at the GOLD Science Data Center.
Titan's organic chemistry: Results of simulation experiments
NASA Technical Reports Server (NTRS)
Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.
1992-01-01
Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.
International benchmarking of longitudinal train dynamics simulators: results
NASA Astrophysics Data System (ADS)
Wu, Qing; Spiryagin, Maksym; Cole, Colin; Chang, Chongyi; Guo, Gang; Sakalo, Alexey; Wei, Wei; Zhao, Xubao; Burgelman, Nico; Wiersma, Pier; Chollet, Hugues; Sebes, Michel; Shamdani, Amir; Melzi, Stefano; Cheli, Federico; di Gialleonardo, Egidio; Bosso, Nicola; Zampieri, Nicolò; Luo, Shihui; Wu, Honghua; Kaza, Guy-Léon
2018-03-01
This paper presents the results of the International Benchmarking of Longitudinal Train Dynamics Simulators which involved participation of nine simulators (TABLDSS, UM, CRE-LTS, TDEAS, PoliTo, TsDyn, CARS, BODYSIM and VOCO) from six countries. Longitudinal train dynamics results and computing time of four simulation cases are presented and compared. The results show that all simulators had basic agreement in simulations of locomotive forces, resistance forces and track gradients. The major differences among different simulators lie in the draft gear models. TABLDSS, UM, CRE-LTS, TDEAS, TsDyn and CARS had general agreement in terms of the in-train forces; minor differences exist as reflections of draft gear model variations. In-train force oscillations were observed in VOCO due to the introduction of wheel-rail contact. In-train force instabilities were sometimes observed in PoliTo and BODYSIM due to the velocity controlled transitional characteristics which could have generated unreasonable transitional stiffness. Regarding computing time per train operational second, the following list is in order of increasing computing speed: VOCO, TsDyn, PoliTO, CARS, BODYSIM, UM, TDEAS, CRE-LTS and TABLDSS (fastest); all simulators except VOCO, TsDyn and PoliTo achieved faster speeds than real-time simulations. Similarly, regarding computing time per integration step, the computing speeds in order are: CRE-LTS, VOCO, CARS, TsDyn, UM, TABLDSS and TDEAS (fastest).
NASA Technical Reports Server (NTRS)
Aveiro, H. C.; Hysell, D. L.; Caton, R. G.; Groves, K. M.; Klenzing, J.; Pfaff, R. F.; Stoneback, R.; Heelis, R. A.
2012-01-01
A three-dimensional numerical simulation of plasma density irregularities in the postsunset equatorial F region ionosphere leading to equatorial spread F (ESF) is described. The simulation evolves under realistic background conditions including bottomside plasma shear flow and vertical current. It also incorporates C/NOFS satellite data which partially specify the forcing. A combination of generalized Rayleigh-Taylor instability (GRT) and collisional shear instability (CSI) produces growing waveforms with key features that agree with C/NOFS satellite and ALTAIR radar observations in the Pacific sector, including features such as gross morphology and rates of development. The transient response of CSI is consistent with the observation of bottomside waves with wavelengths close to 30 km, whereas the steady state behavior of the combined instability can account for the 100+ km wavelength waves that predominate in the F region.
Early BHs: simulations and observations
NASA Astrophysics Data System (ADS)
Cappelluti, Nico; di-Matteo, Tiziana; Schawinski, Kevin; Fragos, Tassos
We report recent investigations in the field of Early Black Holes. We summarize recent theoretical and observational efforts to understand how Black Holes formed and eventually evolved into Super Massive Black Holes at high-z. This paper makes use of state of the art computer simulations and multiwavelength surveys. Although non conclusive, we present results and hypothesis that pose exciting challenges to modern astrophysics and to future facilities.
Galaxy simulations: Kinematics and mock observations
NASA Astrophysics Data System (ADS)
Moody, Christopher E.
2013-08-01
spiral galaxies. We recreate minor and major binary mergers, binary merger trees with multiple progenitors, and multiple sequential mergers. Within each of these categories of formation history, we correlate progenitor gas fraction, mass ratio, orbital pericenter, orbital ellipticity, spin, and kinematically decoupled cores with remnant kinematic properties. We find that binary mergers nearly always form fast rotators, but slow rotators can be formed from zero initial angular momentum configurations and gas-poor mergers. Remnants of binary merger trees are triaxial slow rotators. Sequential mergers form round slow rotators that most resemble the ATLAS3D rotators. We investigate the failure of ART and Sunrise simulation to reproduce the observed distribution of galaxies in the UVJ color-color diagram. No simulated galaxies achieve a color with V-J >1.0 while still being in the blue sequence. I systematically study the underlying sub grid models present in Sunrise to diagnose the source of the discrepancy. The experiments were largely unsuccessful in directly isolating the root of the J-band excess attenuation; however, they are instructive and can guide the intuition in terms of understanding the interplay of stellar emission and dust. These experiments were aimed at understanding the role of the underlying sub grid dust and radiation models, varying the dust geometry, and performing numerical studies of the radiation transfer calculation. Finally, I detail the data pipeline responsible for the creation of galaxy mock observations. The pipeline can be broken into the ART simulation raw data, the dark matter merger tree backbone, the format translation using yt, simulation the radiation transfer in Sunrise, and post-processed image treatments resulting. At every step, I detail the execution of the algorithms, the format of the data, and useful scripts for straightforward analysis.
Observers' focus of attention in the simulation of self-perception.
Wegner, D M; Finstuen, K
1977-01-01
This research was designed to assess the effects of a manipulation of observers' focus of attention--from a focus on the actor to a focus on the actor's situation--upon observers' attributions of attitude to an actor in a simulation of a forced-compliance cognitive dissonance experiment. Observers induced through empathy instructions to focus attention on the actor's situation inferred less actor attitude positivity than did observers given no specific observational set. In addition, situation-focused observers inferred that the actor's attitude was directly related to reward magnitude, whereas actor-focused observers inferred that the actor's attitude was inversely related to reward magnitude. An extension of self-perception theory, offered as an interpretation of these and other results, suggested that motivation attribution made by actors and observers in dissonance and simulation studies are dependent on focus of attention. The attributions made by actor-focused observers simulate those of objectively self-aware actors and are based upon perceived intrinsic motivation; the attributions of situation-focused observers simulate those of subjectively self-aware actors and are based upon perceived extrinsic motivation.
Comparison of Observed Spatio-temporal Aftershock Patterns with Earthquake Simulator Results
NASA Astrophysics Data System (ADS)
Kroll, K.; Richards-Dinger, K. B.; Dieterich, J. H.
2013-12-01
Due to the complex nature of faulting in southern California, knowledge of rupture behavior near fault step-overs is of critical importance to properly quantify and mitigate seismic hazards. Estimates of earthquake probability are complicated by the uncertainty that a rupture will stop at or jump a fault step-over, which affects both the magnitude and frequency of occurrence of earthquakes. In recent years, earthquake simulators and dynamic rupture models have begun to address the effects of complex fault geometries on earthquake ground motions and rupture propagation. Early models incorporated vertical faults with highly simplified geometries. Many current studies examine the effects of varied fault geometry, fault step-overs, and fault bends on rupture patterns; however, these works are limited by the small numbers of integrated fault segments and simplified orientations. The previous work of Kroll et al., 2013 on the northern extent of the 2010 El Mayor-Cucapah rupture in the Yuha Desert region uses precise aftershock relocations to show an area of complex conjugate faulting within the step-over region between the Elsinore and Laguna Salada faults. Here, we employ an innovative approach of incorporating this fine-scale fault structure defined through seismological, geologic and geodetic means in the physics-based earthquake simulator, RSQSim, to explore the effects of fine-scale structures on stress transfer and rupture propagation and examine the mechanisms that control aftershock activity and local triggering of other large events. We run simulations with primary fault structures in state of California and northern Baja California and incorporate complex secondary faults in the Yuha Desert region. These models produce aftershock activity that enables comparison between the observed and predicted distribution and allow for examination of the mechanisms that control them. We investigate how the spatial and temporal distribution of aftershocks are affected by
Cluster observations and simulations of He+ EMIC triggered emissions
NASA Astrophysics Data System (ADS)
Grison, B.; Shoji, M.; Santolik, O.; Omura, Y.
2012-12-01
EMIC triggered emissions have been reported in the inner magnetosphere at the edge of the plasmapause nightside [Pickett et al., 2010]. The generation mechanism proposed by Omura et al. [2010] is very similar to the one of the whistler chorus emissions and simulation results agree with observations and theory [Shoji et Omura, 2011]. The main characteristics of these emissions generated in the magnetic equatorial plane region are a frequency with time dispersion and a high level of coherence. The start frequency of previously mentioned observations is above half of the proton gyrofrequency. It means that the emissions are generated on the proton branch. On the He+ branch, generation of triggered emissions, in the same region, requests more energetic protons and the triggering process starts below the He+ gyrofrequency. It makes their identification in Cluster data rather difficult. Recent simulation results confirm the possibility of EMIC triggered emission on the He+ branch. In the present contribution we propose to compare a Cluster event to simulation results in order to investigate the possibility to identify observations to a He+ triggered emission. The impact of the observed waves on particle precipitation is also investigated.
A NEO population generation and observation simulation software tool
NASA Astrophysics Data System (ADS)
Müller, Sven; Gelhaus, Johannes; Hahn, Gerhard; Franco, Raffaella
One of the main targets of ESA's Space Situational Awareness (SSA) program is to build a wide knowledge base about objects that can potentially harm Earth (Near-Earth Objects, NEOs). An important part of this effort is to create the Small Bodies Data Centre (SBDC) which is going to aggregate measurement data from a fully-integrated NEO observation sensor network. Until this network is developed, artificial NEO measurement data is needed in order to validate SBDC algorithms. Moreover, to establish a functioning NEO observation sensor network, it has to be determined where to place sensors, what technical requirements have to be met in order to be able to detect NEOs and which observation strategies work the best. Because of this, a sensor simulation software was needed. This paper presents a software tool which allows users to create and analyse NEO populations and to simulate and analyse population observations. It is a console program written in Fortran and comes with a Graphical User Interface (GUI) written in Java and C. The tool can be distinguished into the components ``Population Generator'' and ``Observation Simulator''. The Population Generator component is responsible for generating and analysing a NEO population. Users can choose between creating fictitious (random) and synthetic populations. The latter are based on one of two models describing the orbital and size distribution of observed NEOs: The existing socalled ``Bottke Model'' (Bottke et al. 2000, 2002) and the new ``Granvik Model'' (Granvik et al. 2014, in preparation) which has been developed in parallel to the tool. Generated populations can be analysed by defining 2D, 3D and scatter plots using various NEO attributes. As a result, the tool creates the appropiate files for the plotting tool ``gnuplot''. The tool's Observation Simulator component yields the Observation Simulation and Observation Analysis functions. Users can define sensor systems using ground- or space-based locations as well as
Observing System Simulation Experiments
NASA Technical Reports Server (NTRS)
Prive, Nikki
2015-01-01
This presentation gives an overview of Observing System Simulation Experiments (OSSEs). The components of an OSSE are described, along with discussion of the process for validating, calibrating, and performing experiments. a.
NASA Astrophysics Data System (ADS)
Fuqua, Peter D.; Presser, Nathan; Barrie, James D.; Meshishnek, Michael J.; Coleman, Dianne J.
2002-06-01
Certain spaceborne telescope designs require that dielectric-coated lenses be exposed to the energetic electrons and protons associated with the space environment. Test coupons that were exposed to a simulated space environment showed extensive pitting as a result of dielectric breakdown. A typical pit was 50-100 mum at the surface and extended to the substrate material, in which a 10-mum-diameter melt region was found. Pitting was not observed on similar samples that had also been overcoated with a transparent conductive thin film. Measurement of the bidirectional reflectance distribution transfer function showed that pitting caused a fivefold to tenfold increase in the scattering of visible light.
Ionospheric Trend Over Wuhan During 1947-2017: Comparison Between Simulation and Observation
NASA Astrophysics Data System (ADS)
Yue, Xinan; Hu, Lianhuan; Wei, Yong; Wan, Weixing; Ning, Baiqi
2018-02-01
Since Roble and Dickinson (1989), who drew the community's attention about the greenhouse gas effect on the ionosphere, huge efforts have been implemented on ionospheric climate study. However, direct comparison between observations and simulations is still rare. Recently, the Wuhan ionosonde observations were digitized and standardized through unified method back to 1947. In this study, the NCAR-TIEGCM was driven by Mauna Loa Observatory observed CO2 level and International Geomagnetic Reference Field (IGRF) geomagnetic field to simulate their effects on ionospheric long-term trend over Wuhan. Only March equinox was considered in both data analysis and simulation. Simulation results show that the CO2 and geomagnetic field have comparable effect on hmF2 trend, while geomagnetic field effect is stronger than CO2 on foF2 trend over Wuhan. Both factors result in obvious but different diurnal variations of foF2/hmF2 long-term trends. The geomagnetic field effect is nonlinear versus years since the long-term variation of geomagnetic field intensity and orientation is complex. Mean value of foF2 and hmF2 trend is (-0.0021 MHz/yr, -0.106 km/yr) and (-0.0022 MHz/yr, -0.0763 km/yr) for observation and simulation, respectively. Regarding the diurnal variation of the trend, the simulation accords well with that of observation except hmF2 results around 12 UT. Overall, good agreement between observation and simulation illustrates the good quality of Wuhan ionosonde long-term data and the validity of ancient ionosphere reconstruction based on realistic indices driving simulation.
Cassini radar : system concept and simulation results
NASA Astrophysics Data System (ADS)
Melacci, P. T.; Orosei, R.; Picardi, G.; Seu, R.
1998-10-01
The Cassini mission is an international venture, involving NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI), for the investigation of the Saturn system and, in particular, Titan. The Cassini radar will be able to see through Titan's thick, optically opaque atmosphere, allowing us to better understand the composition and the morphology of its surface, but the interpretation of the results, due to the complex interplay of many different factors determining the radar echo, will not be possible without an extensive modellization of the radar system functioning and of the surface reflectivity. In this paper, a simulator of the multimode Cassini radar will be described, after a brief review of our current knowledge of Titan and a discussion of the contribution of the Cassini radar in answering to currently open questions. Finally, the results of the simulator will be discussed. The simulator has been implemented on a RISC 6000 computer by considering only the active modes of operation, that is altimeter and synthetic aperture radar. In the instrument simulation, strict reference has been made to the present planned sequence of observations and to the radar settings, including burst and single pulse duration, pulse bandwidth, pulse repetition frequency and all other parameters which may be changed, and possibly optimized, according to the operative mode. The observed surfaces are simulated by a facet model, allowing the generation of surfaces with Gaussian or non-Gaussian roughness statistic, together with the possibility of assigning to the surface an average behaviour which can represent, for instance, a flat surface or a crater. The results of the simulation will be discussed, in order to check the analytical evaluations of the models of the average received echoes and of the attainable performances. In conclusion, the simulation results should allow the validation of the theoretical evaluations of the capabilities of microwave instruments, when
Ocean Carbon States: Data Mining in Observations and Numerical Simulations Results
NASA Astrophysics Data System (ADS)
Latto, R.; Romanou, A.
2017-12-01
Advanced data mining techniques are rapidly becoming widely used in Climate and Earth Sciences with the purpose of extracting new meaningful information from increasingly larger and more complex datasets. This is particularly important in studies of the global carbon cycle, where any lack of understanding of its combined physical and biogeochemical drivers is detrimental to our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major carbon reservoirs. The analysis presented here evaluates the use of cluster analysis as a means of identifying and comparing spatial and temporal patterns extracted from observational and model datasets. As the observational data is organized into various regimes, which we will call "ocean carbon states", we gain insight into the physical and/or biogeochemical processes controlling the ocean carbon cycle as well as how well these processes are simulated by a state-of-the-art climate model. We find that cluster analysis effectively produces realistic, dynamic regimes that can be associated with specific processes at different temporal scales for both observations and the model. In addition, we show how these regimes can be used to illustrate and characterize the model biases in the model air-sea flux of CO2. These biases are attributed to biases in salinity, sea surface temperature, wind speed, and nitrate, which are then used to identify the physical processes that are inaccurately reproduced by the model. In this presentation, we provide a proof-of-concept application using simple datasets, and we expand to more complex ones, using several physical and biogeochemical variable pairs, thus providing considerable insight into the mechanisms and phases of the ocean carbon cycle over different temporal and spatial scales.
Atmospheric icing of structures: Observations and simulations
NASA Astrophysics Data System (ADS)
Ágústsson, H.; Elíasson, Á. J.; Thorsteins, E.; Rögnvaldsson, Ó.; Ólafsson, H.
2012-04-01
This study compares observed icing in a test span in complex orography at Hallormsstaðaháls (575 m) in East-Iceland with parameterized icing based on an icing model and dynamically downscaled weather at high horizontal resolution. Four icing events have been selected from an extensive dataset of observed atmospheric icing in Iceland. A total of 86 test-spans have been erected since 1972 at 56 locations in complex terrain with more than 1000 icing events documented. The events used here have peak observed ice load between 4 and 36 kg/m. Most of the ice accretion is in-cloud icing but it may partly be mixed with freezing drizzle and wet snow icing. The calculation of atmospheric icing is made in two steps. First the atmospheric data is created by dynamically downscaling the ECMWF-analysis to high resolution using the non-hydrostatic mesoscale Advanced Research WRF-model. The horizontal resolution of 9, 3, 1 and 0.33 km is necessary to allow the atmospheric model to reproduce correctly local weather in the complex terrain of Iceland. Secondly, the Makkonen-model is used to calculate the ice accretion rate on the conductors based on the simulated temperature, wind, cloud and precipitation variables from the atmospheric data. In general, the atmospheric model correctly simulates the atmospheric variables and icing calculations based on the atmospheric variables correctly identify the observed icing events, but underestimate the load due to too slow ice accretion. This is most obvious when the temperature is slightly below 0°C and the observed icing is most intense. The model results improve significantly when additional observations of weather from an upstream weather station are used to nudge the atmospheric model. However, the large variability in the simulated atmospheric variables results in high temporal and spatial variability in the calculated ice accretion. Furthermore, there is high sensitivity of the icing model to the droplet size and the possibility that
Levett-Jones, Tracy; Andersen, Patrea; Reid-Searl, Kerry; Guinea, Stephen; McAllister, Margaret; Lapkin, Samuel; Palmer, Lorinda; Niddrie, Marian
2015-09-01
Active participation in immersive simulation experiences can result in technical and non-technical skill enhancement. However, when simulations are conducted in large groups, maintaining the interest of observers so that they do not disengage from the learning experience can be challenging. We implemented Tag Team Simulation with the aim of ensuring that both participants and observers had active and integral roles in the simulation. In this paper we outline the features of this innovative approach and provide an example of its application to a pain simulation. Evaluation was conducted using the Satisfaction with Simulation Experience Scale. A total of 444 year nursing students participated from a population of 536 (response rate 83%). Cronbach's alpha for the Scale was .94 indicating high internal consistency. The mean satisfaction score for participants was 4.63 compared to 4.56 for observers. An independent sample t test revealed no significant difference between these scores (t (300) = -1.414, p = 0.16). Tag team simulation is an effective approach for ensuring observers' and participants' active involvement during group-based simulations and one that is highly regarded by students. It has the potential for broad applicability across a range of leaning domains both within and beyond nursing. Copyright © 2015 Elsevier Ltd. All rights reserved.
LES ARM Symbiotic Simulation and Observation (LASSO) Implementation Strategy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gustafson Jr., WI; Vogelmann, AM
2015-09-01
This document illustrates the design of the Large-Eddy Simulation (LES) ARM Symbiotic Simulation and Observation (LASSO) workflow to provide a routine, high-resolution modeling capability to augment the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s high-density observations. LASSO will create a powerful new capability for furthering ARM’s mission to advance understanding of cloud, radiation, aerosol, and land-surface processes. The combined observational and modeling elements will enable a new level of scientific inquiry by connecting processes and context to observations and providing needed statistics for details that cannot be measured. The result will be improved process understandingmore » that facilitates concomitant improvements in climate model parameterizations. The initial LASSO implementation will be for ARM’s Southern Great Plains site in Oklahoma and will focus on shallow convection, which is poorly simulated by climate models due in part to clouds’ typically small spatial scale compared to model grid spacing, and because the convection involves complicated interactions of microphysical and boundary layer processes.« less
NASA Astrophysics Data System (ADS)
Guidi, Giovanni; Scannapieco, Cecilia; Walcher, C. Jakob
2015-12-01
We study the sources of biases and systematics in the derivation of galaxy properties from observational studies, focusing on stellar masses, star formation rates, gas and stellar metallicities, stellar ages, magnitudes and colours. We use hydrodynamical cosmological simulations of galaxy formation, for which the real quantities are known, and apply observational techniques to derive the observables. We also analyse biases that are relevant for a proper comparison between simulations and observations. For our study, we post-process the simulation outputs to calculate the galaxies' spectral energy distributions (SEDs) using stellar population synthesis models and also generate the fully consistent far-UV-submillimetre wavelength SEDs with the radiative transfer code SUNRISE. We compared the direct results of simulations with the observationally derived quantities obtained in various ways, and found that systematic differences in all studied galaxy properties appear, which are caused by: (1) purely observational biases, (2) the use of mass-weighted and luminosity-weighted quantities, with preferential sampling of more massive and luminous regions, (3) the different ways of constructing the template of models when a fit to the spectra is performed, and (4) variations due to different calibrations, most notably for gas metallicities and star formation rates. Our results show that large differences can appear depending on the technique used to derive galaxy properties. Understanding these differences is of primary importance both for simulators, to allow a better judgement of similarities and differences with observations, and for observers, to allow a proper interpretation of the data.
Results from Binary Black Hole Simulations in Astrophysics Applications
NASA Technical Reports Server (NTRS)
Baker, John G.
2007-01-01
Present and planned gravitational wave observatories are opening a new astronomical window to the sky. A key source of gravitational waves is the merger of two black holes. The Laser Interferometer Space Antenna (LISA), in particular, is expected to observe these events with signal-to-noise ratio's in the thousands. To fully reap the scientific benefits of these observations requires a detailed understanding, based on numerical simulations, of the predictions of General Relativity for the waveform signals. New techniques for simulating binary black hole mergers, introduced two years ago, have led to dramatic advances in applied numerical simulation work. Over the last two years, numerical relativity researchers have made tremendous strides in understanding the late stages of binary black hole mergers. Simulations have been applied to test much of the basic physics of binary black hole interactions, showing robust results for merger waveform predictions, and illuminating such phenomena as spin-precession. Calculations have shown that merging systems can be kicked at up to 2500 km/s by the thrust from asymmetric emission. Recently, long lasting simulations of ten or more orbits allow tests of post-Newtonian (PN) approximation results for radiation from the last orbits of the binary's inspiral. Already, analytic waveform models based PN techniques with incorporated information from numerical simulations may be adequate for observations with current ground based observatories. As new advances in simulations continue to rapidly improve our theoretical understanding of the systems, it seems certain that high-precision predictions will be available in time for LISA and other advanced ground-based instruments. Future gravitational wave observatories are expected to make precision.
Experimental and simulational result multipactors in 112 MHz QWR injector
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xin, T.; Ben-Zvi, I.; Belomestnykh, S.
2015-05-03
The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were installed and tested for the first time. During this experiment, we observed several multipacting barriers at different gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.8 MV gun voltage under pulsedmore » mode after several round of conditioning processes.« less
Simulations of star-forming molecular clouds: observational predictions
NASA Astrophysics Data System (ADS)
Zhang, Shangjia; Hartmann, Lee; Kuznetsova, Aleksandra; Abelardo Zamora, Manuel
2018-01-01
Observations of protostellar molecular cloud cores can be used to test theories of star formation. However, observational results can be biased because of limited information: (a) only two spatial dimensions and one velocity dimension can be measured, (b) and cores generally are not spherically symmetric. We use numerical simulations of the formation and collapse of molecular gas with sink particles to make observational predictions. We use the radiative transfer code LIME to predict CO and NH3 channel maps. We find reasonable agreement with observed velocity structures and gradients but occasional large differences depending on viewing angle.
Observing System Simulation Experiments for Fun and Profit
NASA Technical Reports Server (NTRS)
Prive, Nikki C.
2015-01-01
Observing System Simulation Experiments can be powerful tools for evaluating and exploring both the behavior of data assimilation systems and the potential impacts of future observing systems. With great power comes great responsibility - given a pure modeling framework, how can we be sure our results are meaningful? The challenges and pitfalls of OSSE calibration and validation will be addressed, as well as issues of incestuousness, selection of appropriate metrics, and experiment design. The use of idealized observational networks to investigate theoretical ideas in a fully complex modeling framework will also be discussed
Laboratory observations and simulations of phase reddening
NASA Astrophysics Data System (ADS)
Schröder, S. E.; Grynko, Ye.; Pommerol, A.; Keller, H. U.; Thomas, N.; Roush, T. L.
2014-09-01
The visible reflectance spectrum of many Solar System bodies changes with changing viewing geometry for reasons not fully understood. It is often observed to redden (increasing spectral slope) with increasing solar phase angle, an effect known as phase reddening. Only once, in an observation of the martian surface by the Viking 1 lander, was reddening observed up to a certain phase angle with bluing beyond, making the reflectance ratio as a function of phase angle shaped like an arch. However, in laboratory experiments this arch-shape is frequently encountered. To investigate this, we measured the bidirectional reflectance of particulate samples of several common rock types in the 400-1000 nm wavelength range and performed ray-tracing simulations. We confirm the occurrence of the arch for surfaces that are forward scattering, i.e. are composed of semi-transparent particles and are smooth on the scale of the particles, and for which the reflectance increases from the lower to the higher wavelength in the reflectance ratio. The arch shape is reproduced by the simulations, which assume a smooth surface. However, surface roughness on the scale of the particles, such as the Hapke and van Horn (Hapke, B., van Horn, H. [1963]. J. Geophys. Res. 68, 4545-4570) fairy castles that can spontaneously form when sprinkling a fine powder, leads to monotonic reddening. A further consequence of this form of microscopic roughness (being indistinct without the use of a microscope) is a flattening of the disk function at visible wavelengths, i.e. Lommel-Seeliger-type scattering. The experiments further reveal monotonic reddening for reflectance ratios at near-IR wavelengths. The simulations fail to reproduce this particular reddening, and we suspect that it results from roughness on the surface of the particles. Given that the regolith of atmosphereless Solar System bodies is composed of small particles, our results indicate that the prevalence of monotonic reddening and Lommel
Observation and Simulation of Microseisms Offshore Ireland
NASA Astrophysics Data System (ADS)
Le Pape, Florian; Bean, Chris; Craig, David; Jousset, Philippe; Donne, Sarah; Möllhoff, Martin
2017-04-01
Although more and more used in seismic imagery, ocean induced ambient seismic noise is still not so well understood, particularly how the signal propagates from ocean to land. Between January and September 2016, 10 broadband Ocean Bottom Seismometers (OBSs) stations, including acoustic sensors (hydrophone), were deployed across the shelf offshore Donegal and out into the Rockall Trough. The preliminary results show spatial and temporal variability in the ocean generated seismic noise which holds information about changes in the generation source process, including meteorological information, but also in the geological structure. In addition to the collected OBS data, numerical simulations of acoustic/seismic wave propagation are also considered in order to study the spatio-temporal variation of the broadband acoustic wavefield and its connection with the measured seismic wavefield in the region. Combination of observations and simulations appears significant to better understand what control the acoustic/seismic coupling at the sea floor as well as the effect of the water column and sediments thickness on signal propagation. Ocean generated seismic ambient noise recorded at the seafloor appears to behave differently in deep and shallow water and 3D simulations of acoustic/seismic wave propagation look particularly promising for reconciling deep ocean, shelf and land seismic observations.
A Statistical Comparison of PSC Model Simulations and POAM Observations
NASA Technical Reports Server (NTRS)
Strawa, A. W.; Drdla, K.; Fromm, M.; Bokarius, K.; Gore, Warren J. (Technical Monitor)
2002-01-01
A better knowledge of PSC composition and formation mechanisms is important to better understand and predict stratospheric ozone depletion. Several past studies have attempted to compare modeling results with satellite observations. These comparisons have concentrated on case studies. In this paper we adopt a statistical approach. POAM PSC observations from several Arctic winters are categorized into Type Ia and Ib PSCs using a technique based on Strawa et al. The discrimination technique has been modified to employ the wavelengths dependence of the extinction signal at all wavelengths rather than only at 603 and 10 18 nm. Winter-long simulations for the 1999-2000 Arctic winter have been made using the IMPACT model. These simulations have been constrained by aircraft observations made during the SOLVE/THESEO 2000 campaign. A complete set of winter-long simulations was run for several different microphysical and PSC formation scenarios. The simulations give us perfect knowledge of PSC type (Ia, Ib, or II), composition, especially condensed phase HNO3 which is important for denitrification, and condensed phase H2O. Comparisons are made between the simulation and observation of PSC extinction at 1018 rim versus wavelength dependence, winter-long percentages of Ia and Ib occurrence, and temporal and altitude trends of the PSCs. These comparisons allow us to comment on how realistic some modeling scenarios are.
Hemispheric Coupling: Comparing Dynamo Simulations and Observations
NASA Astrophysics Data System (ADS)
Norton, A. A.; Charbonneau, P.; Passos, D.
2014-12-01
Numerical simulations that reproduce solar-like magnetic cycles can be used to generate long-term statistics. The variations in north-south hemispheric solar cycle synchronicity and amplitude produced in simulations has not been widely compared to observations. The observed limits on solar cycle amplitude and phase asymmetry show that hemispheric sunspot area production is no more than 20 % asymmetric for cycles 17-23 and that phase lags do not exceed 20 % (or two years) of the total cycle period, as determined from Royal Greenwich Observatory sunspot data. Several independent studies have found a long-term trend in phase values as one hemisphere leads the other for, on average, four cycles. Such persistence in phase is not indicative of a stochastic phenomenon. We compare these observational findings to the magnetic cycle found in a numerical simulation of solar convection recently produced with the EULAG-MHD model. This long "millennium simulation" spans more than 1600 years and generated 40 regular, sunspot-like cycles. While the simulated cycle length is too long (˜40 yrs) and the toroidal bands remain at too high of latitudes (>30°), some solar-like aspects of hemispheric asymmetry are reproduced. The model is successful at reproducing the synchrony of polarity inversions and onset of cycle as the simulated phase lags do not exceed 20 % of the cycle period. The simulated amplitude variations between the north and south hemispheres are larger than those observed in the Sun, some up to 40 %. An interesting note is that the simulations also show that one hemisphere can persistently lead the other for several successive cycles, placing an upper bound on the efficiency of transequatorial magnetic coupling mechanisms. These include magnetic diffusion, cross-equatorial mixing within latitudinally-elongated convective rolls (a.k.a. "banana cells") and transequatorial meridional flow cells. One or more of these processes may lead to magnetic flux cancellation whereby
Observing the baryon cycle in hydrodynamic cosmological simulations
NASA Astrophysics Data System (ADS)
Vander Vliet, Jacob Richard
An understanding of galaxy evolution requires an understanding of the flow of baryons in and out of a galaxy. The accretion of baryons is required for galaxies to form stars, while stars eject baryons out of the galaxy through stellar feedback mechanisms such as supernovae, stellar winds, and radiation pressure. The interplay between outfiowing and infalling material form the circumgalactic medium (CGM). Hydrodynamic simulations provide understanding of the connection between stellar feedback and the distribution and kinematics of baryons in the CGM. To compare simulations and observations properly the simulated CGI must be observed in the same manner as the real CGM. I have developed the Mockspec code to generate synthetic quasar absorption line observations of the CGM in cosmological hydrodynamic simulations. Mockspec generates synthetic spectra based on the phase; lnetallicity, and kinematics of CGM gas and mimics instrumental effects. Mockspec includes automated analysis of the spectra and identifies the gas responsible for the absorption. Mockspec was applied to simulations of dwarf galaxies at low redshift to examine the observable effect different feedback models have on the CGM. While the different feedback models had strong effects on the galaxy, they all produced a similar CGM that failed match observations. Mockspec was applied to the VELA simulation suite of high redshift, high mass galaxies to examine the variance of the CGM across different galaxies in different environments. The observed CGM showed little variation between the different galaxies and almost no evolution from z=4 to z=1. The VELAs were not able to generate a CGM to match the observations. The properties of cells responsible for the absorption were compared to the derived properties from Voigt Profile decomposition. VP modeling was found to accurately describe the HI and MgII absorbing gas but failed for high ionization species such as CIV and OVI, which do not arise in the coherent
NASA Astrophysics Data System (ADS)
Stanford, McKenna W.
The High Altitude Ice Crystals - High Ice Water Content (HAIC-HIWC) field campaign produced aircraft retrievals of total condensed water content (TWC), hydrometeor particle size distributions, and vertical velocity (w) in high ice water content regions of tropical mesoscale convective systems (MCSs). These observations are used to evaluate deep convective updraft properties in high-resolution nested Weather Research and Forecasting (WRF) simulations of observed MCSs. Because simulated hydrometeor properties are highly sensitive to the parameterization of microphysics, three commonly used microphysical parameterizations are tested, including two bulk schemes (Thompson and Morrison) and one bin scheme (Fast Spectral Bin Microphysics). A commonly documented bias in cloud-resolving simulations is the exaggeration of simulated radar reflectivities aloft in tropical MCSs. This may result from overly strong convective updrafts that loft excessive condensate mass and from simplified approximations of hydrometeor size distributions, properties, species separation, and microphysical processes. The degree to which the reflectivity bias is a separate function of convective dynamics, condensate mass, and hydrometeor size has yet to be addressed. This research untangles these components by comparing simulated and observed relationships between w, TWC, and hydrometer size as a function of temperature. All microphysics schemes produce median mass diameters that are generally larger than observed for temperatures between -10 °C and -40 °C and TWC > 1 g m-3. Observations produce a prominent mode in the composite mass size distribution around 300 microm, but under most conditions, all schemes shift the distribution mode to larger sizes. Despite a much greater number of samples, all simulations fail to reproduce observed high TWC or high w conditions between -20 °C and -40 °C in which only a small fraction of condensate mass is found in relatively large particle sizes. Increasing
Magneto-acoustic wave energy in sunspots: observations and numerical simulations
NASA Astrophysics Data System (ADS)
Felipe, T.; Khomenko, E.; Collados, M.; Beck, C.
2011-11-01
We have reproduced some sunspot wave signatures obtained from spectropolarimetric observations through 3D MHD numericalsimulations. The results of the simulations arecompared with the oscillations observed simultaneously at different heights from the SiI lambda10827Å line, HeI lambda10830Å line, the CaII H core and the FeI blends at the wings of the CaII H line. The simulations show a remarkable agreement with the observations, and we have used them to quantify the energy contribution of the magneto-acoustic waves to the chromospheric heating in sunspots. Our findings indicate that the energy supplied by these waves is 5-10 times lower than the amount needed to balance the chromospheric radiative losses.
Observations and Simulations of Electron Dynamics Near an Active Neutral Line
NASA Technical Reports Server (NTRS)
Goldstein, M. L.; Hwang, Kyoung-Joo; Ashour-Abdalla, Maha; El-Aloui, Mostafa; Schriver, David; Richard, Robert; Zhou, Meng; Walker, Ray
2010-01-01
Recent observations in the Earth's magnetotail have shown rapid increases in the fluxes of energetic electrons with energies up to 100's of keV associated with dipolarization fronts that propagate into the inner magnetosphere. On August 15, 2001 the four Cluster spacecraft located slightly dawnward of midnight (yGSM approx. -5.4RE) at xGSM approx. -18RE observed a series of earthward propagating dipolarization fronts [Hwang et al., 2010]. At least 6 dipolarization fronts were observed in a 20m interval. Unlike previously reported cases the fluxes of electrons up to 95keV decreased during the passage of the first three fronts over the spacecraft. The energetic electron fluxes increased during the passage of the last three fronts. We have performed a global magnetohydrodynamic simulation of this event using solar wind observations from the ACE satellite to drive the simulation. In the simulation a very complex reconnection system in the near-Earth tail at XGSM approx. -20RE launched a series of earthward propagating dipolarization fronts that are similar to those observed on Cluster. The simulation results indicate that the Cluster spacecraft were just earthward of the reconnection site. In this paper we will present a study of the dynamics of electrons associated with these events by using the large-scale kinetic simulation approach in which we launch a large number of electrons into the electric and magnetic fields from this simulation.
Simulating AIA observations of a flux rope ejection
NASA Astrophysics Data System (ADS)
Pagano, P.; Mackay, D. H.; Poedts, S.
2014-08-01
Context. Coronal mass ejections (CMEs) are the most violent phenomena observed on the Sun. Currently, extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. In particular, observations now show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. While this is the case, these observations are difficult to interpret in terms of basic physical mechanisms and quantities. To fully understand CMEs we need to compare equivalent quantities derived from both observations and theoretical models. This will aid in bridging the gap between observations and models. Aims: To this end, we aim to produce synthesised AIA observations from simulations of a flux rope ejection. To carry this out we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. Methods: We perform a simulation where a flux rope is ejected from the solar corona. From the density and temperature of the plasma in the simulation we synthesise AIA observations. The emission is then integrated along the line of sight using the instrumental response function of AIA. Results: We sythesise observations of AIA in the channels at 304 Å, 171 Å, 335 Å, and 94 Å. The synthesised observations show a number of features similar to actual observations and in particular reproduce the general development of CMEs in the low corona as observed by AIA. In particular we reproduce an erupting and expanding arcade in the 304 Å and 171 Å channels with a high density core. Conclusions: The ejection of a flux rope reproduces many of the features found in the AIA observations. This work is therefore a step forward in bridging the gap between observations and models, and can lead to more direct interpretations of EUV observations in terms of flux rope
Simulations of extragalactic magnetic fields and of their observables
NASA Astrophysics Data System (ADS)
Vazza, F.; Brüggen, M.; Gheller, C.; Hackstein, S.; Wittor, D.; Hinz, P. M.
2017-12-01
The origin of extragalactic magnetic fields is still poorly understood. Based on a dedicated suite of cosmological magneto-hydrodynamical simulations with the ENZO code we have performed a survey of different models that may have caused present-day magnetic fields in galaxies and galaxy clusters. The outcomes of these models differ in cluster outskirts, filaments, sheets and voids and we use these simulations to find observational signatures of magnetogenesis. With these simulations, we predict the signal of extragalactic magnetic fields in radio observations of synchrotron emission from the cosmic web, in Faraday rotation, in the propagation of ultra high energy cosmic rays, in the polarized signal from fast radio bursts at cosmological distance and in spectra of distant blazars. In general, primordial scenarios in which present-day magnetic fields originate from the amplification of weak (⩽nG ) uniform seed fields result in more homogeneous and relatively easier to observe magnetic fields than astrophysical scenarios, in which present-day fields are the product of feedback processes triggered by stars and active galaxies. In the near future the best evidence for the origin of cosmic magnetic fields will most likely come from a combination of synchrotron emission and Faraday rotation observed at the periphery of large-scale structures.
Validation: Codes to compare simulation data to various observations
NASA Astrophysics Data System (ADS)
Cohn, J. D.
2017-02-01
Validation provides codes to compare several observations to simulated data with stellar mass and star formation rate, simulated data stellar mass function with observed stellar mass function from PRIMUS or SDSS-GALEX in several redshift bins from 0.01-1.0, and simulated data B band luminosity function with observed stellar mass function, and to create plots for various attributes, including stellar mass functions, and stellar mass to halo mass. These codes can model predictions (in some cases alongside observational data) to test other mock catalogs.
NASA Technical Reports Server (NTRS)
Ackerman, Steven A.; Hemler, Richard S.; Hofman, Robert J. Patrick; Pincus, Robert; Platnick, Steven
2011-01-01
The properties of clouds that may be observed by satellite instruments, such as optical depth and cloud top pressure, are only loosely related to the way clouds m-e represented in models of the atmosphere. One way to bridge this gap is through "instrument simulators," diagnostic tools that map the model representation to synthetic observations so that differences between simulator output and observations can be interpreted unambiguously as model error. But simulators may themselves be restricted by limited information available from the host model or by internal assumptions. This paper considers the extent to which instrument simulators are able to capture essential differences between MODIS and ISCCP, two similar but independent estimates of cloud properties. The authors review the measurements and algorithms underlying these two cloud climatologies, introduce a MODIS simulator, and detail data sets developed for comparison with global models using ISCCP and MODIS simulators, In nature MODIS observes less mid-level doudines!> than ISCCP, consistent with the different methods used to determine cloud top pressure; aspects of this difference are reproduced by the simulators running in a climate modeL But stark differences between MODIS and ISCCP observations of total cloudiness and the distribution of cloud optical thickness can be traced to different approaches to marginal pixels, which MODIS excludes and ISCCP treats as homogeneous. These pixels, which likely contain broken clouds, cover about 15 k of the planet and contain almost all of the optically thinnest clouds observed by either instrument. Instrument simulators can not reproduce these differences because the host model does not consider unresolved spatial scales and so can not produce broken pixels. Nonetheless, MODIS and ISCCP observation are consistent for all but the optically-thinnest clouds, and models can be robustly evaluated using instrument simulators by excluding ambiguous observations.
Observational Tracers of Hot and Cold Gas in Isolated Galaxy Simulations
NASA Astrophysics Data System (ADS)
Brzycki, Bryan; Silvia, Devin
2018-01-01
We present results from an analysis comparing simulations of isolated spiral galaxies with recent observations of the circumgalactic medium (CGM). As the interface containing inflows and outflows between the interstellar and intergalactic media, the CGM plays an important role in the composition and evolution of galaxies. Using a set of isolated galaxy simulations over different initial conditions and star formation and feedback parameters, we investigate the evolution of CGM gas. Specifically, in light of recent observational studies, we compute the radial column density profiles and covering fractions of various observable ion species (H I, C IV, O VI, Mg II, Si III) for each simulated galaxy. Taking uniformly random sightlines through the CGM of each simulated galaxy, we find the abundance of gas absorbers and analyze their contribution to the overall column density along each sightline. By identifying the prevalence of high column density absorbers, we seek to characterize the distribution and evolution of observable ion species in the CGM. We also highlight a subset of our isolated galaxy simulations that produce and maintain a stable precipitating CGM that fuels high rates of sustained star formation. This project was supported in part by the NSF REU grant AST-1358980 and by the Nantucket Maria Mitchell Association.
Observations and statistical simulations of a proposed solar cycle/QBO/weather relationship
DOE Office of Scientific and Technical Information (OSTI.GOV)
Baldwin, M.P.; Dunkerton, T.J.
1989-08-01
The 10.7 cm solar flux is observed to be highly correlated with north pole stratospheric temperatures when partitioned according to the phase of the equatorial stratospheric winds (the quasi-biennial oscillation, or QBO). The authors supplement observations with calculations showing that temperatures over most of the northern hemisphere are highly correlated or anticorrelated with north pole temperatures. The observed spatial pattern of solar cycle correlations at high latitudes is shown to be not unique to the solar cycle. The authors present results, similar to the observed solar cycle correlations, with simulated harmonics of various periods replacing the solar cycle. These calculationsmore » demonstrate the correlations at least as high as those for the solar cycle results may be obtained using simulated harmonics.« less
NASA Astrophysics Data System (ADS)
Bonaccorsi, Rosalba; Stoker, Carol R.
2008-10-01
Science results from a field-simulated lander payload and post-mission laboratory investigations provided "ground truth" to interpret remote science observations made as part of the 2005 Mars Astrobiology Research and Technology Experiment (MARTE) drilling mission simulation. The experiment was successful in detecting evidence for life, habitability, and preservation potential of organics in a relevant astrobiological analogue of Mars. Science results. Borehole 7 was drilled near the Río Tinto headwaters at Peña de Hierro (Spain) in the upper oxidized remnant of an acid rock drainage system. Analysis of 29 cores (215 cm of core was recovered from 606 cm penetrated depth) revealed a matrix of goethite- (42-94%) and hematite-rich (47-87%) rocks with pockets of phyllosilicates (47-74%) and fine- to coarse-grained loose material. Post-mission X-ray diffraction (XRD) analysis confirmed the range of hematite:goethite mixtures that were visually recognizable (˜1:1, ˜1:2, and ˜1:3 mixtures displayed a yellowish-red color whereas 3:1 mixtures displayed a dark reddish-brown color). Organic carbon was poorly preserved in hematite/goethite-rich materials (Corg <0.05 wt %) beneath the biologically active organic-rich soil horizon (Corg ˜3-11 wt %) in contrast to the phyllosilicate-rich zones (Corg ˜0.23 wt %). Ground truth vs. remote science analysis. Laboratory-based analytical results were compared to the analyses obtained by a Remote Science Team (RST) using a blind protocol. Ferric iron phases, lithostratigraphy, and inferred geologic history were correctly identified by the RST with the exception of phyllosilicate-rich materials that were misinterpreted as weathered igneous rock. Adenosine 5‧-triphosphate (ATP) luminometry, a tool available to the RST, revealed ATP amounts above background noise, i.e., 278-876 Relative Luminosity Units (RLUs) in only 6 cores, whereas organic carbon was detected in all cores. Our manned vs. remote observations based on automated
Bonaccorsi, Rosalba; Stoker, Carol R
2008-10-01
Science results from a field-simulated lander payload and post-mission laboratory investigations provided "ground truth" to interpret remote science observations made as part of the 2005 Mars Astrobiology Research and Technology Experiment (MARTE) drilling mission simulation. The experiment was successful in detecting evidence for life, habitability, and preservation potential of organics in a relevant astrobiological analogue of Mars. SCIENCE RESULTS: Borehole 7 was drilled near the Río Tinto headwaters at Peña de Hierro (Spain) in the upper oxidized remnant of an acid rock drainage system. Analysis of 29 cores (215 cm of core was recovered from 606 cm penetrated depth) revealed a matrix of goethite- (42-94%) and hematite-rich (47-87%) rocks with pockets of phyllosilicates (47-74%) and fine- to coarse-grained loose material. Post-mission X-ray diffraction (XRD) analysis confirmed the range of hematite:goethite mixtures that were visually recognizable (approximately 1:1, approximately 1:2, and approximately 1:3 mixtures displayed a yellowish-red color whereas 3:1 mixtures displayed a dark reddish-brown color). Organic carbon was poorly preserved in hematite/goethite-rich materials (C(org) <0.05 wt %) beneath the biologically active organic-rich soil horizon (C(org) approximately 3-11 wt %) in contrast to the phyllosilicate-rich zones (C(org) approximately 0.23 wt %). GROUND TRUTH VS. REMOTE SCIENCE ANALYSIS: Laboratory-based analytical results were compared to the analyses obtained by a Remote Science Team (RST) using a blind protocol. Ferric iron phases, lithostratigraphy, and inferred geologic history were correctly identified by the RST with the exception of phyllosilicate-rich materials that were misinterpreted as weathered igneous rock. Adenosine 5'-triphosphate (ATP) luminometry, a tool available to the RST, revealed ATP amounts above background noise, i.e., 278-876 Relative Luminosity Units (RLUs) in only 6 cores, whereas organic carbon was detected in all
Understanding observed and simulated historical temperature trends in California
NASA Astrophysics Data System (ADS)
Bonfils, C. J.; Duffy, P. B.; Santer, B. D.; Lobell, D. B.; Wigley, T. M.
2006-12-01
In our study, we attempt 1) to improve our understanding of observed historical temperature trends and their underlying causes in the context of regional detection of climate change and 2) to identify possible neglected forcings and errors in the model response to imposed forcings at the origin of inconsistencies between models and observations. From eight different observational datasets, we estimate California-average temperature trends over 1950- 1999 and compare them to trends from a suite of IPCC control simulations of natural internal climate variability. We find that the substantial night-time warming occurring from January to September is inconsistent with model-based estimates of natural internal climate variability, and thus requires one or more external forcing agents to be explained. In contrast, we find that a significant day-time warming occurs only from January to March. Our confidence in these findings is increased because there is no evidence that the models systematically underestimate noise on interannual and decadal timescales. However, we also find that IPCC simulations of the 20th century that include combined anthropogenic and natural forcings are not able to reproduce such a pronounced seasonality of the trends. Our first hypothesis is that the warming of Californian winters over the second half of the twentieth century is associated with changes in large-scale atmospheric circulation that are likely to be human-induced. This circulation change is underestimated in the historical simulations, which may explain why the simulated warming of Californian winters is too weak. We also hypothesize that the lack of a detectable observed increase in summertime maximum temperature arises from a cooling associated with large-scale irrigation. This cooling may have, until now, counteracted the warming induced by increasing greenhouse gases and urbanization effects. Omitting to include this forcing in the simulations can result in overestimating the
Observations and simulations of the ionospheric lunar tide: Seasonal variability
NASA Astrophysics Data System (ADS)
Pedatella, N. M.
2014-07-01
The seasonal variability of the ionospheric lunar tide is investigated using a combination of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations and thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) simulations. The present study focuses on the seasonal variability of the lunar tide in the ionosphere and its potential connection to the occurrence of stratosphere sudden warmings (SSWs). COSMIC maximum F region electron density (NmF2) and total electron content observations reveal a primarily annual variation of the ionospheric lunar tide, with maximum amplitudes occurring at low latitudes during December-February. Simulations of the lunar tide climatology in TIME-GCM display a similar annual variability as the COSMIC observations. This leads to the conclusion that the annual variability of the lunar tide in the ionosphere is not solely due to the occurrence of SSWs. Rather, the annual variability of the lunar tide in the ionosphere is generated by the seasonal variability of the lunar tide at E region altitudes. However, compared to the observations, the ionospheric lunar tide annual variability is weaker in the climatological simulations which is attributed to the occurrence of SSWs during the majority of the years included in the observations. Introducing a SSW into the TIME-GCM simulation leads to an additional enhancement of the lunar tide during Northern Hemisphere winter, increasing the lunar tide annual variability and resulting in an annual variability that is more consistent with the observations. The occurrence of SSWs can therefore potentially bias lunar tide climatologies, and it is important to consider these effects in studies of the lunar tide in the atmosphere and ionosphere.
NASA Astrophysics Data System (ADS)
Anantua, Richard; Roger Blandford, Jonathan McKinney and Alexander Tchekhovskoy
2016-01-01
We carry out the process of "observing" simulations of active galactic nuclei (AGN) with relativistic jets (hereafter called jet/accretion disk/black hole (JAB) systems) from ray tracing between image plane and source to convolving the resulting images with a point spread function. Images are generated at arbitrary observer angle relative to the black hole spin axis by implementing spatial and temporal interpolation of conserved magnetohydrodynamic flow quantities from a time series of output datablocks from fully general relativistic 3D simulations. We also describe the evolution of simulations of JAB systems' dynamical and kinematic variables, e.g., velocity shear and momentum density, respectively, and the variation of these variables with respect to observer polar and azimuthal angles. We produce, at frequencies from radio to optical, fixed observer time intensity and polarization maps using various plasma physics motivated prescriptions for the emissivity function of physical quantities from the simulation output, and analyze the corresponding light curves. Our hypothesis is that this approach reproduces observed features of JAB systems such as superluminal bulk flow projections and quasi-periodic oscillations in the light curves more closely than extant stylized analytical models, e.g., cannonball bulk flows. Moreover, our development of user-friendly, versatile C++ routines for processing images of state-of-the-art simulations of JAB systems may afford greater flexibility for observing a wide range of sources from high power BL-Lacs to low power quasars (possibly with the same simulation) without requiring years of observation using multiple telescopes. Advantages of observing simulations instead of observing astrophysical sources directly include: the absence of a diffraction limit, panoramic views of the same object and the ability to freely track features. Light travel time effects become significant for high Lorentz factor and small angles between
NASA Astrophysics Data System (ADS)
Guidi, G.; Casado, J.; Ascasibar, Y.; García-Benito, R.; Galbany, L.; Sánchez-Blázquez, P.; Sánchez, S. F.; Rosales-Ortega, F. F.; Scannapieco, C.
2018-06-01
In this work we present a set of synthetic observations that mimic the properties of the Integral Field Spectroscopy (IFS) survey CALIFA, generated using radiative transfer techniques applied to hydrodynamical simulations of galaxies in a cosmological context. The simulated spatially-resolved spectra include stellar and nebular emission, kinematic broadening of the lines, and dust extinction and scattering. The results of the radiative transfer simulations have been post-processed to reproduce the main properties of the CALIFA V500 and V1200 observational setups. The data has been further formatted to mimic the CALIFA survey in terms of field of view size, spectral range and sampling. We have included the effect of the spatial and spectral Point Spread Functions affecting CALIFA observations, and added detector noise after characterizing it on a sample of 367 galaxies. The simulated datacubes are suited to be analysed by the same algorithms used on real IFS data. In order to provide a benchmark to compare the results obtained applying IFS observational techniques to our synthetic datacubes, and test the calibration and accuracy of the analysis tools, we have computed the spatially-resolved properties of the simulations. Hence, we provide maps derived directly from the hydrodynamical snapshots or the noiseless spectra, in a way that is consistent with the values recovered by the observational analysis algorithms. Both the synthetic observations and the product datacubes are public and can be found in the collaboration website http://astro.ft.uam.es/selgifs/data_challenge/.
Charaterizing the O+ ion plume from Hybrid simulations: comparison to MAVEN observations
NASA Astrophysics Data System (ADS)
Modolo, R.; Leblanc, F.; Chaufray, J. Y.; Leclercq, L.; Esteban-Hernandez, R.; Curry, S.; Dong, Y.; Brain, D. A.; Bowers, C.; Luhmann, J. G.; McFadden, J. P.; Halekas, J. S.; Espley, J. R.; Connerney, J. E. P.; Jakosky, B. M.
2015-12-01
MAVEN observations show a substantial plume-like distribution of escaping ions from the Martian atmosphere. It represents an important ion escape channel with large fluxes (Brain et al, 2015; Dong et al, 2015, Curry et al, 2015). Such structure is organized by the solar wind convection electric field and it is located in the MSE northward hemisphere. Global hybrid models (eg Modolo et al, 2005, 2012; Kallio et al, 2006; Brecht et al, 2006) reproduce nicely this plume. To further characterize this population, hybrid simulations have been performed with upstream solar wind conditions observed by MAVEN. Simulation results along the spacecraft track present signatures of high energetic O+ ions similar to MAVEN measurements. Comparison of simulated 3D distribution functions of this population are compared to STATIC and SWIA observations. Moreover a comparison of hybrid results with statistical ion fluxes maps derived from MAVEN (Dong et al, 2015; Brain et al, 2015) have been conducted and a reasonable agreement is found .
Properties of the circumgalactic medium in simulations compared to observations
NASA Astrophysics Data System (ADS)
Machado, R. E. G.; Tissera, P. B.; Lima Neto, G. B.; Sodré, L.
2018-01-01
Context. Galaxies are surrounded by extended gaseous halos that store significant fractions of chemical elements. These are syntethized by the stellar populations and later ejected into the circumgalactic medium (CGM) by different mechanism, of which supernova feedback is considered one of the most relevant. Aims: We aim to explore the properties of this metal reservoir surrounding star-forming galaxies in a cosmological context aiming to investigate the chemical loop between galaxies and their CGM, and the ability of the subgrid models to reproduce observational results. Methods: Using cosmological hydrodynamical simulations, we have analysed the gas-phase chemical contents of galaxies with stellar masses in the range 109-1011 M⊙. We estimated the fractions of metals stored in the different CGM phases, and the predicted O VI and Si III column densities within the virial radius. Results: We find roughly 107 M⊙ of oxygen in the CGM of simulated galaxies having M⋆ 1010 M⊙, in fair agreement with the lower limits imposed by observations. The Moxy is found to correlate with M⋆, at odds with current observational trends but in agreement with other numerical results. The estimated profiles of O VI column density reveal a substantial shortage of that ion, whereas Si III, which probes the cool phase, is overpredicted. Nevertheless, the radial dependences of both ions follow the respective observed profiles. The analysis of the relative contributions of both ions from the hot, warm and cool phases suggests that the warm gas (105 K < T < 106 K) should be more abundant in order to bridge the mismatch with the observations, or alternatively, that more metals should be stored in this gas-phase. These discrepancies provide important information to improve the subgrid physics models. Our findings show clearly the importance of tracking more than one chemical element and the difficulty of simultaneously satisfying the observables that trace the circumgalactic gas at
Percolation analyses of observed and simulated galaxy clustering
NASA Astrophysics Data System (ADS)
Bhavsar, S. P.; Barrow, J. D.
1983-11-01
A percolation cluster analysis is performed on equivalent regions of the CFA redshift survey of galaxies and the 4000 body simulations of gravitational clustering made by Aarseth, Gott and Turner (1979). The observed and simulated percolation properties are compared and, unlike correlation and multiplicity function analyses, favour high density (Omega = 1) models with n = - 1 initial data. The present results show that the three-dimensional data are consistent with the degree of filamentary structure present in isothermal models of galaxy formation at the level of percolation analysis. It is also found that the percolation structure of the CFA data is a function of depth. Percolation structure does not appear to be a sensitive probe of intrinsic filamentary structure.
Magnetoacoustic Wave Energy from Numerical Simulations of an Observed Sunspot Umbra
NASA Astrophysics Data System (ADS)
Felipe, T.; Khomenko, E.; Collados, M.
2011-07-01
We aim at reproducing the height dependence of sunspot wave signatures obtained from spectropolarimetric observations through three-dimensional MHD numerical simulations. A magnetostatic sunspot model based on the properties of the observed sunspot is constructed and perturbed at the photosphere, introducing the fluctuations measured with the Si I λ10827 line. The results of the simulations are compared with the oscillations observed simultaneously at different heights from the He I λ10830 line, the Ca II H core, and the Fe I blends in the wings of the Ca II H line. The simulations show a remarkable agreement with the observations. They reproduce the velocity maps and power spectra at the formation heights of the observed lines, as well as the phase and amplification spectra between several pairs of lines. We find that the stronger shocks at the chromosphere are accompanied with a delay between the observed signal and the simulated one at the corresponding height, indicating that shocks shift the formation height of the chromospheric lines to higher layers. Since the simulated wave propagation matches very well the properties of the observed one, we are able to use the numerical calculations to quantify the energy contribution of the magnetoacoustic waves to the chromospheric heating in sunspots. Our findings indicate that the energy supplied by these waves is too low to balance the chromospheric radiative losses. The energy contained at the formation height of the lowermost Si I λ10827 line in the form of slow magnetoacoustic waves is already insufficient to heat the higher layers, and the acoustic energy which reaches the chromosphere is around 3-9 times lower than the required amount of energy. The contribution of the magnetic energy is even lower.
NASA Technical Reports Server (NTRS)
Pi, Xiaoqing; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Stephens, Philip; Wilson, Brian D.; Akopian, Vardan; Komjathy, Attila; Lijima, Byron A.
2013-01-01
ISOGAME is designed and developed to assess quantitatively the impact of new observation systems on the capability of imaging and modeling the ionosphere. With ISOGAME, one can perform observation system simulation experiments (OSSEs). A typical OSSE using ISOGAME would involve: (1) simulating various ionospheric conditions on global scales; (2) simulating ionospheric measurements made from a constellation of low-Earth-orbiters (LEOs), particularly Global Navigation Satellite System (GNSS) radio occultation data, and from ground-based global GNSS networks; (3) conducting ionospheric data assimilation experiments with the Global Assimilative Ionospheric Model (GAIM); and (4) analyzing modeling results with visualization tools. ISOGAME can provide quantitative assessment of the accuracy of assimilative modeling with the interested observation system. Other observation systems besides those based on GNSS are also possible to analyze. The system is composed of a suite of software that combines the GAIM, including a 4D first-principles ionospheric model and data assimilation modules, an Internal Reference Ionosphere (IRI) model that has been developed by international ionospheric research communities, observation simulator, visualization software, and orbit design, simulation, and optimization software. The core GAIM model used in ISOGAME is based on the GAIM++ code (written in C++) that includes a new high-fidelity geomagnetic field representation (multi-dipole). New visualization tools and analysis algorithms for the OSSEs are now part of ISOGAME.
Observer roles that optimise learning in healthcare simulation education: a systematic review.
O'Regan, Stephanie; Molloy, Elizabeth; Watterson, Leonie; Nestel, Debra
2016-01-01
Simulation is widely used in health professional education. The convention that learners are actively involved may limit access to this educational method. The aim of this paper is to review the evidence for learning methods that employ directed observation as an alternative to hands-on participation in scenario-based simulation training. We sought studies that included either direct comparison of the learning outcomes of observers with those of active participants or identified factors important for the engagement of observers in simulation. We systematically searched health and education databases and reviewed journals and bibliographies for studies investigating or referring to observer roles in simulation using mannequins, simulated patients or role play simulations. A quality framework was used to rate the studies. We sought studies that included either direct comparison of the learning outcomes of observers with those of active participants or identified factors important for the engagement of observers in simulation. We systematically searched health and education databases and reviewed journals and bibliographies for studies investigating or referring to observer roles in simulation using mannequins, simulated patients or role play simulations. A quality framework was used to rate the studies. Nine studies met the inclusion criteria. Five studies suggest learning outcomes in observer roles are as good or better than hands-on roles in simulation. Four studies document learner satisfaction in observer roles. Five studies used a tool to guide observers. Eight studies involved observers in the debrief. Learning and satisfaction in observer roles is closely associated with observer tools, learner engagement, role clarity and contribution to the debrief. Learners that valued observer roles described them as affording an overarching view, examination of details from a distance, and meaningful feedback during the debrief. Learners who did not value observer roles
Temporal Variability of Observed and Simulated Hyperspectral Earth Reflectance
NASA Technical Reports Server (NTRS)
Roberts, Yolanda; Pilewskie, Peter; Kindel, Bruce; Feldman, Daniel; Collins, William D.
2012-01-01
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system designed to study Earth's climate variability with unprecedented absolute radiometric accuracy and SI traceability. Observation System Simulation Experiments (OSSEs) were developed using GCM output and MODTRAN to simulate CLARREO reflectance measurements during the 21st century as a design tool for the CLARREO hyperspectral shortwave imager. With OSSE simulations of hyperspectral reflectance, Feldman et al. [2011a,b] found that shortwave reflectance is able to detect changes in climate variables during the 21st century and improve time-to-detection compared to broadband measurements. The OSSE has been a powerful tool in the design of the CLARREO imager and for understanding the effect of climate change on the spectral variability of reflectance, but it is important to evaluate how well the OSSE simulates the Earth's present-day spectral variability. For this evaluation we have used hyperspectral reflectance measurements from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), a shortwave spectrometer that was operational between March 2002 and April 2012. To study the spectral variability of SCIAMACHY-measured and OSSE-simulated reflectance, we used principal component analysis (PCA), a spectral decomposition technique that identifies dominant modes of variability in a multivariate data set. Using quantitative comparisons of the OSSE and SCIAMACHY PCs, we have quantified how well the OSSE captures the spectral variability of Earth?s climate system at the beginning of the 21st century relative to SCIAMACHY measurements. These results showed that the OSSE and SCIAMACHY data sets share over 99% of their total variance in 2004. Using the PCs and the temporally distributed reflectance spectra projected onto the PCs (PC scores), we can study the temporal variability of the observed and simulated reflectance spectra. Multivariate time
NASA Technical Reports Server (NTRS)
Berchem, J.; Raeder, J.; Walker, R. J.; Ashour-Abdalla, M.
1995-01-01
We report on the development of an interactive system for visualizing and analyzing numerical simulation results. This system is based on visualization modules which use the Application Visualization System (AVS) and the NCAR graphics packages. Examples from recent simulations are presented to illustrate how these modules can be used for displaying and manipulating simulation results to facilitate their comparison with phenomenological model results and observations.
An Observing System Simulation Experiment Approach to Meteorological Network Assessment
NASA Astrophysics Data System (ADS)
Abbasnezhadi, K.; Rasmussen, P. F.; Stadnyk, T.; Boluwade, A.
2016-12-01
A proper knowledge of the spatiotemporal distribution of rainfall is important in order to conduct a mindful investigation of water movement and storage throughout a catchment. Currently, the most accurate precipitation information available for the remote Boreal ecozones of northern Manitoba is coming from the Canadian Precipitation Analysis (CaPA) data assimilation system. Throughout the Churchill River Basin (CRB), CaPA still does not have the proper skill due to the limited number of weather stations. A new approach to experimental network design was investigated based on the concept of Observing System Simulation Experiment (OSSE). The OSSE-based network assessment procedure which simulates the CaPA system provides a scientific and hydrologically significant tool to assess the sensitivity of CaPA precipitation analysis to observation network density throughout the CRB. To simulate CaPA system, synthetic background and station data were simulated, respectively, by adding spatially uncorrelated and correlated Gaussian noises to an assumingly true daily weather field synthesized by a gridded precipitation generator which simulates CaPA data. Given the true reference field on one hand, and a set of pseudo-CaPA analyses associated with different network realizations on the other hand, a WATFLOOD hydrological model was employed to compare the modeled runoff. The simulations showed that as network density increases, the accuracy of CaPA precipitation products improves up to a certain limit beyond which adding more stations to the network does not result in further accuracy.
NASA Astrophysics Data System (ADS)
Zieleniewski, Simon; Thatte, Niranjan; Kendrew, Sarah; Houghton, Ryan; Tecza, Matthias; Clarke, Fraser; Fusco, Thierry; Swinbank, Mark
2014-07-01
With the next generation of extremely large telescopes commencing construction, there is an urgent need for detailed quantitative predictions of the scientific observations that these new telescopes will enable. Most of these new telescopes will have adaptive optics fully integrated with the telescope itself, allowing unprecedented spatial resolution combined with enormous sensitivity. However, the adaptive optics point spread function will be strongly wavelength dependent, requiring detailed simulations that accurately model these variations. We have developed a simulation pipeline for the HARMONI integral field spectrograph, a first light instrument for the European Extremely Large Telescope. The simulator takes high-resolution input data-cubes of astrophysical objects and processes them with accurate atmospheric, telescope and instrumental effects, to produce mock observed cubes for chosen observing parameters. The output cubes represent the result of a perfect data reduc- tion process, enabling a detailed analysis and comparison between input and output, showcasing HARMONI's capabilities. The simulations utilise a detailed knowledge of the telescope's wavelength dependent adaptive op- tics point spread function. We discuss the simulation pipeline and present an early example of the pipeline functionality for simulating observations of high redshift galaxies.
The Cloud Feedback Model Intercomparison Project Observational Simulator Package: Version 2
NASA Astrophysics Data System (ADS)
Swales, Dustin J.; Pincus, Robert; Bodas-Salcedo, Alejandro
2018-01-01
The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) gathers together a collection of observation proxies or satellite simulators
that translate model-simulated cloud properties to synthetic observations as would be obtained by a range of satellite observing systems. This paper introduces COSP2, an evolution focusing on more explicit and consistent separation between host model, coupling infrastructure, and individual observing proxies. Revisions also enhance flexibility by allowing for model-specific representation of sub-grid-scale cloudiness, provide greater clarity by clearly separating tasks, support greater use of shared code and data including shared inputs across simulators, and follow more uniform software standards to simplify implementation across a wide range of platforms. The complete package including a testing suite is freely available.
Simulating Cosmic Reionization and Its Observable Consequences
NASA Astrophysics Data System (ADS)
Shapiro, Paul
2017-01-01
I summarize recent progress in modelling the epoch of reionization by large- scale simulations of cosmic structure formation, radiative transfer and their interplay, which trace the ionization fronts that swept across the IGM, to predict observable signatures. Reionization by starlight from early galaxies affected their evolution, impacting reionization, itself, and imprinting the galaxies with a memory of reionization. Star formation suppression, e.g., may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for Cold Dark Matter. I describe CoDa (''Cosmic Dawn''), the first fully-coupled radiation-hydrodynamical simulation of reionization and galaxy formation in the Local Universe, in a volume large enough to model reionization globally but with enough resolving power to follow all the atomic-cooling galactic halos in that volume. A 90 Mpc box was simulated from a constrained realization of primordial fluctuations, chosen to reproduce present-day features of the Local Group, including the Milky Way and M31, and the local universe beyond, including the Virgo cluster. The new RAMSES-CUDATON hybrid CPU-GPU code took 11 days to perform this simulation on the Titan supercomputer at Oak Ridge National Laboratory, with 4096-cubed N-body particles for the dark matter and 4096-cubed cells for the atomic gas and ionizing radiation.
NASA Astrophysics Data System (ADS)
Kubota, Y.; Nagatsuma, T.; Den, M.; Nakamizo, A.; Matsumoto, H.; Tanaka, T.
2017-12-01
We are developing a numerical simulator for future space weather forecast using magnetosphere-ionosphere coupling global MHD simulation called REPPU (REProduce Plasma Universe) code. We investigate the validity of the MHD simulation result as compared with observation. In this study we simulate some events including both quiet and disturbed geomagnetic conditions using OMNIWeb solar wind data. The simulation results are compared with magnetic field observations from Michibiki satellite, which is on the quasi-zenith orbit (QZO). In quiet geomagnetic condition, magnetic field variations at QZO obtained from simulation results have good consistency as compared correspondence with those from Michibiki observation. In disturbed geomagnetic condition in which the Dst < -20 nT, however, V component of magnetic field variations from simulation results tend to deviate from observations especially at the night side. We consider that this deviation during disturbed geomagnetic condition might be due to tail and/or ring current enhancement which is already suggested by many other MHD simulation studies as compared with the magnetic field observation at geosynchronous orbit. In this presentation, we will discuss the cause of this discrepancy in more detail with studying the relationship between the magnetic field deviation and some parameters such as Dst and solar wind.
"Observing" the Circumnuclear Stars and Gas in Disk Galaxy Simulations
NASA Astrophysics Data System (ADS)
Cook, Angela; Hicks, Erin K. S.
2018-06-01
We present simulations based on theoretical models of common disk processes designed to represent potential inflow observed within the central 500 pc of local Seyfert galaxies. Mock observations of these n-body plus smoothed particle hydrodynamical simulations provide the conceptual framework in which to identify the driving inflow mechanism, for example nuclear bars, and to quantify to the inflow based on observable properties. From these mock observations the azimuthal average of the flux distribution, velocity dispersion, and velocity of both the stars and interstellar medium on scales of 50pc have been measured at a range of inclinations angles. A comparison of the simulated disk galaxies with these observed azimuthal averages in 40 Seyfert galaxies measured as part of the KONA (Keck OSIRIS Nearby AGN) survey will be presented.
Observability of ionospheric space-time structure with ISR: A simulation study
NASA Astrophysics Data System (ADS)
Swoboda, John; Semeter, Joshua; Zettergren, Matthew; Erickson, Philip J.
2017-02-01
The sources of error from electronically steerable array (ESA) incoherent scatter radar (ISR) systems are investigated both theoretically and with use of an open-source ISR simulator, developed by the authors, called Simulator for ISR (SimISR). The main sources of error incorporated in the simulator include statistical uncertainty, which arises due to nature of the measurement mechanism and the inherent space-time ambiguity from the sensor. SimISR can take a field of plasma parameters, parameterized by time and space, and create simulated ISR data at the scattered electric field (i.e., complex receiver voltage) level, subsequently processing these data to show possible reconstructions of the original parameter field. To demonstrate general utility, we show a number of simulation examples, with two cases using data from a self-consistent multifluid transport model. Results highlight the significant influence of the forward model of the ISR process and the resulting statistical uncertainty on plasma parameter measurements and the core experiment design trade-offs that must be made when planning observations. These conclusions further underscore the utility of this class of measurement simulator as a design tool for more optimal experiment design efforts using flexible ESA class ISR systems.
NASA Astrophysics Data System (ADS)
Hummels, Cameron
Computational hydrodynamical simulations are a very useful tool for understanding how galaxies form and evolve over cosmological timescales not easily revealed through observations. However, they are only useful if they reproduce the sorts of galaxies that we see in the real universe. One of the ways in which simulations of this sort tend to fail is in the prescription of stellar feedback, the process by which nascent stars return material and energy to their immediate environments. Careful treatment of this interaction in subgrid models, so-called because they operate on scales below the resolution of the simulation, is crucial for the development of realistic galaxy models. Equally important is developing effective methods for comparing simulation data against observations to ensure galaxy models which mimic reality and inform us about natural phenomena. This thesis examines the formation and evolution of galaxies and the observable characteristics of the resulting systems. We employ extensive use of cosmological hydrodynamical simulations in order to simulate and interpret the evolution of massive spiral galaxies like our own Milky Way. First, we create a method for producing synthetic photometric images of grid-based hydrodynamical models for use in a direct comparison against observations in a variety of filter bands. We apply this method to a simulation of a cluster of galaxies to investigate the nature of the red-sequence/blue-cloud dichotomy in the galaxy color-magnitude diagram. Second, we implement several subgrid models governing the complex behavior of gas and stars on small scales in our galaxy models. Several numerical simulations are conducted with similar initial conditions, where we systematically vary the subgrid models, afterward assessing their efficacy through comparisons of their internal kinematics with observed systems. Third, we generate an additional method to compare observations with simulations, focusing on the tenuous circumgalactic
Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations
NASA Astrophysics Data System (ADS)
McCoy, Daniel T.; Field, Paul R.; Schmidt, Anja; Grosvenor, Daniel P.; Bender, Frida A.-M.; Shipway, Ben J.; Hill, Adrian A.; Wilkinson, Jonathan M.; Elsaesser, Gregory S.
2018-04-01
Aerosol-cloud interactions are a major source of uncertainty in inferring the climate sensitivity from the observational record of temperature. The adjustment of clouds to aerosol is a poorly constrained aspect of these aerosol-cloud interactions. Here, we examine the response of midlatitude cyclone cloud properties to a change in cloud droplet number concentration (CDNC). Idealized experiments in high-resolution, convection-permitting global aquaplanet simulations with constant CDNC are compared to 13 years of remote-sensing observations. Observations and idealized aquaplanet simulations agree that increased warm conveyor belt (WCB) moisture flux into cyclones is consistent with higher cyclone liquid water path (CLWP). When CDNC is increased a larger LWP is needed to give the same rain rate. The LWP adjusts to allow the rain rate to be equal to the moisture flux into the cyclone along the WCB. This results in an increased CLWP for higher CDNC at a fixed WCB moisture flux in both observations and simulations. If observed cyclones in the top and bottom tercile of CDNC are contrasted it is found that they have not only higher CLWP but also cloud cover and albedo. The difference in cyclone albedo between the cyclones in the top and bottom third of CDNC is observed by CERES to be between 0.018 and 0.032, which is consistent with a 4.6-8.3 Wm-2 in-cyclone enhancement in upwelling shortwave when scaled by annual-mean insolation. Based on a regression model to observed cyclone properties, roughly 60 % of the observed variability in CLWP can be explained by CDNC and WCB moisture flux.
Observations and Simulations of Formation of Broad Plasma Depletions Through Merging Process
NASA Technical Reports Server (NTRS)
Huang, Chao-Song; Retterer, J. M.; Beaujardiere, O. De La; Roddy, P. A.; Hunton, D.E.; Ballenthin, J. O.; Pfaff, Robert F.
2012-01-01
Broad plasma depletions in the equatorial ionosphere near dawn are region in which the plasma density is reduced by 1-3 orders of magnitude over thousands of kilometers in longitude. This phenomenon is observed repeatedly by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during deep solar minimum. The plasma flow inside the depletion region can be strongly upward. The possible causal mechanism for the formation of broad plasma depletions is that the broad depletions result from merging of multiple equatorial plasma bubbles. The purpose of this study is to demonstrate the feasibility of the merging mechanism with new observations and simulations. We present C/NOFS observations for two cases. A series of plasma bubbles is first detected by C/NOFS over a longitudinal range of 3300-3800 km around midnight. Each of the individual bubbles has a typical width of approx 100 km in longitude, and the upward ion drift velocity inside the bubbles is 200-400 m/s. The plasma bubbles rotate with the Earth to the dawn sector and become broad plasma depletions. The observations clearly show the evolution from multiple plasma bubbles to broad depletions. Large upward plasma flow occurs inside the depletion region over 3800 km in longitude and exists for approx 5 h. We also present the numerical simulations of bubble merging with the physics-based low-latitude ionospheric model. It is found that two separate plasma bubbles join together and form a single, wider bubble. The simulations show that the merging process of plasma bubbles can indeed occur in incompressible ionospheric plasma. The simulation results support the merging mechanism for the formation of broad plasma depletions.
NASA Astrophysics Data System (ADS)
Bianchini, Paolo; Norris, Mark A.; van de Ven, Glenn; Schinnerer, Eva
2015-10-01
The detection of intermediate-mass black holes in the centres of globular clusters is highly controversial, as complementary observational methods often deliver significantly different results. In order to understand these discrepancies, we develop a procedure to simulate integral field unit (IFU) observations of globular clusters: Simulating IFU Star Cluster Observations (SISCO). The inputs of our software are realistic dynamical models of globular clusters that are then converted in a spectral data cube. We apply SISCO to Monte Carlo cluster simulations with a realistic number of stars and concentrations. Using independent realizations of a given simulation we are able to quantify the stochasticity intrinsic to the problem of observing a partially resolved stellar population with integrated-light spectroscopy. We show that the luminosity-weighted IFU observations can be strongly biased by the presence of a few bright stars that introduce a scatter in the velocity dispersion measurements up to ≃40 per cent around the expected value, preventing any sound assessment of the central kinematic and a sensible interpretation of the presence/absence of an intermediate-mass black hole. Moreover, we illustrate that, in our mock IFU observations, the average kinematic tracer has a mass of ≃0.75 M⊙, only slightly lower than the mass of the typical stars examined in studies of resolved line-of-sight velocities of giant stars. Finally, in order to recover unbiased kinematic measurements we test different masking techniques that allow us to remove the spaxels dominated by bright stars, bringing the scatter down to a level of only a few per cent. The application of SISCO will allow us to investigate state-of-the-art simulations as realistic observations.
Comparing models of star formation simulating observed interacting galaxies
NASA Astrophysics Data System (ADS)
Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.
2017-07-01
In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.
Ryan, Patrick B; Schuemie, Martijn J
2013-10-01
There has been only limited evaluation of statistical methods for identifying safety risks of drug exposure in observational healthcare data. Simulations can support empirical evaluation, but have not been shown to adequately model the real-world phenomena that challenge observational analyses. To design and evaluate a probabilistic framework (OSIM2) for generating simulated observational healthcare data, and to use this data for evaluating the performance of methods in identifying associations between drug exposure and health outcomes of interest. Seven observational designs, including case-control, cohort, self-controlled case series, and self-controlled cohort design were applied to 399 drug-outcome scenarios in 6 simulated datasets with no effect and injected relative risks of 1.25, 1.5, 2, 4, and 10, respectively. Longitudinal data for 10 million simulated patients were generated using a model derived from an administrative claims database, with associated demographics, periods of drug exposure derived from pharmacy dispensings, and medical conditions derived from diagnoses on medical claims. Simulation validation was performed through descriptive comparison with real source data. Method performance was evaluated using Area Under ROC Curve (AUC), bias, and mean squared error. OSIM2 replicates prevalence and types of confounding observed in real claims data. When simulated data are injected with relative risks (RR) ≥ 2, all designs have good predictive accuracy (AUC > 0.90), but when RR < 2, no methods achieve 100 % predictions. Each method exhibits a different bias profile, which changes with the effect size. OSIM2 can support methodological research. Results from simulation suggest method operating characteristics are far from nominal properties.
Observational Simulation of Icing in Extreme Weather Conditions
NASA Astrophysics Data System (ADS)
Gultepe, Ismail; Heymsfield, Andrew; Agelin-Chaab, Martin; Komar, John; Elfstrom, Garry; Baumgardner, Darrel
2017-04-01
Observations and prediction of icing in extreme weather conditions are important for aviation, transportation, and shipping applications, and icing adversely affects the economy. Icing environments can be studied either in the outdoor atmosphere or in the laboratory. There have been several aircraft based in-situ studies related to weather conditions affecting aviation operations, transportation, and marine shipping that includes icing, wind, and turbulence. However, studying severe weather conditions from aircraft observations are limited due to safety and sampling issues, instrumental uncertainties, and even the possibility of aircraft producing its own physical and dynamical effects. Remote sensing based techniques (e.g. retrieval techniques) for studying severe weather conditions represent usually a volume that cannot characterize the important scales and also represents indirect observations. Therefore, laboratory simulations of atmospheric processes can help us better understand the interactions among microphysical and dynamical processes. The Climatic Wind Tunnel (CWT) in ACE at the University of Ontario Institute of Technology (UOIT) has a large semi-open jet test chamber with flow area 7-13 m2 that can precisely control temperatures down to -40°C, and up to 250 km hr-1 wind speeds, for heavy or dry snow conditions with low visibility, similar to ones observed in the Arctic and cold climate regions, or at high altitude aeronautical conditions. In this study, the ACE CWT employed a spray nozzle array suspended in its settling chamber and fed by pressurized water, creating various particle sizes from a few microns up to mm size range. This array, together with cold temperature and high wind speed, enabled simulation of severe weather conditions, including icing, visibility, strong wind and turbulence, ice fog and frost, freezing fog, heavy snow and blizzard conditions. In this study, the test results will be summarized, and their application to aircraft
Observation and simulation of the ionosphere disturbance waves triggered by rocket exhausts
NASA Astrophysics Data System (ADS)
Lin, Charles C. H.; Chen, Chia-Hung; Matsumura, Mitsuru; Lin, Jia-Ting; Kakinami, Yoshihiro
2017-08-01
Observations and theoretical modeling of the ionospheric disturbance waves generated by rocket launches are investigated. During the rocket passage, time rate change of total electron content (rTEC) enhancement with the V-shape shock wave signature is commonly observed, followed by acoustic wave disturbances and region of negative rTEC centered along the trajectory. Ten to fifteen min after the rocket passage, delayed disturbance waves appeared and propagated along direction normal to the V-shape wavefronts. These observation features appeared most prominently in the 2016 North Korea rocket launch showing a very distinct V-shape rTEC enhancement over enormous areas along the southeast flight trajectory despite that it was also appeared in the 2009 North Korea rocket launch with the eastward flight trajectory. Numerical simulations using the physical-based nonlinear and nonhydrostatic coupled model of neutral atmosphere and ionosphere reproduce promised results in qualitative agreement with the characteristics of ionospheric disturbance waves observed in the 2009 event by considering the released energy of the rocket exhaust as the disturbance source. Simulations reproduce the shock wave signature of electron density enhancement, acoustic wave disturbances, the electron density depletion due to the rocket-induced pressure bulge, and the delayed disturbance waves. The pressure bulge results in outward neutral wind flows carrying neutrals and plasma away from it and leading to electron density depletions. Simulations further show, for the first time, that the delayed disturbance waves are produced by the surface reflection of the earlier arrival acoustic wave disturbances.
Annual asymmetry in thermospheric density: Observations and simulations
NASA Astrophysics Data System (ADS)
Lei, Jiuhou; Dou, Xiankang; Burns, Alan; Wang, Wenbin; Luan, Xiaoli; Zeng, Zhen; Xu, Jiyao
2013-05-01
In this paper, the Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) observations during 2002-2010 are utilized to study the variation of the annual asymmetry in thermospheric density at 400 km under low solar activity condition (F10.7 = 80) based on the method of empirical orthogonal functions (EOFs). The derived asymmetry index (AI) in thermospheric density from the EOF analysis shows a strong latitudinal variation at night but varies a little with latitudes in daytime. Moreover, it exhibits a terdiurnal tidal signature at low to middle latitudes. The global mean value of the AI is 0.191, indicating that a 47% difference in thermosphere between the December and June solstices in the global average. In addition, the NCAR Thermosphere-Ionosphere Electrodynamics Global Circulation Model (TIEGCM) is used to explore the possible mechanisms responsible for the observed annual asymmetry in thermospheric density. It is found that the standard simulations give a lower AI and also a weaker day-to-night difference. The simulated AI shows a semidiurnal pattern in the equatorial and low-latitude regions in contrast with the terdiurnal tide signature seen in the observed AI. The daily mean AI obtained from the simulation is 0.125, corresponding to a 29% December-to-June difference in thermospheric density at 400 km. Further sensitivity simulations demonstrated that the effect of the varying Sun-Earth distance between the December and June solstices is the main process responsible for the annual asymmetry in thermospheric density, while the magnetic field configuration and tides from the lower atmosphere contribute to the temporal and spatial variations of the AI. Specifically, the simulations show that the Sun-Earth distance effect explains 93% of the difference in thermospheric density between December and June, which is mainly associated with the corresponding changes in neutral temperature. However, our calculation from the
NASA Technical Reports Server (NTRS)
Pincus, Robert; Platnick, Steven E.; Ackerman, Steve; Hemler, Richard; Hofmann, Patrick
2011-01-01
The properties of clouds that may be observed by satellite instruments, such as optical depth and cloud top pressure, are only loosely related to the way clouds are represented in models of the atmosphere. One way to bridge this gap is through "instrument simulators," diagnostic tools that map the model representation to synthetic observations so that differences between simulator output and observations can be interpreted unambiguously as model error. But simulators may themselves be restricted by limited information available from the host model or by internal assumptions. This work examines the extent to which instrument simulators are able to capture essential differences between MODIS and ISCCP, two similar but independent estimates of cloud properties. We focus on the stark differences between MODIS and ISCCP observations of total cloudiness and the distribution of cloud optical thickness can be traced to different approaches to marginal pixels, which MODIS excludes and ISCCP treats as homogeneous. These pixels, which likely contain broken clouds, cover about 15% of the planet and contain almost all of the optically thinnest clouds observed by either instrument. Instrument simulators can not reproduce these differences because the host model does not consider unresolved spatial scales and so can not produce broken pixels. Nonetheless, MODIS and ISCCP observation are consistent for all but the optically-thinnest clouds, and models can be robustly evaluated using instrument simulators by excluding ambiguous observations.
Reliable results from stochastic simulation models
Donald L., Jr. Gochenour; Leonard R. Johnson
1973-01-01
Development of a computer simulation model is usually done without fully considering how long the model should run (e.g. computer time) before the results are reliable. However construction of confidence intervals (CI) about critical output parameters from the simulation model makes it possible to determine the point where model results are reliable. If the results are...
NASA Astrophysics Data System (ADS)
Stanford, M.; Varble, A.; Zipser, E. J.; Strapp, J. W.; Leroy, D.; Schwarzenboeck, A.; Korolev, A.; Potts, R.
2016-12-01
A model intercomparison study is conducted to identify biases in simulated tropical convective core microphysical properties using two popular bulk parameterization schemes (Thompson and Morrison) and the Fast Spectral Bin Microphysics (FSBM) scheme. In-situ aircraft measurements of total condensed water content (TWC) and particle size distributions are compared with output from high-resolution WRF simulations of 4 mesoscale convective system (MCS) cases during the High Altitude Ice Crystals-High Ice Water Content (HAIC-HIWC) field campaign conducted in Darwin, Australia in 2014 and Cayenne, French Guiana in 2015. Observations of TWC collected using an isokinetic evaporator probe (IKP) optimized for high IWC measurements in conjunction with particle image processing from two optical array probes aboard the Falcon-20 research aircraft were used to constrain mass-size relationships in the observational dataset. Hydrometeor mass size distributions are compared between retrievals and simulations providing insight into the well-known high bias in simulated convective radar reflectivity. For TWC > 1 g m-3 between -10 and -40°C, simulations generally produce significantly greater median mass diameters (MMDs). Observations indicate that a sharp particle size mode occurs at 300 μm for large TWC values (> 2 g m-3) regardless of temperature. All microphysics schemes fail to reproduce this feature, and relative contributions of different hydrometeor species to this size bias vary between schemes. Despite far greater sample sizes, simulations also fail to produce high TWC conditions with very little of the mass contributed by large particles for a range of temperatures, despite such conditions being observed. Considering vapor grown particles alone in comparison with observations fails to correct the bias present in all schemes. Decreasing horizontal resolution from 1 km to 333 m shifts graupel and rain size distributions to slightly smaller sizes, but increased resolution
NASA Astrophysics Data System (ADS)
Vogelmann, A. M.; Gustafson, W. I., Jr.; Toto, T.; Endo, S.; Cheng, X.; Li, Z.; Xiao, H.
2015-12-01
The Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facilities' Large-Eddy Simulation (LES) ARM Symbiotic Simulation and Observation (LASSO) Workflow is currently being designed to provide output from routine LES to complement its extensive observations. The modeling portion of the LASSO workflow is presented by Gustafson et al., which will initially focus on shallow convection over the ARM megasite in Oklahoma, USA. This presentation describes how the LES output will be combined with observations to construct multi-dimensional and dynamically consistent "data cubes", aimed at providing the best description of the atmospheric state for use in analyses by the community. The megasite observations are used to constrain large-eddy simulations that provide a complete spatial and temporal coverage of observables and, further, the simulations also provide information on processes that cannot be observed. Statistical comparisons of model output with their observables are used to assess the quality of a given simulated realization and its associated uncertainties. A data cube is a model-observation package that provides: (1) metrics of model-observation statistical summaries to assess the simulations and the ensemble spread; (2) statistical summaries of additional model property output that cannot be or are very difficult to observe; and (3) snapshots of the 4-D simulated fields from the integration period. Searchable metrics are provided that characterize the general atmospheric state to assist users in finding cases of interest, such as categorization of daily weather conditions and their specific attributes. The data cubes will be accompanied by tools designed for easy access to cube contents from within the ARM archive and externally, the ability to compare multiple data streams within an event as well as across events, and the ability to use common grids and time sampling, where appropriate.
Evolution of Flow channels and Dipolarization Using THEMIS Observations and Global MHD Simulations
NASA Astrophysics Data System (ADS)
El-Alaoui, M.; McPherron, R. L.; Nishimura, Y.
2017-12-01
We have extensively analyzed a substorm on March 14, 2008 for which we have observations from THEMIS spacecraft located beyond 9 RE near 2100 local time. The available data include an extensive network of all sky cameras and ground magnetometers that establish the times of various auroral and magnetic events. This arrangement provided an excellent data set with which to investigate meso-scale structures in the plasma sheet. We have used a global magnetohydrodynamic simulation to investigate the structure and dynamics of the magnetotail current sheet during this substorm. Both earthward and tailward flows were found in the observations as well as the simulations. The simulation shows that the flow channels follow tortuous paths that are often reflected or deflected before arriving at the inner magnetosphere. The simulation shows a sequence of fast flows and dipolarization events similar to what is seen in the data, though not at precisely the same times or locations. We will use our simulation results combined with the observations to investigate the global convection systems and current sheet structure during this event, showing how meso-scale structures fit into the context of the overall tail dynamics during this event. Our study includes determining the location, timing and strength of several current wedges and expansion onsets during an 8-hour interval.
QUANTIFYING OBSERVATIONAL PROJECTION EFFECTS USING MOLECULAR CLOUD SIMULATIONS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Beaumont, Christopher N.; Offner, Stella S.R.; Shetty, Rahul
2013-11-10
The physical properties of molecular clouds are often measured using spectral-line observations, which provide the only probes of the clouds' velocity structure. It is hard, though, to assess whether and to what extent intensity features in position-position-velocity (PPV) space correspond to 'real' density structures in position-position-position (PPP) space. In this paper, we create synthetic molecular cloud spectral-line maps of simulated molecular clouds, and present a new technique for measuring the reality of individual PPV structures. Using a dendrogram algorithm, we identify hierarchical structures in both PPP and PPV space. Our procedure projects density structures identified in PPP space into correspondingmore » intensity structures in PPV space and then measures the geometric overlap of the projected structures with structures identified from the synthetic observation. The fractional overlap between a PPP and PPV structure quantifies how well the synthetic observation recovers information about the three-dimensional structure. Applying this machinery to a set of synthetic observations of CO isotopes, we measure how well spectral-line measurements recover mass, size, velocity dispersion, and virial parameter for a simulated star-forming region. By disabling various steps of our analysis, we investigate how much opacity, chemistry, and gravity affect measurements of physical properties extracted from PPV cubes. For the simulations used here, which offer a decent, but not perfect, match to the properties of a star-forming region like Perseus, our results suggest that superposition induces a ∼40% uncertainty in masses, sizes, and velocity dispersions derived from {sup 13}CO (J = 1-0). As would be expected, superposition and confusion is worst in regions where the filling factor of emitting material is large. The virial parameter is most affected by superposition, such that estimates of the virial parameter derived from PPV and PPP information typically
NASA Astrophysics Data System (ADS)
Jin, Yi; Gu, Yonggang; Zhai, Chao
2012-09-01
Multi-Object Fiber Spectroscopic sky surveys are now booming, such as LAMOST already built by China, BIGBOSS project put forward by the U.S. Lawrence Berkeley National Lab and GTC (Gran Telescopio Canarias) telescope developed by the United States, Mexico and Spain. They all use or will use this approach and each fiber can be moved within a certain area for one astrology target, so observation planning is particularly important for this Sky Surveys. One observation planning algorithm used in multi-objective astronomical observations is developed. It can avoid the collision and interference between the fiber positioning units in the focal plane during the observation in one field of view, and the interested objects can be ovserved in a limited round with the maximize efficiency. Also, the observation simulation can be made for wide field of view through multi-FOV observation. After the observation planning is built ,the simulation is made in COSMOS field using GTC telescope. Interested galaxies, stars and high-redshift LBG galaxies are selected after the removal of the mask area, which may be bright stars. Then 9 FOV simulation is completed and observation efficiency and fiber utilization ratio for every round are given. Otherwise,allocating a certain number of fibers for background sky, giving different weights for different objects and how to move the FOV to improve the overall observation efficiency are discussed.
GCM simulations of Titan's middle and lower atmosphere and comparison to observations
NASA Astrophysics Data System (ADS)
Lora, Juan M.; Lunine, Jonathan I.; Russell, Joellen L.
2015-04-01
Simulation results are presented from a new general circulation model (GCM) of Titan, the Titan Atmospheric Model (TAM), which couples the Flexible Modeling System (FMS) spectral dynamical core to a suite of external/sub-grid-scale physics. These include a new non-gray radiative transfer module that takes advantage of recent data from Cassini-Huygens, large-scale condensation and quasi-equilibrium moist convection schemes, a surface model with "bucket" hydrology, and boundary layer turbulent diffusion. The model produces a realistic temperature structure from the surface to the lower mesosphere, including a stratopause, as well as satisfactory superrotation. The latter is shown to depend on the dynamical core's ability to build up angular momentum from surface torques. Simulated latitudinal temperature contrasts are adequate, compared to observations, and polar temperature anomalies agree with observations. In the lower atmosphere, the insolation distribution is shown to strongly impact turbulent fluxes, and surface heating is maximum at mid-latitudes. Surface liquids are unstable at mid- and low-latitudes, and quickly migrate poleward. The simulated humidity profile and distribution of surface temperatures, compared to observations, corroborate the prevalence of dry conditions at low latitudes. Polar cloud activity is well represented, though the observed mid-latitude clouds remain somewhat puzzling, and some formation alternatives are suggested.
AOD trends during 2001-2010 from observations and model simulations
NASA Astrophysics Data System (ADS)
Pozzer, A.; de Meij, A.; Yoon, J.; Tost, H.; Georgoulias, A. K.; Astitha, M.
2015-05-01
The aerosol optical depth (AOD) trend between 2001 and 2010 is estimated globally and regionally from observations and results from simulations with the EMAC (ECHAM5/MESSy Atmospheric Chemistry) model. Although interannual variability is applied only to anthropogenic and biomass-burning emissions, the model is able to quantitatively reproduce the AOD trends as observed by the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite sensor, while some discrepancies are found when compared to MISR (Multi-angle Imaging SpectroRadiometer) and SeaWIFS (Sea-viewing Wide Field-of-view Sensor) observations. Thanks to an additional simulation without any change in emissions, it is shown that decreasing AOD trends over the US and Europe are due to the decrease in the emissions, while over the Sahara Desert and the Middle East region, the meteorological changes play a major role. Over Southeast Asia, both meteorology and emissions changes are equally important in defining AOD trends. Additionally, decomposing the regional AOD trends into individual aerosol components reveals that the soluble components are the most dominant contributors to the total AOD, as their influence on the total AOD is enhanced by the aerosol water content.
Summarizing Simulation Results using Causally-relevant States
Parikh, Nidhi; Marathe, Madhav; Swarup, Samarth
2016-01-01
As increasingly large-scale multiagent simulations are being implemented, new methods are becoming necessary to make sense of the results of these simulations. Even concisely summarizing the results of a given simulation run is a challenge. Here we pose this as the problem of simulation summarization: how to extract the causally-relevant descriptions of the trajectories of the agents in the simulation. We present a simple algorithm to compress agent trajectories through state space by identifying the state transitions which are relevant to determining the distribution of outcomes at the end of the simulation. We present a toy-example to illustrate the working of the algorithm, and then apply it to a complex simulation of a major disaster in an urban area. PMID:28042620
Coronal Mass Ejections and Dimmings: A Comparative Study using MHD Simulations and SDO Observations
NASA Astrophysics Data System (ADS)
Jin, M.; Cheung, C. M. M.; DeRosa, M. L.; Nitta, N.; Schrijver, K.
2017-12-01
Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings and determine their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-driven global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize the emissions of different EUV spectral bands/lines and compare with SDO/AIA and EVE observations. A detailed analysis of simulation and observation data suggests that although the transient dimming / brightening patterns could relate to plasma heating processes (either by adiabatic compression or reconnection), the long-lasting "core" and "remote" (also known as "secondary") dimmings both originate from regions with open/quasi-open fields and are caused by mass loss process. The mass loss in the remote dimming region is induced by CME-driven shock. Using metrics such as dimming depth, dimming slope, and recovery time, we investigate the relationship between dimmings and CME properties (e.g., CME mass, CME speed) in the simulation. Our result suggests that coronal dimmings encode important information about CME energetics, CME-driven shock properties, and magnetic configuration of erupting flux ropes. We also discuss how our knowledge about solar coronal dimmings could be extended to the study of stellar CMEs, which may prove important for exoplanet atmospheres and habitability but which are currently not observable.
Introduction to Observing System Simulation Experiments (OSSEs)
NASA Technical Reports Server (NTRS)
Prive, Nikki C.
2014-01-01
This presentation gives a brief overview of Observing System Simulation Experiments (OSSEs), including what OSSEs are, and how and why they are performed. The intent is to educate the audience in light of the OSSE-related sections of the Forecast Improvement Act (H.R. 2413).
SARDA HITL Simulations: System Performance Results
NASA Technical Reports Server (NTRS)
Gupta, Gautam
2012-01-01
This presentation gives an overview of the 2012 SARDA human-in-the-loop simulation, and presents a summary of system performance results from the simulation, including delay, throughput and fuel consumption
Whistler Observations on DEMETER Compared with Full Electromagnetic Wave Simulations
NASA Astrophysics Data System (ADS)
Compston, A. J.; Cohen, M.; Lehtinen, N. G.; Inan, U.; Linscott, I.; Said, R.; Parrot, M.
2014-12-01
Terrestrial Very Low Frequency (VLF) electromagnetic radiation, which strongly impacts the Van Allen radiation belt electron dynamics, is injected across the ionosphere into the Earth's plasmasphere from two primary sources: man-made VLF transmitters and lightning discharges. Numerical models of trans-ionospheric propagation of such waves remain unvalidated, and early models may have overestimated the absorption, hindering a comprehensive understanding of the global impact of VLF waves in the loss of radiation belt electrons. In an attempt to remedy the problem of a lack of accurate trans-ionospheric propagation models, we have used a full electromagnetic wave method (FWM) numerical code to simulate the propagation of lightning-generated whistlers into the magnetosphere and compared the results with whistlers observed on the DEMETER satellite and paired with lightning stroke data from the National Lightning Detection Network (NLDN). We have identified over 20,000 whistlers occuring in 14 different passes of DEMETER over the central United States during the summer of 2009, and 14,000 of those occured within the 2000 km x 2000 km simulation grid we used. As shown in the attached figure, which shows a histogram of the ratio of the simulated whistler energy to the measured whistler energy for the 14,000 whistlers we compared, the simulation tends to slightly underestimate the total whistler energy injected by about 5 dB. However, the simulation underestimates the DEMETER measurements more as one gets further from the source lightning stroke, so since the signal to noise ratio of more distant whistlers will be smaller, possibly additive noise in the DEMETER measurements (which of course is not accounted for in the model) may explain some of the observed discrepancy.
NASA Astrophysics Data System (ADS)
Flock, M.; Ruge, J. P.; Dzyurkevich, N.; Henning, Th.; Klahr, H.; Wolf, S.
2015-02-01
Aims: Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we wish to study axisymmetric and non-axisymmetric structures that are generated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generate synthetic maps and predictions for ALMA. Methods: We performed non-ideal global 3D magneto-hydrodynamic (MHD) stratified simulations of the dead-zone outer edge using the FARGO MHD code PLUTO. The stellar and disk parameters were taken from a parameterized disk model applied for fitting high-angular resolution multi-wavelength observations of various circumstellar disks. We considered a stellar mass of M∗ = 0.5 M⊙ and a total disk mass of about 0.085 M∗. The 2D initial temperature and density profiles were calculated consistently from a given surface density profile and Monte Carlo radiative transfer. The 2D Ohmic resistivity profile was calculated using a dust chemistry model. We considered two values for the dust-to-gas mass ratio, 10-2 and 10-4, which resulted in two different levels of magnetic coupling. The initial magnetic field was a vertical net flux field. The radiative transfer simulations were performed with the Monte Carlo-based 3D continuum RT code MC3D. The resulting dust reemission provided the basis for the simulation of observations with ALMA. Results: All models quickly turned into a turbulent state. The fiducial model with a dust-to-gas mass ratio of 10-2 developed a large gap followed by a jump in surface density located at the dead-zone outer edge. The jump in density and pressure was strong enough to stop the radial drift of particles at this location. In addition, we observed the generation of vortices by the Rossby wave instability at the jump location close to 60 AU
Asynchronous threat awareness by observer trials using crowd simulation
NASA Astrophysics Data System (ADS)
Dunau, Patrick; Huber, Samuel; Stein, Karin U.; Wellig, Peter
2016-10-01
The last few years showed that a high risk of asynchronous threats is given in every day life. Especially in large crowds a high probability of asynchronous attacks is evident. High observational abilities to detect threats are desirable. Consequently highly trained security and observation personal is needed. This paper evaluates the effectiveness of a training methodology to enhance performance of observation personnel engaging in a specific target identification task. For this purpose a crowd simulation video is utilized. The study first provides a measurement of the base performance before the training sessions. Furthermore a training procedure will be performed. Base performance will then be compared to the after training performance in order to look for a training effect. A thorough evaluation of both the training sessions as well as the overall performance will be done in this paper. A specific hypotheses based metric is used. Results will be discussed in order to provide guidelines for the design of training for observational tasks.
Quantitative Comparison of the Variability in Observed and Simulated Shortwave Reflectance
NASA Technical Reports Server (NTRS)
Roberts, Yolanda, L.; Pilewskie, P.; Kindel, B. C.; Feldman, D. R.; Collins, W. D.
2013-01-01
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system that has been designed to monitor the Earth's climate with unprecedented absolute radiometric accuracy and SI traceability. Climate Observation System Simulation Experiments (OSSEs) have been generated to simulate CLARREO hyperspectral shortwave imager measurements to help define the measurement characteristics needed for CLARREO to achieve its objectives. To evaluate how well the OSSE-simulated reflectance spectra reproduce the Earth s climate variability at the beginning of the 21st century, we compared the variability of the OSSE reflectance spectra to that of the reflectance spectra measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). Principal component analysis (PCA) is a multivariate decomposition technique used to represent and study the variability of hyperspectral radiation measurements. Using PCA, between 99.7%and 99.9%of the total variance the OSSE and SCIAMACHY data sets can be explained by subspaces defined by six principal components (PCs). To quantify how much information is shared between the simulated and observed data sets, we spectrally decomposed the intersection of the two data set subspaces. The results from four cases in 2004 showed that the two data sets share eight (January and October) and seven (April and July) dimensions, which correspond to about 99.9% of the total SCIAMACHY variance for each month. The spectral nature of these shared spaces, understood by examining the transformed eigenvectors calculated from the subspace intersections, exhibit similar physical characteristics to the original PCs calculated from each data set, such as water vapor absorption, vegetation reflectance, and cloud reflectance.
Atmospherical simulations of the OMEGA/MEX observations
NASA Astrophysics Data System (ADS)
Melchiorri, R.; Drossart, P.; Combes, M.; Encrenaz, T.; Fouchet, T.; Forget, F.; Bibring, J. P.; Ignatiev, N.; Moroz, V.; OMEGA Team
The modelization of the atmospheric contribution in the martian spectrum is an important step for the OMEGA data analysis.A full line by line radiative transfer calculation is made for the gas absorption; the dust opacity component, in a first approximation, is calculated as an optically thin additive component.Due to the large number of parameters needed in the calculations, the building of a huge data base to be interpolated is not envisageable, for each observed OMEGA spectrum with calculation for all the involved parameters (atmospheric pressure, water abundance, CO abundance, dust opacity and geometric angles of observation). The simulation of the observations allows us to fix all the orbital parameters and leave the unknown parameters as the only variables.Starting from the predictions of the current meteorological models of Mars we build a smaller data base corresponding on each observation. We present here a first order simulation, which consists in retrieving atmospheric contribution from the solar reflected component as a multiplicative (for gas absorption) and an additive component (for suspended dust contribution); although a fully consistent approach will require to include surface and atmosphere contributions together in synthetic calculations, this approach is sufficient for retrieving mineralogic information cleaned from atmospheric absorption at first order.First comparison to OMEGA spectra will be presented, with first order retrieval of CO2 pressure, CO and H2O abundance, and dust opacity.
An Introduction to Observing System Simulation Experiments
NASA Technical Reports Server (NTRS)
Prive, Nikki C.
2017-01-01
Observing System Simulation Experiments (OSSEs) are used to estimate the potential impact of proposed new instruments and data on numerical weather prediction. OSSEs can also be used to help design new observing platforms and to investigate the behavior of data assimilation systems. A basic overview of how to design and perform an OSSE will be given, as well as best practices and pitfalls. Some examples using the OSSE framework developed at the NASA Global Modeling and Assimilation Office will be shown.
The Aurora radiation-hydrodynamical simulations of reionization: calibration and first results
NASA Astrophysics Data System (ADS)
Pawlik, Andreas H.; Rahmati, Alireza; Schaye, Joop; Jeon, Myoungwon; Dalla Vecchia, Claudio
2017-04-01
We introduce a new suite of radiation-hydrodynamical simulations of galaxy formation and reionization called Aurora. The Aurora simulations make use of a spatially adaptive radiative transfer technique that lets us accurately capture the small-scale structure in the gas at the resolution of the hydrodynamics, in cosmological volumes. In addition to ionizing radiation, Aurora includes galactic winds driven by star formation and the enrichment of the universe with metals synthesized in the stars. Our reference simulation uses 2 × 5123 dark matter and gas particles in a box of size 25 h-1 comoving Mpc with a force softening scale of at most 0.28 h-1 kpc. It is accompanied by simulations in larger and smaller boxes and at higher and lower resolution, employing up to 2 × 10243 particles, to investigate numerical convergence. All simulations are calibrated to yield simulated star formation rate functions in close agreement with observational constraints at redshift z = 7 and to achieve reionization at z ≈ 8.3, which is consistent with the observed optical depth to reionization. We focus on the design and calibration of the simulations and present some first results. The median stellar metallicities of low-mass galaxies at z = 6 are consistent with the metallicities of dwarf galaxies in the Local Group, which are believed to have formed most of their stars at high redshifts. After reionization, the mean photoionization rate decreases systematically with increasing resolution. This coincides with a systematic increase in the abundance of neutral hydrogen absorbers in the intergalactic medium.
NASA Astrophysics Data System (ADS)
D'Alessandro, J.; Diao, M.; Wu, C.; Liu, X.
2017-12-01
Numerical weather models often struggle at representing clouds since small scale cloud processes must be parameterized. For example, models often utilize simple parameterizations for transitioning from liquid to ice, usually set as a function of temperature. However, supercooled liquid water (SLW) often persists at temperatures much lower than threshold values used in microphysics parameterizations. Previous observational studies of clouds over the Southern Ocean have found high frequencies of SLW (e.g., Morrison et al., 2011). Many of these studies have relied on satellite retrievals, which provide relatively low resolution observations and are often associated with large uncertainties due to assumptions of microphysical properties (e.g., particle size distributions). Recently, the NSF/NCAR O2/N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS) campaign took observations via the NSF/NCAR HIAPER research aircraft during January and February of 2016, providing in situ observations over the Southern Ocean (50°W to 92°W). We compare simulated results from the Weather Research and Forecasting (WRF) model with in situ observations from ORCAS. Differences between observations and simulations are evaluated via statistical analyses. Initial results from ORCAS reveal a high frequency of SLW at temperatures as low as -15°C, and the existence of SLW around -30°C. Recent studies have found that boundary layer clouds are underestimated by WRF in regions unaffected by cyclonic activity (Huang et al., 2014), suggesting a lack of low-level moisture due to local processes. To explore this, relative humidity distributions are examined and controlled by cloud microphysical characteristics (e.g., total water content) and relevant ambient properties (e.g., vertical velocity). A relatively low frequency of simulated SLW may in part explain the discrepancies in WRF, as cloud-top SLW results in stronger radiative cooling and turbulent motions conducive for long-lived cloud regimes
Photometric and polarimetric observations and model simulations of (216) Kleopatra
NASA Astrophysics Data System (ADS)
Takahashi, S.; Shinokawa, K.; Yoshida, F.; Mukai, T.; Ip, W. H.; Kawabata, K.
2004-10-01
We performed photometric and polarimetric observations, on November 8 and 9, 1999, of an M-type main belt asteroid, (216) Kleopatra by using the HBS spectropolarimeter installed at Dodaira observatory, National Astronomical Observatory of Japan (NAOJ). Photometric amplitude of lightcurve in the V band was 0.12 mag, and the averaged degree of polarization was -1.01±0.1%. It seems that the polarimetric data might also show a slight change in the degree of polarization ( ~0.2%) at the second minimum of the photometric lightcurve, but we could not confirm that the feature was real because of the large errors of data. With the assumption that the surface is uniform, we have carried out lightcurve simulations based on shape models by Ostro et al. (2000), Tanga et al. (2001) and Roche binary (Cellino et al., 1985). The results of simulations were compared to the configurations of lightcurves which had been obtained at different 4 geometric positions (1980, 1982, 1987 and 1999). The model by Cellino et al. (1985) reproduced almost all the data points without the 1987 observations within ~0.05 mag., which is the best result among the 3 models. The model by Tanga et al. (2001) well reproduced the lightcurves, but failed in reproducing the 1982 amplitude (difference Δdiff ~ 0 2 mag.). We also confirmed that the model by Ostro et al. (2000) could not explain the observed lightcurves.
Observed and Simulated Supercell Demise Depicted by VORTEX2 Observations
NASA Astrophysics Data System (ADS)
Letkewicz, Casey Elizabeth
technique deemed base-state substitution (BSS) was developed to incorporate a varying base-state while maintaining a degree of experimental control. BSS was designed to test the impact of a new horizontally homogeneous base-state environment on storm morphology while maintaining storm-induced perturbations. The thermodynamic and kinematic environment can be independently altered, with modifications incorporated slowly (gradual BSS) or all at once (instant BSS). Trial simulations demonstrated that model stability was maintained and domain-integrated fields were well-behaved. The simulations of the 9 June 2009 supercell were designed to isolate the effects of the changing wind profile from those of the increasingly stable boundary layer. The observed environmental modifications, when gradually incorporated into the model via BSS, were able to reasonably reproduce the observed storm morphology. Overall, the experiments demonstrated that the demise of the supercell was ultimately the result of depleting the updraft's buoyancy. The increasingly stable low-level environment predominately contributed to demise; however, changes to the wind profile also acted to notably impact storm strength and morphology. Analysis of updraft parcels in each experiment demonstrated that the mean source region became elevated over time as the low-level environment stabilized and/or shear and helicity weakened. Consequently, updraft buoyancy was eventually depleted since the drier elevated parcels (with less instability) were more negatively impacted by entrainment. The diagnostic pressure equation was utilized to examine the evolution of vertical accelerations within the simulated storm updraft and explore how storm dynamics evolved as the environment evolved. It was found that changes to nonlinear dynamic acceleration primarily influenced the evolution in total vertical acceleration, though these changes were interconnected with shifts in buoyancy and updraft strength and rotation. The findings of
Tang, Guoping; Shafer, Sarah L.; Barlein, Patrick J.; Holman, Justin O.
2009-01-01
Prognostic vegetation models have been widely used to study the interactions between environmental change and biological systems. This study examines the sensitivity of vegetation model simulations to: (i) the selection of input climatologies representing different time periods and their associated atmospheric CO2 concentrations, (ii) the choice of observed vegetation data for evaluating the model results, and (iii) the methods used to compare simulated and observed vegetation. We use vegetation simulated for Asia by the equilibrium vegetation model BIOME4 as a typical example of vegetation model output. BIOME4 was run using 19 different climatologies and their associated atmospheric CO2 concentrations. The Kappa statistic, Fuzzy Kappa statistic and a newly developed map-comparison method, the Nomad index, were used to quantify the agreement between the biomes simulated under each scenario and the observed vegetation from three different global land- and tree-cover data sets: the global Potential Natural Vegetation data set (PNV), the Global Land Cover Characteristics data set (GLCC), and the Global Land Cover Facility data set (GLCF). The results indicate that the 30-year mean climatology (and its associated atmospheric CO2 concentration) for the time period immediately preceding the collection date of the observed vegetation data produce the most accurate vegetation simulations when compared with all three observed vegetation data sets. The study also indicates that the BIOME4-simulated vegetation for Asia more closely matches the PNV data than the other two observed vegetation data sets. Given the same observed data, the accuracy assessments of the BIOME4 simulations made using the Kappa, Fuzzy Kappa and Nomad index map-comparison methods agree well when the compared vegetation types consist of a large number of spatially continuous grid cells. The results of this analysis can assist model users in designing experimental protocols for simulating vegetation.
Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations
NASA Astrophysics Data System (ADS)
Nicolaou, Georgios; Yamauchi, Masatoshi; Nilsson, Hans; Wieser, Martin; Fedorov, Andrei
2017-04-01
Scientific requirements of each mission are crucial for the instrument's design. Ion tracing simulations of instruments can be helpful to characterize their performance, identify their limitations and improving the design for future missions. However, simulations provide the best performance in ideal case, and the actual response is determined by many other factors. Therefore, simulations should be compared with observations when possible. Characterizing the actual response of a running instrument gives valuable lessons for the future design of test instruments with the same detection principle before spending resources to build and calibrate them. In this study we use an ion tracing simulation of the Ion Composition Analyser (ICA) on board ROSETTA, in order to characterize its response and to compare it with the observations. It turned out that, due to the complicated unexpected response of the running instrument, the heavy cometary ions and molecules are sometimes difficult to be resolved. However, preliminary simulation of a slightly modified design predicts much higher mass resolution. Even after considering the complicated unexpected response, we safely expect that the modified design can resolve most abundant heavy atomic ions (e.g., O^+) and molecular ions (e.g., N_2+ and O_2^+). We show the simulation results for both designs and ICA data.
Comparisons Between TIME-GCM/MERRA Simulations and LEO Satellite Observations
NASA Astrophysics Data System (ADS)
Hagan, M. E.; Haeusler, K.; Forbes, J. M.; Zhang, X.; Doornbos, E.; Bruinsma, S.; Lu, G.
2014-12-01
We report on yearlong National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) simulations where we utilize the recently developed lower boundary condition based on 3-hourly MERRA (Modern-Era Retrospective Analysis for Research and Application) reanalysis data to account for tropospheric waves and tides propagating upward into the model domain. The solar and geomagnetic forcing is based on prevailing geophysical conditions. The simulations show a strong day-to-day variability in the upper thermospheric neutral temperature tidal fields, which is smoothed out quickly when averaging is applied over several days, e.g. up to 50% DE3 amplitude reduction for a 10-day average. This is an important result with respect to tidal diagnostics from satellite observations where averaging over multiple days is inevitable. In order to assess TIME-GCM performance we compare the simulations with measurements from the Gravity field and steady-state Ocean Circulation Explorer (GOCE), Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites.
Ice shelf basal melt rates around Antarctica from simulations and observations
NASA Astrophysics Data System (ADS)
Schodlok, M. P.; Menemenlis, D.; Rignot, E. J.
2016-02-01
We introduce an explicit representation of Antarctic ice shelf cavities in the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) ocean retrospective analysis; and compare resulting basal melt rates and patterns to independent estimates from satellite observations. Two simulations are carried out: the first is based on the original ECCO2 vertical discretization; the second has higher vertical resolution particularly at the depth range of ice shelf cavities. The original ECCO2 vertical discretization produces higher than observed melt rates and leads to a misrepresentation of Southern Ocean water mass properties and transports. In general, thicker levels at the base of the ice shelves lead to increased melting because of their larger heat capacity. This strengthens horizontal gradients and circulation within and outside the cavities and, in turn, warm water transports from the shelf break to the ice shelves. The simulation with more vertical levels produces basal melt rates (1735 ± 164 Gt/a) and patterns that are in better agreement with observations. Thinner levels in the sub-ice-shelf cavities improve the representation of a fresh/cold layer at the ice shelf base and of warm/salty water near the bottom, leading to a sharper pycnocline and reduced vertical mixing underneath the ice shelf. Improved water column properties lead to more accurate melt rates and patterns, especially for melt/freeze patterns under large cold-water ice shelves. At the 18 km grid spacing of the ECCO2 model configuration, the smaller, warm-water ice shelves cannot be properly represented, with higher than observed melt rates in both simulations.
Comparing cosmological hydrodynamic simulations with observations of high- redshift galaxy formation
NASA Astrophysics Data System (ADS)
Finlator, Kristian Markwart
We use cosmological hydrodynamic simulations to study the impact of outflows and radiative feedback on high-redshift galaxies. For outflows, we consider simulations that assume (i) no winds, (ii) a "constant-wind" model in which the mass-loading factor and outflow speed are constant, and (iii) "momentum-driven" winds in which both parameters vary smoothly with mass. In order to treat radiative feedback, we develop a moment-based radiative transfer technique that operates in both post-processing and coupled radiative hydrodynamic modes. We first ask how outflows impact the broadband spectral energy distributions (SEDs) of six observed reionization-epoch galaxies. Simulations reproduce five regardless of the outflow prescription, while the sixth suggests an unusually bursty star formation history. We conclude that (i) simulations broadly account for available constraints on reionization-epoch galaxies, (ii) individual SEDs do not constrain outflows, and (iii) SED comparisons efficiently isolate objects that challenge simulations. We next study how outflows impact the galaxy mass metallicity relation (MZR). Momentum-driven outflows uniquely reproduce observations at z = 2. In this scenario, galaxies obey two equilibria: (i) The rate at which a galaxy processes gas into stars and outflows tracks its inflow rate; and (ii) The gas enrichment rate owing to star formation balances the dilution rate owing to inflows. Combining these conditions indicates that the MZR is dominated by the (instantaneous) variation of outflows with mass, with more-massive galaxies driving less gas into outflows per unit stellar mass formed. Turning to radiative feedback, we use post-processing simulations to study the topology of reionization. Reionization begins in overdensities and then "leaks" directly into voids, with filaments reionizing last owing to their high density and low emissivity. This result conflicts with previous findings that voids ionize last. We argue that it owes to the
Trend Estimates of AERONET-Observed and Model-Simulated AOTs Between 1993 and 2013
NASA Technical Reports Server (NTRS)
Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, J.; Kim, M.; Lee, Y. G.; Koo, J.-H.; Lee, J.; Moon, K. J.
2015-01-01
Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope+/-2(sigma) = 0.75 +/- 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over
Sedimentary basin effects in Seattle, Washington: Ground-motion observations and 3D simulations
Frankel, Arthur; Stephenson, William; Carver, David
2009-01-01
Seismograms of local earthquakes recorded in Seattle exhibit surface waves in the Seattle basin and basin-edge focusing of S waves. Spectral ratios of Swaves and later arrivals at 1 Hz for stiff-soil sites in the Seattle basin show a dependence on the direction to the earthquake, with earthquakes to the south and southwest producing higher average amplification. Earthquakes to the southwest typically produce larger basin surface waves relative to S waves than earthquakes to the north and northwest, probably because of the velocity contrast across the Seattle fault along the southern margin of the Seattle basin. S to P conversions are observed for some events and are likely converted at the bottom of the Seattle basin. We model five earthquakes, including the M 6.8 Nisqually earthquake, using 3D finite-difference simulations accurate up to 1 Hz. The simulations reproduce the observed dependence of amplification on the direction to the earthquake. The simulations generally match the timing and character of basin surface waves observed for many events. The 3D simulation for the Nisqually earth-quake produces focusing of S waves along the southern margin of the Seattle basin near the area in west Seattle that experienced increased chimney damage from the earthquake, similar to the results of the higher-frequency 2D simulation reported by Stephenson et al. (2006). Waveforms from the 3D simulations show reasonable agreement with the data at low frequencies (0.2-0.4 Hz) for the Nisqually earthquake and an M 4.8 deep earthquake west of Seattle.
Results from a limited area mesoscale numerical simulation for 10 April 1979
NASA Technical Reports Server (NTRS)
Kalb, M. W.
1985-01-01
Results are presented from a nine-hour limited area fine mesh (35-km) mesoscale model simulation initialized with SESAME-AVE I radiosonde data for Apr. 10, 1979 at 2100 GMT. Emphasis is on the diagnosis of mesoscale structure in the mass and precipitation fields. Along the Texas/Oklahoma border, independent of the short wave, convective precipitation formed several hours into the simulation and was organized into a narrow band suggestive of the observed April 10 squall line.
Retrieved Products from Simulated Hyperspectral Observations of a Hurricane
NASA Technical Reports Server (NTRS)
Susskind, Joel; Kouvaris, Louis; Iredell, Lena; Blaisdell, John
2015-01-01
Demonstrate via Observing System Simulation Experiments (OSSEs) the potential utility of flying high spatial resolution AIRS class IR sounders on future LEO and GEO missions.The study simulates and analyzes radiances for 3 sounders with AIRS spectral and radiometric properties on different orbits with different spatial resolutions: 1) Control run 13 kilometers AIRS spatial resolution at nadir on LEO in Aqua orbit; 2) 2 kilometer spatial resolution LEO sounder at nadir ARIES; 3) 5 kilometers spatial resolution sounder on a GEO orbit, radiances simulated every 72 minutes.
NASA Astrophysics Data System (ADS)
Schumacher, R. S.; Peters, J. M.
2015-12-01
Mesoscale convective systems (MCSs) are responsible for a large fraction of warm-season extreme rainfall events over the continental United States, as well as other midlatitude regions globally. The rainfall production in these MCSs is determined by numerous factors, including the large-scale forcing for ascent, the organization of the convection, cloud microphysical processes, and the surrounding thermodynamic and kinematic environment. Furthermore, heavy-rain-producing MCSs are most common at night, which means that well-studied mechanisms for MCS maintenance and organization such as cold pools (gravity currents) are not always at work. In this study, we use numerical model simulations and recent field observations to investigate the sensitivity of low-level MCS structures, and their influences on rainfall, to the details of the thermodynamic environment. In particular, small alterations to the initial conditions in idealized and semi-idealized simulations result in comparatively large precipitation changes, both in terms of the intensity and the spatial distribution. The uncertainties in the thermodynamic enviroments in the model simulations will be compared with high-resolution observations from the Plains Elevated Convection At Night (PECAN) field experiment in 2015. The results have implications for the paradigms of "surface-based" versus "elevated" convection, as well as for the predictability of warm-season convective rainfall.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ry, Rexha Verdhora, E-mail: rexha.vry@gmail.com; Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id
Observation of earthquakes is routinely used widely in tectonic activity observation, and also in local scale such as volcano tectonic and geothermal activity observation. It is necessary for determining the location of precise hypocenter which the process involves finding a hypocenter location that has minimum error between the observed and the calculated travel times. When solving this nonlinear inverse problem, simulated annealing inversion method can be applied to such global optimization problems, which the convergence of its solution is independent of the initial model. In this study, we developed own program codeby applying adaptive simulated annealing inversion in Matlab environment.more » We applied this method to determine earthquake hypocenter using several data cases which are regional tectonic, volcano tectonic, and geothermal field. The travel times were calculated using ray tracing shooting method. We then compared its results with the results using Geiger’s method to analyze its reliability. Our results show hypocenter location has smaller RMS error compared to the Geiger’s result that can be statistically associated with better solution. The hypocenter of earthquakes also well correlated with geological structure in the study area. Werecommend using adaptive simulated annealing inversion to relocate hypocenter location in purpose to get precise and accurate earthquake location.« less
Observations and simulations of the western United States' hydroclimate
NASA Astrophysics Data System (ADS)
Guirguis, Kristen
While very important from an economical and societal point of view, estimating precipitation in the western United States remains an unsolved and challenging problem. This is due to difficulties in observing and modeling precipitation in complex terrain. This research examines this issue by (i) providing a systematic evaluation of precipitation observations to quantify data uncertainty; and (ii) investigating the ability of the Ocean-Land-Atmosphere Model (OLAM) to simulate the winter hydroclimate in this region. This state-of-the-art, non-hydrostatic model has the capability of simulating simultaneously all scales of motions at various resolutions. This research intercompares nine precipitation datasets commonly used in hydrometeorological research in two ways. First, using principal component analysis, a precipitation climatology is conducted for the western U.S. from which five unique precipitation climates are identified. From this analysis, data uncertainty is shown to be primarily due to differences in (i) precipitation over the Rocky Mountains, (ii) the eastward wet-to-dry precipitation gradient during the cold season, (iii) the North American Monsoon signal, and (iv) precipitation in the desert southwest during spring and summer. The second intercomparison uses these five precipitation regions to provide location-specific assessments of uncertainty, which is shown to be dependent on season, location. Long-range weather forecasts on the order of a season are important for water-scarce regions such as the western U.S. The modeling component of this research looks at the ability of the OLAM to simulate the hydroclimate in the western U.S. during the winter of 1999. Six global simulations are run, each with a different spatial resolution over the western U.S. (360 km down to 11 km). For this study, OLAM is configured as for a long-range seasonal hindcast but with observed sea surface temperatures. OLAM precipitation compares well against observations, and is
DKIST Adaptive Optics System: Simulation Results
NASA Astrophysics Data System (ADS)
Marino, Jose; Schmidt, Dirk
2016-05-01
The 4 m class Daniel K. Inouye Solar Telescope (DKIST), currently under construction, will be equipped with an ultra high order solar adaptive optics (AO) system. The requirements and capabilities of such a solar AO system are beyond those of any other solar AO system currently in operation. We must rely on solar AO simulations to estimate and quantify its performance.We present performance estimation results of the DKIST AO system obtained with a new solar AO simulation tool. This simulation tool is a flexible and fast end-to-end solar AO simulator which produces accurate solar AO simulations while taking advantage of current multi-core computer technology. It relies on full imaging simulations of the extended field Shack-Hartmann wavefront sensor (WFS), which directly includes important secondary effects such as field dependent distortions and varying contrast of the WFS sub-aperture images.
Comparison of the analytical and simulation results of the equilibrium beam profile
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Z. J.; Zhu Shaoping; Cao, L. H.
2007-10-15
The evolution of high current electron beams in dense plasmas has been investigated by using two-dimensional particle-in-cell (PIC) simulations with immobile ions. It is shown that electron beams are split into many filaments at the beginning due to the Weibel instability, and then different filamentation beams attract each other and coalesce. The profile of the filaments can be described by formulas. Hammer et al. [Phys. Fluids 13, 1831 (1970)] developed a self-consistent relativistic electron beam model that allows the propagation of relativistic electron fluxes in excess of the Alfven-Lawson critical-current limit for a fully neutralized beam. The equilibrium solution hasmore » been observed in the simulation results, but the electron distribution function assumed by Hammer et al. is different from the simulation results.« less
Modelling dust polarization observations of molecular clouds through MHD simulations
NASA Astrophysics Data System (ADS)
King, Patrick K.; Fissel, Laura M.; Chen, Che-Yu; Li, Zhi-Yun
2018-03-01
The BLASTPol observations of Vela C have provided the most detailed characterization of the polarization fraction p and dispersion in polarization angles S for a molecular cloud. We compare the observed distributions of p and S with those obtained in synthetic observations of simulations of molecular clouds, assuming homogeneous grain alignment. We find that the orientation of the mean magnetic field relative to the observer has a significant effect on the p and S distributions. These distributions for Vela C are most consistent with synthetic observations where the mean magnetic field is close to the line of sight. Our results point to apparent magnetic disorder in the Vela C molecular cloud, although it can be due to either an inclination effect (i.e. observing close to the mean field direction) or significant field tangling from strong turbulence/low magnetization. The joint correlations of p with column density and of S with column density for the synthetic observations generally agree poorly with the Vela C joint correlations, suggesting that understanding these correlations requires a more sophisticated treatment of grain alignment physics.
NASA Astrophysics Data System (ADS)
van Eerten, Hendrik J.; MacFadyen, Andrew I.
2012-06-01
We discuss jet dynamics for narrow and wide gamma-ray burst (GRB) afterglow jets and the observational implications of numerical simulations of relativistic jets in two dimensions. We confirm earlier numerical results that sideways expansion of relativistic jets during the bulk of the afterglow emission phase is logarithmic in time and find that this also applies to narrow jets with half opening angle of 0.05 rad. As a result, afterglow jets remain highly nonspherical until after they have become nonrelativistic. Although sideways expansion steepens the afterglow light curve after the jet break, the jet edges becoming visible dominates the jet break, which means that the jet break is sensitive to the observer angle even for narrow jets. Failure to take the observer angle into account can lead to an overestimation of the jet energy by up to a factor of four. This weakens the challenge posed to the magneter energy limit by extreme events such as GRB090926A. Late-time radio calorimetry based on a spherical nonrelativistic outflow model remains relevant when the observer is approximately on-axis and where differences of a few in flux level between the model and the simulation are acceptable. However, this does not imply sphericity of the outflow and therefore does not translate to high observer angles relevant to orphan afterglows. For more accurate calorimetry and in order to model significant late-time features such as the rise of the counterjet, detailed jet simulations remain indispensable.
NASA Astrophysics Data System (ADS)
Yudin, V. A.; England, S.; Matsuo, T.; Wang, H.; Immel, T. J.; Eastes, R.; Akmaev, R. A.; Goncharenko, L. P.; Fuller-Rowell, T. J.; Liu, H.; Solomon, S. C.; Wu, Q.
2014-12-01
We review and discuss the capability of novel configurations of global community (WACCM-X and TIME-GCM) and planned-operational (WAM) models to support current and forthcoming space-borne missions to monitor the dynamics and composition of the Ionosphere-Thermosphere-Mesosphere (ITM) system. In the specified meteorology model configuration of WACCM-X, the lower atmosphere is constrained by operational analyses and/or short-term forecasts provided by the Goddard Earth Observing System (GEOS-5) of GMAO/NASA/GSFC. With the terrestrial weather of GEOS-5 and updated model physics, WACCM-X simulations are capable to reproduce the observed signatures of the perturbed wave dynamics and ion-neutral coupling during recent (2006-2013) stratospheric warming events, short-term, annual and year-to-year variability of prevailing flows, planetary waves, tides, and composition. With assimilation of the NWP data in the troposphere and stratosphere the planned-operational configuration of WAM can also recreate the observed features of the ITM day-to-day variability. These "terrestrial-weather" driven whole atmosphere simulations, with day-to-day variable solar and geomagnetic inputs, can provide specification of the background state (first guess) and errors for the inverse algorithms of forthcoming NASA ITM missions, such as ICON and GOLD. With two different viewing geometries (sun-synchronous, for ICON and geostationary for GOLD) these missions promise to perform complimentary global observations of temperature, winds and constituents to constrain the first-principle space weather forecast models. The paper will discuss initial designs of Observing System Simulation Experiments (OSSE) in the coupled simulations of TIME-GCM/WACCM-X/GEOS5 and WAM/GIP. As recognized, OSSE represent an excellent learning tool for designing and evaluating observing capabilities of novel sensors. The choice of assimilation schemes, forecast and observational errors will be discussed along with challenges
Multiwavelength mock observations of the WHIM in a simulated galaxy cluster
NASA Astrophysics Data System (ADS)
Planelles, Susana; Mimica, Petar; Quilis, Vicent; Cuesta-Martínez, Carlos
2018-06-01
About half of the expected total baryon budget in the local Universe is `missing'. Hydrodynamical simulations suggest that most of the missing baryons are located in a mildly overdense, warm-hot intergalactic medium (WHIM), which is difficult to be detected at most wavelengths. In this paper, we explore multiwavelength synthetic observations of a massive galaxy cluster developed in a full Eulerian-adaptive mesh refinement cosmological simulation. A novel numerical procedure is applied on the outputs of the simulation, which are post-processed with a full-radiative transfer code that can compute the change of the intensity at any frequency along the null geodesic of photons. We compare the emission from the whole intergalactic medium and from the WHIM component (defined as the gas with a temperature in the range 105-107 K) at three observational bands associated with thermal X-rays, thermal and kinematic Sunyaev-Zel'dovich effect, and radio emission. The synthetic maps produced by this procedure could be directly compared with existing observational maps and could be used as a guide for future observations with forthcoming instruments. The analysis of the different emissions associated with a high-resolution galaxy cluster is in broad agreement with previous simulated and observational estimates of both gas components.
NASA Astrophysics Data System (ADS)
Dalsøren, Stig B.; Myhre, Gunnar; Hodnebrog, Øivind; Myhre, Cathrine Lund; Stohl, Andreas; Pisso, Ignacio; Schwietzke, Stefan; Höglund-Isaksson, Lena; Helmig, Detlev; Reimann, Stefan; Sauvage, Stéphane; Schmidbauer, Norbert; Read, Katie A.; Carpenter, Lucy J.; Lewis, Alastair C.; Punjabi, Shalini; Wallasch, Markus
2018-03-01
Ethane and propane are the most abundant non-methane hydrocarbons in the atmosphere. However, their emissions, atmospheric distribution, and trends in their atmospheric concentrations are insufficiently understood. Atmospheric model simulations using standard community emission inventories do not reproduce available measurements in the Northern Hemisphere. Here, we show that observations of pre-industrial and present-day ethane and propane can be reproduced in simulations with a detailed atmospheric chemistry transport model, provided that natural geologic emissions are taken into account and anthropogenic fossil fuel emissions are assumed to be two to three times higher than is indicated in current inventories. Accounting for these enhanced ethane and propane emissions results in simulated surface ozone concentrations that are 5-13% higher than previously assumed in some polluted regions in Asia. The improved correspondence with observed ethane and propane in model simulations with greater emissions suggests that the level of fossil (geologic + fossil fuel) methane emissions in current inventories may need re-evaluation.
Numerical simulation of granular flows : comparison with experimental results
NASA Astrophysics Data System (ADS)
Pirulli, M.; Mangeney-Castelnau, A.; Lajeunesse, E.; Vilotte, J.-P.; Bouchut, F.; Bristeau, M. O.; Perthame, B.
2003-04-01
Granular avalanches such as rock or debris flows regularly cause large amounts of human and material damages. Numerical simulation of granular avalanches should provide a useful tool for investigating, within realistic geological contexts, the dynamics of these flows and of their arrest phase and for improving the risk assessment of such natural hazards. Validation of debris avalanche numerical model on granular experiments over inclined plane is performed here. The comparison is performed by simulating granular flow of glass beads from a reservoir through a gate down an inclined plane. This unsteady situation evolves toward the steady state observed in the laboratory. Furthermore simulation exactly reproduces the arrest phase obtained by suddenly closing the gate of the reservoir once a thick flow has developped. The spreading of a granular mass released from rest at the top of a rough inclined plane is also investigated. The evolution of the avalanche shape, the velocity and the characteristics of the arrest phase are compared with experimental results and analysis of the involved forces are studied for various flow laws.
Understanding Southern Ocean SST Trends in Historical Simulations and Observations
NASA Astrophysics Data System (ADS)
Kostov, Yavor; Ferreira, David; Marshall, John; Armour, Kyle
2017-04-01
Historical simulations with CMIP5 global climate models do not reproduce the observed 1979-2014 Southern Ocean (SO) cooling, and most ensemble members predict gradual warming around Antarctica. In order to understand this discrepancy and the mechanisms behind the SO cooling, we analyze output from 19 CMIP5 models. For each ensemble member we estimate the characteristic responses of SO SST to step changes in greenhouse gas (GHG) forcing and in the seasonal indices of the Southern Annular Mode (SAM). Using these step-response functions and linear convolution theory, we reconstruct the original CMIP5 simulations of 1979-2014 SO SST trends. We recover the CMIP5 ensemble mean trend, capture the intermodel spread, and reproduce very well the behavior of individual models. We thus suggest that GHG forcing and the SAM are major drivers of the simulated 1979-2014 SO SST trends. In consistence with the seasonal signature of the Antarctic ozone hole, our results imply that the summer (DJF) and fall (MAM) SAM exert a particularly important effect on the SO SST. In some CMIP5 models the SO SST response to SAM partially counteracts the warming due to GHG forcing, while in other ensemble members the SAM-induced SO SST trends complement the warming effect of GHG forcing. The compensation between GHG and SAM-induced SO SST anomalies is model-dependent and is determined by multiple factors. Firstly, CMIP5 models have different characteristic SST step response functions to SAM. Kostov et al. (2016) relate these differences to biases in the models' climatological SO temperature gradients. Secondly, many CMIP5 historical simulations underestimate the observed positive trends in the DJF and MAM seasonal SAM indices. We show that this affects the models' ability to reproduce the observed SO cooling. Last but not least, CMIP5 models differ in their SO SST step response functions to GHG forcing. Understanding the diverse behavior of CMIP5 models helps shed light on the physical processes
Panchromatic spectral energy distributions of simulated galaxies: results at redshift z = 0
NASA Astrophysics Data System (ADS)
Goz, David; Monaco, Pierluigi; Granato, Gian Luigi; Murante, Giuseppe; Domínguez-Tenreiro, Rosa; Obreja, Aura; Annunziatella, Marianna; Tescari, Edoardo
2017-08-01
We present predictions of spectral energy distributions (SEDs), from the UV to the FIR, of simulated galaxies at z = 0. These were obtained by post-processing the results of an N-body+hydro simulation of a cosmological box of side 25 Mpc, which uses the Multi-Phase Particle Integrator (MUPPI) for star formation and stellar feedback, with the grasil-3d radiative transfer code that includes reprocessing of UV light by dust. Physical properties of our sample of ˜500 galaxies resemble observed ones, though with some tension at small and large stellar masses. Comparing predicted SEDs of simulated galaxies with different samples of local galaxies, we find that these resemble observed ones, when normalized at 3.6 μm. A comparison with the Herschel Reference Survey shows that the average SEDs of galaxies, divided in bins of star formation rate (SFR), are reproduced in shape and absolute normalization to within a factor of ˜2, while average SEDs of galaxies divided in bins of stellar mass show tensions that are an effect of the difference of simulated and observed galaxies in the stellar mass-SFR plane. We use our sample to investigate the correlation of IR luminosity in Spitzer and Herschel bands with several galaxy properties. SFR is the quantity that best correlates with IR light up to 160 μm, while at longer wavelengths better correlations are found with molecular mass and, at 500 μm, with dust mass. However, using the position of the FIR peak as a proxy for cold dust temperature, we assess that heating of cold dust is mostly determined by SFR, with stellar mass giving only a minor contribution. We finally show how our sample of simulated galaxies can be used as a guide to understand the physical properties and selection biases of observed samples.
NASA Technical Reports Server (NTRS)
Ackerman, A. S.; Stevens, D. E.; Toon, O. B.; Coakley, J. A., Jr.; Gore, Warren J. (Technical Monitor)
2002-01-01
A number of observations and simulations have shown that increased droplet concentrations in ship tracks increase their total cross-sectional area, thereby enhancing cloud albedo and providing a negative (cooling) radiative forcing at the surface and the top of the atmosphere. In some cases cloud water has been found to be enhanced in ship tracks, which has been attributed to suppression of drizzle and implies an enhanced susceptibility of cloud albedo to droplet concentrations. However, observations from aircraft and satellite indicate that on average cloud water is instead reduced in daytime ship tracks. Such a reduction in liquid water may be attributable to cloud-burning caused by solar heating by soot within the ship exhaust, or by increased precipitation resulting from giant nuclei in the ship exhaust. We will summarize the observational evidence and present results from large-eddy simulations that evaluate these mechanisms. Along the way we will present our insights into the interpretation of satellite retrievals of cloud microphysical properties.
ON THE OBSERVATION AND SIMULATION OF SOLAR CORONAL TWIN JETS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Jiajia; Wang, Yuming; Zhang, Quanhao
We present the first observation, analysis, and modeling of solar coronal twin jets, which occurred after a preceding jet. Detailed analysis on the kinetics of the preceding jet reveals its blowout-jet nature, which resembles the one studied in Liu et al. However, the erupting process and kinetics of the twin jets appear to be different from the preceding one. Lacking detailed information on the magnetic fields in the twin jet region, we instead use a numerical simulation using a three-dimensional (3D) MHD model as described in Fang et al., and find that in the simulation a pair of twin jetsmore » form due to reconnection between the ambient open fields and a highly twisted sigmoidal magnetic flux, which is the outcome of the further evolution of the magnetic fields following the preceding blowout jet. Based on the similarity between the synthesized and observed emission, we propose this mechanism as a possible explanation for the observed twin jets. Combining our observation and simulation, we suggest that with continuous energy transport from the subsurface convection zone into the corona, solar coronal twin jets could be generated in the same fashion addressed above.« less
Cuerva, Marcos J; Piñel, Carlos S; Martin, Lourdes; Espinosa, Jose A; Corral, Octavio J; Mendoza, Nicolás
2018-02-12
The design of optimal courses for obstetric undergraduate teaching is a relevant question. This study evaluates two different designs of simulator-based learning activity on childbirth with regard to respect to the patient, obstetric manoeuvres, interpretation of cardiotocography tracings (CTG) and infection prevention. This randomised experimental study which differs in the content of their briefing sessions consisted of two groups of undergraduate students, who performed two simulator-based learning activities on childbirth. The first briefing session included the observations of a properly performed scenario according to Spanish clinical practice guidelines on care in normal childbirth by the teachers whereas the second group did not include the observations of a properly performed scenario, and the students observed it only after the simulation process. The group that observed a properly performed scenario after the simulation obtained worse grades during the simulation, but better grades during the debriefing and evaluation. Simulator use in childbirth may be more fruitful when the medical students observe correct performance at the completion of the scenario compared to that at the start of the scenario. Impact statement What is already known on this subject? There is a scarcity of literature about the design of optimal high-fidelity simulation training in childbirth. It is known that preparing simulator-based learning activities is a complex process. Simulator-based learning includes the following steps: briefing, simulation, debriefing and evaluation. The most important part of high-fidelity simulations is the debriefing. A good briefing and simulation are of high relevance in order to have a fruitful debriefing session. What do the results of this study add? Our study describes a full simulator-based learning activity on childbirth that can be reproduced in similar facilities. The findings of this study add that high-fidelity simulation training in
Red-light running violation prediction using observational and simulator data.
Jahangiri, Arash; Rakha, Hesham; Dingus, Thomas A
2016-11-01
In the United States, 683 people were killed and an estimated 133,000 were injured in crashes due to running red lights in 2012. To help prevent/mitigate crashes caused by running red lights, these violations need to be identified before they occur, so both the road users (i.e., drivers, pedestrians, etc.) in potential danger and the infrastructure can be notified and actions can be taken accordingly. Two different data sets were used to assess the feasibility of developing red-light running (RLR) violation prediction models: (1) observational data and (2) driver simulator data. Both data sets included common factors, such as time to intersection (TTI), distance to intersection (DTI), and velocity at the onset of the yellow indication. However, the observational data set provided additional factors that the simulator data set did not, and vice versa. The observational data included vehicle information (e.g., speed, acceleration, etc.) for several different time frames. For each vehicle approaching an intersection in the observational data set, required data were extracted from several time frames as the vehicle drew closer to the intersection. However, since the observational data were inherently anonymous, driver factors such as age and gender were unavailable in the observational data set. Conversely, the simulator data set contained age and gender. In addition, the simulator data included a secondary (non-driving) task factor and a treatment factor (i.e., incoming/outgoing calls while driving). The simulator data only included vehicle information for certain time frames (e.g., yellow onset); the data did not provide vehicle information for several different time frames while vehicles were approaching an intersection. In this study, the random forest (RF) machine-learning technique was adopted to develop RLR violation prediction models. Factor importance was obtained for different models and different data sets to show how differently the factors influence the
NASA Astrophysics Data System (ADS)
Pucci, F.; Servidio, S.; Sorriso-Valvo, L.; Olshevsky, V.; Matthaeus, W. H.; Malara, F.; Goldman, M. V.; Newman, D. L.; Lapenta, G.
2017-05-01
The properties of the turbulence that develops in the outflows of magnetic reconnection have been investigated using self-consistent plasma simulations, in three dimensions. As commonly observed in space plasmas, magnetic reconnection is characterized by the presence of turbulence. Here we provide a direct comparison of our simulations with reported observations of reconnection events in the magnetotail, investigating the properties of the electromagnetic field and the energy conversion mechanisms. In particular, simulations show the development of a turbulent cascade consistent with spacecraft observations, statistics of the dissipation mechanisms in the turbulent outflows similar to the ones observed in reconnection jets in the magnetotail, and that the properties of turbulence vary as a function of the distance from the reconnecting X-line.
NASA Astrophysics Data System (ADS)
Pucci, Francesco; Servidio, Sergio; Sorriso-Valvo, Luca; Olshevsky, Vyacheslav; Matthaeus, William; Malara, Francesco; Goldman, Martin; Newman, David; Lapenta, Giovanni
2017-04-01
The properties of the turbulence which develops in the outflows of magnetic reconnection have been investigated using self-consistent plasma simulations, in three dimensions. As commonly observed in space plasmas, magnetic reconnection is characterized by the presence of turbulence. Here we provide a direct comparison of our simulations with observations of reconnection event in the magnetotail investigating the properties of the electromagnetic field and the energy conversion mechanisms. In particular, simulations show: the development of a turbulent cascade consistent with spacecraft observations, statistics of the the dissipation mechanisms in the turbulent outflows similar to the one observed in reconnection jets in the magnetotail, and that the properties of turbulence vary as a function of the distance from the reconnecting X-line.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pucci, F.; Olshevsky, V.; Lapenta, G.
2017-05-20
The properties of the turbulence that develops in the outflows of magnetic reconnection have been investigated using self-consistent plasma simulations, in three dimensions. As commonly observed in space plasmas, magnetic reconnection is characterized by the presence of turbulence. Here we provide a direct comparison of our simulations with reported observations of reconnection events in the magnetotail, investigating the properties of the electromagnetic field and the energy conversion mechanisms. In particular, simulations show the development of a turbulent cascade consistent with spacecraft observations, statistics of the dissipation mechanisms in the turbulent outflows similar to the ones observed in reconnection jets inmore » the magnetotail, and that the properties of turbulence vary as a function of the distance from the reconnecting X-line.« less
Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H I observations
NASA Astrophysics Data System (ADS)
El-Badry, Kareem; Bradford, Jeremy; Quataert, Eliot; Geha, Marla; Boylan-Kolchin, Michael; Weisz, Daniel R.; Wetzel, Andrew; Hopkins, Philip F.; Chan, T. K.; Fitts, Alex; Kereš, Dušan; Faucher-Giguère, Claude-André
2018-06-01
The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/σ and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations. We then quantify the shapes of 21-cm line profiles from a morphologically unbiased sample of ˜2000 low-redshift, H I-detected galaxies with Mstar = 107-11 M⊙ and compare to the simulated galaxies. At Mstar ≳ 1010 M⊙, both the observed and simulated galaxies produce double-horned profiles with low kurtosis and steep wings, consistent with rotationally supported discs. Both the observed and simulated line profiles become more Gaussian like (higher kurtosis and less-steep wings) at lower masses, indicating increased dispersion support. However, the simulated galaxies transition from rotational to dispersion support more strongly: at Mstar = 108-10 M⊙, most of the simulations produce more Gaussian-like profiles than typical observed galaxies with similar mass, indicating that gas in the low-mass simulated galaxies is, on average, overly dispersion supported. Most of the lower-mass-simulated galaxies also have somewhat lower gas fractions than the median of the observed population. The simulations nevertheless reproduce the observed line-width baryonic Tully-Fisher relation, which is insensitive to rotational versus dispersion support.
The Shock Dynamics of Heterogeneous YSO Jets: 3D Simulations Meet Multi-epoch Observations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hansen, E. C.; Frank, A.; Hartigan, P.
High-resolution observations of young stellar object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper, we report results of 3D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale dynamics by imposing velocity differences between spherical, over-dense regions, which then lead to the formation of bow shocks as faster clumps overtake slower material. We show that much of the spatial structure apparent in emission line images of jets arises from the dynamics and interactions of thesemore » bow shocks. Our simulations show a variety of time-dependent features, including bright knots associated with Mach stems where the shocks intersect, a “frothy” emission structure that arises from the presence of the Nonlinear Thin Shell Instability along the surfaces of the bow shocks, and the merging and fragmentation of clumps. Our simulations use a new non-equilibrium cooling method to produce synthetic emission maps in H α and [S ii]. These are directly compared to multi-epoch Hubble Space Telescope observations of Herbig–Haro jets. We find excellent agreement between features seen in the simulations and the observations in terms of both proper motion and morphologies. Thus we conclude that YSO jets may be dominated by heterogeneous structures and that interactions between these structures and the shocks they produce can account for many details of YSO jet evolution.« less
Simulations of VLBI observations of a geodetic satellite providing co-location in space
NASA Astrophysics Data System (ADS)
Anderson, James M.; Beyerle, Georg; Glaser, Susanne; Liu, Li; Männel, Benjamin; Nilsson, Tobias; Heinkelmann, Robert; Schuh, Harald
2018-02-01
We performed Monte Carlo simulations of very-long-baseline interferometry (VLBI) observations of Earth-orbiting satellites incorporating co-located space-geodetic instruments in order to study how well the VLBI frame and the spacecraft frame can be tied using such measurements. We simulated observations of spacecraft by VLBI observations, time-of-flight (TOF) measurements using a time-encoded signal in the spacecraft transmission, similar in concept to precise point positioning, and differential VLBI (D-VLBI) observations using angularly nearby quasar calibrators to compare their relative performance. We used the proposed European Geodetic Reference Antenna in Space (E-GRASP) mission as an initial test case for our software. We found that the standard VLBI technique is limited, in part, by the present lack of knowledge of the absolute offset of VLBI time to Coordinated Universal Time at the level of microseconds. TOF measurements are better able to overcome this problem and provide frame ties with uncertainties in translation and scale nearly a factor of three smaller than those yielded from VLBI measurements. If the absolute time offset issue can be resolved by external means, the VLBI results can be significantly improved and can come close to providing 1 mm accuracy in the frame tie parameters. D-VLBI observations with optimum performance assumptions provide roughly a factor of two higher uncertainties for the E-GRASP orbit. We additionally simulated how station and spacecraft position offsets affect the frame tie performance.
NASA Astrophysics Data System (ADS)
Sagawa, Hideo; Hartogh, Paul; Rengel, Miriam; de Lange, Arno; Cavalié, Thibault
2010-11-01
Observations of the water inventory as well as other chemically important species on Jupiter will be performed in the frame of the guaranteed time key project of the Herschel Space Observatory entitled "Water and related chemistry in the Solar system". Among other onboard instruments, PACS (Photodetector Array Camera and Spectrometer) will provide new data of the spectral atlas in a wide region covering the far-infrared and submillimetre domains, with an improved spectral resolution and a higher sensitivity compared to previous observations carried out by Cassini/CIRS (Composite InfraRed Spectrometer) and by ISO (Infrared Space Observatory). In order to optimise the observational plan and to prepare for the data analysis, we have simulated the expected spectra of PACS Jupiter observations. Our simulation shows that PACS will promisingly detect several H 2O emission lines. As PACS is capable of spatially resolving the Jovian disk, we will be able to discern the external oxygen sources in the giant planets by exploring the horizontal distribution of water. In addition to H 2O lines, some absorption lines due to tropospheric CH 4, HD, PH 3 and NH 3 lines will be observed with PACS. Furthermore, owing to the high sensitivity of the instrument, the current upper limit on the abundance of hydrogen halides such as HCl will be also improved.
Revisiting the stellar velocity ellipsoid-Hubble-type relation: observations versus simulations
NASA Astrophysics Data System (ADS)
Pinna, F.; Falcón-Barroso, J.; Martig, M.; Martínez-Valpuesta, I.; Méndez-Abreu, J.; van de Ven, G.; Leaman, R.; Lyubenova, M.
2018-04-01
The stellar velocity ellipsoid (SVE) in galaxies can provide important information on the processes that participate in the dynamical heating of their disc components (e.g. giant molecular clouds, mergers, spiral density waves, and bars). Earlier findings suggested a strong relation between the shape of the disc SVE and Hubble type, with later-type galaxies displaying more anisotropic ellipsoids and early types being more isotropic. In this paper, we revisit the strength of this relation using an exhaustive compilation of observational results from the literature on this issue. We find no clear correlation between the shape of the disc SVE and morphological type, and show that galaxies with the same Hubble type display a wide range of vertical-to-radial velocity dispersion ratios. The points are distributed around a mean value and scatter of σz/σR = 0.7 ± 0.2. With the aid of numerical simulations, we argue that different mechanisms might influence the shape of the SVE in the same manner and that the same process (e.g. mergers) does not have the same impact in all the galaxies. The complexity of the observational picture is confirmed by these simulations, which suggest that the vertical-to-radial axis ratio of the SVE is not a good indicator of the main source of disc heating. Our analysis of those simulations also indicates that the observed shape of the disc SVE may be affected by several processes simultaneously and that the signatures of some of them (e.g. mergers) fade over time.
Muhlbauer, A.; Ackerman, T. P.; Lawson, R. P.; ...
2015-07-14
Cirrus clouds are ubiquitous in the upper troposphere and still constitute one of the largest uncertainties in climate predictions. Our paper evaluates cloud-resolving model (CRM) and cloud system-resolving model (CSRM) simulations of a midlatitude cirrus case with comprehensive observations collected under the auspices of the Atmospheric Radiation Measurements (ARM) program and with spaceborne observations from the National Aeronautics and Space Administration A-train satellites. The CRM simulations are driven with periodic boundary conditions and ARM forcing data, whereas the CSRM simulations are driven by the ERA-Interim product. Vertical profiles of temperature, relative humidity, and wind speeds are reasonably well simulated bymore » the CSRM and CRM, but there are remaining biases in the temperature, wind speeds, and relative humidity, which can be mitigated through nudging the model simulations toward the observed radiosonde profiles. Simulated vertical velocities are underestimated in all simulations except in the CRM simulations with grid spacings of 500 m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in general circulation models and in CSRM simulations with horizontal grid spacings on the order of 1 km. The simulated ice water content and ice number concentrations agree with the observations in the CSRM but are underestimated in the CRM simulations. The underestimation of ice number concentrations is consistent with the overestimation of radar reflectivity in the CRM simulations and suggests that the model produces too many large ice particles especially toward the cloud base. Simulated cloud profiles are rather insensitive to perturbations in the initial conditions or the dimensionality of the model domain, but the treatment of the forcing data has a considerable effect on the outcome of the model simulations. Despite considerable progress in observations and microphysical parameterizations
Simulating CO2 profiles using NIES TM and comparison with HIAPER Pole-to-Pole Observations
NASA Astrophysics Data System (ADS)
Song, C.; Maksyutov, S.; Belikov, D.; Takagi, H.; Shu, J.
2015-03-01
We present a study on validation of the National Institute for Environmental Studies Transport Model (NIES TM) by comparing to observed vertical profiles of atmospheric CO2. The model uses a hybrid sigma-isentropic (σ-θ) vertical coordinate that employs both terrain-following and isentropic parts switched smoothly in the stratosphere. The model transport is driven by reanalyzed meteorological fields and designed to simulate seasonal and diurnal cycles, synoptic variations, and spatial distributions of atmospheric chemical constituents in the troposphere. The model simulations were run for biosphere, fossil fuel, air-ocean exchange, biomass burning and inverse correction fluxes of carbon dioxide (CO2) by GOSAT Level 4 product. We compared the NIES TM simulated fluxes with data from the HIAPER Pole-to-Pole Observations (HIPPO) Merged 10 s Meteorology, Atmospheric Chemistry, and Aerosol Data, including HIPPO-1, HIPPO-2 and HIPPO-3 from 128.0° E to -84.0° W, and 87.0° N to -67.2° S. The simulation results were compared with CO2 observations made in January and November 2009, and March and April 2010. The analysis attests that the model is good enough to simulate vertical profiles with errors generally within 1-2 ppmv, except for the lower stratosphere in the Northern Hemisphere high latitudes.
Simulating flaring events in complex active regions driven by observed magnetograms
NASA Astrophysics Data System (ADS)
Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.
2011-05-01
Context. We interpret solar flares as events originating in active regions that have reached the self organized critical state, by using a refined cellular automaton model with initial conditions derived from observations. Aims: We investigate whether the system, with its imposed physical elements, reaches a self organized critical state and whether well-known statistical properties of flares, such as scaling laws observed in the distribution functions of characteristic parameters, are reproduced after this state has been reached. Methods: To investigate whether the distribution functions of total energy, peak energy and event duration follow the expected scaling laws, we first applied a nonlinear force-free extrapolation that reconstructs the three-dimensional magnetic fields from two-dimensional vector magnetograms. We then locate magnetic discontinuities exceeding a threshold in the Laplacian of the magnetic field. These discontinuities are relaxed in local diffusion events, implemented in the form of cellular automaton evolution rules. Subsequent loading and relaxation steps lead the system to self organized criticality, after which the statistical properties of the simulated events are examined. Physical requirements, such as the divergence-free condition for the magnetic field vector, are approximately imposed on all elements of the model. Results: Our results show that self organized criticality is indeed reached when applying specific loading and relaxation rules. Power-law indices obtained from the distribution functions of the modeled flaring events are in good agreement with observations. Single power laws (peak and total flare energy) are obtained, as are power laws with exponential cutoff and double power laws (flare duration). The results are also compared with observational X-ray data from the GOES satellite for our active-region sample. Conclusions: We conclude that well-known statistical properties of flares are reproduced after the system has
Realistic Simulations of Coronagraphic Observations with Future Space Telescopes
NASA Astrophysics Data System (ADS)
Rizzo, M. J.; Roberge, A.; Lincowski, A. P.; Zimmerman, N. T.; Juanola-Parramon, R.; Pueyo, L.; Hu, M.; Harness, A.
2017-11-01
We present a framework to simulate realistic observations of future space-based coronagraphic instruments. This gathers state-of-the-art scientific and instrumental expertise allowing robust characterization of future instrument concepts.
The power spectrum of solar convection flows from high-resolution observations and 3D simulations
NASA Astrophysics Data System (ADS)
Yelles Chaouche, L.; Moreno-Insertis, F.; Bonet, J. A.
2014-03-01
instead of on horizontal planes. Results: A very good match between observational and simulated Fourier power spectra is obtained for the vertical velocity data for scales between 200 km and 6 Mm. Instead, a clear vertical shift is obtained when the synthetic observations are not degraded to emulate the degradation in the IMaX data. The match for the horizontal velocity data is much less impressive because of the inaccuracies of the LCT procedure. Concerning the internal comparison of the direct velocity values of the numerical boxes with those from the synthetic observations, a high correlation (0.96) is obtained for the vertical component when using the velocity values on the log τ500 = -1 surface in the box. The corresponding Fourier spectra are near each other. A lower maximum correlation (0.5) is reached (at log τ500 = 0) for the horizontal velocities as a result of the coarseness of the LCT procedure. Correspondingly, the Fourier spectra for the LCT-determined velocities is well below that from the actual velocity components. Conclusions: As measured by the Fourier spectra, realistic numerical simulations of surface magnetoconvection provide a very good match to the observational proxies for the photospheric velocity fields at least on scales from several Mm down to around 200 km. Taking into account the spatial and spectral instrumental blurring is essential for the comparison between simulations and observations. Dopplergrams are an excellent proxy for the vertical velocities on constant-τ isosurfaces, while LCT is a much less reliable method of determining the horizontal velocities.
Volcanic observation data and simulation database at NIED, Japan (Invited)
NASA Astrophysics Data System (ADS)
Fujita, E.; Ueda, H.; Kozono, T.
2009-12-01
NIED (Nat’l Res. Inst. for Earth Sci. & Disast. Prev.) has a project to develop two volcanic database systems: (1) volcanic observation database; (2) volcanic simulation database. The volcanic observation database is the data archive center obtained by the geophysical observation networks at Mt. Fuji, Miyake, Izu-Oshima, Iwo-jima and Nasu volcanoes, central Japan. The data consist of seismic (both high-sensitivity and broadband), ground deformation (tiltmeter, GPS) and those from other sensors (e.g., rain gauge, gravimeter, magnetometer, pressure gauge.) These data is originally stored in “WIN format,” the Japanese standard format, which is also at the Hi-net (High sensitivity seismic network Japan, http://www.hinet.bosai.go.jp/). NIED joins to WOVOdat and we have prepared to upload our data, via XML format. Our concept of the XML format is 1)a common format for intermediate files to upload into the WOVOdat DB, 2) for data files downloaded from the WOVOdat DB, 3) for data exchanges between observatories without the WOVOdat DB, 4) for common data files in each observatory, 5) for data communications between systems and softwares and 6)a for softwares. NIED is now preparing for (2) the volcanic simulation database. The objective of this project is to support to develop a “real-time” hazard map, i.e., the system which is effective to evaluate volcanic hazard in case of emergency, including the up-to-date conditions. Our system will include lava flow simulation (LavaSIM) and pyroclastic flow simulation (grvcrt). The database will keep many cases of assumed simulations and we can pick up the most probable case as the first evaluation in case the eruption started. The final goals of the both database will realize the volcanic eruption prediction and forecasting in real time by the combination of monitoring data and numerical simulations.
Thermal airborne multispectral aster simulator and its preliminary results
NASA Astrophysics Data System (ADS)
Mills, F.; Kannari, Y.; Watanabe, H.; Sano, M.; Chang, S. H.
1994-03-01
An Airborne ASTER Simulator (AAS) is being developed for the Japan Resources Observation System Organization (JAROS) by the Geophysical Environmental Research (GER) Corporation. The first test flights of the AAS were over Cuprite, Nevada; Long Valley, California; and Death Valley, California, in December 1991. Preliminary laboratory tests at NASA's Stennis Space Center (SSC) were completed in April 1992. The results of the these tests indicate the AAS can discriminate between silicate and non-silicate rocks. The improvements planned for the next two years may give a spectral Full-Width at Half-Maximum (FWHM) of 0.3 μm and NEΔT of 0.2 - 0.5°K. The AAS has the potential to become a good tool for airborne TIR research and can be used for simulations of future satellite-borne TIR sensors. Flight tests over Cuprite, Nevada, and Castaic Lake, California, are planned for October-December 1992.
Evaluation of Global Observations-Based Evapotranspiration Datasets and IPCC AR4 Simulations
NASA Technical Reports Server (NTRS)
Mueller, B.; Seneviratne, S. I.; Jimenez, C.; Corti, T.; Hirschi, M.; Balsamo, G.; Ciais, P.; Dirmeyer, P.; Fisher, J. B.; Guo, Z.;
2011-01-01
Quantification of global land evapotranspiration (ET) has long been associated with large uncertainties due to the lack of reference observations. Several recently developed products now provide the capacity to estimate ET at global scales. These products, partly based on observational data, include satellite ]based products, land surface model (LSM) simulations, atmospheric reanalysis output, estimates based on empirical upscaling of eddycovariance flux measurements, and atmospheric water balance datasets. The LandFlux-EVAL project aims to evaluate and compare these newly developed datasets. Additionally, an evaluation of IPCC AR4 global climate model (GCM) simulations is presented, providing an assessment of their capacity to reproduce flux behavior relative to the observations ]based products. Though differently constrained with observations, the analyzed reference datasets display similar large-scale ET patterns. ET from the IPCC AR4 simulations was significantly smaller than that from the other products for India (up to 1 mm/d) and parts of eastern South America, and larger in the western USA, Australia and China. The inter-product variance is lower across the IPCC AR4 simulations than across the reference datasets in several regions, which indicates that uncertainties may be underestimated in the IPCC AR4 models due to shared biases of these simulations.
Leistedt, B.; Peiris, H. V.; Elsner, F.; ...
2016-10-17
Spatially-varying depth and characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey analyses, in particular in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. Wemore » illustrate the complementarity of these two approaches by comparing the SV data with the BCC-UFig, a synthetic sky catalogue generated by forward-modelling of the DES SV images. We then analyse the BCC-UFig simulation to construct galaxy samples mimicking those used in SV galaxy clustering studies. We show that the spatially-varying survey depth imprinted in the observed galaxy densities and the redshift distributions of the SV data are successfully reproduced by the simulation and well-captured by the maps of observing conditions. The combined use of the maps, the SV data and the BCC-UFig simulation allows us to quantify the impact of spatial systematics on N(z), the redshift distributions inferred using photometric redshifts. We conclude that spatial systematics in the SV data are mainly due to seeing fluctuations and are under control in current clustering and weak lensing analyses. However, they will need to be carefully characterised in upcoming phases of DES in order to avoid biasing the inferred cosmological results. The framework presented is relevant to all multi-epoch surveys, and will be essential for exploiting future surveys such as the Large Synoptic Survey Telescope, which will require detailed null-tests and realistic end-to-end image simulations to correctly interpret the deep, high
DOE Office of Scientific and Technical Information (OSTI.GOV)
Leistedt, B.; Peiris, H. V.; Elsner, F.
Spatially varying depth and the characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey analyses, particularly in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES-SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. Wemore » illustrate the complementary nature of these two approaches by comparing the SV data with BCC-UFig, a synthetic sky catalog generated by forward-modeling of the DES-SV images. We analyze the BCC-UFig simulation to construct galaxy samples mimicking those used in SV galaxy clustering studies. We show that the spatially varying survey depth imprinted in the observed galaxy densities and the redshift distributions of the SV data are successfully reproduced by the simulation and are well-captured by the maps of observing conditions. The combined use of the maps, the SV data, and the BCC-UFig simulation allows us to quantify the impact of spatial systematics on N(z), the redshift distributions inferred using photometric redshifts. We conclude that spatial systematics in the SV data are mainly due to seeing fluctuations and are under control in current clustering and weak-lensing analyses. However, they will need to be carefully characterized in upcoming phases of DES in order to avoid biasing the inferred cosmological results. The framework presented here is relevant to all multi-epoch surveys and will be essential for exploiting future surveys such as the Large Synoptic Survey Telescope, which will require detailed null tests and realistic end-to-end image simulations to correctly interpret the deep, high
DOE Office of Scientific and Technical Information (OSTI.GOV)
Leistedt, B.; Peiris, H. V.; Elsner, F.
Spatially-varying depth and characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey analyses, in particular in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. Wemore » illustrate the complementarity of these two approaches by comparing the SV data with the BCC-UFig, a synthetic sky catalogue generated by forward-modelling of the DES SV images. We then analyse the BCC-UFig simulation to construct galaxy samples mimicking those used in SV galaxy clustering studies. We show that the spatially-varying survey depth imprinted in the observed galaxy densities and the redshift distributions of the SV data are successfully reproduced by the simulation and well-captured by the maps of observing conditions. The combined use of the maps, the SV data and the BCC-UFig simulation allows us to quantify the impact of spatial systematics on N(z), the redshift distributions inferred using photometric redshifts. We conclude that spatial systematics in the SV data are mainly due to seeing fluctuations and are under control in current clustering and weak lensing analyses. However, they will need to be carefully characterised in upcoming phases of DES in order to avoid biasing the inferred cosmological results. The framework presented is relevant to all multi-epoch surveys, and will be essential for exploiting future surveys such as the Large Synoptic Survey Telescope, which will require detailed null-tests and realistic end-to-end image simulations to correctly interpret the deep, high
Mars boundary layer simulations - Comparison with Viking lander and entry observations
NASA Technical Reports Server (NTRS)
Haberle, R. M.; Houben, H. C.
1991-01-01
Diurnal variations of wind and temperature in the lower Martian atmosphere are simulated with a boundary layer model that includes radiative heating in a dusty CO2 atmosphere, turbulence generated by convection and/or shear stresses, a surface heat budget, and time varying pressure forces due to sloping terrain. Model results for early northern summer are compared with Viking lander observations to determine the model's strengths and weaknesses, and suitability as an engineering model.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Benincasa, Samantha M.; Pudritz, Ralph E.; Wadsley, James
We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10{sup 4} M{sub ☉} and 10{sup 7} M{sub ☉}. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulatedmore » cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n{sub thresh} ≥ 10{sup 4} cm{sup –3}—is 3% per 10 Myr, in clouds of roughly 10{sup 6} M{sub ☉}. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.« less
Partial Variance of Increments Method in Solar Wind Observations and Plasma Simulations
NASA Astrophysics Data System (ADS)
Greco, A.; Matthaeus, W. H.; Perri, S.; Osman, K. T.; Servidio, S.; Wan, M.; Dmitruk, P.
2018-02-01
The method called "PVI" (Partial Variance of Increments) has been increasingly used in analysis of spacecraft and numerical simulation data since its inception in 2008. The purpose of the method is to study the kinematics and formation of coherent structures in space plasmas, a topic that has gained considerable attention, leading the development of identification methods, observations, and associated theoretical research based on numerical simulations. This review paper will summarize key features of the method and provide a synopsis of the main results obtained by various groups using the method. This will enable new users or those considering methods of this type to find details and background collected in one place.
Observation and simulation of AGW in Space
NASA Astrophysics Data System (ADS)
Kunitsyn, Vyacheslav; Kholodov, Alexander; Andreeva, Elena; Nesterov, Ivan; Padokhin, Artem; Vorontsov, Artem
2014-05-01
Examples are presented of satellite observations and imaging of AGW and related phenomena in space travelling ionospheric disturbances (TID). The structure of AGW perturbations was reconstructed by satellite radio tomography (RT) based on the signals of Global Navigation Satellite Systems (GNSS). The experiments use different GNSS, both low-orbiting (Russian Tsikada and American Transit) and high-orbiting (GPS, GLONASS, Galileo, Beidou). The examples of RT imaging of TIDs and AGWs from anthropogenic sources such as ground explosions, rocket launching, heating the ionosphere by high-power radio waves are presented. In the latter case, the corresponding AGWs and TIDs were generated in response to the modulation in the power of the heating wave. The natural AGW-like wave disturbances are frequently observed in the atmosphere and ionosphere in the form of variations in density and electron concentration. These phenomena are caused by the influence of the near-space environment, atmosphere, and surface phenomena including long-period vibrations of the Earth's surface, earthquakes, explosions, temperature heating, seisches, tsunami waves, etc. Examples of experimental RT reconstructions of wave disturbances associated with the earthquakes and tsunami waves are presented, and RT images of TIDs caused by the variations in the corpuscular ionization are demonstrated. The results of numerical modeling of AGW generation by some surface and volume sources are discussed. The milli-Hertz AGWs generated by these sources induce perturbations with a typical scale of a few hundred of kilometers at the heights of the middle atmosphere and ionosphere. The numerical modeling is based on the solution of equations of geophysical hydrodynamics. The results of the numerical simulations agree with the observations. The authors acknowledge the support of the Russian Foundation for Basic Research (grants 14-05-00855 and 13-05-01122), grant of the President of Russian Federation MK-2670
Comparison of solar photospheric bright points between Sunrise observations and MHD simulations
NASA Astrophysics Data System (ADS)
Riethmüller, T. L.; Solanki, S. K.; Berdyugina, S. V.; Schüssler, M.; Martínez Pillet, V.; Feller, A.; Gandorfer, A.; Hirzberger, J.
2014-08-01
Bright points (BPs) in the solar photosphere are thought to be the radiative signatures (small-scale brightness enhancements) of magnetic elements described by slender flux tubes or sheets located in the darker intergranular lanes in the solar photosphere. They contribute to the ultraviolet (UV) flux variations over the solar cycle and hence may play a role in influencing the Earth's climate. Here we aim to obtain a better insight into their properties by combining high-resolution UV and spectro-polarimetric observations of BPs by the Sunrise Observatory with 3D compressible radiation magnetohydrodynamical (MHD) simulations. To this end, full spectral line syntheses are performed with the MHD data and a careful degradation is applied to take into account all relevant instrumental effects of the observations. In a first step it is demonstrated that the selected MHD simulations reproduce the measured distributions of intensity at multiple wavelengths, line-of-sight velocity, spectral line width, and polarization degree rather well. The simulated line width also displays the correct mean, but a scatter that is too small. In the second step, the properties of observed BPs are compared with synthetic ones. Again, these are found to match relatively well, except that the observations display a tail of large BPs with strong polarization signals (most likely network elements) not found in the simulations, possibly due to the small size of the simulation box. The higher spatial resolution of the simulations has a significant effect, leading to smaller and more numerous BPs. The observation that most BPs are weakly polarized is explained mainly by the spatial degradation, the stray light contamination, and the temperature sensitivity of the Fe i line at 5250.2 Å. Finally, given that the MHD simulations are highly consistent with the observations, we used the simulations to explore the properties of BPs further. The Stokes V asymmetries increase with the distance to the
Comparison of Tropical and Extratropical Gust Factors Using Observed and Simulated Data
NASA Astrophysics Data System (ADS)
Edwards, R. P.; Schroeder, J. L.
2011-12-01
Questions of whether differences exist between tropical cyclone (TC) and extratropical (ET) wind have been the subject of considerable debate. This study will focus on the behavior of the gust factor (GF), the ratio of a peak wind speed of a certain duration and a mean wind speed of a certain duration, for three types of data: TC, ET, and simulated. For this project, the Universal Spectrum, a normalized, averaged spectrum for wind, was un-normalized and used to create simulated wind speed time series at a variety of wind speeds. Additional time series were created after modifying the spectrum to simulate the additional low-frequency energy observed in the TC wind spectrum as well as the reduction of high-frequency energy caused by a mechanical anemometer. The T and ET data used for this study were collected by Texas Tech University's mobile towers as part of various field efforts since 1998. Before comparisons were made, the database was divided into four roughness regimes based on the roughness length to ensure that differences observed in the turbulence statistics are not caused by differences in upstream terrain. The mean GF for the TC data set (open roughness regime), 1.49, was slightly higher than the ET value of 1.44 (Table 1). The distributions of GFs from each data type show similarities in shape between the base-simulated and ET data sets and between the TC and modified-simulated data set (Figure 1). These similarities are expected given the spectral similarities between the TC and modified-simulated data sets, namely additional low-frequency energy relative to the ET and base-simulated data. These findings suggest that the higher amount of low-frequency energy present in the tropical wind spectrum is partially responsible for the resulting higher GF for the tropical cyclone data. However, the modest increase in GF from the base to the modified simulated data suggest that there are more factors at work.
NASA Technical Reports Server (NTRS)
Berchem, J.; Raeder, J.; Ashour-Abdalla, M.; Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Yamamoto, T.; Lepping, R. P.
1998-01-01
Understanding the large-scale dynamics of the magnetospheric boundary is an important step towards achieving the ISTP mission's broad objective of assessing the global transport of plasma and energy through the geospace environment. Our approach is based on three-dimensional global magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere- ionosphere system, and consists of using interplanetary magnetic field (IMF) and plasma parameters measured by solar wind monitors upstream of the bow shock as input to the simulations for predicting the large-scale dynamics of the magnetospheric boundary. The validity of these predictions is tested by comparing local data streams with time series measured by downstream spacecraft crossing the magnetospheric boundary. In this paper, we review results from several case studies which confirm that our MHD model reproduces very well the large-scale motion of the magnetospheric boundary. The first case illustrates the complexity of the magnetic field topology that can occur at the dayside magnetospheric boundary for periods of northward IMF with strong Bx and By components. The second comparison reviewed combines dynamic and topological aspects in an investigation of the evolution of the distant tail at 200 R(sub E) from the Earth.
NASA Technical Reports Server (NTRS)
Yeh, Hwa-Young M.; Prasad, N.; Mack, Robert A.; Adler, Robert F.
1990-01-01
In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.
NASA Astrophysics Data System (ADS)
Zhang, Z.; Song, H.; Wang, M.; Ghan, S. J.; Dong, X.
2016-12-01
he main objective of this study is to systematically evaluate the MBL cloud properties simulated in CAM5 family models using a combination of satellite-based CloudSat/MODIS observations and ground-based observations from the ARM Azores site, with a special focus on MBL cloud microphysics and warm rain process. First, we will present a global evaluation based on satellite observations and retrievals. We will compare global cloud properties (e.g., cloud fraction, cloud vertical structure, cloud CER, COT, and LWP, as well as drizzle frequency and intensity diagnosed using the CAM5-COSP instrumental simulators) simulated in the CAM5 models with the collocated CloudSat and MODIS observations. We will also present some preliminary results from a regional evaluation based mainly on ground observations from ARM Azores site. We will compare MBL cloud properties simulated in CAM5 models over the ARM Azores site with collocated satellite (MODIS and CloudSat) and ground-based observations from the ARM site.
Ram Pressure Stripping: Observations Meet Simulations
NASA Astrophysics Data System (ADS)
Past, Matthew; Ruszkowski, Mateusz; Sharon, Keren
2017-01-01
Ram pressure stripping occurs when a galaxy falls into the potential well of a cluster, removing gas and dust as the galaxy travels through the intracluster medium. This interaction leads to filamentary gas tails stretching behind the galaxy and plays an important role in galaxy evolution. Previously, these “jellyfish” galaxies had only been observed in nearby clusters, but recently, higher redshift (z > 0.3) examples have been found from HST data imaging.Recent work has shown that cosmic rays injected by supernovae can cause galactic disks to thicken due to cosmic ray pressure. We run three-dimensional magneto-hydrodynamical simulations of ram pressure stripping including cosmic rays to compare to previous models. We study how the efficiency of the ram pressure stripping of the gas, and the morphology of the filamentary tails, depend on the magnitude of the cosmic ray pressure support. We generate mock X-ray images and radio polarization data. Simultaneously, we perform an exhaustive search of the HST archive to increase the sample of jellyfish galaxies and compare selected cases to simulations.
Retrieved Products from Simulated Hyperspectral Observations of a Hurricane
NASA Technical Reports Server (NTRS)
Susskind, Joel; Kouvaris, Louis; Iredell, Lena; Blaisdell, John
2015-01-01
Retrievals were run using the AIRS Science Team Version-6 AIRS Only retrieval algorithm, which generates a Neural-Net first guess (T(sub s))(sup 0), (T(p))(sup 0), and (q(p))(sup 0) as a function of observed AIRS radiances. AIRS Science Team Neural-Net coefficients performed very well beneath 300 mb using the simulated radiances. This means the simulated radiances are very realistic. First guess and retrieved values of T(p) above 300 mb were biased cold, but both represented the model spatial structure very well. QC'd T(p) and q(p) retrievals for all experiments had similar accuracies compared to their own truth fields, and were roughly consistent with results obtained using real data. Spatial coverage of retrievals, as well as the representativeness of the spatial structure of the storm, improved dramatically with decreasing size of the instrument's FOV. We sent QC'd values of T(p) and q(p) to Bob Atlas at AOML for use as input to OSSE Data Assimilation experiments.
Infrared Spectral Observations While Drilling into a Frozen Lunar Simulant
NASA Technical Reports Server (NTRS)
Roush, Ted L.; Colaprete, Anthony; Thompson, Sarah; Cook, Amanda; Kleinhenz, Julie
2014-01-01
Past and continuing observations indicate an enrichment of volatile materials in lunar polar regions. While these volatiles may be located near the surface, access to them will likely require subsurface sampling, during which it is desirable to monitor the volatile content. In a simulation of such activities, a multilayer lunar simulant was prepared with differing water content, and placed inside a thermal vacuum chamber at Glenn Research Center (GRC). The soil profile was cooled using liquid nitrogen. In addition to the soil, a drill and infrared (IR) spectrometer (1600-3400 nm) were also located in the GRC chamber. We report the spectral observations obtained during a sequence where the drill was repeatedly inserted and extracted, to different depths, at the same location. We observe an overall increase in the spectral signature of water ice over the duration of the test. Additionally, we observe variations in the water ice spectral signature as the drill encounters different layers.
Simulation of keratoconus observation in photorefraction
NASA Astrophysics Data System (ADS)
Chen, Ying-Ling; Tan, B.; Baker, K.; Lewis, J. W. L.; Swartz, T.; Jiang, Y.; Wang, M.
2006-11-01
In the recent years, keratoconus (KC) has increasingly gained attention due to its treatment options and to the popularity of keratorefractive surgery. This paper investigates the potential of identification of KC using photorefraction (PR), an optical technique that is similar to objective retinoscopy and is commonly used for large-scale ocular screening. Using personalized eye models of both KC and pre-LASIK patients, computer simulations were performed to achieve visualization of this ophthalmic measurement. The simulations are validated by comparing results to two sets of experimental measurements. These PR images show distinguishable differences between KC eyes and eyes that are either normal or ametropic. The simulation technique with personalized modeling can be extended to other ophthalmic instrument developments. It makes possible investigation with the least number of real human subjects. The application is also of great interest in medical training.
3-D VPIC simulation of an vortex-induced reconnection event observed by MMS
Nakamura, Takuma; Daughton, William
2016-01-01
The data set consists of a 3-D fully kinetic (VPIC) simulation of an in-situ observation event at the Earth's magnetopause by the NASA MMS spacecraft on September 8, 2015. The results show a turbulent development of magnetic reconnection induced by the Kelvin-Helmohltz vortex, and resulting significantly efficient plasma mixing across the magnetopause. The vortex-induced reconnection signatures are well consistent with the MMS observations. These results are published in some scientific journals such as Nature Communications. Fortran unformatted files with 1024x1536x512 cells, which have been compressed from original ones with 2048x3072x1024 cells, are archived for selected time slices of field and moment data shown in these papers.
Comparisons of Spectra from 3D Kinetic Meteor PIC Simulations with Theory and Observations
NASA Astrophysics Data System (ADS)
Oppenheim, M. M.; Tarnecki, L. K.
2017-12-01
Meteoroids smaller than a grain of sand have significant impacts on the composition, chemistry, and dynamics of the atmosphere. The processes by which they turbulently diffuse can be studied using collisional kinetic particle-in-cell (PIC) simulations. Spectral analysis is a valuable tool for comparing such simulations of turbulent, non-specular meteor trails with observations. We present three types of spectral information: full spectra along the trail in k-ω space, spectral widths at common radar frequencies, and power as a function of angle with respect to B. These properties can be compared to previously published data. Zhou et al. (2004) use radar theory to predict the power observed by a radar as a function of the angle between the meteor trail and the radar beam and the size of field-aligned irregularities (FAI) within the trail. Close et al. (2008) present observations of meteor trails from the ALTAIR radar, including power returned as a function of angle off B for a small sample of meteors. Close et al. (2008) and Zhou et al. (2004) both suggest a power drop off of 2-3 dB per degree off perpendicular to B. We compare results from our simulations with both theory and observations for a range of conditions, including trail altitude and incident neutral wind speed. For 1m waves, power fell off by 1-3 dB per degree off perpendicular to B. These comparisons help determine if small-scale simulations accurately capture the behavior of real meteors.
The role of historical forcings in simulating the observed Atlantic multidecadal oscillation
NASA Astrophysics Data System (ADS)
Murphy, Lisa N.; Bellomo, Katinka; Cane, Mark; Clement, Amy
2017-03-01
We analyze the Atlantic multidecadal oscillation (AMO) in the preindustrial (PI) and historical (HIST) simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to assess the drivers of the observed AMO from 1865 to 2005. We draw 141 year samples from the 41 CMIP5 model's PI runs and compare the correlation and variance between the observed AMO and the simulated PI and HIST AMO. The correlation coefficients in 38 forced (HIST) models are above the 90% confidence level and explain up to 56% of the observed variance. The probability that any of the unforced (PI) models do as well is less than 3% in 31 models. Multidecadal variability is larger in 39 CMIP5 HIST simulations and in all HIST members of the Community Earth System Model Large Ensemble than their corresponding PI. We conclude that there is an essential role for external forcing in driving the observed AMO.
NASA Astrophysics Data System (ADS)
Koenders, C.; Perschke, C.; Goetz, C.; Richter, I.; Motschmann, U.; Glassmeier, K. H.
2016-10-01
Context. A new type of low-frequency wave was detected by the magnetometer of the Rosetta Plasma Consortium at the comet during the initial months after the arrival of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. This large-amplitude, nearly continuous wave activity is observed in the frequency range from 30 mHz to 80 mHz where 40 mHz to 50 mHz is the dominant frequency. This type of low frequency is not closely related to the gyrofrequency of newborn cometary ions, which differs from previous wave activity observed in the interaction region of comets with the solar wind. Aims: This work aims to reveal a global view on the wave activity region using simulations of the comet-solar wind interaction region. Parameters, such as wavelength, propagation direction, and propagation patterns, are within the focus of this study. While the Rosetta observations only provide local information, numerical simulations provide further information on the global wave properties. Methods: Standard hybrid simulations were applied to the comet-solar wind interaction scenario. In the model, the ions were described as particles, which allows us to describe kinetic processes of the ions. The electrons were described as a fluid. Results: The simulations exhibit a threefold wave structure of the interaction region. A Mach cone and a Whistler wing are observed downstream of the comet. The third kind of wave activity found are low-frequency waves at 97 mHz, which corresponds to the waves observed by Richter et al. (2015, Ann. Geophys., 33, 1031). These waves are caused by the initial pick-up of the cometary ions that are perpendicular to the solar wind flow and in the interplanetary magnetic field direction. The associated electric current becomes unstable. The simulations show that wave activity is only detectable in the + E hemisphere and that the Mach cone and whistler wings need to be distinguished from the newly found instability driven wave activity. The movie associated to
Johnson, R.H.; Poeter, E.P.
2007-01-01
Perchloroethylene (PCE) saturations determined from GPR surveys were used as observations for inversion of multiphase flow simulations of a PCE injection experiment (Borden 9??m cell), allowing for the estimation of optimal bulk intrinsic permeability values. The resulting fit statistics and analysis of residuals (observed minus simulated PCE saturations) were used to improve the conceptual model. These improvements included adjustment of the elevation of a permeability contrast, use of the van Genuchten versus Brooks-Corey capillary pressure-saturation curve, and a weighting scheme to account for greater measurement error with larger saturation values. A limitation in determining PCE saturations through one-dimensional GPR modeling is non-uniqueness when multiple GPR parameters are unknown (i.e., permittivity, depth, and gain function). Site knowledge, fixing the gain function, and multiphase flow simulations assisted in evaluating non-unique conceptual models of PCE saturation, where depth and layering were reinterpreted to provide alternate conceptual models. Remaining bias in the residuals is attributed to the violation of assumptions in the one-dimensional GPR interpretation (which assumes flat, infinite, horizontal layering) resulting from multidimensional influences that were not included in the conceptual model. While the limitations and errors in using GPR data as observations for inverse multiphase flow simulations are frustrating and difficult to quantify, simulation results indicate that the error and bias in the PCE saturation values are small enough to still provide reasonable optimal permeability values. The effort to improve model fit and reduce residual bias decreases simulation error even for an inversion based on biased observations and provides insight into alternate GPR data interpretations. Thus, this effort is warranted and provides information on bias in the observation data when this bias is otherwise difficult to assess. ?? 2006 Elsevier B
ICE-COLA: fast simulations for weak lensing observables
NASA Astrophysics Data System (ADS)
Izard, Albert; Fosalba, Pablo; Crocce, Martin
2018-01-01
Approximate methods to full N-body simulations provide a fast and accurate solution to the development of mock catalogues for the modelling of galaxy clustering observables. In this paper we extend ICE-COLA, based on an optimized implementation of the approximate COLA method, to produce weak lensing maps and halo catalogues in the light-cone using an integrated and self-consistent approach. We show that despite the approximate dynamics, the catalogues thus produced enable an accurate modelling of weak lensing observables one decade beyond the characteristic scale where the growth becomes non-linear. In particular, we compare ICE-COLA to the MICE Grand Challenge N-body simulation for some fiducial cases representative of upcoming surveys and find that, for sources at redshift z = 1, their convergence power spectra agree to within 1 per cent up to high multipoles (i.e. of order 1000). The corresponding shear two point functions, ξ+ and ξ-, yield similar accuracy down to 2 and 20 arcmin respectively, while tangential shear around a z = 0.5 lens sample is accurate down to 4 arcmin. We show that such accuracy is stable against an increased angular resolution of the weak lensing maps. Hence, this opens the possibility of using approximate methods for the joint modelling of galaxy clustering and weak lensing observables and their covariance in ongoing and future galaxy surveys.
NASA Technical Reports Server (NTRS)
Kubat, Gregory
2016-01-01
This report addresses a deliverable to the UAS-in-the-NAS project for recommendations for integration of CNPC and ATC communications based on analysis results from modeled radio system and NAS-wide UA communication architecture simulations. For each recommendation, a brief explanation of the rationale for its consideration is provided with any supporting results obtained or observed in our simulation activity.
Evaluating Clouds in Long-Term Cloud-Resolving Model Simulations with Observational Data
NASA Technical Reports Server (NTRS)
Zeng, Xiping; Tao, Wei-Kuo; Zhang, Minghua; Peters-Lidard, Christa; Lang, Stephen; Simpson, Joanne; Kumar, Sujay; Xie, Shaocheng; Eastman, Joseph L.; Shie, Chung-Lin;
2006-01-01
Two 20-day, continental midlatitude cases are simulated with a three-dimensional (3D) cloud-resolving model (CRM) and compared to Atmospheric Radiation Measurement (ARM) data. This evaluation of long-term cloud-resolving model simulations focuses on the evaluation of clouds and surface fluxes. All numerical experiments, as compared to observations, simulate surface precipitation well but over-predict clouds, especially in the upper troposphere. The sensitivity of cloud properties to dimensionality and other factors is studied to isolate the origins of the over prediction of clouds. Due to the difference in buoyancy damping between 2D and 3D models, surface precipitation fluctuates rapidly with time, and spurious dehumidification occurs near the tropopause in the 2D CRM. Surface fluxes from a land data assimilation system are compared with ARM observations. They are used in place of the ARM surface fluxes to test the sensitivity of simulated clouds to surface fluxes. Summertime simulations show that surface fluxes from the assimilation system bring about a better simulation of diurnal cloud variation in the lower troposphere.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Feldman, D.R.; Algieri, C.A.; Ong, J.R.
2011-04-01
Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensivelymore » validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and poleward shifts in the subsidence zones and the storm tracks are all detectable along with large changes in snow cover and sea ice fraction. These findings suggest that the proposed NASA Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to measure shortwave reflectance spectra may help elucidate climate forcings, responses, and feedbacks.« less
Simulation and 'TWINS Observations of the 22 July 2009 Storm
NASA Technical Reports Server (NTRS)
Fok, Mei-Ching; Buzulukova, Natalia Y.; Chen, Sheng-Hsien; Valek, Phil; Goldstein, Jerry; McComas, David
2010-01-01
TWINS is the first mission to perform stereo imaging of the Earth's ring current. The magnetic storm on 22 July 2009 is the largest storm observed since TWINS began routine stereo imaging in June 2008. On 22 July 2009, the Dst dropped to nearly -80nT at 7:00 and 10:00 UT. During the main phase and at the peak of the storm, TWINS 1 and 2 were near apogee and moving from pre-dawn to post-dawn local time. The energetic neutral atom (ENA) imagers on the 2 spacecraft captured the storm intensification and the formation of the partial ring current. The peak of the ENA emissions was seen in the midnight-to-dawn local-time sector. The development of this storm has been simulated using the Comprehensive Ring Current Model (CRCM) to understand and interpret the observed signatures. We perform CRCM runs with constant and time-varying magnetic field. The model calculations are validated by comparing the simulated ENA and ion flux intensities with TWINS ENA images and in-situ ion data from THEMIS satellites. Simulation with static magnetic field produces a strong shielding electric field that skews the ion drift trajectories toward dawn. The model's corresponding peak ENA emissions are always eastward than those in the observed TWINS images. On the other hand, simulation with a dynamic magnetic field gives better spatial agreements with both ENA and insitu particle data, suggesting that temporal variations of the geomagnetic field exert a significant influence upon global ring current ion dynamics.
Simulation and Twins Observations of the 22 July 2009 Storm
NASA Technical Reports Server (NTRS)
Fok, M.-C.; Buzulukova, N.; Chen, S.-H.; Valek, P. W.; Goldstein, J.; McComas, D. J.
2011-01-01
TWINS is the first mission to perform stereo imaging of the Earth's ring current. The magnetic storm on 22 July 2009 was at the time the largest storm observed since TWINS began routine stereo imaging in June 2008. On 22 July 2009, the Dst dropped to nearly .80 nT at 0700 and 1000 UT. During the main phase, and at the peak of the storm, TWINS 1 and 2 were near apogee and moving between predawn and postdawn local time. The energetic neutral atom (ENA) imagers on the two spacecraft captured the storm intensification and the formation of the partial ring current. The peak of the high-altitude ENA emissions was seen in the midnight-to-dawn local time sector. The development of this storm has been simulated using the comprehensive ring current model (CRCM) to understand and interpret the observed signatures. We perform CRCM runs with constant and time-varying magnetic field. The model calculations are validated by comparing the simulated ENA and ion flux intensities with TWINS ENA images and in situ ion data from a THEMIS satellite. Simulation with a static magnetic field produces a strong shielding electric field that skews the ion drift trajectories toward dawn. The model's corresponding peak ENA emissions are always more eastward than those in the observed TWINS images. On the other hand, the simulation with a dynamic magnetic field gives better spatial agreement with both ENA and in situ particle data, suggesting that temporal variations of the geomagnetic field exert a significant influence upon global ring current ion dynamics.
Marvel-ous Dwarfs: Results from Four Heroically Large Simulated Volumes of Dwarf Galaxies
NASA Astrophysics Data System (ADS)
Munshi, Ferah; Brooks, Alyson; Weisz, Daniel; Bellovary, Jillian; Christensen, Charlotte
2018-01-01
We present results from high resolution, fully cosmological simulations of cosmic sheets that contain many dwarf galaxies. Together, they create the largest collection of simulated dwarf galaxies to date, with z=0 stellar masses comparable to the LMC or smaller. In total, we have simulated almost 100 luminous dwarf galaxies, forming a sample of simulated dwarfs which span a wide range of physical (stellar and halo mass) and evolutionary properties (merger history). We show how they can be calibrated against a wealth of observations of nearby galaxies including star formation histories, HI masses and kinematics, as well as stellar metallicities. We present preliminary results answering the following key questions: What is the slope of the stellar mass function at extremely low masses? Do halos with HI and no stars exist? What is the scatter in the stellar to halo mass relationship as a function of dwarf mass? What drives the scatter? With this large suite, we are beginning to statistically characterize dwarf galaxies and identify the types and numbers of outliers to expect.
Bayraktar, Meriç; Männer, Jörg
2014-01-01
The transformation of the straight embryonic heart tube into a helically wound loop is named cardiac looping. Such looping is regarded as an essential process in cardiac morphogenesis since it brings the building blocks of the developing heart into an approximation of their definitive topographical relationships. During the past two decades, a large number of genes have been identified which play important roles in cardiac looping. However, how genetic information is physically translated into the dynamic form changes of the looping heart is still poorly understood. The oldest hypothesis of cardiac looping mechanics attributes the form changes of the heart loop (ventral bending → simple helical coiling → complex helical coiling) to compressive loads resulting from growth differences between the heart and the pericardial cavity. In the present study, we have tested the physical plausibility of this hypothesis, which we call the growth-induced buckling hypothesis, for the first time. Using a physical simulation model, we show that growth-induced buckling of a straight elastic rod within the confined space of a hemispherical cavity can generate the same sequence of form changes as observed in the looping embryonic heart. Our simulation experiments have furthermore shown that, under bilaterally symmetric conditions, growth-induced buckling generates left- and right-handed helices (D-/L-loops) in a 1:1 ratio, while even subtle left- or rightward displacements of the caudal end of the elastic rod at the pre-buckling state are sufficient to direct the buckling process toward the generation of only D- or L-loops, respectively. Our data are discussed with respect to observations made in biological “models.” We conclude that compressive loads resulting from unequal growth of the heart and pericardial cavity play important roles in cardiac looping. Asymmetric positioning of the venous heart pole may direct these forces toward a biased generation of D- or L-loops. PMID
NASA Technical Reports Server (NTRS)
Varble, Adam; Fridlind, Ann M.; Zipser, Edward J.; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben
2011-01-01
The Tropical Warm Pool.International Cloud Experiment (TWP ]ICE) provided extensive observational data sets designed to initialize, force, and constrain atmospheric model simulations. In this first of a two ]part study, precipitation and cloud structures within nine cloud ]resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Seven of nine simulations overestimate convective area by 20% or more leading to general overestimation of convective rainfall. This is balanced by underestimation of stratiform rainfall by 5% to 50% despite overestimation of stratiform area by up to 65% because of a preponderance of very low stratiform rain rates in all simulations. All simulations fail to reproduce observed radar reflectivity distributions above the melting level in convective regions and throughout the troposphere in stratiform regions. Observed precipitation ]sized ice reaches higher altitudes than simulated precipitation ]sized ice despite some simulations that predict lower than observed top ]of ]atmosphere infrared brightness temperatures. For the simulations that overestimate radar reflectivity aloft, graupel is the cause with one ]moment microphysics schemes whereas snow is the cause with two ]moment microphysics schemes. Differences in simulated radar reflectivity are more highly correlated with differences in mass mean melted diameter (Dm) than differences in ice water content. Dm is largely dependent on the mass ]dimension relationship and gamma size distribution parameters such as size intercept (N0) and shape parameter (m). Having variable density, variable N0, or m greater than zero produces radar reflectivities closest to those observed.
Arctic daily temperature and precipitation extremes: Observed and simulated physical behavior
NASA Astrophysics Data System (ADS)
Glisan, Justin Michael
Simulations using a six-member ensemble of Pan-Arctic WRF (PAW) were produced on two Arctic domains with 50-km resolution to analyze precipitation and temperature extremes for various periods. The first study used a domain developed for the Regional Arctic Climate Model (RACM). Initial simulations revealed deep atmospheric circulation biases over the northern Pacific Ocean, manifested in pressure, geopotential height, and temperature fields. Possible remedies to correct these large biases, such as modifying the physical domain or using different initial/boundary conditions, were unsuccessful. Spectral (interior) nudging was introduced as a way of constraining the model to be more consistent with observed behavior. However, such control over numerical model behavior raises concerns over how much nudging may affect unforced variability and extremes. Strong nudging may reduce or filter out extreme events, since the nudging pushes the model toward a relatively smooth, large-scale state. The question then becomes---what is the minimum spectral nudging needed to correct biases while not limiting the simulation of extreme events? To determine this, we use varying degrees of spectral nudging, using WRF's standard nudging as a reference point during January and July 2007. Results suggest that there is a marked lack of sensitivity to varying degrees of nudging. Moreover, given that nudging is an artificial forcing applied in the model, an important outcome of this work is that nudging strength apparently can be considerably smaller than WRF's standard strength and still produce reliable simulations. In the remaining studies, we used the same PAW setup to analyze daily precipitation extremes simulated over a 19-year period on the CORDEX Arctic domain for winter and summer. We defined these seasons as the three-month period leading up to and including the climatological sea ice maximum and minimum, respectively. Analysis focused on four North American regions defined using
NASA Technical Reports Server (NTRS)
Cheng, Yen-Ben; Middleton, Elizabeth M.; Zhang, Qingyuan; Corp, Lawrence A.; Dandois, Jonathan; Kustas, William P.
2012-01-01
The two-layer Markov chain Analytical Canopy Reflectance Model (ACRM) was linked with in situ hyperspectral leaf optical properties to simulate the Photochemical Reflectance Index (PRI) for a corn crop canopy at three different growth stages. This is an extended study after a successful demonstration of PRI simulations for a cornfield previously conducted at an early vegetative growth stage. Consistent with previous in situ studies, sunlit leaves exhibited lower PRI values than shaded leaves. Since sunlit (shaded) foliage dominates the canopy in the reflectance hotspot (coldspot), the canopy PRI derived from field hyperspectral observations displayed sensitivity to both view zenith angle and relative azimuth angle at all growth stages. Consequently, sunlit and shaded canopy sectors were most differentiated when viewed along the azimuth matching the solar principal plane. These directional PRI responses associated with sunlit/shaded foliage were successfully reproduced by the ACRM. As before, the simulated PRI values from the current study were closer to in situ values when both sunlit and shaded leaves were utilized as model input data in a two-layer mode, instead of a one-layer mode with sunlit leaves only. Model performance as judged by correlation between in situ and simulated values was strongest for the mature corn crop (r = 0.87, RMSE = 0.0048), followed by the early vegetative stage (r = 0.78; RMSE = 0.0051) and the early senescent stage (r = 0.65; RMSE = 0.0104). Since the benefit of including shaded leaves in the scheme varied across different growth stages, a further analysis was conducted to investigate how variable fractions of sunlit/shaded leaves affect the canopy PRI values expected for a cornfield, with implications for 20 remote sensing monitoring options. Simulations of the sunlit to shaded canopy ratio near 50/50 +/- 10 (e.g., 60/40) matching field observations at all growth stages were examined. Our results suggest in the importance of the
Synchrony between reanalysis-driven RCM simulations and observations: variation with time scale
NASA Astrophysics Data System (ADS)
de Elía, Ramón; Laprise, René; Biner, Sébastien; Merleau, James
2017-04-01
Unlike coupled global climate models (CGCMs) that run in a stand-alone mode, nested regional climate models (RCMs) are driven by either a CGCM or a reanalysis dataset. This feature makes high correlations between the RCM simulation and its driver possible. When the driving dataset is a reanalysis, time correlations between RCM output and observations are also common and to be expected. In certain situations time correlation between driver and driven RCM is of particular interest and techniques have been developed to increase it (e.g. large-scale spectral nudging). For such cases, a question that remains open is whether aggregating in time increases the correlation between RCM output and observations. That is, although the RCM may be unable to reproduce a given daily event, whether it will still be able to satisfactorily simulate an anomaly on a monthly or annual basis. This is a preconception that the authors of this work and others in the community have held, perhaps as a natural extension of the properties of upscaling or aggregating other statistics such as the mean squared error. Here we explore analytically four particular cases that help us partially answer this question. In addition, we use observations datasets and RCM-simulated data to illustrate our findings. Results indicate that time upscaling does not necessarily increase time correlations, and that those interested in achieving high monthly or annual time correlations between RCM output and observations may have to do so by increasing correlation as much as possible at the shortest time scale. This may indicate that even when only concerned with time correlations at large temporal scale, large-scale spectral nudging acting at the time-step level may have to be used.
Virtual Observation System for Earth System Model: An Application to ACME Land Model Simulations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, Dali; Yuan, Fengming; Hernandez, Benjamin
Investigating and evaluating physical-chemical-biological processes within an Earth system model (EMS) can be very challenging due to the complexity of both model design and software implementation. A virtual observation system (VOS) is presented to enable interactive observation of these processes during system simulation. Based on advance computing technologies, such as compiler-based software analysis, automatic code instrumentation, and high-performance data transport, the VOS provides run-time observation capability, in-situ data analytics for Earth system model simulation, model behavior adjustment opportunities through simulation steering. A VOS for a terrestrial land model simulation within the Accelerated Climate Modeling for Energy model is also presentedmore » to demonstrate the implementation details and system innovations.« less
Virtual Observation System for Earth System Model: An Application to ACME Land Model Simulations
Wang, Dali; Yuan, Fengming; Hernandez, Benjamin; ...
2017-01-01
Investigating and evaluating physical-chemical-biological processes within an Earth system model (EMS) can be very challenging due to the complexity of both model design and software implementation. A virtual observation system (VOS) is presented to enable interactive observation of these processes during system simulation. Based on advance computing technologies, such as compiler-based software analysis, automatic code instrumentation, and high-performance data transport, the VOS provides run-time observation capability, in-situ data analytics for Earth system model simulation, model behavior adjustment opportunities through simulation steering. A VOS for a terrestrial land model simulation within the Accelerated Climate Modeling for Energy model is also presentedmore » to demonstrate the implementation details and system innovations.« less
NASA Technical Reports Server (NTRS)
Cummings, Kristin A.; Pickering, Kenneth E.; Barth, M.; Bela, M.; Li, Y.; Allen, D.; Bruning, E.; MacGorman, D.; Rutledge, S.; Basarab, B.;
2016-01-01
The focus of this analysis is on lightning-generated nitrogen oxides (LNOx) and their distribution for two thunderstorms observed during the Deep Convective Clouds and Chemistry (DC3) field campaign in May-June 2012. The Weather Research and Forecasting Chemistry (WRF-Chem) model is used to perform cloud-resolved simulations for the May 29-30 Oklahoma severe convection, which contained one supercell, and the June 6-7 Colorado squall line. Aircraft and ground-based observations (e.g., trace gases, lightning and radar) collected during DC3 are used in comparisons against the model-simulated lightning flashes generated by the flash rate parameterization schemes (FRPSs) incorporated into the model, as well as the model-simulated LNOx predicted in the anvil outflow. Newly generated FRPSs based on DC3 radar observations and Lightning Mapping Array data are implemented in the model, along with previously developed schemes from the literature. The results of these analyses will also be compared between storms to investigate which FRPSs were most appropriate for the two types of convection and to examine the variation in the LNOx production. The simulated LNOx results from WRF-Chem will also be compared against other previously studied mid-latitude thunderstorms.
NASA Astrophysics Data System (ADS)
Dong, Chuanfei; Winske, Dan; Cowee, Misa; Bougher, Stephen W.; Andersson, Laila; Connerney, Jack; Epley, Jared; Ergun, Robert; McFadden, James P.; Ma, Yingjuan; Toth, Gabor; Curry, Shannon; Nagy, Andrew; Jakosky, Bruce
2015-04-01
Two-dimensional hybrid simulation codes are employed to investigate the kinetic properties of plasmas and waves downstream of the Martian bow shock. The simulations are two-dimensional in space but three dimensional in field and velocity components. Simulations show that ion cyclotron waves are generated by temperature anisotropy resulting from the reflected protons around the Martian bow shock. These proton cyclotron waves could propagate downward into the Martian ionosphere and are expected to heat the O+ layer peaked from 250 to 300 km due to the wave-particle interaction. The proton cyclotron wave heating is anticipated to be a significant source of energy into the thermosphere, which impacts atmospheric escape rates. The simulation results show that the specific dayside heating altitude depends on the Martian crustal field orientations, solar cycles and seasonal variations since both the cyclotron resonance condition and the non/sub-resonant stochastic heating threshold depend on the ambient magnetic field strength. The dayside magnetic field profiles for different crustal field orientation, solar cycle and seasonal variations are adopted from the BATS-R-US Mars multi-fluid MHD model. The simulation results, however, show that the heating of O+ via proton cyclotron wave resonant interaction is not likely in the relatively weak crustal field region, based on our simplified model. This indicates that either the drift motion resulted from the transport of ionospheric O+, or the non/sub-resonant stochastic heating mechanism are important to explain the heating of Martian O+ layer. We will investigate this further by comparing the simulation results with the available MAVEN data. These simulated ion cyclotron waves are important to explain the heating of Martian O+ layer and have significant implications for future observations.
NASA Astrophysics Data System (ADS)
Markevitch, Maxim
' -- sharp, arc-like contact discontinuities often observed in the cluster high- resolution X-ray images. Most of the observed cold fronts are very smooth, but some are visibly affected by instabilities. We will constrain the viscosity (largely independently of its exact physical nature) by including various levels of viscosity in the simulation of a strategically selected sample of cold front clusters. The forthcoming Astro-H mission opens another avenue to study the ICM viscosity and related phenomena -- by directly observing turbulence in merging and relaxed clusters. The turbulence in our merger simulations with varying viscosity could be directly compared to the levels eventually observed by Astro-H. Over the past several years, we have developed most of the machinery necessary for the above simulations by adding the appropriate code for diffusive physics into FLASH -- the high-resolution, grid-based magnetohydrodynamic code. As part of the proposed project, we will (a) add a few missing physical ingredients to the code and (b) simulate a sample of merging clusters, carefully selected from the XMM and Chandra archives to provide the strongest constraints on thermal conduction and viscosity in the ICM. The comparison with observations will result in strict limits on these microphysical quantities, adding an important element into the astrophysical foundation for the use of clusters as cosmological tools. The proposed research is directly relevant to the ROSES ATP solicitation, because it is a theoretical/numerical study of the physical processes in galaxy clusters, which will lead to predictions that can be tested with observations by the NASA space astrophysics missions XMM, Chandra and Astro-H.
The role of historical forcings in simulating the observed Atlantic Multidecadal Oscillation
NASA Astrophysics Data System (ADS)
Goes, L. M.; Cane, M. A.; Bellomo, K.; Clement, A. C.
2016-12-01
The variation in basin-wide North Atlantic sea surface temperatures (SST), known as the Atlantic multidecadal oscillation (AMO), affects climate throughout the Northern Hemisphere and tropics, yet the forcing mechanisms are not fully understood. Here, we analyze the AMO in the Coupled Model Intercomparison Project phase 5 (CMIP5) Pre-industrial (PI) and Historical (HIST) simulations to determine the role of historical climate forcings in producing the observed 20th century shifts in the AMO (OBS, 1865-2005). We evaluate whether the agreement between models and observations is better with historical forcings or without forcing - i.e. due to processes internal to the climate system, such as the Atlantic Meridional Overturning Circulation (AMOC). To do this we draw 141-year samples from 38 CMIP5 PI runs and compare the correlation between the PI and HIST AMO to the observed AMO. We find that in the majority of models (24 out of 38), it is very unlikely (less than 10% chance) that the unforced simulations produce agreement with observations that are as high as the forced simulations. We also compare the amplitude of the simulated AMO and find that 87% of models produce multi-decadal variance in the AMO with historical forcings that is very likely higher than without forcing, but most models underestimate the variance of the observed AMO. This indicates that over the 20th century external rather than internal forcing was crucial in setting the pace, phase and amplitude of the AMO.
The Arctic clouds from model simulations and long-term observations at Barrow, Alaska
NASA Astrophysics Data System (ADS)
Zhao, Ming
The Arctic is a region that is very sensitive to global climate change while also experiencing significant changes in its surface air temperature, sea-ice cover, atmospheric circulation, precipitation, snowfall, biogeochemical cycling, and land surface. Although previous studies have shown that the arctic clouds play an important role in the arctic climate changes, the arctic clouds are poorly understood and simulated in climate model due to limited observations. Furthermore, most of the studies were based on short-term experiments and typically only cover the warm seasons, which do not provide a full understanding of the seasonal cycle of arctic clouds. To address the above concerns and to improve our understanding of arctic clouds, six years of observational and retrieval data from 1999 to 2004 at the Atmospheric Radiation Management (ARM) Climate Research Facility (ACRF) North Slope of Alaska (NSA) Barrow site are used to understand the arctic clouds and related radiative processes. In particular, we focus on the liquid-ice mass partition in the mixed-phase cloud layer. Statistical results show that aerosol type and concentration are important factors that impact the mixed-phase stratus (MPS) cloud microphysical properties: liquid water path (LWP) and liquid water fraction (LWF) decrease with the increase of cloud condensation nuclei (CCN) number concentration; the high dust loading and dust occurrence in the spring are possible reasons for the much lower LWF than the other seasons. The importance of liquid-ice mass partition on surface radiation budgets was analyzed by comparing cloud longwave radiative forcings under the same LWP but different ice water path (IWP) ranges. Results show the ice phase enhance the surface cloud longwave (LW) forcing by 8˜9 W m-2 in the moderately thin MPS. This result provides an observational evidence on the aerosol glaciation effect in the moderately thin MPS, which is largely unknown so far. The above new insights are
A Comparison of Observed and Simulated 1990 – 2010 U.S. Ozone Trends
In this study, we analyze ozone concentrations from long-term (1990 – 2010) WRF-CMAQ simulations driven by year specific meteorology and emissions. These simulations allow us to compare observed and simulated ozone trends in order to evaluate the model’s ability to pr...
NASA Technical Reports Server (NTRS)
Iguchi, Takamichi; Nakajima, Teruyuki; Khain, Alexander P.; Saito, Kazuo; Takemura, Toshihiko; Okamoto, Hajime; Nishizawa, Tomoaki; Tao, Wei-Kuo
2012-01-01
Numerical weather prediction (NWP) simulations using the Japan Meteorological Agency NonhydrostaticModel (JMA-NHM) are conducted for three precipitation events observed by shipborne or spaceborneW-band cloud radars. Spectral bin and single-moment bulk cloud microphysics schemes are employed separatelyfor an intercomparative study. A radar product simulator that is compatible with both microphysicsschemes is developed to enable a direct comparison between simulation and observation with respect to theequivalent radar reflectivity factor Ze, Doppler velocity (DV), and path-integrated attenuation (PIA). Ingeneral, the bin model simulation shows better agreement with the observed data than the bulk modelsimulation. The correction of the terminal fall velocities of snowflakes using those of hail further improves theresult of the bin model simulation. The results indicate that there are substantial uncertainties in the masssizeand sizeterminal fall velocity relations of snowflakes or in the calculation of terminal fall velocity of snowaloft. For the bulk microphysics, the overestimation of Ze is observed as a result of a significant predominanceof snow over cloud ice due to substantial deposition growth directly to snow. The DV comparison shows thata correction for the fall velocity of hydrometeors considering a change of particle size should be introducedeven in single-moment bulk cloud microphysics.
NASA Astrophysics Data System (ADS)
Zhang, Yuzhong; Wang, Yuhang; Crawford, James; Cheng, Ye; Li, Jianfeng
2018-05-01
Obtaining the full spatial coverage of daily surface ozone fields is challenging because of the sparsity of the surface monitoring network and the difficulty in direct satellite retrievals of surface ozone. We propose an indirect satellite retrieval framework to utilize the information from satellite-measured column densities of tropospheric NO2 and CH2O, which are sensitive to the lower troposphere, to derive surface ozone fields. The method is applicable to upcoming geostationary satellites with high-quality NO2 and CH2O measurements. To prove the concept, we conduct a simulation experiment using a 3-D chemical transport model for July 2011 over the eastern US. The results show that a second order regression using both NO2 and CH2O column densities can be an effective predictor for daily maximum 8-h average ozone. Furthermore, this indirect retrieval approach is shown to be complementary to spatial interpolation of surface observations, especially in regions where the surface sites are sparse. Combining column observations of NO2 and CH2O with surface site measurements leads to an improved representation of surface ozone over simple kriging, increasing the R2 value from 0.53 to 0.64 at a surface site distance of 252 km. The improvements are even more significant with larger surface site distances. The simulation experiment suggests that the indirect satellite retrieval technique can potentially be a useful tool to derive the full spatial coverage of daily surface ozone fields if satellite observation uncertainty is moderate.
Simulated observations of young gravitationally unstable protoplanetary discs
NASA Astrophysics Data System (ADS)
Douglas, T. A.; Caselli, P.; Ilee, J. D.; Boley, A. C.; Hartquist, T. W.; Durisen, R. H.; Rawlings, J. M. C.
2013-08-01
The formation and earliest stages of protoplanetary discs remain poorly constrained by observations. Atacama Large Millimetre/sub-millimetre Array (ALMA) will soon revolutionise this field. Therefore, it is important to provide predictions which will be valuable for the interpretation of future high sensitivity and high angular resolution observations. Here, we present simulated ALMA observations based on radiative transfer modelling of a relatively massive (0.39 M⊙) self-gravitating disc embedded in a 10 M⊙ dense core, with structure similar to the pre-stellar core L1544. We focus on simple species and conclude that C17O 3→2, HCO+ 3→2, OCS 26→25 and H2CO 404→303 lines can be used to probe the disc structure and kinematics at all scales.
Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation
NASA Astrophysics Data System (ADS)
Benassai, Guido; Aucelli, Pietro; Budillon, Giorgio; De Stefano, Massimo; Di Luccio, Diana; Di Paola, Gianluigi; Montella, Raffaele; Mucerino, Luigi; Sica, Mario; Pennetta, Micla
2017-09-01
The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including RPAS (remotely piloted aircraft systems) observations, allowed us to detect the presence of rip currents and rip channels at the mouth of Sele River, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment analysis and a set of high-resolution wave numerical simulations, completed with Google EarthTM images and RPAS observations. The grain size trend analysis and the numerical simulations allowed us to identify the rip current occurrence, forced by topographically constrained channels incised on the seabed, which were compared with observations.
Trend estimates of AERONET-observed and model-simulated AOT percentiles between 1993 and 2013
NASA Astrophysics Data System (ADS)
Yoon, Jongmin; Pozzer, Andrea; Chang, Dong Yeong; Lelieveld, Jos
2016-04-01
Recent Aerosol Optical thickness (AOT) trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope±2σ = 0.75 ± 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires.
AOD trends during 2001-2010 from observations and model simulations
NASA Astrophysics Data System (ADS)
Pozzer, Andrea; de Meij, Alexander; Yoon, Jongmin; Astitha, Marina
2016-04-01
The trend of aerosol optical depth (AOD) between 2001 and 2010 is estimated globally and regionally from remote sensed observations by the MODIS (Moderate Resolution Imaging Spectroradiometer), MISR (Multi-angle Imaging SpectroRadiometer) and SeaWIFS (Sea-viewing Wide Field-of-view Sensor) satellite sensor. The resulting trends have been compared to model results from the EMAC (ECHAM5/MESSy Atmospheric Chemistry {[1]}), model. Although interannual variability is applied only to anthropogenic and biomass-burning emissions, the model is able to quantitatively reproduce the AOD trends as observed by MODIS, while some discrepancies are found when compared to MISR and SeaWIFS. An additional numerical simulation with the same model was performed, neglecting any temporal change in the emissions, i.e. with no interannual variability for any emission source. It is shown that decreasing AOD trends over the US and Europe are due to the decrease in the (anthropogenic) emissions. On contrary over the Sahara Desert and the Middle East region, the meteorological/dynamical changes in the last decade play a major role in driving the AOD trends. Further, over Southeast Asia, both meteorology and emissions changes are equally important in defining AOD trends {[2]}. Finally, decomposing the regional AOD trends into individual aerosol components reveals that the soluble components are the most dominant contributors to the total AOD, as their influence on the total AOD is enhanced by the aerosol water content. {[1]}: Jöckel, P., Kerkweg, A., Pozzer, A., Sander, R., Tost, H., Riede, H., Baumgaertner, A., Gromov, S., and Kern, B.: Development cycle 2 of the Modular Earth Submodel System (MESSy2), Geosci. Model Dev., 3, 717-752, doi:10.5194/gmd-3-717-2010, 2010. {[2]}: Pozzer, A., de Meij, A., Yoon, J., Tost, H., Georgoulias, A. K., and Astitha, M.: AOD trends during 2001-2010 from observations and model simulations, Atmos. Chem. Phys., 15, 5521-5535, doi:10.5194/acp-15-5521-2015, 2015.
Congested traffic states in empirical observations and microscopic simulations
NASA Astrophysics Data System (ADS)
Treiber, Martin; Hennecke, Ansgar; Helbing, Dirk
2000-08-01
We present data from several German freeways showing different kinds of congested traffic forming near road inhomogeneities, specifically lane closings, intersections, or uphill gradients. The states are localized or extended, homogeneous or oscillating. Combined states are observed as well, like the coexistence of moving localized clusters and clusters pinned at road inhomogeneities, or regions of oscillating congested traffic upstream of nearly homogeneous congested traffic. The experimental findings are consistent with a recently proposed theoretical phase diagram for traffic near on-ramps [D. Helbing, A. Hennecke, and M. Treiber, Phys. Rev. Lett. 82, 4360 (1999)]. We simulate these situations with a continuous microscopic single-lane model, the ``intelligent driver model,'' using empirical boundary conditions. All observations, including the coexistence of states, are qualitatively reproduced by describing inhomogeneities with local variations of one model parameter. We show that the results of the microscopic model can be understood by formulating the theoretical phase diagram for bottlenecks in a more general way. In particular, a local drop of the road capacity induced by parameter variations has essentially the same effect as an on-ramp.
Arctic sea-ice diffusion from observed and simulated Lagrangian trajectories
NASA Astrophysics Data System (ADS)
Rampal, Pierre; Bouillon, Sylvain; Bergh, Jon; Ólason, Einar
2016-07-01
We characterize sea-ice drift by applying a Lagrangian diffusion analysis to buoy trajectories from the International Arctic Buoy Programme (IABP) dataset and from two different models: the standalone Lagrangian sea-ice model neXtSIM and the Eulerian coupled ice-ocean model used for the TOPAZ reanalysis. By applying the diffusion analysis to the IABP buoy trajectories over the period 1979-2011, we confirm that sea-ice diffusion follows two distinct regimes (ballistic and Brownian) and we provide accurate values for the diffusivity and integral timescale that could be used in Eulerian or Lagrangian passive tracers models to simulate the transport and diffusion of particles moving with the ice. We discuss how these values are linked to the evolution of the fluctuating displacements variance and how this information could be used to define the size of the search area around the position predicted by the mean drift. By comparing observed and simulated sea-ice trajectories for three consecutive winter seasons (2007-2011), we show how the characteristics of the simulated motion may differ from or agree well with observations. This comparison illustrates the usefulness of first applying a diffusion analysis to evaluate the output of modeling systems that include a sea-ice model before using these in, e.g., oil spill trajectory models or, more generally, to simulate the transport of passive tracers in sea ice.
Observed and Simulated Eddy Diffusivity Upstream of the Drake Passage
NASA Astrophysics Data System (ADS)
Tulloch, R.; Ferrari, R. M.; Marshall, J.
2012-12-01
Estimates of eddy diffusivity in the Southern Ocean are poorly constrained due to lack of observations. We compare the first direct estimate of isopycnal eddy diffusivity upstream of the Drake Passage (from Ledwell et al. 2011) with a numerical simulation. The estimate is computed from a point tracer release as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). We find that the observational diffusivity estimate of about 500m^2/s at 1500m depth is close to that computed in a data-constrained, 1/20th of a degree simulation of the Drake Passage region. This tracer estimate also agrees with Lagrangian float calculations in the model. The role of mean flow suppression of eddy diffusivity at shallower depths will also be discussed.
NASA Astrophysics Data System (ADS)
Miller, D. J.; Liu, Z.; Sun, K.; Tao, L.; Nowak, J. B.; Bambha, R.; Michelsen, H. A.; Zondlo, M. A.
2014-12-01
Agricultural ammonia (NH3) emissions are highly uncertain in current bottom-up inventories. Ammonium nitrate is a dominant component of fine aerosols in agricultural regions such as the Central Valley of California, especially during winter. Recent high resolution regional modeling efforts in this region have found significant ammonium nitrate and gas-phase NH3 biases during summer. We compare spatially-resolved surface and boundary layer gas-phase NH3 observations during NASA DISCOVER-AQ California with Community Multi-Scale Air Quality (CMAQ) regional model simulations driven by the EPA NEI 2008 inventory to constrain wintertime NH3 model biases. We evaluate model performance with respect to aerosol partitioning, mixing and deposition to constrain contributions to modeled NH3 concentration biases in the Central Valley Tulare dairy region. Ammonia measurements performed with an open-path mobile platform on a vehicle are gridded to 4 km resolution hourly background concentrations. A peak detection algorithm is applied to remove local feedlot emission peaks. Aircraft NH3, NH4+ and NO3- observations are also compared with simulations extracted along the flight tracks. We find NH3 background concentrations in the dairy region are underestimated by three to five times during winter and NH3 simulations are moderately correlated with observations (r = 0.36). Although model simulations capture NH3 enhancements in the dairy region, these simulations are biased low by 30-60 ppbv NH3. Aerosol NH4+ and NO3- are also biased low in CMAQ by three and four times respectively. Unlike gas-phase NH3, CMAQ simulations do not capture typical NH4+ or NO3- enhancements observed in the dairy region. In contrast, boundary layer height simulations agree well with observations within 13%. We also address observational constraints on simulated NH3 deposition fluxes. These comparisons suggest that NEI 2008 wintertime dairy emissions are underestimated by a factor of three to five. We test
NASA Astrophysics Data System (ADS)
Hamaker, J. P.
2006-09-01
Context: .This is Paper V in a series on polarimetric aperture synthesis based on the algebra of 2×2 matrices. Aims: .It validates the matrix self-calibration theory of the preceding Paper IV and outlines the algorithmic methods that had to be developed for its application. Methods: .New avenues of polarimetric self-calibration opened up in Paper IV are explored by processing a simulated observation. To focus on the polarimetric issues, it is set up so as to sidestep some of the common complications of aperture synthesis, yet properly represent physical conditions. In addition to a representative collection of observing errors, the simulated instrument includes strongly varying Faraday rotation and antennas with unequal feeds. The selfcal procedure is described in detail, including aspects in which it differs from the scalar case, and its effects are demonstrated with a number of intermediate image results. Results: .The simulation's outcome is in full agreement with the theory. The nonlinear matrix equations for instrumental parameters are readily solved by iteration; a convergence problem is easily remedied with a new ancillary algorithm. Instrumental effects are cleanly separated from source properties without reference to changes in parallactic rotation during the observation. Polarimetric images of high purity and dynamic range result. As theory predicts, polarimetric errors that are common to all sources inevitably remain; prior knowledge of the statistics of linear and circular polarization in a typical observed field can be applied to eliminate most of them. Conclusions: .The paper conclusively demonstrates that matrix selfcal per se is a viable method that may foster substantial advancement in the art of radio polarimetry. For its application in real observations, a number of issues must be resolved that matrix selfcal has in common with its scalar sibling, such as the treatment of extended sources and the familiar sampling and aliasing problems. The
Diouf, Ibrahima; Rodriguez-Fonseca, Belen; Deme, Abdoulaye; Caminade, Cyril; Morse, Andrew P.; Cisse, Moustapha; Sy, Ibrahima; Dia, Ibrahima; Ermert, Volker; Ndione, Jacques-André; Gaye, Amadou Thierno
2017-01-01
The analysis of the spatial and temporal variability of climate parameters is crucial to study the impact of climate-sensitive vector-borne diseases such as malaria. The use of malaria models is an alternative way of producing potential malaria historical data for Senegal due to the lack of reliable observations for malaria outbreaks over a long time period. Consequently, here we use the Liverpool Malaria Model (LMM), driven by different climatic datasets, in order to study and validate simulated malaria parameters over Senegal. The findings confirm that the risk of malaria transmission is mainly linked to climate variables such as rainfall and temperature as well as specific landscape characteristics. For the whole of Senegal, a lag of two months is generally observed between the peak of rainfall in August and the maximum number of reported malaria cases in October. The malaria transmission season usually takes place from September to November, corresponding to the second peak of temperature occurring in October. Observed malaria data from the Programme National de Lutte contre le Paludisme (PNLP, National Malaria control Programme in Senegal) and outputs from the meteorological data used in this study were compared. The malaria model outputs present some consistencies with observed malaria dynamics over Senegal, and further allow the exploration of simulations performed with reanalysis data sets over a longer time period. The simulated malaria risk significantly decreased during the 1970s and 1980s over Senegal. This result is consistent with the observed decrease of malaria vectors and malaria cases reported by field entomologists and clinicians in the literature. The main differences between model outputs and observations regard amplitude, but can be related not only to reanalysis deficiencies but also to other environmental and socio-economic factors that are not included in this mechanistic malaria model framework. The present study can be considered as a
Diouf, Ibrahima; Rodriguez-Fonseca, Belen; Deme, Abdoulaye; Caminade, Cyril; Morse, Andrew P; Cisse, Moustapha; Sy, Ibrahima; Dia, Ibrahima; Ermert, Volker; Ndione, Jacques-André; Gaye, Amadou Thierno
2017-09-25
The analysis of the spatial and temporal variability of climate parameters is crucial to study the impact of climate-sensitive vector-borne diseases such as malaria. The use of malaria models is an alternative way of producing potential malaria historical data for Senegal due to the lack of reliable observations for malaria outbreaks over a long time period. Consequently, here we use the Liverpool Malaria Model (LMM), driven by different climatic datasets, in order to study and validate simulated malaria parameters over Senegal. The findings confirm that the risk of malaria transmission is mainly linked to climate variables such as rainfall and temperature as well as specific landscape characteristics. For the whole of Senegal, a lag of two months is generally observed between the peak of rainfall in August and the maximum number of reported malaria cases in October. The malaria transmission season usually takes place from September to November, corresponding to the second peak of temperature occurring in October. Observed malaria data from the Programme National de Lutte contre le Paludisme (PNLP, National Malaria control Programme in Senegal) and outputs from the meteorological data used in this study were compared. The malaria model outputs present some consistencies with observed malaria dynamics over Senegal, and further allow the exploration of simulations performed with reanalysis data sets over a longer time period. The simulated malaria risk significantly decreased during the 1970s and 1980s over Senegal. This result is consistent with the observed decrease of malaria vectors and malaria cases reported by field entomologists and clinicians in the literature. The main differences between model outputs and observations regard amplitude, but can be related not only to reanalysis deficiencies but also to other environmental and socio-economic factors that are not included in this mechanistic malaria model framework. The present study can be considered as a
Exploring the observational constraints on the simulation of brown carbon
NASA Astrophysics Data System (ADS)
Wang, X.; Heald, C. L.; Liu, J.; Weber, R. J.; Campuzano-Jost, P.; Jimenez, J. L.; Schwarz, J. P.; Perring, A. E.
2017-12-01
Brown carbon (BrC) is the component of organic aerosols (OA) which strongly absorbs solar radiation in the near-UV range of the spectrum. However the sources, evolution, and optical properties of BrC remain highly uncertain, and therefore constitute a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. Previous modeling studies of BrC optical properties and DRE have been unable to fully evaluate the skill of their simulations, given the lack of direct measurements of organic aerosol absorption. In this study, we develop a global model simulation (GEOS-Chem) of BrC and test it against BrC absorption measurements from two aircraft campaigns in the U.S. (SEAC4RS and DC3). To our knowledge, this is the first study to compare simulated BrC absorption with direct, continuous ambient measurements. We show that the laboratory-based BrC absorption properties from biomass burning overestimate the aircraft measurements of ambient BrC. In addition, applying a photochemical whitening scheme to simulated BrC is better able to represent the observed BrC absorption. These observations are consistent with a mass absorption coefficient (MAC) of freshly emitted biomass burning OA of 0.57m2g-1. Using the RRTMG model integrated with GEOS-Chem, we estimate that the all-sky top-of-atmosphere direct radiative effect (DRE) of OA is -0.350 Wm-2, 10% higher than that without consideration of BrC absorption. Therefore, our best estimate of the absorption DRE of BrC is +0.042 Wm-2. We suggest that the DRE of BrC has been overestimated previously due to the lack of observational constraints from direct measurements as well as neglect of the effects of photochemical whitening.
NASA Technical Reports Server (NTRS)
Pi, Xiaoqing; Mannucci, Anthony J.; Verkhoglyadova, Olga; Stephens, Philip; Iijima, Bryron A.
2013-01-01
Modeling and imaging the Earth's ionosphere as well as understanding its structures, inhomogeneities, and disturbances is a key part of NASA's Heliophysics Directorate science roadmap. This invention provides a design tool for scientific missions focused on the ionosphere. It is a scientifically important and technologically challenging task to assess the impact of a new observation system quantitatively on our capability of imaging and modeling the ionosphere. This question is often raised whenever a new satellite system is proposed, a new type of data is emerging, or a new modeling technique is developed. The proposed constellation would be part of a new observation system with more low-Earth orbiters tracking more radio occultation signals broadcast by Global Navigation Satellite System (GNSS) than those offered by the current GPS and COSMIC observation system. A simulation system was developed to fulfill this task. The system is composed of a suite of software that combines the Global Assimilative Ionospheric Model (GAIM) including first-principles and empirical ionospheric models, a multiple- dipole geomagnetic field model, data assimilation modules, observation simulator, visualization software, and orbit design, simulation, and optimization software.
Features of the accretion in the EX Hydrae system: Results of numerical simulation
NASA Astrophysics Data System (ADS)
Isakova, P. B.; Zhilkin, A. G.; Bisikalo, D. V.; Semena, A. N.; Revnivtsev, M. G.
2017-07-01
A two-dimensional numerical model in the axisymmetric approximation that describes the flow structure in the magnetosphere of the white dwarf in the EX Hya system has been developed. Results of simulations show that the accretion in EX Hya proceeds via accretion columns, which are not closed and have curtain-like shapes. The thickness of the accretion curtains depends only weakly on the thickness of the accretion disk. This thickness developed in the simulations does not agree with observations. It is concluded that the main reason for the formation of thick accretion curtains in the model is the assumption that the magnetic field penetrates fully into the plasma of the disk. An analysis based on simple estimates shows that a diamagnetic disk that fully or partially shields the magnetic field of the star may be a more attractive explanation for the observed features of the accretion in EX Hya.
Liu, Z; Voelger, P; Sugimoto, N
2000-06-20
We carried out a simulation study for the observation of clouds and aerosols with the Japanese Experimental Lidar in Space Equipment (ELISE), which is a two-wavelength backscatter lidar with three detection channels. The National Space Development Agency of Japan plans to launch the ELISE on the Mission Demonstrate Satellite 2 (MDS-2). In the simulations, the lidar return signals for the ELISE are calculated for an artificial, two-dimensional atmospheric model including different types of clouds and aerosols. The signal detection processes are simulated realistically by inclusion of various sources of noise. The lidar signals that are generated are then used as input for simulations of data analysis with inversion algorithms to investigate retrieval of the optical properties of clouds and aerosols. The results demonstrate that the ELISE can provide global data on the structures and optical properties of clouds and aerosols. We also conducted an analysis of the effects of cloud inhomogeneity on retrievals from averaged lidar profiles. We show that the effects are significant for space lidar observations of optically thick broken clouds.
Presenting simulation results in a nested loop plot.
Rücker, Gerta; Schwarzer, Guido
2014-12-12
Statisticians investigate new methods in simulations to evaluate their properties for future real data applications. Results are often presented in a number of figures, e.g., Trellis plots. We had conducted a simulation study on six statistical methods for estimating the treatment effect in binary outcome meta-analyses, where selection bias (e.g., publication bias) was suspected because of apparent funnel plot asymmetry. We varied five simulation parameters: true treatment effect, extent of selection, event proportion in control group, heterogeneity parameter, and number of studies in meta-analysis. In combination, this yielded a total number of 768 scenarios. To present all results using Trellis plots, 12 figures were needed. Choosing bias as criterion of interest, we present a 'nested loop plot', a diagram type that aims to have all simulation results in one plot. The idea was to bring all scenarios into a lexicographical order and arrange them consecutively on the horizontal axis of a plot, whereas the treatment effect estimate is presented on the vertical axis. The plot illustrates how parameters simultaneously influenced the estimate. It can be combined with a Trellis plot in a so-called hybrid plot. Nested loop plots may also be applied to other criteria such as the variance of estimation. The nested loop plot, similar to a time series graph, summarizes all information about the results of a simulation study with respect to a chosen criterion in one picture and provides a suitable alternative or an addition to Trellis plots.
NASA Astrophysics Data System (ADS)
Battarbee, M.; Guo, J.; Dalla, S.; Wimmer-Schweingruber, R.; Swalwell, B.; Lawrence, D. J.
2018-05-01
Context. The injection, propagation and arrival of solar energetic particles (SEPs) during eruptive solar events is an important and current research topic of heliospheric physics. During the largest solar events, particles may have energies up to a few GeVs and sometimes even trigger ground-level enhancements (GLEs) at Earth. These large SEP events are best investigated through multi-spacecraft observations. Aims: We aim to study the first GLE-event of solar cycle 24, from 17th May 2012, using data from multiple spacecraft (SOHO, GOES, MSL, STEREO-A, STEREO-B and MESSENGER). These spacecraft are located throughout the inner heliosphere, at heliocentric distances between 0.34 and 1.5 astronomical units (au), covering nearly the whole range of heliospheric longitudes. Methods: We present and investigate sub-GeV proton time profiles for the event at several energy channels, obtained via different instruments aboard the above spacecraft. We investigated issues caused by magnetic connectivity, and present results of three-dimensional SEP propagation simulations. We gathered virtual time profiles and perform qualitative and quantitative comparisons with observations, assessed longitudinal injection and transport effects as well as peak intensities. Results: We distinguish different time profile shapes for well-connected and weakly connected observers, and find our onset time analysis to agree with this distinction. At select observers, we identify an additional low-energy component of Energetic Storm Particles (ESPs). Using well-connected observers for normalisation, our simulations are able to accurately recreate both time profile shapes and peak intensities at multiple observer locations. Conclusions: This synergetic approach combining numerical modelling with multi-spacecraft observations is crucial for understanding the propagation of SEPs within the interplanetary magnetic field. Our novel analysis provides valuable proof of the ability to simulate SEP propagation
NASA Technical Reports Server (NTRS)
McCarty, Will
2011-01-01
With the launch of the European Space Agency's Aeolus Mission in 2013, direct spaceborne measurements of vertical wind profiles are imminent via Doppler wind lidar technology. Part of the preparedness for such missions is the development of the proper data assimilation methodology for handling such observations. Since no heritage measurements exist in space, the Joint Observing System Simulation Experiment (Joint OSSE) framework has been utilized to generate a realistic proxy dataset as a precursor to flight. These data are being used for the development of the Gridpoint Statistical Interpolation (GSI) data assimilation system utilized at a number of centers through the United States including the Global Modeling and Assimilation Office (GMAO) at NASA/Goddard Space Flight Center and at the National Centers for Environmental Prediction (NOAA/NWS/NCEP) as an activity through the Joint Center for Satellite Data Assimilation. An update of this ongoing effort will be presented, including the methodology of proxy data generation, the limitations of the proxy data, the handling of line-of-sight wind measurements within the GSI, and the impact on both analyses and forecasts with the addition of the new data type.
NASA Astrophysics Data System (ADS)
McGibbon, J.; Bretherton, C. S.
2017-06-01
During the Marine ARM GPCI Investigation of Clouds (MAGIC) in October 2011 to September 2012, a container ship making periodic cruises between Los Angeles, CA, and Honolulu, HI, was instrumented with surface meteorological, aerosol and radiation instruments, a cloud radar and ceilometer, and radiosondes. Here large-eddy simulation (LES) is performed in a ship-following frame of reference for 13 four day transects from the MAGIC field campaign. The goal is to assess if LES can skillfully simulate the broad range of observed cloud characteristics and boundary layer structure across the subtropical stratocumulus to cumulus transition region sampled during different seasons and meteorological conditions. Results from Leg 15A, which sampled a particularly well-defined stratocumulus to cumulus transition, demonstrate the approach. The LES reproduces the observed timing of decoupling and transition from stratocumulus to cumulus and matches the observed evolution of boundary layer structure, cloud fraction, liquid water path, and precipitation statistics remarkably well. Considering the simulations of all 13 cruises, the LES skillfully simulates the mean diurnal variation of key measured quantities, including liquid water path (LWP), cloud fraction, measures of decoupling, and cloud radar-derived precipitation. The daily mean quantities are well represented, and daily mean LWP and cloud fraction show the expected correlation with estimated inversion strength. There is a -0.6 K low bias in LES near-surface air temperature that results in a high bias of 5.6 W m-2 in sensible heat flux (SHF). Overall, these results build confidence in the ability of LES to represent the northeast Pacific stratocumulus to trade cumulus transition region.
NASA Astrophysics Data System (ADS)
D'Alessandro, J.; Diao, M.; Chen, M.
2015-12-01
John D'Alessandro1, Minghui Diao1, Ming Chen2, George Bryan2, Hugh Morrison21. Department of Meteorology and Climate Science, San Jose State University2. Mesoscale & Microscale Meteorology Division, National Center for Atmospheric Research, Boulder, CO, 80301 Ice crystal formation requires the prerequisite condition of ice supersaturation, i.e., relative humidity with respect to ice (RHi) greater than 100%. The formation and evolution of ice supersaturated regions (ISSRs) has large impact on the subsequent formation of ice clouds. To examine the characteristics of simulated ice supersaturated regions at various model spatial resolutions, case studies between airborne in-situ measurements in the NSF Deep Convective, Clouds and Chemistry (DC3) campaign (May - June 2012) and WRF simulations are conducted in this work. Recent studies using ~200 m in-situ observations showed that ice supersaturated regions are mostly around 1 km in horizontal scale (Diao et al. 2014). Yet it is still unclear if such observed characteristics can be represented by WRF simulations at various spatial resolutions. In this work, we compare the WRF simulated anvil cirrus spatial characteristics with those observed in the DC3 campaign over the southern great plains in US. The WRF model is run at 1 km and 3 km horizontal grid spacing with a recent update of Thompson microphysics scheme. Our comparisons focus on the spatial characteristics of ISSRs and cirrus clouds, including the distributions of their horizontal scales, the maximum relative humidity with respect to ice (RHi) and the relationship between RHi and temperature. Our previous work on the NCAR CM1 cloud-resolving model shows that the higher resolution runs (i.e., 250m and 1km) generally have better agreement with observations than the coarser resolution (4km) runs. We will examine if similar trend exists for WRF simulations in deep convection cases. In addition, we will compare the simulation results between WRF and CM1, particularly
First results from the IllustrisTNG simulations: the galaxy colour bimodality
NASA Astrophysics Data System (ADS)
Nelson, Dylan; Pillepich, Annalisa; Springel, Volker; Weinberger, Rainer; Hernquist, Lars; Pakmor, Rüdiger; Genel, Shy; Torrey, Paul; Vogelsberger, Mark; Kauffmann, Guinevere; Marinacci, Federico; Naiman, Jill
2018-03-01
We introduce the first two simulations of the IllustrisTNG project, a next generation of cosmological magnetohydrodynamical simulations, focusing on the optical colours of galaxies. We explore TNG100, a rerun of the original Illustris box, and TNG300, which includes 2 × 25003 resolution elements in a volume 20 times larger. Here, we present first results on the galaxy colour bimodality at low redshift. Accounting for the attenuation of stellar light by dust, we compare the simulated (g - r) colours of 109 < M⋆/M⊙ < 1012.5 galaxies to the observed distribution from the Sloan Digital Sky Survey. We find a striking improvement with respect to the original Illustris simulation, as well as excellent quantitative agreement with the observations, with a sharp transition in median colour from blue to red at a characteristic M⋆ ˜ 1010.5 M⊙. Investigating the build-up of the colour-mass plane and the formation of the red sequence, we demonstrate that the primary driver of galaxy colour transition is supermassive black hole feedback in its low accretion state. Across the entire population the median colour transition time-scale Δtgreen is ˜1.6 Gyr, a value which drops for increasingly massive galaxies. We find signatures of the physical process of quenching: at fixed stellar mass, redder galaxies have lower star formation rates, gas fractions, and gas metallicities; their stellar populations are also older and their large-scale interstellar magnetic fields weaker than in bluer galaxies. Finally, we measure the amount of stellar mass growth on the red sequence. Galaxies with M⋆ > 1011 M⊙ which redden at z < 1 accumulate on average ˜25 per cent of their final z = 0 mass post-reddening; at the same time, ˜18 per cent of such massive galaxies acquire half or more of their final stellar mass while on the red sequence.
Water vapour tomography using GPS phase observations: Results from the ESCOMPTE experiment
NASA Astrophysics Data System (ADS)
Nilsson, T.; Gradinarsky, L.; Elgered, G.
2007-10-01
Global Positioning System (GPS) tomography is a technique for estimating the 3-D structure of the atmospheric water vapour using data from a dense local network of GPS receivers. Several current methods utilize estimates of slant wet delays between the GPS satellites and the receivers on the ground, which are difficult to obtain with millimetre accuracy from the GPS observations. We present results of applying a new tomographic method to GPS data from the Expériance sur site pour contraindre les modèles de pollution atmosphérique et de transport d'emissions (ESCOMPTE) experiment in southern France. This method does not rely on any slant wet delay estimates, instead it uses the GPS phase observations directly. We show that the estimated wet refractivity profiles estimated by this method is on the same accuracy level or better compared to other tomographic methods. The results are in agreement with earlier simulations, for example the profile information is limited above 4 km.
NASA Technical Reports Server (NTRS)
Prasad, N.; Yeh, Hwa-Young M.; Adler, Robert F.; Tao, Wei-Kuo
1995-01-01
A three-dimensional cloud model, radiative transfer model-based simulation system is tested and validated against the aircraft-based radiance observations of an intense convective system in southeastern Virginia on 29 June 1986 during the Cooperative Huntsville Meteorological Experiment. NASA's ER-2, a high-altitude research aircraft with a complement of radiometers operating at 11-micrometer infrared channel and 18-, 37-, 92-, and 183-GHz microwave channels provided data for this study. The cloud model successfully simulated the cloud system with regard to aircraft- and radar-observed cloud-top heights and diameters and with regard to radar-observed reflectivity structure. For the simulation time found to correspond best with the aircraft- and radar-observed structure, brightness temperatures T(sub b) are simulated and compared with observations for all the microwave frequencies along with the 11-micrometer infrared channel. Radiance calculations at the various frequencies correspond well with the aircraft observations in the areas of deep convection. The clustering of 37-147-GHz T(sub b) observations and the isolation of the 18-GHz values over the convective cores are well simulated by the model. The radiative transfer model, in general, is able to simulate the observations reasonably well from 18 GHz through 174 GHz within all convective areas of the cloud system. When the aircraft-observed 18- and 37-GHz, and 90- and 174-GHz T(sub b) are plotted against each other, the relationships have a gradual difference in the slope due to the differences in the ice particle size in the convective and more stratiform areas of the cloud. The model is able to capture these differences observed by the aircraft. Brightness temperature-rain rate relationships compare reasonably well with the aircraft observations in terms of the slope of the relationship. The model calculations are also extended to select high-frequency channels at 220, 340, and 400 GHz to simulate the
SIM_ADJUST -- A computer code that adjusts simulated equivalents for observations or predictions
Poeter, Eileen P.; Hill, Mary C.
2008-01-01
This report documents the SIM_ADJUST computer code. SIM_ADJUST surmounts an obstacle that is sometimes encountered when using universal model analysis computer codes such as UCODE_2005 (Poeter and others, 2005), PEST (Doherty, 2004), and OSTRICH (Matott, 2005; Fredrick and others (2007). These codes often read simulated equivalents from a list in a file produced by a process model such as MODFLOW that represents a system of interest. At times values needed by the universal code are missing or assigned default values because the process model could not produce a useful solution. SIM_ADJUST can be used to (1) read a file that lists expected observation or prediction names and possible alternatives for the simulated values; (2) read a file produced by a process model that contains space or tab delimited columns, including a column of simulated values and a column of related observation or prediction names; (3) identify observations or predictions that have been omitted or assigned a default value by the process model; and (4) produce an adjusted file that contains a column of simulated values and a column of associated observation or prediction names. The user may provide alternatives that are constant values or that are alternative simulated values. The user may also provide a sequence of alternatives. For example, the heads from a series of cells may be specified to ensure that a meaningful value is available to compare with an observation located in a cell that may become dry. SIM_ADJUST is constructed using modules from the JUPITER API, and is intended for use on any computer operating system. SIM_ADJUST consists of algorithms programmed in Fortran90, which efficiently performs numerical calculations.
NASA Technical Reports Server (NTRS)
Halem, M.; Shukla, J.; Mintz, Y.; Wu, M. L.; Godbole, R.; Herman, G.; Sud, Y.
1979-01-01
Results are presented from numerical simulations performed with the general circulation model (GCM) for winter and summer. The monthly mean simulated fields for each integration are compared with observed geographical distributions and zonal averages. In general, the simulated sea level pressure and upper level geopotential height field agree well with the observations. Well simulated features are the winter Aleutian and Icelandic lows, the summer southwestern U.S. low, the summer and winter oceanic subtropical highs in both hemispheres, and the summer upper level Tibetan high and Atlantic ridge. The surface and upper air wind fields in the low latitudes are in good agreement with the observations. The geographical distirbutions of the Earth-atmosphere radiation balance and of the precipitation rates over the oceans are well simulated, but not all of the intensities of these features are correct. Other comparisons are shown for precipitation along the ITCZ, rediation balance, zonally averaged temperatures and zonal winds, and poleward transports of momentum and sensible heat.
NASA Astrophysics Data System (ADS)
Aklan, Bassim; Hartmann, Josefin; Zink, Diana; Siavooshhaghighi, Hadi; Merten, Ricarda; Putz, Florian; Ott, Oliver; Fietkau, Rainer; Bert, Christoph
2017-06-01
The aim of this study was to systematically investigate the influence of the inter- and intra-observer segmentation variation of tumors and organs at risk on the simulated temperature coverage of the target. CT scans of six patients with tumors in the pelvic region acquired for radiotherapy treatment planning were used for hyperthermia treatment planning. To study the effect of inter-observer variation, three observers manually segmented in the CT images of each patient the following structures: fat, muscle, bone and the bladder. The gross tumor volumes (GTV) were contoured by three radiation oncology residents and used as the hyperthermia target volumes. For intra-observer variation, one of the observers of each group contoured the structures of each patient three times with a time span of one week between the segmentations. Moreover, the impact of segmentation variations in organs at risk (OARs) between the three inter-observers was investigated on simulated temperature distributions using only one GTV. The spatial overlap between individual segmentations was assessed by the Dice similarity coefficient (DSC) and the mean surface distance (MSD). Additionally, the temperatures T90/T10 delivered to 90%/10% of the GTV, respectively, were assessed for each observer combination. The results of the segmentation similarity evaluation showed that the DSC of the inter-observer variation of fat, muscle, the bladder, bone and the target was 0.68 ± 0.12, 0.88 ± 0.05, 0.73 ± 0.14, 0.91 ± 0.04 and 0.64 ± 0.11, respectively. Similar results were found for the intra-observer variation. The MSD results were similar to the DSCs for both observer variations. A statistically significant difference (p < 0.05) was found for T90 and T10 in the predicted target temperature due to the observer variability. The conclusion is that intra- and inter-observer variations have a significant impact on the temperature coverage of the
Observing and Simulating Diapycnal Mixing in the Canadian Arctic Archipelago
NASA Astrophysics Data System (ADS)
Hughes, K.; Klymak, J. M.; Hu, X.; Myers, P. G.; Williams, W. J.; Melling, H.
2016-12-01
High-spatial-resolution observations in the central Canadian Arctic Archipelago are analysed in conjunction with process-oriented modelling to estimate the flow pathways among the constricted waterways, understand the nature of the hydraulic control(s), and assess the influence of smaller scale (metres to kilometres) phenomena such as internal waves and topographically induced eddies. The observations repeatedly display isopycnal displacements of 50 m as dense water plunges over a sill. Depth-averaged turbulent dissipation rates near the sill estimated from these observations are typically 10-6-10-5 W kg-1, a range that is three orders of magnitude larger than that for the open ocean. These and other estimates are compared against a 1/12° basin-scale model from which we estimate diapycnal mixing rates using a volume-integrated advection-diffusion equation. Much of the mixing in this simulation is concentrated near constrictions within Barrow Strait and Queens Channel, the latter being our observational site. This suggests the model is capable of capturing topographically induced mixing. However, such mixing is expected to be enhanced in the presence of tides, a process not included in our basin scale simulation or other similar models. Quantifying this enhancement is another objective of our process-oriented modelling.
NASA Astrophysics Data System (ADS)
Rakesh, V.; Kantharao, B.
2017-03-01
Data assimilation is considered as one of the effective tools for improving forecast skill of mesoscale models. However, for optimum utilization and effective assimilation of observations, many factors need to be taken into account while designing data assimilation methodology. One of the critical components that determines the amount and propagation observation information into the analysis, is model background error statistics (BES). The objective of this study is to quantify how BES in data assimilation impacts on simulation of heavy rainfall events over a southern state in India, Karnataka. Simulations of 40 heavy rainfall events were carried out using Weather Research and Forecasting Model with and without data assimilation. The assimilation experiments were conducted using global and regional BES while the experiment with no assimilation was used as the baseline for assessing the impact of data assimilation. The simulated rainfall is verified against high-resolution rain-gage observations over Karnataka. Statistical evaluation using several accuracy and skill measures shows that data assimilation has improved the heavy rainfall simulation. Our results showed that the experiment using regional BES outperformed the one which used global BES. Critical thermo-dynamic variables conducive for heavy rainfall like convective available potential energy simulated using regional BES is more realistic compared to global BES. It is pointed out that these results have important practical implications in design of forecast platforms while decision-making during extreme weather events
Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; ...
2015-09-22
Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less
Stratospheric Temperature Changes: Observations and Model Simulations
NASA Technical Reports Server (NTRS)
Ramaswamy, V.; Chanin, M.-L.; Angell, J.; Barnett, J.; Gaffen, D.; Gelman, M.; Keckhut, P.; Koshelkov, Y.; Labitzke, K.; Lin, J.-J. R.
1999-01-01
This paper reviews observations of stratospheric temperatures that have been made over a period of several decades. Those observed temperatures have been used to assess variations and trends in stratospheric temperatures. A wide range of observation datasets have been used, comprising measurements by radiosonde (1940s to the present), satellite (1979 - present), lidar (1979 - present) and rocketsonde (periods varying with location, but most terminating by about the mid-1990s). In addition, trends have also been assessed from meteorological analyses, based on radiosonde and/or satellite data, and products based on assimilating observations into a general circulation model. Radiosonde and satellite data indicate a cooling trend of the annual-mean lower stratosphere since about 1980. Over the period 1979-1994, the trend is 0.6K/decade. For the period prior to 1980, the radiosonde data exhibit a substantially weaker long-term cooling trend. In the northern hemisphere, the cooling trend is about 0.75K/decade in the lower stratosphere, with a reduction in the cooling in mid-stratosphere (near 35 km), and increased cooling in the upper stratosphere (approximately 2 K per decade at 50 km). Model simulations indicate that the depletion of lower stratospheric ozone is the dominant factor in the observed lower stratospheric cooling. In the middle and upper stratosphere both the well-mixed greenhouse gases (such as CO) and ozone changes contribute in an important manner to the cooling.
High Fidelity Thermal Simulators for Non-Nuclear Testing: Analysis and Initial Results
NASA Technical Reports Server (NTRS)
Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David
2007-01-01
Non-nuclear testing can be a valuable tool in the development of a space nuclear power system, providing system characterization data and allowing one to work through various fabrication, assembly and integration issues without the cost and time associated with a full ground nuclear test. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Testing with non-optimized heater elements allows one to assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. High fidelity thermal simulators that match both the static and the dynamic fuel pin performance that would be observed in an operating, fueled nuclear reactor can vastly increase the value of non-nuclear test results. With optimized simulators, the integration of thermal hydraulic hardware tests with simulated neutronie response provides a bridge between electrically heated testing and fueled nuclear testing, providing a better assessment of system integration issues, characterization of integrated system response times and response characteristics, and assessment of potential design improvements' at a relatively small fiscal investment. Initial conceptual thermal simulator designs are determined by simple one-dimensional analysis at a single axial location and at steady state conditions; feasible concepts are then input into a detailed three-dimensional model for comparison to expected fuel pin performance. Static and dynamic fuel pin performance for a proposed reactor design is determined using SINDA/FLUINT thermal analysis software, and comparison is made between the expected nuclear performance and the performance of conceptual thermal simulator designs. Through a series of iterative analyses, a conceptual high fidelity design can developed. Test results presented in this paper correspond to a "first cut" simulator design for a potential
Observations and simulations of microplastic marine debris in the ocean surface boundary layer
NASA Astrophysics Data System (ADS)
Kukulka, T.; Brunner, K.; Proskurowski, G. K.; Lavender Law, K. L.
2016-02-01
Motivated by observations of buoyant microplastic marine debris (MPMD) in the ocean surface boundary layer (OSBL), this study applies a large eddy simulation model and a parametric one-dimensional column model to examine vertical distributions of MPMD. MPMD is widely distributed in vast regions of the subtropical gyres and has emerged as a major open ocean pollutant whose distribution is subject to upper ocean turbulence. The models capture wind-driven turbulence, Langmuir turbulence (LT), and enhanced turbulent kinetic energy input due to breaking waves (BW). Model results are only consistent with MPMD observations if LT effects are included. Neither BW nor shear-driven turbulence is capable of deeply submerging MPMD, suggesting that the observed vertical MPMD distributions are a characteristic signature of wave-driven LT. Thus, this study demonstrates that LT substantially increases turbulent transport in the OSBL, resulting in deep submergence of buoyant tracers. The parametric model is applied to eleven years of observations in the North Atlantic and North Pacific subtropical gyres to show that surface measurements substantially underestimate MPMD concentrations by a factor of three to thirteen.
Study on observation planning of LAMOST focal plane positioning system and its simulation
NASA Astrophysics Data System (ADS)
Zhai, Chao; Jin, Yi; Peng, Xiaobo; Xing, Xiaozheng
2006-06-01
Fiber Positioning System of LAMOST focal plane based on subarea thinking, adopts a parallel controllable positioning plan, the structure is designed as a round area and overlapped each other in order to eliminate the un-observation region. But it also makes the observation efficiency of the system become an important problem. In this paper According to the system, the model of LAMOST focal plane Observation Planning including 4000 fiber positioning units is built, Stars are allocated using netflow algorithm and mechanical collisions are diminished through the retreat algorithm, then the simulation of the system's observation efficiency is carried out. The problem of observation efficiency of LAMOST focal plane is analysed systemic and all-sided from the aspect of overlapped region, fiber positioning units, observation radius, collisions and so on. The observation efficiency of the system in theory is describes and the simulation indicates that the system's observation efficiency is acceptable. The analyses play an indicative role on the design of the LAMOST focal plane structure.
Nurse students learning acute care by simulation - Focus on observation and debriefing.
Abelsson, Anna; Bisholt, Birgitta
2017-05-01
Simulation creates the possibility to experience acute situations during nursing education which cannot easily be achieved in clinical settings. To describe how nursing students learn acute care of patients through simulation exercises, based on observation and debriefing. The study was designed as an observational study inspired by an ethnographic approach. Data was collected through observations and interviews. Data was analyzed using an interpretive qualitative content analysis. Nursing students created space for reflection when needed. There was a positive learning situation when suitable patient scenarios were presented. Observations and discussions with peers gave the students opportunities to identify their own need for knowledge, while also identifying existing knowledge. Reflections could confirm or reject their preparedness for clinical practice. The importance of working in a structured manner in acute care situations became apparent. However, negative feedback to peers was avoided, which led to a loss of learning opportunity. High fidelity simulation training as a method plays an important part in the nursing students' learning. The teacher also plays a key role by asking difficult questions and guiding students towards accurate knowledge. This makes it possible for the students to close knowledge gaps, leading to improved patient safety. Copyright © 2017 Elsevier Ltd. All rights reserved.
A system for simulating aerial or orbital TV observations of geographic patterns
NASA Technical Reports Server (NTRS)
Latham, J. P.
1972-01-01
A system which simulates observation of the earth surface by aerial or orbiting television devices has been developed. By projecting color slides of photographs taken by aircraft and orbiting sensors upon a rear screen system, and altering scale of projected image, screen position, or TV camera position, it is possible to simulate alternatives of altitude, or optical systems. By altering scan line patterns in COHU 3200 series camera from 525 to 945 scan lines, it is possible to study implications of scan line resolution upon the detection and analysis of geographic patterns observed by orbiting TV systems.
Interannual Rainfall Variability in North-East Brazil: Observation and Model Simulation
NASA Astrophysics Data System (ADS)
Harzallah, A.; Rocha de Aragão, J. O.; Sadourny, R.
1996-08-01
The relationship between interannual variability of rainfall in north-east Brazil and tropical sea-surface temperature is studied using observations and model simulations. The simulated precipitation is the average of seven independent realizations performed using the Laboratoire de Météorologie Dynamique atmospheric general model forced by the 1970-1988 observed sea-surface temperature. The model reproduces very well the rainfall anomalies (correlation of 091 between observed and modelled anomalies). The study confirms that precipitation in north-east Brazil is highly correlated to the sea-surface temperature in the tropical Atlantic and Pacific oceans. Using the singular value decomposition method, we find that Nordeste rainfall is modulated by two independent oscillations, both governed by the Atlantic dipole, but one involving only the Pacific, the other one having a period of about 10 years. Correlations between precipitation in north-east Brazil during February-May and the sea-surface temperature 6 months earlier indicate that both modes are essential to estimate the quality of the rainy season.
NASA Technical Reports Server (NTRS)
Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Zhang, Chidong; Jeong, Myeong Jae; Gautam, Ritesh; Bettenhausen, Corey; Sayer, Andrew M.; Hansell, Richard A.; Liu, Xiaohong;
2012-01-01
One of the seven scientific areas of interests of the 7-SEAS field campaign is to evaluate the impact of aerosol on cloud and precipitation (http://7-seas.gsfc.nasa.gov). However, large-scale covariability between aerosol, cloud and precipitation is complicated not only by ambient environment and a variety of aerosol effects, but also by effects from rain washout and climate factors. This study characterizes large-scale aerosol-cloud-precipitation covariability through synergy of long-term multi ]sensor satellite observations with model simulations over the 7-SEAS region [10S-30N, 95E-130E]. Results show that climate factors such as ENSO significantly modulate aerosol and precipitation over the region simultaneously. After removal of climate factor effects, aerosol and precipitation are significantly anti-correlated over the southern part of the region, where high aerosols loading is associated with overall reduced total precipitation with intensified rain rates and decreased rain frequency, decreased tropospheric latent heating, suppressed cloud top height and increased outgoing longwave radiation, enhanced clear-sky shortwave TOA flux but reduced all-sky shortwave TOA flux in deep convective regimes; but such covariability becomes less notable over the northern counterpart of the region where low ]level stratus are found. Using CO as a proxy of biomass burning aerosols to minimize the washout effect, large-scale covariability between CO and precipitation was also investigated and similar large-scale covariability observed. Model simulations with NCAR CAM5 were found to show similar effects to observations in the spatio-temporal patterns. Results from both observations and simulations are valuable for improving our understanding of this region's meteorological system and the roles of aerosol within it. Key words: aerosol; precipitation; large-scale covariability; aerosol effects; washout; climate factors; 7- SEAS; CO; CAM5
Observation of the pressure effect in simulations of droplets splashing on a dry surface
NASA Astrophysics Data System (ADS)
Boelens, A. M. P.; Latka, A.; de Pablo, J. J.
2018-06-01
At atmospheric pressure, a drop of ethanol impacting on a solid surface produces a splash. Reducing the ambient pressure below its atmospheric value suppresses this splash. The origin of this so-called pressure effect is not well understood, and this study presents an in-depth comparison between various theoretical models that aim to predict splashing and simulations. In this paper, the pressure effect is explored numerically by resolving the Navier-Stokes equations at a 3-nm resolution. In addition to reproducing numerous experimental observations, it is found that different models all provide elements of what is observed in the simulations. The skating droplet model correctly predicts the existence and scaling of a gas film under the droplet, the lamella formation theory is able to correctly predict the scaling of the lamella ejection velocity as a function of the impact velocity for liquids with different viscosity, and lastly, the dewetting theory's hypothesis of a lift force acting on the liquid sheet after ejection is consistent with our results.
Improving the result of forcasting using reservoir and surface network simulation
NASA Astrophysics Data System (ADS)
Hendri, R. S.; Winarta, J.
2018-01-01
This study was aimed to get more representative results in production forcasting using integrated simulation in pipeline gathering system of X field. There are 5 main scenarios which consist of the production forecast of the existing condition, work over, and infill drilling. Then, it’s determined the best development scenario. The methods of this study is Integrated Reservoir Simulator and Pipeline Simulator so-calle as Integrated Reservoir and Surface Network Simulation. After well data result from reservoir simulator was then integrated with pipeline networking simulator’s to construct a new schedule, which was input for all simulation procedure. The well design result was done by well modeling simulator then exported into pipeline simulator. Reservoir prediction depends on the minimum value of Tubing Head Pressure (THP) for each well, where the pressure drop on the Gathering Network is not necessary calculated. The same scenario was done also for the single-reservoir simulation. Integration Simulation produces results approaching the actual condition of the reservoir and was confirmed by the THP profile, which difference between those two methods. The difference between integrated simulation compared to single-modeling simulation is 6-9%. The aimed of solving back-pressure problem in pipeline gathering system of X field is achieved.
NREL: News - Solar Decathlon Design Presentation and Simulation Results
Announced Design Presentation and Simulation Results Announced Monday, September 30, 2002 took first place in the Design Presentation and Simulation Contest at the Solar Village on the National Tech in third. Design Presentation and Simulation is one of ten contests in the Solar Decathlon, which
LENS: μLENS Simulations, Analysis, and Results
NASA Astrophysics Data System (ADS)
Rasco, Charles
2013-04-01
Simulations of the Low-Energy Neutrino Spectrometer prototype, μLENS, have been performed in order to benchmark the first measurements of the μLENS detector at the Kimballton Underground Research Facility (KURF). μLENS is a 6x6x6 celled scintillation lattice filled with Linear Alkylbenzene based scintillator. We have performed simulations of μLENS using the GEANT4 toolkit. We have measured various radioactive sources, LEDs, and environmental background radiation measurements at KURF using up to 96 PMTs with a simplified data acquisition system of QDCs and TDCs. In this talk we will demonstrate our understanding of the light propagation and we will compare simulation results with measurements of the μLENS detector of various radioactive sources, LEDs, and the environmental background radiation.
NASA Technical Reports Server (NTRS)
Yau, A. W.; Whalen, B. A.; Harris, F. R.; Gattinger, R. L.; Pongratz, M. B.
1985-01-01
Observations of plasma depletion, ion composition modification, and airglow emissions in the Waterhole experiments are presented. The detailed ion chemistry and airglow emission processes related to the ionospheric hole formation in the experiment are examined, and observations are compared with computer simulation results. The latter indicate that the overall depletion rates in different parts of the depletion region are governed by different parameters.
Hyper-X Stage Separation: Simulation Development and Results
NASA Technical Reports Server (NTRS)
Reubush, David E.; Martin, John G.; Robinson, Jeffrey S.; Bose, David M.; Strovers, Brian K.
2001-01-01
This paper provides an overview of stage separation simulation development and results for NASA's Hyper-X program; a focused hypersonic technology effort designed to move hypersonic, airbreathing vehicle technology from the laboratory environment to the flight environment. This paper presents an account of the development of the current 14 degree of freedom stage separation simulation tool (SepSim) and results from use of the tool in a Monte Carlo analysis to evaluate the risk of failure for the separation event. Results from use of the tool show that there is only a very small risk of failure in the separation event.
NASA Astrophysics Data System (ADS)
Berchem, J.; Marchaudon, A.; Bosqued, J.; Escoubet, C. P.; Dunlop, M.; Owen, C. J.; Reme, H.; Balogh, A.; Carr, C.; Fazakerley, A. N.; Cao, J. B.
2005-12-01
Synoptic measurements from the DOUBLE STAR and CLUSTER spacecraft offer a unique opportunity to evaluate global models in simulating the complex topology and dynamics of the dayside merging region. We compare observations from the DOUBLE STAR TC-1 and CLUSTER spacecraft on May 8, 2004 with the predictions from a three-dimensional magnetohydrodynamic (MHD) simulation that uses plasma and magnetic field parameters measured upstream of the bow shock by the WIND spacecraft. Results from the global simulation are consistent with the large-scale features observed by CLUSTER and TC-1. We discuss topological changes and plasma flows at the dayside magnetospheric boundary inferred from the simulation results. The simulation shows that the DOUBLE STAR spacecraft passed through the dawn side merging region as the IMF rotated. In particular, the simulation indicates that at times TC-1 was very close to the merging region. In addition, we found that the bifurcation of the merging region in the simulation results is consistent with predictions by the antiparallel merging model. However, because of the draping of the magnetosheath field lines over the magnetopause, the positions and shape of the merging region differ significantly from those predicted by the model.
NASA Astrophysics Data System (ADS)
Buzulukova, N.; Dorelli, J.; Glocer, A.
2017-12-01
We present the results of global high resolution resistive magnetohydrodynamics (MHD BATS-R-US) simulations of Earth's magnetosphere. We extract location of magnetic separators with RECONX tool and compare the results with observations from the Magnetospheric Multiscale (MMS). A few cases are analysed including a southward IMF magnetopause crossing during October 16, 2015 that was previously identified as an electron diffusion region (EDR) event. The simulation predicts a complex time-dependent magnetic topology consisting of multiple separators and flux ropes. Despite the topological complexity, the predicted distance between MMS and the primary separator is less than 0.5 Earth radii. The simulation shows that the existence of IMF Bx results in a duskward shift of the location of the topological separator. The results are explained by a combined effect of solar wind draping and pile-up effect that modify the current density across the magnetopause and affect the location of the separator. The RECONX tool also is used to extract the separator location in the geomagnetic tail, and relate transient tail structures (bursty bulk flows) to the location of separator. These results suggest that global magnetic topology, rather than local magnetic geometry alone, determines the location of the separator reconnection both at the dayside magnetopause and in the tail. We show that the resistive MHD model helps to understand the global context of local MMS observations.
Simulated cosmic microwave background maps at 0.5 deg resolution: Basic results
NASA Technical Reports Server (NTRS)
Hinshaw, G.; Bennett, C. L.; Kogut, A.
1995-01-01
We have simulated full-sky maps of the cosmic microwave background (CMB) anisotropy expected from cold dark matter (CDM) models at 0.5 deg and 1.0 deg angular resolution. Statistical properties of the maps are presented as a function of sky coverage, angular resolution, and instrument noise, and the implications of these results for observability of the Doppler peak are discussed. The rms fluctuations in a map are not a particularly robust probe of the existence of a Doppler peak; however, a full correlation analysis can provide reasonable sensitivity. We find that sensitivity to the Doppler peak depends primarily on the fraction of sky covered, and only secondarily on the angular resolution and noise level. Color plates of the simulated maps are presented to illustrate the anisotropies.
Analysis of sensor network observations during some simulated landslide experiments
NASA Astrophysics Data System (ADS)
Scaioni, M.; Lu, P.; Feng, T.; Chen, W.; Wu, H.; Qiao, G.; Liu, C.; Tong, X.; Li, R.
2012-12-01
A multi-sensor network was tested during some experiments on a landslide simulation platform established at Tongji University (Shanghai, P.R. China). Here landslides were triggered by means of artificial rainfall (see Figure 1). The sensor network currently incorporates contact sensors and two imaging systems. This represent a novel solution, because the spatial sensor network incorporate either contact sensors and remote sensors (video-cameras). In future, these sensors will be installed on two real ground slopes in Sichuan province (South-West China), where Wenchuan earthquake occurred in 2008. This earthquake caused the immediate activation of several landslide, while other area became unstable and still are a menace for people and properties. The platform incorporates the reconstructed scale slope, sensor network, communication system, database and visualization system. Some landslide simulation experiments allowed ascertaining which sensors could be more suitable to be deployed in Wenchuan area. The poster will focus on the analysis of results coming from down scale simulations. Here the different steps of the landslide evolution can be followed on the basis of sensor observations. This include underground sensors to detect the water table level and the pressure in the ground, a set of accelerometers and two inclinometers. In the first part of the analysis the full data series are investigated to look for correlations and common patterns, as well as to link them to the physical processes. In the second, 4 subsets of sensors located in neighbor positions are analyzed. The analysis of low- and high-speed image sequences allowed to track a dense field of displacement on the slope surface. These outcomes have been compared to the ones obtained from accelerometers for cross-validation. Images were also used for the photogrammetric reconstruction of the slope topography during the experiment. Consequently, volume computation and mass movements could be evaluated on
Eddy-Covariance Observations and Large-Eddy-Simulations of Near-Shore Fluxes from Water Bodies
NASA Astrophysics Data System (ADS)
Bohrer, G.; Rey Sanchez, C.; Kenny, W.; Morin, T. H.
2017-12-01
Eddy covariance (EC) measurement techniques are increasingly used in the study of lakes and coastal ecosystems. The sharp water-shore transitions in energy forcing and surface roughness are challenging the validity of the EC approach at these sites. We discuss the results of two seasonal campaigns to measure CO2 and water-vapor fluxes in coastal environments - a small lake in Michigan, and the water over a coral reef in the Red, Sea, Israel. We show that in both environments, horizontal advection of CO2 and water vapor is responsible to a non-negligible component of the total flux to/from the water. We used a two-tower approach to measure fluxes from the water and from the shore and calculate the advection and flux divergence between the two. An empirical footprint model was used to filter the observations and keep only the times when interference from the shore-line transition is minimal. Observations of both vertical turbulent fluxes and advection were gapfilled with a neural-network model, based on their observed relationships with environmental forcing. Gap-filled observations were used to determine the seasonal net fluxes for the tow ecosystems. We used Large-Eddy Simulations (LES) to conduct a case study of airflow patterns associated with a small inland lake surrounded by forest (i.e. radius of lake only ten times the height of the forest). We combined LES outputs with scalar dispersion simulations to model potential biases in EC flux measurements due to the heterogeneity of surface fluxes and vertical advection. Our simulations show that the lake-to-forest transition can induce a non-zero vertical wind component, which will strongly affect the interpretation of wind and flux measurements. Furthermore, significant horizontal gradients of CO2 are generated by the forest carbon sink and lake carbon source, which are further transported by local roughness-induced circulation. We simulated six hypothetical flux tower locations along a downwind gradient at
DOE Office of Scientific and Technical Information (OSTI.GOV)
Varble, A. C.; Zipser, Edward J.; Fridlind, Ann
2014-12-27
Ten 3D cloud-resolving model (CRM) simulations and four 3D limited area model (LAM) simulations of an intense mesoscale convective system observed on January 23-24, 2006 during the Tropical Warm Pool – International Cloud Experiment (TWP-ICE) are compared with each other and with observed radar reflectivity fields and dual-Doppler retrievals of vertical wind speeds in an attempt to explain published results showing a high bias in simulated convective radar reflectivity aloft. This high bias results from ice water content being large, which is a product of large, strong convective updrafts, although hydrometeor size distribution assumptions modulate the size of this bias.more » Snow reflectivity can exceed 40 dBZ in a two-moment scheme when a constant bulk density of 100 kg m-3 is used. Making snow mass more realistically proportional to area rather than volume should somewhat alleviate this problem. Graupel, unlike snow, produces high biased reflectivity in all simulations. This is associated with large amounts of liquid water above the freezing level in updraft cores. Peak vertical velocities in deep convective updrafts are greater than dual-Doppler retrieved values, especially in the upper troposphere. Freezing of large rainwater contents lofted above the freezing level in simulated updraft cores greatly contributes to these excessive upper tropospheric vertical velocities. Strong simulated updraft cores are nearly undiluted, with some showing supercell characteristics. Decreasing horizontal grid spacing from 900 meters to 100 meters weakens strong updrafts, but not enough to match observational retrievals. Therefore, overly intense simulated updrafts may partly be a product of interactions between convective dynamics, parameterized microphysics, and large-scale environmental biases that promote different convective modes and strengths than observed.« less
Realistic Simulations of Coronagraphic Observations with WFIRST
NASA Astrophysics Data System (ADS)
Rizzo, Maxime; Zimmerman, Neil; Roberge, Aki; Lincowski, Andrew; Arney, Giada; Stark, Chris; Jansen, Tiffany; Turnbull, Margaret; WFIRST Science Investigation Team (Turnbull)
2018-01-01
We present a framework to simulate observing scenarios with the WFIRST Coronagraphic Instrument (CGI). The Coronagraph and Rapid Imaging Spectrograph in Python (crispy) is an open-source package that can be used to create CGI data products for analysis and development of post-processing routines. The software convolves time-varying coronagraphic PSFs with realistic astrophysical scenes which contain a planetary architecture, a consistent dust structure, and a background field composed of stars and galaxies. The focal plane can be read out by a WFIRST electron-multiplying CCD model directly, or passed through a WFIRST integral field spectrograph model first. Several elementary post-processing routines are provided as part of the package.
Science simulations for the New Worlds Observer
NASA Astrophysics Data System (ADS)
Schindhelm, Eric; Cash, Webster; Seager, Sara
2005-08-01
The New Worlds Observer, currently studied under a NASA Institute for Advanced Concepts grant, will be a pinhole camera in space designed to directly detect and study extrasolar terrestrial planets. An apodized occultor or pinhole creates an image of the planetary system in the focal plane far away, where a second telescope craft orbits to detect the light. In this study we simulate the expected signal of NWO to find the optimal configuration and specifications of the two craft. The efficiency of direct detection through photometric imaging depends strongly on occulter and telescope size, while preliminary studies on absorption biomarker detection and photometric variability measurements are summarized.
Theory and observations: Model simulations of the period 1955-1985
NASA Technical Reports Server (NTRS)
Isaksen, Ivar S. A.; Eckman, R.; Lacis, A.; Ko, Malcolm K. W.; Prather, M.; Pyle, J.; Rodhe, H.; Stordal, Frode; Stolarski, R. S.; Turco, R. P.
1989-01-01
The main objective of the theoretical studies presented here is to apply models of stratospheric chemistry and transport in order to understand the processes that control stratospheric ozone and that are responsible for the observed variations. The model calculations are intended to simulate the observed behavior of atmospheric ozone over the past three decades (1955-1985), for which there exists a substantial record of both ground-based and, more recently, satellite measurements. Ozone concentrations in the atmosphere vary on different time scales and for several different causes. The models described here were designed to simulate the effect on ozone of changes in the concentration of such trace gases as CFC, CH4, N2O, and CO2. Changes from year to year in ultraviolet radiation associated with the solar cycle are also included in the models. A third source of variability explicitly considered is the sporadic introduction of large amounts of NO sub x into the stratosphere during atmospheric nuclear tests.
NASA Technical Reports Server (NTRS)
Fairfield, Donald H.; Otto, A.
1999-01-01
On March 24, 1995 the Geotail spacecraft observed large fluctuations of the magnetic field and plasma properties in the Low Latitude Boundary Layer (LLBL) about 15 R(sub E) tailward of the dusk meridian. Although the magnetospheric and the magnetosheath field were strongly northward, the B(sub z) component showed strong short duration fluctuations in which B(sub z) could even reach negative values. We have used two-dimensional magnetohydrodynamic simulations with magnetospheric and magnetosheath input parameters specifically chosen for this. Geotail event to identify the processes which cause the observed boundary properties. It is shown that these fluctuations can be explained by the Kelvin-Helmholtz instability if the k vector of the instability has a component along the magnetic field direction. The simulation results show many of the characteristic properties of the Geotail observations. In particular, the quasi-periodic strong fluctuations are well explained by satellite crossings through the Kelvin-Helmholtz vortices. It is illustrated how the interior structure of the Kelvin-Helmholtz vortices leads to the rapid fluctuations in the Geotail observations. Our results suggest an average Kelvin-Helmholtz wavelength of about 5 R(sub E) with a vortex size of close to 2 R(sub E) for an average repetition time of 2.5 minutes. The growth time for these waves implies a source region of about 10 to 16 R(sub E) upstream from the location of the Geotail spacecraft (i.e., near the dusk meridian). The results also indicate a considerable mass transport of magnetosheath material into the magnetosphere by magnetic reconnection in the Kelvin-Helmholtz vortices.
Intercomparison of microphysical datasets collected from CAIPEEX observations and WRF simulation
NASA Astrophysics Data System (ADS)
Pattnaik, S.; Goswami, B.; Kulkarni, J.
2009-12-01
In the first phase of ongoing Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program of Indian Institute of Tropical Meteorology (IITM), intensive cloud microphysical datasets are collected over India during the May through September, 2009. This study is designed to evaluate the forecast skills of existing cloud microphysical parameterization schemes (i.e. single moment/double moments) within the WRF-ARW model (Version 3.1.1) during different intensive observation periods (IOP) over the targeted regions spreading all across India. Basic meteorological and cloud microphysical parameters obtained from the model simulations are validated against the observed data set collected during CAIPEEX program. For this study, we have considered three IOP phases (i.e. May 23-27, June 11-15, July 3-7) carried out over northern, central and western India respectively. This study emphasizes the thrust to understand the mechanism of evolution, intensification and distribution of simulated precipitation forecast upto day four (i.e. 96 hour forecast). Efforts have also been made to carryout few important microphysics sensitivity experiments within the explicit schemes to investigate their respective impact on the formation and distribution of vital cloud parameters (e.g. cloud liquid water, frozen hydrometeors) and model rainfall forecast over the IOP regions. The characteristic features of liquid and frozen hydrometers in the pre-monsoon and monsoon regimes are examined from model forecast as well as from CAIPEEX observation data set for different IOPs. The model is integrated in a triply nested fashion with an innermost nest explicitly resolved at a horizontal resolution of 4km.In this presentation preliminary results from aforementioned research initiatives will be introduced.
The VIIRS Ocean Data Simulator Enhancements and Results
NASA Technical Reports Server (NTRS)
Robinson, Wayne D.; Patt, Fredrick S.; Franz, Bryan A.; Turpie, Kevin R.; McClain, Charles R.
2011-01-01
The VIIRS Ocean Science Team (VOST) has been developing an Ocean Data Simulator to create realistic VIIRS SDR datasets based on MODIS water-leaving radiances. The simulator is helping to assess instrument performance and scientific processing algorithms. Several changes were made in the last two years to complete the simulator and broaden its usefulness. The simulator is now fully functional and includes all sensor characteristics measured during prelaunch testing, including electronic and optical crosstalk influences, polarization sensitivity, and relative spectral response. Also included is the simulation of cloud and land radiances to make more realistic data sets and to understand their important influence on nearby ocean color data. The atmospheric tables used in the processing, including aerosol and Rayleigh reflectance coefficients, have been modeled using VIIRS relative spectral responses. The capabilities of the simulator were expanded to work in an unaggregated sample mode and to produce scans with additional samples beyond the standard scan. These features improve the capability to realistically add artifacts which act upon individual instrument samples prior to aggregation and which may originate from beyond the actual scan boundaries. The simulator was expanded to simulate all 16 M-bands and the EDR processing was improved to use these bands to make an SST product. The simulator is being used to generate global VIIRS data from and in parallel with the MODIS Aqua data stream. Studies have been conducted using the simulator to investigate the impact of instrument artifacts. This paper discusses the simulator improvements and results from the artifact impact studies.
The VIIRS ocean data simulator enhancements and results
NASA Astrophysics Data System (ADS)
Robinson, Wayne D.; Patt, Frederick S.; Franz, Bryan A.; Turpie, Kevin R.; McClain, Charles R.
2011-10-01
The VIIRS Ocean Science Team (VOST) has been developing an Ocean Data Simulator to create realistic VIIRS SDR datasets based on MODIS water-leaving radiances. The simulator is helping to assess instrument performance and scientific processing algorithms. Several changes were made in the last two years to complete the simulator and broaden its usefulness. The simulator is now fully functional and includes all sensor characteristics measured during prelaunch testing, including electronic and optical crosstalk influences, polarization sensitivity, and relative spectral response. Also included is the simulation of cloud and land radiances to make more realistic data sets and to understand their important influence on nearby ocean color data. The atmospheric tables used in the processing, including aerosol and Rayleigh reflectance coefficients, have been modeled using VIIRS relative spectral responses. The capabilities of the simulator were expanded to work in an unaggregated sample mode and to produce scans with additional samples beyond the standard scan. These features improve the capability to realistically add artifacts which act upon individual instrument samples prior to aggregation and which may originate from beyond the actual scan boundaries. The simulator was expanded to simulate all 16 M-bands and the EDR processing was improved to use these bands to make an SST product. The simulator is being used to generate global VIIRS data from and in parallel with the MODIS Aqua data stream. Studies have been conducted using the simulator to investigate the impact of instrument artifacts. This paper discusses the simulator improvements and results from the artifact impact studies.
NASA Technical Reports Server (NTRS)
Nearing, Grey S.; Crow, Wade T.; Thorp, Kelly R.; Moran, Mary S.; Reichle, Rolf H.; Gupta, Hoshin V.
2012-01-01
Observing system simulation experiments were used to investigate ensemble Bayesian state updating data assimilation of observations of leaf area index (LAI) and soil moisture (theta) for the purpose of improving single-season wheat yield estimates with the Decision Support System for Agrotechnology Transfer (DSSAT) CropSim-Ceres model. Assimilation was conducted in an energy-limited environment and a water-limited environment. Modeling uncertainty was prescribed to weather inputs, soil parameters and initial conditions, and cultivar parameters and through perturbations to model state transition equations. The ensemble Kalman filter and the sequential importance resampling filter were tested for the ability to attenuate effects of these types of uncertainty on yield estimates. LAI and theta observations were synthesized according to characteristics of existing remote sensing data, and effects of observation error were tested. Results indicate that the potential for assimilation to improve end-of-season yield estimates is low. Limitations are due to a lack of root zone soil moisture information, error in LAI observations, and a lack of correlation between leaf and grain growth.
NASA Astrophysics Data System (ADS)
Chen, M.; Lemon, C.; Sazykin, S. Y.; Wolf, R.; Anderson, P. C.
2016-12-01
Sub-Auroral Polarization Streams (SAPS), characterized by large subauroral E x B velocities that span from dusk to the early morning sector for high magnetic activity, result from strong magnetosphere-ionosphere coupling. We investigate how electron and ion precipitation and the ionospheric conductance affect the simulated development of the SAPS electric field for the 17 March 2013 storm. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the SAPS. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. Ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. The electron and proton contributions to the auroral conductance in the RCM-E are calculated using the empirical Robinson et al. [JGR, 1987] and Galand and Richmond [JGR, 2001] equations, respectively. The "background" ionospheric conductance is based on parameters from the International Reference Ionosphere [Bilitza and Reinisch, JASR, 2008] but modified to include the effect of specified ionospheric troughs. Parameterized simulations will aid in understanding the underlying physical process. We compare simulated precipitating particle energy flux and E x B velocities with DMSP observations where SAPS are observed during the 17 March 2013 storm. Analysis of discerpancies between the simulation results and data will aid us in assessing needed improvements in the model.
NASA Astrophysics Data System (ADS)
Yan, Xuewei; Xu, Qingyan; Liu, Baicheng
2017-12-01
Dendritic structures are the predominant microstructural constituents of nickel-based superalloys, an understanding of the dendrite growth is required in order to obtain the desirable microstructure and improve the performance of castings. For this reason, numerical simulation method and an in-situ observation technology by employing high temperature confocal laser scanning microscopy (HT-CLSM) were used to investigate dendrite growth during solidification process. A combined cellular automaton-finite difference (CA-FD) model allowing for the prediction of dendrite growth of binary alloys was developed. The algorithm of cells capture was modified, and a deterministic cellular automaton (DCA) model was proposed to describe neighborhood tracking. The dendrite and detail morphology, especially hundreds of dendrites distribution at a large scale and three-dimensional (3-D) polycrystalline growth, were successfully simulated based on this model. The dendritic morphologies of samples before and after HT-CLSM were both observed by optical microscope (OM) and scanning electron microscope (SEM). The experimental observations presented a reasonable agreement with the simulation results. It was also found that primary or secondary dendrite arm spacing, and segregation pattern were significantly influenced by dendrite growth. Furthermore, the directional solidification (DS) dendritic evolution behavior and detail morphology were also simulated based on the proposed model, and the simulation results also agree well with experimental results.
Clinical results of computerized tomography-based simulation with laser patient marking.
Ragan, D P; Forman, J D; He, T; Mesina, C F
1996-02-01
Accuracy of a patient treatment portal marking device and computerized tomography (CT) simulation have been clinically tested. A CT-based simulator has been assembled based on a commercial CT scanner. This includes visualization software and a computer-controlled laser drawing device. This laser drawing device is used to transfer the setup, central axis, and/or radiation portals from the CT simulator to the patient for appropriate patient skin marking. A protocol for clinical testing is reported. Twenty-five prospectively, sequentially accessioned patients have been analyzed. The simulation process can be completed in an average time of 62 min. Under many cases, the treatment portals can be designed and the patient marked in one session. Mechanical accuracy of the system was found to be within +/- 1mm. The portal projection accuracy in clinical cases is observed to be better than +/- 1.2 mm. Operating costs are equivalent to the conventional simulation process it replaces. Computed tomography simulation is a clinical accurate substitute for conventional simulation when used with an appropriate patient marking system and digitally reconstructed radiographs. Personnel time spent in CT simulation is equivalent to time in conventional simulation.
Strategy for long-term 3D cloud-resolving simulations over the ARM SGP site and preliminary results
NASA Astrophysics Data System (ADS)
Lin, W.; Liu, Y.; Song, H.; Endo, S.
2011-12-01
Parametric representations of cloud/precipitation processes continue having to be adopted in climate simulations with increasingly higher spatial resolution or with emerging adaptive mesh framework; and it is only becoming more critical that such parameterizations have to be scale aware. Continuous cloud measurements at DOE's ARM sites have provided a strong observational basis for novel cloud parameterization research at various scales. Despite significant progress in our observational ability, there are important cloud-scale physical and dynamical quantities that are either not currently observable or insufficiently sampled. To complement the long-term ARM measurements, we have explored an optimal strategy to carry out long-term 3-D cloud-resolving simulations over the ARM SGP site using Weather Research and Forecasting (WRF) model with multi-domain nesting. The factors that are considered to have important influences on the simulated cloud fields include domain size, spatial resolution, model top, forcing data set, model physics and the growth of model errors. The hydrometeor advection that may play a significant role in hydrological process within the observational domain but is often lacking, and the limitations due to the constraint of domain-wide uniform forcing in conventional cloud system-resolving model simulations, are at least partly accounted for in our approach. Conventional and probabilistic verification approaches are employed first for selected cases to optimize the model's capability of faithfully reproducing the observed mean and statistical distributions of cloud-scale quantities. This then forms the basis of our setup for long-term cloud-resolving simulations over the ARM SGP site. The model results will facilitate parameterization research, as well as understanding and dissecting parameterization deficiencies in climate models.
NASA Astrophysics Data System (ADS)
Fridlind, A. M.; Atlas, R.; van Diedenhoven, B.; Ackerman, A. S.; Rind, D. H.; Harrington, J. Y.; McFarquhar, G. M.; Um, J.; Jackson, R.; Lawson, P.
2017-12-01
It has recently been suggested that seeding synoptic cirrus could have desirable characteristics as a geoengineering approach, but surprisingly large uncertainties remain in the fundamental parameters that govern cirrus properties, such as mass accommodation coefficient, ice crystal physical properties, aggregation efficiency, and ice nucleation rate from typical upper tropospheric aerosol. Only one synoptic cirrus model intercomparison study has been published to date, and studies that compare the shapes of observed and simulated ice size distributions remain sparse. Here we amend a recent model intercomparison setup using observations during two 2010 SPARTICUS campaign flights. We take a quasi-Lagrangian column approach and introduce an ensemble of gravity wave scenarios derived from collocated Doppler cloud radar retrievals of vertical wind speed. We use ice crystal properties derived from in situ cloud particle images, for the first time allowing smoothly varying and internally consistent treatments of nonspherical ice capacitance, fall speed, gravitational collection, and optical properties over all particle sizes in our model. We test two new parameterizations for mass accommodation coefficient as a function of size, temperature and water vapor supersaturation, and several ice nucleation scenarios. Comparison of results with in situ ice particle size distribution data, corrected using state-of-the-art algorithms to remove shattering artifacts, indicate that poorly constrained uncertainties in the number concentration of crystals smaller than 100 µm in maximum dimension still prohibit distinguishing which parameter combinations are more realistic. When projected area is concentrated at such sizes, the only parameter combination that reproduces observed size distribution properties uses a fixed mass accommodation coefficient of 0.01, on the low end of recently reported values. No simulations reproduce the observed abundance of such small crystals when the
Mercury's plasma belt: hybrid simulations results compared to in-situ measurements
NASA Astrophysics Data System (ADS)
Hercik, D.; Travnicek, P. M.; Schriver, D.; Hellinger, P.
2012-12-01
The presence of plasma belt and trapped particles region in the Mercury's inner magnetosphere has been questionable due to small dimensions of the magnetosphere of Mercury compared to Earth, where these regions are formed. Numerical simulations of the solar wind interaction with Mercury's magnetic field suggested that such a structure could be found also in the vicinity of Mercury. These results has been recently confirmed also by MESSENGER observations. Here we present more detailed analysis of the plasma belt structure and quasi-trapped particle population characteristics and behaviour under different orientations of the interplanetary magnetic field.The plasma belt region is constantly supplied with solar wind protons via magnetospheric flanks and tail current sheet region. Protons inside the plasma belt region are quasi-trapped in the magnetic field of Mercury and perform westward drift along the planet. This region is well separated by a magnetic shell and has higher average temperatures and lower bulk proton current densities than surrounding area. On the day side the population exhibits loss cone distribution function matching the theoretical loss cone angle. Simulations results are also compared to in-situ measurements acquired by MESSENGER MAG and FIPS instruments.
Tillman, Fred D.; Gangopadhyay, Subhrendu; Pruitt, Tom
2017-01-01
In evaluating potential impacts of climate change on water resources, water managers seek to understand how future conditions may differ from the recent past. Studies of climate impacts on groundwater recharge often compare simulated recharge from future and historical time periods on an average monthly or overall average annual basis, or compare average recharge from future decades to that from a single recent decade. Baseline historical recharge estimates, which are compared with future conditions, are often from simulations using observed historical climate data. Comparison of average monthly results, average annual results, or even averaging over selected historical decades, may mask the true variability in historical results and lead to misinterpretation of future conditions. Comparison of future recharge results simulated using general circulation model (GCM) climate data to recharge results simulated using actual historical climate data may also result in an incomplete understanding of the likelihood of future changes. In this study, groundwater recharge is estimated in the upper Colorado River basin, USA, using a distributed-parameter soil-water balance groundwater recharge model for the period 1951–2010. Recharge simulations are performed using precipitation, maximum temperature, and minimum temperature data from observed climate data and from 97 CMIP5 (Coupled Model Intercomparison Project, phase 5) projections. Results indicate that average monthly and average annual simulated recharge are similar using observed and GCM climate data. However, 10-year moving-average recharge results show substantial differences between observed and simulated climate data, particularly during period 1970–2000, with much greater variability seen for results using observed climate data.
NASA Astrophysics Data System (ADS)
Kaiser, Christopher; Hendricks, Johannes; Righi, Mattia; Jöckel, Patrick
2016-04-01
aerosol and black carbon mass mixing ratio with altitude than found in the observations. In contrast, measured profiles from the HIPPO project are qualitatively captured well. Similar conclusions hold for the comparison of simulated and measured aerosol particle number concentrations. On the one hand, these results exemplify the difficulty in evaluating the representativeness of the simulated global climatological state of the aerosol by means of comparison with individually measured vertical profiles. On the other hand, it highlights the value of aircraft campaigns with large spatial and temporal coverage for model evaluation.
NASA Technical Reports Server (NTRS)
Wang, James S.; Kawa, S. Randolph; Eluszkiewicz, Janusz; Collatz, G. J.; Mountain, Marikate; Henderson, John; Nehrkorn, Thomas; Aschbrenner, Ryan; Zaccheo, T. Scott
2012-01-01
Knowledge of the spatiotemporal variations in emissions and uptake of CO2 is hampered by sparse measurements. The recent advent of satellite measurements of CO2 concentrations is increasing the density of measurements, and the future mission ASCENDS (Active Sensing of CO2 Emissions over Nights, Days and Seasons) will provide even greater coverage and precision. Lagrangian atmospheric transport models run backward in time can quantify surface influences ("footprints") of diverse measurement platforms and are particularly well suited for inverse estimation of regional surface CO2 fluxes at high resolution based on satellite observations. We utilize the STILT Lagrangian particle dispersion model, driven by WRF meteorological fields at 40-km resolution, in a Bayesian synthesis inversion approach to quantify the ability of ASCENDS column CO2 observations to constrain fluxes at high resolution. This study focuses on land-based biospheric fluxes, whose uncertainties are especially large, in a domain encompassing North America. We present results based on realistic input fields for 2007. Pseudo-observation random errors are estimated from backscatter and optical depth measured by the CALIPSO satellite. We estimate a priori flux uncertainties based on output from the CASA-GFED (v.3) biosphere model and make simple assumptions about spatial and temporal error correlations. WRF-STILT footprints are convolved with candidate vertical weighting functions for ASCENDS. We find that at a horizontal flux resolution of 1 degree x 1 degree, ASCENDS observations are potentially able to reduce average weekly flux uncertainties by 0-8% in July, and 0-0.5% in January (assuming an error of 0.5 ppm at the Railroad Valley reference site). Aggregated to coarser resolutions, e.g. 5 degrees x 5 degrees, the uncertainty reductions are larger and more similar to those estimated in previous satellite data observing system simulation experiments.
Generalizing observational study results: applying propensity score methods to complex surveys.
Dugoff, Eva H; Schuler, Megan; Stuart, Elizabeth A
2014-02-01
To provide a tutorial for using propensity score methods with complex survey data. Simulated data and the 2008 Medical Expenditure Panel Survey. Using simulation, we compared the following methods for estimating the treatment effect: a naïve estimate (ignoring both survey weights and propensity scores), survey weighting, propensity score methods (nearest neighbor matching, weighting, and subclassification), and propensity score methods in combination with survey weighting. Methods are compared in terms of bias and 95 percent confidence interval coverage. In Example 2, we used these methods to estimate the effect on health care spending of having a generalist versus a specialist as a usual source of care. In general, combining a propensity score method and survey weighting is necessary to achieve unbiased treatment effect estimates that are generalizable to the original survey target population. Propensity score methods are an essential tool for addressing confounding in observational studies. Ignoring survey weights may lead to results that are not generalizable to the survey target population. This paper clarifies the appropriate inferences for different propensity score methods and suggests guidelines for selecting an appropriate propensity score method based on a researcher's goal. © Health Research and Educational Trust.
Constraints on Cumulus Parameterization from Simulations of Observed MJO Events
NASA Technical Reports Server (NTRS)
Del Genio, Anthony; Wu, Jingbo; Wolf, Audrey B.; Chen, Yonghua; Yao, Mao-Sung; Kim, Daehyun
2015-01-01
Two recent activities offer an opportunity to test general circulation model (GCM) convection and its interaction with large-scale dynamics for observed Madden-Julian oscillation (MJO) events. This study evaluates the sensitivity of the Goddard Institute for Space Studies (GISS) GCM to entrainment, rain evaporation, downdrafts, and cold pools. Single Column Model versions that restrict weakly entraining convection produce the most realistic dependence of convection depth on column water vapor (CWV) during the Atmospheric Radiation Measurement MJO Investigation Experiment at Gan Island. Differences among models are primarily at intermediate CWV where the transition from shallow to deeper convection occurs. GCM 20-day hindcasts during the Year of Tropical Convection that best capture the shallow–deep transition also produce strong MJOs, with significant predictability compared to Tropical Rainfall Measuring Mission data. The dry anomaly east of the disturbance on hindcast day 1 is a good predictor of MJO onset and evolution. Initial CWV there is near the shallow–deep transition point, implicating premature onset of deep convection as a predictor of a poor MJO simulation. Convection weakly moistens the dry region in good MJO simulations in the first week; weakening of large-scale subsidence over this time may also affect MJO onset. Longwave radiation anomalies are weakest in the worst model version, consistent with previous analyses of cloud/moisture greenhouse enhancement as the primary MJO energy source. The authors’ results suggest that both cloud-/moisture-radiative interactions and convection–moisture sensitivity are required to produce a successful MJO simulation.
NASA Astrophysics Data System (ADS)
Maxwell, R. M.; Condon, L. E.; Atchley, A. L.; Hector, B.
2017-12-01
Quantifying the available freshwater for human use and ecological function depends on fluxes and stores that are hard to observe. Evapotranspiration (ET) is the largest terrestrial flux of water behind precipitation but is observed with low spatial density. Likewise, groundwater is the largest freshwater store, yet is equally uncertain. The ability to upscale observations of these variables is an additional complication; point measurements are made at scales orders of magnitude smaller than remote sensing data products. Integrated hydrologic models that simulate continental extents at fine spatial resolution are now becoming an additional tool to constrain fluxes and address interconnections. For example, recent work has shown connections between water table depth and transpiration partitioning, and demonstrated the ability to reconcile point observations and large-scale inferences. Here we explore the dynamics of large hydrologic systems experiencing change and stress across continental North America using integrated model simulations, observations and data products. Simulations of aquifer depletion due to pervasive groundwater pumping diagnose both stream depletion and changes in ET. Simulations of systematic increases in temperature are used to understand the relationship between snowpack dynamics, surface and groundwater flow, ET and a changing climate. Remotely sensed products including the GRACE estimates of total storage change are downscaled using model simulations to better understand human impacts to the hydrologic cycle. These example applications motivate a path forward to better use simulations to understand water availability.
NASA Astrophysics Data System (ADS)
Sun, Cheng; Li, Jianping; Kucharski, Fred; Xue, Jiaqing; Li, Xiang
2018-04-01
circulation (AMOC) and northward ocean heat transport caused by the accumulated effect of NAO forcing, reasonably well captures the observed multidecadal fluctuations in the AMO. Further analysis using the fully coupled model simulations provides direct modeling evidence that the observed spatial coherence of decadal SST variations across North Atlantic basin can be reproduced only by including the AMOC-related ocean dynamics, and the AMOC acts as a common forcing signal that results in a spatially coherent variation of North Atlantic SST.
NASA Technical Reports Server (NTRS)
Douglass, Anne R.; Stolarski, Richard S.; Steenrod, Steven; Pawson, Steven
2003-01-01
One key application of atmospheric chemistry and transport models is prediction of the response of ozone and other constituents to various natural and anthropogenic perturbations. These include changes in composition, such as the previous rise and recent decline in emission of man-made chlorofluorcarbons, changes in aerosol loading due to volcanic eruption, and changes in solar forcing. Comparisons of hindcast model results for the past few decades with observations are a key element of model evaluation and provide a sense of the reliability of model predictions. The 25 year data set from Total Ozone Mapping Spectrometers is a cornerstone of such model evaluation. Here we report evaluation of three-dimensional multi-decadal simulation of stratospheric composition. Meteorological fields for this off-line calculation are taken from a 50 year simulation of a general circulation model. Model fields are compared with observations from TOMS and also with observations from the Stratospheric Aerosol and Gas Experiment (SAGE), Microwave Limb Sounder (MLS), Cryogenic Limb Array Etalon Spectrometer (CLAES), and the Halogen Occultation Experiment (HALOE). This overall evaluation will emphasize the spatial, seasonal, and interannual variability of the simulation compared with observed atmospheric variability.
NASA Astrophysics Data System (ADS)
Zhang, Guang J.; Zurovac-Jevtic, Dance; Boer, Erwin R.
1999-10-01
A Lagrangian cloud classification algorithm is applied to the cloud fields in the tropical Pacific simulated by a high-resolution regional atmospheric model. The purpose of this work is to assess the model's ability to reproduce the observed spatial characteristics of the tropical cloud systems. The cloud systems are broadly grouped into three categories: deep clouds, mid-level clouds and low clouds. The deep clouds are further divided into mesoscale convective systems and nonmesoscale convective systems. It is shown that the model is able to simulate the total cloud cover for each category reasonably well. However, when the cloud cover is broken down into contributions from cloud systems of different sizes, it is shown that the simulated cloud size distribution is biased toward large cloud systems, with contribution from relatively small cloud systems significantly under-represented in the model for both deep and mid-level clouds. The number distribution and area contribution to the cloud cover from mesoscale convective systems are very well simulated compared to the satellite observations, so are low clouds as well. The dependence of the cloud physical properties on cloud scale is examined. It is found that cloud liquid water path, rainfall, and ocean surface sensible and latent heat fluxes have a clear dependence on cloud types and scale. This is of particular interest to studies of the cloud effects on surface energy budget and hydrological cycle. The diurnal variation of the cloud population and area is also examined. The model exhibits a varying degree of success in simulating the diurnal variation of the cloud number and area. The observed early morning maximum cloud cover in deep convective cloud systems is qualitatively simulated. However, the afternoon secondary maximum is missing in the model simulation. The diurnal variation of the tropospheric temperature
Simulating pre-galactic metal enrichment for JWST deep-field observations
NASA Astrophysics Data System (ADS)
Jaacks, Jason
2017-08-01
We propose to create a new suite of mesoscale cosmological volume simulations with custom built sub-grid physics in which we independently track the contribution from Population III and Population II star formation to the total metals in the interstellar medium (ISM) of the first galaxies, and in the diffuse IGM at an epoch prior to reionization. These simulations will fill a gap in our simulation knowledge about chemical enrichment in the pre-reionization universe, which is a crucial need given the impending observational push into this epoch with near-future ground and space-based telescopes. This project is the natural extension of our successful Cycle 24 theory proposal (HST-AR-14569.001-A; PI Jaacks) in which we developed a new Pop III star formation sub-grid model which is currently being utilized to study the baseline metal enrichment of pre-reionization systems.
First results of coupled IPS/NIMROD/GENRAY simulations
NASA Astrophysics Data System (ADS)
Jenkins, Thomas; Kruger, S. E.; Held, E. D.; Harvey, R. W.; Elwasif, W. R.; Schnack, D. D.
2010-11-01
The Integrated Plasma Simulator (IPS) framework, developed by the SWIM Project Team, facilitates self-consistent simulations of complicated plasma behavior via the coupling of various codes modeling different spatial/temporal scales in the plasma. Here, we apply this capability to investigate the stabilization of tearing modes by ECCD. Under IPS control, the NIMROD code (MHD) evolves fluid equations to model bulk plasma behavior, while the GENRAY code (RF) calculates the self-consistent propagation and deposition of RF power in the resulting plasma profiles. GENRAY data is then used to construct moments of the quasilinear diffusion tensor (induced by the RF) which influence the dynamics of momentum/energy evolution in NIMROD's equations. We present initial results from these coupled simulations and demonstrate that they correctly capture the physics of magnetic island stabilization [Jenkins et al, PoP 17, 012502 (2010)] in the low-beta limit. We also discuss the process of code verification in these simulations, demonstrating good agreement between NIMROD and GENRAY predictions for the flux-surface-averaged, RF-induced currents. An overview of ongoing model development (synthetic diagnostics/plasma control systems; neoclassical effects; etc.) is also presented. Funded by US DoE.
Medical Simulation Practices 2010 Survey Results
NASA Technical Reports Server (NTRS)
McCrindle, Jeffrey J.
2011-01-01
Medical Simulation Centers are an essential component of our learning infrastructure to prepare doctors and nurses for their careers. Unlike the military and aerospace simulation industry, very little has been published regarding the best practices currently in use within medical simulation centers. This survey attempts to provide insight into the current simulation practices at medical schools, hospitals, university nursing programs and community college nursing programs. Students within the MBA program at Saint Joseph's University conducted a survey of medical simulation practices during the summer 2010 semester. A total of 115 institutions responded to the survey. The survey resus discuss overall effectiveness of current simulation centers as well as the tools and techniques used to conduct the simulation activity
USDA-ARS?s Scientific Manuscript database
We develop a robust understanding of the effects of assimilating remote sensing observations of leaf area index and soil moisture (in the top 5 cm) on DSSAT-CSM CropSim-Ceres wheat yield estimates. Synthetic observing system simulation experiments compare the abilities of the Ensemble Kalman Filter...
NASA Astrophysics Data System (ADS)
Wainwright, Carroll L.; Johnson, Matthew C.; Peiris, Hiranya V.; Aguirre, Anthony; Lehner, Luis; Liebling, Steven L.
2014-03-01
The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. We develop and implement an algorithm for accurately computing the cosmological observables arising from bubble collisions directly from the Lagrangian of a single scalar field. We first simulate the collision spacetime by solving Einstein's equations, starting from nucleation and ending at reheating. Taking advantage of the collision's hyperbolic symmetry, the simulations are performed with a 1+1-dimensional fully relativistic code that uses adaptive mesh refinement. We then calculate the comoving curvature perturbation in an open Friedmann-Robertson-Walker universe, which is used to determine the temperature anisotropies of the cosmic microwave background radiation. For a fiducial Lagrangian, the anisotropies are well described by a power law in the cosine of the angular distance from the center of the collision signature. For a given form of the Lagrangian, the resulting observational predictions are inherently statistical due to stochastic elements of the bubble nucleation process. Further uncertainties arise due to our imperfect knowledge about inflationary and pre-recombination physics. We characterize observational predictions by computing the probability distributions over four phenomenological parameters which capture these intrinsic and model uncertainties. This represents the first fully-relativistic set of predictions from an ensemble of scalar field models giving rise to eternal inflation, yielding significant differences from previous non-relativistic approximations. Thus, our results provide a basis for a rigorous confrontation of these theories with cosmological data.
NASA Astrophysics Data System (ADS)
Goudarzi, Shervin; Amrollahi, R.; Niknam Sharak, M.
2014-06-01
In this paper the results of the numerical simulation for Amirkabir Mather-type Plasma Focus Facility (16 kV, 36μF and 115 nH) in several experiments with Argon as working gas at different working conditions (different discharge voltages and gas pressures) have been presented and compared with the experimental results. Two different models have been used for simulation: five-phase model of Lee and lumped parameter model of Gonzalez. It is seen that the results (optimum pressures and current signals) of the Lee model at different working conditions show better agreement than lumped parameter model with experimental values.
Reime, Marit Hegg; Johnsgaard, Tone; Kvam, Fred Ivan; Aarflot, Morten; Engeberg, Janecke Merethe; Breivik, Marit; Brattebø, Guttorm
2017-01-01
Larger student groups and pressure on limited faculty time have raised the question of the learning value of merely observing simulation training in emergency medicine, instead of active team participation. The purpose of this study was to examine observers and hands-on participants' self-reported learning outcomes during simulation-based interprofessional team training regarding non-technical skills. In addition, we compared the learning outcomes for different professions and investigated team performance relative to the number of simulations in which they participated. A concurrent mixed-method design was chosen to evaluate the study, using questionnaires, observations, and focus group interviews. Participants included a total of 262 postgraduate and bachelor nursing students and medical students, organised into 44 interprofessional teams. The quantitative data showed that observers and participants had similar results in three of six predefined learning outcomes. The qualitative data emphasised the importance of participating in different roles, training several times, and training interprofessionally to enhance realism. Observing simulation training can be a valuable learning experience, but the students' preferred hands-on participation and learning by doing. For this reason, one can legitimise the observer role, given the large student groups and limited faculty time, as long as the students are also given some opportunity for hands-on participation in order to become more confident in their professional roles.
NASA Astrophysics Data System (ADS)
Allen, D. M.; Henry, C.; Demon, H.; Kirste, D. M.; Huang, J.
2011-12-01
Sustainable management of groundwater resources, particularly in water stressed regions, requires estimates of groundwater recharge. This study in southern Mali, Africa compares approaches for estimating groundwater recharge and understanding recharge processes using a variety of methods encompassing groundwater level-climate data analysis, GRACE satellite data analysis, and recharge modelling for current and future climate conditions. Time series data for GRACE (2002-2006) and observed groundwater level data (1982-2001) do not overlap. To overcome this problem, GRACE time series data were appended to the observed historical time series data, and the records compared. Terrestrial water storage anomalies from GRACE were corrected for soil moisture (SM) using the Global Land Data Assimilation System (GLDAS) to obtain monthly groundwater storage anomalies (GRACE-SM), and monthly recharge estimates. Historical groundwater storage anomalies and recharge were determined using the water table fluctuation method using observation data from 15 wells. Historical annual recharge averaged 145.0 mm (or 15.9% of annual rainfall) and compared favourably with the GRACE-SM estimate of 149.7 mm (or 14.8% of annual rainfall). Both records show lows and peaks in May and September, respectively; however, the peak for the GRACE-SM data is shifted later in the year to November, suggesting that the GLDAS may poorly predict the timing of soil water storage in this region. Recharge simulation results show good agreement between the timing and magnitude of the mean monthly simulated recharge and the regional mean monthly storage anomaly hydrograph generated from all monitoring wells. Under future climate conditions, annual recharge is projected to decrease by 8% for areas with luvisols and by 11% for areas with nitosols. Given this potential reduction in groundwater recharge, there may be added stress placed on an already stressed resource.
The Sea Breeze in South-Iceland: Observations with an unmanned aircraft and numerical simulations
NASA Astrophysics Data System (ADS)
Opsanger Jonassen, Marius; Ólafsson, Haraldur; Rasol, Dubravka; Reuder, Joachim
2010-05-01
Sea breeze events, 19-20 July 2009, observed during the international field campaign MOSO, at the southcoast of Iceland, have been investigated using high resolution numerical simulations. Thanks to the use of a small unmanned aircraft system (UAS), SUMO, the wind and temperature aloft could be observed at a high resolution in both space and time. Simultaneously with the UAS operations, conventional platforms were used to obtain surface measurements. The observations show a distinct sea breeze circulation with an onset at around noon and a final decay around 19:00 UTC. At the maximum, the sea breeze layer reached a height of appr. 400 m, marked by a capping wind minimum. When compared to the flow aloft, the sea breeze layer was found to exhibit relatively low temperatures and an expected turn from an off-shore to an on-shore flow. Overall, the agreement between the observations and simulations are relatively good. The simulations suggest a horizontal extent of the circulation some 20-30 km off-shore, but only around 5 km on-shore.
Reconstructing the ideal results of a perturbed analog quantum simulator
NASA Astrophysics Data System (ADS)
Schwenk, Iris; Reiner, Jan-Michael; Zanker, Sebastian; Tian, Lin; Leppäkangas, Juha; Marthaler, Michael
2018-04-01
Well-controlled quantum systems can potentially be used as quantum simulators. However, a quantum simulator is inevitably perturbed by coupling to additional degrees of freedom. This constitutes a major roadblock to useful quantum simulations. So far there are only limited means to understand the effect of perturbation on the results of quantum simulation. Here we present a method which, in certain circumstances, allows for the reconstruction of the ideal result from measurements on a perturbed quantum simulator. We consider extracting the value of the correlator 〈Ôi(t ) Ôj(0 ) 〉 from the simulated system, where Ôi are the operators which couple the system to its environment. The ideal correlator can be straightforwardly reconstructed by using statistical knowledge of the environment, if any n -time correlator of operators Ôi of the ideal system can be written as products of two-time correlators. We give an approach to verify the validity of this assumption experimentally by additional measurements on the perturbed quantum simulator. The proposed method can allow for reliable quantum simulations with systems subjected to environmental noise without adding an overhead to the quantum system.
NASA Astrophysics Data System (ADS)
Matsui, T.; Dolan, B.; Tao, W. K.; Rutledge, S. A.; Iguchi, T.; Barnum, J. I.; Lang, S. E.
2017-12-01
This study presents polarimetric radar characteristics of intense convective cores derived from observations as well as a polarimetric-radar simulator from cloud resolving model (CRM) simulations from Midlatitude Continental Convective Clouds Experiment (MC3E) May 23 case over Oklahoma and a Tropical Warm Pool-International Cloud Experiment (TWP-ICE) Jan 23 case over Darwin, Australia to highlight the contrast between continental and maritime convection. The POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS) is a state-of-art T-matrix-Mueller-Matrix-based polarimetric radar simulator that can generate synthetic polarimetric radar signals (reflectivity, differential reflectivity, specific differential phase, co-polar correlation) as well as synthetic radar retrievals (precipitation, hydrometeor type, updraft velocity) through the consistent treatment of cloud microphysics and dynamics from CRMs. The Weather Research and Forecasting (WRF) model is configured to simulate continental and maritime severe storms over the MC3E and TWP-ICE domains with the Goddard bulk 4ICE single-moment microphysics and HUCM spectra-bin microphysics. Various statistical diagrams of polarimetric radar signals, hydrometeor types, updraft velocity, and precipitation intensity are investigated for convective and stratiform precipitation regimes and directly compared between MC3E and TWP-ICE cases. The result shows MC3E convection is characterized with very strong reflectivity (up to 60dBZ), slight negative differential reflectivity (-0.8 0 dB) and near-zero specific differential phase above the freezing levels. On the other hand, TWP-ICE convection shows strong reflectivity (up to 50dBZ), slight positive differential reflectivity (0 1.0 dB) and differential phase (0 0.8 dB/km). Hydrometeor IDentification (HID) algorithm from the observation and simulations detect hail-dominant convection core in MC3E, while graupel-dominant convection core in TWP-ICE. This land-ocean contrast
Observing System Simulations for ASCENDS: Synthesizing Science Measurement Requirements (Invited)
NASA Astrophysics Data System (ADS)
Kawa, S. R.; Baker, D. F.; Schuh, A. E.; Crowell, S.; Rayner, P. J.; Hammerling, D.; Michalak, A. M.; Wang, J. S.; Eluszkiewicz, J.; Ott, L.; Zaccheo, T.; Abshire, J. B.; Browell, E. V.; Moore, B.; Crisp, D.
2013-12-01
The measurement of atmospheric CO2 from space using active (lidar) sensing techniques has several potentially significant advantages in comparison to current and planned passive CO2 instruments. Application of this new technology aims to advance CO2 measurement capability and carbon cycle science into the next decade. The NASA Active Sensing of Carbon Emissions, Nights, Days, and Seasons (ASCENDS) mission has been recommended by the US National Academy of Sciences Decadal Survey for the next generation of space-based CO2 observing systems. ASCENDS is currently planned for launch in 2022. Several possible lidar instrument approaches have been demonstrated in airborne campaigns and the results indicate that such sensors are quite feasible. Studies are now underway to evaluate performance requirements for space mission implementation. Satellite CO2 observations must be highly precise and unbiased in order to accurately infer global carbon source/sink fluxes. Measurement demands are likely to further increase in the wake of GOSAT, OCO-2, and enhanced ground-based in situ and remote sensing CO2 data. The objective of our work is to quantitatively and consistently evaluate the measurement capabilities and requirements for ASCENDS in the context of advancing our knowledge of carbon flux distributions and their dependence on underlying physical processes. Considerations include requirements for precision, relative accuracy, spatial/temporal coverage and resolution, vertical information content, interferences, and possibly the tradeoffs among these parameters, while at the same time framing a mission that can be implemented within a constrained budget. Here, we attempt to synthesize the results of observing system simulation studies, commissioned by the ASCENDS Science Requirements Definition Team, into a coherent set of mission performance guidelines. A variety of forward and inverse model frameworks are employed to reduce the potential dependence of the results on model
NASA Technical Reports Server (NTRS)
Matsui, Toshihisa; Zeng, Xiping; Tao, Wei-Kuo; Masunaga, Hirohiko; Olson, William S.; Lang, Stephen
2008-01-01
This paper proposes a methodology known as the Tropical Rainfall Measuring Mission (TRMM) Triple-Sensor Three-step Evaluation Framework (T3EF) for the systematic evaluation of precipitating cloud types and microphysics in a cloud-resolving model (CRM). T3EF utilizes multi-frequency satellite simulators and novel statistics of multi-frequency radiance and backscattering signals observed from the TRMM satellite. Specifically, T3EF compares CRM and satellite observations in the form of combined probability distributions of precipitation radar (PR) reflectivity, polarization-corrected microwave brightness temperature (Tb), and infrared Tb to evaluate the candidate CRM. T3EF is used to evaluate the Goddard Cumulus Ensemble (GCE) model for cases involving the South China Sea Monsoon Experiment (SCSMEX) and Kwajalein Experiment (KWAJEX). This evaluation reveals that the GCE properly captures the satellite-measured frequencies of different precipitating cloud types in the SCSMEX case but underestimates the frequencies of deep convective and deep stratiform types in the KWAJEX case. Moreover, the GCE tends to simulate excessively large and abundant frozen condensates in deep convective clouds as inferred from the overestimated GCE-simulated radar reflectivities and microwave Tb depressions. Unveiling the detailed errors in the GCE s performance provides the best direction for model improvements.
NASA Astrophysics Data System (ADS)
Bzowski, M.; Kubiak, M. A.; Hlond, M.; Moebius, E.; Leonard, T.; Heirtzler, D.; Kucharek, H.; Bochsler, P. A.; Schwadron, N. A.; Crew, G. B.; McComas, D. J.; Fuselier, S. A.
2010-12-01
lower by ≈4 km/s. The simulations appear to agree with the IBEX observations slightly better for the different inflow direction. The results obtained separately from the two passes through the He flow (in 2009 and 2010) are identical within observational uncertainties. Potential reasons for the differences from previous results will be discussed. Any modifications in these critical inflow parameters will require modification of current global heliosphere models. In particular, a reduced flow speed and thus reduced ram pressure would require an increase in the total LIC density and/or the magnetic field strength to maintain pressure balance at the heliopause.
NASA Astrophysics Data System (ADS)
Baushev, A. N.; del Valle, L.; Campusano, L. E.; Escala, A.; Muñoz, R. R.; Palma, G. A.
2017-05-01
Galaxy observations and N-body cosmological simulations produce conflicting dark matter halo density profiles for galaxy central regions. While simulations suggest a cuspy and universal density profile (UDP) of this region, the majority of observations favor variable profiles with a core in the center. In this paper, we investigate the convergency of standard N-body simulations, especially in the cusp region, following the approach proposed by [1]. We simulate the well known Hernquist model using the SPH code Gadget-3 and consider the full array of dynamical parameters of the particles. We find that, although the cuspy profile is stable, all integrals of motion characterizing individual particles suffer strong unphysical variations along the whole halo, revealing an effective interaction between the test bodies. This result casts doubts on the reliability of the velocity distribution function obtained in the simulations. Moreover, we find unphysical Fokker-Planck streams of particles in the cusp region. The same streams should appear in cosmological N-body simulations, being strong enough to change the shape of the cusp or even to create it. Our analysis, based on the Hernquist model and the standard SPH code, strongly suggests that the UDPs generally found by the cosmological N-body simulations may be a consequence of numerical effects. A much better understanding of the N-body simulation convergency is necessary before a `core-cusp problem' can properly be used to question the validity of the CDM model.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Baushev, A.N.; Valle, L. del; Campusano, L.E.
2017-05-01
Galaxy observations and N-body cosmological simulations produce conflicting dark matter halo density profiles for galaxy central regions. While simulations suggest a cuspy and universal density profile (UDP) of this region, the majority of observations favor variable profiles with a core in the center. In this paper, we investigate the convergency of standard N-body simulations, especially in the cusp region, following the approach proposed by [1]. We simulate the well known Hernquist model using the SPH code Gadget-3 and consider the full array of dynamical parameters of the particles. We find that, although the cuspy profile is stable, all integrals ofmore » motion characterizing individual particles suffer strong unphysical variations along the whole halo, revealing an effective interaction between the test bodies. This result casts doubts on the reliability of the velocity distribution function obtained in the simulations. Moreover, we find unphysical Fokker-Planck streams of particles in the cusp region. The same streams should appear in cosmological N-body simulations, being strong enough to change the shape of the cusp or even to create it. Our analysis, based on the Hernquist model and the standard SPH code, strongly suggests that the UDPs generally found by the cosmological N-body simulations may be a consequence of numerical effects. A much better understanding of the N-body simulation convergency is necessary before a 'core-cusp problem' can properly be used to question the validity of the CDM model.« less
Analysis of Voyager Observed High-Energy Electron Fluxes in the Heliosheath Using MHD Simulations
NASA Technical Reports Server (NTRS)
Washimi, Haruichi; Webber, W. R.; Zank, Gary P.; Hu, Qiang; Florinski, Vladimir; Adams, James; Kubo, Yuki
2011-01-01
The Voyager spacecraft (V1 and V2) observed electrons of 6-14 MeV in the heliosheath which showed several incidences of flux variation relative to a background of gradually increasing flux with distance from the Sun. The increasing flux of background electrons is thought to result from inward radial diffusion. We compare the temporal electron flux variation with dynamical phenomena in the heliosheath that are obtained from our MHD simulations. Because our simulation is based on V2 observed plasma data before V2 crossed the termination shock, this analysis is effective up to late 2008, i.e., about a year after the V2-crossing, during which disturbances, driven prior to the crossing time, survived in the heliosheath. Several electron flux variations correspond to times directly associated with interplanetary shock events. One noteworthy example corresponds to various times associated with the March 2006 interplanetary shock, these being the collision with the termination shock, the passage past the V1 spacecraft, and the collision with the region near the heliopause, as identified by W.R. Webber et al. for proton/helium of 7-200 MeV. Our simulations indicate that all other electron flux variations, except one, correspond well to the times when a shock-driven magneto-sonic pulse and its reflection in the heliosheath either passed across V1/V2, or collided with the termination shock or with the plasma sheet near the heliopause. This result suggests that variation in the electron flux should be due to either direct or indirect effects of magnetosonic pulses in the heliosheath driven by interplanetary shocks
The effect of AGN feedback on the X-ray morphologies of clusters: Simulations vs. observations
NASA Astrophysics Data System (ADS)
Chon, Gayoung; Puchwein, Ewald; Böhringer, Hans
2016-07-01
Clusters of galaxies probe the large-scale distribution of matter and are a useful tool to test the cosmological models by constraining cosmic structure growth and the expansion of the Universe. It is the scaling relations between mass observables and the true mass of a cluster through which we obtain the cosmological constraints by comparing to theoretical cluster mass functions. These scaling relations are, however, heavily influenced by cluster morphology. The presence of the slight tension in recent cosmological constraints on Ωm and σ8 based on the CMB and clusters has boosted the interests in looking for possible sources for the discrepancy. Therefore we study here the effect of active galactic nucleus (AGN) feedback as one of the major mechanisms modifying the cluster morphology influencing scaling relations. It is known that AGN feedback injects energies up to 1062 erg into the intracluster medium, controls the heating and cooling of a cluster, and re-distributes cold gas from the centre to outer radii. We have also learned that cluster simulations with AGN feedback can reproduce observed cluster properties, for example, the X-ray luminosity, temperature, and cooling rate at the centre better than without the AGN feedback. In this paper using cosmological hydrodynamical simulations we investigate how the AGN feedback changes the X-ray morphology of the simulated systems, and compare this to the observed Representative XMM-Newton Cluster Structure Survey (REXCESS) clusters. We apply two substructure measures, centre shifts (w) and power ratios (e.g. P3/P0), to characterise the cluster morphology, and find that our simulated clusters are more substructured than the observed clusters based on the values of w and P3/P0. We also show that the degree of this discrepancy is affected by the inclusion of AGN feedback. While the clusters simulated with the AGN feedback are in much better agreement with the REXCESS LX-T relation, they are also more substructured
Causes and implications of the growing divergence between climate model simulations and observations
NASA Astrophysics Data System (ADS)
Curry, Judith
2014-03-01
For the past 15+ years, there has been no increase in global average surface temperature, which has been referred to as a 'hiatus' in global warming. By contrast, estimates of expected warming in the first several decades of 21st century made by the IPCC AR4 were 0.2C/decade. This talk summarizes the recent CMIP5 climate model simulation results and comparisons with observational data. The most recent climate model simulations used in the AR5 indicate that the warming stagnation since 1998 is no longer consistent with model projections even at the 2% confidence level. Potential causes for the model-observation discrepancies are discussed. A particular focus of the talk is the role of multi-decadal natural internal variability on the climate variability of the 20th and early 21st centuries. The ``stadium wave'' climate signal is described, which propagates across the Northern Hemisphere through a network of ocean, ice, and atmospheric circulation regimes that self-organize into a collective tempo. The stadium wave hypothesis provides a plausible explanation for the hiatus in warming and helps explain why climate models did not predict this hiatus. Further, the new hypothesis suggests how long the hiatus might last. Implications of the hiatus are discussed in context of climate model sensitivity to CO2 forcing and attribution of the warming that was observed in the last quarter of the 20th century.
Observation and numerical simulation of a convective initiation during COHMEX
NASA Technical Reports Server (NTRS)
Song, J. Aaron; Kaplan, Michael L.
1991-01-01
Under a synoptically undisturbed condition, a dual-peak convective lifecycle was observed with the COoperative Huntsville Meteorological EXperiment (COHMEX) observational network over a 24-hour period. The lifecycle included a multicell storm, which lasted about 6 hours, produced a peak rainrate exceeding 100 mm/hr, and initiated a downstream mesoscale convective system. The 24-hour accumulated rainfall of this event was the largest during the entire COHMEX. The downstream mesoscale convective system, unfortunately, was difficult to investigate quantitatively due to the lack of mesoscale observations. The dataset collected near the time of the multicell storm evolution, including its initiation, was one of the best datasets of COHMEX. In this study, the initiation of this multicell storm is chosen as the target of the numerical simulations.
DoSSiER: Database of scientific simulation and experimental results
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wenzel, Hans; Yarba, Julia; Genser, Krzystof
The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER can be easily accessed via a web application. In addition, a web service allows for programmatic access to the repository to extract records in json or xml exchange formats. In this paper, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.
DoSSiER: Database of scientific simulation and experimental results
Wenzel, Hans; Yarba, Julia; Genser, Krzystof; ...
2016-08-01
The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER can be easily accessed via a web application. In addition, a web service allows for programmatic access to the repository to extract records in json or xml exchange formats. In this paper, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.
NASA Astrophysics Data System (ADS)
Kim, Minwoo; Park, Hyeon K.; Yun, Gunsu; Lee, Jaehyun; Lee, Jieun; Lee, Woochang; Jardin, Stephen; Xu, X. Q.; Kstar Team
2015-11-01
The modeling of the Edge-localized-mode (ELM) should be rigorously pursued for reliable and robust ELM control for steady-state long-pulse H-mode operation in ITER as well as DEMO. In the KSTAR discharge #7328, a linear stability of the ELMs is investigated using M3D-C1 and BOUT + + codes. This is achieved by linear simulation for the n = 8 mode structure of the ELM observed by the KSTAR electron cyclotron emission imaging (ECEI) systems. In the process of analysis, variations due to the plasma equilibrium profiles and transport coefficients on the ELM growth rate are investigated and simulation results with the two codes are compared. The numerical simulations are extended to nonlinear phase of the ELM dynamics, which includes saturation and crash of the modes. Preliminary results of the nonlinear simulations are compared with the measured images especially from the saturation to the crash. This work is supported by NRF of Korea under contract no. NRF-2014M1A7A1A03029865, US DoE by LLNL under contract DE-AC52-07NA27344 and US DoE by PPPL under contract DE-AC02-09CH11466.
Thin films structural properties: results of the full-atomistic supercomputer simulation
NASA Astrophysics Data System (ADS)
Grigoriev, F. V.; Sulimov, V. B.; Tikhonravov, A. V.
2017-12-01
The previously developed full-atomistic approach to the thin film growth simulation is applied for the investigation of the dependence of silicon dioxide films properties on deposition conditions. It is shown that the surface roughness and porosity are essentially reduced with the growth of energy of deposited silicon atoms. The growth of energy from 0.1 eV to 10 eV results in the increase of the film density for 0.2 - 0.4 g/cm3 and of the refractive index for 0.04-0.08. The compressive stress in films structures is observed for all deposition conditions. Absolute values of the stress tensor components increase with the growth of e energy of deposited atoms. The increase of the substrate temperature results in smoothing of the density profiles of the deposited films.
Generalizing Observational Study Results: Applying Propensity Score Methods to Complex Surveys
DuGoff, Eva H; Schuler, Megan; Stuart, Elizabeth A
2014-01-01
ObjectiveTo provide a tutorial for using propensity score methods with complex survey data. Data SourcesSimulated data and the 2008 Medical Expenditure Panel Survey. Study DesignUsing simulation, we compared the following methods for estimating the treatment effect: a naïve estimate (ignoring both survey weights and propensity scores), survey weighting, propensity score methods (nearest neighbor matching, weighting, and subclassification), and propensity score methods in combination with survey weighting. Methods are compared in terms of bias and 95 percent confidence interval coverage. In Example 2, we used these methods to estimate the effect on health care spending of having a generalist versus a specialist as a usual source of care. Principal FindingsIn general, combining a propensity score method and survey weighting is necessary to achieve unbiased treatment effect estimates that are generalizable to the original survey target population. ConclusionsPropensity score methods are an essential tool for addressing confounding in observational studies. Ignoring survey weights may lead to results that are not generalizable to the survey target population. This paper clarifies the appropriate inferences for different propensity score methods and suggests guidelines for selecting an appropriate propensity score method based on a researcher’s goal. PMID:23855598
Observations of Crew Dynamics During Mars Analog Simulations
NASA Technical Reports Server (NTRS)
Cusack, Stacy L.
2009-01-01
Crewmembers on Mars missions will face new and unique challenges compared to those in close communications proximity to Mission Control centers. Crews on Mars will likely become more autonomous and responsible for their day-to-day planning. These explorers will need to make frequent real time decisions without the assistance of large ground support teams. Ground-centric control will no longer be an option due to the communications delays. As a result of the new decision making model, crew dynamics and leadership styles of future astronauts may become significantly different from the demands of today. As a volunteer for the Mars Society on two Mars analog missions, this presenter will discuss observations made during isolated, surface exploration simulations. The need for careful crew selections, not just based on individual skill sets, but on overall team interactions becomes apparent very quickly when the crew is planning their own days and deciding their own priorities. Even more important is the selection of a Mission Commander who can lead a team of highly skilled individuals with strong and varied opinions in a way that promotes crew consensus, maintains fairness, and prevents unnecessary crew fatigue.
NASA Technical Reports Server (NTRS)
Prigent, Catherine; Pardo, Juan R.; Mishchenko, Michael I.; Rossow, Willaim B.; Hansen, James E. (Technical Monitor)
2001-01-01
Special Sensor Microwave /Imager (SSM/I) observations in cloud systems are studied over the tropics. Over optically thick cloud systems, presence of polarized signatures at 37 and 85 GHz is evidenced and analyzed with the help of cloud top temperature and optical thickness extracted from visible and IR satellite observations. Scattering signatures at 85 GHz (TbV(85) less than or = 250 K) are associated with polarization differences greater than or = 6 K, approx. 50%, of the time over ocean and approx. 40% over land. In addition. over thick clouds the polarization difference at 37 GHz is rarely negligible. The polarization differences at 37 and 85 GHz do not stem from the surface but are generated in regions of relatively homogeneous clouds having high liquid water content. To interpret the observations, a radiative transfer model that includes the scattering by non-spherical particles is developed. based on the T-matrix approach and using the doubling and adding method. In addition to handling randomly and perfectly oriented particles, this model can also simulate the effect of partial orientation of the hydrometeors. Microwave brightness temperatures are simulated at SSM/I frequencies and are compared with the observations. Polarization differences of approx. 2 K can be simulated at 37 GHz over a rain layer, even using spherical drops. The polarization difference is larger for oriented non-spherical particles. The 85 GHz simulations are very sensitive to the ice phase of the cloud. Simulations with spherical particles or with randomly oriented non-spherical ice particles cannot replicate the observed polarization differences. However, with partially oriented non-spherical particles, the observed polarized signatures at 85 GHz are explained, and the sensitivity of the scattering characteristics to the particle size, asphericity, and orientation is analyzed. Implications on rain and ice retrievals are discussed.
Advanced Thermal Simulator Testing: Thermal Analysis and Test Results
NASA Technical Reports Server (NTRS)
Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe
2008-01-01
Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.
Wallace, John M.; Fu, Qiang; Smoliak, Brian V.; Lin, Pu; Johanson, Celeste M.
2012-01-01
A suite of the historical simulations run with the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) models forced by greenhouse gases, aerosols, stratospheric ozone depletion, and volcanic eruptions and a second suite of simulations forced by increasing CO2 concentrations alone are compared with observations for the reference interval 1965–2000. Surface air temperature trends are disaggregated by boreal cold (November-April) versus warm (May-October) seasons and by high latitude northern (N: 40°–90 °N) versus southern (S: 60 °S–40 °N) domains. A dynamical adjustment is applied to remove the component of the cold-season surface air temperature trends (over land areas poleward of 40 °N) that are attributable to changing atmospheric circulation patterns. The model simulations do not simulate the full extent of the wintertime warming over the high-latitude Northern Hemisphere continents during the later 20th century, much of which was dynamically induced. Expressed as fractions of the concurrent trend in global-mean sea surface temperature, the relative magnitude of the dynamically induced wintertime warming over domain N in the observations, the simulations with multiple forcings, and the runs forced by the buildup of greenhouse gases only is 7∶2∶1, and roughly comparable to the relative magnitude of the concurrent sea-level pressure trends. These results support the notion that the enhanced wintertime warming over high northern latitudes from 1965 to 2000 was mainly a reflection of unforced variability of the coupled climate system. Some of the simulations exhibit an enhancement of the warming along the Arctic coast, suggestive of exaggerated feedbacks. PMID:22847408
NASA Technical Reports Server (NTRS)
Prive, N. C.; Errico, R. M.; Tai, K.-S.
2013-01-01
The Global Modeling and Assimilation Office (GMAO) observing system simulation experiment (OSSE) framework is used to explore the response of analysis error and forecast skill to observation quality. In an OSSE, synthetic observations may be created that have much smaller error than real observations, and precisely quantified error may be applied to these synthetic observations. Three experiments are performed in which synthetic observations with magnitudes of applied observation error that vary from zero to twice the estimated realistic error are ingested into the Goddard Earth Observing System Model (GEOS-5) with Gridpoint Statistical Interpolation (GSI) data assimilation for a one-month period representing July. The analysis increment and observation innovation are strongly impacted by observation error, with much larger variances for increased observation error. The analysis quality is degraded by increased observation error, but the change in root-mean-square error of the analysis state is small relative to the total analysis error. Surprisingly, in the 120 hour forecast increased observation error only yields a slight decline in forecast skill in the extratropics, and no discernable degradation of forecast skill in the tropics.
NASA Technical Reports Server (NTRS)
Cole, Benjamin H.; Yang, Ping; Baum, Bryan A.; Riedi, Jerome; Labonnote, Laurent C.; Thieuleux, Francois; Platnick, Steven
2012-01-01
Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals.
New methods to benchmark simulations of accreting black holes systems against observations
NASA Astrophysics Data System (ADS)
Markoff, Sera; Chatterjee, Koushik; Liska, Matthew; Tchekhovskoy, Alexander; Hesp, Casper; Ceccobello, Chiara; Russell, Thomas
2017-08-01
The field of black hole accretion has been significantly advanced by the use of complex ideal general relativistic magnetohydrodynamics (GRMHD) codes, now capable of simulating scales from the event horizon out to ~10^5 gravitational radii at high resolution. The challenge remains how to test these simulations against data, because the self-consistent treatment of radiation is still in its early days, and is complicated by dependence on non-ideal/microphysical processes not yet included in the codes. On the other extreme, a variety of phenomenological models (disk, corona, jet, wind) can well-describe spectra or variability signatures in a particular waveband, although often not both. To bring these two methodologies together, we need robust observational “benchmarks” that can be identified and studied in simulations. I will focus on one example of such a benchmark, from recent observational campaigns on black holes across the mass scale: the jet break. I will describe new work attempting to understand what drives this feature by searching for regions that share similar trends in terms of dependence on accretion power or magnetisation. Such methods can allow early tests of simulation assumptions and help pinpoint which regions will dominate the light production, well before full radiative processes are incorporated, and will help guide the interpretation of, e.g. Event Horizon Telescope data.
NASA Astrophysics Data System (ADS)
Eriksson, S.; Cassak, P. A.; Retinò, A.; Mozer, F. S.
2016-04-01
The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 across a subsolar magnetopause that displayed a symmetric plasma density, but different out-of-plane magnetic field signatures for similar solar wind conditions. The first magnetopause crossing displayed a bipolar guide field variation in a weak external guide field consistent with a symmetric Hall field from a single X line. The subsequent crossing represents the first observation of a tripolar guide field perturbation at Earth's magnetopause in a strong guide field. This perturbation consists of a significant guide field enhancement between two narrow guide field depressions. A particle-in-cell simulation for the prevailing conditions across this second event resulted in a magnetic island between two simulated X lines across which a tripolar guide field developed consistent with the observation. The simulated island supports a scenario whereby Polar encountered the asymmetric quadrupole Hall magnetic fields between two X lines for symmetric conditions across the magnetopause.
Sea Surface Salinity Variability from Simulations and Observations: Preparing for Aquarius
NASA Technical Reports Server (NTRS)
Jacob, S. Daniel; LeVine, David M.
2010-01-01
Oceanic fresh water transport has been shown to play an important role in the global hydrological cycle. Sea surface salinity (SSS) is representative of the surface fresh water fluxes and the upcoming Aquarius mission scheduled to be launched in December 2010 will provide excellent spatial and temporal SSS coverage to better estimate the net exchange. In most ocean general circulation models, SSS is relaxed to climatology to prevent model drift. While SST remains a well observed variable, relaxing to SST reduces the range of SSS variability in the simulations (Fig.1). The main objective of the present study is to simulate surface tracers using a primitive equation ocean model for multiple forcing data sets to identify and establish a baseline SSS variability. The simulated variability scales are compared to those from near-surface argo salinity measurements.
Atmospheric Retrievals from Exoplanet Observations and Simulations with BART
NASA Astrophysics Data System (ADS)
Harrington, Joseph
the planet has uniform composition and the same temperature profile everywhere. We do not know this assumption's impact. While Spitzer and HST have few exoplanet observing modes, JWST will have over 20. Given the signal challenges and the complexity of retrieval, modeling the observations and data analysis is the best way to optimize an observing plan. Our project solves all of these problems. Using only open-source codes, with tools available to the community for their immediate application in JWST and HST proposals and analyses, we will produce a faithful simulator of 2D spectral and photometric frames from each JWST exoplanet mode (WFC3 spatial scan mode works already), including jitter and intrapixel effects. We will extract and calibrate data, analyzing them with BART. Given planetary input spectra for terrestrial, super-Earth, Neptune, and Jupiterclass planets, and a variety of stellar spectra, we will determine the best combination of observations to recover each atmosphere, and the limits where low SNR or spectral coverage produce deceptive results. To facilitate these analyses, we will adapt an existing cloud model to BART, add condensate code now being written to its thermochemical model, include scattering, add a 3D atmosphere module (for dayside occultation mapping and the 1D vs. 3D question), and improve performance and documentation, among other improvements. We will host a web site and community discussions online and at conferences about retrieval issues. We will develop validation tests for radiative-transfer and BART-style retrieval codes, and provide examples to validate others' codes. We will engage the retrieval community in data challenges. We will provide web-enabled tools to specify planets easily for modeling. We will make all of these tools, tests, and comparisons available online so everyone can use them to maximize NASA's investment in high-end observing capabilities to characterize exoplanets.
NASA Astrophysics Data System (ADS)
Kostenko, I. S.; Zaytsev, A. I.; Minaev, D. D.; Kurkin, A. A.; Pelinovsky, E. N.; Oshmarina, O. E.
2018-01-01
Observation data on the September 5, 1971, earthquake that occurred near the Moneron Island (Sakhalin) have been analyzed and a numerical simulation of the tsunami induced by this earthquake is conducted. The tsunami source identified in this study indicates that the observational data are in good agreement with the results of calculations performed on the basis of shallow-water equations.
NASA Technical Reports Server (NTRS)
Huang, Lei; Jiang, Jonathan H.; Murray, Lee T.; Damon, Megan R.; Su, Hui; Livesey, Nathaniel J.
2016-01-01
This study evaluates the distribution and variation of carbon monoxide (CO) in the upper troposphere and lower stratosphere (UTLS) during 2004-2012 as simulated by two chemical transport models, using the latest version of Aura Microwave Limb Sounder (MLS) observations. The simulated spatial distributions, temporal variations and vertical transport of CO in the UTLS region are compared with those observed by MLS. We also investigate the impact of surface emissions and deep convection on CO concentrations in the UTLS over different regions, using both model simulations and MLS observations. Global Modeling Initiative (GMI) and GEOS-Chem simulations of UTLS CO both show similar spatial distributions to observations. The global mean CO values simulated by both models agree with MLS observations at 215 and 147 hPa, but are significantly underestimated by more than 40% at 100 hPa. In addition, the models underestimate the peak CO values by up to 70% at 100 hPa, 60% at 147 hPa and 40% at 215 hPa, with GEOS-Chem generally simulating more CO at 100 hPa and less CO at 215 hPa than GMI. The seasonal distributions of CO simulated by both models are in better agreement with MLS in the Southern Hemisphere (SH) than in the Northern Hemisphere (NH), with disagreements between model and observations over enhanced CO regions such as southern Africa. The simulated vertical transport of CO shows better agreement with MLS in the tropics and the SH subtropics than the NH subtropics. We also examine regional variations in the relationships among surface CO emission, convection and UTLS CO concentrations. The two models exhibit emission-convection- CO relationships similar to those observed by MLS over the tropics and some regions with enhanced UTLS CO.
Evaluation of Precipitation Simulated by Seven SCMs against the ARM Observations at the SGP Site
NASA Technical Reports Server (NTRS)
Song, Hua; Lin, Wuyin; Lin, Yanluan; Wolf, Audrey B.; Neggers, Roel; Donner, Leo J.; Del Genio, Anthony D.; Liu, Yangang
2013-01-01
This study evaluates the performances of seven single-column models (SCMs) by comparing simulated surface precipitation with observations at the Atmospheric Radiation Measurement Program Southern Great Plains (SGP) site from January 1999 to December 2001. Results show that although most SCMs can reproduce the observed precipitation reasonably well, there are significant and interesting differences in their details. In the cold season, the model-observation differences in the frequency and mean intensity of rain events tend to compensate each other for most SCMs. In the warm season, most SCMs produce more rain events in daytime than in nighttime, whereas the observations have more rain events in nighttime. The mean intensities of rain events in these SCMs are much stronger in daytime, but weaker in nighttime, than the observations. The higher frequency of rain events during warm-season daytime in most SCMs is related to the fact that most SCMs produce a spurious precipitation peak around the regime of weak vertical motions but rich in moisture content. The models also show distinct biases between nighttime and daytime in simulating significant rain events. In nighttime, all the SCMs have a lower frequency of moderate-to-strong rain events than the observations for both seasons. In daytime, most SCMs have a higher frequency of moderate-to-strong rain events than the observations, especially in the warm season. Further analysis reveals distinct meteorological backgrounds for large underestimation and overestimation events. The former occur in the strong ascending regimes with negative low-level horizontal heat and moisture advection, whereas the latter occur in the weak or moderate ascending regimes with positive low-level horizontal heat and moisture advection.
Computer simulation results of attitude estimation of earth orbiting satellites
NASA Technical Reports Server (NTRS)
Kou, S. R.
1976-01-01
Computer simulation results of attitude estimation of Earth-orbiting satellites (including Space Telescope) subjected to environmental disturbances and noises are presented. Decomposed linear recursive filter and Kalman filter were used as estimation tools. Six programs were developed for this simulation, and all were written in the basic language and were run on HP 9830A and HP 9866A computers. Simulation results show that a decomposed linear recursive filter is accurate in estimation and fast in response time. Furthermore, for higher order systems, this filter has computational advantages (i.e., less integration errors and roundoff errors) over a Kalman filter.
Welsher, Arthur; Rojas, David; Khan, Zain; VanderBeek, Laura; Kapralos, Bill; Grierson, Lawrence E M
2018-02-01
Research has revealed that individuals can improve technical skill performance by viewing demonstrations modeled by either expert or novice performers. These findings support the development of video-based observational practice communities that augment simulation-based skill education and connect geographically distributed learners. This study explores the experimental replicability of the observational learning effect when demonstrations are sampled from a community of distributed learners and serves as a context for understanding learner experiences within this type of training protocol. Participants from 3 distributed medical campuses engaged in a simulation-based learning study of the elliptical excision in which they completed a video-recorded performance before being assigned to 1 of 3 groups for a 2-week observational practice intervention. One group observed expert demonstrations, another observed novice demonstrations, and the third observed a combination of both. Participants returned for posttesting immediately and 1 month after the intervention. Participants also engaged in interviews regarding their perceptions of the usability and relevance of video-based observational practice to clinical education. Checklist (P < 0.0001) and global rating (P < 0.0001) measures indicate that participants, regardless of group assignment, improved after the intervention and after a 1-month retention period. Analyses revealed no significant differences between groups. Qualitative analyses indicate that participants perceived the observational practice platform to be usable, relevant, and potentially improved with enhanced feedback delivery. Video-based observational practice involving expert and/or novice demonstrations enhances simulation-based skill learning in a group of geographically distributed trainees. These findings support the use of Internet-mediated observational learning communities in distributed and simulation-based medical education contexts.
NASA Technical Reports Server (NTRS)
Kemp, E.; Jacob, J.; Rosenberg, R.; Jusem, J. C.; Emmitt, G. D.; Wood, S.; Greco, L. P.; Riishojgaard, L. P.; Masutani, M.; Ma, Z.;
2013-01-01
NASA Goddard Space Flight Center's Software Systems Support Office (SSSO) is participating in a multi-agency study of the impact of assimilating Doppler wind lidar observations on numerical weather prediction. Funded by NASA's Earth Science Technology Office, SSSO has worked with Simpson Weather Associates to produce time series of synthetic lidar observations mimicking the OAWL and WISSCR lidar instruments deployed on the International Space Station. In addition, SSSO has worked to assimilate a portion of these observations those drawn from the NASA fvGCM Nature Run into the NASA GEOS-DAS global weather prediction system in a series of Observing System Simulation Experiments (OSSEs). These OSSEs will complement parallel OSSEs prepared by the Joint Center for Satellite Data Assimilation and by NOAA's Atlantic Oceanographic and Meteorological Laboratory. In this talk, we will describe our procedure and provide available OSSE results.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan
2016-12-01
The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to variable VLBI data, in order to infer model parameters and perform model comparisons. We use mock EHT data based on GRMHD simulations to explore themore » robustness of this Bayesian method and contrast it to approaches that do not consider the effects of variability. We find that time-independent models lead to offset values of the inferred parameters with artificially reduced uncertainties. Moreover, neglecting the variability in the data and the models often leads to erroneous model selections. We finally apply our method to the early EHT data on Sgr A*.« less
NASA Astrophysics Data System (ADS)
Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan; Medeiros, Lia; Özel, Feryal; Psaltis, Dimitrios
2016-12-01
The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to variable VLBI data, in order to infer model parameters and perform model comparisons. We use mock EHT data based on GRMHD simulations to explore the robustness of this Bayesian method and contrast it to approaches that do not consider the effects of variability. We find that time-independent models lead to offset values of the inferred parameters with artificially reduced uncertainties. Moreover, neglecting the variability in the data and the models often leads to erroneous model selections. We finally apply our method to the early EHT data on Sgr A*.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dolly, S; Mutic, S; Anastasio, M
Purpose: Traditionally, image quality in radiation therapy is assessed subjectively or by utilizing physically-based metrics. Some model observers exist for task-based medical image quality assessment, but almost exclusively for diagnostic imaging tasks. As opposed to disease diagnosis, the task for image observers in radiation therapy is to utilize the available images to design and deliver a radiation dose which maximizes patient disease control while minimizing normal tissue damage. The purpose of this study was to design and implement a new computer simulation model observer to enable task-based image quality assessment in radiation therapy. Methods: A modular computer simulation framework wasmore » developed to resemble the radiotherapy observer by simulating an end-to-end radiation therapy treatment. Given images and the ground-truth organ boundaries from a numerical phantom as inputs, the framework simulates an external beam radiation therapy treatment and quantifies patient treatment outcomes using the previously defined therapeutic operating characteristic (TOC) curve. As a preliminary demonstration, TOC curves were calculated for various CT acquisition and reconstruction parameters, with the goal of assessing and optimizing simulation CT image quality for radiation therapy. Sources of randomness and bias within the system were analyzed. Results: The relationship between CT imaging dose and patient treatment outcome was objectively quantified in terms of a singular value, the area under the TOC (AUTOC) curve. The AUTOC decreases more rapidly for low-dose imaging protocols. AUTOC variation introduced by the dose optimization algorithm was approximately 0.02%, at the 95% confidence interval. Conclusion: A model observer has been developed and implemented to assess image quality based on radiation therapy treatment efficacy. It enables objective determination of appropriate imaging parameter values (e.g. imaging dose). Framework flexibility allows for
NASA Astrophysics Data System (ADS)
Tripathi, O. P.; Godin-Beekmann, S.; Lefevre, F.; Marchand, M.; Pazmino, A.; Hauchecorne, A.
2005-12-01
Model simulations of ozone loss rates during recent arctic and Antarctic winters are compared with the observed ozone loss rates from the match technique. Arctic winters 1994/1995, 1999/2000, 2002/2003 and the Antarctic winter 2003 were considered for the analysis. We use a high resolution chemical transport model MIMOSA-CHIM and REPROBUS box model for the calculation of ozone loss rates. Trajectory model calculations show that the ozone loss rates are dependent on the initialization fields. On the one hand when chemical fields are initialized by UCAM (University of Cambridge SLIMCAT model simulated fields) the loss rates were underestimated by a factor of two whereas on the other hand when it is initialized by UL (University of Leeds) fields the model loss rates are in a very good agreement with match loss rates at lower levels. The study shows a very good agreement between MIMOSA-CHIM simulation and match observation in 1999/2000 winter at both levels, 450 and 500 K, except slight underestimation in March at 500 K. But in January we have a very good agreement. This is also true for 1994/1995 when we consider simulated ozone loss rate in view of the ECMWF wind deficiency assuming that match observations were not made on isolated trajectories. Sensitivity tests, by changing JCl2O2 value, particle number density and heating rates, performed for the arctic winter 1999/2000 shows that we need to improve our understanding of particle number density and heating rate calculation mechanism. Burkholder JCl2O2 has improved the comparison of MIMOSA-CHIM model results with observations (Tripathi et al., 2005). In the same study the comparison results were shown to improved by changing heating rates and number density through NAT particle sedimentation.
NASA Astrophysics Data System (ADS)
Mehran, A.; AghaKouchak, A.; Phillips, T. J.
2014-02-01
The objective of this study is to cross-validate 34 Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations of precipitation against the Global Precipitation Climatology Project (GPCP) data, quantifying model pattern discrepancies, and biases for both entire distributions and their upper tails. The results of the volumetric hit index (VHI) analysis of the total monthly precipitation amounts show that most CMIP5 simulations are in good agreement with GPCP patterns in many areas but that their replication of observed precipitation over arid regions and certain subcontinental regions (e.g., northern Eurasia, eastern Russia, and central Australia) is problematical. Overall, the VHI of the multimodel ensemble mean and median also are superior to that of the individual CMIP5 models. However, at high quantiles of reference data (75th and 90th percentiles), all climate models display low skill in simulating precipitation, except over North America, the Amazon, and Central Africa. Analyses of total bias (B) in CMIP5 simulations reveal that most models overestimate precipitation over regions of complex topography (e.g., western North and South America and southern Africa and Asia), while underestimating it over arid regions. Also, while most climate model simulations show low biases over Europe, intermodel variations in bias over Australia and Amazonia are considerable. The quantile bias analyses indicate that CMIP5 simulations are even more biased at high quantiles of precipitation. It is found that a simple mean field bias removal improves the overall B and VHI values but does not make a significant improvement at high quantiles of precipitation.
NASA Technical Reports Server (NTRS)
Shie, C.-L.; Tao, W.-K.; Hou, A.; Lin, X.
2006-01-01
The GCE (Goddard Cumulus Ensemble) model, which has been developed and improved at NASA Goddard Space Flight Center over the past two decades, is considered as one of the finer and state-of-the-art CRMs (Cloud Resolving Models) in the research community. As the chosen CRM for a NASA Interdisciplinary Science (IDS) Project, GCE has recently been successfully upgraded into an MPI (Message Passing Interface) version with which great improvement has been achieved in computational efficiency, scalability, and portability. By basically using the large-scale temperature and moisture advective forcing, as well as the temperature, water vapor and wind fields obtained from TRMM (Tropical Rainfall Measuring Mission) field experiments such as SCSMEX (South China Sea Monsoon Experiment) and KWAJEX (Kwajalein Experiment), our recent 2-D and 3-D GCE simulations were able to capture detailed convective systems typical of the targeted (simulated) regions. The GEOS-3 [Goddard EOS (Earth Observing System) Version-3] reanalysis data have also been proposed and successfully implemented for usage in the proposed/performed GCE long-term simulations (i.e., aiming at producing massive simulated cloud data -- Cloud Library) in compensating the scarcity of real field experimental data in both time and space (location). Preliminary 2-D or 3-D pilot results using GEOS-3 data have generally showed good qualitative agreement (yet some quantitative difference) with the respective numerical results using the SCSMEX observations. The first objective of this paper is to ensure the GEOS-3 data quality by comparing the model results obtained from several pairs of simulations using the real observations and GEOS-3 reanalysis data. The different large-scale advective forcing obtained from these two kinds of resources (i.e., sounding observations and GEOS-3 reanalysis) has been considered as a major critical factor in producing various model results. The second objective of this paper is therefore to
Simulations of Galactic polarized synchrotron emission for Epoch of Reionization observations
NASA Astrophysics Data System (ADS)
Spinelli, M.; Bernardi, G.; Santos, M. G.
2018-06-01
The detection of the redshifted cosmological 21 cm line signal requires the removal of the Galactic and extragalactic foreground emission, which is orders of magnitude brighter anywhere in the sky. Foreground cleaning methods currently used are efficient in removing spectrally smooth components. However, they struggle in the presence of not spectrally smooth contamination that is, therefore, potentially the most dangerous one. An example of this is the polarized synchrotron emission, which is Faraday rotated by the interstellar medium and leaks into total intensity due to instrumental imperfections. In this work we present new full-sky simulations of this polarized synchrotron emission in the 50 - 200 MHz range, obtained from the observed properties of diffuse polarized emission at low frequencies. The simulated polarized maps are made publicly available, aiming to provide more realistic templates to simulate the effect of instrumental leakage and the effectiveness of foreground separation techniques.
XIMPOL: a new x-ray polarimetry observation-simulation and analysis framework
NASA Astrophysics Data System (ADS)
Omodei, Nicola; Baldini, Luca; Pesce-Rollins, Melissa; di Lalla, Niccolò
2017-08-01
We present a new simulation framework, XIMPOL, based on the python programming language and the Scipy stack, specifically developed for X-ray polarimetric applications. XIMPOL is not tied to any specific mission or instrument design and is meant to produce fast and yet realistic observation-simulations, given as basic inputs: (i) an arbitrary source model including morphological, temporal, spectral and polarimetric information, and (ii) the response functions of the detector under study, i.e., the effective area, the energy dispersion, the point-spread function and the modulation factor. The format of the response files is OGIP compliant, and the framework has the capability of producing output files that can be directly fed into the standard visualization and analysis tools used by the X-ray community, including XSPEC which make it a useful tool not only for simulating physical systems, but also to develop and test end-to-end analysis chains.
Molecular Simulation Results on Charged Carbon Nanotube Forest-Based Supercapacitors.
Muralidharan, Ajay; Pratt, Lawrence R; Hoffman, Gary G; Chaudhari, Mangesh I; Rempe, Susan B
2018-06-22
Electrochemical double-layer capacitances of charged carbon nanotube (CNT) forests with tetraethyl ammonium tetrafluoro borate electrolyte in propylene carbonate are studied on the basis of molecular dynamics simulation. Direct molecular simulation of the filling of pore spaces of the forest is feasible even with realistic, small CNT spacings. The numerical solution of the Poisson equation based on the extracted average charge densities then yields a regular experimental dependence on the width of the pore spaces, in contrast to the anomalous pattern observed in experiments on other carbon materials and also in simulations on planar slot-like pores. The capacitances obtained have realistic magnitudes but are insensitive to electric potential differences between the electrodes in this model. This agrees with previous calculations on CNT forest supercapacitors, but not with experiments which have suggested electrochemical doping for these systems. Those phenomena remain for further theory/modeling work. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Simulation of diurnal thermal energy storage systems: Preliminary results
NASA Astrophysics Data System (ADS)
Katipamula, S.; Somasundaram, S.; Williams, H. R.
1994-12-01
This report describes the results of a simulation of thermal energy storage (TES) integrated with a simple-cycle gas turbine cogeneration system. Integrating TES with cogeneration can serve the electrical and thermal loads independently while firing all fuel in the gas turbine. The detailed engineering and economic feasibility of diurnal TES systems integrated with cogeneration systems has been described in two previous PNL reports. The objective of this study was to lay the ground work for optimization of the TES system designs using a simulation tool called TRNSYS (TRaNsient SYstem Simulation). TRNSYS is a transient simulation program with a sequential-modular structure developed at the Solar Energy Laboratory, University of Wisconsin-Madison. The two TES systems selected for the base-case simulations were: (1) a one-tank storage model to represent the oil/rock TES system; and (2) a two-tank storage model to represent the molten nitrate salt TES system. Results of the study clearly indicate that an engineering optimization of the TES system using TRNSYS is possible. The one-tank stratified oil/rock storage model described here is a good starting point for parametric studies of a TES system. Further developments to the TRNSYS library of available models (economizer, evaporator, gas turbine, etc.) are recommended so that the phase-change processes is accurately treated.
Comparison between simulations and lab results on the ASSIST test-bench
NASA Astrophysics Data System (ADS)
Le Louarn, Miska; Madec, Pierre-Yves; Kolb, Johann; Paufique, Jerome; Oberti, Sylvain; La Penna, Paolo; Arsenault, Robin
2016-07-01
We present the latest comparison results between laboratory tests carried out on the ASSIST test bench and Octopus end-to end simulations. We simulated, as closely to the lab conditions as possible, the different AOF modes (Maintenance and commissioning mode (SCAO), GRAAL (GLAO in the near IR), Galacsi Wide Field mode (GLAO in the visible) and Galacsi narrow field mode (LTAO in the visible)). We then compared the simulation results to the ones obtained on the lab bench. Several aspects were investigated, like number of corrected modes, turbulence wind speeds, LGS photon flux etc. The agreement between simulations and lab is remarkably good for all investigated parameters, giving great confidence in both simulation tool and performance of the AO system in the lab.
Numerical simulations of catastrophic disruption: Recent results
NASA Technical Reports Server (NTRS)
Benz, W.; Asphaug, E.; Ryan, E. V.
1994-01-01
Numerical simulations have been used to study high velocity two-body impacts. In this paper, a two-dimensional Largrangian finite difference hydro-code and a three-dimensional smooth particle hydro-code (SPH) are described and initial results reported. These codes can be, and have been, used to make specific predictions about particular objects in our solar system. But more significantly, they allow us to explore a broad range of collisional events. Certain parameters (size, time) can be studied only over a very restricted range within the laboratory; other parameters (initial spin, low gravity, exotic structure or composition) are difficult to study at all experimentally. The outcomes of numerical simulations lead to a more general and accurate understanding of impacts in their many forms.
Probing the chemical composition of the Z < 1 intergalactic medium with observations and simulations
NASA Astrophysics Data System (ADS)
Cooksey, Kathy L.
2009-09-01
significantly. The line density d[Special characters omitted.] /d X has not evolved as much, indicating that the average column density per doublet increases with decreasing redshift. In addition, I compare the observed properties of C IV absorbers with those predicted by cosmological hydrodynamic simulations with a variety of physical models (e.g., feedback, cosmology). I also use the results from the simulations that reproduce well the observations to understand better the physical conditions giving rise to the C IV absorbing gas. The observations and simulations indicate that the log N (C +3 ) > 13 C IV absorption systems predominately come from circum-galactic (or halo) gas.
Observation of Topological Links Associated with Hopf Insulators in a Solid-State Quantum Simulator
NASA Astrophysics Data System (ADS)
Yuan, X.-X.; He, L.; Wang, S.-T.; Deng, D.-L.; Wang, F.; Lian, W.-Q.; Wang, X.; Zhang, C.-H.; Zhang, H.-L.; Chang, X.-Y.; Duan, L.-M.
2017-06-01
Hopf insulators are intriguing three-dimensional topological insulators characterized by an integer topological invariant. They originate from the mathematical theory of Hopf fibration and epitomize the deep connection between knot theory and topological phases of matter, which distinguishes them from other classes of topological insulators. Here, we implement a model Hamiltonian for Hopf insulators in a solid-state quantum simulator and report the first experimental observation of their topological properties, including fascinating topological links associated with the Hopf fibration and the integer-valued topological invariant obtained from a direct tomographic measurement. Our observation of topological links and Hopf fibration in a quantum simulator opens the door to probe rich topological properties of Hopf insulators in experiments. The quantum simulation and probing methods are also applicable to the study of other intricate three-dimensional topological model Hamiltonians.
Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis, Phase 2 Results
NASA Technical Reports Server (NTRS)
Murri, Daniel G.
2011-01-01
The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL-Systems Analysis (SA) team that is conducting studies of the technologies and architectures that are required to enable human and higher mass robotic missions to Mars. The findings, observations, and recommendations from the NESC are provided in this report.
GEOS observation systems intercomparison investigation results
NASA Technical Reports Server (NTRS)
Berbert, J. H.
1974-01-01
The results of an investigation designed to determine the relative accuracy and precision of the different types of geodetic observation systems used by NASA is presented. A collocation technique was used to minimize the effects of uncertainties in the relative station locations and in the earth's gravity field model by installing accurate reference tracking systems close to the systems to be compared, and by precisely determining their relative survey. The Goddard laser and camera systems were shipped to selected sites, where they tracked the GEOS satellite simultaneously with other systems for an intercomparison observation.
NASA Astrophysics Data System (ADS)
Choi, Ena
2015-10-01
The lives of galaxies and their supermassive black holes (SMBH) are probably intimately linked. Deep multi-wavelength surveys with HST are now providing detailed imaging of a statistically robust sample of obscured and unobscured AGN hosts, along with control samples of inactive galaxies, giving us an unprecedented opportunity to study the relationship between AGN and their hosts. However, so far these observations have uncovered more puzzles than they have resolved. Although mergers are considered a promising triggering mechanism for AGN activity, numerous studies have shown that AGN hosts are no more likely to appear morphologically disturbed than inactive galaxies. Studies of whether AGN hosts exhibit enhanced or suppressed star formation have also yielded conflicting results. We propose to run a suite of state-of-the-art simulations to study the AGN-host galaxy connection. These simulations will be post-processed with a radiative transfer code, a sub-grid model for torus-scale obscuration, and short timescale AGN variability. Using mock images created from the simulations, we will study the predicted morphologies and stellar populations of AGN hosts and normal galaxies with similar stellar masses. We will use our simulations to address two major science questions: (1) how is SMBH growth fueled and fed, and what triggers rapid feeding, and (2) how does AGN feedback regulate BH growth and the growth of the host galaxy? In addition, we will release our simulation outputs and mock images and catalogs to the community through MAST.
NASA Technical Reports Server (NTRS)
West, Jeff S.; Richardson, Brian R.; Schmauch, Preston; Kenny, Robert J.
2011-01-01
Marshall Space Flight Center (MSFC) has been heavily involved in developing the J2-X engine. The Center has been testing a Work Horse Gas Generator (WHGG) to supply gas products to J2-X turbine components at realistic flight-like operating conditions. Three-dimensional time accurate CFD simulations and analytical fluid analysis have been performed to support WHGG tests at MSFC. The general purpose CFD program LOCI/Chem was utilized to simulate flow of products from the WHGG through a turbine manifold, a stationary row of turbine vanes, into a Can and orifice assembly used to control the back pressure at the turbine vane row and finally through an aspirator plate and flame bucket. Simulations showed that supersonic swirling flow downstream of the turbine imparted a much higher pressure on the Can wall than expected for a non-swirling flow. This result was verified by developing an analytical model that predicts wall pressure due to swirling flow. The CFD simulations predicted that the higher downstream pressure would cause the pressure drop across the nozzle row to be approximately half the value of the test objective. With CFD support, a redesign of the Can orifice and aspirator plate was performed. WHGG experimental results and observations compared well with pre-test and post-test CFD simulations. CFD simulations for both quasi-static and transient test conditions correctly predicted the pressure environment downstream of the turbine row and the behavior of the gas generator product plume as it exited the WHGG test article, impacted the flame bucket and interacted with the external environment.
NASA Astrophysics Data System (ADS)
Malherbe, J.-M.; Roudier, T.; Stein, R.; Frank, Z.
2018-01-01
We compare horizontal velocities, vertical magnetic fields, and the evolution of trees of fragmenting granules (TFG, also named families of granules) derived in the quiet Sun at disk center from observations at solar minimum and maximum of the Solar Optical Telescope (SOT on board Hinode) and results of a recent 3D numerical simulation of the magneto-convection. We used 24-hour sequences of a 2D field of view (FOV) with high spatial and temporal resolution recorded by the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager (NFI). TFG were evidenced by segmentation and labeling of continuum intensities. Horizontal velocities were obtained from local correlation tracking (LCT) of proper motions of granules. Stokes V provided a proxy of the line-of-sight magnetic field (BLOS). The MHD simulation (performed independently) produced granulation intensities, velocity, and magnetic field vectors. We discovered that TFG also form in the simulation and show that it is able to reproduce the main properties of solar TFG: lifetime and size, associated horizontal motions, corks, and diffusive index are close to observations. The largest (but not numerous) families are related in both cases to the strongest flows and could play a major role in supergranule and magnetic network formation. We found that observations do not reveal any significant variation in TFG between solar minimum and maximum.
NASA Astrophysics Data System (ADS)
O'Connor, J. Michael; Pretorius, P. Hendrik; Gifford, Howard C.; Licho, Robert; Joffe, Samuel; McGuiness, Matthew; Mehurg, Shannon; Zacharias, Michael; Brankov, Jovan G.
2012-02-01
Our previous Single Photon Emission Computed Tomography (SPECT) myocardial perfusion imaging (MPI) research explored the utility of numerical observers. We recently created two hundred and eighty simulated SPECT cardiac cases using Dynamic MCAT (DMCAT) and SIMIND Monte Carlo tools. All simulated cases were then processed with two reconstruction methods: iterative ordered subset expectation maximization (OSEM) and filtered back-projection (FBP). Observer study sets were assembled for both OSEM and FBP methods. Five physicians performed an observer study on one hundred and seventy-nine images from the simulated cases. The observer task was to indicate detection of any myocardial perfusion defect using the American Society of Nuclear Cardiology (ASNC) 17-segment cardiac model and the ASNC five-scale rating guidelines. Human observer Receiver Operating Characteristic (ROC) studies established the guidelines for the subsequent evaluation of numerical model observer (NO) performance. Several NOs were formulated and their performance was compared with the human observer performance. One type of NO was based on evaluation of a cardiac polar map that had been pre-processed using a gradient-magnitude watershed segmentation algorithm. The second type of NO was also based on analysis of a cardiac polar map but with use of a priori calculated average image derived from an ensemble of normal cases.
McGibbon, J.; Bretherton, C. S.
2017-03-17
During the Marine ARM GPCI Investigation of Clouds (MAGIC) in October 2011 to September 2012, a container ship making periodic cruises between Los Angeles, CA, and Honolulu, HI, was instrumented with surface meteorological, aerosol and radiation instruments, a cloud radar and ceilometer, and radiosondes. Here large-eddy simulation (LES) is performed in a ship-following frame of reference for 13 four day transects from the MAGIC field campaign. The goal is to assess if LES can skillfully simulate the broad range of observed cloud characteristics and boundary layer structure across the subtropical stratocumulus to cumulus transition region sampled during different seasons andmore » meteorological conditions. Results from Leg 15A, which sampled a particularly well-defined stratocumulus to cumulus transition, demonstrate the approach. The LES reproduces the observed timing of decoupling and transition from stratocumulus to cumulus and matches the observed evolution of boundary layer structure, cloud fraction, liquid water path, and precipitation statistics remarkably well. Considering the simulations of all 13 cruises, the LES skillfully simulates the mean diurnal variation of key measured quantities, including liquid water path (LWP), cloud fraction, measures of decoupling, and cloud radar-derived precipitation. The daily mean quantities are well represented, and daily mean LWP and cloud fraction show the expected correlation with estimated inversion strength. There is a –0.6 K low bias in LES near-surface air temperature that results in a high bias of 5.6 W m –2 in sensible heat flux (SHF). Altogether, these results build confidence in the ability of LES to represent the northeast Pacific stratocumulus to trade cumulus transition region.« less
NASA Astrophysics Data System (ADS)
Cicchetti, A.; Nenna, C.; Plaut, J. J.; Plettemeier, D.; Noschese, R.; Cartacci, M.; Orosei, R.
2017-11-01
The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005) is a synthetic aperture low frequency radar altimeter, onboard the ESA Mars Express orbiter, launched in June 2003. It is the first and so far the only spaceborne radar that has observed the Martian moon Phobos. Radar echoes were collected on different flyby trajectories. The primary aim of sounding Phobos is to prove the feasibility of deep sounding, into its subsurface. MARSIS is optimized for deep penetration investigations and is capable of transmitting at four different bands between 1.3 MHz and 5.5 MHz with a 1 MHz bandwidth. Unfortunately the instrument was originally designed to operate exclusively on Mars, assuming that Phobos would not be observed. Following this assumption, a protection mechanism was implemented in the hardware (HW) to maintain a minimum time separation between transmission and reception phases of the radar. This limitation does not have any impact on Mars observation but it prevented the observation of Phobos. In order to successfully operate the instrument at Phobos, a particular configuration of the MARSIS onboard software (SW) parameters, called ;Range Ambiguity,; was implemented to override the HW protection zone, ensuring at the same time a high level of safety of the instrument. This paper describes the principles of MARSIS onboard processing, and the procedure through which the parameters of the processing software were tuned to observe targets below the minimum distance allowed by hardware. Some preliminary results of data analysis will be shown, with the support of radar echo simulations. A qualitative comparison between the simulated results and the actual data, does not support the detection of subsurface reflectors.
Trans-Pacific yellow sand transport observed in April 1998: A numerical simulation
NASA Astrophysics Data System (ADS)
Uno, Itsushi; Amano, Hiroyasu; Emori, Seita; Kinoshita, Kisei; Matsui, Ichiro; Sugimoto, Nobuo
2001-08-01
A yellow sand transport episode from the Asian continent to Japan and North America which occurred in April 1998 is simulated. A new on-line dust tracer model coupled with a regional-scale meteorological model is developed and applied to this dust storm episode. The results for two large dust events that started during April 14-15 and 19-20, 1998, have been analyzed and discussed. The first dust storm was trapped in a cutoff vortex developed over the China plain. A modeled 3-D structure of dust associated with this cutoff vortex agreed with an observed time-height cross section of dust concentration. Results show that the strong subsidence at the backside of the vortex restricted the dust layer below 3 km level. Model analysis revealed that the second dust event that started during April 19-20 over inland China was the origin of a dust episode reported over North America. The trans-Pacific dust transport simulation successfully showed the dust onset near the West Coast of North America. Elevation of the dust layer during the long-range transport was below 3 km. The model is extended to include the transport of an Asian origin anthropogenic tracer over the North Pacific Rim. Both the natural-origin mineral dust and the Asian-origin anthropogenic tracer are simultaneously transported even if their emission regions are different.
An OSSE on Mesoscale Model Assimilation of Simulated HIRAD-Observed Hurricane Surface Winds
NASA Technical Reports Server (NTRS)
Albers, Cerese; Miller, Timothy; Uhlhorn, Eric; Krishnamurti, T. N.
2012-01-01
The hazards of landfalling hurricanes are well known, but progress on improving the intensity forecasts of these deadly storms at landfall has been slow. Many cite a lack of high-resolution data sets taken inside the core of a hurricane, and the lack of reliable measurements in extreme conditions near the surface of hurricanes, as possible reasons why even the most state-of-the-art forecasting models cannot seem to forecast intensity changes better. The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor for observing hurricanes, and is operated and researched by NASA Marshall Space Flight Center in partnership with the NOAA Atlantic Oceanographic and Meteorological Laboratory/Hurricane Research Division, the University of Central Florida, the University of Michigan, and the University of Alabama in Huntsville. This instrument?s purpose is to study the wind field of a hurricane, specifically observing surface wind speeds and rain rates, in what has traditionally been the most difficult areas for other instruments to study; the high wind and heavy rain regions. Dr. T. N. Krishnamurti has studied various data assimilation techniques for hurricane and monsoon rain rates, and this study builds off of results obtained from utilizing his style of physical initializations of rainfall observations, but obtaining reliable observations in heavy rain regions has always presented trouble to our research of high-resolution rainfall forecasting. Reliable data from these regions at such a high resolution and wide swath as HIRAD provides is potentially very valuable to mesoscale forecasting of hurricane intensity. This study shows how the data assimilation technique of Ensemble Kalman Filtering (EnKF) in the Weather Research and Forecasting (WRF) model can be used to incorporate wind, and later rain rate, data into a mesoscale model forecast of hurricane intensity. The study makes use of an Observing System Simulation Experiment (OSSE) with a simulated
NASA Technical Reports Server (NTRS)
Stanfield, Ryan E.; Dong, Xiquan; Xi, Baike; Del Genio, Anthony D.; Minnis, Patrick; Doelling, David; Loeb, Norman
2014-01-01
In Part I of this study, the NASA GISS Coupled Model Intercomparison Project (CMIP5) and post-CMIP5 (herein called C5 and P5, respectively) simulated cloud properties were assessed utilizing multiple satellite observations, with a particular focus on the southern midlatitudes (SMLs). This study applies the knowledge gained from Part I of this series to evaluate the modeled TOA radiation budgets and cloud radiative effects (CREs) globally using CERES EBAF (CE) satellite observations and the impact of regional cloud properties and water vapor on the TOA radiation budgets. Comparisons revealed that the P5- and C5-simulated global means of clear-sky and all-sky outgoing longwave radiation (OLR) match well with CE observations, while biases are observed regionally. Negative biases are found in both P5- and C5-simulated clear-sky OLR. P5-simulated all-sky albedo slightly increased over the SMLs due to the increase in low-level cloud fraction from the new planetary boundary layer (PBL) scheme. Shortwave, longwave, and net CRE are quantitatively analyzed as well. Regions of strong large-scale atmospheric upwelling/downwelling motion are also defined to compare regional differences across multiple cloud and radiative variables. In general, the P5 and C5 simulations agree with the observations better over the downwelling regime than over the upwelling regime. Comparing the results herein with the cloud property comparisons presented in Part I, the modeled TOA radiation budgets and CREs agree well with the CE observations. These results, combined with results in Part I, have quantitatively estimated how much improvement is found in the P5-simulated cloud and radiative properties, particularly over the SMLs and tropics, due to the implementation of the new PBL and convection schemes.
Scheduling Results for the THEMIS Observation Scheduling Tool
NASA Technical Reports Server (NTRS)
Mclaren, David; Rabideau, Gregg; Chien, Steve; Knight, Russell; Anwar, Sadaat; Mehall, Greg; Christensen, Philip
2011-01-01
We describe a scheduling system intended to assist in the development of instrument data acquisitions for the THEMIS instrument, onboard the Mars Odyssey spacecraft, and compare results from multiple scheduling algorithms. This tool creates observations of both (a) targeted geographical regions of interest and (b) general mapping observations, while respecting spacecraft constraints such as data volume, observation timing, visibility, lighting, season, and science priorities. This tool therefore must address both geometric and state/timing/resource constraints. We describe a tool that maps geometric polygon overlap constraints to set covering constraints using a grid-based approach. These set covering constraints are then incorporated into a greedy optimization scheduling algorithm incorporating operations constraints to generate feasible schedules. The resultant tool generates schedules of hundreds of observations per week out of potential thousands of observations. This tool is currently under evaluation by the THEMIS observation planning team at Arizona State University.
Mehran, Ali; AghaKouchak, Amir; Phillips, Thomas J.
2014-02-25
Numerous studies have emphasized that climate simulations are subject to various biases and uncertainties. The objective of this study is to cross-validate 34 Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations of precipitation against the Global Precipitation Climatology Project (GPCP) data, quantifying model pattern discrepancies and biases for both entire data distributions and their upper tails. The results of the Volumetric Hit Index (VHI) analysis of the total monthly precipitation amounts show that most CMIP5 simulations are in good agreement with GPCP patterns in many areas, but that their replication of observed precipitation over arid regions and certain sub-continentalmore » regions (e.g., northern Eurasia, eastern Russia, central Australia) is problematical. Overall, the VHI of the multi-model ensemble mean and median also are superior to that of the individual CMIP5 models. However, at high quantiles of reference data (e.g., the 75th and 90th percentiles), all climate models display low skill in simulating precipitation, except over North America, the Amazon, and central Africa. Analyses of total bias (B) in CMIP5 simulations reveal that most models overestimate precipitation over regions of complex topography (e.g. western North and South America and southern Africa and Asia), while underestimating it over arid regions. Also, while most climate model simulations show low biases over Europe, inter-model variations in bias over Australia and Amazonia are considerable. The Quantile Bias (QB) analyses indicate that CMIP5 simulations are even more biased at high quantiles of precipitation. Lastly, we found that a simple mean-field bias removal improves the overall B and VHI values, but does not make a significant improvement in these model performance metrics at high quantiles of precipitation.« less
The dynamics of human-water systems: comparing observations and simulations
NASA Astrophysics Data System (ADS)
Di Baldassarre, G.; Ciullo, A.; Castellarin, A.; Viglione, A.
2016-12-01
Real-word data of human-flood interactions are compared to the results of stylized socio-hydrological models. These models build on numerous examples from different parts of the world and consider two main prototypes of floodplain systems. Green systems, whereby societies cope with flood risk via non-structural measures, e.g. resettling out of floodplain areas ("living with floods" approach); and Technological systems, whereby societies cope with flood risk by also via structural measures, e.g. building levees ("fighting floods" approach). The floodplain systems of the Tiber River in Rome and the Ganges-Brahmaputra-Meghna Rivers in Bangladesh systems are used as case studies. The comparison of simulations and observations shows the potential of socio-hydrological models in capturing the dynamics of risk emerging from the interactions and feedbacks between social and hydrological processes, such as learning and forgetting effects. It is then discussed how the proposed approach can contribute to a better understanding of flood risk changes and therefore support the process of disaster risk reduction.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Beck, C.; Fabbian, D.; Rezaei, R.
2017-06-10
Before using three-dimensional (3D) magnetohydrodynamical (MHD) simulations of the solar photosphere in the determination of elemental abundances, one has to ensure that the correct amount of magnetic flux is present in the simulations. The presence of magnetic flux modifies the thermal structure of the solar photosphere, which affects abundance determinations and the solar spectral irradiance. The amount of magnetic flux in the solar photosphere also constrains any possible heating in the outer solar atmosphere through magnetic reconnection. We compare the polarization signals in disk-center observations of the solar photosphere in quiet-Sun regions with those in Stokes spectra computed on themore » basis of 3D MHD simulations having average magnetic flux densities of about 20, 56, 112, and 224 G. This approach allows us to find the simulation run that best matches the observations. The observations were taken with the Hinode SpectroPolarimeter (SP), the Tenerife Infrared Polarimeter (TIP), the Polarimetric Littrow Spectrograph (POLIS), and the GREGOR Fabry–Pèrot Interferometer (GFPI), respectively. We determine characteristic quantities of full Stokes profiles in a few photospheric spectral lines in the visible (630 nm) and near-infrared (1083 and 1565 nm). We find that the appearance of abnormal granulation in intensity maps of degraded simulations can be traced back to an initially regular granulation pattern with numerous bright points in the intergranular lanes before the spatial degradation. The linear polarization signals in the simulations are almost exclusively related to canopies of strong magnetic flux concentrations and not to transient events of magnetic flux emergence. We find that the average vertical magnetic flux density in the simulation should be less than 50 G to reproduce the observed polarization signals in the quiet-Sun internetwork. A value of about 35 G gives the best match across the SP, TIP, POLIS, and GFPI observations.« less
Global simulations and observations of O(1S), O2(1Σ) and OH mesospheric nightglow emissions
NASA Astrophysics Data System (ADS)
Yee, Jeng-Hwa; Crowley, G.; Roble, R. G.; Skinner, W. R.; Burrage, M. D.; Hays, P. B.
1997-09-01
Despite a large number of observations of mesospheric nightglow emissions in the past, the quantitative comparison between theoretical and experimental brightnesses is rather poor, owing primarily to the short duration of the observations, the strong variability of the tides, and the influence of short-timescale gravity waves. The high-resolution Doppler imager (HRDI) instrument onboard the upper atmosphere research satellite (UARS) provides nearly simultaneous, near-global observations of O(1S) green line, O2(0-1) atmospheric band, and OH Meinel band nightglow emissions. Three days of these observations near the September equinox of 1993 are presented to show the general characteristics of the three emissions, including the emission brightness, peak emission altitude, and their temporal and spatial variabilities. The global distribution of these emissions is simulated on the basis of atmospheric parameters from the recently developed National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM). The most striking features revealed by the global simulation are the structuring of the mesospheric nightglow by the diurnal tides and enhancements of the airglow at high latitudes. The model reproduces the inverse relationship observed by HRDI between the nightglow brightness and peak emission altitude. Analysis of our model results shows that the large-scale latitudinal/tidal nightglow brightness variations are a direct result of a complex interplay between mesospheric and lower thermospheric diffusive and advective processes, acting mainly on the atomic oxygen concentrations. The inclination of the UARS spacecraft precluded observations of high latitude nightglow emissions by HRDI. However, our predicted high-latitude brightness enhancements confirm previous limited groundbased observations in the polar region. This work provides an initial validation of the NCAR-TIMEGCM using airglow data.
NASA Astrophysics Data System (ADS)
Koepferl, Christine M.; Robitaille, Thomas P.
2017-11-01
When modeling astronomical objects throughout the universe, it is important to correctly treat the limitations of the data, for instance finite resolution and sensitivity. In order to simulate these effects, and to make radiative transfer models directly comparable to real observations, we have developed an open-source Python package called the FluxCompensator that enables the post-processing of the output of 3D Monte Carlo radiative transfer codes, such as Hyperion. With the FluxCompensator, realistic synthetic observations can be generated by modeling the effects of convolution with arbitrary point-spread functions, transmission curves, finite pixel resolution, noise, and reddening. Pipelines can be applied to compute synthetic observations that simulate observatories, such as the Spitzer Space Telescope or the Herschel Space Observatory. Additionally, this tool can read in existing observations (e.g., FITS format) and use the same settings for the synthetic observations. In this paper, we describe the package as well as present examples of such synthetic observations.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Koepferl, Christine M.; Robitaille, Thomas P., E-mail: koepferl@usm.lmu.de
When modeling astronomical objects throughout the universe, it is important to correctly treat the limitations of the data, for instance finite resolution and sensitivity. In order to simulate these effects, and to make radiative transfer models directly comparable to real observations, we have developed an open-source Python package called the FluxCompensator that enables the post-processing of the output of 3D Monte Carlo radiative transfer codes, such as Hyperion. With the FluxCompensator, realistic synthetic observations can be generated by modeling the effects of convolution with arbitrary point-spread functions, transmission curves, finite pixel resolution, noise, and reddening. Pipelines can be applied tomore » compute synthetic observations that simulate observatories, such as the Spitzer Space Telescope or the Herschel Space Observatory . Additionally, this tool can read in existing observations (e.g., FITS format) and use the same settings for the synthetic observations. In this paper, we describe the package as well as present examples of such synthetic observations.« less
Caution: Precision Error in Blade Alignment Results in Faulty Unsteady CFD Simulation
NASA Astrophysics Data System (ADS)
Lewis, Bryan; Cimbala, John; Wouden, Alex
2012-11-01
Turbomachinery components experience unsteady loads at several frequencies. The rotor frequency corresponds to the time for one rotor blade to rotate between two stator vanes, and is normally dominant for rotor torque oscillations. The guide vane frequency corresponds to the time for two rotor blades to pass by one guide vane. The machine frequency corresponds to the machine RPM. Oscillations at the machine frequency are always present due to minor blade misalignments and imperfections resulting from manufacturing defects. However, machine frequency oscillations should not be present in CFD simulations if the mesh is free of both blade misalignment and surface imperfections. The flow through a Francis hydroturbine was modeled with unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD simulations and a dynamic rotating grid. Spectral analysis of the unsteady torque on the rotor blades revealed a large component at the machine frequency. Close examination showed that one blade was displaced by 0 .0001° due to round-off errors during mesh generation. A second mesh without blade misalignment was then created. Subsequently, large machine frequency oscillations were not observed for this mesh. These results highlight the effect of minor geometry imperfections on CFD solutions. This research was supported by a grant from the DoE and a National Defense Science and Engineering Graduate Fellowship.
Remote Sensing Observations and Numerical Simulation for Martian Layered Ejecta Craters
NASA Astrophysics Data System (ADS)
Li, L.; Yue, Z.; Zhang, C.; Li, D.
2018-04-01
To understand past Martian climates, it is important to know the distribution and nature of water ice on Mars. Impact craters are widely used ubiquitous indicators for the presence of subsurface water or ice on Mars. Remote sensing observations and numerical simulation are powerful tools for investigating morphological and topographic features on planetary surfaces, and we can use the morphology of layered ejecta craters and hydrocode modeling to constrain possible layering and impact environments. The approach of this work consists of three stages. Firstly, the morphological characteristics of the Martian layered ejecta craters are performed based on Martian images and DEM data. Secondly, numerical modeling layered ejecta are performed through the hydrocode iSALE (impact-SALE). We present hydrocode modeling of impacts onto targets with a single icy layer within an otherwise uniform basalt crust to quantify the effects of subsurface H2O on observable layered ejecta morphologies. The model setup is based on a layered target made up of a regolithic layer (described by the basalt ANEOS), on top an ice layer (described by ANEOS equation of H2O ice), in turn on top of an underlying basaltic crust. The bolide is a 0.8 km diameter basaltic asteroid hitting the Martian surface vertically at a velocity of 12.8 km/s. Finally, the numerical results are compared with the MOLA DEM profile in order to analyze the formation mechanism of Martian layered ejecta craters. Our simulations suggest that the presence of an icy layer significantly modifies the cratering mechanics, and many of the unusual features of SLE craters may be explained by the presence of icy layers. Impact cratering on icy satellites is significantly affected by the presence of subsurface H2O.
Observed and Simulated Urban Heat Island and Urban Cool Island in Las Vegas
NASA Astrophysics Data System (ADS)
Sauceda, Daniel O.
This research investigates the urban climate of Las Vegas and establishes long-term trends relative to the regional climate in an attempt to identify climate disturbances strictly related to urban growth. An experimental surface station network (DRI-UHI) of low-cost surface temperature (T2m) and relative humidity (RH) sensors were designed to cover under-sampled low-intensity residential urban areas, as well as complement the in-city and surrounding rural areas. In addition to the analysis of the surface station data, high-resolution gridded data products (GDPs) from Daymet (1km) and PRISM (800 m) and results from numerical simulations were used to further characterize the Las Vegas climate trends. The Weather Research and Forecasting (WRF) model was coupled with three different models: the Noah Land Surface Model (LSM) and a single- and multi-layer urban canopy model (UCM) to assess the urban related climate disturbances; as well as the model sensitivity and ability to characterize diurnal variability and rural/urban thermal contrasts. The simulations consisted of 1 km grid size for five, one month-long hindcast simulations during November of 2012: (i) using the Noah LSM without UCM treatment, (ii) same as (i) with a single-layer UCM (UCM1), (iii) same as (i) with a multi-layer UCM (UCM2), (iv) removing the City of Las Vegas (NC) and replacing it with predominant land cover (shrub), and (v) same as (ii) with increasing the albedo of rooftops from 0.20 to 0.65 as a potential adaptation scenario known as "white roofing". T2m long-term trends showed a regional warming of minimum temperatures (Tmin) and negligible trends in maximum temperatures (Tmax ). By isolating the regional temperature trends, an observed urban heat island (UHI) of ~1.63°C was identified as well as a daytime urban cool island (UCI) of ~0.15°C. GDPs agree with temperature trends but tend to underpredict UHI intensity by ~1.05°C. The WRF-UCM showed strong correlations with observed T2m (0
NASA Technical Reports Server (NTRS)
Stanfield, Ryan E.; Dong, Xiquan; Xi, Baike; Kennedy, Aaron; Del Genio, Anthony D.; Minnia, Patrick; Jiang, Jonathan H.
2014-01-01
Although many improvements have been made in phase 5 of the Coupled Model Intercomparison Project (CMIP5), clouds remain a significant source of uncertainty in general circulation models (GCMs) because their structural and optical properties are strongly dependent upon interactions between aerosol/cloud microphysics and dynamics that are unresolved in such models. Recent changes to the planetary boundary layer (PBL) turbulence and moist convection parameterizations in the NASA GISS Model E2 atmospheric GCM(post-CMIP5, hereafter P5) have improved cloud simulations significantly compared to its CMIP5 (hereafter C5) predecessor. A study has been performed to evaluate these changes between the P5 and C5 versions of the GCM, both of which used prescribed sea surface temperatures. P5 and C5 simulated cloud fraction (CF), liquid water path (LWP), ice water path (IWP), cloud water path (CWP), precipitable water vapor (PWV), and relative humidity (RH) have been compared to multiple satellite observations including the Clouds and the Earth's Radiant Energy System-Moderate Resolution Imaging Spectroradiometer (CERES-MODIS, hereafter CM), CloudSat- Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO; hereafter CC), Atmospheric Infrared Sounder (AIRS), and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). Although some improvements are observed in the P5 simulation on a global scale, large improvements have been found over the southern midlatitudes (SMLs), where correlations increased and both bias and root-mean-square error (RMSE) significantly decreased, in relation to the previous C5 simulation, when compared to observations. Changes to the PBL scheme have resulted in improved total column CFs, particularly over the SMLs where marine boundary layer (MBL) CFs have increased by nearly 20% relative to the previous C5 simulation. Globally, the P5 simulated CWPs are 25 gm22 lower than the previous C5 results. The P5 version of the
Exploring the observational constraints on the simulation of brown carbon
NASA Astrophysics Data System (ADS)
Wang, Xuan; Heald, Colette L.; Liu, Jiumeng; Weber, Rodney J.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Schwarz, Joshua P.; Perring, Anne E.
2018-01-01
Organic aerosols (OA) that strongly absorb solar radiation in the near-UV are referred to as brown carbon (BrC). The sources, evolution, and optical properties of BrC remain highly uncertain and contribute significantly to uncertainty in the estimate of the global direct radiative effect (DRE) of aerosols. Previous modeling studies of BrC optical properties and DRE have been unable to fully evaluate model performance due to the lack of direct measurements of BrC absorption. In this study, we develop a global model simulation (GEOS-Chem) of BrC and test it against BrC absorption measurements from two aircraft campaigns in the continental US (SEAC4RS and DC3). To the best of our knowledge, this is the first study to compare simulated BrC absorption with direct aircraft measurements. We show that BrC absorption properties estimated based on previous laboratory measurements agree with the aircraft measurements of freshly emitted BrC absorption but overestimate aged BrC absorption. In addition, applying a photochemical scheme to simulate bleaching/degradation of BrC improves model skill. The airborne observations are therefore consistent with a mass absorption coefficient (MAC) of freshly emitted biomass burning OA of 1.33 m2 g-1 at 365 nm coupled with a 1-day whitening e-folding time. Using the GEOS-Chem chemical transport model integrated with the RRTMG radiative transfer model, we estimate that the top-of-the-atmosphere all-sky direct radiative effect (DRE) of OA is -0.344 Wm-2, 10 % higher than that without consideration of BrC absorption. Therefore, our best estimate of the absorption DRE of BrC is +0.048 Wm-2. We suggest that the DRE of BrC has been overestimated previously due to the lack of observational constraints from direct measurements and omission of the effects of photochemical whitening.
2010-04-14
for inter- basin exchange, including the net throughflow transport. The simulated total ITF transport (-13.4 Sv) is similar to the observational...May 2004 and 2005, November 2004, 2005 and 2006) appear to be associated with coastally-trapped Kelvin waves propagating eastward along Sumatra coast...in global HYCOM, this submerged multi-passage plateau causes the flow to separate into three branches, an eastern and central branch that feeds the
NASA Astrophysics Data System (ADS)
O'Donncha, Fearghal; Hartnett, Michael; Nash, Stephen; Ren, Lei; Ragnoli, Emanuele
2015-02-01
In this study, High Frequency Radar (HFR), observations in conjunction with numerical model simulations investigate surface flow dynamics in a tidally-active, wind-driven bay; Galway Bay situated on the West coast of Ireland. Comparisons against ADCP sensor data permit an independent assessment of HFR and model performance, respectively. Results show root-mean-square (rms) differences in the range 10 - 12cm/s while model rms equalled 12 - 14cm/s. Subsequent analysis focus on a detailed comparison of HFR and model output. Harmonic analysis decompose both sets of surface currents based on distinct flow process, enabling a correlation analysis between the resultant output and dominant forcing parameters. Comparisons of barotropic model simulations and HFR tidal signal demonstrate consistently high agreement, particularly of the dominant M2 tidal signal. Analysis of residual flows demonstrate considerably poorer agreement, with the model failing to replicate complex flows. A number of hypotheses explaining this discrepancy are discussed, namely: discrepancies between regional-scale, coastal-ocean models and globally-influenced bay-scale dynamics; model uncertainties arising from highly-variable wind-driven flows across alarge body of water forced by point measurements of wind vectors; and the high dependence of model simulations on empirical wind-stress coefficients. The research demonstrates that an advanced, widely-used hydro-environmental model does not accurately reproduce aspects of surface flow processes, particularly with regards wind forcing. Considering the significance of surface boundary conditions in both coastal and open ocean dynamics, the viability of using a systematic analysis of results to improve model predictions is discussed.
A simulation study of particle energization observed by THEMIS spacecraft during a substorm
NASA Astrophysics Data System (ADS)
Ashour-Abdalla, Maha; Bosqued, Jean-Michel; El-Alaoui, Mostafa; Peroomian, Vahe; Zhou, Meng; Richard, Robert; Walker, Raymond; Runov, Andrei; Angelopoulos, Vassilis
2009-09-01
Energetic ions with hundreds of keV energy are frequently observed in the near-Earth tail during magnetospheric substorms. We examined the sources and acceleration of ions during a magnetospheric substorm on 1 March 2008 by using Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Cluster observations and numerical simulations. Four of the THEMIS spacecraft were aligned at yGSM = 6 RE during a very large substorm (AE = 1200) while the Cluster spacecraft were located about 5 RE above the auroral ionosphere. For 2 h before the substorm, Cluster observed ionospheric oxygen flowing out into the magnetosphere. After substorm onset the THEMIS P3 and P4 spacecraft located in the near-Earth tail (xGSM = -9 RE and -8 RE, respectively) observed large fluxes of energetic ions up to 500 keV. We used calculations of millions of ions of solar wind and ionospheric origin in the time-dependent electric and magnetic fields from a global magnetohydrodynamic simulation of this event to study the source of these ions and their acceleration. The simulation did a good job of reproducing the particle observations. Both solar wind protons and ionospheric oxygen were accelerated by nonadiabatic motion across large (>˜5 mV/m) total electric fields (both potential and induced). The acceleration occurred in the "wall" region of the near-Earth tail where nonadiabatic motion dominates over convection and the particles move rapidly across the tail. The acceleration occurred mostly in regions with large electric fields and nonadiabatic motion. There was relatively little acceleration in regions with large electric fields and adiabatic motion or small electric fields and nonadiabatic motion. Prior to substorm onset, ionospheric ions were a significant contributor to the cross-tail current, but after onset, solar wind ions become more dominant.
NASA Astrophysics Data System (ADS)
Rutledge, G. K.; Karl, T. R.; Easterling, D. R.; Buja, L.; Stouffer, R.; Alpert, J.
2001-05-01
A major transition in our ability to evaluate transient Global Climate Model (GCM) simulations is occurring. Real-time and retrospective numerical weather prediction analysis, model runs, climate simulations and assessments are proliferating from a handful of national centers to dozens of groups across the world. It is clear that it is no longer sufficient for any one national center to develop its data services alone. The comparison of transient GCM results with the observational climate record is difficult for several reasons. One limitation is that the global distributions of a number of basic climate quantities, such as precipitation, are not well known. Similarly, observational limitations exist with model re-analysis data. Both the NCEP/NCAR, and the ECMWF, re-analysis eliminate the problems of changing analysis systems but observational data also contain time-dependant biases. These changes in input data are blended with the natural variability making estimates of true variability uncertain. The need for data homogeneity is critical to study questions related to the ability to evaluate simulation of past climate. One approach to correct for time-dependant biases and data sparse regions is the development and use of high quality 'reference' data sets. The primary U.S. National responsibility for the archive and service of weather and climate data rests with the National Climatic Data Center (NCDC). However, as supercomputers increase the temporal and spatial resolution of both Numerical Weather Prediction (NWP) and GCM models, the volume and varied formats of data presented for archive at NCDC, using current communications technologies and data management techniques is limiting the scientific access of these data. To address this ever expanding need for climate and NWP information, NCDC along with the National Center's for Environmental Prediction (NCEP) have initiated the NOAA Operational Model Archive and Distribution System (NOMADS). NOMADS is a
NASA Astrophysics Data System (ADS)
ZuHone, J. A.; Kowalik, K.; Öhman, E.; Lau, E.; Nagai, D.
2018-01-01
We present the “Galaxy Cluster Merger Catalog.” This catalog provides an extensive suite of mock observations and related data for N-body and hydrodynamical simulations of galaxy cluster mergers and clusters from cosmological simulations. These mock observations consist of projections of a number of important observable quantities in several different wavebands, as well as along different lines of sight through each simulation domain. The web interface to the catalog consists of easily browsable images over epoch and projection direction, as well as download links for the raw data and a JS9 interface for interactive data exploration. The data are presented within a consistent format so that comparison between simulations is straightforward. All of the data products are provided in the standard Flexible Image Transport System file format. The data are being stored on the yt Hub (http://hub.yt), which allows for remote access and analysis using a Jupyter notebook server. Future versions of the catalog will include simulations from a number of research groups and a variety of research topics related to the study of interactions of galaxy clusters with each other and with their member galaxies. The catalog is located at http://gcmc.hub.yt.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Varble, Adam; Zipser, Edward J.; Fridlind, Ann M.
2014-12-18
Ten 3D cloud-resolving model (CRM) simulations and four 3D limited area model (LAM) simulations of an intense mesoscale convective system observed on 23-24 January 2006 during the Tropical Warm Pool – International Cloud Experiment (TWP-ICE) are compared with each other and with observed radar reflectivity fields and dual-Doppler retrievals of vertical wind speeds in an attempt to explain published results showing a high bias in simulated convective radar reflectivity aloft. This high bias results from ice water content being large, which is a product of large, strong convective updrafts, although hydrometeor size distribution assumptions modulate the size of this bias.more » Making snow mass more realistically proportional to D2 rather than D3 eliminates unrealistically large snow reflectivities over 40 dBZ in some simulations. Graupel, unlike snow, produces high biased reflectivity in all simulations, which is partly a result of parameterized microphysics, but also partly a result of overly intense simulated updrafts. Peak vertical velocities in deep convective updrafts are greater than dual-Doppler retrieved values, especially in the upper troposphere. Freezing of liquid condensate, often rain, lofted above the freezing level in simulated updraft cores greatly contributes to these excessive upper tropospheric vertical velocities. The strongest simulated updraft cores are nearly undiluted, with some of the strongest showing supercell characteristics during the multicellular (pre-squall) stage of the event. Decreasing horizontal grid spacing from 900 to 100 meters slightly weakens deep updraft vertical velocity and moderately decreases the amount of condensate aloft, but not enough to match observational retrievals. Therefore, overly intense simulated updrafts may additionally be a product of unrealistic interactions between convective dynamics, parameterized microphysics, and the large-scale model forcing that promote different convective strengths than
NASA Astrophysics Data System (ADS)
Wu, C.; Liu, X.; Zhang, K.; Diao, M.; Gettelman, A.
2016-12-01
Cirrus clouds in the upper troposphere play a key role in the Earth radiation budget, and their radiative forcing depends strongly on number concentration and size distribution of ice particles. In this study we evaluate the cloud microphysical properties simulated by the Community Atmosphere Model version 5.4 (CAM5) against the Small Particles in Cirrus (SPartICus) observations over the ARM South Great Plain (SGP) site between January and June 2010. Model simulation is performed using specific dynamics to preserve prognostic meteorology (U, V, and T) close to GEOS-5 analysis. Model results collocated with SPartICus flight tracks spatially and temporally are directly compared with the observations. We compare CAM5 simulated ice crystal number concentration (Ni), ice particle size distribution, ice water content (IWC), and Ni co-variances with temperature and vertical velocity with the statistics from SPartICus observations. All analyses are restricted to T ≤ -40°C and in a 6°×6° area centered at SGP. Model sensitivity tests are performed with different ice nucleation mechanisms and with the effects of pre-existing ice crystals to reflect the uncertainties in cirrus parameterizations. In addition, different threshold size for autoconversion of cloud ice to snow (Dcs) is also tested. We find that (1) a distinctly high Ni (100-1000 L-1) often occurred in the observations but is significantly underestimated in the model, which may be due to the smaller relative humidity with respect to ice (RHi) in the simulation that could suppress the homogeneous nucleation, (2) a positive correlation exists between Ni and vertical velocity variance (σw) at horizontal scales up to 50 km in the observation, and the model can reproduce this relationship but tends to underestimate Ni when σw is relatively small, (3) simulated Ni differs greatly among the sensitive experiments, and simulated IWC is also sensitive to the cirrus parameterizations but to a lesser extent. Moreover
Results of GEANT simulations and comparison with first experiments at DANCE.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Reifarth, R.; Bredeweg, T. A.; Browne, J. C.
2003-07-29
This report describes intensive Monte Carlo simulations carried out to be compared with the results of the first run cycle with DANCE (Detector for Advanced Neutron Capture Experiments). The experimental results were gained during the commissioning phase 2002/2003 with only a part of the array. Based on the results of these simulations the most important items to be improved before the next experiments will be addressed.
Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model
NASA Astrophysics Data System (ADS)
Shellito, Peter J.; Small, Eric E.; Livneh, Ben
2018-03-01
Drydown periods that follow precipitation events provide an opportunity to assess controls on soil evaporation on a continental scale. We use SMAP (Soil Moisture Active Passive) observations and Noah simulations from drydown periods to quantify the role of soil moisture, potential evaporation, vegetation cover, and soil texture on soil drying rates. Rates are determined using finite differences over intervals of 1 to 3 days. In the Noah model, the drying rates are a good approximation of direct soil evaporation rates, and our work suggests that SMAP-observed drying is also predominantly affected by direct soil evaporation. Data cover the domain of the North American Land Data Assimilation System Phase 2 and span the first 1.8 years of SMAP's operation. Drying of surface soil moisture observed by SMAP is faster than that simulated by Noah. SMAP drying is fastest when surface soil moisture levels are high, potential evaporation is high, and when vegetation cover is low. Soil texture plays a minor role in SMAP drying rates. Noah simulations show similar responses to soil moisture and potential evaporation, but vegetation has a minimal effect and soil texture has a much larger effect compared to SMAP. When drying rates are normalized by potential evaporation, SMAP observations and Noah simulations both show that increases in vegetation cover lead to decreases in evaporative efficiency from the surface soil. However, the magnitude of this effect simulated by Noah is much weaker than that determined from SMAP observations.
First results from simulations of supersymmetric lattices
NASA Astrophysics Data System (ADS)
Catterall, Simon
2009-01-01
We conduct the first numerical simulations of lattice theories with exact supersymmetry arising from the orbifold constructions of \\cite{Cohen:2003xe,Cohen:2003qw,Kaplan:2005ta}. We consider the Script Q = 4 theory in D = 0,2 dimensions and the Script Q = 16 theory in D = 0,2,4 dimensions. We show that the U(N) theories do not possess vacua which are stable non-perturbatively, but that this problem can be circumvented after truncation to SU(N). We measure the distribution of scalar field eigenvalues, the spectrum of the fermion operator and the phase of the Pfaffian arising after integration over the fermions. We monitor supersymmetry breaking effects by measuring a simple Ward identity. Our results indicate that simulations of Script N = 4 super Yang-Mills may be achievable in the near future.
SWAT use of gridded observations for simulating runoff - a Vietnam river basin study
NASA Astrophysics Data System (ADS)
Vu, M. T.; Raghavan, S. V.; Liong, S. Y.
2012-08-01
Many research studies that focus on basin hydrology have applied the SWAT model using station data to simulate runoff. But over regions lacking robust station data, there is a problem of applying the model to study the hydrological responses. For some countries and remote areas, the rainfall data availability might be a constraint due to many different reasons such as lacking of technology, war time and financial limitation that lead to difficulty in constructing the runoff data. To overcome such a limitation, this research study uses some of the available globally gridded high resolution precipitation datasets to simulate runoff. Five popular gridded observation precipitation datasets: (1) Asian Precipitation Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources (APHRODITE), (2) Tropical Rainfall Measuring Mission (TRMM), (3) Precipitation Estimation from Remote Sensing Information using Artificial Neural Network (PERSIANN), (4) Global Precipitation Climatology Project (GPCP), (5) a modified version of Global Historical Climatology Network (GHCN2) and one reanalysis dataset, National Centers for Environment Prediction/National Center for Atmospheric Research (NCEP/NCAR) are used to simulate runoff over the Dak Bla river (a small tributary of the Mekong River) in Vietnam. Wherever possible, available station data are also used for comparison. Bilinear interpolation of these gridded datasets is used to input the precipitation data at the closest grid points to the station locations. Sensitivity Analysis and Auto-calibration are performed for the SWAT model. The Nash-Sutcliffe Efficiency (NSE) and Coefficient of Determination (R2) indices are used to benchmark the model performance. Results indicate that the APHRODITE dataset performed very well on a daily scale simulation of discharge having a good NSE of 0.54 and R2 of 0.55, when compared to the discharge simulation using station data (0.68 and 0.71). The GPCP proved to be the
Multiple Optical Filter Design Simulation Results
NASA Astrophysics Data System (ADS)
Mendelsohn, J.; Englund, D. C.
1986-10-01
In this paper we continue our investigation of the application of matched filters to robotic vision problems. Specifically, we are concerned with the tray-picking problem. Our principal interest in this paper is the examination of summation affects which arise from attempting to reduce the matched filter memory size by averaging of matched filters. While the implementation of matched filtering theory to applications in pattern recognition or machine vision is ideally through the use of optics and optical correlators, in this paper the results were obtained through a digital simulation of the optical process.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fayock, B.; Zank, G. P.; Heerikhuisen, J., E-mail: brian.fayock@gmail.com, E-mail: garyp.zank@gmail.com, E-mail: jacob.heerikhuisen@uah.edu
Observations made by ultraviolet (UV) detectors on board Pioneer 10, Voyager 1, and Voyager 2 can be used to analyze the distribution of neutral hydrogen throughout the heliosphere, including the interaction regions of the solar wind and local interstellar medium. Previous studies of the long-term trend of decreasing intensity with increasing heliocentric distance established the need for more sophisticated heliospheric models. Here we use state-of-the-art three-dimensional (3D) magnetohydrodynamic (MHD) neutral models to simulate Lyman-alpha backscatter as would be seen by the three spacecrafts, exploiting a new 3D Monte Carlo radiative transfer code under solar minimum conditions. Both observations and simulationsmore » of the UV backscatter intensity are normalized for each spacecraft flight path at {approx}15 AU, and we focus on the slope of decreasing intensity over an increasing heliocentric distance. Comparisons of simulations with Voyager 1 Lyman-alpha data results in a very close match, while the Pioneer 10 comparison is similar due to normalization, but not considered to be in agreement. The deviations may be influenced by a low resolution of photoionization in the 3D MHD-neutral model, a lack of solar cycle activity in our simulations, and possibly issues with instrumental sensitivity. Comparing the slope of Voyager 2 and the simulated intensities yields an almost identical match. Our results predict a large increase in the Lyman-alpha intensity as the hydrogen wall is approached, which would signal an imminent crossing of the heliopause.« less
NASA Technical Reports Server (NTRS)
Su, Hui; Waliser, Duane E.; Jiang, Jonathan H.; Li, Jui-lin; Read, William G.; Waters, Joe W.; Tompkins, Adrian M.
2006-01-01
The relationships of upper tropospheric water vapor (UTWV), cloud ice and sea surface temperature (SST) are examined in the annual cycles of ECMWF analyses and simulations from 15 atmosphere-ocean coupled models which were contributed to the IPCC AR4. The results are compared with the observed relationships based on UTWV and cloud ice measurements from MLS on Aura. It is shown that the ECMWF analyses produce positive correlations between UTWV, cloud ice and SST, similar to the MLS data. The rate of the increase of cloud ice and UTWV with SST is about 30% larger than that for MLS. For the IPCC simulations, the relationships between UTWV, cloud ice and SST are qualitatively captured. However, the magnitudes of the simulated cloud ice show a considerable disagreement between models, by nearly a factor of 10. The amplitudes of the approximate linear relations between UTWV, cloud ice and SST vary by a factor up to 4.
Simulations Build Efficacy: Empirical Results from a Four-Week Congressional Simulation
ERIC Educational Resources Information Center
Mariani, Mack; Glenn, Brian J.
2014-01-01
This article describes a four-week congressional committee simulation implemented in upper level courses on Congress and the Legislative process at two liberal arts colleges. We find that the students participating in the simulation possessed high levels of political knowledge and confidence in their political skills prior to the simulation. An…
NASA Astrophysics Data System (ADS)
Philip, S.; Johnson, M. S.; Potter, C. S.; Genovese, V. B.
2016-12-01
Atmospheric mixing ratios of carbon dioxide (CO2) are largely controlled by anthropogenic emission sources and biospheric sources/sinks. Global biospheric fluxes of CO2 are controlled by complex processes facilitating the exchange of carbon between terrestrial ecosystems and the atmosphere. These processes which play a key role in these terrestrial ecosystem-atmosphere carbon exchanges are currently not fully understood, resulting in large uncertainties in the quantification of biospheric CO2 fluxes. Current models with these inherent deficiencies have difficulties simulating the global carbon cycle with high accuracy. We are developing a new modeling platform, GEOS-Chem-CASA by integrating the year-specific NASA-CASA (National Aeronautics and Space Administration - Carnegie Ames Stanford Approach) biosphere model with the GEOS-Chem (Goddard Earth Observation System-Chemistry) chemical transport model to improve the simulation of atmosphere-terrestrial ecosystem carbon exchange. We use NASA-CASA to explicitly represent the exchange of CO2 between terrestrial ecosystem and atmosphere by replacing the baseline GEOS-Chem land net CO2 flux and forest biomass burning CO2 emissions. We will present the estimation and evaluation of these "bottom-up" land CO2 fluxes, simulated atmospheric mixing ratios, and forest disturbance changes over the last decade. In addition, we will present our initial comparison of atmospheric column-mean dry air mole fraction of CO2 predicted by the model and those retrieved from NASA's OCO-2 (Orbiting Carbon Observatory-2) satellite instrument and model-predicted surface CO2 mixing ratios with global in situ observations. This evaluation is the first step necessary for our future work planned to constrain the estimates of biospheric carbon fluxes through "top-down" inverse modeling, which will improve our understanding of the processes controlling atmosphere-terrestrial ecosystem greenhouse gas exchanges, especially over regions which lack in
Cloud-edge mixing: Direct numerical simulation and observations in Indian Monsoon clouds
NASA Astrophysics Data System (ADS)
Kumar, Bipin; Bera, Sudarsan; Prabha, Thara V.; Grabowski, Wojceich W.
2017-03-01
A direct numerical simulation (DNS) with the decaying turbulence setup has been carried out to study cloud-edge mixing and its impact on the droplet size distribution (DSD) applying thermodynamic conditions observed in monsoon convective clouds over Indian subcontinent during the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX). Evaporation at the cloud-edges initiates mixing at small scale and gradually introduces larger-scale fluctuations of the temperature, moisture, and vertical velocity due to droplet evaporation. Our focus is on early evolution of simulated fields that show intriguing similarities to the CAIPEEX cloud observations. A strong dilution at the cloud edge, accompanied by significant spatial variations of the droplet concentration, mean radius, and spectral width, are found in both the DNS and in observations. In DNS, fluctuations of the mean radius and spectral width come from the impact of small-scale turbulence on the motion and evaporation of inertial droplets. These fluctuations decrease with the increase of the volume over which DNS data are averaged, as one might expect. In cloud observations, these fluctuations also come from other processes, such as entrainment/mixing below the observation level, secondary CCN activation, or variations of CCN activation at the cloud base. Despite large differences in the spatial and temporal scales, the mixing diagram often used in entrainment/mixing studies with aircraft data is remarkably similar for both DNS and cloud observations. We argue that the similarity questions applicability of heuristic ideas based on mixing between two air parcels (that the mixing diagram is designed to properly represent) to the evolution of microphysical properties during turbulent mixing between a cloud and its environment.
NASA Astrophysics Data System (ADS)
Beranová, Romana; Kyselý, Jan; Hanel, Martin
2018-04-01
The study compares characteristics of observed sub-daily precipitation extremes in the Czech Republic with those simulated by Hadley Centre Regional Model version 3 (HadRM3) and Rossby Centre Regional Atmospheric Model version 4 (RCA4) regional climate models (RCMs) driven by reanalyses and examines diurnal cycles of hourly precipitation and their dependence on intensity and surface temperature. The observed warm-season (May-September) maxima of short-duration (1, 2 and 3 h) amounts show one diurnal peak in the afternoon, which is simulated reasonably well by RCA4, although the peak occurs too early in the model. HadRM3 provides an unrealistic diurnal cycle with a nighttime peak and an afternoon minimum coinciding with the observed maximum for all three ensemble members, which suggests that convection is not captured realistically. Distorted relationships of the diurnal cycles of hourly precipitation to daily maximum temperature in HadRM3 further evidence that underlying physical mechanisms are misrepresented in this RCM. Goodness-of-fit tests indicate that generalised extreme value distribution is an applicable model for both observed and RCM-simulated precipitation maxima. However, the RCMs are not able to capture the range of the shape parameter estimates of distributions of short-duration precipitation maxima realistically, leading to either too many (nearly all for HadRM3) or too few (RCA4) grid boxes in which the shape parameter corresponds to a heavy tail. This means that the distributions of maxima of sub-daily amounts are distorted in the RCM-simulated data and do not match reality well. Therefore, projected changes of sub-daily precipitation extremes in climate change scenarios based on RCMs not resolving convection need to be interpreted with caution.
CLaMS-Ice: Large-scale cirrus cloud simulations in comparison with observations
NASA Astrophysics Data System (ADS)
Costa, Anja; Rolf, Christian; Grooß, Jens-Uwe; Spichtinger, Peter; Afchine, Armin; Spelten, Nicole; Dreiling, Volker; Zöger, Martin; Krämer, Martina
2016-04-01
Cirrus clouds are an element of uncertainty in the climate system and have received increasing attention since the last IPCC reports. The interactions of different freezing mechanisms, sedimentation rates, updraft velocity fluctuations and other factors that determine the formation and evolution of those clouds is still not fully understood. Thus, a reliable representation of cirrus clouds in models representing real atmospheric conditions is still a challenging task. At last year's EGU, Rolf et al. (2015) introduced the new large-scale microphysical cirrus cloud model CLaMS-Ice: based on trajectories calculated with CLaMS (McKenna et al., 2002 and Konopka et al. 2007), it simulates the development of cirrus clouds relying on the cirrus bulk model by Spichtinger and Gierens (2009). The qualitative agreement between CLaMS-Ice simulations and observations could be demonstrated at that time. Now we present a detailed quantitative comparison between standard ECMWF products, CLaMS-Ice simulations, and in-situ measurements obtained during the ML-Cirrus campaign 2014. We discuss the agreement of the parameters temperature (observational data: BAHAMAS), relative humidity (SHARC), cloud occurrence, cloud particle concentration, ice water content and cloud particle radii (all NIXE-CAPS). Due to the precise trajectories based on ECMWF wind and temperature fields, CLaMS-Ice represents the cirrus cloud vertical and horizontal coverage more accurately than the ECMWF ice water content (IWC) fields. We demonstrate how CLaMS-Ice can be used to evaluate different input settings (e.g. amount of ice nuclei, freezing thresholds, sedimentation settings) that lead to cirrus clouds with the microphysical properties observed during ML-Cirrus (2014).
NASA Astrophysics Data System (ADS)
Jiang, J. H.; Eckermann, S. D.; Wu, D. L.; Ma, J.; Wang, D. Y.
2003-04-01
Topography-related wintertime stratospheric gravity waves in both Northern and Southern Hemisphere are simulated using the Naval Research Laboratory Mountain Wave Forecast Model (MWFM). The results agree well with the observations from Upper Atmospheric Research Satellite Microwave Limb Sounder (MLS). Both the MWFM simulation and MLS observations found strong wave activities over the high-latitude mountain ridges of Scandinavia, Central Eurasia, Alaska, southern Greenland in Northern Hemisphere, and Andes, New Zealand, Antarctic rim in Southern Hemisphere. These mountain waves are dominated by wave modes with downward phase progression and horizontal phase velocities opposite to the stratospheric jet-stream. Agreements of minor wave activities are also found at low- to mid-latitudes over Zagros Mountains of Middle East, Colorado Rocky Mountains, Appalachians, and Sierra Madres of Central America. Some differences between the MWFM results and MLS data are explained by different horizontal resolution between the model and observation, and the fact that MLS may also see the non-orographic wave sources, such as mesoscale storms and jet-stream instabilities. The findings from this model-measurement comparison study demonstrate that satellite instruments such as MLS can provide global data needed to characterize mountain wave sources, their inter-annual variations, and to improve gravity wave parameterizations in global climate and forecast models.
NASA Technical Reports Server (NTRS)
Roberts, Aaron
2005-01-01
New tools for data access and visualization promise to make the analysis of space plasma data both more efficient and more powerful, especially for answering questions about the global structure and dynamics of the Sun-Earth system. We will show how new existing tools (particularly the Virtual Space Physics Observatory-VSPO-and the Visual System for Browsing, Analysis and Retrieval of Data-ViSBARD; look for the acronyms in Google) already provide rapid access to such information as spacecraft orbits, browse plots, and detailed data, as well as visualizations that can quickly unite our view of multispacecraft observations. We will show movies illustrating multispacecraft observations of the solar wind and magnetosphere during a magnetic storm, and of simulations of 3 0-spacecraft observations derived from MHD simulations of the magnetosphere sampled along likely trajectories of the spacecraft for the MagCon mission. An important issue remaining to be solved is how best to integrate simulation data and services into the Virtual Observatory environment, and this talk will hopefully stimulate further discussion along these lines.
Fast Plasma Instrument for MMS: Simulation Results
NASA Technical Reports Server (NTRS)
Figueroa-Vinas, Adolfo; Adrian, Mark L.; Lobell, James V.; Simpson, David G.; Barrie, Alex; Winkert, George E.; Yeh, Pen-Shu; Moore, Thomas E.
2008-01-01
Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. The Dual Electron Spectrometer (DES) of the Fast Plasma Instrument (FPI) for MMS meets these demanding requirements by acquiring the electron velocity distribution functions (VDFs) for the full sky with high-resolution angular measurements every 30 ms. This will provide unprecedented access to electron scale dynamics within the reconnection diffusion region. The DES consists of eight half-top-hat energy analyzers. Each analyzer has a 6 deg. x 11.25 deg. Full-sky coverage is achieved by electrostatically stepping the FOV of each of the eight sensors through four discrete deflection look directions. Data compression and burst memory management will provide approximately 30 minutes of high time resolution data during each orbit of the four MMS spacecraft. Each spacecraft will intelligently downlink the data sequences that contain the greatest amount of temporal structure. Here we present the results of a simulation of the DES analyzer measurements, data compression and decompression, as well as ground-based analysis using as a seed re-processed Cluster/PEACE electron measurements. The Cluster/PEACE electron measurements have been reprocessed through virtual DES analyzers with their proper geometrical, energy, and timing scale factors and re-mapped via interpolation to the DES angular and energy phase-space sampling measurements. The results of the simulated DES measurements are analyzed and the full moments of the simulated VDFs are compared with those obtained from the Cluster/PEACE spectrometer using a standard quadrature moment, a newly implemented spectral spherical harmonic method, and a singular value decomposition method. Our preliminary moment calculations show a remarkable agreement within the uncertainties of the measurements, with the
NASA Astrophysics Data System (ADS)
Evrard, Rebecca L.; Ding, Yifeng
2018-01-01
Clouds play a large role in the Earth's global energy budget, but the impact of cirrus clouds is still widely questioned and researched. Cirrus clouds reside high in the atmosphere and due to cold temperatures are comprised of ice crystals. Gaining a better understanding of ice cloud optical properties and the distribution of cirrus clouds provides an explanation for the contribution of cirrus clouds to the global energy budget. Using radiative transfer models (RTMs), accurate simulations of cirrus clouds can enhance the understanding of the global energy budget as well as improve the use of global climate models. A newer, faster RTM such as the visible infrared imaging radiometer suite (VIIRS) fast radiative transfer model (VFRTM) is compared to a rigorous RTM such as the line-by-line radiative transfer model plus the discrete ordinates radiative transfer program. By comparing brightness temperature (BT) simulations from both models, the accuracy of the VFRTM can be obtained. This study shows root-mean-square error <0.2 K for BT difference using reanalysis data for atmospheric profiles and updated ice particle habit information from the moderate-resolution imaging spectroradiometer collection 6. At a higher resolution, the simulated results of the VFRTM are compared to the observations of VIIRS resulting in a <1.5 % error from the VFRTM for all cases. The VFRTM is validated and is an appropriate RTM to use for global cloud retrievals.
2015-01-01
Density is an easily adjusted variable in molecular dynamics (MD) simulations. Thus, pressure-jump (P-jump)-induced protein refolding, if it could be made fast enough, would be ideally suited for comparison with MD. Although pressure denaturation perturbs secondary structure less than temperature denaturation, protein refolding after a fast P-jump is not necessarily faster than that after a temperature jump. Recent P-jump refolding experiments on the helix bundle λ-repressor have shown evidence of a <3 μs burst phase, but also of a ∼1.5 ms “slow” phase of refolding, attributed to non-native helical structure frustrating microsecond refolding. Here we show that a λ-repressor mutant is nonetheless capable of refolding in a single explicit solvent MD trajectory in about 19 μs, indicating that the burst phase observed in experiments on the same mutant could produce native protein. The simulation reveals that after about 18.5 μs of conformational sampling, the productive structural rearrangement to the native state does not occur in a single swift step but is spread out over a brief series of helix and loop rearrangements that take about 0.9 μs. Our results support the molecular time scale inferred for λ-repressor from near-downhill folding experiments, where transition-state population can be seen experimentally, and also agrees with the transition-state transit time observed in slower folding proteins by single-molecule spectroscopy. PMID:24437525
Insights from Synthetic Star-forming Regions. I. Reliable Mock Observations from SPH Simulations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Koepferl, Christine M.; Robitaille, Thomas P.; Biscani, Francesco
Through synthetic observations of a hydrodynamical simulation of an evolving star-forming region, we assess how the choice of observational techniques affects the measurements of properties that trace star formation. Testing and calibrating observational measurements requires synthetic observations that are as realistic as possible. In this part of the series (Paper I), we explore different techniques for mapping the distributions of densities and temperatures from the particle-based simulations onto a Voronoi mesh suitable for radiative transfer and consequently explore their accuracy. We further test different ways to set up the radiative transfer in order to produce realistic synthetic observations. We give amore » detailed description of all methods and ultimately recommend techniques. We have found that the flux around 20 μ m is strongly overestimated when blindly coupling the dust radiative transfer temperature with the hydrodynamical gas temperature. We find that when instead assuming a constant background dust temperature in addition to the radiative transfer heating, the recovered flux is consistent with actual observations. We present around 5800 realistic synthetic observations for Spitzer and Herschel bands, at different evolutionary time-steps, distances, and orientations. In the upcoming papers of this series (Papers II, III, and IV), we will test and calibrate measurements of the star formation rate, gas mass, and the star formation efficiency using our realistic synthetic observations.« less
Numerical simulation of whistler-triggered VLF emissions observed in Antartica
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nunn, D.; Smith, A.J.
1996-03-01
The authors have extracted from VLF databases from British Antarctica Survey data taken at Halley and Faraday stations, examples of whistler-triggered emissions (WTE). The WTE are relatively narrow band emissions triggered by natural background whistlers undergoing nonlinear wave particle interactions generally in the equatorial regions. They occur with either rising or falling frequency relative to the triggering waves. Using a Vlasov type code the authors are able to simulate the types of emissions which are observed. 24 refs., 8 figs., 3 tabs.
MMS observations and hybrid simulations of rippled and reforming quasi-parallel shocks
NASA Astrophysics Data System (ADS)
Gingell, I.; Schwartz, S. J.; Burgess, D.; Johlander, A.; Russell, C. T.; Burch, J. L.; Ergun, R.; Fuselier, S. A.; Gershman, D. J.; Giles, B. L.; Goodrich, K.; Khotyaintsev, Y. V.; Lavraud, B.; Lindqvist, P. A.; Strangeway, R. J.; Trattner, K. J.; Torbert, R. B.; Wilder, F. D.
2017-12-01
Surface ripples, i.e. deviations in the nominal local shock orientation, are expected to propagate in the ramp and overshoot of collisionless shocks. These ripples have typically been associated with observations and simulations of quasi-perpendicular shocks. We present observations of a crossing of Earth's marginally quasi-parallel (θBn ˜ 45°) bow shock by the MMS spacecraft on 2015-11-27 06:01:44 UTC, for which we identify signatures consistent with a propagating surface ripple. In order to demonstrate the differences between ripples at quasi-perpendicular and quasi-parallel shocks, we also present two-dimensional hybrid simulations over a range of shock normal angles θBn under the observed solar wind conditions. We show that in the quasi-parallel cases surface ripples are transient phenomena modulated by the cyclic reformation of the shock front. These ripples develop faster than an ion gyroperiod and only during the period of the reformation cycle when a newly developed shock ramp is unaffected by turbulence in the foot. We conclude that the change of properties of the surface ripple observed by MMS while crossing Earth's quasi-parallel bow shock are consistent with the influence of cyclic reformation on shock structure. Given that both surface ripples and cyclic reformation are expected to affect the acceleration of electrons within the shock, the interaction of these phenomena and any other sources of shock non-stationary are important for models of particle acceleration. We therefore discuss signatures of electron heating and acceleration in several rippled shocks observed by MMS.
NASA Astrophysics Data System (ADS)
Barbosa, Marcos; Alves, Maria Virginia; Simões Junior, Fernando
2016-04-01
In plasmas out of thermodynamic equilibrium the particle velocity distribution can be described by the so called Kappa distribution. These velocity distribution functions are a generalization of the Maxwellian distribution. Since 1960, Kappa velocity distributions were observed in several regions of interplanetary space and astrophysical plasmas. Using KEMPO1 particle simulation code, modified to introduce Kappa distribution functions as initial conditions for particle velocities, the normal modes of propagation were analyzed in a plasma containing two species of electrons with different temperatures and densities and ions as a third specie.This type of plasma is usually found in magnetospheres such as in Saturn. Numerical solutions for the dispersion relation for such a plasma predict the presence of an electron-acoustic mode, besides the Langmuir and ion-acoustic modes. In the presence of an ambient magnetic field, the perpendicular propagation (Bernstein mode) also changes, as compared to a Maxwellian plasma, due to the Kappa distribution function. Here results for simulations with and without external magnetic field are presented. The parameters for the initial conditions in the simulations were obtained from the Cassini spacecraft data. Simulation results are compared with numerical solutions of the dispersion relation obtained in the literature and they are in good agreement.
NASA Astrophysics Data System (ADS)
Feng, Xingru; Li, Mingjie; Yin, Baoshu; Yang, Dezhou; Yang, Hongwei
2018-06-01
This is a study of the storm surge trends in some of the typhoon-prone coastal areas of China. An unstructured-grid, storm surge-wave-tide coupled model was established for the coastal areas of Zhejiang, Fujian and Guangdong provinces. The coupled model has a high resolution in coastal areas, and the simulated results compared well with the in situ observations and satellite altimeter data. The typhoon-induced storm surges along the coast of the study areas were simulated based on the established coupled model for the past 20 years (1997-2016). The simulated results were used to analyze the trends of the storm surges in the study area. The extreme storm surge trends along the central coast of Fujian Province reached up to 0.06 m/y, significant at the 90% confidence level. The duration of the storm surges greater than 1.0 and 0.7 m had an increasing trend along the coastal area of northern Fujian Province, significant at confidence levels of 70%-91%. The simulated trends of the extreme storm surges were also validated by observations from two tide gauge stations. Further studies show that the correlation coefficient (RTE) between the duration of the storm surge greater than 1 m and the annual ENSO index can reach as high as 0.62, significant at the 99% confidence level. This occurred in a location where the storm surge trend was not significant. For the areas with significant increasing storm surge trends, RTE was small and not significant. This study identified the storm surge trends for the full complex coastline of the study area. These results are useful both for coastal management by the government and for coastal engineering design.
Lai, Anita; Haligua, Alexis; Dylan Bould, M; Everett, Tobias; Gale, Mark; Pigford, Ashlee-Ann; Boet, Sylvain
2016-08-01
Simulation training has been shown to be an effective way to teach crisis resource management (CRM) skills. Deliberate practice theory states that learners need to actively practice so that learning is effective. However, many residency programs have limited opportunities for learners to be "active" participants in simulation exercises. This study compares the effectiveness of learning CRM skills when being an active participant versus being an observer participant in simulation followed by a debriefing. Participants were randomized to two groups: active or observer. Active participants managed a simulated crisis scenario (pre-test) while paired observer participants viewed the scenario via video transmission. Then, a trained instructor debriefed participants on CRM principles. On the same day, each participant individually managed another simulated crisis scenario (post-test) and completed a post-test questionnaire. Two independent, blinded raters evaluated all videos using the Ottawa Global Rating Scale (GRS). Thirty-nine residents were included in the analysis. Normally distributed data were analyzed using paired and unpaired t-tests. Inter-rater reliability was 0.64. Active participants significantly improved from pre-test to post-test (P=0.015). There was no significant difference between the post-test performance of active participants compared to observer participants (P=0.12). We found that learning CRM principles was not superior when learners were active participants compared to being observers followed by debriefing. These findings challenge the deliberate practice theory claiming that learning requires active practice. Assigning residents as observers in simulation training and involving them in debriefing is still beneficial. Copyright © 2016 Société française d'anesthésie et de réanimation (Sfar). Published by Elsevier Masson SAS. All rights reserved.
NASA Astrophysics Data System (ADS)
Pu, Z.; Yu, Y.
2016-12-01
The prediction of Hurricane Joaquin's hairpin clockwise during 1 and 2 October 2015 presents a forecasting challenge during real-time numerical weather prediction, as tracks of several major numerical weather prediction models differ from each other. To investigate the large-scale environment and hurricane inner-core structures related to the hairpin turn of Joaquin, a series of high-resolution mesoscale numerical simulations of Hurricane Joaquin had been performed with an advanced research version of the Weather Research and Forecasting (WRF) model. The outcomes were compared with the observations obtained from the US Office of Naval Research's Tropical Cyclone Intensity (TCI) Experiment during 2015 hurricane season. Specifically, five groups of sensitivity experiments with different cumulus, boundary layer, and microphysical schemes as well as different initial and boundary conditions and initial times in WRF simulations had been performed. It is found that the choice of the cumulus parameterization scheme plays a significant role in reproducing reasonable track forecast during Joaquin's hairpin turn. The mid-level environmental steering flows can be the reason that leads to different tracks in the simulations with different cumulus schemes. In addition, differences in the distribution and amounts of the latent heating over the inner-core region are associated with discrepancies in the simulated intensity among different experiments. Detailed simulation results, comparison with TCI-2015 observations, and comprehensive diagnoses will be presented.
NASA Astrophysics Data System (ADS)
Stanfield, Ryan Evan
outgoing longwave radiation (OLR) is 3 W m-2 higher than observations. Finally, cloud radiative effects (CRE) are calculated and compared with observations to fully assess the impact of clouds on the TOA radiation budgets. The difference in clear-sky reflected SW flux between model and observation is only +4 W m-2 while the SW CRE difference is up to 17 W m-2, indicating that most of the bias in SW CRE results from the all-sky bias between the model and observation. A sizeable negative bias of 10 W m-2 in simulated clear-sky OLR has been found due to a dry bias in calculating observed clear-sky OLR and lack of upper-level water vapor at the 100-mb level in the model. The dry bias impacts CRE LW, with the model undersimulating by 13 W m-2. The CRE NET difference is only 5 W m-2 due to the cancellation of SW and LW CRE biases.
The atmospheric boundary layer in the CSIRO global climate model: simulations versus observations
NASA Astrophysics Data System (ADS)
Garratt, J. R.; Rotstayn, L. D.; Krummel, P. B.
2002-07-01
A 5-year simulation of the atmospheric boundary layer in the CSIRO global climate model (GCM) is compared with detailed boundary-layer observations at six locations, two over the ocean and four over land. Field observations, in the form of surface fluxes and vertical profiles of wind, temperature and humidity, are generally available for each hour over periods of one month or more in a single year. GCM simulations are for specific months corresponding to the field observations, for each of five years. At three of the four land sites (two in Australia, one in south-eastern France), modelled rainfall was close to the observed climatological values, but was significantly in deficit at the fourth (Kansas, USA). Observed rainfall during the field expeditions was close to climatology at all four sites. At the Kansas site, modelled screen temperatures (Tsc), diurnal temperature amplitude and sensible heat flux (H) were significantly higher than observed, with modelled evaporation (E) much lower. At the other three land sites, there is excellent correspondence between the diurnal amplitude and phase and absolute values of each variable (Tsc, H, E). Mean monthly vertical profiles for specific times of the day show strong similarities: over land and ocean in vertical shape and absolute values of variables, and in the mixed-layer and nocturnal-inversion depths (over land) and the height of the elevated inversion or height of the cloud layer (over the sea). Of special interest is the presence climatologically of early morning humidity inversions related to dewfall and of nocturnal low-level jets; such features are found in the GCM simulations. The observed day-to-day variability in vertical structure is captured well in the model for most sites, including, over a whole month, the temperature range at all levels in the boundary layer, and the mix of shallow and deep mixed layers. Weaknesses or unrealistic structure include the following, (a) unrealistic model mixed
NASA Astrophysics Data System (ADS)
Zhang, Lei; Dong, Xiquan; Kennedy, Aaron; Xi, Baike; Li, Zhanqing
2017-03-01
The planetary boundary layer turbulence and moist convection parameterizations have been modified recently in the NASA Goddard Institute for Space Studies (GISS) Model E2 atmospheric general circulation model (GCM; post-CMIP5, hereafter P5). In this study, single column model (SCM P5) simulated cloud fractions (CFs), cloud liquid water paths (LWPs) and precipitation were compared with Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) groundbased observations made during the period 2002-08. CMIP5 SCM simulations and GCM outputs over the ARM SGP region were also used in the comparison to identify whether the causes of cloud and precipitation biases resulted from either the physical parameterization or the dynamic scheme. The comparison showed that the CMIP5 SCM has difficulties in simulating the vertical structure and seasonal variation of low-level clouds. The new scheme implemented in the turbulence parameterization led to significantly improved cloud simulations in P5. It was found that the SCM is sensitive to the relaxation time scale. When the relaxation time increased from 3 to 24 h, SCM P5-simulated CFs and LWPs showed a moderate increase (10%-20%) but precipitation increased significantly (56%), which agreed better with observations despite the less accurate atmospheric state. Annual averages among the GCM and SCM simulations were almost the same, but their respective seasonal variations were out of phase. This suggests that the same physical cloud parameterization can generate similar statistical results over a long time period, but different dynamics drive the differences in seasonal variations. This study can potentially provide guidance for the further development of the GISS model.
NASA Astrophysics Data System (ADS)
Hadamcik, E.; Levasseur-Regourd, A. C.
2007-08-01
1.Introduction Remote observations of solar light scattered by cometary dust particles provide information on the dust properties for a large variety of comets, in complement to the exceptional in-situ observations (with or without sample returns). The scattered light is partially linearly polarized, with a polarization degree depending on the geometry of observations (phase angle ?) and on the physical properties of the particles. Differences in polarization have been found in cometary comae, pointing to different physical properties of the dust (e.g. sizes of the grains, of the aggregates, structures and porosities, complex refractive indices) [1, 2]. Such differences, as well as an observed polarimetric wavelength effect, tend to show that large aggregates made of submicron-sized grains could be present in some cometary comae regions [3, 4]. On the opposite, more compact particles seem to be present in other comae regions and/or comets [5, 6]. 2. Results We will present observations of different comets. The variations of the dust properties in the coma and their evolution will be discussed. The results will be compared to the results obtained by other observational techniques. On the images of comet 9P/Tempel 1 (at ?=41°) some hours after Deep Impact, two kinds of dust particles are detected: more compact particles with small velocities and fluffy particles ejected by the impact with larger velocities. On the images of comet 73P/Schwassmann-Wachmann 3, in the tail direction of fragment B, a disruption is observed. The dust coma around fragment C is more symmetric. For both A and B, important dust jets are ejected by the nucleus, which are visible on the intensity images in the solar and antisolar directions, and on the polarization maps. 3. Interpretation and conclusion Numerical (7,8,9) and experimental simulations provide an interpretation of the observations in terms of the physical properties of the particles. Experimental simulations have been performed on
NASA Astrophysics Data System (ADS)
Ahmadalipour, Ali; Moradkhani, Hamid
2017-12-01
Hydrologic modeling is one of the primary tools utilized for drought monitoring and drought early warning systems. Several sources of uncertainty in hydrologic modeling have been addressed in the literature. However, few studies have assessed the uncertainty of gridded observation datasets from a drought monitoring perspective. This study provides a hydrologic modeling oriented analysis of the gridded observation data uncertainties over the Pacific Northwest (PNW) and its implications on drought assessment. We utilized a recently developed 100-member ensemble-based observed forcing data to simulate hydrologic fluxes at 1/8° spatial resolution using Variable Infiltration Capacity (VIC) model, and compared the results with a deterministic observation. Meteorological and hydrological droughts are studied at multiple timescales over the basin, and seasonal long-term trends and variations of drought extent is investigated for each case. Results reveal large uncertainty of observed datasets at monthly timescale, with systematic differences for temperature records, mainly due to different lapse rates. The uncertainty eventuates in large disparities of drought characteristics. In general, an increasing trend is found for winter drought extent across the PNW. Furthermore, a ∼3% decrease per decade is detected for snow water equivalent (SWE) over the PNW, with the region being more susceptible to SWE variations of the northern Rockies than the western Cascades. The agricultural areas of southern Idaho demonstrate decreasing trend of natural soil moisture as a result of precipitation decline, which implies higher appeal for anthropogenic water storage and irrigation systems.
NASA Astrophysics Data System (ADS)
Madhulatha, A.; Rajeevan, M.; Bhowmik, S. K. Roy; Das, A. K.
2018-01-01
The primary goal of present study is to investigate the impact of assimilation of conventional and satellite radiance observations in simulating the mesoscale convective system (MCS) formed over south east India. An assimilation methodology based on Weather Research and Forecasting model three dimensional variational data assimilation is considered. Few numerical experiments are carried out to examine the individual and combined impact of conventional and non-conventional (satellite radiance) observations. After the successful inclusion of additional observations, strong analysis increments of temperature and moisture fields are noticed and contributed to significant improvement in model's initial fields. The resulting model simulations are able to successfully reproduce the prominent synoptic features responsible for the initiation of MCS. Among all the experiments, the final experiment in which both conventional and satellite radiance observations assimilated has showed considerable impact on the prediction of MCS. The location, genesis, intensity, propagation and development of rain bands associated with the MCS are simulated reasonably well. The biases of simulated temperature, moisture and wind fields at surface and different pressure levels are reduced. Thermodynamic, dynamic and vertical structure of convective cells associated with the passage of MCS are well captured. Spatial distribution of rainfall is fairly reproduced and comparable to TRMM observations. It is demonstrated that incorporation of conventional and satellite radiance observations improved the local and synoptic representation of temperature, moisture fields from surface to different levels of atmosphere. This study highlights the importance of assimilation of conventional and satellite radiances in improving the models initial conditions and simulation of MCS.
NASA Astrophysics Data System (ADS)
Yosritzal; Kemal, B. M.; Purnawan; Putra, H.
2018-04-01
This paper presents a simulation study to observe the walking speed of evacuee in the case of tsunami evacuation in Padang, West Sumatera, Indonesia. A number of 9 volunteers, 6 observers, 1 route with 5 segments were involved in the simulation. The chosen route is the easiest path and the volunteers were ordered to walk in hurry to a particular place which was assumed as a shelter. The observers were placed at some particular places to record the time when an evacuee passes their place. The distance between the observers were measured using a manual distance meter. The study found that the average walking speed during the evacuation was 1.419 m/s. Walking speed is varied by age and gender of the evacuee.
Daniels, Stijn; Vanrie, Jan; Dreesen, An; Brijs, Tom
2010-05-01
Although speed limits are indicated by road signs, road users are not always aware, while driving, of the actual speed limit on a given road segment. The Roads and Traffic Agency developed additional road markings in order to support driver decisions on speed on 70 km/h roads in Flanders-Belgium. In this paper the results are presented of two evaluation studies, both a field study and a simulator study, on the effects of the additional road markings on speed behaviour. The results of the field study showed no substantial effect of the markings on speed behaviour. Neither did the simulator study, with slightly different stimuli. Nevertheless an effect on lateral position was noticed in the simulator study, showing at least some effect of the markings. The role of conspicuity of design elements and expectations towards traffic environments is discussed. Both studies illustrate well some strengths and weaknesses of observational field studies compared to experimental simulator studies. Copyright (c) 2009 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Colarco, P. R.; Gasso, S.; Jethva, H. T.; Buchard, V.; Ahn, C.; Torres, O.; daSilva, A.
2016-12-01
Output from the NASA Goddard Earth Observing System, version 5 (GEOS-5) Earth system model is used to simulate the top-of-atmosphere 354 and 388 nm radiances observed by the Ozone Monitoring Instrument (OMI) onboard the Aura spacecraft. The principle purpose of developing this simulator tool is to compute from the modeled fields the so-called OMI Aerosol Index (AI), which is a more fundamental retrieval product than higher level products such as the aerosol optical depth (AOD) or absorbing aerosol optical depth (AAOD). This lays the groundwork for eventually developing a capability to assimilate either the OMI AI or its radiances, which would provide further constraint on aerosol loading and absorption properties for global models. We extend the use of the simulator capability to understand the nature of the OMI aerosol retrieval algorithms themselves in an Observing System Simulation Experiment (OSSE). The simulated radiances are used to calculate the AI from the modeled fields. These radiances are also provided to the OMI aerosol algorithms, which return their own retrievals of the AI, AOD, and AAOD. Our assessment reveals that the OMI-retrieved AI can be mostly harmonized with the model-derived AI given the same radiances provided a common surface pressure field is assumed. This is important because the operational OMI algorithms presently assume a fixed pressure field, while the contribution of molecular scattering to the actual OMI signal in fact responds to the actual atmospheric pressure profile, which is accounted for in our OSSE by using GEOS-5 produced atmospheric reanalyses. Other differences between the model and OMI AI are discussed, and we present a preliminary assessment of the OMI AOD and AAOD products with respect to the known inputs from the GEOS-5 simulation.
Mirams, Gary R; Davies, Mark R; Brough, Stephen J; Bridgland-Taylor, Matthew H; Cui, Yi; Gavaghan, David J; Abi-Gerges, Najah
2014-01-01
Detection of drug-induced pro-arrhythmic risk is a primary concern for pharmaceutical companies and regulators. Increased risk is linked to prolongation of the QT interval on the body surface ECG. Recent studies have shown that multiple ion channel interactions can be required to predict changes in ventricular repolarisation and therefore QT intervals. In this study we attempt to predict the result of the human clinical Thorough QT (TQT) study, using multiple ion channel screening which is available early in drug development. Ion current reduction was measured, in the presence of marketed drugs which have had a TQT study, for channels encoded by hERG, CaV1.2, NaV1.5, KCNQ1/MinK, and Kv4.3/KChIP2.2. The screen was performed on two platforms - IonWorks Quattro (all 5 channels, 34 compounds), and IonWorks Barracuda (hERG & CaV1.2, 26 compounds). Concentration-effect curves were fitted to the resulting data, and used to calculate a percentage reduction in each current at a given concentration. Action potential simulations were then performed using the ten Tusscher and Panfilov (2006), Grandi et al. (2010) and O'Hara et al. (2011) human ventricular action potential models, pacing at 1Hz and running to steady state, for a range of concentrations. We compared simulated action potential duration predictions with the QT prolongation observed in the TQT studies. At the estimated concentrations, simulations tended to underestimate any observed QT prolongation. When considering a wider range of concentrations, and conventional patch clamp rather than screening data for hERG, prolongation of ≥5ms was predicted with up to 79% sensitivity and 100% specificity. This study provides a proof-of-principle for the prediction of human TQT study results using data available early in drug development. We highlight a number of areas that need refinement to improve the method's predictive power, but the results suggest that such approaches will provide a useful tool in cardiac safety
Chen, Gong; Kong, Xian; Zhu, Jingying; Lu, Diannan; Liu, Zheng
2015-04-28
While the conjugation of enzymes with ABA copolymers has resulted in increased enzymatic activities in organic solvents, by several orders of magnitude, the underpinning mechanism has not been fully uncovered, particularly at the molecular level. In the present work, a coarse-grained molecular dynamics simulation of cytochrome c (Cyt c) conjugated with a PEO-PPO-PEO block copolymer (ABA) in toluene was simulated with Cyt c as a control. It is shown that the hydrophilic segments (PEO) of the conjugated block copolymer molecules tend to entangle around the hydrophilic patch of Cyt c, while the hydrophobic segments (PPO) extend into the toluene. At a lower temperature, the PEO tails tend to form a hairpin structure outside the conjugated protein, whereas the Cyt c-ABA conjugates tend to form larger aggregates. At a higher temperature, however, the PEO tails tend to adsorb onto the hydrophilic protein surface, thus improving the suspension of the Cyt c-ABA conjugates and, consequently, the contact with the substrate. Moreover, the temperature increase drives the conformational transition of the active site of Cyt c-ABA from an "inactive state" to an "activated state" and thus results in an enhanced activity. To validate the above simulations, Cyt c was conjugated to F127, an extensively used ABA copolymer. By elevating the temperature, a decrease in the average size of the Cyt c-F127 conjugates along with a great increase in the apparent activity in toluene was observed, as can be predicted from the molecular dynamics simulation. The above mentioned molecular simulations offer a molecular insight into the temperature-responsive behaviour of protein-ABA copolymers, which is helpful for the design and application of enzyme-polymer conjugates for industrial biocatalysis.
NASA Astrophysics Data System (ADS)
Klimczak, Marcin; Bojarski, Jacek; Ziembicki, Piotr; Kęskiewicz, Piotr
2017-11-01
The requirements concerning energy performance of buildings and their internal installations, particularly HVAC systems, have been growing continuously in Poland and all over the world. The existing, traditional calculation methods following from the static heat exchange model are frequently not sufficient for a reasonable heating design of a building. Both in Poland and elsewhere in the world, methods and software are employed which allow a detailed simulation of the heating and moisture conditions in a building, and also an analysis of the performance of HVAC systems within a building. However, these systems are usually difficult in use and complex. In addition, the development of a simulation model that is sufficiently adequate to the real building requires considerable time involvement of a designer, is time-consuming and laborious. A simplification of the simulation model of a building renders it possible to reduce the costs of computer simulations. The paper analyses in detail the effect of introducing a number of different variants of the simulation model developed in Design Builder on the quality of final results obtained. The objective of this analysis is to find simplifications which allow obtaining simulation results which have an acceptable level of deviations from the detailed model, thus facilitating a quick energy performance analysis of a given building.
Observing System Simulation Experiment (OSSE) for a future Doppler Wind Lidar satellite in Japan:
NASA Astrophysics Data System (ADS)
Baron, Philippe; Ishii, Shoken; Okamoto, Kozo
2017-04-01
A feasibility study of tropospheric wind measurements by a coherent Doppler lidar aboard a super-low-altitude satellite is being conducted in Japan. We consider a coherent lidar with a laser light source at 2.05 μm whose characteristics correspond to an existing ground-based instrument (power=3.75 W, PRF=30 Hz and pulse width=200 ns). An Observing System Simulation Experiment (OSSE) has been implemented based on the Sensitivity Observing System experiment (SOSE) developed at the Japanese Meteorological-Research-Institute using the Japan Meteorological Agency global Numerical Weather Prediction model. The measurement simulator uses wind, aerosol and cloud 3-d global fields from the OSSE speudo-truth and the aerosol model MASINGAR. In this presentation, we will first discuss the measurement performances. Considering measurement horizontal resolutions of 100 km along the orbit track, we found that below 3 km, the median horizontal wind error is between 0.8-1 m/s for a vertical resolution of 0.5 km, and that near 50% of the data are valid measurements. Decreasing the vertical resolution to 1 km allows us to maintain similar performances up to 8 km almost over most latitudes. Above, the performances significantly fall down but a relatively good percentage of valid measurements (20-40%) are still found near the tropics where cirrus clouds frequently occur. The potential of the instrument to improve weather prediction models will be discussed using the OSSE results obtained for both polar and low inclination orbit satellites. The first results show positive improvements of short-term forecasts (<48 hours), in particular, on the wind speed at 850 hPa and 250 hPa. S. Ishii, K. Okamoto, P. Baron, T. Kubota, Y. Satoh, D. Sakaizawa, T. Ishibashi, T. Y. Tanaka, K. Yamashita, S. Ochiai, K. Gamo, M. Yasui, R. Oki, M. Satoh, and T. Iwasaki, "Measurement performance assessment of future space-borne Doppler wind lidar", SOLA, vol. 12, pp. 55-59, 2016. S. Ishii et al., "Feasibility
NASA Astrophysics Data System (ADS)
Johnson, Marcus; Jung, Youngsun; Dawson, Daniel; Supinie, Timothy; Xue, Ming; Park, Jongsook; Lee, Yong-Hee
2018-07-01
The UK Met Office Unified Model (UM) is employed by many weather forecasting agencies around the globe. This model is designed to run across spatial and time scales and known to produce skillful predictions for large-scale weather systems. However, the model has only recently begun running operationally at horizontal grid spacings of ˜1.5 km [e.g., at the UK Met Office and the Korea Meteorological Administration (KMA)]. As its microphysics scheme was originally designed and tuned for large-scale precipitation systems, we investigate the performance of UM microphysics to determine potential inherent biases or weaknesses. Two rainfall cases from the KMA forecasting system are considered in this study: a Changma (quasi-stationary) front, and Typhoon Sanba (2012). The UM output is compared to polarimetric radar observations in terms of simulated polarimetric radar variables. Results show that the UM generally underpredicts median reflectivity in stratiform rain, producing high reflectivity cores and precipitation gaps between them. This is partially due to the diagnostic rain intercept parameter formulation used in the one-moment microphysics scheme. Model drop size is generally both underand overpredicted compared to observations. UM frozen hydrometeors favor generic ice (crystals and snow) rather than graupel, which is reasonable for Changma and typhoon cases. The model performed best with the typhoon case in terms of simulated precipitation coverage.
NASA Astrophysics Data System (ADS)
Abbasnezhadi, K.; Rasmussen, P. F.; Stadnyk, T.
2014-12-01
To gain a better understanding of the spatiotemporal distribution of rainfall over the Churchill River basin, this study was undertaken. The research incorporates gridded precipitation data from the Canadian Precipitation Analysis (CaPA) system. CaPA has been developed by Environment Canada and provides near real-time precipitation estimates on a 10 km by 10 km grid over North America at a temporal resolution of 6 hours. The spatial fields are generated by combining forecasts from the Global Environmental Multiscale (GEM) model with precipitation observations from the network of synoptic weather stations. CaPA's skill is highly influenced by the number of weather stations in the region of interest as well as by the quality of the observations. In an attempt to evaluate the performance of CaPA as a function of the density of the weather station network, a dual-stage design algorithm to simulate CaPA is proposed which incorporates generated weather fields. More specifically, we are adopting a controlled design algorithm which is generally known as Observing System Simulation Experiment (OSSE). The advantage of using the experiment is that one can define reference precipitation fields assumed to represent the true state of rainfall over the region of interest. In the first stage of the defined OSSE, a coupled stochastic model of precipitation and temperature gridded fields is calibrated and validated. The performance of the generator is then validated by comparing model statistics with observed statistics and by using the generated samples as input to the WATFLOOD™ hydrologic model. In the second stage of the experiment, in order to account for the systematic error of station observations and GEM fields, representative errors are to be added to the reference field using by-products of CaPA's variographic analysis. These by-products explain the variance of station observations and background errors.
NASA Technical Reports Server (NTRS)
Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Kapernick, Richard
2007-01-01
Non-nuclear testing can be a valuable tool in the development of a space nuclear power system, providing system characterization data and allowing one to work through various fabrication, assembly and integration issues without the cost and time associated with a full ground nuclear test. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Testing with non-optimized heater elements allows one to assess thermal, heat transfer. and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. High fidelity thermal simulators that match both the static and the dynamic fuel pin performance that would be observed in an operating, fueled nuclear reactor can vastly increase the value of non-nuclear test results. With optimized simulators, the integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and fueled nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response characteristics and assess potential design improvements at relatively small fiscal investment. Initial conceptual thermal simulator designs are determined by simple one-dimensional analysis at a single axial location and at steady state conditions; feasible concepts are then input into a detailed three-dimensional model for comparison to expected fuel pin performance. Static and dynamic fuel pin performance for a proposed reactor design is determined using SINDA/FLUINT thermal analysis software, and comparison is made between the expected nuclear performance and the performance of conceptual thermal simulator designs. Through a series of iterative analyses, a conceptual high fidelity design is developed
Simulated and observed 2010 floodwater elevations in the Pawcatuck and Wood Rivers, Rhode Island
Zarriello, Phillip J.; Straub, David E.; Smith, Thor E.
2014-01-01
Heavy, persistent rains from late February through March 2010 caused severe flooding that set, or nearly set, peaks of record for streamflows and water levels at many long-term U.S. Geological Survey streamgages in Rhode Island. In response to this flood, hydraulic models of Pawcatuck River (26.9 miles) and Wood River (11.6 miles) were updated from the most recent approved U.S. Department of Homeland Security-Federal Emergency Management Agency flood insurance study (FIS) to simulate water-surface elevations (WSEs) for specified flows and boundary conditions. The hydraulic models were updated to Hydrologic Engineering Center-River Analysis System (HEC-RAS) using steady-state simulations and incorporate new field-survey data at structures, high resolution land-surface elevation data, and updated flood flows from a related study. The models were used to simulate the 0.2-percent annual exceedance probability (AEP) flood, which is the AEP determined for the 2010 flood in the Pawcatuck and Wood Rivers. The simulated WSEs were compared to high-water mark (HWM) elevation data obtained in a related study following the March–April 2010 flood, which included 39 HWMs along the Pawcatuck River and 11 HWMs along the Wood River. The 2010 peak flow generally was larger than the 0.2-percent AEP flow, which, in part, resulted in the FIS and updated model WSEs to be lower than the 2010 HWMs. The 2010 HWMs for the Pawcatuck River averaged about 1.6 feet (ft) higher than the 0.2-percent AEP WSEs simulated in the updated model and 2.5 ft higher than the WSEs in the FIS. The 2010 HWMs for the Wood River averaged about 1.3 ft higher than the WSEs simulated in the updated model and 2.5 ft higher than the WSEs in the FIS. The improved agreement of the updated simulated water elevations to observed 2010 HWMs provides a measure of the hydraulic model performance, which indicates the updated models better represent flooding at other AEPs than the existing FIS models.
Results of a joint NOAA/NASA sounder simulation study
NASA Technical Reports Server (NTRS)
Phillips, N.; Susskind, Joel; Mcmillin, L.
1988-01-01
This paper presents the results of a joint NOAA and NASA sounder simulation study in which the accuracies of atmospheric temperature profiles and surface skin temperature measuremnents retrieved from two sounders were compared: (1) the currently used IR temperature sounder HIRS2 (High-resolution Infrared Radiation Sounder 2); and (2) the recently proposed high-spectral-resolution IR sounder AMTS (Advanced Moisture and Temperature Sounder). Simulations were conducted for both clear and partial cloud conditions. Data were analyzed at NASA using a physical inversion technique and at NOAA using a statistical technique. Results show significant improvement of AMTS compared to HIRS2 for both clear and cloudy conditions. The improvements are indicated by both methods of data analysis, but the physical retrievals outperform the statistical retrievals.
[Results of Simulation Studies
NASA Technical Reports Server (NTRS)
2003-01-01
Lattice Monte Carlo and off-lattice molecular dynamics simulations of h(sub 1)t(sub 4) and h(sub 4)t(sub l) (head/tail) amphiphile solutions have been performed as a function of surfactant concentration and temperature. The lattice and off-lattice systems exhibit quite different self-assembly behavior at equivalent thermodynamic conditions. We found that in the weakly aggregating regime (no preferred-size micelles), all models yield similar micelle size distributions at the same average aggregation number, albeit at different thermodynamic conditions (temperatures). In the strongly aggregating regime, this mapping between models (through temperature adjustment) fails, and the models exhibit qualitatively different micellization behavior. Incipient micellization in a model self-associating telechelic polymer solution results in a network with a transient elastic response that decays by a two-step relaxation: the first is due to a heterogeneous jump-diffusion process involving entrapment of end-groups within well-defined clusters and this is followed by rapid diffusion to neighboring clusters and a decay (terminal relaxation) due to cluster disintegration. The viscoelastic response of the solution manifests characteristics of a glass transition and entangled polymer network.
NASA Technical Reports Server (NTRS)
Olsen, Mark A.; Douglass, Anne R.; Newman, Paul A.; Gille, John C.; Nardi, Bruno; Yudin, Valery A.; Kinnison, Douglas E.; Khosravi, Rashid
2008-01-01
On 26 January 2006, the High Resolution Dynamic Limb Sounder (HIRDLS) observed low mixing ratios of ozone and nitric acid in an approximately 2 km vertical layer near 100 hPa extending from the subtropics to 55 degrees N over North America. The subsequent evolution of the layer is simulated with the Global Modeling Initiative (GMI) model and substantiated with HIRDLS observations. Air with low mixing ratios of ozone is transported poleward to 80 degrees N. Although there is evidence of mixing with extratropical air and diabatic descent, much of the tropical intrusion returns to the subtropics. This study demonstrates that HIRDLS and the GMI model are capable of resolving thin intrusion events. The observations combined with simulation are a first step towards development of a quantitative understanding of the lower stratospheric ozone budget.
NASA Technical Reports Server (NTRS)
Pierce, R. B.; Remsberg, Ellis E.; Fairlie, T. D.; Blackshear, W. T.; Grose, William L.; Turner, Richard E.
1992-01-01
Lagrangian area diagnostics and trajectory techniques are used to investigate the radiative and dynamical characteristics of a spontaneous sudden warming which occurred during a 2-yr Langley Research Center model simulation. The ability of the Langley Research Center GCM to simulate the major features of the stratospheric circulation during such highly disturbed periods is illustrated by comparison of the simulated warming to the observed circulation during the LIMS observation period. The apparent sink of vortex area associated with Rossby wave-breaking accounts for the majority of the reduction of the size of the vortex and also acts to offset the radiatively driven increase in the area occupied by the 'surf zone'. Trajectory analysis of selected material lines substantiates the conclusions from the area diagnostics.
Comparison of simulation and experimental results for a model aqueous tert-butanol solution
NASA Astrophysics Data System (ADS)
Overduin, S. D.; Patey, G. N.
2017-07-01
Molecular dynamics simulations are used to investigate the behavior of aqueous tert-butanol (TBA) solutions for a range of temperatures, using the CHARMM generalized force field (CGenFF) to model TBA and the TIP4P/2005 or TIP4P-Ew water model. Simulation results for the density, isothermal compressibility, constant pressure heat capacity, and self-diffusion coefficients are in good accord with experimental measurements. Agreement with the experiment is particularly good at low TBA concentration, where experiments have revealed anomalies in a number of thermodynamic properties. Importantly, the CGenFF model does not exhibit liquid-liquid demixing at temperatures between 290 and 320 K (for systems of 32 000 molecules), in contrast with the situation for several other common TBA models [R. Gupta and G. N. Patey, J. Chem. Phys. 137, 034509 (2012)]. However, whereas real water and TBA are miscible at all temperatures where the liquid is stable, we observe some evidence of demixing at 340 K and above. To evaluate the structural properties at low concentrations, we compare with both neutron scattering and recent spectroscopic measurements. This reveals that while the CGenFF model is a definite improvement over other models that have been considered, the TBA molecules still exhibit a tendency to associate at low concentrations that is somewhat stronger than that indicated by experiments. Finally, we discuss the range and decay times of the long-range correlations, providing an indication of the system size and simulation times that are necessary in order to obtain reliable results for certain properties.
Shprits, Yuri Y.; Kellerman, Adam C.; Drozdov, Alexander Y.; ...
2015-11-19
Our study focused on understanding the coupling between different electron populations in the inner magnetosphere and the various physical processes that determine evolution of electron fluxes at different energies. Observations during the 17 March 2013 storm and simulations with a newly developed Versatile Electron Radiation Belt-4D (VERB-4D) are presented. This analysis of the drift trajectories of the energetic and relativistic electrons shows that electron trajectories at transitional energies with a first invariant on the scale of ~100 MeV/G may resemble ring current or relativistic electron trajectories depending on the level of geomagnetic activity. Simulations with the VERB-4D code including convection,more » radial diffusion, and energy diffusion are presented. Sensitivity simulations including various physical processes show how different acceleration mechanisms contribute to the energization of energetic electrons at transitional energies. In particular, the range of energies where inward transport is strongly influenced by both convection and radial diffusion are studied. Our results of the 4-D simulations are compared to Van Allen Probes observations at a range of energies including source, seed, and core populations of the energetic and relativistic electrons in the inner magnetosphere.« less
First Results of Venus Express Spacecraft Observations with Wettzell
NASA Technical Reports Server (NTRS)
Calves, Guifre Molera; Wagner, Jan; Neidhardt, Alexander; Kronschnabl, Gerhard; Ayucar, Miguel Perez; Cimo, Giuseppe; Pogrebenko, Sergei
2010-01-01
The ESA Venus Express spacecraft was observed at X-band with the Wettzell radio telescope in October-December 2009 in the framework of an assessment study of the possible contribution of the European VLBI Network to the upcoming ESA deep space missions. A major goal of these observations was to develop and test the scheduling, data capture, transfer, processing, and analysis pipeline. Recorded data were transferred from Wettzell to Metsahovi for processing, and the processed data were sent from Mets ahovi to JIVE for analysis. A turnover time of 24 hours from observations to analysis results was achieved. The high dynamic range of the detections allowed us to achieve a milliHz level of spectral resolution accuracy and to extract the phase of the spacecraft signal carrier line. Several physical parameters can be determined from these observational results with more observational data collected. Among other important results, the measured phase fluctuations of the carrier line at different time scales can be used to determine the influence of the solar wind plasma density fluctuations on the accuracy of the astrometric VLBI observations.
NASA Astrophysics Data System (ADS)
Karimabadi, Homa
2012-03-01
Recent advances in simulation technology and hardware are enabling breakthrough science where many longstanding problems can now be addressed for the first time. In this talk, we focus on kinetic simulations of the Earth's magnetosphere and magnetic reconnection process which is the key mechanism that breaks the protective shield of the Earth's dipole field, allowing the solar wind to enter the Earth's magnetosphere. This leads to the so-called space weather where storms on the Sun can affect space-borne and ground-based technological systems on Earth. The talk will consist of three parts: (a) overview of a new multi-scale simulation technique where each computational grid is updated based on its own unique timestep, (b) Presentation of a new approach to data analysis that we refer to as Physics Mining which entails combining data mining and computer vision algorithms with scientific visualization to extract physics from the resulting massive data sets. (c) Presentation of several recent discoveries in studies of space plasmas including the role of vortex formation and resulting turbulence in magnetized plasmas.
Atefi, Seyed Reza; Seoane, Fernando; Kamalian, Shervin; Rosenthal, Eric S.; Lev, Michael H.; Bonmassar, Giorgio
2016-01-01
Purpose: Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis. Methods: Finite element method (FEM) simulations and experimental left–right hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors’ custom-made bioimpedance spectrometer. Mean left–right scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch t-test. Results: The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brain models is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors’ preliminary experimental results also confirmed that the left–right scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05). Conclusions: Realistic
NASA Astrophysics Data System (ADS)
Zhou, Y.; Tao, W.; Hou, A. Y.; Zeng, X.; Shie, C.
2007-12-01
The cloud and precipitation statistics simulated by 3D Goddard Cumulus Ensemble (GCE) model for different environmental conditions, i.e., the South China Sea Monsoon Experiment (SCSMEX), CRYSTAL-FACE, and KAWJEX are compared with Tropical Rainfall Measuring Mission (TRMM) TMI and PR rainfall measurements and as well as cloud observations from the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments. It is found that GCE is capable of simulating major convective system development and reproducing total surface rainfall amount as compared with rainfall estimated from the soundings. The model presents large discrepancies in rain spectrum and vertical hydrometer profiles. The discrepancy in the precipitation field is also consistent with the cloud and radiation observations. The study will focus on the effects of large scale forcing and microphysics to the simulated model- observation discrepancies.
NASA Astrophysics Data System (ADS)
Hayashi, M.; Yoshizumi, M.; Saito, S.; Matsumoto, Y.; Kurita, S.; Teramoto, M.; Hori, T.; Matsuda, S.; Shoji, M.; Machida, S.; Amano, T.; Seki, K.; Higashio, N.; Mitani, T.; Takashima, T.; Kasahara, Y.; Kasaba, Y.; Yagitani, S.; Ishisaka, K.; Tsuchiya, F.; Kumamoto, A.; Matsuoka, A.; Shinohara, I.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.
2017-12-01
Relativistic electron fluxes of the outer radiation belt rapidly change in response to solar wind variations. One of the shortest acceleration processes of electrons in the outer radiation belt is wave-particle interactions between drifting electrons and fast-mode waves induced by compression of the dayside magnetopause caused by interplanetary shocks. In order to investigate this process by a solar wind pressure pulse, we perform a code-coupling simulation using the GEMSIS-RB test particle simulation (Saito et al., 2010) and the GEMSIS-GM global MHD magnetosphere simulation (Matsumoto et al., 2010). As a case study, an interplanetary pressure pulse with the enhancement of 5 nPa is used as the up-stream condition. In the magnetosphere, the fast mode waves with the azimuthal electric field ( negative 𝐸𝜙 : |𝐸&;#120601;| 10 mV/m, azimuthal mode number : m ≤ 2) propagates from the dayside to nightside, interacting with electrons. From the simulation results, we derived effective acceleration model and condition : The electrons whose drift velocities vd ≥ (π/2)Vfast are accelerated efficiently. On December 20, 2016, the Arase (ERG) satellite was launched , allowing more accurate multi-point simultaneous observation with other satellites. We will compare our simulation results with observations from Arase and Van Allen Probes, and investigate the acceleration condition of relativistic electrons associated with storm sudden commencement (SSC).
NASA Technical Reports Server (NTRS)
Emmitt, G. D.; Wood, S. A.; Morris, M.
1990-01-01
Lidar Atmospheric Wind Sounder (LAWS) Simulation Models (LSM) were developed to evaluate the potential impact of global wind observations on the basic understanding of the Earth's atmosphere and on the predictive skills of current forecast models (GCM and regional scale). Fully integrated top to bottom LAWS Simulation Models for global and regional scale simulations were developed. The algorithm development incorporated the effects of aerosols, water vapor, clouds, terrain, and atmospheric turbulence into the models. Other additions include a new satellite orbiter, signal processor, line of sight uncertainty model, new Multi-Paired Algorithm and wind error analysis code. An atmospheric wind field library containing control fields, meteorological fields, phenomena fields, and new European Center for Medium Range Weather Forecasting (ECMWF) data was also added. The LSM was used to address some key LAWS issues and trades such as accuracy and interpretation of LAWS information, data density, signal strength, cloud obscuration, and temporal data resolution.
Li, W.; Ma, Q.; Thorne, R. M.; ...
2016-06-10
Various physical processes are known to cause acceleration, loss, and transport of energetic electrons in the Earth's radiation belts, but their quantitative roles in different time and space need further investigation. During the largest storm over the past decade (17 March 2015), relativistic electrons experienced fairly rapid acceleration up to ~7 MeV within 2 days after an initial substantial dropout, as observed by Van Allen Probes. In the present paper, we evaluate the relative roles of various physical processes during the recovery phase of this large storm using a 3-D diffusion simulation. By quantitatively comparing the observed and simulated electronmore » evolution, we found that chorus plays a critical role in accelerating electrons up to several MeV near the developing peak location and produces characteristic flat-top pitch angle distributions. By only including radial diffusion, the simulation underestimates the observed electron acceleration, while radial diffusion plays an important role in redistributing electrons and potentially accelerates them to even higher energies. Moreover, plasmaspheric hiss is found to provide efficient pitch angle scattering losses for hundreds of keV electrons, while its scattering effect on > 1 MeV electrons is relatively slow. Although an additional loss process is required to fully explain the overestimated electron fluxes at multi-MeV, the combined physical processes of radial diffusion and pitch angle and energy diffusion by chorus and hiss reproduce the observed electron dynamics remarkably well, suggesting that quasi-linear diffusion theory is reasonable to evaluate radiation belt electron dynamics during this big storm.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, W.; Ma, Q.; Thorne, R. M.
Various physical processes are known to cause acceleration, loss, and transport of energetic electrons in the Earth's radiation belts, but their quantitative roles in different time and space need further investigation. During the largest storm over the past decade (17 March 2015), relativistic electrons experienced fairly rapid acceleration up to ~7 MeV within 2 days after an initial substantial dropout, as observed by Van Allen Probes. In the present paper, we evaluate the relative roles of various physical processes during the recovery phase of this large storm using a 3-D diffusion simulation. By quantitatively comparing the observed and simulated electronmore » evolution, we found that chorus plays a critical role in accelerating electrons up to several MeV near the developing peak location and produces characteristic flat-top pitch angle distributions. By only including radial diffusion, the simulation underestimates the observed electron acceleration, while radial diffusion plays an important role in redistributing electrons and potentially accelerates them to even higher energies. Moreover, plasmaspheric hiss is found to provide efficient pitch angle scattering losses for hundreds of keV electrons, while its scattering effect on > 1 MeV electrons is relatively slow. Although an additional loss process is required to fully explain the overestimated electron fluxes at multi-MeV, the combined physical processes of radial diffusion and pitch angle and energy diffusion by chorus and hiss reproduce the observed electron dynamics remarkably well, suggesting that quasi-linear diffusion theory is reasonable to evaluate radiation belt electron dynamics during this big storm.« less
NASA Astrophysics Data System (ADS)
Lei, Hongxing; Wu, Chun; Wang, Zhi-Xiang; Zhou, Yaoqi; Duan, Yong
2008-06-01
Reaching the native states of small proteins, a necessary step towards a comprehensive understanding of the folding mechanisms, has remained a tremendous challenge to ab initio protein folding simulations despite the extensive effort. In this work, the folding process of the B domain of protein A (BdpA) has been simulated by both conventional and replica exchange molecular dynamics using AMBER FF03 all-atom force field. Started from an extended chain, a total of 40 conventional (each to 1.0 μs) and two sets of replica exchange (each to 200.0 ns per replica) molecular dynamics simulations were performed with different generalized-Born solvation models and temperature control schemes. The improvements in both the force field and solvent model allowed successful simulations of the folding process to the native state as demonstrated by the 0.80 A˚ Cα root mean square deviation (RMSD) of the best folded structure. The most populated conformation was the native folded structure with a high population. This was a significant improvement over the 2.8 A˚ Cα RMSD of the best nativelike structures from previous ab initio folding studies on BdpA. To the best of our knowledge, our results demonstrate, for the first time, that ab initio simulations can reach the native state of BdpA. Consistent with experimental observations, including Φ-value analyses, formation of helix II/III hairpin was a crucial step that provides a template upon which helix I could form and the folding process could complete. Early formation of helix III was observed which is consistent with the experimental results of higher residual helical content of isolated helix III among the three helices. The calculated temperature-dependent profile and the melting temperature were in close agreement with the experimental results. The simulations further revealed that phenylalanine 31 may play critical to achieve the correct packing of the three helices which is consistent with the experimental observation
Observations and simulations of specularly reflected He++ at Earth's quasiperpendicular bow shock
NASA Astrophysics Data System (ADS)
Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Anderson, B. J.; Burch, J. L.; Giles, B. L.
2016-12-01
Specular reflection of protons at Earth's quasiperpendicular bow shock is an important process for supercritical shock dissipation. Previous studies have found evidence of He++ specular reflection from reduced particle distributions downstream from the shock, but confirmation of the process for heavier ions in the shock foot was not possible due to time resolution constraints. We present He++ distributions, observed by MMS in a quasiperpendicular bow shock crossing, that are consistent with specularly reflected He++. We also investigate the He++ dynamics with test-particle simulations in a simulated shock based on this crossing and we conduct wave analysis to determine what processes lead to separate gyrotropization timescales for the transmitted and reflected populations.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Moestl, U. V.; Temmer, M.; Veronig, A. M., E-mail: ute.moestl@uni-graz.at
2013-03-20
The Atmospheric Imaging Assembly on board the Solar Dynamics Observatory observed a coronal mass ejection with an embedded filament on 2011 February 24, revealing quasi-periodic vortex-like structures at the northern side of the filament boundary with a wavelength of approximately 14.4 Mm and a propagation speed of about 310 {+-} 20 km s{sup -1}. These structures could result from the Kelvin-Helmholtz instability occurring on the boundary. We perform 2.5D numerical simulations of the Kelvin-Helmholtz instability and compare the simulated characteristic properties of the instability with the observations, where we obtain qualitative as well as quantitative accordance. We study the absencemore » of Kelvin-Helmholtz vortex-like structures on the southern side of the filament boundary and find that a magnetic field component parallel to the boundary with a strength of about 20% of the total magnetic field has stabilizing effects resulting in an asymmetric development of the instability.« less
Comparing Simulated and Observed Spectroscopic Signatures of Mix in Omega Capsules
NASA Astrophysics Data System (ADS)
Tregillis, I. L.; Shah, R. C.; Hakel, P.; Cobble, J. A.; Murphy, T. J.; Krasheninnikova, N. S.; Hsu, S. C.; Bradley, P. A.; Schmitt, M. J.; Batha, S. H.; Mancini, R. C.
2012-10-01
The Defect-Induced Mix Experiment (DIME) campaign at Los Alamos National Laboratory uses multi-monochromatic X-ray imaging (MMI)footnotetextT. Nagayama, R.C. Mancini, R. Florido, et al, J. App. Phys. 109, 093303 (2011) to detect the migration of high-Z spectroscopic dopants into the hot core of an imploded capsule. We have developed an MMI post-processing tool for producing synthetic datasets from two- and three-dimensional Lagrangian numerical simulations of Omega and NIF shots. These synthetic datasets are of sufficient quality, and contain sufficient physics, that they can be analyzed in the same manner as actual MMI data. We have carried out an extensive comparison between simulated and observed MMI data for a series of polar direct-drive shots carried out at the Omega laser facility in January, 2011. The capsule diameter was 870 microns; the 15 micron CH ablators contained a 2 micron Ti-doped layer along the inner edge. All capsules were driven with 17 kJ; some capsules were manufactured with an equatorial ``trench'' defect. This talk will focus on the construction of spectroscopic-quality synthetic MMI datasets from numerical simulations, and their correlation with MMI measurements.
Evaluation of GFDL-AM4 simulations of nitrogen oxides with OMI satellite observations
NASA Astrophysics Data System (ADS)
Penn, E.; Horowitz, L. W.; Naik, V.
2017-12-01
We examine the seasonal cycle and interannual variability of NO2 from 2005-2015 of NO2 over key global regions using simulations with a nudged version of the GFDL-AM4 chemistry-climate model and satellite-based observations from OMI (Ozone Monitoring Instrument), which observes near-global NO2 column abundances at 1pm local time daily. We gridded TEMIS (Tropospheric Emissions Monitoring Internet Service) OMI data to the model spatial grid using WHIPS 2.0 (Wisconsin Horizontal Interpolation Program for Satellites version 2.0) and applied the OMI averaging kernel to weight the model's NO2 concentrations vertically. Model-simulated tropospheric NO2 columns reproduce well the OMI spatial patterns (averaging r2=0.81) and seasonal cycles, but underestimate observations in most regions by 16-62%. A notable exception is the overestimate by 5-35% in East Asia. In regions dominated by biomass burning, these emissions tend to control the seasonal cycle of NO2. However, where anthropogenic emissions dominate, the photochemical conversion of NO2 to PAN and nitric acid controls the seasonal cycle, as indicated by NO2/NOy ratios. Future work is required to explain AM4 biases relative to OMI.
Review on optical constants of Titan aerosols: Experimental results and modeling/observational data
NASA Astrophysics Data System (ADS)
Brassé, Coralie; Muñoz, Olga; Coll, Patrice; Raulin, François
2014-05-01
available. Therefore it would be very useful to get more laboratory data and especially from Tran et al (2013), Mahjoub et al. (2012) and Imanaka et al. (2012) samples in these spectral regions since their refractive indexes match observational and theoretical data in other spectral ranges. This presentation will critically summarize these recent results and present detailled constraints on the optical constants Titan's aerosols. In addition, specific lacks of data will be highlighted as well as some possible investigations to be carried out to fill these gaps. References: Cable, M. L., et al., 2012. Titan Tholins: Simulating Titan Organic Chemistry in the Cassini-Huygens Era. Chemical Reviews. 112, 1882-1909. Imanaka, H., et al., 2012. Optical constants of Titan tholins at mid-infrared wavelengths (2.5-25 µm) and the possible chemical nature of Titan's haze particles. Icarus. 218, 247-261. Khare, B. N., et al., 1984. Optical-Constants of Organic Tholins Produced in a Simulated Titanian Atmosphere - from Soft-X-Ray to Microwave-Frequencies. Icarus. 60, 127-137. Kim, S. J., Courtin, R., 2013. Spectral characteristics of the Titanian haze at 1-5 micron from Cassini/VIMS solar occultation data. Astronomy & Astrophysics. 557, L6. Mahjoub, A., et al., 2012. Influence of methane concentration on the optical indices of Titan's aerosols analogues. Icarus. 221, 670-677. Raulin, F., et al., 2012. Prebiotic-like chemistry on Titan. Chemical Society Reviews. 41, 5380-5393. Sagan, C., Khare, B. N., 1979. Tholins - Organic-Chemistry of Inter-Stellar Grains and Gas. Nature. 277, 102-107. Tran, B. N., et al., 2003. Simulation of Titan haze formation using a photochemical flow reactor - The optical constants of the polymer. Icarus. 165, 379-390. Acknowledgements: We acknowledge support from the French Space Agency (CNES) and the European Space Agency (ESA).
NASA Astrophysics Data System (ADS)
Endo, S.; Fridlind, A. M.; Lin, W.; Vogelmann, A. M.; Toto, T.; Liu, Y.
2013-12-01
Three cases of boundary layer clouds are analyzed in the FAst-physics System TEstbed and Research (FASTER) project, based on continental boundary-layer-cloud observations during the RACORO Campaign [Routine Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations] at the ARM Climate Research Facility's Southern Great Plains (SGP) site. The three 60-hour case study periods are selected to capture the temporal evolution of cumulus, stratiform, and drizzling boundary-layer cloud systems under a range of conditions, intentionally including those that are relatively more mixed or transitional in nature versus being of a purely canonical type. Multi-modal and temporally varying aerosol number size distribution profiles are derived from aircraft observations. Large eddy simulations (LESs) are performed for the three case study periods using the GISS Distributed Hydrodynamic Aerosol and Radiative Modeling Application (DHARMA) model and the WRF-FASTER model, which is the Weather Research and Forecasting (WRF) model implemented with forcing ingestion and other functions to constitute a flexible LES. The two LES models commonly capture the significant transitions of cloud-topped boundary layers in the three periods: diurnal evolution of cumulus layers repeating over multiple days, nighttime evolution/daytime diminution of thick stratus, and daytime breakup of stratus and stratocumulus clouds. Simulated transitions of thermodynamic structures of the cloud-topped boundary layers are examined by balloon-borne soundings and ground-based remote sensors. Aircraft observations are then used to statistically evaluate the predicted cloud droplet number size distributions under varying aerosol and cloud conditions. An ensemble approach is used to refine the model configuration for the combined use of observations with parallel LES and single-column model simulations. See Lin et al. poster for single
Observed and simulated sea breeze characteristics over Rayong coastal area, Thailand
NASA Astrophysics Data System (ADS)
Phan, Tung Thanh; Manomaiphiboon, Kasemsan
2012-05-01
This work presents the detailed characterization of sea breeze (SB) over the Rayong coastal area, one of the most rapidly developed and highly industrialized areas during the last decade in Thailand, using observation data analysis and fine-resolution (2 km) mesoscale meteorological modeling with incorporation of new land cover and satellite-derived vegetation fraction data sets. The key characteristics considered include frequency of SB occurrence, sea-breeze day (SBD) identification, degree of inland penetration, and boundary layer development. It was found that SBs occur frequently in the winter due mainly to relatively large land-sea temperature contrasts and minimally in the wet season. Monthly mean SB onset and cessation times are at around 12-15 local time (LT) and 18-21 LT, respectively, and its strength peaks during the early- to mid-afternoon. Monthly SB hodographs generally exhibit clockwise rotations, and SB inland penetration (at PCD-T tower) ranges widely with the monthly means of 25-55 km from the coast. Mesoscale MM5 modeling was performed on two selected SBDs (13 January and 16 March 2006), on which the SBs are under weak and onshore strong influences from background winds, respectively. Simulated near-surface winds and temperature were found to be in fair-to-acceptable agreement with the observations. The SB circulation along the Rayong coast is clearly defined with a return flow aloft and a front on 13 January, while it is enhanced by the onshore background winds on 16 March. Another SB along the Chonburi coast also develops separately, but their fronts merge into one in the mid-afternoon, resulting in large area coverage by the SB. Simulated planetary boundary layer height over the land area is significantly affected by a thermal internal boundary layer (TIBL) induced by an SB, which is found to be low near the coast and increases toward the front (up to 800-1,000 m along the Rayong coast).
Mars Science Laboratory relative humidity observations: Initial results.
Harri, A-M; Genzer, M; Kemppinen, O; Gomez-Elvira, J; Haberle, R; Polkko, J; Savijärvi, H; Rennó, N; Rodriguez-Manfredi, J A; Schmidt, W; Richardson, M; Siili, T; Paton, M; Torre-Juarez, M De La; Mäkinen, T; Newman, C; Rafkin, S; Mischna, M; Merikallio, S; Haukka, H; Martin-Torres, J; Komu, M; Zorzano, M-P; Peinado, V; Vazquez, L; Urqui, R
2014-09-01
The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers. Atmospheric water mixing ratio at Gale crater varies from 30 to 140 ppmMSL relative humidity observation provides good dataHighest detected relative humidity reading during first MSL 100 sols is RH75.
Comparison of preliminary results from Airborne Aster Simulator (AAS) with TIMS data
NASA Technical Reports Server (NTRS)
Kannari, Yoshiaki; Mills, Franklin; Watanabe, Hiroshi; Ezaka, Teruya; Narita, Tatsuhiko; Chang, Sheng-Huei
1992-01-01
The Japanese Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER), being developed for a NASA EOS-A satellite, will have 3 VNIR, 6 SWIR, and 5 TIR (8-12 micron) bands. An Airborne ASTER Simulator (AAS) was developed for Japan Resources Observation System Organization (JAROS) by the Geophysical Environmental Research Group (GER) Corp. to research surface temperature and emission features in the MWIR/TIR, to simulate ASTER's TIR bands, and to study further possibility of MWIR/TIR bands. ASTER Simulator has 1 VNIR, 3 MWIR (3-5 microns), and 20 (currently 24) TIR bands. Data was collected over 3 sites - Cuprite, Nevada; Long Valley/Mono Lake, California; and Death Valley, California - with simultaneous ground truth measurements. Preliminary data collected by AAS for Cuprite, Nevada is presented and AAS data is compared with Thermal Infrared Multispectral Scanner (TIMS) data.
Earth resources mission performance studies. Volume 2: Simulation results
NASA Technical Reports Server (NTRS)
1974-01-01
Simulations were made at three month intervals to investigate the EOS mission performance over the four seasons of the year. The basic objectives of the study were: (1) to evaluate the ability of an EOS type system to meet a representative set of specific collection requirements, and (2) to understand the capabilities and limitations of the EOS that influence the system's ability to satisfy certain collection objectives. Although the results were obtained from a consideration of a two sensor EOS system, the analysis can be applied to any remote sensing system having similar optical and operational characteristics. While the category related results are applicable only to the specified requirement configuration, the results relating to general capability and limitations of the sensors can be applied in extrapolating to other U.S. based EOS collection requirements. The TRW general purpose mission simulator and analytic techniques discussed in this report can be applied to a wide range of collection and planning problems of earth orbiting imaging systems.
NASA Astrophysics Data System (ADS)
D'Alessandro, John J.; Diao, Minghui; Wu, Chenglai; Liu, Xiaohong; Chen, Ming; Morrison, Hugh; Eidhammer, Trude; Jensen, Jorgen B.; Bansemer, Aaron; Zondlo, Mark A.; DiGangi, Josh P.
2017-03-01
Occurrence frequency and dynamical conditions of ice supersaturation (ISS, where relative humidity with respect to ice (RHi) > 100%) are examined in the upper troposphere around convective activity. Comparisons are conducted between in situ airborne observations and the Weather Research and Forecasting model simulations using four double-moment microphysical schemes at temperatures ≤ -40°C. All four schemes capture both clear-sky and in-cloud ISS conditions. However, the clear-sky (in-cloud) ISS conditions are completely (significantly) limited to the RHi thresholds of the Cooper parameterization. In all of the simulations, ISS occurrence frequencies are higher by 3-4 orders of magnitude at higher updraft speeds (>1 m s-1) than those at the lower updraft speeds when ice water content (IWC) > 0.01 g m-3, while observations show smaller differences up to 1-2 orders of magnitude. The simulated ISS also occurs less frequently at weaker updrafts and downdrafts than observed. These results indicate that the simulations have a greater dependence on stronger updrafts to maintain/generate ISS at higher IWC. At lower IWC (≤0.01 g m-3), simulations unexpectedly show lower ISS frequencies at stronger updrafts. Overall, the Thompson aerosol-aware scheme has the closest magnitudes and frequencies of ISS >20% to the observations, and the modified Morrison has the closest correlations between ISS frequencies and vertical velocity at higher IWC and number density. The Cooper parameterization often generates excessive ice crystals and therefore suppresses the frequency and magnitude of ISS, indicating that it should be initiated at higher ISS (e.g., ≥25%).
NASA Astrophysics Data System (ADS)
Rubini, F.; Maurri, L.; Inghirami, G.; Bacciotti, F.; Del Zanna, L.
2014-07-01
High angular resolution spectra obtained with the Hubble Space Telescope Imaging Spectrograph (HST/STIS) provide rich morphological and kinematical information about the stellar jet phenomenon, which allows us to test theoretical models efficiently. In this work, numerical simulations of stellar jets in the propagation region are executed with the PLUTO code, by adopting inflow conditions that arise from former numerical simulations of magnetized outflows, accelerated by the disk-wind mechanism in the launching region. By matching the two regions, information about the magneto-centrifugal accelerating mechanism underlying a given astrophysical object can be extrapolated by comparing synthetic and observed position-velocity diagrams. We show that quite different jets, like those from the young T Tauri stars DG-Tau and RW-Aur, may originate from the same disk-wind model for different configurations of the magnetic field at the disk surface. This result supports the idea that all the observed jets may be generated by the same mechanism. Appendix A is available in electronic form at http://www.aanda.org
Preliminary Results from an Assimilation of TOMS Aerosol Observations Into the GOCART Model
NASA Technical Reports Server (NTRS)
daSilva, Arlindo; Weaver, Clark J.; Ginoux, Paul; Torres, Omar; Einaudi, Franco (Technical Monitor)
2000-01-01
At NASA Goddard we are developing a global aerosol data assimilation system that combines advances in remote sensing and modeling of atmospheric aerosols. The goal is to provide high resolution, 3-D aerosol distributions to the research community. Our first step is to develop a simple assimilation system for Saharan mineral aerosol. The Goddard Chemistry and Aerosol Radiation model (GOCART) provides accurate 3-D mineral aerosol size distributions that compare well with TOMS satellite observations. Surface, mobilization, wet and dry deposition, convective and long-range transport are all driven by assimilated fields from the Goddard Earth Observing System Data Assimilation System, GEOS-DAS. Our version of GOCART transports sizes from.08-10 microns and only simulates Saharan dust. TOMS radiance observations in the ultra violet provide information on the mineral and carbonaceous aerosol fields. We use two main observables in this study: the TOMS aerosol index (AI) which is directly related to the ratio of the 340 and 380 radiances and the 380 radiance. These are sensitive to the aerosol optical thickness, the single scattering albedo and the height of the aerosol layer. The Goddard Aerosol Assimilation System (GAAS) uses the Data Assimilation Office's Physical-space Statistical Analysis System (PSAS) to combine TOMS observations and GOCART model first guess fields. At this initial phase we only assimilate observations into the the GOCART model over regions of Africa and the Atlantic where mineral aerosols dominant and carbonaceous aerosols are minimal, Our preliminary results during summer show that the assimilation with TOMS data modifies both the aerosol mass loading and the single scattering albedo. Assimilated aerosol fields will be compared with assimilated aerosol fields from GOCART and AERONET observations over Cape Verde.
A method for data handling numerical results in parallel OpenFOAM simulations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Anton, Alin; Muntean, Sebastian
Parallel computational fluid dynamics simulations produce vast amount of numerical result data. This paper introduces a method for reducing the size of the data by replaying the interprocessor traffic. The results are recovered only in certain regions of interest configured by the user. A known test case is used for several mesh partitioning scenarios using the OpenFOAM toolkit{sup ®}[1]. The space savings obtained with classic algorithms remain constant for more than 60 Gb of floating point data. Our method is most efficient on large simulation meshes and is much better suited for compressing large scale simulation results than the regular algorithms.
Migrating Shoals on Ebb-tidal Deltas: Results from Numerical Simulations
NASA Astrophysics Data System (ADS)
van der Vegt, M.; Ridderinkhof, W.; De Swart, H. E.; Hoekstra, P.
2016-02-01
Many ebb-tidal deltas show repetitive patterns of channel- shoal generation, migration and attachment of shoals to the downdrift barrier coast. For the Wadden Sea coast along the Dutch, German en Danish coastline the typical time scale of shoal attachment ranges from several to hundred years. There is a weak correlation between the tidal prism and the typical time scale of shoal attachment. The main aim of this research is to clarify the physical processes that result in the formation of shoals on ebb-tidal deltas and to study what determines their propagation speed. To this end numerical simulations were performed in Delft3D. Starting from an idealized geometry with a sloping bed on the shelf sea and a flat bed in the back barrier basin, the model was spun up until an approximate morphodynamic steady state was realized. The model was forced with tides and constant wave forcing based on the yearly average conditions along the Dutch Wadden coast. The resulting ebb-tidal delta is called the equilibrium delta. Next, two types of scenarios were run. First, the equilibrium delta was breached by creating a channel and adding the removed sand volume to the downdrift shoal. Second, the wave climate was made more realistic by adding storms and subsequently its effect on the equilibrium delta was simulated. Based on the model results we conclude the following. First, the model is able to realistically simulate the migration of shoals and the attachment to the downdrift barrier island. Second, larger waves result in faster propagation of the shoals. Third, simulations suggest that shoals only migrate when they are shallower than a critical maximum depth with respect to the wave height. These shallow shoals can be `man-made' or be generated during storms. When no storms were added to the wave climate and the bed was not artificially disturbed, no migrating shoals were simulated. During the presentation the underlying physical processes will be discussed in detail.
COCOA code for creating mock observations of star cluster models
NASA Astrophysics Data System (ADS)
Askar, Abbas; Giersz, Mirek; Pych, Wojciech; Dalessandro, Emanuele
2018-04-01
We introduce and present results from the COCOA (Cluster simulatiOn Comparison with ObservAtions) code that has been developed to create idealized mock photometric observations using results from numerical simulations of star cluster evolution. COCOA is able to present the output of realistic numerical simulations of star clusters carried out using Monte Carlo or N-body codes in a way that is useful for direct comparison with photometric observations. In this paper, we describe the COCOA code and demonstrate its different applications by utilizing globular cluster (GC) models simulated with the MOCCA (MOnte Carlo Cluster simulAtor) code. COCOA is used to synthetically observe these different GC models with optical telescopes, perform point spread function photometry, and subsequently produce observed colour-magnitude diagrams. We also use COCOA to compare the results from synthetic observations of a cluster model that has the same age and metallicity as the Galactic GC NGC 2808 with observations of the same cluster carried out with a 2.2 m optical telescope. We find that COCOA can effectively simulate realistic observations and recover photometric data. COCOA has numerous scientific applications that maybe be helpful for both theoreticians and observers that work on star clusters. Plans for further improving and developing the code are also discussed in this paper.
ERIC Educational Resources Information Center
Pustejovsky, James E.; Runyon, Christopher
2014-01-01
Direct observation recording procedures produce reductive summary measurements of an underlying stream of behavior. Previous methodological studies of these recording procedures have employed simulation methods for generating random behavior streams, many of which amount to special cases of a statistical model known as the alternating renewal…
Information and Complexity Measures Applied to Observed and Simulated Soil Moisture Time Series
USDA-ARS?s Scientific Manuscript database
Time series of soil moisture-related parameters provides important insights in functioning of soil water systems. Analysis of patterns within these time series has been used in several studies. The objective of this work was to compare patterns in observed and simulated soil moisture contents to u...
Kim, Tae K.; Pogorelov, Nikolai V.; Borovikov, Sergey N.; ...
2012-11-20
Numerical modeling of the heliosphere is a critical component of space weather forecasting. The accuracy of heliospheric models can be improved by using realistic boundary conditions and confirming the results with in situ spacecraft measurements. To accurately reproduce the solar wind (SW) plasma flow near Earth, we need realistic, time-dependent boundary conditions at a fixed distance from the Sun. We may prepare such boundary conditions using SW speed and density determined from interplanetary scintillation (IPS) observations, magnetic field derived from photospheric magnetograms, and temperature estimated from its correlation with SW speed. In conclusion, we present here the time-dependent MHD simulationmore » results obtained by using the 2011 IPS data from the Solar-Terrestrial Environment Laboratory as time-varying inner boundary conditions and compare the simulated data at Earth with OMNI data (spacecraft-interspersed, near-Earth solar wind data).« less
Computer simulating observations of the Lunar physical libration for the Japanese Lunar project ILOM
NASA Astrophysics Data System (ADS)
Petrova, Natalia; Hanada, Hideo
2010-05-01
are calculated using the analytical theory of physical libration Petrova et al. (2008; 2009). We cannot use Newton's method for solution of the equation, because the Jacobian | | || δδfx11 δδfx12 δδf1x3-|| || δδfx2 δδfx2 δδf2x-|| J(X ) = || δf13 δf23 δ3f3-|| = 0. || δx1 δx2 δx3 || We transformed equations to the iteration form xi = φi(X). Used iteration methods have unsatisfactory convergence: inaccuracy in polar distance of 1 milliseconds of arc causes inaccuracy of 0.01arcsec in ρ and in Iσ, and 0.1 arcsec in ?. Results of our computer simulating showed It's necessary to carry out measuring of polar distances of stars in several meridians simultaneously to increase sample of stars. It's necessary to find additional links (relations) between observed parameters and libration angles to have stable mathematical methods to receive solutions for lunar rotation with high accuracy. The research was supported by the Russian-Japanese grant RFFI-JSPS 09-02-92113, (2009-2010) References: Hanada H., Noda H., Kikuchi F. et al., 2009. Different kind of observations of lunar rotation and gravity for SELENE-2. Proc of conf. Astrokazan-2009, August 19 - 26, Kazan, Russia. p. 172-175 Petrova N., Gusev A., Kawano N., Hanada H., 2008. Free librations of the two-layer Moon and the possibilities of their detection. Advances in Space Res., v 42, p. 1398-1404 Petrova N., Gusev A., Hanada H., Ivanova T., Akutina V., 2009. Application of the analytical theory of Lunar physical libration for simulating observations of stars for the future Japanese project ILOM. Proc of conf. Astrokazan-2009, August 19 - 26, Kazan, Russia. p.197 - 201.
An analysis of simulated and observed storm characteristics
NASA Astrophysics Data System (ADS)
Benestad, R. E.
2010-09-01
A calculus-based cyclone identification (CCI) method has been applied to the most recent re-analysis (ERAINT) from the European Centre for Medium-range Weather Forecasts and results from regional climate model (RCM) simulations. The storm frequency for events with central pressure below a threshold value of 960-990hPa were examined, and the gradient wind from the simulated storm systems were compared with corresponding estimates from the re-analysis. The analysis also yielded estimates for the spatial extent of the storm systems, which was also included in the regional climate model cyclone evaluation. A comparison is presented between a number of RCMs and the ERAINT re-analysis in terms of their description of the gradient winds, number of cyclones, and spatial extent. Furthermore, a comparison between geostrophic wind estimated though triangules of interpolated or station measurements of SLP is presented. Wind still represents one of the more challenging variables to model realistically.
NASA Astrophysics Data System (ADS)
Ahmadi, N.; Wilder, F. D.; Usanova, M.; Ergun, R.; Argall, M. R.; Goodrich, K.; Eriksson, S.; Germaschewski, K.; Torbert, R. B.; Lindqvist, P. A.; Le Contel, O.; Khotyaintsev, Y. V.; Strangeway, R. J.; Schwartz, S. J.; Giles, B. L.; Burch, J.
2017-12-01
The Magnetospheric Multiscale (MMS) mission observed electron whistler waves at the center and at the gradients of magnetic holes on the dayside magnetosheath. The magnetic holes are nonlinear mirror structures which are anti-correlated with particle density. We used expanding box Particle-in-cell simulations and produced the mirror instability magnetic holes. We show that the electron whistler waves can be generated at the gradients and the center of magnetic holes in our simulations which is in agreement with MMS observations. At the nonlinear regime of mirror instability, the proton and electron temperature anisotropy are anti-correlated with the magnetic hole. The plasma is unstable to electron whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are dominant, electron temperature anisotropy develops at the edges of the magnetic holes and electrons become isotropic at the magnetic field minimum. We investigate the possible mechanism for enhancing the electron temperature anisotropy and analyze the electron pitch angle distributions and electron distribution functions in our simulations and compare it with MMS observations.
Electron-cloud updated simulation results for the PSR, and recent results for the SNS
NASA Astrophysics Data System (ADS)
Pivi, M.; Furman, M. A.
2002-05-01
Recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos are presented in this paper. A refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has recently been included in the electron-cloud code.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Morrison, H.; Zuidema, Paquita; Ackerman, Andrew
2011-06-16
An intercomparison of six cloud-resolving and large-eddy simulation models is presented. This case study is based on observations of a persistent mixed-phase boundary layer cloud gathered on 7 May, 1998 from the Surface Heat Budget of Arctic Ocean (SHEBA) and First ISCCP Regional Experiment - Arctic Cloud Experiment (FIRE-ACE). Ice nucleation is constrained in the simulations in a way that holds the ice crystal concentration approximately fixed, with two sets of sensitivity runs in addition to the baseline simulations utilizing different specified ice nucleus (IN) concentrations. All of the baseline and sensitivity simulations group into two distinct quasi-steady states associatedmore » with either persistent mixed-phase clouds or all-ice clouds after the first few hours of integration, implying the existence of multiple equilibria. These two states are associated with distinctly different microphysical, thermodynamic, and radiative characteristics. Most but not all of the models produce a persistent mixed-phase cloud qualitatively similar to observations using the baseline IN/crystal concentration, while small increases in the IN/crystal concentration generally lead to rapid glaciation and conversion to the all-ice state. Budget analysis indicates that larger ice deposition rates associated with increased IN/crystal concentrations have a limited direct impact on dissipation of liquid in these simulations. However, the impact of increased ice deposition is greatly enhanced by several interaction pathways that lead to an increased surface precipitation flux, weaker cloud top radiative cooling and cloud dynamics, and reduced vertical mixing, promoting rapid glaciation of the mixed-phase cloud for deposition rates in the cloud layer greater than about 1-2x10-5 g kg-1 s-1. These results indicate the critical importance of precipitation-radiative-dynamical interactions in simulating cloud phase, which have been neglected in previous fixed-dynamical parcel studies of
NASA Technical Reports Server (NTRS)
Conroy, Michael; Mazzone, Rebecca; Little, William; Elfrey, Priscilla; Mann, David; Mabie, Kevin; Cuddy, Thomas; Loundermon, Mario; Spiker, Stephen; McArthur, Frank;
2010-01-01
The Distributed Observer network (DON) is a NASA-collaborative environment that leverages game technology to bring three-dimensional simulations to conventional desktop and laptop computers in order to allow teams of engineers working on design and operations, either individually or in groups, to view and collaborate on 3D representations of data generated by authoritative tools such as Delmia Envision, Pro/Engineer, or Maya. The DON takes models and telemetry from these sources and, using commercial game engine technology, displays the simulation results in a 3D visual environment. DON has been designed to enhance accessibility and user ability to observe and analyze visual simulations in real time. A variety of NASA mission segment simulations [Synergistic Engineering Environment (SEE) data, NASA Enterprise Visualization Analysis (NEVA) ground processing simulations, the DSS simulation for lunar operations, and the Johnson Space Center (JSC) TRICK tool for guidance, navigation, and control analysis] were experimented with. Desired functionalities, [i.e. Tivo-like functions, the capability to communicate textually or via Voice-over-Internet Protocol (VoIP) among team members, and the ability to write and save notes to be accessed later] were targeted. The resulting DON application was slated for early 2008 release to support simulation use for the Constellation Program and its teams. Those using the DON connect through a client that runs on their PC or Mac. This enables them to observe and analyze the simulation data as their schedule allows, and to review it as frequently as desired. DON team members can move freely within the virtual world. Preset camera points can be established, enabling team members to jump to specific views. This improves opportunities for shared analysis of options, design reviews, tests, operations, training, and evaluations, and improves prospects for verification of requirements, issues, and approaches among dispersed teams.
ERIC Educational Resources Information Center
Dart, Evan H.; Radley, Keith C.; Briesch, Amy M.; Furlow, Christopher M.; Cavell, Hannah J.; Briesch, Amy M.
2016-01-01
Two studies investigated the accuracy of eight different interval-based group observation methods that are commonly used to assess the effects of classwide interventions. In Study 1, a Microsoft Visual Basic program was created to simulate a large set of observational data. Binary data were randomly generated at the student level to represent…
NASA Astrophysics Data System (ADS)
Bertone, Stefano; Vecchiato, Alberto; Bucciarelli, Beatrice; Crosta, Mariateresa; Lattanzi, Mario G.; Bianchi, Luca; Angonin, Marie-Christine; Le Poncin-Lafitte, Christophe
2017-12-01
Context. A key objective of the ESA Gaia satellite is the realization of a quasi-inertial reference frame at visual wavelengths by means of global astrometric techniques. This requires accurate mathematical and numerical modeling of relativistic light propagation, as well as double-blind-like procedures for the internal validation of the results, before they are released to the scientific community at large. Aims: We aim to specialize the time transfer functions (TTF) formalism to the case of the Gaia observer and prove its applicability to the task of global sphere reconstruction (GSR), in anticipation of its inclusion in the GSR system, already featuring the Relativistic Astrometric MODel (RAMOD) suite, as an additional semi-external validation of the forthcoming Gaia baseline astrometric solutions. Methods: We extended the current GSR framework and software infrastructure (GSR2) to include TTF relativistic observation equations compatible with Gaia's operations. We used simulated data generated by the Gaia Data Processing and Analysis Consortium (DPAC) to obtain different least-squares estimations of the full (five-parameter) stellar spheres and gauge results. These were compared to analogous solutions obtained with the current RAMOD model in GSR2 (RAMOD@GSR2) and to the catalog generated with the Gaia RElativistic Model (GREM), the model baselined for Gaia and used to generate the DPAC synthetic data. Results: Linearized least-squares TTF solutions are based on spheres of about 132 000 primary stars uniformly distributed on the sky and simulated observations spanning the entire 5 yr range of Gaia's nominal operational lifetime. The statistical properties of the results compare well with those of GREM. Finally, comparisons to RAMOD@GSR2 solutions confirmed the known lower accuracy of that model and allowed us to establish firm limits on the quality of the linearization point outside of which an iteration for non-linearity is required for its proper convergence
Wang, Candice; Huang, Chin-Chou; Lin, Shing-Jong; Chen, Jaw-Wen
2016-01-01
Objectives The goal of our study was to shed light on educational methods to strengthen medical students' cardiopulmonary resuscitation (CPR) leadership and team skills in order to optimise CPR understanding and success using didactic videos and high-fidelity simulations. Design An observational study. Setting A tertiary medical centre in Northern Taiwan. Participants A total of 104 5–7th year medical students, including 72 men and 32 women. Interventions We provided the medical students with a 2-hour training session on advanced CPR. During each class, we divided the students into 1–2 groups; each group consisted of 4–6 team members. Medical student teams were trained by using either method A or B. Method A started with an instructional CPR video followed by a first CPR simulation. Method B started with a first CPR simulation followed by an instructional CPR video. All students then participated in a second CPR simulation. Outcome measures Student teams were assessed with checklist rating scores in leadership, teamwork and team member skills, global rating scores by an attending physician and video-recording evaluation by 2 independent individuals. Results The 104 medical students were divided into 22 teams. We trained 11 teams using method A and 11 using method B. Total second CPR simulation scores were significantly higher than first CPR simulation scores in leadership (p<0.001), teamwork (p<0.001) and team member skills (p<0.001). For methods A and B students' first CPR simulation scores were similar, but method A students' second CPR simulation scores were significantly higher than those of method B in leadership skills (p=0.034), specifically in the support subcategory (p=0.049). Conclusions Although both teaching strategies improved leadership, teamwork and team member performance, video exposure followed by CPR simulation further increased students' leadership skills compared with CPR simulation followed by video exposure. PMID:27678539
Mars Science Laboratory relative humidity observations: Initial results
Harri, A-M; Genzer, M; Kemppinen, O; Gomez-Elvira, J; Haberle, R; Polkko, J; Savijärvi, H; Rennó, N; Rodriguez-Manfredi, JA; Schmidt, W; Richardson, M; Siili, T; Paton, M; Torre-Juarez, M De La; Mäkinen, T; Newman, C; Rafkin, S; Mischna, M; Merikallio, S; Haukka, H; Martin-Torres, J; Komu, M; Zorzano, M-P; Peinado, V; Vazquez, L; Urqui, R
2014-01-01
The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers. Key Points Atmospheric water mixing ratio at Gale crater varies from 30 to 140 ppm MSL relative humidity observation provides good data Highest detected relative humidity reading during first MSL 100 sols is RH75% PMID:26213667
NASA Astrophysics Data System (ADS)
Yudin, V. A.; England, S.; Liu, H.; Solomon, S. C.; Immel, T. J.; Maute, A. I.; Burns, A. G.; Foster, B.; Wu, Q.; Goncharenko, L. P.
2013-12-01
We examine the capability of novel configurations of community models, WACCM-X and TIME-GCM, to support current and forthcoming space-borne missions to monitor the dynamics and composition of the Mesosphere-Thermosphere-Ionosphere (MTI) system. In these configurations the lower atmosphere of WACCM-X is constrained by operational analyses and/or short-term forecasts provided by the Goddard Earth Observing System (GEOS-5) of Global Modeling and Assimilation Office at NASA/GSFC. With the terrestrial weather of GEOS-5 and updated model physics the simulations in the MTI are capable to reproduce observed signatures of the perturbed wave dynamics and ion-neutral coupling during recent stratospheric warming events, short-term, annual and year-to-year variability of prevailing flows, planetary waves, tides, and composition. These 'terrestrial-weather' driven simulations with day-to-day variable solar and geomagnetic inputs can provide background state (first guess) and error statistics for the inverse algorithms of new NASA missions, ICON and GOLD at locations and time of observations in the MTI region. With two different viewing geometries (sun-synchronous and geostationary) of instruments, ICON and GOLD will provide complimentary global observations of temperature, winds and constituents to constrain the first-principle forecast models. This paper will discuss initial design of Observing Simulation Experiments (OSE) in WACCM-X/GEOS-5 and TIME-GCM. As recognized, OSE represent an excellent learning tool for designing and evaluating observing capabilities of novel sensors. They can guide on how to integrate/combine information from different instruments. The choice of assimilation schemes, forecast and observational errors will be discussed along with challenges and perspectives to constrain fast-varying tidal dynamics and their effects in models by combination of sun-synchronous and geostationary observations of ICON and GOLD. We will also discuss how correlative space
Space Geodetic Technique Co-location in Space: Simulation Results for the GRASP Mission
NASA Astrophysics Data System (ADS)
Kuzmicz-Cieslak, M.; Pavlis, E. C.
2011-12-01
The Global Geodetic Observing System-GGOS, places very stringent requirements in the accuracy and stability of future realizations of the International Terrestrial Reference Frame (ITRF): an origin definition at 1 mm or better at epoch and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale (0.1 ppb) and orientation components. These goals were derived from the requirements of Earth science problems that are currently the international community's highest priority. None of the geodetic positioning techniques can achieve this goal alone. This is due in part to the non-observability of certain attributes from a single technique. Another limitation is imposed from the extent and uniformity of the tracking network and the schedule of observational availability and number of suitable targets. The final limitation derives from the difficulty to "tie" the reference points of each technique at the same site, to an accuracy that will support the GGOS goals. The future GGOS network will address decisively the ground segment and to certain extent the space segment requirements. The JPL-proposed multi-technique mission GRASP (Geodetic Reference Antenna in Space) attempts to resolve the accurate tie between techniques, using their co-location in space, onboard a well-designed spacecraft equipped with GNSS receivers, a SLR retroreflector array, a VLBI beacon and a DORIS system. Using the anticipated system performance for all four techniques at the time the GGOS network is completed (ca 2020), we generated a number of simulated data sets for the development of a TRF. Our simulation studies examine the degree to which GRASP can improve the inter-technique "tie" issue compared to the classical approach, and the likely modus operandi for such a mission. The success of the examined scenarios is judged by the quality of the origin and scale definition of the resulting TRF.
Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables
NASA Astrophysics Data System (ADS)
Martínez-Sykora, Juan; De Pontieu, Bart; De Moortel, Ineke; Hansteen, Viggo H.; Carlsson, Mats
2018-06-01
The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations, including ion–neutral interaction effects with the Bifrost code. We find that the formation of simulated type II spicules, driven by the release of magnetic tension, impacts the corona in various manners. Associated with the formation of spicules, the corona exhibits (1) magneto-acoustic shocks and flows, which supply mass to coronal loops, and (2) transversal magnetic waves and electric currents that propagate at Alfvén speeds. The transversal waves and electric currents, generated by the spicule’s driver and lasting for many minutes, are dissipated and heat the associated loop. These complex interactions in the corona can be connected with blueshifted secondary components in coronal spectral lines (red–blue asymmetries) observed with Hinode/EIS and SOHO/SUMER, as well as the EUV counterpart of type II spicules and propagating coronal disturbances observed with the 171 Å and 193 Å SDO/AIA channels.
NASA Astrophysics Data System (ADS)
Pierre, M.; Pacaud, F.; Adami, C.; Alis, S.; Altieri, B.; Baran, N.; Benoist, C.; Birkinshaw, M.; Bongiorno, A.; Bremer, M. N.; Brusa, M.; Butler, A.; Ciliegi, P.; Chiappetti, L.; Clerc, N.; Corasaniti, P. S.; Coupon, J.; De Breuck, C.; Democles, J.; Desai, S.; Delhaize, J.; Devriendt, J.; Dubois, Y.; Eckert, D.; Elyiv, A.; Ettori, S.; Evrard, A.; Faccioli, L.; Farahi, A.; Ferrari, C.; Finet, F.; Fotopoulou, S.; Fourmanoit, N.; Gandhi, P.; Gastaldello, F.; Gastaud, R.; Georgantopoulos, I.; Giles, P.; Guennou, L.; Guglielmo, V.; Horellou, C.; Husband, K.; Huynh, M.; Iovino, A.; Kilbinger, M.; Koulouridis, E.; Lavoie, S.; Le Brun, A. M. C.; Le Fevre, J. P.; Lidman, C.; Lieu, M.; Lin, C. A.; Mantz, A.; Maughan, B. J.; Maurogordato, S.; McCarthy, I. G.; McGee, S.; Melin, J. B.; Melnyk, O.; Menanteau, F.; Novak, M.; Paltani, S.; Plionis, M.; Poggianti, B. M.; Pomarede, D.; Pompei, E.; Ponman, T. J.; Ramos-Ceja, M. E.; Ranalli, P.; Rapetti, D.; Raychaudury, S.; Reiprich, T. H.; Rottgering, H.; Rozo, E.; Rykoff, E.; Sadibekova, T.; Santos, J.; Sauvageot, J. L.; Schimd, C.; Sereno, M.; Smith, G. P.; Smolčić, V.; Snowden, S.; Spergel, D.; Stanford, S.; Surdej, J.; Valageas, P.; Valotti, A.; Valtchanov, I.; Vignali, C.; Willis, J.; Ziparo, F.
2016-06-01
Context. The quest for the cosmological parameters that describe our universe continues to motivate the scientific community to undertake very large survey initiatives across the electromagnetic spectrum. Over the past two decades, the Chandra and XMM-Newton observatories have supported numerous studies of X-ray-selected clusters of galaxies, active galactic nuclei (AGNs), and the X-ray background. The present paper is the first in a series reporting results of the XXL-XMM survey; it comes at a time when the Planck mission results are being finalised. Aims: We present the XXL Survey, the largest XMM programme totaling some 6.9 Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25 deg2 each at a point-source sensitivity of ~5 × 10-15 erg s-1 cm-2 in the [0.5-2] keV band (completeness limit). The survey's main goals are to provide constraints on the dark energy equation of state from the space-time distribution of clusters of galaxies and to serve as a pathfinder for future, wide-area X-ray missions. We review science objectives, including cluster studies, AGN evolution, and large-scale structure, that are being conducted with the support of approximately 30 follow-up programmes. Methods: We describe the 542 XMM observations along with the associated multi-λ and numerical simulation programmes. We give a detailed account of the X-ray processing steps and describe innovative tools being developed for the cosmological analysis. Results: The paper provides a thorough evaluation of the X-ray data, including quality controls, photon statistics, exposure and background maps, and sky coverage. Source catalogue construction and multi-λ associations are briefly described. This material will be the basis for the calculation of the cluster and AGN selection functions, critical elements of the cosmological and science analyses. Conclusions: The XXL multi-λ data set will have a unique lasting legacy
NASA Astrophysics Data System (ADS)
Juza, Mélanie; Renault, Lionel; Ruiz, Simon; Heslop, Emma; Tintoré, Joaquin
2013-04-01
The Winter Intermediate Water (WIW) plays a crucial role in the water exchanges through the Balearic channels and in the Western Mediterranean Sea general circulation. Its formation occurs in the North-Western of the basin under severe winter conditions. Observational datasets (in situ temperature and salinity profiles collected during CTD and glider transects) reveal the presence of WIW in the Gulf of Lion and in the Ibiza Channel during the winter-spring 2011. However, the inhomogeneous spatial and temporal coverage of the observational array makes the monitoring of WIW through the basin difficult. In this study, as a complement to the observations, a ROMS 1/40° regional oceanic simulation implemented over the Western Mediterranean Sea is used to determine the origin, evolution and pathways of the WIW in the basin. The simulation outputs are first collocated at the observation positions. Their comparison against the observations shows the ability of the simulation to reproduce the observed WIW in the Gulf of Lion in March 2011 and in the Ibiza channel in winter-spring 2011. Then, the fully-sampled simulation outputs are used to study the spatial and temporal variability of the WIW in the Western Mediterranean Sea during the winter 2011. Investigating the T/S diagrams and transports in key sections over the basin and calculating lagrangian trajectories, the main pathways of WIW in winter-spring 2011 emerge. We show that, in good agreement with the literature, the simulated WIW are formed along the continental shelves of the Gulf of Lion and Catalan Sea, and then circulate souththward in the Balearic Sea reaching 100-200m depth. One branch (mainly formed in the Ebro estuary) goes through the Ibiza Channel, while the second main branch (coming from both the Gulf of Lion and the Ebro estuary) splits to the East joining the Balearic Current.
Fewer clouds in the Mediterranean: consistency of observations and climate simulations
Sanchez-Lorenzo, Arturo; Enriquez-Alonso, Aaron; Calbó, Josep; González, Josep-Abel; Wild, Martin; Folini, Doris; Norris, Joel R.; Vicente-Serrano, Sergio M.
2017-01-01
Clouds play a major role in the climate system, but large uncertainties remain about their decadal variations. Here we report a widespread decrease in cloud cover since the 1970 s over the Mediterranean region, in particular during the 1970 s–1980 s, especially in the central and eastern areas and during springtime. Confidence in these findings is high due to the good agreement between the interannual variations of cloud cover provided by surface observations and several satellite-derived and reanalysis products, although some discrepancies exist in their trends. Climate model simulations of the historical experiment from the Coupled Model Intercomparison Project Phase 5 (CMIP5) also exhibit a decrease in cloud cover over the Mediterranean since the 1970 s, in agreement with surface observations, although the rate of decrease is slightly lower. The observed northward expansion of the Hadley cell is discussed as a possible cause of detected trends. PMID:28148960
NASA Technical Reports Server (NTRS)
Luo, Yali; Xu, Kuan-Man; Morrison, Hugh; McFarquhar, Greg M.; Wang, Zhien; Zhang, Gong
2007-01-01
A cloud-resolving model (CRM) is used to simulate the multiple-layer mixed-phase stratiform (MPS) clouds that occurred during a three-and-a-half day subperiod of the Department of Energy-Atmospheric Radiation Measurement Program s Mixed-Phase Arctic Cloud Experiment (M-PACE). The CRM is implemented with an advanced two-moment microphysics scheme, a state-of-the-art radiative transfer scheme, and a complicated third-order turbulence closure. Concurrent meteorological, aerosol, and ice nucleus measurements are used to initialize the CRM. The CRM is prescribed by time-varying large-scale advective tendencies of temperature and moisture and surface turbulent fluxes of sensible and latent heat. The CRM reproduces the occurrences of the single- and double-layer MPS clouds as revealed by the M-PACE observations. However, the simulated first cloud layer is lower and the second cloud layer thicker compared to observations. The magnitude of the simulated liquid water path agrees with that observed, but its temporal variation is more pronounced than that observed. As in an earlier study of single-layer cloud, the CRM also captures the major characteristics in the vertical distributions and temporal variations of liquid water content (LWC), total ice water content (IWC), droplet number concentration and ice crystal number concentration (nis) as suggested by the aircraft observations. However, the simulated mean values differ significantly from the observed. The magnitude of nis is especially underestimated by one order of magnitude. Sensitivity experiments suggest that the lower cloud layer is closely related to the surface fluxes of sensible and latent heat; the upper cloud layer is probably initialized by the large-scale advective cooling/moistening and maintained through the strong longwave (LW) radiative cooling near the cloud top which enhances the dynamical circulation; artificially turning off all ice-phase microphysical processes results in an increase in LWP by a
Experimental and simulation study results for video landmark acquisition and tracking technology
NASA Technical Reports Server (NTRS)
Schappell, R. T.; Tietz, J. C.; Thomas, H. M.; Lowrie, J. W.
1979-01-01
A synopsis of related Earth observation technology is provided and includes surface-feature tracking, generic feature classification and landmark identification, and navigation by multicolor correlation. With the advent of the Space Shuttle era, the NASA role takes on new significance in that one can now conceive of dedicated Earth resources missions. Space Shuttle also provides a unique test bed for evaluating advanced sensor technology like that described in this report. As a result of this type of rationale, the FILE OSTA-1 Shuttle experiment, which grew out of the Video Landmark Acquisition and Tracking (VILAT) activity, was developed and is described in this report along with the relevant tradeoffs. In addition, a synopsis of FILE computer simulation activity is included. This synopsis relates to future required capabilities such as landmark registration, reacquisition, and tracking.
NASA Astrophysics Data System (ADS)
Stern, Daniel P.
The vertical structure of the tangential wind field in tropical cyclones is investigated through observations, theory, and numerical simulations. First, a dataset of Doppler radar wind swaths obtained from NOAA/AOML/HRD is used to create azimuthal mean tangential wind fields for 7 storms on 17 different days. Three conventional wisdoms of vertical structure are reexamined: the outward slope of the Radius of Maximum Winds (RMW) decreases with increasing intensity, the slope increases with the size of the RMW, and the RMW is a surface of constant absolute angular momentum (M). The slopes of the RMW and of M surfaces are objectively determined. The slopes are found to increase linearly with the size of the low-level RMW, and to be independent of the intensity of the storm. While the RMW is approximately an M surface, M systematically decreases with height along the RMW. The steady-state analytical theory of Emanuel (1986) is shown to make specific predictions regarding the vertical structure of tropical cyclones. It is found that in this model, the slope of the RMW is a linear function of its size and is independent of intensity, and that the RMW is almost exactly an M surface. A simple time-dependent model which is governed by the same assumptions as the analytical theory yields the same results. Idealized hurricane simulations are conducted using the Weather Research and Forecasting (WRF) model. The assumptions of Emanuel's theory, slantwise moist neutrality and thermal wind balance, are both found to be violated. Nevertheless, the vertical structure of the wind field itself is generally well predicted by the theory. The percentage rate at which the winds decay with height is found to be nearly independent of both size and intensity, in agreement with observations and theory. Deviations from this decay profile are shown to be due to gradient wind imbalance. The slope of the RMW increases linearly with its size, but is systematically too large compared to
Positive state observer for the automatic control of the depth of anesthesia-Clinical results.
Nogueira, Filipa N; Mendonça, T; Rocha, P
2016-09-13
The depth of anesthesia (DoA) is a crucial feature in general anesthesia. Nowadays the DoA is usually evaluated by the bispectral index (BIS). According to the surgical procedure, different reference levels for the BIS may be clinically required. This can be achieved by the simultaneous administration of an analgesic (e.g. remifentanil) and an hypnotic (eg propofol). As a contribution to the effort of automating the processes of drug delivery in general anesthesia, in this paper, a positive state observer is designed for the implementation of a control scheme proposed for the automatic administration of propofol and of remifentanil, in order to track a desired level for the BIS. It is proved and illustrated by simulations that the controller-observer scheme has a very good performance. This scheme was implemented, tested and evaluated both by means of simulations and for a set of patients during surgical procedures. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
The spiral-compact galaxy pair AM 2208-251: Computer simulations versus observations
NASA Technical Reports Server (NTRS)
Klaric, Mario; Byrd, Gene G.
1990-01-01
The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral. Bertola, Huchtmeier, and Zeilinger (1990) have presented optical spectroscopic as well as single dish 21 cm observations of this system. Their spectroscopic data show, via emission lines lambda lambda 3727-29A, a rising rotation curve near the nucleus. These spectroscopic observations may indicate a tidal interaction in the system. In order to learn more about such pairs, the authors simulated the interaction using the computer model developed by Miller (1976 a,b, 1978) and modified by the authors (Byrd 1986, 1987, 1988). To do the simulation they need an idea of the mutual orbits of the two galaxies. Their computer model is a two-dimensional polar N-body program. It consists of a self-gravitating disk of particles, within an inert axially symmetric stabilizing halo potential. The particles are distributed in a 24(radial) by 36(azimuthal) polar grid. Self consistent calculations can be done only within the grid area. The disk is modeled with a finite Mestel disk, where all the particles initially move in circular orbits with constant tangential velocities (Mestel 1963), resulting in a flat rotation curve. The gas particles in the spiral's disk, which make up 30 percent of its mass, collide in the following manner. The number of particles in each bin of the polar grid is counted every time step. If it is greater than a given critical density, all the particles in the bin collide, obtaining in the result the same velocities, equal to the average for the bin. This process produces clumps of gas particles-the star formation sites. The authors suppress the collision in the inner part of the disk (within the circle r = 6) to represent the hole seen in the gas in the nuclear bulge of spirals. They thus avoid spurious effects due to collisions in that region. They also varied the size of
NASA Astrophysics Data System (ADS)
Inoue, S.; Hayashi, K.; Magara, T.; Choe, G. S.; Park, Y. D.
2014-06-01
We performed a magnetohydrodynamic (MHD) simulation using a nonlinear force-free field (NLFFF) in solar active region 11158 to clarify the dynamics of an X2.2-class solar flare. We found that the NLFFF never shows the dramatic dynamics seen in observations, i.e., it is in a stable state against the perturbations. On the other hand, the MHD simulation shows that when the strongly twisted lines are formed at close to the neutral line, which are produced via tether-cutting reconnection in the twisted lines of the NLFFF, they consequently erupt away from the solar surface via the complicated reconnection. This result supports the argument that the strongly twisted lines formed in NLFFF via tether-cutting reconnection are responsible for breaking the force balance condition of the magnetic fields in the lower solar corona. In addition to this, the dynamical evolution of these field lines reveals that at the initial stage the spatial pattern of the footpoints caused by the reconnection of the twisted lines appropriately maps the distribution of the observed two-ribbon flares. Interestingly, after the flare, the reconnected field lines convert into a structure like the post-flare loops, which is analogous to the extreme ultraviolet image taken by the Solar Dynamics Observatory. Eventually, we found that the twisted lines exceed a critical height at which the flux tube becomes unstable to the torus instability. These results illustrate the reliability of our simulation and also provide an important relationship between flare and coronal mass ejection dynamics.
Simulation results of corkscrew motion in DARHT-II
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chan, K. D.; Ekdahl, C. A.; Chen, Y. J.
2003-01-01
DARHT-II, the second axis of the Dual-Axis Radiographic Hydrodynamics Test Facility, is being commissioned. DARHT-II is a linear induction accelerator producing 2-microsecond electron beam pulses at 20 MeV and 2 kA. These 2-microsecond pulses will be chopped into four short pulses to produce time resolved x-ray images. Radiographic application requires the DARHT-II beam to have excellent beam quality, and it is important to study various beam effects that may cause quality degradation of a DARHT-II beam. One of the beam dynamic effects under study is 'corkscrew' motion. For corkscrew motion, the beam centroid is deflected off axis due to misalignmentsmore » of the solenoid magnets. The deflection depends on the beam energy variation, which is expected to vary by {+-}0.5% during the 'flat-top' part of a beam pulse. Such chromatic aberration will result in broadening of beam spot size. In this paper, we will report simulation results of our study of corkscrew motion in DARHT-II. Sensitivities of beam spot size to various accelerator parameters and the strategy for minimizing corkscrew motion will be described. Measured magnet misalignment is used in the simulation.« less
NASA Technical Reports Server (NTRS)
Bacmeister, Julio T.; Suarez, Max J.; Einaudi, Franco (Technical Monitor)
2001-01-01
This is the first of a two part study examining the connection of the equatorial momentum budget in an AGCM (Atmospheric General Circulation Model), with simulated equatorial surface wind stresses over the Pacific. The AGCM used in this study forms part of a newly developed coupled forecasting system used at NASA's Seasonal- to-Interannual Prediction Project. Here we describe the model and present results from a 20-year (1979-1999) AMIP-type experiment forced with observed SSTs (Sea Surface Temperatures). Model results are compared them with available observational data sets. The climatological pattern of extra-tropical planetary waves as well as their ENSO-related variability is found to agree quite well with re-analysis estimates. The model's surface wind stress is examined in detail, and reveals a reasonable overall simulation of seasonal interannual variability, as well as seasonal mean distributions. However, an excessive annual oscillation in wind stress over the equatorial central Pacific is found. We examine the model's divergent circulation over the tropical Pacific and compare it with estimates based on re-analysis data. These comparisons are generally good, but reveal excessive upper-level convergence in the central Pacific. In Part II of this study a direct examination of individual terms in the AGCM's momentum budget is presented. We relate the results of this analysis to the model's simulation of surface wind stress.
NASA Astrophysics Data System (ADS)
Wu, C.; Liu, X.; Diao, M.; Zhang, K.; Gettelman, A.
2015-12-01
A dominant source of uncertainty within climate system modeling lies in the representation of cloud processes. This is not only because of the great complexity in cloud microphysics, but also because of the large variations of cloud amount and macroscopic properties in time and space. In this study, the cloud properties simulated by the Community Atmosphere Model version 5.4 (CAM5.4) are evaluated using the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011). CAM5.4 is driven by the meteorology (U, V, and T) from GEOS5 analysis, while water vapor, hydrometeors and aerosols are calculated by the model itself. For direct comparison of CAM5.4 and HIPPO observations, model output is collocated with HIPPO flights. Generally, the model has an ability to capture specific cloud systems of meso- to large-scales. In total, the model can reproduce 80% of observed cloud occurrences inside model grid boxes, and even higher (93%) for ice clouds (T≤-40°C). However, the model produces plenty of clouds that are not presented in the observation. The model also simulates significantly larger cloud fraction including for ice clouds compared to the observation. Further analysis shows that the overestimation is a result of bias in relative humidity (RH) in the model. The bias of RH can be mostly attributed to the discrepancies of water vapor, and to a lesser extent to those of temperature. Down to the micro-scale level of ice clouds, the model can simulate reasonably well the magnitude of ice and snow number concentration (Ni, with diameter larger than 75 μm). However, the model simulates fewer occurrences of Ni>50 L-1. This can be partially ascribed to the low bias of aerosol number concentration (Naer, with diameter between 0.1-1 μm) simulated by the model. Moreover, the model significantly underestimates both the number mean diameter (Di,n) and the volume mean diameter (Di,v) of ice/snow. The result shows that the underestimation may be related to a weaker positive relationship
Future missions for observing Earth's changing gravity field: a closed-loop simulation tool
NASA Astrophysics Data System (ADS)
Visser, P. N.
2008-12-01
The GRACE mission has successfully demonstrated the observation from space of the changing Earth's gravity field at length and time scales of typically 1000 km and 10-30 days, respectively. Many scientific communities strongly advertise the need for continuity of observing Earth's gravity field from space. Moreover, a strong interest is being expressed to have gravity missions that allow a more detailed sampling of the Earth's gravity field both in time and in space. Designing a gravity field mission for the future is a complicated process that involves making many trade-offs, such as trade-offs between spatial, temporal resolution and financial budget. Moreover, it involves the optimization of many parameters, such as orbital parameters (height, inclination), distinction between which gravity sources to observe or correct for (for example are gravity changes due to ocean currents a nuisance or a signal to be retrieved?), observation techniques (low-low satellite-to-satellite tracking, satellite gravity gradiometry, accelerometers), and satellite control systems (drag-free?). A comprehensive tool has been developed and implemented that allows the closed-loop simulation of gravity field retrievals for different satellite mission scenarios. This paper provides a description of this tool. Moreover, its capabilities are demonstrated by a few case studies. Acknowledgments. The research that is being done with the closed-loop simulation tool is partially funded by the European Space Agency (ESA). An important component of the tool is the GEODYN software, kindly provided by NASA Goddard Space Flight Center in Greenbelt, Maryland.
NASA Astrophysics Data System (ADS)
Sydorenko, D.; Rankin, R.
2013-12-01
We have developed a comprehensive two-dimensional (meridional) model of coupling between the magnetosphere and ionosphere that covers an altitude range from ~100 km to few thousand km at high latitudes [Sydorenko and Rankin, 2013]. The model describes propagation of inertial scale Alfven waves, including ponderomotive forces, and has a parametric model of energetic electron precipitation; it includes vertical ion flows and chemical reactions between ions and neutrals. Model results are presented that reproduce EISCAT radar observations of electron and ion temperatures, height integrated conductivity, ion densities, and ion flows during a period of ULF activity described in [Lester, Davies, and Yeoman, 2000]. We performed simulations where the precipitation and the Alfven wave perturb the ionosphere simultaneously. By adjusting parameters of the wave and the precipitation we have achieved qualitative, and sometimes even reasonable quantitative agreement between the observations and the simulation. The model results are discussed in the context of new results anticipated from the Canadian small satellite mission ePOP "Enhanced Polar Outflow Probe", scheduled for launch on September 9, 2013. Sydorenko D. and R. Rankin, 'Simulation of O+ upflows created by electron precipitation and Alfvén waves in the ionosphere' submitted to Journal of Geophysical Research, 2013. Lester M., J. A. Davies, and T. K. Yeoman, 'The ionospheric response during an interval of PC5 ULF wave activity', Ann. Geophysicae, v.18, p.257-261 (2000).
NASA Astrophysics Data System (ADS)
Rühs, Siren; Zhurbas, Victor; Durgadoo, Jonathan V.; Biastoch, Arne
2017-04-01
The Lagrangian description of fluid motion by sets of individual particle trajectories is extensively used to characterize connectivity between distinct oceanic locations. One important factor influencing the connectivity is the average rate of particle dispersal, generally quantified as Lagrangian diffusivity. In addition to Lagrangian observing programs, Lagrangian analyses are performed by advecting particles with the simulated flow field of ocean general circulation models (OGCMs). However, depending on the spatio-temporal model resolution, not all scale-dependent processes are explicitly resolved in the simulated velocity fields. Consequently, the dispersal of advective Lagrangian trajectories has been assumed not to be sufficiently diffusive compared to observed particle spreading. In this study we present a detailed analysis of the spatially variable lateral eddy diffusivity characteristics of advective drifter trajectories simulated with realistically forced OGCMs and compare them with estimates based on observed drifter trajectories. The extended Agulhas Current system around South Africa, known for its intricate mesoscale dynamics, serves as a test case. We show that a state-of-the-art eddy-resolving OGCM indeed features theoretically derived dispersion characteristics for diffusive regimes and realistically represents Lagrangian eddy diffusivity characteristics obtained from observed surface drifter trajectories. The estimates for the maximum and asymptotic lateral single-particle eddy diffusivities obtained from the observed and simulated drifter trajectories show a good agreement in their spatial pattern and magnitude. We further assess the sensitivity of the simulated lateral eddy diffusivity estimates to the temporal and lateral OGCM output resolution and examine the impact of the different eddy diffusivity characteristics on the Lagrangian connectivity between the Indian Ocean and the South Atlantic.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hu, Zhiyuan; Zhao, Chun; Huang, Jianping
A fully coupled meteorology-chemistry model (WRF-Chem, the Weather Research and Forecasting model coupled with chemistry) has been configured to conduct quasi-global simulation for 5 years (2010–2014) and evaluated with multiple observation data sets for the first time. The evaluation focuses on the simulation over the trans-Pacific transport region using various reanalysis and observational data sets for meteorological fields and aerosol properties. The simulation generally captures the overall spatial and seasonal variability of satellite retrieved aerosol optical depth (AOD) and absorbing AOD (AAOD) over the Pacific that is determined by the outflow of pollutants and dust and the emissions of marine aerosols.more » The assessment of simulated extinction Ångström exponent (EAE) indicates that the model generally reproduces the variability of aerosol size distributions as seen by satellites. In addition, the vertical profile of aerosol extinction and its seasonality over the Pacific are also well simulated. The difference between the simulation and satellite retrievals can be mainly attributed to model biases in estimating marine aerosol emissions as well as the satellite sampling and retrieval uncertainties. Compared with the surface measurements over the western USA, the model reasonably simulates the observed magnitude and seasonality of dust, sulfate, and nitrate surface concentrations, but significantly underestimates the peak surface concentrations of carbonaceous aerosol likely due to model biases in the spatial and temporal variability of biomass burning emissions and secondary organic aerosol (SOA) production. A sensitivity simulation shows that the trans-Pacific transported dust, sulfate, and nitrate can make significant contribution to surface concentrations over the rural areas of the western USA, while the peaks of carbonaceous aerosol surface concentrations are dominated by the North American emissions. Both the retrievals and simulation show
Hu, Zhiyuan; Zhao, Chun; Huang, Jianping; ...
2016-05-10
A fully coupled meteorology-chemistry model (WRF-Chem, the Weather Research and Forecasting model coupled with chemistry) has been configured to conduct quasi-global simulation for 5 years (2010–2014) and evaluated with multiple observation data sets for the first time. The evaluation focuses on the simulation over the trans-Pacific transport region using various reanalysis and observational data sets for meteorological fields and aerosol properties. The simulation generally captures the overall spatial and seasonal variability of satellite retrieved aerosol optical depth (AOD) and absorbing AOD (AAOD) over the Pacific that is determined by the outflow of pollutants and dust and the emissions of marine aerosols.more » The assessment of simulated extinction Ångström exponent (EAE) indicates that the model generally reproduces the variability of aerosol size distributions as seen by satellites. In addition, the vertical profile of aerosol extinction and its seasonality over the Pacific are also well simulated. The difference between the simulation and satellite retrievals can be mainly attributed to model biases in estimating marine aerosol emissions as well as the satellite sampling and retrieval uncertainties. Compared with the surface measurements over the western USA, the model reasonably simulates the observed magnitude and seasonality of dust, sulfate, and nitrate surface concentrations, but significantly underestimates the peak surface concentrations of carbonaceous aerosol likely due to model biases in the spatial and temporal variability of biomass burning emissions and secondary organic aerosol (SOA) production. A sensitivity simulation shows that the trans-Pacific transported dust, sulfate, and nitrate can make significant contribution to surface concentrations over the rural areas of the western USA, while the peaks of carbonaceous aerosol surface concentrations are dominated by the North American emissions. Both the retrievals and simulation show
NASA Astrophysics Data System (ADS)
Hu, Zhiyuan; Zhao, Chun; Huang, Jianping; Leung, L. Ruby; Qian, Yun; Yu, Hongbin; Huang, Lei; Kalashnikova, Olga V.
2016-05-01
A fully coupled meteorology-chemistry model (WRF-Chem, the Weather Research and Forecasting model coupled with chemistry) has been configured to conduct quasi-global simulation for 5 years (2010-2014) and evaluated with multiple observation data sets for the first time. The evaluation focuses on the simulation over the trans-Pacific transport region using various reanalysis and observational data sets for meteorological fields and aerosol properties. The simulation generally captures the overall spatial and seasonal variability of satellite retrieved aerosol optical depth (AOD) and absorbing AOD (AAOD) over the Pacific that is determined by the outflow of pollutants and dust and the emissions of marine aerosols. The assessment of simulated extinction Ångström exponent (EAE) indicates that the model generally reproduces the variability of aerosol size distributions as seen by satellites. In addition, the vertical profile of aerosol extinction and its seasonality over the Pacific are also well simulated. The difference between the simulation and satellite retrievals can be mainly attributed to model biases in estimating marine aerosol emissions as well as the satellite sampling and retrieval uncertainties. Compared with the surface measurements over the western USA, the model reasonably simulates the observed magnitude and seasonality of dust, sulfate, and nitrate surface concentrations, but significantly underestimates the peak surface concentrations of carbonaceous aerosol likely due to model biases in the spatial and temporal variability of biomass burning emissions and secondary organic aerosol (SOA) production. A sensitivity simulation shows that the trans-Pacific transported dust, sulfate, and nitrate can make significant contribution to surface concentrations over the rural areas of the western USA, while the peaks of carbonaceous aerosol surface concentrations are dominated by the North American emissions. Both the retrievals and simulation show small
NASA Astrophysics Data System (ADS)
Choi, Y.; Li, X.; Czader, B.
2014-12-01
Three WRF simulations for the DISCOVER-AQ 2013 Texas campaign period (30 days in September) are performed to characterize uncertainties in the simulated meteorological and chemical conditions. These simulations differ in domain setup, and in performing observation nudging in WRF runs. There are around 7% index of agreement (IOA) gain in temperature and 9-12% boost in U-WIND and V-WIND when the observational nudging is employed in the simulation. Further performance gain from nested domains over single domain is marginal. The CMAQ simulations based on above WRF setups showed that the ozone performance slightly improved in the simulation for which objective analysis (OA) is carried out. Further IOA gain, though quite limited, is achieved with nested domains. This study shows that the high ozone episodes during the analyzed time periods were associated with the uncertainties of the simulated cold front passage, chemical boundary condition and small-scale temporal wind fields. All runs missed the observed high ozone values which reached above 150 ppb in La Porte on September 25, the only day with hourly ozone over 120 ppb. The failure is likely due to model's inability to catch small-scale wind shifts in the industrial zone, despite better wind directions in the simulations with nudging and nested domains. This study also shows that overestimated background ozone from the southerly chemical boundary is a critical source for the model's general overpredictions of the ozone concentrations from CMAQ during September of 2013. These results of this study shed a light on the necessity of (1) capturing the small-scale winds such as the onsets of bay-breeze or sea-breeze and (2) implementing more accurate chemical boundary conditions to reduce the simulated high-biased ozone concentrations. One promising remedy for (1) is implementing hourly observation nudging instead of the standard one which is done every three hours.
Methane over South Asian region from GOSAT observations and ACTM simulations
NASA Astrophysics Data System (ADS)
Chandra, N.; Hayashida, S.; Patra, P. K.; Saeki, T.
2017-12-01
Methane (CH4) is one of the most important short-lived climate forcers. About 8% of global CH4 emissions are estimated from South Asia, covering less than 1% of global land. However, large uncertainty prevails in the sectorial CH4 emissions because of the lack of measurements. With the availability of total column methane (XCH4) observations by satellites, variability in XCH4 have been captured for most parts of the global land with major emissions, which were otherwise not covered by the surface observation network. However, direct use of satellite data for estimating emissions by inversion analysis is highly ambiguous, unlike the in-situ measurements near the source region, XCH4 values are controlled by surface emission and CH4 abundances at all altitudes. Therefore, understanding the role of transport along with the emissions on XCH4 is necessary before using the XCH4 data for the inversion analysis. We analyzed XCH4 observed by the GHGs Observation SATellite (GOSAT) and simulations over the South Asia region using the JAMSTEC's atmospheric chemistry-transport model (ACTM). The analysis suggests that distinct XCH4 seasonal cycle over northern and southern regions of India is governed by the both heterogeneous distributions of surface emissions and variability in partial CH4 column in the upper troposphere. Using ACTM simulations, we find that over most part of the northern Indian regions up to 40% of the seasonal peak during the southwest (SW) monsoon is attributed to the lower troposphere ( 1000-600 hPa), while 40% to uplifted high-CH4 air masses in the upper troposphere ( 600-200 hPa). In contrast, XCH4 seasonal enhancement over the semi-arid region, with extremely low CH4 emissions, is attributed mainly ( 70%) to partial XCH4 variability in the upper troposphere. The lower tropospheric region contributes up to 60% in the XCH4 seasonal enhancement over the southern peninsula and oceanic region. These differences arise from the complex atmospheric transport
NASA Astrophysics Data System (ADS)
Fen, Cao; XuHai, Yang; ZhiGang, Li; ChuGang, Feng
2016-08-01
The normal consecutive observing model in Chinese Area Positioning System (CAPS) can only supply observations of one GEO satellite in 1 day from one station. However, this can't satisfy the project need for observing many GEO satellites in 1 day. In order to obtain observations of several GEO satellites in 1 day like GPS/GLONASS/Galileo/BeiDou, the time-sharing observing model for GEO satellites in CAPS needs research. The principle of time-sharing observing model is illuminated with subsequent Precise Orbit Determination (POD) experiments using simulated time-sharing observations in 2005 and the real time-sharing observations in 2015. From time-sharing simulation experiments before 2014, the time-sharing observing 6 GEO satellites every 2 h has nearly the same orbit precision with the consecutive observing model. From POD experiments using the real time-sharing observations, POD precision for ZX12# and Yatai7# are about 3.234 m and 2.570 m, respectively, which indicates the time-sharing observing model is appropriate for CBTR system and can realize observing many GEO satellites in 1 day.
NASA Astrophysics Data System (ADS)
Hopkins, Julia; Elgar, Steve; Raubenheimer, Britt
2017-04-01
Accurately characterizing the interaction of waves and currents can improve predictions of wave propagation and subsequent sediment transport in the nearshore. Along the southern shoreline of Martha's Vineyard, MA, waves propagate across strong tidal currents as they shoal, providing an ideal environment for investigating wave-current interaction. Wave directions and mean currents observed for two 1-month-long periods in 7- and 2-m water depths along 11 km of the Martha's Vineyard shoreline have strong tidal modulations. Wave directions shift by as much as 70 degrees over a tidal cycle in 7 m depth, and by as much as 25 degrees in 2 m depth. The magnitude of the tidal modulations in the wave field decreases alongshore to the west, consistent with the observed decrease in tidal currents from 2.1 to 0.2 m/s. The observations are reproduced accurately by a numerical model (SWAN and Deflt3D-FLOW) that simulates waves and currents over the observed bathymetry. Model simulations with and without wave-current interaction and tidal depth changes demonstrate that the observed tidal modulations of the wave field primarily are caused by wave-current interaction and not by tidal changes to water depths over the nearby complex shoals. Sediment transport estimates from simulated wave conditions using a range of tidal currents and offshore wave fields indicate that the modulation of the wave field at Martha's Vineyard can impact the direction of wave-induced alongshore sediment transport, sometimes driving transport opposing the direction of the offshore incident wave field. As such, the observations and model simulations suggest the importance of wave-current interaction to tidally averaged transport in mixed-energy wave-and-current nearshore environments. Supported by ASD(R&E), NSF, NOAA (Sea Grant), and ONR.
NASA Astrophysics Data System (ADS)
Schoof, J. T.; Pryor, S. C.; Barthelmie, R. J.
2013-12-01
Previous research has indicated that large-scale modes of climate variability, such as El Niño - Southern Oscillation (ENSO), the Arctic Oscillation (AO) and the Pacific-North American pattern (PNA), influence the inter-annual and intra-annual variability of near-surface and upper-level wind speeds over the United States. For example, we have shown that rawinsonde derived wind speeds indicate that 90th percentile of wind speeds at 700 hPa over the Pacific Northwest and Southwestern USA are significantly higher under the negative phase of the PNA, and the Central Plains experiences higher wind speeds at 850 hPa under positive phase Southern Oscillation index while the Northeast exhibits higher wind speeds at 850 hPa under positive phase NAO. Here, we extend this research by further investigating these relationships using both reanalysis products and output from coupled atmosphere-ocean general circulation models (AOGCMs) developed for the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). The research presented has two specific goals. First, we evaluate the AOGCM simulations in terms of their ability to represent the temporal and spatial representations of ENSO, the AO, and the PNA pattern relative to historical observations. The diagnostics used include calculation of the power spectra (and thus representation of the fundamental frequencies of variability) and Taylor diagrams (for comparative assessment of the spatial patterns and their intensities). Our initial results indicate that most AOGCMs produce modes that are qualitatively similar to those observed, but that differ slightly in terms of the spatial pattern, intensity of specific centers of action, and variance explained. Figure 1 illustrates an example of the analysis of the frequencies of variability of two climate modes for the NCEP-NCAR reanalysis (NNR) and a single AOGCM (BCC CSM1). The results show a high degree of similarity in the power spectra but for this AOGCM the variance of the PNA
NASA Technical Reports Server (NTRS)
Clauer, C. Robert; Friis-Christensen, Eigil
1988-01-01
On July 23, 1983 the IMF turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, the onset of the reconfiguration of the high-latitude ionospheric currents is found to occur about 3 min after the northward IMF encounters the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. These observations and the results of numerical simulations indicate that the dayside polar-cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind.
Three-Dimensional Imaging in Rhinoplasty: A Comparison of the Simulated versus Actual Result.
Persing, Sarah; Timberlake, Andrew; Madari, Sarika; Steinbacher, Derek
2018-05-22
Computer imaging has become increasingly popular for rhinoplasty. Three-dimensional (3D) analysis permits a more comprehensive view from multiple vantage points. However, the predictability and concordance between the simulated and actual result have not been morphometrically studied. The purpose of this study was to aesthetically and quantitatively compare the simulated to actual rhinoplasty result. A retrospective review of 3D images (VECTRA, Canfield) for rhinoplasty patients was performed. Images (preop, simulated, and actual) were randomized. A blinded panel of physicians rated the images (1 = poor, 5 = excellent). The image series considered "best" was also recorded. A quantitative assessment of nasolabial angle and tip projection was compared. Paired and two-sample t tests were performed for statistical analysis (P < 0.05 as significant). Forty patients were included. 67.5% of preoperative images were rated as poor (mean = 1.7). The simulation received a mean score of 2.9 (good in 60% of cases). 82.5% of actual cases were rated good to excellent (mean 3.4) (P < 0.001). Overall, the panel significantly preferred the actual postoperative result in 77.5% of cases compared to the simulation in 22.5% of cases (P < 0.001). The actual nasal tip was more projected compared to the simulations for both males and females. There was no significant difference in nasal tip rotation between simulated and postoperative groups. 3D simulation is a powerful communication and planning tool in rhinoplasty. In this study, the actual result was deemed more aesthetic than the simulated image. Surgeon experience is important to translate the plan and achieve favorable postoperative results. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .
NASA Astrophysics Data System (ADS)
Sybilska, Agnieszka; Łokas, Ewa Luiza; Fouquet, Sylvain
2017-03-01
We combine high-quality IFU data with a new set of numerical simulations to study low-mass early type galaxies (dEs) in dense environments. Our earlier study of dEs in the Virgo cluster has produced the first large-scale maps of kinematic and stellar population properties of dEs in those environments (Ryś et al. 2013, 2014, 2015). A quantitative discrimination between various (trans)formation processes proposed for these objects is, however, a complex issue, requiring a priori assumptions about the progenitors of galaxies we observe and study today. To bridge this gap between observations and theoretical predictions, we use the expertise gained in the IFU data analysis to look ``through the eye of SAURON'' at our new suite of high-resolution N-body simulations of dEs in the Virgo cluster. Mimicking the observers perspective as closely as possible, we can also indicate the existing instrumental and viewer limitations regarding what we are/are not able to detect as observers.
Status of the NASA GMAO Observing System Simulation Experiment
NASA Technical Reports Server (NTRS)
Prive, Nikki C.; Errico, Ronald M.
2014-01-01
An Observing System Simulation Experiment (OSSE) is a pure modeling study used when actual observations are too expensive or difficult to obtain. OSSEs are valuable tools for determining the potential impact of new observing systems on numerical weather forecasts and for evaluation of data assimilation systems (DAS). An OSSE has been developed at the NASA Global Modeling and Assimilation Office (GMAO, Errico et al 2013). The GMAO OSSE uses a 13-month integration of the European Centre for Medium- Range Weather Forecasts 2005 operational model at T511/L91 resolution for the Nature Run (NR). Synthetic observations have been updated so that they are based on real observations during the summer of 2013. The emulated observation types include AMSU-A, MHS, IASI, AIRS, and HIRS4 radiance data, GPS-RO, and conventional types including aircraft, rawinsonde, profiler, surface, and satellite winds. The synthetic satellite wind observations are colocated with the NR cloud fields, and the rawinsondes are advected during ascent using the NR wind fields. Data counts for the synthetic observations are matched as closely as possible to real data counts, as shown in Figure 2. Errors are added to the synthetic observations to emulate representativeness and instrument errors. The synthetic errors are calibrated so that the statistics of observation innovation and analysis increments in the OSSE are similar to the same statistics for assimilation of real observations, in an iterative method described by Errico et al (2013). The standard deviations of observation minus forecast (xo-H(xb)) are compared for the OSSE and real data in Figure 3. The synthetic errors include both random, uncorrelated errors, and an additional correlated error component for some observational types. Vertically correlated errors are included for conventional sounding data and GPS-RO, and channel correlated errors are introduced to AIRS and IASI (Figure 4). HIRS, AMSU-A, and MHS have a component of horizontally
NASA Astrophysics Data System (ADS)
Dunning, C.; Black, E.; Allan, R. P.
2017-12-01
The seasonality of rainfall over Africa plays a key role in determining socio-economic impacts for agricultural stakeholders, influences energy supply from hydropower, affects the length of the malaria transmission season and impacts surface water supplies. Hence, failure or delays of these rains can lead to significant socio-economic impacts. Diagnosing and interpreting interannual variability and long-term trends in seasonality, and analysing the physical driving mechanisms, requires a robust definition of African precipitation seasonality, applicable to both observational datasets and model simulations. Here we present a methodology for objectively determining the onset and cessation of multiple wet seasons across the whole of Africa. Compatibility with known physical drivers of African rainfall, consistency with indigenous methods, and generally strong agreement between satellite-based rainfall data sets confirm that the method is capturing the correct seasonal progression of African rainfall. Application of this method to observational datasets reveals that over East Africa cessation of the short rains is 5 days earlier in La Nina years, and the failure of the rains and subsequent humanitarian disaster is associated with shorter as well as weaker rainy seasons over this region. The method is used to examine the representation of the seasonality of African precipitation in CMIP5 model simulations. Overall, atmosphere-only and fully coupled CMIP5 historical simulations represent essential aspects of the seasonal cycle; patterns of seasonal progression of the rainy season are captured, for the most part mean model onset/ cessation dates agree with mean observational dates to within 18 days. However, unlike the atmosphere-only simulations, the coupled simulations do not capture the biannual regime over the southern West African coastline, linked to errors in Gulf of Guinea Sea Surface Temperature. Application to both observational and climate model datasets, and
NASA Astrophysics Data System (ADS)
di Luca, Alejandro; de Elía, Ramón; Laprise, René
2012-03-01
Regional Climate Models (RCMs) constitute the most often used method to perform affordable high-resolution regional climate simulations. The key issue in the evaluation of nested regional models is to determine whether RCM simulations improve the representation of climatic statistics compared to the driving data, that is, whether RCMs add value. In this study we examine a necessary condition that some climate statistics derived from the precipitation field must satisfy in order that the RCM technique can generate some added value: we focus on whether the climate statistics of interest contain some fine spatial-scale variability that would be absent on a coarser grid. The presence and magnitude of fine-scale precipitation variance required to adequately describe a given climate statistics will then be used to quantify the potential added value (PAV) of RCMs. Our results show that the PAV of RCMs is much higher for short temporal scales (e.g., 3-hourly data) than for long temporal scales (16-day average data) due to the filtering resulting from the time-averaging process. PAV is higher in warm season compared to cold season due to the higher proportion of precipitation falling from small-scale weather systems in the warm season. In regions of complex topography, the orographic forcing induces an extra component of PAV, no matter the season or the temporal scale considered. The PAV is also estimated using high-resolution datasets based on observations allowing the evaluation of the sensitivity of changing resolution in the real climate system. The results show that RCMs tend to reproduce relatively well the PAV compared to observations although showing an overestimation of the PAV in warm season and mountainous regions.
Moritsugu, Kei; Koike, Ryotaro; Yamada, Kouki; Kato, Hiroaki; Kidera, Akinori
2015-01-01
Molecular dynamics (MD) simulations of proteins provide important information to understand their functional mechanisms, which are, however, likely to be hidden behind their complicated motions with a wide range of spatial and temporal scales. A straightforward and intuitive analysis of protein dynamics observed in MD simulation trajectories is therefore of growing significance with the large increase in both the simulation time and system size. In this study, we propose a novel description of protein motions based on the hierarchical clustering of fluctuations in the inter-atomic distances calculated from an MD trajectory, which constructs a single tree diagram, named a “Motion Tree”, to determine a set of rigid-domain pairs hierarchically along with associated inter-domain fluctuations. The method was first applied to the MD trajectory of substrate-free adenylate kinase to clarify the usefulness of the Motion Tree, which illustrated a clear-cut dynamics picture of the inter-domain motions involving the ATP/AMP lid and the core domain together with the associated amplitudes and correlations. The comparison of two Motion Trees calculated from MD simulations of ligand-free and -bound glutamine binding proteins clarified changes in inherent dynamics upon ligand binding appeared in both large domains and a small loop that stabilized ligand molecule. Another application to a huge protein, a multidrug ATP binding cassette (ABC) transporter, captured significant increases of fluctuations upon binding a drug molecule observed in both large scale inter-subunit motions and a motion localized at a transmembrane helix, which may be a trigger to the subsequent structural change from inward-open to outward-open states to transport the drug molecule. These applications demonstrated the capabilities of Motion Trees to provide an at-a-glance view of various sizes of functional motions inherent in the complicated MD trajectory. PMID:26148295
SWAT use of gridded observations for simulating runoff - a Vietnam river basin study
NASA Astrophysics Data System (ADS)
Vu, M. T.; Raghavan, S. V.; Liong, S. Y.
2011-12-01
Many research studies that focus on basin hydrology have used the SWAT model to simulate runoff. One common practice in calibrating the SWAT model is the application of station data rainfall to simulate runoff. But over regions lacking robust station data, there is a problem of applying the model to study the hydrological responses. For some countries and remote areas, the rainfall data availability might be a constraint due to many different reasons such as lacking of technology, war time and financial limitation that lead to difficulty in constructing the runoff data. To overcome such a limitation, this research study uses some of the available globally gridded high resolution precipitation datasets to simulate runoff. Five popular gridded observation precipitation datasets: (1) Asian Precipitation Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources (APHRODITE), (2) Tropical Rainfall Measuring Mission (TRMM), (3) Precipitation Estimation from Remote Sensing Information using Artificial Neural Network (PERSIANN), (4) Global Precipitation Climatology Project (GPCP), (5) modified Global Historical Climatology Network version 2 (GHCN2) and one reanalysis dataset National Centers for Environment Prediction/National Center for Atmospheric Research (NCEP/NCAR) are used to simulate runoff over the Dakbla River (a small tributary of the Mekong River) in Vietnam. Wherever possible, available station data are also used for comparison. Bilinear interpolation of these gridded datasets is used to input the precipitation data at the closest grid points to the station locations. Sensitivity Analysis and Auto-calibration are performed for the SWAT model. The Nash-Sutcliffe Efficiency (NSE) and Coefficient of Determination (R2) indices are used to benchmark the model performance. This entails a good understanding of the response of the hydrological model to different datasets and a quantification of the uncertainties in these datasets. Such a
NASA Technical Reports Server (NTRS)
2008-01-01
NASA s advanced visual simulations are essential for analyses associated with life cycle planning, design, training, testing, operations, and evaluation. Kennedy Space Center, in particular, uses simulations for ground services and space exploration planning in an effort to reduce risk and costs while improving safety and performance. However, it has been difficult to circulate and share the results of simulation tools among the field centers, and distance and travel expenses have made timely collaboration even harder. In response, NASA joined with Valador Inc. to develop the Distributed Observer Network (DON), a collaborative environment that leverages game technology to bring 3-D simulations to conventional desktop and laptop computers. DON enables teams of engineers working on design and operations to view and collaborate on 3-D representations of data generated by authoritative tools. DON takes models and telemetry from these sources and, using commercial game engine technology, displays the simulation results in a 3-D visual environment. Multiple widely dispersed users, working individually or in groups, can view and analyze simulation results on desktop and laptop computers in real time.
Initial Data Analysis Results for ATD-2 ISAS HITL Simulation
NASA Technical Reports Server (NTRS)
Lee, Hanbong
2017-01-01
To evaluate the operational procedures and information requirements for the core functional capabilities of the ATD-2 project, such as tactical surface metering tool, APREQ-CFR procedure, and data element exchanges between ramp and tower, human-in-the-loop (HITL) simulations were performed in March, 2017. This presentation shows the initial data analysis results from the HITL simulations. With respect to the different runway configurations and metering values in tactical surface scheduler, various airport performance metrics were analyzed and compared. These metrics include gate holding time, taxi-out in time, runway throughput, queue size and wait time in queue, and TMI flight compliance. In addition to the metering value, other factors affecting the airport performance in the HITL simulation, including run duration, runway changes, and TMI constraints, are also discussed.
NASA Astrophysics Data System (ADS)
Schneider, Tapio; Lan, Shiwei; Stuart, Andrew; Teixeira, João.
2017-12-01
Climate projections continue to be marred by large uncertainties, which originate in processes that need to be parameterized, such as clouds, convection, and ecosystems. But rapid progress is now within reach. New computational tools and methods from data assimilation and machine learning make it possible to integrate global observations and local high-resolution simulations in an Earth system model (ESM) that systematically learns from both and quantifies uncertainties. Here we propose a blueprint for such an ESM. We outline how parameterization schemes can learn from global observations and targeted high-resolution simulations, for example, of clouds and convection, through matching low-order statistics between ESMs, observations, and high-resolution simulations. We illustrate learning algorithms for ESMs with a simple dynamical system that shares characteristics of the climate system; and we discuss the opportunities the proposed framework presents and the challenges that remain to realize it.
NASA Astrophysics Data System (ADS)
Stanfield, R. E.; Dong, X.; Xi, B.; Kennedy, A. D.; Del Genio, A. D.; Minnis, P.; Loeb, N. G.; Doelling, D.
2013-05-01
Marine Boundary Layer (MBL) Clouds are an extremely important part of the climate system. Their treatment in climate models is a large source of uncertainty that will harm future projection of the Earth's climate. Zhang et al. (2005, CMIP3) compared the GCMs simulated cloud fractions (CF) with NASA CERES and ISCCP results and found that most GCMs underestimated mid-latitude MBL clouds but overestimated their optical depth. The underestimated CF and overestimated cloud optical thickness in the models offset each other when calculating TOA radiation budgets. Recent studies (Jiang et al. 2012; Stanfield et al. 2013; and Dolinar et al. 2013) have found there has not been much improvement from CMIP3 to CMIP5 for MBL clouds. Most GCMs still simulate fewer mid-latitude MBL clouds. In this study, we compare the NASA GISS CMIP5 and Post-CMIP5 results with NASA CERES cloud properties (SYN1deg) and TOA radiation budgets (EBAF), as well as CloudSat-CALIPSO cloud products. Special attention has been paid over the Southern mid-latitudes (~ 30-60 °S) where the total cloud fractions can reach up to 80-90% with MBL clouds being the dominant cloud type. Comparisons have shown that the globally averaged total CFs and TOA radiation budgets from CMIP5 agreed well with satellite observations, however, there are significant regional differences. For example, most CMIP5 models underestimated MBL clouds over the Southern mid-latitudes, including the GISS GCM, resulting in less reflected (or more absorbed) shortwave flux at TOA. The preliminary results from NASA GISS post-CMIP5 have made many improvements, and agree much better with satellite observations. These improvements are attributed to a new PBL parameterization, where more/less clouds can be simulated when the PBL gets deeper/shallower. This update has a large effect on radiation and clouds.
Influence of photon energy cuts on PET Monte Carlo simulation results.
Mitev, Krasimir; Gerganov, Georgi; Kirov, Assen S; Schmidtlein, C Ross; Madzhunkov, Yordan; Kawrakow, Iwan
2012-07-01
The purpose of this work is to study the influence of photon energy cuts on the results of positron emission tomography (PET) Monte Carlo (MC) simulations. MC simulations of PET scans of a box phantom and the NEMA image quality phantom are performed for 32 photon energy cut values in the interval 0.3-350 keV using a well-validated numerical model of a PET scanner. The simulations are performed with two MC codes, egs_pet and GEANT4 Application for Tomographic Emission (GATE). The effect of photon energy cuts on the recorded number of singles, primary, scattered, random, and total coincidences as well as on the simulation time and noise-equivalent count rate is evaluated by comparing the results for higher cuts to those for 1 keV cut. To evaluate the effect of cuts on the quality of reconstructed images, MC generated sinograms of PET scans of the NEMA image quality phantom are reconstructed with iterative statistical reconstruction. The effects of photon cuts on the contrast recovery coefficients and on the comparison of images by means of commonly used similarity measures are studied. For the scanner investigated in this study, which uses bismuth germanate crystals, the transport of Bi X(K) rays must be simulated in order to obtain unbiased estimates for the number of singles, true, scattered, and random coincidences as well as for an unbiased estimate of the noise-equivalent count rate. Photon energy cuts higher than 170 keV lead to absorption of Compton scattered photons and strongly increase the number of recorded coincidences of all types and the noise-equivalent count rate. The effect of photon cuts on the reconstructed images and the similarity measures used for their comparison is statistically significant for very high cuts (e.g., 350 keV). The simulation time decreases slowly with the increase of the photon cut. The simulation of the transport of characteristic x rays plays an important role, if an accurate modeling of a PET scanner system is to be achieved
Observing Convective Aggregation
NASA Astrophysics Data System (ADS)
Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita
2017-11-01
Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.
NASA Technical Reports Server (NTRS)
D’Alessandro, John J.; Diao, Minghui; Wu, Chenglai; Liu, Xiaohong; Chen, Ming; Morrison, Hugh; Eidhammer, Trude; Jensen, Jorgen B.; Bansemer, Aaron; Zondlo, Mark A.;
2017-01-01
Occurrence frequency and dynamical conditions of ice supersaturation (ISS, where relative humidity with respect to ice (RHi) greater than 100%) are examined in the upper troposphere around convective activity. Comparisons are conducted between in situ airborne observations and the Weather Research and Forecasting model simulations using four double-moment microphysical schemes at temperatures less than or or equal to -40degdegC. All four schemes capture both clear-sky and in-cloud ISS conditions. However, the clear-sky (in-cloud) ISS conditions are completely (significantly) limited to the RHi thresholds of the Cooper parameterization. In all of the simulations, ISS occurrence frequencies are higher by approximately 3-4 orders of magnitude at higher updraft speeds (greater than 1 m s(exp -1) than those at the lower updraft speeds when ice water content (IWC) greater than 0.01 gm(exp -3), while observations show smaller differences up to approximately 1-2 orders of magnitude. The simulated ISS also occurs less frequently at weaker updrafts and downdrafts than observed. These results indicate that the simulations have a greater dependence on stronger updrafts to maintain/generate ISS at higher IWC. At lower IWC (less than or equal or 0.01 gm(exp -3), simulations unexpectedly show lower ISS frequencies at stronger updrafts. Overall, the Thompson aerosol-aware scheme has the closest magnitudes and frequencies of ISS greater than 20% to the observations, and the modified Morrison has the closest correlations between ISS frequencies and vertical velocity at higher IWC and number density. The Cooper parameterization often generates excessive ice crystals and therefore suppresses the frequency and magnitude of ISS, indicating that it should be initiated at higher ISS (e.g.,lees than or equal to 25%).
Simulation of Twin Telescopes at Onsala and Wettzell for the VLBI Global Observing System
NASA Astrophysics Data System (ADS)
Schönberger, Caroline; Gnilsen, Paul; Böhm, Johannes; Haas, Rüdiger
2015-04-01
The VLBI2010 committee of the International VLBI Service for Geodesy and Astrometry (IVS) developed a concept to achieve an improvement of the accuracy of geodetic Very Long Baseline Interferometry (VLBI) to 1 mm for station positions and 0.1 mm/yr for station velocities. This so-called VLBI2010 concept includes broadband observations with fast slewing telescopes and proposes twin telescopes to improve the handling of atmospheric turbulence that has been identified as a limiting factor for geodetic VLBI. There are several VLBI sites that have projects to install a Twin Telescope. The Wettzell Twin Telescope in Germany has already been constructed, and Twin Telescopes will be installed in the coming years at Onsala (Sweden), Ny-Ålesund (Spitsbergen, Norway) and Kazan (Russia). In this study, the Vienna VLBI Software (VieVS) is used to schedule and simulate a global VLBI network following the example of the CONT11 campaign, with and without the Twin Telescopes in Onsala and Wettzell. Different scheduling approaches (e.g., source-based scheduling, Twin Telescope observing in multidirectional mode, Twin Telescopes in continuous mode) were compared by evaluating the numbers of observations and scans as well as baseline length repeatabilities, station positions, Earth orientation parameters, atmospheric parameters and clock estimates. Comparison of the results show an improvement in estimated parameters with Twin Telescopes, especially with the Onsala Twin Telescope in a continuous observing mode and a strategy with four sources observed simultaneously.
Observing gas in Cosmic Web filaments to constrain simulations of cosmic structure formation
NASA Astrophysics Data System (ADS)
Wakker, Bart
2016-10-01
Cosmological simulations predict that dark matter and baryons condense into multi-Mpc filamentary structures, making up the Cosmic Web. This is outlined by dark matter halos, inside which 10% of baryons are concentrated to make stars in galaxies. The other 90% of the baryons remain gaseous, with about half located outside galaxy halos. They can be traced by Lyman alpha absorbers, whose HI column density is determined by a combination of gas density and the intensity of the extragalactic ionizing background (EGB). About 1000 HST orbits have been expended to map the 50% of baryons in galaxy halos. This contrasts with 37 orbits explicitly allocated to map the other 50% (our Cycle 18 program to observe 17 AGN projected onto a single filament at cz 3500 km/s). We propose a 68-orbit program to observe 40 AGN, creating a sample of 56 sightlines covering a second filament at cz 2500 km/s. Using this dataset we will do the following: (1) measure the intensity of the EGB to within about 50%; (2) confirm that the linewidth of Lya absorbers increases near the filament axis, suggesting increasing temperature or turbulence; (3) check our earlier finding that simulations predict a transverse density HI profile (which scales with the dark-matter profile) that is much broader than is indicated by the observations.
Results of intravehicular manned cargo-transfer studies in simulated weightlessness
NASA Technical Reports Server (NTRS)
Spady, A. A., Jr.; Beasley, G. P.; Yenni, K. R.; Eisele, D. F.
1972-01-01
A parametric investigation was conducted in a water immersion simulator to determine the effect of package mass, moment of inertia, and size on the ability of man to transfer cargo in simulated weightlessness. Results from this study indicate that packages with masses of at least 744 kg and moments of inertia of at least 386 kg-m2 can be manually handled and transferred satisfactorily under intravehicular conditions using either one- or two-rail motion aids. Data leading to the conclusions and discussions of test procedures and equipment are presented.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Richards, H.L.; Sides, S.W.; Novotny, M.A.
1996-12-31
Recently experimental techniques, such as magnetic force microscopy (MFM), have enabled the magnetic state of individual sub-micron particles to be resolved. Motivated by these experimental developments, the authors use Monte Carlo simulations of two-dimensional kinetic Ising ferromagnets to study the magnetic relaxation in a negative applied field of a grain with an initial magnetization m{sub 0} = + 1. They use classical droplet theory to predict the functional forms for some quantities which can be observed by MFM. An example is the probability that the magnetization is positive, which is a function of time, field, grain size, and grain dimensionality.more » The qualitative agreement between experiments and their simulations of switching in individual single-domain ferromagnets indicates that the switching mechanism in such particles may involve local nucleation and subsequent growth of droplets of the stable phase.« less
Endo, Satoshi; Fridlind, Ann M.; Lin, Wuyin; ...
2015-06-19
A 60-hour case study of continental boundary layer cumulus clouds is examined using two large-eddy simulation (LES) models. The case is based on observations obtained during the RACORO Campaign (Routine Atmospheric Radiation Measurement [ARM] Aerial Facility [AAF] Clouds with Low Optical Water Depths [CLOWD] Optical Radiative Observations) at the ARM Climate Research Facility's Southern Great Plains site. The LES models are driven by continuous large-scale and surface forcings, and are constrained by multi-modal and temporally varying aerosol number size distribution profiles derived from aircraft observations. We compare simulated cloud macrophysical and microphysical properties with ground-based remote sensing and aircraft observations.more » The LES simulations capture the observed transitions of the evolving cumulus-topped boundary layers during the three daytime periods, and generally reproduce variations of droplet number concentration with liquid water content (LWC), corresponding to the gradient between the cloud centers and cloud edges at given heights. The observed LWC values fall within the range of simulated values; the observed droplet number concentrations are commonly higher than simulated, but differences remain on par with potential estimation errors in the aircraft measurements. Sensitivity studies examine the influences of bin microphysics versus bulk microphysics, aerosol advection, supersaturation treatment, and aerosol hygroscopicity. Simulated macrophysical cloud properties are found to be insensitive in this non-precipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity.« less
NASA Astrophysics Data System (ADS)
Stanfield, R.; Dong, X.; Xi, B.; Kennedy, A. D.; Del Genio, A. D.; Minnis, P.; Jiang, J. H.
2013-12-01
Recent changes to boundary layer turbulence and convection parameterizations of the NASA GISS E2 GCM have led to drastic improvements in the newest Post-CMIP5 (P5) model simulations. A study has been performed to evaluate these changes. Variables including Cloud Fraction (CF), Liquid Water Path (LWP), Ice Water Path (IWP), Cloud Water Path (LWP+IWP, CWP), Precipitable Water Vapor (PWV), and Relative Humidity (RH), from P5 and its CMIP5 (C5) predecessor have been compared to multiple satellite observations including CERES-MODIS (CM), CloudSat/CALIPSO (CC), AIRS, and AMSR-E. P5 simulations show drastic improvements for regional CFs, resulting in better correlations with observations. The largest improvements were found over the Southern Mid-Latitudes (SMLs), where newly implemented changes to the boundary layer turbulence parameterization increased low-level CF by ~20% while generating less optically thick clouds. The double InterTropical Convergence Zone (ITCZ) issue that plagues many GCMs, including previous GISS C5 simulations, is also removed with the new changes to convection parameterizations when decoupled from the ocean. P5 simulations show a decrease in global CWP, more closely resembling CC and CM observations. Globally, P5 simulated PWV is in better agreement with AMSR-R and AIRS, particularly over the SML oceans. RH comparisons show improvement when compared with AIRS. Spatial and variability analyses using Taylor diagrams indicate overall better correlations and smaller standard deviations in PWV and RH comparisons between P5/C5 simulations and AMSR-R/AIRS observations than CF and CWP/LWP/IWP comparisons.
NASA Astrophysics Data System (ADS)
Garg, P.; Nesbitt, S. W.; Lang, T. J.; Chronis, T.; Thayer, J. D.; Hence, D. A.
2017-12-01
Cold pools generated in the wake of convective activity can enhance the surface sensible heat flux, latent heat flux, and also changes in evaporation out of, and fresh water flux into, the ocean. Recent studies have shown that over the open ocean, cold pool outflow boundaries and their intersections can organize and initiate a spectrum of deep convective clouds, which is a key driver of shallow and deep convection over conditionally-unstable tropical oceans. The primary goal of this study is to understand the structure and characteristics of cold pools over the tropical oceans using observations. With the idea that cold pools will have strong wind gradients at their boundaries, we use ASCAT vector wind retrievals. We identify regions of steep gradients in wind vectors as gradient features (GFs), akin to cold pools. Corresponding to these GFs, sensible and latent heat fluxes were calculated using the observed winds and background temperatures from MERRA-2 reanalysis. To evaluate the proposed technique, cold pools were observed using S-PolKa radar from the DYNAMO/AMIE field campaign in the Indian Ocean for the period of 1 October 2011 to 31 March 2012 and were compared with ASCAT GFs. To relate the thermodynamic and kinematic characteristics of observed and simulated cold pools, simulations were carried out on WRF on a 3-km domain explicitly. The areas of cold pools were identified in the models using virtual temperature (Tv), which is a direct measure of air density, while GFs were identified using model simulated winds. Quantitative measures indicate that GFs are highly correspondent with model-simulated cold pools. In global measurements of cold pools from 2007-2015, it is possible to examine the characteristics of GFs across all tropical ocean basins, and relate them to meteorological conditions, as well as the characteristics of the parent precipitation systems. Our results indicate that while there is a general relationship between the amount of precipitation
NASA Astrophysics Data System (ADS)
Veneziani, C.; Kurtakoti, P. K.; Weijer, W.; Stoessel, A.
2016-12-01
In contrast to their better known coastal counterpart, open ocean polynyas (OOPs) form through complex driving mechanisms, involving pre-conditioning of the water column, external forcing and internal ocean dynamics, and are therefore much more elusive and less predictable than coastal polynyas. Yet, their impact on bottom water formation and the Meridional Overturning Circulation could prove substantial. Here, we characterize the formation of Southern Ocean OOPs by analyzing the full satellite NASA microwave imager and radiometer (SSMI/SMMR) data record from 1972 to present day. We repeat the same analysis within the low-resolution (LR) and high-resolution (HR) fully-coupled Earth System Model simulations that are part of the Accelerated Climate Model for Energy (ACME) v0 baseline experiments. The focus is on two OOPs that are more consistently seen in observations: the Maud Rise and the Weddell Sea polynyas. Results show that the LR simulation is unable to reproduce any OOP over the 195 years of its duration, while both Maud Rise and Weddell Sea polynyas are seen in the HR simulation, with extents similar to observations'. We explore possible mechanisms that would explain the asymmetric behavior, including topographic processes, eddy shedding events, and different water column stratification between the two simulations.
Vibronic coupling simulations for linear and nonlinear optical processes: Simulation results
NASA Astrophysics Data System (ADS)
Silverstein, Daniel W.; Jensen, Lasse
2012-02-01
A vibronic coupling model based on time-dependent wavepacket approach is applied to simulate linear optical processes, such as one-photon absorbance and resonance Raman scattering, and nonlinear optical processes, such as two-photon absorbance and resonance hyper-Raman scattering, on a series of small molecules. Simulations employing both the long-range corrected approach in density functional theory and coupled cluster are compared and also examined based on available experimental data. Although many of the small molecules are prone to anharmonicity in their potential energy surfaces, the harmonic approach performs adequately. A detailed discussion of the non-Condon effects is illustrated by the molecules presented in this work. Linear and nonlinear Raman scattering simulations allow for the quantification of interference between the Franck-Condon and Herzberg-Teller terms for different molecules.
NASA Astrophysics Data System (ADS)
Feng, Z.; Ma, P. L.; Hardin, J. C.; Houze, R.
2017-12-01
Mesoscale convective systems (MCSs) are the largest type of convective storms that develop when convection aggregates and induces mesoscale circulation features. Over North America, MCSs contribute over 60% of the total warm-season precipitation and over half of the extreme daily precipitation in the central U.S. Our recent study (Feng et al. 2016) found that the observed increases in springtime total and extreme rainfall in this region are dominated by increased frequency and intensity of long-lived MCSs*. To date, global climate models typically do not run at a resolution high enough to explicitly simulate individual convective elements and may not have adequate process representations for MCSs, resulting in a large deficiency in projecting changes of the frequency of extreme precipitation events in future climate. In this study, we developed a novel observation-guided approach specifically designed to evaluate simulated MCSs in the Department of Energy's climate model, Accelerated Climate Modeling for Energy (ACME). The ACME model has advanced treatments for convection and subgrid variability and for this study is run at 25 km and 100 km grid spacings. We constructed a robust MCS database consisting of over 500 MCSs from 3 warm-season observations by applying a feature-tracking algorithm to 4-km resolution merged geostationary satellite and 3-D NEXRAD radar network data over the Continental US. This high-resolution MCS database is then down-sampled to the 25 and 100 km ACME grids to re-characterize key MCS properties. The feature-tracking algorithm is adapted with the adjusted characteristics to identify MCSs from ACME model simulations. We demonstrate that this new analysis framework is useful for evaluating ACME's warm-season precipitation statistics associated with MCSs, and provides insights into the model process representations related to extreme precipitation events for future improvement. *Feng, Z., L. R. Leung, S. Hagos, R. A. Houze, C. D. Burleyson
Keating, Elizabeth H.; Hakala, J. Alexandra; Viswanathan, Hari; ...
2013-03-01
It is challenging to predict the degree to which shallow groundwater might be affected by leaks from a CO 2 sequestration reservoir, particularly over long time scales and large spatial scales. In this study observations at a CO 2 enriched shallow aquifer natural analog were used to develop a predictive model which is then used to simulate leakage scenarios. This natural analog provides the opportunity to make direct field observations of groundwater chemistry in the presence of elevated CO 2, to collect aquifer samples and expose them to CO 2 under controlled conditions in the laboratory, and to test themore » ability of multiphase reactive transport models to reproduce measured geochemical trends at the field-scale. The field observations suggest that brackish water entrained with the upwelling CO 2 are a more significant source of trace metals than in situ mobilization of metals due to exposure to CO 2. The study focuses on a single trace metal of concern at this site: U. Experimental results indicate that cation exchange/adsorption and dissolution/precipitation of calcite containing trace amounts of U are important reactions controlling U in groundwater at this site, and that the amount of U associated with calcite is fairly well constrained. Simulations incorporating these results into a 3-D multi-phase reactive transport model are able to reproduce the measured ranges and trends between pH, pCO 2, Ca, total C, U and Cl -at the field site. Although the true fluxes at the natural analog site are unknown, the cumulative CO 2 flux inferred from these simulations are approximately equivalent to 37.8E-3 MT, approximately corresponding to a .001% leak rate for injection at a large (750 MW) power plant. The leakage scenario simulations suggest that if the leak only persists for a short time the volume of aquifer contaminated by CO 2-induced mobilization of U will be relatively small, yet persistent over 100 a.« less
Binary Black Hole Late Inspiral: Simulations for Gravitational Wave Observations
NASA Technical Reports Server (NTRS)
Baker, John G.; vanMeter, James R.; Centrella, Joan; Choi, Dae-Il; Kelly, Bernard J.; Koppitz, Michael
2006-01-01
Coalescing binary black hole mergers are expected to be the strongest gravitational wave sources for ground-based interferometers, such as the LIGO, VIRGO, and GEO600, as well as the spacebased interferometer LISA. Until recently it has been impossible to reliably derive the predictions of General Relativity for the final merger stage, which takes place in the strong-field regime. Recent progress in numerical relativity simulations is, however, revolutionizing our understanding of these systems. We examine here the specific case of merging equal-mass Schwarzschild black holes in detail, presenting new simulations in which the black holes start in the late inspiral stage on orbits with very low eccentricity and evolve for approximately 1200M through approximately 7 orbits before merging. We study the accuracy and consistency of our simulations and the resulting gravitational waveforms, which encompass approximately 14 cycles before merger, and highlight the importance of using frequency (rather than time) to set the physical reference when comparing models. Matching our results to PN calculations for the earlier parts of the inspiral provides a combined waveform with less than half a cycle of accumulated phase error through the entire coalescence. Using this waveform, we calculate signal-to-noise ratios (SNRs) for iLIGO, adLIGO, and LISA, highlighting the contributions from the late-inspiral and merger-ringdown parts of the waveform which can now be simulated numerically. Contour plots of SNR as a function of z and M show that adLIGO can achieve SNR 2 10 for some IMBBHs out to z approximately equals 1, and that LISA can see MBBHs in the range 3 x 10(exp 4) approximately < M/Mo approximately < 10(exp 7) at SNR > 100 out to the earliest epochs of structure formation at z > 15.
A simulated observation database to assess the impact of the IASI-NG hyperspectral infrared sounder
NASA Astrophysics Data System (ADS)
Andrey-Andrés, Javier; Fourrié, Nadia; Guidard, Vincent; Armante, Raymond; Brunel, Pascal; Crevoisier, Cyril; Tournier, Bernard
2018-02-01
The highly accurate measurements of the hyperspectral Infrared Atmospheric Sounding Interferometer (IASI) are used in numerical weather prediction (NWP), atmospheric chemistry and climate monitoring. As the second generation of the European Polar System (EPS-SG) is being developed, a new generation of IASI instruments has been designed to fly on board the MetOp-SG constellation: IASI New Generation (IASI-NG). In order to prepare the arrival of this new instrument, and to evaluate its impact on NWP and atmospheric chemistry applications, a set of IASI and IASI-NG simulated data was built and made available to the public to set a common framework for future impact studies. This paper describes the information available in this database and the procedure followed to run the IASI and IASI-NG simulations. These simulated data were evaluated by comparing IASI-NG to IASI observations. The result is also presented here. Additionally, preliminary impact studies of the benefit of IASI-NG compared to IASI on the retrieval of temperature and humidity in a NWP framework are also shown in the present work. With a channel dataset located in the same wave numbers for both instruments, we showed an improvement of the temperature retrievals throughout the atmosphere, with a maximum in the troposphere with IASI-NG and a lower benefit for the tropospheric humidity.
NASA Astrophysics Data System (ADS)
Mooers, Christopher N. K.; Bang, Inkweon; Sandoval, Francisco J.
2005-06-01
The Princeton Ocean Model (POM), as implemented for the Japan (East) Sea (JES) with mesoscale-admitting resolution is driven by seasonal throughflow and synoptic atmospheric forcing for 1999 through 2001. Temperature and salinity profiles from shipborne and PALACE float CTDs, and horizontal velocities at 800 m from PALACE float trajectories, plus horizontal velocities at 15 m from WOCE surface drifters for 1988 through 2001, are used to assess the performance of the numerical simulations for a base case. General agreement exists in the circulation at 15 and 800 m and the horizontal and vertical structure of the upper ocean temperature and salinity fields. The mean observed flow at 15 m defines the two branches of the Tsushima Warm Current and hints at the existence of a large cyclonic gyre over the Japan Basin, which the simulations also produce. The mean observed flow at 800 m defines a large cyclonic recirculation gyre over the Japan Basin that validates the simulated flow pattern. Variances of the observed and simulated flows at 15 and 800 m have similar patterns. The main discrepancies are associated with the strength of the seasonal thermocline and halocline and the location of the Subpolar Front. When smoother topography and smaller lateral friction are used in other cases, the thermocline and halocline strengthen, agreeing better with the observed values, and when 80% of total outflow transport is forced to exit through Soya Strait, the Subpolar Front extends along the coast to the north of Tsugaru Strait, which is an observed feature absent in the base case.
Janssens, Sarah; Beckmann, Michael; Bonney, Donna
2015-08-01
Simulation training in laparoscopic surgery has been shown to improve surgical performance. To describe the implementation of a laparoscopic simulation training and credentialing program for gynaecology registrars. A pilot program consisting of protected, supervised laparoscopic simulation time, a tailored curriculum and a credentialing process, was developed and implemented. Quantitative measures assessing simulated surgical performance were measured over the simulation training period. Laparoscopic procedures requiring credentialing were assessed for both the frequency of a registrar being the primary operator and the duration of surgery and compared to a presimulation cohort. Qualitative measures regarding quality of surgical training were assessed pre- and postsimulation. Improvements were seen in simulated surgical performance in efficiency domains. Operative time for procedures requiring credentialing was reduced by 12%. Primary operator status in the operating theatre for registrars was unchanged. Registrar assessment of training quality improved. The introduction of a laparoscopic simulation training and credentialing program resulted in improvements in simulated performance, reduced operative time and improved registrar assessment of the quality of training. © 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
Hydrodynamic cavitation in microsystems. II. Simulations and optical observations
NASA Astrophysics Data System (ADS)
Medrano, M.; Pellone, C.; Zermatten, P. J.; Ayela, F.
2012-04-01
Numerical calculations in the single liquid phase and optical observations in the two-phase cavitating flow regime have been performed on microdiaphragms and microventuris fed with deionized water. Simulations have confirmed the influence of the shape of the shrinkage upon the contraction of the jet, and so on the localisation of possible cavitating area downstream. Observations of cavitating flow patterns through hybrid silicon-pyrex microdevices have been performed either via a laser excitation with a pulse duration of 6 ns, or with the help of a high-speed camera. Recorded snapshots and movies are presented. Concerning microdiaphragms, it is confirmed that very high shear rates downstream the diaphragms are the cause of bubbly flows. Concerning microventuris, a gaseous cavity forms on a boundary downstream the throat. As a consequence of a microsystem instability, the cavity displays a high frequency pulsation. Low values Strouhal numbers are associated to such a sheet cavitation. Moreover, when the intensity of the cavitating flow is reduced, there is a mismatch between the frequency of the pulsation of the cavity and the frequency of shedded clouds downstream the channel. That may be the consequence of viscous effects limiting the impingement of a re-entrant liquid jet on the attached cavity.
NASA Astrophysics Data System (ADS)
Wu, Chenglai; Liu, Xiaohong; Diao, Minghui; Zhang, Kai; Gettelman, Andrew; Lu, Zheng; Penner, Joyce E.; Lin, Zhaohui
2017-04-01
In this study we evaluate cloud properties simulated by the Community Atmosphere Model version 5 (CAM5) using in situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) campaign for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes and even higher (94.3 %) for ice clouds (T ≤ -40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 µm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model.
NASA Astrophysics Data System (ADS)
Zhang, Y.; Yang, W.; Zhang, R.; Zhang, Z.; Lyu, S.; Yu, J.; Wang, Y.; Wang, G.; Wang, X.
2017-12-01
Isoprene, the most abundant non-methane hydrocarbon emitted from plants, directly and indirectly affects atmospheric photochemistry and radiative forcing, yet narrowing its emission uncertainties is a continuous challenge. Comparison of observed and modelled isoprene on large spatiotemporal scales would help recognize factors that control isoprene variability, systematic field observation data are however quite lacking. Here we collected ambient air samples with 1 L silonite-treated stainless steel canisters simultaneously at 20 sites over China on every Wednesday at approximately 14:00 pm Beijing time from 2012 to 2014, and analyzed isoprene mixing ratios by preconcentrator-GC-MSD/FID. Observed isoprene mixing ratios were also compared with that simulated by coupling MEGAN 2.0 (Guenther et al., 2006) with a 3-D Regional chEmical trAnsport Model (REAM) (Zhang et al., 2017). Similar seasonal variations between observation and model simulation were obtained for most of sampling sites, but overall the average isoprene mixing ratios during growing months (May to October) was 0.37 ± 0.08 ppbv from model simulation, about 32% lower than that of 0.54 ± 0.20 ppbv based on ground-based observation, and this discrepancy was particularly significant in north China during wintertime. Further investigation demonstrated that emission of biogenic isoprene in northwest China might be underestimated and non-biogenic emission, such burning biomass/biofuel, might contribute to the elevated levels of isoprene during winter time. The observation-based empirical formulas for changing isoprene emission with solar radiation and temperature were also derived for different regions of China.
NASA Astrophysics Data System (ADS)
Jia, T.; Liang, J. J.; Li, X.-M.; Sha, J.
2018-01-01
The refraction and reconnection of internal solitary waves (ISWs) around the Dongsha Atoll (DSA) in the northern South China Sea (SCS) are investigated based on spaceborne synthetic aperture radar (SAR) observations and numerical simulations. In general, a long ISW front propagating from the deep basin of the northern SCS splits into northern and southern branches when it passes the DSA. In this study, the statistics of Envisat Advanced SAR (ASAR) images show that the northern and southern wave branches can reconnect behind the DSA, but the reconnection location varies. A previously developed nonlinear refraction model is set up to simulate the refraction and reconnection of the ISWs behind the DSA, and the model is used to evaluate the effects of ocean stratification, background currents, and incoming ISW characteristics at the DSA on the variation in reconnection locations. The results of the first realistic simulation agree with consecutive TerraSAR-X (TSX) images captured within 12 h of each other. Further sensitivity simulations show that ocean stratification, background currents, and initial wave amplitudes all affect the phase speeds of wave branches and therefore shift their reconnection locations while shapes and locations of incoming wave branches upstream of the DSA profoundly influence the subsequent propagation paths. This study clarifies the variation in reconnection locations of ISWs downstream of the DSA and reveals the important mechanisms governing the reconnection process, which can improve our understanding of the propagation of ISWs near the DSA.
Xiong, Kan; Zwier, Matthew C.; Myshakina, Nataliya S.; Burger, Virginia M.; Asher, Sanford A.; Chong, Lillian T.
2011-01-01
We report the first experimental measurements of Ramachandran Ψ-angle distributions for intrinsically disordered peptides: the N-terminal peptide fragment of tumor suppressor p53 and its P27 mutant form. To provide atomically detailed views of the conformational distributions, we performed classical, explicit-solvent molecular dynamics simulations on the microsecond timescale. Upon binding its partner protein, MDM2, wild-type p53 peptide adopts an α-helical conformation. Mutation of Pro27 to serine results in the highest affinity yet observed for MDM2-binding of the p53 peptide. Both UV resonance Raman spectroscopy (UVRR) and simulations reveal that the P27S mutation decreases the extent of PPII helical content and increases the probability for conformations that are similar to the α-helical MDM2-bound conformation. In addition, UVRR measurements were performed on peptides that were isotopically labeled at the Leu26 residue preceding the Pro27 in order to determine the conformational distributions of Leu26 in the wild-type and mutant peptides. The UVRR and simulation results are in quantitative agreement in terms of the change in the population of non-PPII conformations involving Leu26 upon mutation of Pro27 to serine. Finally, our simulations reveal that the MDM2-bound conformation of the peptide is significantly populated in both the wild-type and mutant isolated peptide ensembles in their unbound states, suggesting that MDM2 binding of the p53 peptides may involve conformational selection. PMID:21528875
NASA Astrophysics Data System (ADS)
Kim, H.; Meneghini, R.; Jones, J.; Liao, L.
2011-12-01
A comprehensive space-borne radar simulator has been developed to support active microwave sensor satellite missions. The two major objectives of this study are: 1) to develop a radar simulator optimized for the Dual-frequency Precipitation Radar (KuPR and KaPR) on the Global Precipitation Measurement Mission satellite (GPM-DPR) and 2) to generate the synthetic test datasets for DPR algorithm development. This simulator consists of two modules: a DPR scanning configuration module and a forward module that generates atmospheric and surface radar observations. To generate realistic DPR test data, the scanning configuration module specifies the technical characteristics of DPR sensor and emulates the scanning geometry of the DPR with a inner swath of about 120 km, which contains matched-beam data from both frequencies, and an outer swath from 120 to 245 km over which only Ku-band data will be acquired. The second module is a forward model used to compute radar observables (reflectivity, attenuation and polarimetric variables) from input model variables including temperature, pressure and water content (rain water, cloud water, cloud ice, snow, graupel and water vapor) over the radar resolution volume. Presently, the input data to the simulator come from the Goddard Cumulus Ensemble (GCE) and Weather Research and Forecast (WRF) models where a constant mass density is assumed for each species with a particle size distribution given by an exponential distribution with fixed intercept parameter (N0) and a slope parameter (Λ) determined from the equivalent water content. Although the model data do not presently contain mixed phase hydrometeors, the Yokoyama-Tanaka melting model is used along with the Bruggeman effective dielectric constant to replace rain and snow particles, where both are present, with mixed phase particles while preserving the snow/water fraction. For testing one of the DPR retrieval algorithms, the Surface Reference Technique (SRT), the simulator uses
NASA Astrophysics Data System (ADS)
Tremblin, P.; Minier, V.; Schneider, N.; Audit, E.; Hill, T.; Didelon, P.; Peretto, N.; Arzoumanian, D.; Motte, F.; Zavagno, A.; Bontemps, S.; Anderson, L. D.; André, Ph.; Bernard, J. P.; Csengeri, T.; Di Francesco, J.; Elia, D.; Hennemann, M.; Könyves, V.; Marston, A. P.; Nguyen Luong, Q.; Rivera-Ingraham, A.; Roussel, H.; Sousbie, T.; Spinoglio, L.; White, G. J.; Williams, J.
2013-12-01
Context. Herschel far-infrared imaging observations have revealed the density structure of the interface between H ii regions and molecular clouds in great detail. In particular, pillars and globules are present in many high-mass star-forming regions, such as the Eagle nebula (M 16) and the Rosette molecular cloud, and understanding their origin will help characterize triggered star formation. Aims: The formation mechanisms of these structures are still being debated. The initial morphology of the molecular cloud and its turbulent state are key parameters since they generate deformations and curvatures of the shell during the expansion of the H ii region. Recent numerical simulations have shown how pillars can arise from the collapse of the shell in on itself and how globules can be formed from the interplay of the turbulent molecular cloud and the ionization from massive stars. The goal here is to test this scenario through recent observations of two massive star-forming regions, M 16 and the Rosette molecular cloud. Methods: First, the column density structure of the interface between molecular clouds and associated H ii regions was characterized using column density maps obtained from far-infrared imaging of the Herschel HOBYS key programme. Then, the DisPerSe algorithm was used on these maps to detect the compressed layers around the ionized gas and pillars in different evolutionary states. Column density profiles were constructed. Finally, their velocity structure was investigated using CO data, and all observational signatures were tested against some distinct diagnostics established from simulations. Results: The column density profiles have revealed the importance of compression at the edge of the ionized gas. The velocity properties of the structures, i.e. pillars and globules, are very close to what we predict from the numerical simulations. We have identified a good candidate of a nascent pillar in the Rosette molecular cloud that presents the velocity
Rubbi, Ivan; Ferri, Paola; Andreina, Giulia; Cremonini, Valeria
2016-01-01
Simulation in the context of the educational workshop is becoming an important learning method, as it allows to play realistic clinical-care situations. These vocational training activities promote the development of cognitive, affective and psychomotor skills in a pedagogical context safe and risk-free, but need to be accounted for using by valid and reliable instruments. To inspect the level of satisfaction of the students of a Degree in Nursing in northern Italy about static and high-fidelity exercises with simulators and clinical cases. A prospective observational study has been conducted involving a non-probabili- stic sample of 51 third-year students throughout the academic year 2013/14. The data collection instrument consists of three questionnaires Student Satisfaction and Self-confidence in Learning Scale, Educational Practices Questionnaire, Simulation Design Scale and 3 questions on overall satisfaction. Statistical analysis was performed with SPSS 20.0 and Office 2003 Excel. The response rate of 89.5% is obtained. The Cronbach Alfa showed a good internal reliability (α = .982). The students were generally satisfied with the activities carried out in the teaching laboratory, showing more enthusiasm for the simulation with static mannequins (71%) and with high-fidelity simulators (60%), activities for which they have experienced a significant involvement and active learning. The teaching with clinical cases scored a lesser degree of satisfaction (38%) and for this method it was found the largest number of elements of weakness.
NASA Astrophysics Data System (ADS)
Olmos, L.; Bouvard, D.; Martin, C. L.; Bellet, D.; Di Michiel, M.
2009-06-01
The sintering of both a powder with a wide particle size distribution (0-63 μm) and of a powder with artificially created pores is investigated by coupling in situ X-ray microtomography observations with Discrete Element simulations. The micro structure evolution of the copper particles is observed by microtomography all along a typical sintering cycle at 1050° C at the European Synchrotron Research Facilities (ESRF, Grenoble, France). A quantitative analysis of the 3D images provides original data on interparticle indentation, coordination and particle displacements throughout sintering. In parallel, the sintering of similar powder systems has been simulated with a discrete element code which incorporates appropriate sintering contact laws from the literature. The initial numerical packing is generated directly from the 3D microtomography images or alternatively from a random set of particles with the same size distribution. The comparison between the information drawn from the simulations and the one obtained by tomography leads to the conclusion that the first method is not satisfactory because real particles are not perfectly spherical as the numerical ones. On the opposite the packings built with the second method show sintering behaviors close to the behaviors of real materials, although particle rearrangement is underestimated by DEM simulations.
NASA Technical Reports Server (NTRS)
Young, Sun-Woo; Carmichael, Gregory R.
1994-01-01
Tropospheric ozone production and transport in mid-latitude eastern Asia is studied. Data analysis of surface-based ozone measurements in Japan and satellite-based tropospheric column measurements of the entire western Pacific Rim are combined with results from three-dimensional model simulations to investigate the diurnal, seasonal and long-term variations of ozone in this region. Surface ozone measurements from Japan show distinct seasonal variation with a spring peak and summer minimum. Satellite studies of the entire tropospheric column of ozone show high concentrations in both the spring and summer seasons. Finally, preliminary model simulation studies show good agreement with observed values.
Simulation loop between cad systems, GEANT-4 and GeoModel: Implementation and results
NASA Astrophysics Data System (ADS)
Sharmazanashvili, A.; Tsutskiridze, Niko
2016-09-01
Compare analysis of simulation and as-built geometry descriptions of detector is important field of study for data_vs_Monte-Carlo discrepancies. Shapes consistency and detalization is not important while adequateness of volumes and weights of detector components are essential for tracking. There are 2 main reasons of faults of geometry descriptions in simulation: (1) Difference between simulated and as-built geometry descriptions; (2) Internal inaccuracies of geometry transformations added by simulation software infrastructure itself. Georgian Engineering team developed hub on the base of CATIA platform and several tools enabling to read in CATIA different descriptions used by simulation packages, like XML->CATIA; VP1->CATIA; Geo-Model->CATIA; Geant4->CATIA. As a result it becomes possible to compare different descriptions with each other using the full power of CATIA and investigate both classes of reasons of faults of geometry descriptions. Paper represents results of case studies of ATLAS Coils and End-Cap toroid structures.
A Novel Simulation Technician Laboratory Design: Results of a Survey-Based Study
Hughes, Patrick G; Friedl, Ed; Ortiz Figueroa, Fabiana; Cepeda Brito, Jose R; Frey, Jennifer; Birmingham, Lauren E; Atkinson, Steven Scott
2016-01-01
Objective The purpose of this study was to elicit feedback from simulation technicians prior to developing the first simulation technician-specific simulation laboratory in Akron, OH. Background Simulation technicians serve a vital role in simulation centers within hospitals/health centers around the world. The first simulation technician degree program in the US has been approved in Akron, OH. To satisfy the requirements of this program and to meet the needs of this special audience of learners, a customized simulation lab is essential. Method A web-based survey was circulated to simulation technicians prior to completion of the lab for the new program. The survey consisted of questions aimed at identifying structural and functional design elements of a novel simulation center for the training of simulation technicians. Quantitative methods were utilized to analyze data. Results Over 90% of technicians (n=65) think that a lab designed explicitly for the training of technicians is novel and beneficial. Approximately 75% of respondents think that the space provided appropriate audiovisual (AV) infrastructure and space to evaluate the ability of technicians to be independent. The respondents think that the lab needed more storage space, visualization space for a large number of students, and more space in the technical/repair area. Conclusions A space designed for the training of simulation technicians was considered to be beneficial. This laboratory requires distinct space for technical repair, adequate bench space for the maintenance and repair of simulators, an appropriate AV infrastructure, and space to evaluate the ability of technicians to be independent. PMID:27096134
NASA Technical Reports Server (NTRS)
Prive, Nikki; Errico, R. M.; Carvalho, D.
2018-01-01
The National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO) has spent more than a decade developing and implementing a global Observing System Simulation Experiment framework for use in evaluting both new observation types as well as the behavior of data assimilation systems. The NASA/GMAO OSSE has constantly evolved to relect changes in the Gridpoint Statistical Interpolation data assimiation system, the Global Earth Observing System model, version 5 (GEOS-5), and the real world observational network. Software and observational datasets for the GMAO OSSE are publicly available, along with a technical report. Substantial modifications have recently been made to the NASA/GMAO OSSE framework, including the character of synthetic observation errors, new instrument types, and more sophisticated atmospheric wind vectors. These improvements will be described, along with the overall performance of the current OSSE. Lessons learned from investigations into correlated errors and model error will be discussed.
Boundary pint corrections for variable radius plots - simulation results
Margaret Penner; Sam Otukol
2000-01-01
The boundary plot problem is encountered when a forest inventory plot includes two or more forest conditions. Depending on the correction method used, the resulting estimates can be biased. The various correction alternatives are reviewed. No correction, area correction, half sweep, and toss-back methods are evaluated using simulation on an actual data set. Based on...
Improving the trust in results of numerical simulations and scientific data analytics
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cappello, Franck; Constantinescu, Emil; Hovland, Paul
This white paper investigates several key aspects of the trust that a user can give to the results of numerical simulations and scientific data analytics. In this document, the notion of trust is related to the integrity of numerical simulations and data analytics applications. This white paper complements the DOE ASCR report on Cybersecurity for Scientific Computing Integrity by (1) exploring the sources of trust loss; (2) reviewing the definitions of trust in several areas; (3) providing numerous cases of result alteration, some of them leading to catastrophic failures; (4) examining the current notion of trust in numerical simulation andmore » scientific data analytics; (5) providing a gap analysis; and (6) suggesting two important research directions and their respective research topics. To simplify the presentation without loss of generality, we consider that trust in results can be lost (or the results’ integrity impaired) because of any form of corruption happening during the execution of the numerical simulation or the data analytics application. In general, the sources of such corruption are threefold: errors, bugs, and attacks. Current applications are already using techniques to deal with different types of corruption. However, not all potential corruptions are covered by these techniques. We firmly believe that the current level of trust that a user has in the results is at least partially founded on ignorance of this issue or the hope that no undetected corruptions will occur during the execution. This white paper explores the notion of trust and suggests recommendations for developing a more scientifically grounded notion of trust in numerical simulation and scientific data analytics. We first formulate the problem and show that it goes beyond previous questions regarding the quality of results such as V&V, uncertainly quantification, and data assimilation. We then explore the complexity of this difficult problem, and we sketch complementary