Science.gov

Sample records for convective complex development

  1. Convective cell development and propagation in a mesoscale convective complex

    NASA Technical Reports Server (NTRS)

    Ahn, Yoo-Shin; Brundidge, Kenneth C.

    1987-01-01

    A case study was made of the mesoscale convective complex (MCC) which occurred over southern Oklahoma and northern Texas on 27 May 1981. This storm moved in an eastsoutheasterly direction and during much of its lifetime was observable by radars at Oklahoma City, Ok. and Stephenville, Tx. It was found that the direction of cell (VIP level 3 or more reflectivity) propagation was somewhat erratic but approximately the same as the system (VIP level 1 reflectivity) movement and the ambient wind. New cells developed along and behind the gust front make it appear that once the MCC is initiated, a synergistic relationship exists between the gust front and the MCC. The relationship between rainfall patterns and amounts and the infrared (IR) temperature field in the satellite imagery were examined. The 210 K isotherm of GOES IR imagery was found to encompass the rain area of the storm. The heaviest rainfall was in the vicinity of the VIP level 3 cells and mostly contained within the 205 K isotherm of GOES IR imagery.

  2. Complex spatiotemporal convection patterns

    NASA Astrophysics Data System (ADS)

    Pesch, W.

    1996-09-01

    This paper reviews recent efforts to describe complex patterns in isotropic fluids (Rayleigh-Bénard convection) as well as in anisotropic liquid crystals (electro-hydrodynamic convection) when driven away from equilibrium. A numerical scheme for solving the full hydrodynamic equations is presented that allows surprisingly well for a detailed comparison with experiments. The approach can also be useful for a systematic construction of models (order parameter equations).

  3. Cloud-to-ground lightning activity in mesoscale convective complexes

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.; Macgorman, D. R.

    1986-01-01

    An analysis of the evolution of cloud-to-ground lightning discharges attending convective storms in mesoscale convective systems was conducted in the framework of the mesoscale convective complexes (MCCs) life cycle. The lightning discharge data were acquired by a commercially available lightning detection and location system. Peak rates averaged 42/min for the MCCs analyzed; these rates are comparable to the highest observed rates within other mesoscale storm systems and are greater than 20 times the rates previously observed in isolated thunderstorms. Lightning damage occurs with half of the MCCs and is most frequent between the development and the mature phases of the MCC life cycle. The most active period is also characterized by the greatest average number of discrete strokes and largest fraction of multiple-stroke discharges. The total cloud-to-ground lightning activity and maximum flashing rate do not appear to be directly related to either the size of the cloud shield or total duration of the MCC.

  4. A composite analysis of the Mesoscale Convective Complexes (MCCs) development over the Central Kalimantan and its relation with the propagation of the rainfall systems

    NASA Astrophysics Data System (ADS)

    Trismidianto; Yulihastin, E.; Satyawardhana, H.; Ishida, S.

    2017-01-01

    The composite analysis for 45-cases of the MCC which identified by using infrared satellite imagery over the Central Kalimantan (110° - 116°E, 4°S - 1°N) has been observed. The data used is a combination of satellite data and reanalysis data. This study reported that the MCCs develops triggered by the orographic convective that helped by the convergent surface wind flow through interaction with the sea breeze in the afternoon until midnight and dissipated in the morning. The new convective systems are generated by the divergent outflow of the cold pool, in conjunction with the morning land breeze during MCCs mature. After dissipated, the new convective systems induce the land convection over the Java Island that became heavy rainfall. The initial and mature region are characterized by weak low-level convergence and upper-level divergence, but the low-level divergence begin appear during mature. The MCC develops largely driven by MCC-scale moisture convergence in the lower troposphere and cold core structure in the lower level. The weak surface divergence and upper-level divergence, warm advection in the lower atmosphere are dissipation characteristics. MCCs develop due to low-level cold advection and temperature and separated when dissipated that indicate the existence of the new convective systems propagation.

  5. Complex Convective Thermal Fluxes and Vorticity Structure

    NASA Astrophysics Data System (ADS)

    Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita

    2015-04-01

    Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied

  6. Propagation of convective complex systems triggering potential flooding rainfall of Greater Jakarta using satellite data

    NASA Astrophysics Data System (ADS)

    Eko Nuryanto, Danang; Pawitan, Hidayat; Hidayat, Rahmat; Aldrian, Edvin

    2017-01-01

    A convective cloud system that large, long lived, and exhibits a quasi-circular cloud shield could be called a mesoscale convective complexes (MCC) system. These systems produce a wide variety of severe convective weather such as heavy rainfall. On January 15th, 2013, Jakarta experienced an extraordinary heavy rainfall event. In this study, we examined the propagation of the convective complex system on that date that was triggering heavy rainfall occurred in the Greater Jakarta area, using observations from the Multi-functional Transport Satellite (MTSAT)-IR and the synoptic data. The convective complex system developed from midnight of January 14th, 2013 until the morning of January 15th, 2013 and it was intensified by the influence of low-level westerly winds. The convective complex systems were generated during the nighttime of January 14th, 2013 of over Sumatera, and propagate to the Southeast through Java Sea until the northern coast of the Great Jakarta in the morning of January 15th, 2013. These convective complex systems give heavy rainfall up to 63 mm/h on average over the Greater Jakarta area at 04.00 LT. This heavy rainfall had triggered flash flood in Jakarta January 2013.

  7. A long-lived mesoscale convective complex. II - Evolution and structure of the mature complex

    NASA Technical Reports Server (NTRS)

    Wetzel, P. J.; Cotton, W. R.; Mcanelly, R. L.

    1983-01-01

    The present investigation is concerned with an eight-day episode, during which a series of mesoscale convective complexes (MCC) developed and moved across the country, producing heavy rain and some flooding over an extensive region. An overview of the considered period from August 3 to August 10, 1977 is presented, and the evolution of the August 4 storm is examined. The structure of the mature MCC is discussed, taking into account the August 4-5 storm, a comparative case involving the August 3-4 storm, and an evaluation of the observed phenomena. It is concluded that MCCs are basically tropical in nature and that their dynamics are dominated by buoyant accelerations. It was found that the MCCs developed a warm-core, divergent anticyclonic flow pattern in the upper troposphere which was not present prior to the development of convection. A similar structure is observed in tropical cloud clusters.

  8. Eigenfunction Expansions for Coupled Nonlinear Convection-Diffusion Problems in Complex Physical Domains

    NASA Astrophysics Data System (ADS)

    Cotta, R. M.; Naveira-Cotta, C. P.; Knupp, D. C.; Zotin, J. L. Z.; Pontes, P. C.

    2016-09-01

    This lecture offers an updated review on the Generalized Integral Transform Technique (GITT), with focus on handling complex geometries, coupled problems, and nonlinear convection-diffusion, so as to illustrate some new application paradigms. Special emphasis is given to demonstrating novel developments, such as a single domain reformulation strategy that simplifies the treatment of complex geometries, an integral balance scheme in handling multiscale problems, the adoption of convective eigenvalue problems in dealing with strongly convective formulations, and the direct integral transformation of nonlinear convection-diffusion problems based on nonlinear eigenvalue problems. Representative application examples are then provided that employ recent extensions on the Generalized Integral Transform Technique (GITT), and a few numerical results are reported to illustrate the convergence characteristics of the proposed eigenfunction expansions.

  9. Mesoscale modeling study of severe convection over complex terrain

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Meng, Zhiyong; Zhu, Peijun; Su, Tao; Zhai, Guoqing

    2016-11-01

    Short squall lines that occurred over Lishui, southwestern Zhejiang Province, China, on 5 July 2012, were investigated using the WRF model based on 1°×1° gridded NCEP Final Operational Global Analysis data. The results from the numerical simulations were particularly satisfactory in the simulated radar echo, which realistically reproduced the generation and development of the convective cells during the period of severe convection. The initiation of this severe convective case was mainly associated with the uplift effect of mesoscale mountains, topographic convergence, sufficient water vapor, and enhanced low-level southeasterly wind from the East China Sea. An obvious wind velocity gradient occurred between the Donggong Mountains and the southeast coastline, which easily enabled wind convergence on the windward slope of the Donggong Mountains; both strong mid-low-level southwesterly wind and low-level southeasterly wind enhanced vertical shear over the mountains to form instability; and a vertical coupling relation between the divergence on the upper-left side of the Donggong Mountains and the convergence on the lower-left side caused the convection to develop rapidly. The convergence centers of surface streams occurred over the mountain terrain and updrafts easily broke through the lifting condensation level (LCL) because of the strong wind convergence and topographic lift, which led to water vapor condensation above the LCL and the generation of the initial convective cloud. The centers of surface convergence continually created new convective cells that moved with the southwest wind and combined along the Donggong Mountains, eventually forming a short squall line that caused severe convective weather.

  10. Convective scale interaction: Arc cloud lines and the development and evolution of deep convection

    NASA Technical Reports Server (NTRS)

    Purdom, James Francis Whitehurst

    1986-01-01

    Information is used from satellite data and research aircraft data to provide new insights concerning the mesoscale development and evolution of deep convection in an atmosphere typified by weak synoptic-scale forcing. The importance of convective scale interaction in the development and evolution of deep convection is examined. This interaction is shown to manifest itself as the merger and intersection of thunderstorm outflow boundaries (arc cloud lines) with other convective lines, areas or boundaries. Using geostationary satellite visible and infrared data convective scale interaction is shown to be responsible for over 85 percent of the intense convection over the southeast U.S. by late afternoon, and a majority of that area's afternoon rainfall. The aircraft observations provided valuable information concerning critically important regions of the arc cloud line: (1) the cool outflow region, (2) the density surge line interface region; and (3) the sub-cloud region above the surge line. The observations when analyzed with rapid scan satellite data, helped in defining the arc cloud line's life cycle as 3 evolving stages.

  11. Episodic Subduction arising from convection in a complex-rheology fluid: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    di Giuseppe, Erika; Davaille, Anne

    2010-05-01

    We report here new laboratory experiments on mantle convection using a fluid, whose rheology varies from brittle to viscous when its water content changes. So as an analogy to cooling from above, the fluid is dryed from above, its surface being kept at a constant humidity. Humidity, temperature, fluid thickness and solution concentration are systematically varied, which results in changing the intensity of convection and the rheological properties of the fluid. The entire process is monitored by means of cameras. As the fluid dries at the surface, a chemical boundary layer (CBL) develops, constituted of a thin brittle film on top of a more ductile layer. Folds and cracks are visible on the surface film. When the CBL reaches a critical negative buoyancy, subduction starts and the surface is cut into plates. The subduction is always asymmetric and is an episodic phenomena. The variation of the fluid's rheology, and especially the existence of a brittle state, depending on the experimental parameters such as temperature, humidity rate and concentration, is the key ingredient to exhibit convection with plate-like behavior. Those experiments show that there is no dichotomy between plates and mantle convection. Tectonic plates constitute the upper thermal boundary layer (TBL) of the Earth's mantle, and they subduct as the cold TBL becomes unstable under gravity. The localization of surface deformation on plate boundaries, the rigidity of plates and the asymmetry of subduction is the result of the complex rheology (from brittle to ductile) of mantle material.

  12. Observation of the development of individual clear air convective cells

    NASA Technical Reports Server (NTRS)

    Arnold, A.

    1977-01-01

    A series of radar observations has been used to monitor the development of clear air convective cells. It is suggested that an airfield may be a source of such cells. The cells first appear at a distance of about 11 km, and are observed to be produced every four minutes. The emergence of separate cells supports the bubble theory of convection. After reaching maximum height, a typical decrease of 100-200 m occurs. Various methods used to estimate convective cell energy yield values of 10 to the 12th, 4 x 10 to the 11th, and 10 to the 11th J.

  13. Mechanisms initiating deep convection over complex terrain during COPS.

    SciTech Connect

    Kottmeier, C.; Kalthoff, N.; Barthlott, C.; Corsmeier, U.; Van Baelen, J.; Coulter, R.; Environmental Science Division; Inst. for Meteorology and Climate Research; Lab. de Meteorologie Physique; Inst. of Physics and Meteorology

    2008-12-01

    Precipitating convection in a mountain region of moderate topography is investigated, with particular emphasis on its initiation in response to boundary-layer and mid- and upper-tropospheric forcing mechanisms. The data used in the study are from COPS (Convective and Orographically-induced Precipitation Study) that took place in southwestern Germany and eastern France in the summer of 2007. It is found that the initiation of precipitating convection can be roughly classified as being due to either: (i) surface heating and low-level flow convergence; (ii) surface heating and moisture supply overcoming convective inhibition during latent and/or potential instability; or (iii) mid-tropospheric dynamical processes due to mesoscale convergence lines and forced mean vertical motion. These phenomena have to be adequately represented in models in order to improve quantitative precipitation forecast. Selected COPS cases are analyzed and classified into these initiation categories. Although only a subset of COPS data (mainly radiosondes, surface weather stations, radar and satellite data) are used here, it is shown that convective systems are captured in considerable detail by sensor synergy. Convergence lines were observed by Doppler radar in the location where deep convection is triggered several hours later. The results suggest that in many situations, observations of the location and timing of convergence lines will facilitate the nowcasting of convection. Further on, forecasting of the initiation of convection is significantly complicated if advection of potentially convective air masses over changing terrain features plays a major role. The passage of a frontal structure over the Vosges - Rhine valley - Black Forest orography was accompanied by an intermediate suppression of convection over the wide Rhine valley. Further downstream, an intensification of convection was observed over the Black Forest due to differential surface heating, a convergence line, and the flow

  14. Mesoscale Convective Systems: Structure, Development and Storm-Environment Interactions.

    NASA Astrophysics Data System (ADS)

    Rappaport, Edward N.

    1988-12-01

    This study describes Mesoscale Convective Systems (MCSs), clusterings of thunderstorms associated with significant weather events. Analyses focused on several objectives: a documentation of the conditions in which MCSs form; an elucidation of the life cycle and internal structure of a mid-latitude Mesoscale Convective Complex (MCC); and a systematic comparison of the precipitation structures and environments of many MCSs. In meeting the objectives the evolution of an episode of five MCSs over West Texas was investigated using as a principal source data collected by Texas Tech University as a participant in the Texas High Plains Cooperative Program (HIPLEX). Results of the study show that the first MCS formed near a cold front where lifting along an elevated dew-point front released instability. Surface outflows from the MCSs advanced the surface baroclinic zone associated with the cold front and helped initiate subsequent convection. Convection in the mature MCSs was uncoupled from the surface layer and occurred just ahead of mid-level short-wave perturbations. The third MCS in the sequence formed from isolated echoes over the mountains which merged and grew into an MCC with a low-level precipitation pattern whose organization resembled that of tropical MCSs, extended about 500 km across and had a lifetime of about 24 hours. Behind a squall line and a transition zone near the leading edge occurred an extensive region of precipitation that was organized during the system's mature stage as a set of curved rainbands. A composite wind analysis shows a center of cyclonic inflow at 500 mb near the common center of curvature of the rainbands. Upward motion in the middle - and upper-level cloud and a mesoscale unsaturated downdraft below are diagnosed. MCSs consisting of a squall line followed by a wide range of lighter rain develop in an environment where the relative flow of 300 mb is moist and directed from front to rear. Rainbands embedded in the trailing stratiform

  15. The development of convective structures in the solar photosphere

    NASA Astrophysics Data System (ADS)

    Baran, O.; Stodilka, M.

    2016-12-01

    We study the development of convective structures in the solar photosphere on the basis of the photospheric convection models obtained using data from VTT by the solving of the inverse nonequilibrium radiative transfer problem. Temporal changes of the variations of vertical velocity and temperature within granular cells are analyzed. Features of the appearance and the disappearance of granules according to their size, the formation of "trees" of fragmenting granules are investigated.

  16. The development of convective structures in the solar photosphere

    NASA Astrophysics Data System (ADS)

    Baran, O.; Stodilka, M.

    2016-12-01

    We study the development of convective structures in the solar photosphere on the basis of the photospheric convection models obtained using data from VTT by the solving of the inverse nonequilibrium radiative transfer problem. Temporal changes of the variations of vertical velocity and temperature within granular cells are analyzed. Features of the appearance and the disappearance of granules according to their size, the formation of "trees" of fragmenting granules are investigated.

  17. Developing turbulent convective heat transfer in helical pipes

    SciTech Connect

    Lin, C.X.; Ebadian, M.A.

    1996-12-31

    A fully elliptic numerical study has been carried out to investigate three-dimensional turbulent developing convective heat transfer in helical pipes with finite pitches. The {kappa}-{var_epsilon} standard two-equation turbulence model is used to simulate turbulent flow. The turbulent flow and heat transfer are assumed to develop simultaneously. Uniform inlet velocity and constant wall temperature conditions are applied. The governing equations are solved by a Control-Volume Finite Element Method (CVFEM). Numerical results have been compared to the existing experimental data, and a good agreement has been obtained. The results presented in this paper cover a Reynolds number range of 2.5 {times} 10{sup 4} {minus} 1.0 {times} 10{sup 5}, a pitch range of 0.0--0.6, and a curvature ratio range of 0.025--0.050. The developments of effective thermal conductivity, temperature fields, and local and average Nusselt numbers are given and discussed. It has been found that the examined parameters exert complex effects on the developing thermal fields and heat transfer in the helical pipes. The Nusselt numbers for the helical pipes are oscillatory before the flow is fully developed, especially for the case of a relatively large curvature ratio.

  18. Development of Ensemble Neural Network Convection Parameterizations for Climate Models

    SciTech Connect

    Fox-Rabinovitz, M. S.; Krasnopolsky, V. M.

    2012-05-02

    The novel neural network (NN) approach has been formulated and used for development of a NN ensemble stochastic convection parametrization for climate models. This fast parametrization is built based on data from Cloud Resolving Model (CRM) simulations initialized with and forced by TOGA-COARE data. The SAM (System for Atmospheric Modeling), developed by D. Randall, M. Khairoutdinov, and their collaborators, has been used for CRM simulations. The observational data are also used for validation of model simulations. The SAM-simulated data have been averaged and projected onto the GCM space of atmospheric states to implicitly define a stochastic convection parametrization. This parametrization is emulated using an ensemble of NNs. An ensemble of NNs with different NN parameters has been trained and tested. The inherent uncertainty of the stochastic convection parametrization derived in such a way is estimated. Due to these inherent uncertainties, NN ensemble is used to constitute a stochastic NN convection parametrization. The developed NN convection parametrization have been validated in a diagnostic CAM (CAM-NN) run vs. the control CAM run. Actually, CAM inputs have been used, at every time step of the control/original CAM integration, for parallel calculations of the NN convection parametrization (CAM-NN) to produce its outputs as a diagnostic byproduct. Total precipitation (P) and cloudiness (CLD) time series, diurnal cycles, and P and CLD distributions for the large Tropical Pacific Ocean for the parallel CAM-NN and CAM runs show similarity and consistency with the NCEP reanalysis. The P and CLD distributions for the tropical area for the parallel runs have been analyzed first for the TOGA-COARE boreal winter season (November 1992 through February 1993) and then for the winter seasons of the follow-up parallel decadal simulations. The obtained results are encouraging and practically meaningful. They show the validity of the NN approach. This constitutes an

  19. The Structure and Life-Cycle of Midlatitude Mesoscale Convective Complexes.

    NASA Astrophysics Data System (ADS)

    Maddox, Robert Alan

    Enhanced infrared satellite imagery has been used to document the existence and frequent occurrence, over middle latitudes of the United States, of large, convectively driven weather systems. These systems, named Mesoscale Convective Complexes (MCCs), have not been heretofore recognized or documented in the scientific literature. It is shown that these systems frequently produce a variety of severe convective weather phenomena (such as tornadoes, hailstorms and flash floods) that significantly impact human activities. A preliminary climatology of MCCs, based on satellite data from two warm seasons, indicates that these systems frequently affect United States agricultural regions and it is hypothesized that MCCs produce a highly significant portion of the growing season precipitation over these areas. Objective analyses of composited meteorological conditions attending ten MCC weather systems have revealed a number of distinctive characteristics and interactions with their larger scale environment. These analyses are used to develop a physically realistic model of the life -cycle of the typical midlatitude Mesoscale Convective Complex. The systems develop within a relatively weak and stagnant large -scale setting and are usually closely linked to the eastward progression of a weak middle tropospheric short-wave trough. Initial thunderstorms develop within a region of mesoscale convergence and lifting that is primarily forced by low-level warm advection. The MCC system rapidly grows and takes on a mesoscale organization while it moves slowly eastward ahead of the short-wave trough. Diabatic heating eventually produces a system that is warm core in the middle troposphere and cold core in lower and upper levels. The mature MCC, although it occurs within a considerably different large -scale setting, exhibits many similarities to tropical convective systems. Strong inflow within the lower half of the toposphere forces an intense mesoscale updraft that maintains a region

  20. Application of Graph-Theory Based Algorithm for Identifying Convective Complex Systems over Greater Jakarta basins

    NASA Astrophysics Data System (ADS)

    E Nuryanto, D.; Aldrian, E.; Pawitan, H.; Hidayat, R.

    2017-03-01

    Heavy rainfalls over the Greater Jakarta (GJ) basins during January 14 - 15th, 2013 were suspected to be derived from convective complex systems (CCSs) as subsets of mesoscale convective systems (MCSs). This study, implementing a graph-theory based algorithm on black body temperature (TBB) dataset, identified CCS over GJ during heavy rainfall event on January 14 - 15th, 2013. We found that convective cloud cluster for ≤ 221 K of TBB more than 6 hours (about 16 hours of duration) with average of eccentricity was 0.47. The maximum area of this system was about 249,731.9 km2 at 0300 Local Time (LT) January 15th, 2013. Ones of these convective system features is not match with MCC definition. We defined this convective system as convective cloud system that large, long lived, and very cold of cloud shield. This system is in agreement with heavy rainfall (more than 40 mm/3h) at 0200 - 0400 LT January 15th, 2013 over GJ basins.

  1. Convective instabilities in complex systems with partly free surface

    NASA Astrophysics Data System (ADS)

    Schwabe, Dietrich

    2007-04-01

    Experiments and observations and some selected theoretical studies of thermocapillary instabilities are reviewed and presented together with new unpublished work. We start with simple idealized model systems of pure thermocapillarity and add to them more complex features like gravity forces, temperature gradients inclined to the free surface, static and dynamic surface deformations, solutocapillary effects and reacting or moving crystal boundaries (like during unidirectional solidification). Many effects and instabilities are demonstrated in video clips which can be downloaded from http://meyweb.physik.uni-giessen.de/1_Forschung/crystalgrowth/video/homepage.html. We try to point out the relationship of thermocapillary instabilities in the more complex systems with those in theoretical studies where the names of these instabilities have been coined.

  2. Evaluation and development of satellite inferences of convective storm intensity using combined case study analysis and thunderstorm model simulations

    NASA Technical Reports Server (NTRS)

    Cotton, W. R.; Tripoli, G. J.

    1980-01-01

    Major research accomplishments which were achieved during the first year of the grant are summarized. The research concentrated in the following areas: (1) an examination of observational requirements for predicting convective storm development and intensity as suggested by recent numerical experiments; (2) interpretation of recent 3D numerical experiments with regard to the relationship between overshooting tops and surface wind gusts; (3) the development of software for emulating satellite-inferred cloud properties using 3D cloud model predicted data; and (4) the development of a conceptual/semi-quantitative model of eastward propagating, mesoscale convective complexes forming to the lee of the Rocky Mountains.

  3. Evaluation and development of satellite inferences of convective storm intensity using combined case study and thunderstorm model simulations

    NASA Technical Reports Server (NTRS)

    Cotton, W. R.; Tripoli, G. J.

    1982-01-01

    Observational requirements for predicting convective storm development and intensity as suggested by recent numerical experiments are examined. Recent 3D numerical experiments are interpreted with regard to the relationship between overshooting tops and surface wind gusts. The development of software for emulating satellite inferred cloud properties using 3D cloud model predicted data and the simulation of Heymsfield (1981) Northern Illinois storm are described as well as the development of a conceptual/semi-quantitative model of eastward propagating, mesoscale convective complexes forming to the lee of the Rocky Mountains.

  4. Fully developed nanofluid mixed convection flow in a vertical channel

    NASA Astrophysics Data System (ADS)

    Al-Amri, Fahad G.

    2017-04-01

    A closed form analytical solution of laminar mixed convection heat transfer of a nanofluid between two vertical parallel plates, accounting for the effects Brownian motion and thermophoresis, is presented for the fully developed region under thermal boundary conditions of the first and fourth kinds. Four kinds of nano-sized solid particles with varied thermophysical properties suspended in water are considered. Closed form analytical expressions of velocity and temperature fields, pressure gradients, nanoparticle concentration profiles, and Nusslet numbers are illustrated. Effects of the controlling parameters, namely the buoyancy parameter, thermal conductivity, solid/fluid ratio, and volume fraction, on the hydrodynamic and heat transfer parameters such as pressure gradient and Nusslet number are discussed in detail. It is found that the Nusslet number increases with increases in the buoyancy parameter and volume fraction. However, the pressure drop is found to increase with volume fraction and decrease with the buoyancy parameter. In addition, for upward mixed convection flow, the pressure drop attributed to the addition of nano-sized solid particles into the base fluid can be overcome by the buoyancy forces. The critical values of the buoyancy parameter- where the buoyancy forces balance the viscous forces-are obtained and presented.

  5. Defect chaos and bursts: hexagonal rotating convection and the complex Ginzburg-Landau equation.

    PubMed

    Madruga, Santiago; Riecke, Hermann; Pesch, Werner

    2006-02-24

    We employ numerical computations of the full Navier-Stokes equations to investigate non-Boussinesq convection in a rotating system using water as the working fluid. We identify two regimes. For weak non-Boussinesq effects the Hopf bifurcation from steady to oscillating (whirling) hexagons is supercritical and typical states exhibit defect chaos that is systematically described by the cubic complex Ginzburg-Landau equation. For stronger non-Boussinesq effects the Hopf bifurcation becomes subcritical and the oscillations exhibit localized chaotic bursting, which is modeled by a quintic complex Ginzburg-Landau equation.

  6. LASE measurements of convective boundary layer development during SGP97

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Browell, Edward V.; Ferrare, Richard A.; Senff, Christoph; Davis, Kenneth J.a; Lenschow, Donald H.; Kooi, Susan; Brackett, Vince; Clayton, Marian

    1998-01-01

    The Southern Great Plains 1997 (SGP97) field experiment was conducted in Oklahoma during June-July 1997 to validate the models used for computing remote soil moisture using measurements by microwave radiometers. One of the objectives of SGP97 was to examine the effect of soil moisture on the evolution of the Atmospheric Boundary Layer (ABL) and clouds over the Southern Great Plains (SGP) during the warm season. The LASE (Lidar Atmospheric Sensing Experiment) airborne DIAL (Differential Absorption Lidar) system, which was flown autonomously on the NASA ER-2 aircraft during previous missions, was reconfigured to fly on the NASA P3 research aircraft. During SGP97 LASE was used to study the morning evolution of the ABL, particularly as manifested in the development of the convective boundary layer, and to study the influence of soil moisture variations on the development of ABL. The ABL development is strongly influenced by the surface energy budget, which is in turn influenced by soil moisture, mesoscale meteorology, clouds, and solar insolation. LASE data acquired during this mission are being used to study the ABL water vapor budget, the development of the ABL, spatial and temporal variabilities in the ABL, and the meteorological factors that influence the ABL development. This field experiment also permitted comparisons of LASE water vapor measurements with water vapor profiles acquired by radiosondes launched at the DOE (Department of Energy) Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site and at NASA/Wallops Flight Facility, as well as with measurements from other SGP97 aircraft.

  7. LASE measurements of convective boundary layer development during SGP97

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Browell, Edward V.; Ferrare, Richard A.; Senff, Christoph; Davis, Kenneth J.a; Lenschow, Donald H.; Kooi, Susan; Brackett, Vince; Clayton, Marian

    1998-01-01

    The Southern Great Plains 1997 (SGP97) field experiment was conducted in Oklahoma during June-July 1997 to validate the models used for computing remote soil moisture using measurements by microwave radiometers. One of the objectives of SGP97 was to examine the effect of soil moisture on the evolution of the Atmospheric Boundary Layer (ABL) and clouds over the Southern Great Plains (SGP) during the warm season. The LASE (Lidar Atmospheric Sensing Experiment) airborne DIAL (Differential Absorption Lidar) system, which was flown autonomously on the NASA ER-2 aircraft during previous missions, was reconfigured to fly on the NASA P3 research aircraft. During SGP97 LASE was used to study the morning evolution of the ABL, particularly as manifested in the development of the convective boundary layer, and to study the influence of soil moisture variations on the development of ABL. The ABL development is strongly influenced by the surface energy budget, which is in turn influenced by soil moisture, mesoscale meteorology, clouds, and solar insolation. LASE data acquired during this mission are being used to study the ABL water vapor budget, the development of the ABL, spatial and temporal variabilities in the ABL, and the meteorological factors that influence the ABL development. This field experiment also permitted comparisons of LASE water vapor measurements with water vapor profiles acquired by radiosondes launched at the DOE (Department of Energy) Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site and at NASA/Wallops Flight Facility, as well as with measurements from other SGP97 aircraft.

  8. Development of a mechanistic model for forced convection subcooled boiling

    NASA Astrophysics Data System (ADS)

    Shaver, Dillon R.

    The focus of this work is on the formulation, implementation, and testing of a mechanistic model of subcooled boiling. Subcooled boiling is the process of vapor generation on a heated wall when the bulk liquid temperature is still below saturation. This is part of a larger effort by the US DoE's CASL project to apply advanced computational tools to the simulation of light water reactors. To support this effort, the formulation of the dispersed field model is described and a complete model of interfacial forces is formulated. The model has been implemented in the NPHASE-CMFD computer code with a K-epsilon model of turbulence. The interfacial force models are built on extensive work by other authors, and include novel formulations of the turbulent dispersion and lift forces. The complete model of interfacial forces is compared to experiments for adiabatic bubbly flows, including both steady-state and unsteady conditions. The same model is then applied to a transient gas/liquid flow in a complex geometry of fuel channels in a sodium fast reactor. Building on the foundation of the interfacial force model, a mechanistic model of forced-convection subcooled boiling is proposed. This model uses the heat flux partitioning concept and accounts for condensation of bubbles attached to the wall. This allows the model to capture the enhanced heat transfer associated with boiling before the point of net generation of vapor, a phenomenon consistent with existing experimental observations. The model is compared to four different experiments encompassing flows of light water, heavy water, and R12 at different pressures, in cylindrical channels, an internally heated annulus, and a rectangular channel. The experimental data includes axial and radial profiles of both liquid temperature and vapor volume fraction, and the agreement can be considered quite good. The complete model is then applied to simulations of subcooled boiling in nuclear reactor subchannels consistent with the

  9. Processes of Hydrometeor Development in Oklahoma Convective Clouds.

    NASA Astrophysics Data System (ADS)

    Heymsfield, Andrew J.; Hjelmfelt, Mark R.

    1984-10-01

    This study employs in situ measurements to examine cloud conditions in which hydrometeors develop in mature Oklahoma convective clouds and to develop hypotheses as to how they formed. The measurements were made from penetrations on six days using a T-28 aircraft. Values of the maximum vertical velocity W in cells ranged from 5 to 35 m s1, and the liquid water content (LWC) up to 6 gmminus;3;LWCs are usually less than adiabatic. Drops are found primarily in strong updrafts at T/>8°c. Graupel are present in low concentrations in the strong updrafts and in moderate concentrations in the weak to intermediate updrafts. Planar and needle ice crystals and aggregates are present in copious concentrations in regions of low LWC and W. Strong evidence exists for production of secondary ice crystals (SICS) through a Hallett and Mossop type of mechanism involving cloud droplets >24m in diameter.Particle growth calculations are used in conjunction with the measurements to infer the processes of formation of drops, graupel and hail, and secondary ice crystals. Most drops of diameters <500m found at temperatures below 0°C are inferred to form through coalescence growth and most of diameters >500m through shedding from growing and/or melting graupel and hail. Embryos of hailstones are found to develop to 1 cm in diameter most rapidly from millimetric size drops produced from shedding and from aggregates of planar ice-crystals. Most growth of particles to 1 cm hailstones occurs in the regions of intermediate values of LWC (1-2 gm3) and W (5-15 m sminus;1) at temperatures higher than 20°C. In these regions, moderate concentrations of ice particles can develop over appreciable periods and depletion of the liquid water content due to collection by ice particles is minimal. The regions of high LWC and W are found to be the least conducive to SIC production. Initially, most SICs come from riming of aggregates in clouds which develop embedded within cloud layers and from frozen drops

  10. Flow reversal of fully developed double diffusive mixed convection in a vertical channel

    NASA Astrophysics Data System (ADS)

    Makhatar, Nur Asiah Mohd; Saleh, Habibis; Hashim, Ishak

    2015-10-01

    The mixed convection flow within a vertical channel having internal heat generation at a rate proportional to a power of the temperature difference is considered. The analysis is concerning the studies of occurrence of flow reversal and the effects of three dimensionless parameters, identified as the internal heat parameter (G), a mixed convection parameter (λ) and the exponent (p) in the local heating term on the fully developed double diffusive mixed convection flow in a vertical channel. The governing equations are solved numerically via MAPLE. It was found that flow reversal occurs with larger values of internal heat parameter and mixed convection parameter, but smaller values of local-heating exponent. They also show that, unlike the internal heat parameter and the local-heating exponent, the mixed convection parameter do not give any significant effect on the temperature.

  11. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    SciTech Connect

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2016-11-25

    High resolution numerical simulation can provide insight into important physical processes that occur within the planetary boundary layer (PBL). The present work employs large eddy simulation (LES) using the Weather Forecasting and Research (WRF) model, with the LES domain nested within mesoscale simulation, to simulate real conditions in the convective PBL over an area of complex terrain. A multiple nesting approach has been used to downsize the grid spacing from 12.15 km (mesoscale) to 0.03 km (LES). A careful selection of grid spacing in the WRF Meso domain has been conducted to minimize artifacts in the WRF-LES solutions. The WRF-LES results have been evaluated with in situ and remote sensing observations collected during the US Department of Energy-supported Columbia BasinWind Energy Study (CBWES). Comparison of the first- and second-order moments, turbulence spectrum, and probability density function (PDF) of wind speed shows good agreement between the simulations and data. Furthermore, the WRF-LES variables show a great deal of variability in space and time caused by the complex topography in the LES domain. The WRF-LES results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day. In addition to basic studies related to boundary-layer meteorology, results from these simulations can be used in other applications, such as studying wind energy resources, atmospheric dispersion, fire weather etc.

  12. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2016-11-01

    The Weather Research and Forecasting (WRF) model can be used to simulate atmospheric processes ranging from quasi-global to tens of m in scale. Here we employ large-eddy simulation (LES) using the WRF model, with the LES-domain nested within a mesoscale WRF model domain with grid spacing decreasing from 12.15 km (mesoscale) to 0.03 km (LES). We simulate real-world conditions in the convective planetary boundary layer over an area of complex terrain. The WRF-LES model results are evaluated against observations collected during the US Department of Energy-supported Columbia Basin Wind Energy Study. Comparison of the first- and second-order moments, turbulence spectrum, and probability density function of wind speed shows good agreement between the simulations and observations. One key result is to demonstrate that a systematic methodology needs to be applied to select the grid spacing and refinement ratio used between domains, to avoid having a grid resolution that falls in the grey zone and to minimize artefacts in the WRF-LES model solutions. Furthermore, the WRF-LES model variables show large variability in space and time caused by the complex topography in the LES domain. Analyses of WRF-LES model results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day as well as the distance from the inflow boundaries.

  13. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2017-04-01

    The Weather Research and Forecasting (WRF) model can be used to simulate atmospheric processes ranging from quasi-global to tens of m in scale. Here we employ large-eddy simulation (LES) using the WRF model, with the LES-domain nested within a mesoscale WRF model domain with grid spacing decreasing from 12.15 km (mesoscale) to 0.03 km (LES). We simulate real-world conditions in the convective planetary boundary layer over an area of complex terrain. The WRF-LES model results are evaluated against observations collected during the US Department of Energy-supported Columbia Basin Wind Energy Study. Comparison of the first- and second-order moments, turbulence spectrum, and probability density function of wind speed shows good agreement between the simulations and observations. One key result is to demonstrate that a systematic methodology needs to be applied to select the grid spacing and refinement ratio used between domains, to avoid having a grid resolution that falls in the grey zone and to minimize artefacts in the WRF-LES model solutions. Furthermore, the WRF-LES model variables show large variability in space and time caused by the complex topography in the LES domain. Analyses of WRF-LES model results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day as well as the distance from the inflow boundaries.

  14. Developing Oceanic Convective Products to Mitigate the Impact of Weather Hazards on Transoceanic Flights

    NASA Astrophysics Data System (ADS)

    Nierow, A.

    2003-12-01

    Transoceanic flights will increase significantly in the next decade. To manage this increased demand for capacity, while maintaining safety, the Federal Aviation Administration (FAA) is exploring whether the separation minima normally used between aircraft crossing oceanic regions can be reduced both horizontally and vertically. However, before reducing separation standards, the increased hazard of encountering convective weather over oceanic routes must be considered. New evidence has shown that roughly half of the turbulence encounters over oceanic regions were likely associated with convective activity. This phenomenon, Convectively-Induced Turbulence (CIT), can occur several kilometers from convective cores. Operational decision-makers need to detect turbulence associated with oceanic convective activity to route or reroute aircraft safely. However, the only weather data consistently available is from satellite imagery, which can reveal potential areas of convection, but can't unambiguously isolate the hazardous regions from the benign regions. Being able to do this would improve routing and rerouting decisions. The FAA and other agencies are collaborating to develop oceanic convective products. The National Weather Service's Aviation Weather Center created a product that identifies thunderstorms by using the output from different satellite imagers. The technique exploits the difference between the 11-micron infrared (IR) channel and the 6.7-micron water vapor channel. The National Center for Atmospheric Research has developed a new product that maps cloud top temperatures drawn from IR satellite imagery and converts them to aircraft flight levels. In addition, the Naval Research Lab in Monterey, CA is developing cloud classification algorithms that will distinguish between cirrus and convective clouds. We have compared these new convective diagnostic techniques to long-range ground base lightning data and lightning data from the National Aeronautics and Space

  15. Using Satellite Observations to Infer the Relationship Between Cold Pools and Subsequent Convection Development

    NASA Technical Reports Server (NTRS)

    Elsaesser, Gregory

    2015-01-01

    Cold pools are increasingly being recognized as important players in the evolution of both shallow and deep convection; hence, the incorporation of cold pool processes into a number of recently developed convective parameterizations. Unfortunately, observations serving to inform cold pool parameterization development are limited to select field programs and limited radar domains. However, a number of recent studies have noted that cold pools are often associated with arcs-lines of shallow clouds traversing 10 100 km in visible satellite imagery. Boundary layer thermodynamic perturbations are plausible at such scales, coincident with such mesoscale features. Atmospheric signatures of features at these spatial scales are potentially observable from satellites. In this presentation, we discuss recent work that uses multi-sensor, high-resolution satellite products for observing mesoscale wind vector fluctuations and boundary layer temperature depressions attributed to cold pools produced by antecedent convection. The relationship to subsequent convection as well as convective system longevity is discussed. As improvements in satellite technology occur and efforts to reduce noise in high-resolution orbital products progress, satellite pixel level (10 km) thermodynamic and dynamic (e.g. mesoscale convergence) parameters can increasingly serve as useful benchmarks for constraining convective parameterization development, including for regimes where organized convection contributes substantially to the cloud and rainfall climatology.

  16. Can a partially molten metasedimentary sequence convect? Insights from the El Oro Complex (Ecuador) and 1D thermal modelling.

    NASA Astrophysics Data System (ADS)

    Riel, Nicolas; Mercier, Jonathan

    2014-05-01

    It is now widely accepted that the formation and the evolution of high elevation plateaus such as the Tibet and the Altiplano-Puna are strongly linked to mantel magma underplating at crustal root level and partial melting of the lower crust. Understanding the rheological behavior of the deep continental crust during these episodes is therefore crucial to constrain the evolution of such plateau. In this study we present results obtained from pressure-temperature estimates and thermal modeling of gabbro underplating at crustal root level (25km) in the El Oro Metamorphic Complex (Ecuador). The aim of this study is: (1) to complete previously published P-Tmax estimates in the northern part of the migmatitic unit, close to the magmatic contact with the gabbroic unit, to obtain better constraints on the metamorphic gradient during partial melting, (2) to characterize the effects of melt extraction, latent heat capture and release and a temperature-dependent thermal diffusivity on the thermal evolution of the system using a specifically developed numerical model, and (3) in the light of the thermal modeling results, to discuss the geological processes involved during partial melting of the metasedimentary crust. Our modeling results show that the estimate metamorphic gradient cannot be reproduced when solely taking into account latent heat, melt extraction and thermal-dependent diffusivity. In the light of geological, geochemical and modeling evidence we show that the lower migmatitic unit, controlled by biotite-dehydration melting reactions was subject to convective motion that contributed to lower the metamorphic gradient and rapidly transfer heat upward. For a biotite-rich rock (~20%) containing 15-20% of melt, we estimate the maximum viscosity of the rock that allows convection at ~7.5e17 Pa.s. Our results also suggest that convection can be maintained as long as heat is provided and that temperature lies in the stability field of biotite-dehydration melting (750-900°C).

  17. Changes in Stratiform Clouds of Mesoscale Convective Complex Introduced by Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Lin, B.; Min, Q.-L.; Li, R.

    2010-01-01

    Aerosols influence the earth s climate through direct, indirect, and semi-direct effects. There are large uncertainties in quantifying these effects due to limited measurements and observations of aerosol-cloud-precipitation interactions. As a major terrestrial source of atmospheric aerosols, dusts may serve as a significant climate forcing for the changing climate because of its effect on solar and thermal radiation as well as on clouds and precipitation processes. Latest satellites measurements enable us to determine dust aerosol loadings and cloud distributions and can potentially be used to reduce the uncertainties in the estimations of aerosol effects on climate. This study uses sensors on various satellites to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective complex (MCC). A trans-Atlantic dust outbreak of Saharan origin occurring in early March 2004 is considered. For the observed MCCs under a given convective strength, small hydrometeors were found more prevalent in the dusty stratiform regions than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust regions, particularly at altitudes where heterogeneous nucleation of mineral dust prevails, further supports the observed changes of clouds and precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the size spectrum of precipitation-sized hydrometeors from heavy precipitation to light precipitation and ultimately to suppress precipitation and increase the lifecycle of cloud systems, especially over stratiform areas.

  18. Observations of the Convective Environment in Developing and Non-developing Tropical Disturbances

    DTIC Science & Technology

    2012-01-01

    Quarterly Journal of the Royal Meteorological Society Q. J. R. Meteorol. Soc. (2012) Observations of the convective environment in developing and non...Germany bDept. of Meteorology , Naval Postgraduate School, Monterey, California, USA cHurricane Research Division, NOAA, Miami, Florida, USA...Correspondence to: R. K. Smith, Meteorological Institute, Ludwig-Maximilians University, Theresienstrasse 37, 80333 Munich, Germany. E-mail: roger.smith@lmu.de

  19. The interactive role of subsynoptic scale jet streak and planetary boundary layer processes in organizing an isolated convective complex

    NASA Technical Reports Server (NTRS)

    Kaplan, M. L.; Zack, J. W.; Wong, V. C.; Coats, G. D.

    1984-01-01

    Surface analyses and numerical simulation sensitivity studies are compared in order to determine the role played by deep, well-mixed, and well-heated boundary layers in perturbing a weak jet streak in proximity to the development of an isolated but intense convective complex associated with the Grand Island, Nebraska tornado outbreak of June 3-4, 1980. A brief description of the case is first presented, emphasizing three-hourly surface analyses, radar, and satellite data. The results of numerical experiments comparing differences in the runs with and without diurnal surface sensible heating are discussed and related to observations. The dynamical processes responsible for these simulation differences are discussed, and the significance of these differences are considered in terms of their effect on the preconvective environment.

  20. Convective thermal fluxes in unsteady non-homogeneous flows generating complex three dimensional vorticity patterns

    NASA Astrophysics Data System (ADS)

    Tellez Alvarez, Jackson David; Redondo, Jose Manuel; Sanchez, Jesu Mary

    2016-04-01

    fresh water in order to form density interfaces. The Reynolds number can be reduced adding Glicerine the set of dimensionless parameters define different conditions of both numeric and small scale laboratory applied often in modeling environmental flows. Fields of velocity, density and their gradients are computed using advanced visualization [8 9]. Visualizations are performed by PIV, Particle tracking and shadowgraph. When convective heating and cooling takes place the patterns depend on the parameter space region of the initial conditions We also map the different transitions between two and three dimensional convection in an enclosure with several complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [2-4]. The thermal convective driven flows are generated by Seebeck and Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. At present side heat fluxes are considered and estimated as a function of Rayleigh, Peclet and Nusselt numbers, [4-6] The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or non-mixing front occurring at a density interface due to body forces [12] can be compared with the convective fronts. The evolution of the turbulent mixing layer and its complex configuration is studied taking into account the dependence on the initial modes at the early stages, Self-similar information [13]. Spectral and Fractal analysis on the images seems very useful in order to

  1. Development of lidar sensor for cloud-based measurements during convective conditions

    NASA Astrophysics Data System (ADS)

    Vishnu, R.; Bhavani Kumar, Y.; Rao, T. Narayana; Nair, Anish Kumar M.; Jayaraman, A.

    2016-05-01

    Atmospheric convection is a natural phenomena associated with heat transport. Convection is strong during daylight periods and rigorous in summer months. Severe ground heating associated with strong winds experienced during these periods. Tropics are considered as the source regions for strong convection. Formation of thunder storm clouds is common during this period. Location of cloud base and its associated dynamics is important to understand the influence of convection on the atmosphere. Lidars are sensitive to Mie scattering and are the suitable instruments for locating clouds in the atmosphere than instruments utilizing the radio frequency spectrum. Thunder storm clouds are composed of hydrometers and strongly scatter the laser light. Recently, a lidar technique was developed at National Atmospheric Research Laboratory (NARL), a Department of Space (DOS) unit, located at Gadanki near Tirupati. The lidar technique employs slant path operation and provides high resolution measurements on cloud base location in real-time. The laser based remote sensing technique allows measurement of atmosphere for every second at 7.5 m range resolution. The high resolution data permits assessment of updrafts at the cloud base. The lidar also provides real-time convective boundary layer height using aerosols as the tracers of atmospheric dynamics. The developed lidar sensor is planned for up-gradation with scanning facility to understand the cloud dynamics in the spatial direction. In this presentation, we present the lidar sensor technology and utilization of its technology for high resolution cloud base measurements during convective conditions over lidar site, Gadanki.

  2. An Automated Method to Identify Mesoscale Convective Complexes in the Regional Climate Model Evaluation System

    NASA Astrophysics Data System (ADS)

    Whitehall, K. D.; Jenkins, G. S.; Mattmann, C. A.; Waliser, D. E.; Kim, J.; Goodale, C. E.; Hart, A. F.; Ramirez, P.; Whittell, J.; Zimdars, P. A.

    2012-12-01

    Mesoscale convective complexes (MCCs) are large (2 - 3 x 105 km2) nocturnal convectively-driven weather systems that are generally associated with high precipitation events in short durations (less than 12hrs) in various locations through out the tropics and midlatitudes (Maddox 1980). These systems are particularly important for climate in the West Sahel region, where the precipitation associated with them is a principal component of the rainfall season (Laing and Fritsch 1993). These systems occur on weather timescales and are historically identified from weather data analysis via manual and more recently automated processes (Miller and Fritsch 1991, Nesbett 2006, Balmey and Reason 2012). The Regional Climate Model Evaluation System (RCMES) is an open source tool designed for easy evaluation of climate and Earth system data through access to standardized datasets, and intrinsic tools that perform common analysis and visualization tasks (Hart et al. 2011). The RCMES toolkit also provides the flexibility of user-defined subroutines for further metrics, visualization and even dataset manipulation. The purpose of this study is to present a methodology for identifying MCCs in observation datasets using the RCMES framework. TRMM 3 hourly datasets will be used to demonstrate the methodology for 2005 boreal summer. This method promotes the use of open source software for scientific data systems to address a concern to multiple stakeholders in the earth sciences. A historical MCC dataset provides a platform with regards to further studies of the variability of frequency on various timescales of MCCs that is important for many including climate scientists, meteorologists, water resource managers, and agriculturalists. The methodology of using RCMES for searching and clipping datasets will engender a new realm of studies as users of the system will no longer be restricted to solely using the datasets as they reside in their own local systems; instead will be afforded rapid

  3. The development of convective instability, wind shear, and vertical motion in relation to convection activity and synoptic systems in AVE 4

    NASA Technical Reports Server (NTRS)

    Davis, J. G.; Scoggins, J. R.

    1981-01-01

    Data from the Fourth Atmospheric Variability Experiment were used to investigate conditions/factors responsible for the development (local time rate-of-change) of convective instability, wind shear, and vertical motion in areas with varying degrees of convective activity. AVE IV sounding data were taken at 3 or 6 h intervals during a 36 h period on 24-25 April 1975 over approximately the eastern half of the United States. An error analysis was performed for each variable studied.

  4. Viking observations of a reverse convection cell developing in response to a northward turning of the interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Henderson, M. G.; Murphree, J. S.

    Observations of a developing reverse convection cell on September 23, 1986 are examined using auroral images acquired with the UV imager on board the Viking Spacecraft. The cell possesses a counter-clockwise rotational sense and evolves on the duskside of the northern auroral distribution between the duskside oval and a complex duskside transpolar arc system. As the structure evolves, it grows and appears to displace the transpolar arc toward the dawn. We interpret these observations in terms of a model proposed by Burch et al., [1992] in which open field lines produced by merging on the high latitude magnetopause produce reverse convection cells between the oval and the transpolar arcs associated with horse-collar or teardrop auroral patterns.

  5. Exploring the Development of Conceptual Ecologies: Communities of Concepts Related to Convection and Heat.

    ERIC Educational Resources Information Center

    Jones, M. Gail; Carter, Glenda; Rua, Melissa J.

    2000-01-01

    Examines the relationships and development of communities of concepts related to heat and convection among fifth grade students. Discusses the influence of familial and cultural experiences on conceptual development as well as the extent to which competing phenomena affect the development of new conceptual understandings. (Contains 49 references.)…

  6. Exploring the Development of Conceptual Ecologies: Communities of Concepts Related to Convection and Heat.

    ERIC Educational Resources Information Center

    Jones, M. Gail; Carter, Glenda; Rua, Melissa J.

    2000-01-01

    Examines the relationships and development of communities of concepts related to heat and convection among fifth grade students. Discusses the influence of familial and cultural experiences on conceptual development as well as the extent to which competing phenomena affect the development of new conceptual understandings. (Contains 49 references.)…

  7. Predicting Turbulent Convective Heat Transfer in Fully Developed Duct Flows

    NASA Technical Reports Server (NTRS)

    Rokni, Masoud; Gatski, Thomas B.

    2001-01-01

    The performance of an explicit algebraic stress model (EASM) is assessed in predicting the turbulent flow and forced heat transfer in both straight and wavy ducts, with rectangular, trapezoidal and triangular cross-sections, under fully developed conditions. A comparison of secondary flow patterns. including velocity vectors and velocity and temperature contours, are shown in order to study the effect of waviness on flow dynamics, and comparisons between the hydraulic parameters. Fanning friction factor and Nusselt number, are also presented. In all cases. isothermal conditions are imposed on the duct walls, and the turbulent heat fluxes are modeled using gradient-diffusion type models. The formulation is valid for Reynolds numbers up to 10(exp 5) and this minimizes the need for wall functions that have been used with mixed success in previous studies of complex duct flows. In addition, the present formulation imposes minimal demand on the number of grid points without any convergence or stability problems. Criteria in terms of heat transfer and friction factor needed to choose the optimal wavy duct cross-section for industrial applications among the ones considered are discussed.

  8. Investigation of the process chain leading to the development of convection during COP IOP 4b

    NASA Astrophysics Data System (ADS)

    Bauer, H.-S.; Schwitalla, T.; Aoshima, F.; Behrendt, A.; Wulfmeyer, V.

    2012-04-01

    The COPS IOP 4b took place from June 20th to June 21st 2007. It was characterized by widespread convection in the COPS domain. The development was steered by a strong low pressure system southwest of the British Isles. On its eastern side warm and moist subtropical air was directed to central Europe. First convection was triggered over the Vosges Mountains around noon on the 20th of June long before the front approached the COPS region. After a calm early afternoon, severe convection was triggered in wide regions of the COPS region in the evening and moved eastwards to Bavaria during the night to the 21st of June. In contrast to other IOPs, the situation was not captured correctly by most of the involved prediction models, no matter whether they were operated with or without sophisticated data assimilation. Aim of this presentation is to unravel the mechanisms responsible for the triggering of convection and to understand the processes preparing the atmosphere for the development of severe convection during the afternoon and night. For this purpose, many different data sets will be investigated ranging from the high resolution Vienna Enhanced Resolution Analysis (VERA), high resolution radar and satellite images and composites to soundings and data as well as retrieved products from the instruments at the COPS supersites. First impression is that the complicated low-level wind field is the major driver for the preparation of the atmosphere and therefore for the development of convection during the day. The inaccuracies in representing the low level wind field are also expected to be the major reason for the failure of the models to correctly predict the situation.

  9. Sensitivity studies of developing convection in a cloud-resolving model

    NASA Astrophysics Data System (ADS)

    Petch, J. C.

    2006-01-01

    Cloud-resolving models (CRMs) remain an important tool for providing detailed process information about convection. In this short paper I focus on the development of deep convection and consider what can be considered a minimum expense benchmark simulation for comparison with a numerical weather-prediction model. To decide this a range of sensitivity studies are presented to aspects of the experimental set-up which strongly impact the computational expense. Many of the sensitivities shown in these CRM experiments are quite different to those seen in previous papers which have tended to focus more on deep active convection. Here it is shown that for the case-study presented a minimum expense benchmark simulation must be a 3D simulation. A 200 m horizontal grid length and a domain of 25 km are also required to capture the most important processes.

  10. The development of small-scale convection below evolving oceanic plates

    NASA Astrophysics Data System (ADS)

    Coltice, N.; Garnero, E.

    2015-12-01

    Seafloor of older ages shows a constancy of heat flow, and bathymetry that is different from what is expected for a half-space cooling model. These observations led to consideration of the existence of small-scale convection below the lithosphere (Parsons and McKenzie, 1978). Previous studies have characterized the detailed physics of such processes (Davaille and Jaupart, 1994; Choblet and Sotin, 2000; Solomatov and Moresi, 2000; Korenaga and Jordan, 2003 among others). However, questions remain for applications to the Earth: what is the shape of developed small-scale convection, what length-scales are involved, how does associated small-scale convection depend on the plate layout and its time-dependence. Using 3D spherical models of mantle convection with plate-like behaviour (Tackley, 2008), we will present a study of developed small-scale convection in a context of self-organization of plates and mantle flow. Small-scale convection depends on the resistance of the lithosphere, and its development beneath large plates produce network shapes with specific length-scales and orientations (see figure). We will show the impact of the size of plates and the evolution of subduction on the small-scale convection, and characterize how the age-heat flow relationship can change with time. The potential for seismic detection of the spatiotemporal patterns of temperature heterogeneity will also be discussed. ReferencesChoblet, G., and C. Sotin, Phys. Earth Planet. Inter. 119, 321-336 (2000). Davaille, A., and C. Jaupart, J. Geophys. Res. 99, 19,853-19,866 (1994). Korenaga, J., and T. H. Jordan, J. Geophys. Res. 108, 2333, (2003). Parsons, B., and D. McKenzie, J. Geophys. Res. 83, 4485-4496 (1978). Solomatov, V. S., and L. N. Moresi, J. Geophys. Res. 105, 21,795-21,817 (2000). Tackley, P. J., Phys. Earth Planet. Inter. 171, 7-18 (2008). Figure: Age of the seafloor in Myrs and white countour of a cold temperature isotherm showing the network of small-scale convection.

  11. Nonlinear Convection in Mushy Layers

    NASA Technical Reports Server (NTRS)

    Worster, M. Grae; Anderson, Daniel M.; Schulze, T. P.

    1996-01-01

    When alloys solidify in a gravitational field there are complex interactions between solidification and natural, buoyancy-driven convection that can alter the composition and impair the structure of the solid product. The particular focus of this project has been the compositional convection within mushy layers that occurs in situations where the lighter component of the alloy is rejected into the melt during solidification by cooling from below. The linear stability of such a situation was previously described and has been further elucidated in a number of published articles. Here we describe some recent developments in the study of nonlinear evolution of convection in mushy layers.

  12. Multiscale Precipitation Processes Over Mountain Terrain - Landform and Vegetation Controls of Microphysics and Convection in Complex Terrain

    NASA Astrophysics Data System (ADS)

    Barros, A. P.; Wilson, A. M.; Sun, X.; Duan, Y.

    2015-12-01

    Recent precipitation observations in mountainous regions do not exhibit the classical orographic enhancement with elevation, especially where fog and multi-layer clouds are persistent. The role of landform in modulating moisture convergence patterns and constraining the thermodynamic environment that supports the development of complex vertical structures of clouds and precipitation is discussed first using observations and model results from the IPHEx (Integrated Precipitation and Hydrology Experiment) field campaign in the Southern Appalachian Mountains (SAM). Analysis of the complex spatial heterogeneity of precipitation microphysics in the SAM suggests that seeder-feeder interactions (SFI) among stratiform precipitation, low level clouds (LLC), and fog play a governing role on the diurnal and seasonal cycles of observed precipitation regimes. Further, in the absence of synoptic-scale forcing, results suggest that evapotranspiration makes a significant contribution to the moisture budget in the lower atmosphere, creating super-saturation conditions favorable to CCN activation, LLC formation, and light rainfall. To investigate the role of evapotranspiration on the diurnal cycle of mountain precipitation further, range-scale modeling studies were conducted in the Central Andes. Specifically, high resolution WRF simulations for realistic and quasi-idealized ET withdrawal case-studies show that evapotranspiration fluxes modulated by landform govern convective activity in the lower troposphere, including cloud formation and precipitation processes that account for daily precipitation amounts as high as 50-70% depending on synoptic conditions and season. These studies suggest multiscale vegetation controls of orographic precipitation processes via atmospheric instability on the one hand, and low level super-saturation and local microphysics on the other. A conceptual model of multiscale interactions among vegetation, landform and moist processes over complex

  13. On the impact of spatial heterogeneous permeability distributions on the development of free convection cells in the Perth Basin, Australia.

    NASA Astrophysics Data System (ADS)

    Niederau, Jan; Ebigbo, Anozie; Freitag, Sebastian; Marquart, Gabriele; Clauser, Christoph

    2014-05-01

    Recent increase in exploration of the geothermal energy potential of the Perth Metropolitan Area (PMA) results in the need for reliable and robust reservoir models in order to explore rock properties and temperature distributions in the subsurface, where free convection in the main reservoir (Yarragadee Aquifer) is likely to occur [1]. While the structure of the Perth Basin has been refined recently, the heterogeneity and spatial complexity of permeability was up till now mainly neglected. An integrated, three dimensional tectonostratigraphic model of the PMA is constructed, using the modeling software '3D GeoModeller' and data of numerous artesian and petroleum wells. Comprising the region around the city of Perth, the model covers an area of about 5000 km2 up to a depth of 4.5 km, with focus on adequate representation of the main reservoir. We further construct a numerical model for fluid flow and heat transport in the Yarragadee Aquifer. Porosity distributions are deduced from well logs and linked to permeability by a calibrated correlation, based on a fractal approach. Three different cases are simulated using the FD code SHEMAT-Suite, in order to assess the influence of spatial heterogeneity of porosity and permeability on the development of free convection cells. constant porosity and permeability for the entire aquifer porosity and permeability decreasing with depth, thus reflecting compaction a conditional random permeability field within prescribed limits and for given correlation length In order to improve understanding of model correctness, as well as identification and comparison of convection cells in different simulations, we are developing a specialized visualization tool tailored to this purpose. The three different scenarios show distinctions in the distribution of convection cells. Where the Yarragadee Aquifer is in contact with overlying aquifers, regions of downflow develop. These in turn have a strong impact on the regional flow field and

  14. Development of a Mantle Convection Physical Model to Assist with Teaching about Earth's Interior Processes

    NASA Astrophysics Data System (ADS)

    Glesener, G. B.; Aurnou, J. M.

    2010-12-01

    The Modeling and Educational Demonstrations Laboratory (MEDL) at UCLA is developing a mantle convection physical model to assist educators with the pedagogy of Earth’s interior processes. Our design goal consists of two components to help the learner gain conceptual understanding by means of visual interactions without the burden of distracters, which may promote alternative conceptions. Distracters may be any feature of the conceptual model that causes the learner to use inadequate mental artifact to help him or her understand what the conceptual model is intended to convey. The first component, and most important, is a psychological component that links properties of “everyday things” (Norman, 1988) to the natural phenomenon, mantle convection. Some examples of everyday things may be heat rising out from a freshly popped bag of popcorn, or cold humid air falling from an open freezer. The second component is the scientific accuracy of the conceptual model. We would like to simplify the concepts for the learner without sacrificing key information that is linked to other natural phenomena the learner will come across in future science lessons. By taking into account the learner’s mental artifacts in combination with a simplified, but accurate, representation of what scientists know of the Earth’s interior, we expect the learner to have the ability to create an adequate qualitative mental simulation of mantle convection. We will be presenting some of our prototypes of this mantle convection physical model at this year’s poster session and invite constructive input from our colleagues.

  15. Grey zone simulations of the morning convective boundary layer development

    NASA Astrophysics Data System (ADS)

    Efstathiou, G. A.; Beare, R. J.; Osborne, S.; Lock, A. P.

    2016-05-01

    Numerical simulations of two cases of morning boundary layer development are conducted to investigate the impact of grid resolution on mean profiles and turbulent kinetic energy (TKE) partitioning from the large eddy simulation (LES) to the mesoscale limit. Idealized LES, using the 3-D Smagorinsky scheme, is shown to be capable of reproducing the boundary layer evolution when compared against measurements. However, increasing grid spacing results in the damping of resolved TKE and the production of superadiabatic temperature profiles in the boundary layer. Turbulence initiation is significantly delayed, exhibiting an abrupt onset at intermediate resolutions. Two approaches, the bounding of vertical diffusion coefficient and the blending of the 3-D Smagorinsky with a nonlocal 1D scheme, are used to model subgrid diffusion at grey zone resolutions. Simulations are compared against the coarse-grained fields from the validated LES results for each case. Both methods exhibit particular strengths and weaknesses, indicating the compromise that needs to be made currently in high-resolution numerical weather prediction. The blending scheme is able to reproduce the adiabatic profiles although turbulence is underestimated in favor of the parametrized heat flux, and the spin-up of TKE remains delayed. In contrast, the bounding approach gives an evolution of TKE that follows the coarse-grained LES very well, relying on the resolved motions for the nonlocal heat flux. However, bounding gives unrealistic static instability in the early morning temperature profiles (similar to the 3-D Smagorinsky scheme) because model dynamics are unable to resolve TKE when the boundary layer is too shallow compared to the grid spacing.

  16. High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin

    NASA Astrophysics Data System (ADS)

    Gerken, T.; Babel, W.; Herzog, M.; Fuchs, K.; Sun, F.; Ma, Y.; Foken, T.; Graf, H.-F.

    2015-09-01

    The Tibetan Plateau plays a significant role in atmospheric circulation and the Asian monsoon system. Turbulent surface fluxes and the evolution of boundary-layer clouds to deep and moist convection provide a feedback system that modifies the plateau's surface energy balance on scales that are currently unresolved in mesoscale models. This work analyses the land surface's role and specifically the influence of soil moisture on the triggering of convection at a cross section of the Nam Co Lake basin, 150 km north of Lhasa using a cloud-resolving atmospheric model with a fully coupled surface. The modelled turbulent fluxes and development of convection compare reasonably well with the observed weather. The simulations span Bowen ratios of 0.5 to 2.5. It is found that convective development is the strongest at intermediate soil moisture. Dry cases with soils close to the permanent wilting point are moisture limited in convective development, while convection in wet soil moisture cases is limited by cloud cover reducing incoming solar radiation and sensible heat fluxes, which has a strong impact on the surface energy balance. This study also shows that local development of convection is an important mechanism for the upward transport of water vapour, which originates from the lake basin that can then be transported to dryer regions of the plateau. Both processes demonstrate the importance of soil moisture and surface-atmosphere interactions on the energy and hydrological cycles of the Tibetan Plateau.

  17. High-resolution modelling of interactions between soil moisture and convection development in mountain enclosed Tibetan basin

    NASA Astrophysics Data System (ADS)

    Gerken, T.; Babel, W.; Herzog, M.; Fuchs, K.; Sun, F.; Ma, Y.; Foken, T.; Graf, H.-F.

    2015-05-01

    The Tibetan Plateau plays a significant role in the atmospheric circulation and the Asian monsoon system. Turbulent surface fluxes and the evolution of boundary layer clouds to deep and moist convection provide a feedback system that modifies the Plateau's surface energy balance on scales that are currently unresolved in mesoscale models. This work analyses the land surface's role and specifically the influence of soil moisture on the triggering of convection at a cross-section of the Nam Co Lake basin, 150 km north of Lhasa using a cloud resolving atmospheric model with a fully coupled surface. The modelled turbulent fluxes and development of convection compare reasonably well with the observed weather. The simulations span Bowen-ratios of 0.5 to 2.5. It is found that convection development is strongest at intermediate soil moistures. Dry cases with soils close to the permanent wilting point are moisture limited in the convection development, while convection in wet soil moisture cases is limited by cloud cover reducing incoming solar radiation and sensible heat fluxes. This has a strong impact on the surface energy balance. This study also shows that local development of convection is an important mechanism for the upward transport of water vapour that originates from the lake basin that can then be transported to dryer regions of the plateau. Both processes demonstrate the importance of soil moisture and surface-atmosphere interactions on the energy and hydrological cycles of the Tibetan Plateau.

  18. Development of convective testing methods for low-rise multifamily buildings. Final report

    SciTech Connect

    Stiles, M.R.

    1996-08-01

    This report describes convective testing methods and protocols developed for use in weatherizing low-rise multifamily buildings. The methods can lead to controlling internal air movement and preventing leakage to the exterior by estimating magnitudes of air leakage pathways in garden and town house apartments. The 4 methods cited are: After-a-Retrofit; Equivalent Interfaces; Open-a-Door; and Add-a-Pathway. It is found that, because of modern interior finishing practices, convective problems tend to be more associated with indoor air quality than loss of space conditioning energy. The After-a-Retrofit method is the easiest to integrate into current diagnostic practices. In some cases, the Equivalent Interfaces method may be used on a production basis. The methods are an advance on current field practices that do not quantify the leakage pathways and research practices that require extensive equipment.

  19. Development of a Convection Risk Index to forecast severe weather, and application to predict maximum wind speeds

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. A. E.; Wanik, D. W.; Scerbo, D.; Anagnostou, E. N.

    2015-12-01

    We have developed a tool, the Convection Risk Index (CRI), to represent the severity, timing and location of convection for select geographic areas. The CRI is calculated from the Convection Risk Matrix (CRM), a tabulation of numerous meteorological parameters which are categorized into four broad factors that contribute to convection (surface and lower level moisture, atmospheric instability, vertical wind shear, and lift); each of these factors have historically been utilized by meteorologists to predict the likelihood for development of thunderstorms. The CRM ascribes a specific threshold value to each parameter in such a way that it creates a unique tool used to calculate the risk for seeing the development of thunderstorms. The parameters were combined using a weighted formula and which when calculated, yields the Convection Risk Index 1 to 4 scale, with 4 being the highest risk for seeing strong convection. In addition, we also evaluated the performance of the parameters in the CRM and CRI for predicting the maximum wind speed in areas where we calculated the CRI using nonparametric tree-based model, Bayesian additive trees (BART). The use of the CRI and the predicted wind speeds from BART can be used to better inform emergency preparedness efforts in government and industry.We have developed a tool, the Convection Risk Index (CRI), to represent the severity, timing and location of convection for select geographic areas. The CRI is calculated from the Convection Risk Matrix (CRM), a tabulation of numerous meteorological parameters which are categorized into four broad factors that contribute to convection (surface and lower level moisture, atmospheric instability, vertical wind shear, and lift); each of these factors have historically been utilized by meteorologists to predict the likelihood for development of thunderstorms. The CRM ascribes a specific threshold value to each parameter in such a way that it creates a unique tool used to calculate the risk for

  20. Contrasting a non-developing African mesoscale convective system with the precursor to Hurricane Helene (2006)

    NASA Astrophysics Data System (ADS)

    Rivera, G.; Fuentes, J. D.; Evans, J. L.; Hamilton, H. L.

    2015-12-01

    Mesoscale convective systems (MCSs) in West Africa traverse strong thermodynamic gradients during their westward propagation from land to ocean. Some of the systems continue to develop after crossing the coastline and may ultimately develop into tropical cyclones, while others do not. Understanding the lifecycle behavior of these convective systems and the factors that contribute to their continuous development as they transition from a continental environment to a marine environment poses a challenge. We examine the difference between two MCSs, one that continued to develop when it crossed the West African coast and one that did not, using European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA Interim) and Tropical Rainfall Measurement Mission (TRMM) 3B42 data. The non-developing MCS that intensified briefly while over land, weakened as soon as it crossed the coast. Preliminary results show that the developing MCS interacted with two cyclonic vortices, one associated with an African Easterly Wave that was propagating towards the coast and the other vortex generated by the topography near the coast.

  1. Propagation of Convective Complexes Observed by TRMM in the Eastern Tropical Atlantic

    NASA Technical Reports Server (NTRS)

    Druyan, Leonard M.; Fulazeka, Matthew

    2012-01-01

    Precipitation maxima during the West African summer monsoon propagate generally westward in tandem with African easterly waves. A heretofore unreported, repeating pattern of northward drift of precipitation maxima is detected on Tropical Rainfall Measurement Mission (TRMM satellite) time-latitude distributions of daily accumulations over the eastern tropical Atlantic. Corresponding 3-hourly TRMM accumulations show that the northward drifting envelopes of precipitation during August 2006 are often comprised of individual swaths propagating towards the southwest, presumably as mesoscale squall lines. The implied northward drift on the time-latitude distribution is a component of a resultant northwestward movement. The study examines the entire available record of TRMM precipitation observations, 1998-2010, to summarize TRMM maxima propagation over the eastern tropical Atlantic. Meridional displacements of precipitation maxima are most prevalent in June-September 2006, occurring less frequently during other summers. An investigation of geopotential and circulation fields, limited to two case studies, suggests mechanisms to explain some of the observed propagation of TRMM maxima. In one event, northward drift of the precipitation envelope is consistent with the corresponding displacement of the intertropical convergence zone trough, although the southwest propagation of individual mesoscale convection maxima does not correspond to any synoptic feature on reanalysis circulation or reanalysis downscaled by a regional model. One speculation is that southwestward propagation of precipitation maxima could be caused by regeneration of convection at outflow boundaries of mature thunderstorms.

  2. Development of the Rice Convection Model as a Space Weather Tool

    DTIC Science & Technology

    2015-05-31

    Air Force Research Laboratory Space Vehicles Directorate 3550 Aberdeen Ave SE Kirtland AFB, NM 87117-5776 10. SPONSOR/MONITOR’S ACRONYM(S) AFRL ...unlimited. 9 DISTRIBUTION LIST DTIC/OCP 8725 John J. Kingman Rd, Suite 0944 Ft Belvoir, VA 22060-6218 1 cy AFRL /RVIL Kirtland AFB, NM... AFRL -RV-PS- AFRL -RV-PS- TR-2015-0129 TR-2015-0129 DEVELOPMENT OF THE RICE CONVECTION MODEL AS A SPACE WEATHER TOOL Frank R. Toffoletto, et al

  3. 'Electrically-Hot' Convection and Tropical Cyclone Development in the Eastern Atlantic

    NASA Technical Reports Server (NTRS)

    Leppert, Kenneth, II; Petersen, Walter A.; Williams, Earle

    2008-01-01

    The depth and intensity of convective-scale "hot" towers in intensifying tropical disturbances has been hypothesized to play a role in tropical cyclogenesis via dynamic and thermodynamic feedbacks on the larger meso-to-synoptic scale circulation. In this investigation we investigate the role that widespread and/or intense lightning-producing convection (i.e., "electrically-hot towers") resident in African Easterly Waves (AEW) may play in tropical cyclogenesis over the eastern Atlantic Ocean. NCEP reanalysis data for the months of July to November for the years 2004, 2006, and 2007 are analyzed for the domain of 5 N - 15 N and 500W - 300 E. Specifically, NCEP data for individual AEWs are partitioned into northerly, southerly, trough, and ridge phases using the 700 hPa meridional winds. Subsequently, information from National Hurricane Center storm reports were divided up into developing and non-developing waves (i.e. tropical cyclogenesis). Finally, composites were created of developing and non-developing waves using the NCEP variables, but with the inclusion of lightning flash count and infrared brightness temperature information. The Zeus and World Wide Lightning Location Network lightning data were used for the lightning information, and the IR brightness temperature data was extracted from the NASA global-merged infrared brightness temperature dataset.

  4. 'Electrically-Hot' Convection and Tropical Cyclone Development in the Eastern Atlantic

    NASA Technical Reports Server (NTRS)

    Leppert, Kenneth, II; Petersen, Walter A.; Williams, Earle

    2008-01-01

    The depth and intensity of convective-scale "hot" towers in intensifying tropical disturbances has been hypothesized to play a role in tropical cyclogenesis via dynamic and thermodynamic feedbacks on the larger meso-to-synoptic scale circulation. In this investigation we investigate the role that widespread and/or intense lightning-producing convection (i.e., "electrically-hot towers") resident in African Easterly Waves (AEW) may play in tropical cyclogenesis over the eastern Atlantic Ocean. NCEP reanalysis data for the months of July to November for the years 2004, 2006, and 2007 are analyzed for the domain of 5 N - 15 N and 500W - 300 E. Specifically, NCEP data for individual AEWs are partitioned into northerly, southerly, trough, and ridge phases using the 700 hPa meridional winds. Subsequently, information from National Hurricane Center storm reports were divided up into developing and non-developing waves (i.e. tropical cyclogenesis). Finally, composites were created of developing and non-developing waves using the NCEP variables, but with the inclusion of lightning flash count and infrared brightness temperature information. The Zeus and World Wide Lightning Location Network lightning data were used for the lightning information, and the IR brightness temperature data was extracted from the NASA global-merged infrared brightness temperature dataset.

  5. Effect of convective transport in porous media on the conditions of organic matter maturation and generation of hydrocarbons in trap rocks complexes

    NASA Astrophysics Data System (ADS)

    Yurie Khachay, Professor; Mindubaev, Mansur

    2016-04-01

    One of the main problems of the study of the intrusion thermal effects on the maturation of the organic matter is to estimate the volume, intensity, thermal effects of the intrusion and its redistribution in porous media by convection. A numerical algorithm for solving the problem of the developed convection in two-dimensional and three-dimensional models of the porous medium depending on the incline angle is developed. It is defined that the convective stability in the medium decreases with increasing incline angle. It was found that depending on the incline angle the structure of convection from many cells for a flat horizontal layer changes and it transfers to more elongated structures along the layer. It is shown that depending on the incline angles, invading sill and imbedding volume of the porous medium it can be realized either stationary or non-stationary convection that provides a principal different thermal conditions of hydrocarbons maturation in the motherboard porous medium. We give numerical examples of the influence of the incline angle on the flow structure inside the porous inclusion. By the stationary convection the volume of the boundary layers between the convective sells increases. That can lead to increasing of the part of motherboard rocks that are outer the temperature conditions of oil catalysis and as a consequence to the overestimation of the deposits.

  6. Effects of anisotropy and fabric development on convection in ice Ih mantles

    NASA Astrophysics Data System (ADS)

    Rudolph, M. L.; Manga, M.

    2011-12-01

    We study the effects of fabric development on convection in Ice I mantles using a new numerical model. In order to simulate the effect of texture development, we coupled a model for polycrystal deformation that incorporates dislocation creep on basal planes, grain boundary sliding, and diffusion creep with a macroscopic mantle flow model. Texture is tracked on tracer particles and allowed to evolve. Coupling between the microscopic and macroscopic models is two-way: macroscopic strain induces changes in crystallographic preferred orientation (CPO) on microscopic scales, and the anisotropic response of polycrystalline ice affects the macroscopic rheological behavior. We present results from two-dimensional simulations in which we allow texture to evolve and contrast these results with simulations in which ice remains isotropic. Surface features described as pits and domes on Europa may be manifestations of convection in Europa's predominantly water-ice mantle. We compare our model results with observed topography with the aim of understanding whether fabric development can explain discrepancies between the observed topography and predictions from previous models.

  7. An aircraft study of rapid precipitation development and electrification in a growing convective cloud

    NASA Astrophysics Data System (ADS)

    Willis, P. T.; Hallett, J.; Black, R. A.; Hendricks, W.

    The rapid initial precipitation growth and initial electrification of a convective cloud, growing as a new cell on the upshear side of a cloud system in Florida, is traced from radar data and aircraft penetrations at the -7°C to -10°C level. This study combines radar, microphysical and electrical measurements so that an examination of the interactions between the cloud dynamics, microphysics and electrification is possible. The first pass (-7°C) was characterized by a strong 23 m/s updraft, all liquid cloud water, no precipitation, and no significant electrification. In the 300 s between the two penetrations, precipitation developed very rapidly from < 15 dBZ to < 45 dBZ, and the vertical component of the electric field increased from below the measurement threshold to - 25 kv/m. The second penetration, which started at - 7°C and ended at - 10°C, was still exclusively updraft, but with lesser peak velocities and a more complex structure; i.e., no downdraft, but with relative minima in the updraft. The microphysics of the second pass displayed a segment of exclusively cloud liquid water (no precipitation size hydrometeors), a small segment of all liquid precipitation size hydrometeors, a small region of mixed hydrometeors and an extensive region of graupel hydrometeors, ranging in size from 100 μm to several mm. High cloud liquid water coexisted with the liquid and graupel hydrometeors in the strong updrafts. The electrification was observed to occur exclusively in the segments of the cloud pass where graupel were observed. Within this graupel region, where the graupel often coexisted with supercooled cloud liquid water, significant electric field occurred only at relative minima in the updraft. These relative velocity minima were also minima in the cloud liquid water content. The observed updraft velocities in these relative minima were close to balance velocities for the observed larger graupel hydrometeors. The strongest updrafts, where the formation and

  8. Evaluating and Understanding Parameterized Convective Processes and their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael; Kain, John S.

    1997-01-01

    Research efforts during the second year have centered on improving the manner in which convective stabilization is achieved in the Penn State/NCAR mesoscale model MM5. Ways of improving this stabilization have been investigated by (1) refining the partitioning between the Kain-Fritsch convective parameterization scheme and the grid scale by introducing a form of moist convective adjustment; (2) using radar data to define locations of subgrid-scale convection during a dynamic initialization period; and (3) parameterizing deep-convective feedbacks as subgrid-scale sources and sinks of mass. These investigations were conducted by simulating a long-lived convectively-generated mesoscale vortex that occurred during 14-18 Jul. 1982 and the 10-11 Jun. 1985 squall line that occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. The long-lived vortex tracked across the central Plains states and was responsible for multiple convective outbreaks during its lifetime.

  9. Specialized software for modelling of convection in microgravity

    NASA Astrophysics Data System (ADS)

    Ermakov, M. K.; Grjaznov, V. L.; Nikitin, S. A.; Pavlovsky, D. S.; Poleshaev, V. I.

    The paper contains a short description of special dialog system for study of convective processes on the basis of the unsteady Navier-Stokes equations developed in the Institute for Problems in Mechanics USSR Academy of Science. This is a desktop scientific analysis program for both beginning and experienced scientists. Several examples of tests and analysis of complex convective processes are discussed.

  10. Stochastic Convection Parameterizations

    NASA Technical Reports Server (NTRS)

    Teixeira, Joao; Reynolds, Carolyn; Suselj, Kay; Matheou, Georgios

    2012-01-01

    computational fluid dynamics, radiation, clouds, turbulence, convection, gravity waves, surface interaction, radiation interaction, cloud and aerosol microphysics, complexity (vegetation, biogeochemistry, radiation versus turbulence/convection stochastic approach, non-linearities, Monte Carlo, high resolutions, large-Eddy Simulations, cloud structure, plumes, saturation in tropics, forecasting, parameterizations, stochastic, radiation-clod interaction, hurricane forecasts

  11. The Development of Geo-KOMPSAT-2A (GK-2A) Convective Initiation Algorithm over the Korea peninsular

    NASA Astrophysics Data System (ADS)

    Kim, H. S.; Chung, S. R.; Lee, B. I.; Baek, S.; Jeon, E.

    2016-12-01

    The rapid development of convection can bring heavy rainfall that suffers a great deal of damages to society as well as threatens human life. The high accurate forecast of the strong convection is essentially demanded to prevent those disasters from the severe weather. Since a geostationary satellite is the most suitable instrument for monitoring the single cloud's lifecycle from its formation to extinction, it has been attempted to capture the precursor signals of convection clouds by satellite. Keeping pace with the launch of Geo-KOMPSAT-2A (GK-2A) in 2018, we planned to produce convective initiation (CI) defined as the indicator of potential cloud objects to bring heavy precipitation within two hours. The CI algorithm for GK-2A is composed of four stages. The beginning is to subtract mature cloud pixels, a sort of convective cloud mask by visible (VIS) albedo and infrared (IR) brightness temperature thresholds. Then, the remained immature cloud pixels are clustered as a cloud object by watershed techniques. Each clustering object is undergone 'Interest Fields' tests for IR data that reflect cloud microphysical properties at the current and their temporal changes; the cloud depth, updraft strength and production of glaciations. All thresholds of 'Interest fields' were optimized for Korean-type convective clouds. Based on scores from tests, it is decided whether the cloud object would develop as a convective cell or not. Here we show the result of case study in this summer over the Korea peninsular by using Himawari-8 VIS and IR data. Radar echo and data were used for validation. This study suggests that CI products of GK-2A would contribute to enhance accuracy of the very short range forecast over the Korea peninsular.

  12. Influence of Offshore Initial Moisture Field and Convection on the Development of Coastal Convection in a Heavy Rainfall Event over South China during the Pre-summer Rainy Season

    NASA Astrophysics Data System (ADS)

    Lu, Rong; Sun, Jianhua; Fu, Shenming

    2017-04-01

    This paper utilizes the observation data from the Southern China Monsoon Rainfall Experiment (SCMREX) and the numerical experiments to investigate the influence of moisture amount and convection development over the northern South China Sea on a heavy rainfall event in coastal South China on May 8, 2014. Intensive sounding and wind profiles data reveal that there existed a convergence region formed by the southwesterly and easterly jet in the Pearl River delta, which provided favorable conditions for the development of convection. Whether the initial relative humidity field was increased or decreased in the offshore area, or turning off sensible and latent heat release from the cumulus and microphysical processes, had significant effects on the intensity and movement of convection in the coastal areas of Guangdong owing to the adjustment of temperature and wind fields. Especially, when increasing offshore initial humidity, prosperous sea convection modified the circulation in the entire simulation area, and suppressed the development of convection over land. Moreover, if sensible and latent heat from cumulus and microphysical processes was turned off, the low-level jets could reach further north, and the convective system moved to the northeast in the later stage. These experiments indicate that offshore initial moisture filed and convection activity are indeed important for precipitation forecast in the coastal areas, therefore it's necessary to enhance offshore observation and data assimilation methods in the future.

  13. Holocene Development of Greenland Sea Deep Convection: A Comparison of Calcite Surface and Bottom Water δ13c

    NASA Astrophysics Data System (ADS)

    Bauch, H. A.; Telesinski, M. M.; Spielhagen, R. F.

    2014-12-01

    The northern polar oceans are a crucially important region to understand the overturning circulation of the North Atlantic within the context of glacial-interglacial climate change. Independent of different water mass properties planktic carbon isotope records (13C/12C) from across the Nordic Seas show a rather consistent pattern over the course of the Holocene. We present data from a number of sediment cores obtained in the central Nordic Seas which show that carbon isotope values were increasing since the early Holocene. They reached a maximum level between 7 and 6 ka and remained relatively stable thereafter. Ca. 3 ka they rapidly decreased. Benthic carbon isotope records from the central Nordic Seas, close to the present-day convection center of the Greenland Sea, reveal a similar trend as the planktic records. Although of lower amplitude, these bottom water data reflect the development of the regional deep convection in this region. A comparison with other proxy records and modelling results supports this presumption. While the early to late Holocene trend apparently reflect the developing deep convection after the last glacial period, the sudden decrease in the convection strength around 3 ka was most probably triggered by a strong solar irradiance minimum. This, combined with low insolation, caused an expansion of the sea ice over the convection center and enhanced stratification, thereby strengthening the entire halocline system.

  14. A Generalized Simple Formulation of Convective Adjustment Timescale for Cumulus Convection Parameterizations

    EPA Science Inventory

    Convective adjustment timescale (τ) for cumulus clouds is one of the most influential parameters controlling parameterized convective precipitation in climate and weather simulation models at global and regional scales. Due to the complex nature of deep convection, a pres...

  15. Development of a new device to measure local heat exchange by evaporation and convection.

    PubMed

    Kakitsuba, N; Katsuura, T

    1992-06-01

    According to the principles of heat and mass transfer, the rate of local heat exchange by convection (C) and local heat loss by evaporation (E) can be estimated if temperature and vapor concentration profiles in the boundary layer are measured. In addition, temperature (Ts) and vapor concentration (rho s) at the surface may be predicted from the measured profiles. On this basis, a new device was developed to measure parabolic profiles by incorporating three relative humidity sensors coupled with thermistors into its probe. It has been evaluated from various tests including human experiments. The results showed that the device, with humidity sensors arranged perpendicular to the surface, could estimate C, E, Ts, and rho s in closer agreement with direct measurements when compared with the conventional gradient method. This confirmed that our method had clear advantages over the conventional gradient method under laminar air flow conditions.

  16. Effects of corrugation angle on developing laminar forced convection and entropy generation in a wavy channel

    NASA Astrophysics Data System (ADS)

    Ko, Tzu-Hsiang

    2007-12-01

    This paper investigates the effects of corrugation angle ( β) on the developing laminar forced convection and entropy generation in a wavy channel with numerical methods. The studied cases cover β = 10-, 15-, 20-, 25-, 30- and 35°, whilst Reynolds number ( Re) is varied as 100, 200 and 400. The analyzed flow characteristics include recirculating flows, secondary vortices, temperature distributions, and friction factor as well as Nusselt number. In particular, the effects of corrugation angle on the distributions and magnitudes of local entropy generation resulted from frictional irreversibility ( S {/P '''}) and heat transfer irreversibility ( S {/T '''}) are separately discussed in detail in the present paper. Based on the minimal entropy generation principle, the optimal corrugation angle and favorable Re are reported.

  17. Development of a laser-induced heat flux technique for measurement of convective heat transfer coefficients in a supersonic flowfield

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Keith, Theo G., Jr.; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.

    1991-01-01

    A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the load surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimental results agreed reasonably well with theoretical predictions of convective heat transfer of flat plate laminar boundary layers. The results indicate that this non-intrusive optical measurement technique has the potential to obtain high quality surface convective heat transfer measurements in high speed flowfields.

  18. Mantle convection on modern supercomputers

    NASA Astrophysics Data System (ADS)

    Weismüller, Jens; Gmeiner, Björn; Mohr, Marcus; Waluga, Christian; Wohlmuth, Barbara; Rüde, Ulrich; Bunge, Hans-Peter

    2015-04-01

    Mantle convection is the cause for plate tectonics, the formation of mountains and oceans, and the main driving mechanism behind earthquakes. The convection process is modeled by a system of partial differential equations describing the conservation of mass, momentum and energy. Characteristic to mantle flow is the vast disparity of length scales from global to microscopic, turning mantle convection simulations into a challenging application for high-performance computing. As system size and technical complexity of the simulations continue to increase, design and implementation of simulation models for next generation large-scale architectures demand an interdisciplinary co-design. Here we report about recent advances of the TERRA-NEO project, which is part of the high visibility SPPEXA program, and a joint effort of four research groups in computer sciences, mathematics and geophysical application under the leadership of FAU Erlangen. TERRA-NEO develops algorithms for future HPC infrastructures, focusing on high computational efficiency and resilience in next generation mantle convection models. We present software that can resolve the Earth's mantle with up to 1012 grid points and scales efficiently to massively parallel hardware with more than 50,000 processors. We use our simulations to explore the dynamic regime of mantle convection assessing the impact of small scale processes on global mantle flow.

  19. Mantle Convection on Modern Supercomputers

    NASA Astrophysics Data System (ADS)

    Weismüller, J.; Gmeiner, B.; Huber, M.; John, L.; Mohr, M.; Rüde, U.; Wohlmuth, B.; Bunge, H. P.

    2015-12-01

    Mantle convection is the cause for plate tectonics, the formation of mountains and oceans, and the main driving mechanism behind earthquakes. The convection process is modeled by a system of partial differential equations describing the conservation of mass, momentum and energy. Characteristic to mantle flow is the vast disparity of length scales from global to microscopic, turning mantle convection simulations into a challenging application for high-performance computing. As system size and technical complexity of the simulations continue to increase, design and implementation of simulation models for next generation large-scale architectures is handled successfully only in an interdisciplinary context. A new priority program - named SPPEXA - by the German Research Foundation (DFG) addresses this issue, and brings together computer scientists, mathematicians and application scientists around grand challenges in HPC. Here we report from the TERRA-NEO project, which is part of the high visibility SPPEXA program, and a joint effort of four research groups. TERRA-NEO develops algorithms for future HPC infrastructures, focusing on high computational efficiency and resilience in next generation mantle convection models. We present software that can resolve the Earth's mantle with up to 1012 grid points and scales efficiently to massively parallel hardware with more than 50,000 processors. We use our simulations to explore the dynamic regime of mantle convection and assess the impact of small scale processes on global mantle flow.

  20. Thermo-electro-hydrodynamic convection under microgravity: a review

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Yoshikawa, Harunori N.; Tadie Fogaing, Mireille; Travnikov, Vadim; Crumeyrolle, Olivier; Futterer, Birgit; Egbers, Christoph

    2016-12-01

    Recent studies on thermo-electro-hydrodynamic (TEHD) convection are reviewed with focus on investigations motivated by the analogy with natural convection. TEHD convection originates in the action of the dielectrophoretic force generated by an alternating electric voltage applied to a dielectric fluid with a temperature gradient. This electrohydrodynamic force is analogous to Archimedean thermal buoyancy and can be regarded as a thermal buoyancy force in electric effective gravity. The review is concerned with TEHD convection in plane, cylindrical, and spherical capacitors under microgravity conditions, where the electric gravity can induce convection without any complexities arising from geometry or the buoyancy force due to the Earth’s gravity. We will highlight the convection in spherical geometry, comparing developed theories and numerical simulations with the GEOFLOW experiments performed on board the International Space Station (ISS).

  1. Heat enhanced by an exothermic reaction on a fully developed MHD mixed convection flow in a vertical channel

    NASA Astrophysics Data System (ADS)

    Jayabalan, C.; Sivagnana Prabhu, K. K.; Kandasamy, R.

    2016-09-01

    The problem of a fully developed MHD mixed convection flow in a vertical channel with the first-order chemical reaction is analyzed. The dimensionless governing ordinary differential equations are solved numerically by using the Maple 18 software. It is observed that dual solutions exist for both velocity and temperature.

  2. The interactive role of subsynoptic scale jet sreak and planetary boundary layer adjustments in organizing an apparently isolated convective complex

    NASA Technical Reports Server (NTRS)

    Kaplan, M. L.; Zack, J. W.; Wong, V. C.; Tuccillo, J. J.; Coats, G. D.

    1982-01-01

    A mesoscale atmospheric simulation system is described that is being developed in order to improve the simulation of subsynoptic and mesoscale adjustments associated with cyclogenesis, severe storm development, and significant atmospheric transport processes. Present emphasis in model development is in the parameterization of physical processes, time-dependent boundary conditions, sophisticated initialization and analysis procedures, nested grid solutions, and applications software development. Basic characteristics of the system as of March 1982 are listed. In a case study, the Grand Island tornado outbreak of 3 June 1980 is considered in substantial detail. Results of simulations with a mesoscale atmospheric simulation system indicate that over the high plains subtle interactions between existing jet streaks and deep well mixed boundary layers can lead to well organized patterns of mesoscale divergence and pressure falls. The amplitude and positioning of these mesoscale features is a function of the subtle nonlinear interaction between the pre-existing jet-streak and deep well mixed boundary layers. Model results for the case study indicate that the model has the potential for forecasting the precursor mesoscale convective environment.

  3. Tropical Cyclogenesis Initiated by Lee Vortices and Mesoscale Convective Complexes in East Africa

    DTIC Science & Technology

    2003-09-30

    will cover the width of the African continent, using a grid resolution of 30 km. Several sensitivity tests will be performed to help find the necessary...based on a statistical study of upper air observations from Khartoum, Sudan, Burpee (1972) argued that the African easterly waves do not develop

  4. Progress in developing the ASPECT Mantle Convection Code - New Features, Benchmark Comparisons and Applications

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Bangerth, Wolfgang; Sobolev, Stephan

    2014-05-01

    Since there is no direct access to the deep Earth, numerical simulations are an indispensible tool for exploring processes in the Earth's mantle. Results of these models can be compared to surface observations and, combined with constraints from seismology and geochemistry, have provided insight into a broad range of geoscientific problems. In this contribution we present results obtained from a next-generation finite-element code called ASPECT (Advanced Solver for Problems in Earth's ConvecTion), which is especially suited for modeling thermo-chemical convection due to its use of many modern numerical techniques: fully adaptive meshes, accurate discretizations, a nonlinear artificial diffusion method to stabilize the advection equation, an efficient solution strategy based on a block triangular preconditioner utilizing an algebraic multigrid, parallelization of all of the steps above and finally its modular and easily extensible implementation. In particular the latter features make it a very versatile tool applicable also to lithosphere models. The equations are implemented in the form of the Anelastic Liquid Approximation with temperature, pressure, composition and strain rate dependent material properties including associated non-linear solvers. We will compare computations with ASPECT to common benchmarks in the geodynamics community such as the Rayleigh-Taylor instability (van Keken et al., 1997) and demonstrate recently implemented features such as a melting model with temperature, pressure and composition dependent melt fraction and latent heat. Moreover, we elaborate on a number of features currently under development by the community such as free surfaces, porous flow and elasticity. In addition, we show examples of how ASPECT is applied to develop sophisticated simulations of typical geodynamic problems. These include 3D models of thermo-chemical plumes incorporating phase transitions (including melting) with the accompanying density changes, Clapeyron

  5. Use of Geostationary Satellite Imagery to Estimate Convective Precipitation Over Complex Terrain in the Western United States.

    DTIC Science & Technology

    imagery when terrain influences were included. This technique may be useful for real-time estimates of convective precipitation amounts and has potential for application to flash flood forecasting in the western United States.

  6. Development of a convective diffusion model for lead pipe rigs operating in laminar flow.

    PubMed

    Cardew, P T

    2006-06-01

    As part of achieving lower lead standards water undertakers are utilising lead pipe rigs to quantify the benefit of treatment measures. A convective diffusion model is developed for lead pipe rigs operating in laminar flow, and applied to the three operating steps of flushing, sampling and stagnation. The model is used to determine the appropriate time-scales for each stage, and the sensitivity of the measure to variations in flow-rate. In contrast to rigs operating in turbulent flow the average lead observed leaving the pipe and that in the pipe, after a period of stagnation, are substantially different. Equations are derived for both, and take into account the residual distribution of lead left in the pipe after flushing. It is shown that the lead concentration observed leaving the pipe is well approximated by a single exponential term in contrast to the concentration within the pipe. Predictions are made on the residual lead concentration that can be achieved through flushing, and its dependence on flow-rate. The relevance of the laminar flow model to that in domestic lead pipes is discussed.

  7. Developments in convective heat transfer models featuring seamless and selected detail surfaces, employing electroless plating

    NASA Technical Reports Server (NTRS)

    Stalmach, C. J., Jr.

    1975-01-01

    Several model/instrument concepts employing electroless metallic skin were considered for improvement of surface condition, accuracy, and cost of contoured-geometry convective heat transfer models. A plated semi-infinite slab approach was chosen for development and evaluation in a hypersonic wind tunnel. The plated slab model consists of an epoxy casting containing fine constantan wires accurately placed at specified surface locations. An electroless alloy was deposited on the plastic surface that provides a hard, uniformly thick, seamless skin. The chosen alloy forms a high-output thermocouple junction with each exposed constantan wire, providing means of determining heat transfer during tunnel testing of the model. A selective electroless plating procedure was used to deposit scaled heatshield tiles on the lower surface of a 0.0175-scale shuttle orbiter model. Twenty-five percent of the tiles were randomly selected and plated to a height of 0.001-inch. The purpose was to assess the heating effects of surface roughness simulating misalignment of tiles that may occur during manufacture of the spacecraft.

  8. Comparison of Measured and WRF-LES Turbulence Statistics in a Real Convective Boundary Layer over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Rai, R. K.; Berg, L. K.; Kosovic, B.; Mirocha, J. D.; Pekour, M. S.; Shaw, W. J.

    2015-12-01

    Resolving the finest turbulent scales present in the lower atmosphere using numerical simulations helps to study the processes that occur in the atmospheric boundary layer, such as the turbulent inflow condition to the wind plant and the generation of the wake behind wind turbines. This work employs several nested domains in the WRF-LES framework to simulate conditions in a convectively driven cloud free boundary layer at an instrumented field site in complex terrain. The innermost LES domain (30 m spatial resolution) receives the boundary forcing from two other coarser resolution LES outer domains, which in turn receive boundary conditions from two WRF-mesoscale domains. Wind and temperature records from sonic anemometers mounted at two vertical levels (30 m and 60 m) are compared with the LES results in term of first and second statistical moments as well as power spectra and distributions of wind velocity. For the two mostly used boundary layer parameterizations (MYNN and YSU) tested in the WRF mesoscale domains, the MYNN scheme shows slightly better agreement with the observations for some quantities, such as time averaged velocity and Turbulent Kinetic Energy (TKE). However, LES driven by WRF-mesoscale simulations using either parameterization have similar velocity spectra and distributions of velocity. For each component of the wind velocity, WRF-LES power spectra are found to be comparable to the spectra derived from the measured data (for the frequencies that are accurately represented by WRF-LES). Furthermore, the analysis of LES results shows a noticeable variability of the mean and variance even over small horizontal distances that would be considered sub-grid scale in mesoscale simulations. This observed statistical variability in space and time can be utilized to further analyze the turbulence quantities over a heterogeneous surface and to improve the turbulence parameterization in the mesoscale model.

  9. Compositional convection in viscous melts

    NASA Astrophysics Data System (ADS)

    Tait, Stephen; Jaupart, Claude

    1989-04-01

    DURING solidification of multi-component melts, gradients in temperature and composition develop on different scales because of the large difference between their respective molecular diffusivities. Two consequences are the development of double-diffusive convection1 and the creation of mushy zones in which solid and liquid intimately coexist with a complex small-scale geometry2,3. Theoretical analysis requires simplifying assumptions that must be verified by laboratory experiments. Hitherto, experiments have been carried out with aqueous solutions which do not accurately represent the dynamics of melts with high Prandtl numbers, such as magmas. Here we describe the characteristics of compositional convection using a new experimental technique which allows the viscosity of the solution to be varied independently of chemical composition and liquidus temperature. A supereutectic melt was cooled from below, causing the growth of a horizontal layer of crystals. Convective instability occurred when the local solutal Rayleigh number of the compositional boundary layer ahead of the advancing crystallization front attained a value of ~3 on average. We observed a novel regime of convection in which the thermal boundary layer above the crystallization front was essentially unmodified by the motion of the plumes. The plumes carried a small heat flux and did not mix the fluid to a uniform temperature.

  10. Development and evolution of convective bursts in WRF simulations of hurricanes Dean (2007) and Bill (2009)

    NASA Astrophysics Data System (ADS)

    Hazelton, Andrew Todd

    Understanding and predicting the inner-core structure and intensity change of tropical cyclones (TCs) remains one of the biggest challenges in tropical meteorology. This study addresses this challenge by investigating the formation, structure, and intensity changes resulting from localized strong updrafts in TCs known as convective bursts (CBs). The evolution of CBs are analyzed in high-resolution simulations of two hurricanes (Dean 2007 and Bill 2009) using the Weather Research and Forecasting (WRF) model. The simulations are able to capture the observed track and peak intensity of the TCs. With Dean, there is a slight lag between the simulated intensification and actual intensification, and the extreme rate of RI is not fully captured. However, the cycle of intensification, weakening, and re-intensification observed in both TCs is captured in the simulations, and appears to be due to a combination of internal dynamics and the surrounding environmental conditions. CBs are identified based on the 99th percentile of eyewall vertical velocity (over the layer from z = 6-12 km) in each simulation (8.4 m s-1 for Dean, 5.4 m s-1 for Bill). The highest density of CBs is found in the downshear-left quadrant, consistent with prior studies. The structure of the CBs is analyzed by comparing r-z composites of azimuths with CBs and azimuths without CBs, using composite figures and statistical comparisons. The CB composites show stronger radial inflow in the lowest 0-2 km, and stronger radial outflow from the eye to the eyewall in the 2-4 km layer. The CB composites also have stronger low-level vorticity than the non-CBs, potentially due to eyewall mesovortices. The analysis of individual CBs also confirms the importance of the eye-eyewall exchange in CB development, potentially by providing buoyancy, as parcel trajectories show that many parcels are flung outward from the eye and rapidly ascend in the CBs, with as much as 500 J/kg of CAPE along the parcel path. In addition, the

  11. Evaluating and Understanding Parameterized Convective Processes and Their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael (Principal Investigator); Kain, John S.

    1995-01-01

    Research efforts during the first year focused on numerical simulations of two convective systems with the Penn State/NCAR mesoscale model. The first of these systems was tropical cyclone Irma, which occurred in 1987 in Australia's Gulf of Carpentaria during the AMEX field program. Comparison simulations of this system were done with two different convective parameterization schemes (CPS's), the Kain-Fritsch (1993 - KF) and the Betts-Miller (Betts 1986- BM) schemes. The second system was the June 10-11 1985 squall line simulation, which occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. Simulations of this system using the KF scheme were examined in detail.

  12. Evaluating and Understanding Parameterized Convective Processes and Their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael; Kain, John S.

    1996-01-01

    Research efforts focused on numerical simulations of two convective systems with the Penn State/NCAR mesoscale model. The first of these systems was tropical cyclone Irma, which occurred in 1987 in Australia's Gulf of Carpentaria during the AMEX field program. Comparison simulations of this system were done with two different convective parameterization schemes (CPS's), the Kain-Fritsch (KF) and the Betts-Miller (BM) schemes. The second system was the June 10-11, 1985 squall line simulation, which occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. Simulations of this system using the KF scheme were examined in detail.

  13. Multiday evolution of convective bursts during western North Pacific tropical cyclone development and nondevelopment using geostationary satellite measurements

    NASA Astrophysics Data System (ADS)

    Chang, Minhee; Ho, Chang-Hoi; Park, Myung-Sook; Kim, Jinwon; Ahn, Myoung-Hwan

    2017-02-01

    Tropical cyclones (TCs) develop through latent heating from a series of deep convection. To investigate the evolution of diurnal convective burst (CB) activities prior to TC formation, we analyzed 463 tropical disturbances that developed (80) or not developed (383) into TCs over the western North Pacific during the 2007-2009 period. Geostationary satellite data allowed defining deep convection where infrared (IR) brightness temperature is lower than that of water vapor (WV). Diurnal expansions from time series of IR minus WV < 0 areas near disturbance vortex centers for 5 days are defined as CB events. Combined analysis with the Modern Era Retrospective-Analysis shows that the multiday convective-environmental evolution for TC formation is entirely different from nonformation processes in terms of the occurrence of two consecutive diurnal CB events. Multiday CBs (mCB) are observed in 67.5% of the 80 TC formation cases and in 13.8% of the 383 nonformation cases. Intensities of the middle-to-low tropospheric relative vorticity of these two groups are comparable on 4 to 5 days prior to TC formation. However, vorticity intensification is weak for nondeveloping disturbances in environments of strong vertical wind shear; these disturbances eventually decay. The vorticity of developing disturbances continuously intensifies to TC strengths. The remaining 32.5% of the TC cases without mCB show weaker initial vorticity, but rapid intensification over 3 day periods before TC formation. The present results reveal that mCB is a common feature in pre-TC stages, and large-scale environments of weak vertical wind shear are critical for the formation of TC-strength circulations.

  14. Growth and property development of convection pass deposits in recovery boilers : final project project.

    SciTech Connect

    Lien, Steve J.; Baxter, Larry L.; Frederick, W. James Jr.; Wessel, Richard A.

    2004-11-01

    As part of the U.S. Department of Energy (DOE) Office of Industrial Technologies (OIT) Industries of the Future (IOF) Forest Products research program, the mechanisms of particle deposition and properties of deposits that form in the convection passes of recovery boilers were investigated. Research from experimental facilities at Sandia National Laboratories, the Institute of Paper Science and Technology (IPST), and the University of Toronto (U of T) was coordinated into a single effort to define the controlling mechanisms and rates of deposition. Deposition rates were recorded on a volumetric and mass basis in a Sandia facility for particle sizes in the range of 0.1 to 150 {micro}m. Deposit thickness, mass, spectral emissivity, thermal conductivity, surface temperature, and apparent density were monitored simultaneously and in situ on instrumented probes that allow determination of heat flux and probe surface temperature. Particle composition and mass deposition rates were also recorded in a U of T facility for particle sizes in the range of 100 to 600 {micro}m. These measurements allowed determination of the liquid content and sticking efficiency of carryover particles that inertially impact on a deposition probe. In addition, information on particulates, stable gas species, gas temperature and velocity were obtained from field tests in an operating recovery boiler. The results were used to develop algorithms appropriate for use in computer codes that simulate recovery boilers. Representative calculations were performed using B&W's comprehensive recovery boiler model to demonstrate the use of the algorithms in such computer codes. Comparisons between observations in commercial systems and model predictions were made to identify algorithm strengths and weaknesses.

  15. Development of a Forced-Convection Liquid-Fluoride-Salt Test Loop

    SciTech Connect

    Yoder Jr, Graydon L; Wilson, Dane F; Peretz, Fred J; Wilgen, John B; Romanoski, Glenn R; Kisner, Roger A; Holcomb, David Eugene; Heatherly, Dennis Wayne; Aaron, Adam M

    2010-01-01

    A small forced-convection molten-fluoride-salt loop is being constructed at Oak Ridge National Laboratory to examine the heat transfer behavior of FLiNaK salt in a heated pebble bed. Objectives of the experiment include reestablishing infrastructure needed for fluoride-salt loop testing, developing a unique inductive heating technique for performing heat transfer (or other) experiments, measuring heat transfer characteristics in a liquid-fluoride-salt-cooled pebble bed, and demonstrating the use of silicon carbide (SiC) as a structural component for salt systems. The salt loop will consist of an Inconel 600 piping system, a sump-type pump, a SiC test section, and an air-cooled heat exchanger, as well as auxiliary systems needed to pre-heat the loop, transport salt into and out of the loop, and maintain an inert cover gas over the salt. A 30,000 Hz inductive heating system will be used to provide up to 250 kW of power to a 15 cm diameter SiC test section containing a packed bed of 3 cm graphite spheres. A SiC-to-Inconel 600 joint will use a conventional nickel/grafoil spiral wound gasket sandwiched between SiC and Inconel flanges. The loop system can provide up to 4.5 kg/s of salt flow at a head of 0.125 MPa and operate at a pressure just above atmospheric. Pebble Reynolds numbers of up to 2600 are possible with this configuration. A sump system is provided to drain and store the salt when not in use. Instrumentation on the loop will include pressure, temperature, and flow measurements, while the test section will be instrumented to provide pebble and FLiNaK temperatures.

  16. An evaluation of satellite-derived humidity and its relationship to convective development

    NASA Technical Reports Server (NTRS)

    Fuelberg, Henry E.

    1993-01-01

    An aircraft prototype of the High-Resolution Interferometer Sounder (HIS) was flown over Tennessee and northern Alabama during summer 1986. The HIS temperature and dewpoint soundings were examined on two flight days to determine their error characteristics and utility in mesoscale analyses. Random errors were calculated from structure functions while total errors were obtained by pairing the HIS soundings with radiosonde-derived profiles. Random temperature errors were found to be less than 1 C at most levels, but random dewpoint errors ranged from 1 to 5 C. Total errors of both parameters were considerably greater, with dewpoint errors especially large on the day having a pronounced subsidence inversion. Cumulus cloud cover on 15 June limited HIS mesoscale analyses on that day. Previously undetected clouds were found in many HIS fields of view, and these probably produced the low-level horizontal temperature and dewpoint variations observed in the retrievals. HIS dewpoints at 300 mb indicated a strong moisture gradient that was confirmed by GOES 6.7-micron imagery. HIS mesoscale analyses on 19 June revealed a tongue of humid air stretching across the study area. The moist region was confirmed by radiosonde data and imagery from the Multispectral Atmospheric Mapping Sensor (MAMS). Convective temperatures derived from HIS retrievals helped explain the cloud formation that occurred after the HIS overflights. Crude estimates of Bowen ratio were obtained from HIS data using a mixing-line approach. Values indicated that areas of large sensible heat flux were the areas of first cloud development. These locations were also suggested by GOES visible and infrared imagery. The HIS retrievals indicated that areas of thunderstorm formation were regions of greatest instability. Local landscape variability and atmospheric temperature and humidity fluctuations were found to be important factors in producing the cumulus clouds on 19 June. HIS soundings were capable of detecting

  17. NEW DEVELOPMENT IN DISPERSION EXPERIMENTS AND MODELS FOR THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    We present recent experiments and modeling studies of dispersion in the convective boundary layer (CBL) with focus on highly-buoyant plumes that "loft" near the CBL top and resist downward mixing. Such plumes have been a significant problem in earlier dispersion models; they a...

  18. NEW DEVELOPMENT IN DISPERSION EXPERIMENTS AND MODELS FOR THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    We present recent experiments and modeling studies of dispersion in the convective boundary layer (CBL) with focus on highly-buoyant plumes that "loft" near the CBL top and resist downward mixing. Such plumes have been a significant problem in earlier dispersion models; they a...

  19. A Generalized Simple Formulation of Convective Adjustment ...

    EPA Pesticide Factsheets

    Convective adjustment timescale (τ) for cumulus clouds is one of the most influential parameters controlling parameterized convective precipitation in climate and weather simulation models at global and regional scales. Due to the complex nature of deep convection, a prescribed value or ad hoc representation of τ is used in most global and regional climate/weather models making it a tunable parameter and yet still resulting in uncertainties in convective precipitation simulations. In this work, a generalized simple formulation of τ for use in any convection parameterization for shallow and deep clouds is developed to reduce convective precipitation biases at different grid spacing. Unlike existing other methods, our new formulation can be used with field campaign measurements to estimate τ as demonstrated by using data from two different special field campaigns. Then, we implemented our formulation into a regional model (WRF) for testing and evaluation. Results indicate that our simple τ formulation can give realistic temporal and spatial variations of τ across continental U.S. as well as grid-scale and subgrid scale precipitation. We also found that as the grid spacing decreases (e.g., from 36 to 4-km grid spacing), grid-scale precipitation dominants over subgrid-scale precipitation. The generalized τ formulation works for various types of atmospheric conditions (e.g., continental clouds due to heating and large-scale forcing over la

  20. High order WENO and DG methods for time-dependent convection-dominated PDEs: A brief survey of several recent developments

    NASA Astrophysics Data System (ADS)

    Shu, Chi-Wang

    2016-07-01

    For solving time-dependent convection-dominated partial differential equations (PDEs), which arise frequently in computational physics, high order numerical methods, including finite difference, finite volume, finite element and spectral methods, have been undergoing rapid developments over the past decades. In this article we give a brief survey of two selected classes of high order methods, namely the weighted essentially non-oscillatory (WENO) finite difference and finite volume schemes and discontinuous Galerkin (DG) finite element methods, emphasizing several of their recent developments: bound-preserving limiters for DG, finite volume and finite difference schemes, which address issues in robustness and accuracy; WENO limiters for DG methods, which address issues in non-oscillatory performance when there are strong shocks, and inverse Lax-Wendroff type boundary treatments for finite difference schemes, which address issues in solving complex geometry problems using Cartesian meshes.

  1. Transcriptome Complexity in Cardiac Development and Diseases

    PubMed Central

    Gao, Chen; Wang, Yibin

    2014-01-01

    With the advancement of transcriptome profiling by micro-arrays and high-throughput RNA-sequencing, transcriptome complexity and its dynamics are revealed at different levels in cardiovascular development and diseases. In this review, we will highlight the recent progress in our knowledge of cardiovascular transcriptome complexity contributed by RNA splicing, RNA editing and noncoding RNAs. The emerging importance of many of these previously under-explored aspects of gene regulation in cardiovascular development and pathology will be discussed. PMID:24759793

  2. Development of Real-Time Frame Selector 2 and the Characteristic Convective Structure in the Emerging Flux Region

    NASA Astrophysics Data System (ADS)

    Kozu, Hiromichi; Kitai, Reizaburo; Funakoshi, Yasuhiro

    2005-02-01

    A new image-grabbing system, Real-Time Frame Selector 2 (RTFS2), was developed and installed in the Domeless Solar Telescope at Hida Observatory. The purpose of this system is to acquire high-quality images in ground-based observations. We observed the emerging flux region NOAA 8582 in the G-band wavelengths from 20:59 UT to 23:32 UT on 1999 June 11 with RTFS2. Simultaneous Hα line center and wing wavelength observations with a Lyot filter system showed emerging flux loops and surge activities in this region. We applied a Local Correlation Tracking Method to the G-band data set in order to derive the horizontal convective structure in the upper convective zone. In addition to a meso-scale convective structure, we found divergent-flow structures under emerging flux loops, which were stable during the whole observation period, and located at the middle of the foot points of each flux loop. We suggest that the divergent-flow structure is a newly found characteristic of emerging flux regions.

  3. Mantle Convection in a Microwave Oven: New Perspectives for the Internally Heated Convection

    NASA Astrophysics Data System (ADS)

    Limare, A.; Fourel, L.; Surducan, E.; Neamtu, C.; Surducan, V.; Vilella, K.; Farnetani, C. G.; Kaminski, E. C.; Jaupart, C. P.

    2015-12-01

    The thermal evolution of silicate planets is primarily controlled by the balance between internal heating - due to radioactive decay - and heat transport by mantle convection. In the Earth, the problem is particularly complex due to the heterogeneous distribution of heat sources in the mantle and the non-linear coupling between this distribution and convective mixing. To investigate the behaviour of such systems, we have developed a new technology based on microwave absorption to study internally-heated convection in the laboratory. This prototype offers the ability to reach the high Rayleigh-Roberts and Prandtl numbers that are relevant for planetary convection. Our experimental results obtained for a uniform distribution of heat sources were compared to numerical calculations reproducing exactly experimental conditions (3D Cartesian geometry and temperature-dependent physical properties), thereby providing the first cross validation of experimental and numerical studies of convection in internally-heated systems. We find that the thermal boundary layer thickness and interior temperature scale with RaH-1/4, where RaH is the Rayleigh-Roberts number, as theoretically predicted by scaling arguments on the dissipation of kinetic energy. Our microwave-based method offers new perspectives for the study of internally-heated convection in heterogeneous systems which have been out of experimental reach until now. We are able to selectively heat specific regions in the convecting layer, through the careful control of the absorption properties of different miscible fluids. This is analogous to convection in the presence of chemical reservoirs with different concentration of long-lived radioactive isotopes. We shall show results for two different cases: the stability of continental lithosphere over a convective fluid and the evolution of a hidden enriched reservoir in the lowermost mantle.

  4. Automatic remote sensing detection of the convective boundary layer structure over flat and complex terrain using the novel PathfinderTURB algorithm

    NASA Astrophysics Data System (ADS)

    Poltera, Yann; Martucci, Giovanni; Hervo, Maxime; Haefele, Alexander; Emmenegger, Lukas; Brunner, Dominik; Henne, stephan

    2016-04-01

    We have developed, applied and validated a novel algorithm called PathfinderTURB for the automatic and real-time detection of the vertical structure of the planetary boundary layer. The algorithm has been applied to a year of data measured by the automatic LIDAR CHM15K at two sites in Switzerland: the rural site of Payerne (MeteoSwiss station, 491 m, asl), and the alpine site of Kleine Scheidegg (KSE, 2061 m, asl). PathfinderTURB is a gradient-based layer detection algorithm, which in addition makes use of the atmospheric variability to detect the turbulent transition zone that separates two low-turbulence regions, one characterized by homogeneous mixing (convective layer) and one above characterized by free tropospheric conditions. The PathfinderTURB retrieval of the vertical structure of the Local (5-10 km, horizontal scale) Convective Boundary Layer (LCBL) has been validated at Payerne using two established reference methods. The first reference consists of four independent human-expert manual detections of the LCBL height over the year 2014. The second reference consists of the values of LCBL height calculated using the bulk Richardson number method based on co-located radio sounding data for the same year 2014. Based on the excellent agreement with the two reference methods at Payerne, we decided to apply PathfinderTURB to the complex-terrain conditions at KSE during 2014. The LCBL height retrievals are obtained by tilting the CHM15K at an angle of 19 degrees with respect to the horizontal and aiming directly at the Sphinx Observatory (3580 m, asl) on the Jungfraujoch. This setup of the CHM15K and the processing of the data done by the PathfinderTURB allows to disentangle the long-transport from the local origin of gases and particles measured by the in-situ instrumentation at the Sphinx Observatory. The KSE measurements showed that the relation amongst the LCBL height, the aerosol layers above the LCBL top and the gas + particle concentration is all but

  5. On the Development of Above-Anvil Cirrus Plumes in Extratropical Convection

    NASA Astrophysics Data System (ADS)

    Homeyer, C. R.; McAuliffe, J. D.; Bedka, K. M.

    2016-12-01

    Expansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft-based imagery for several decades. Despite knowledge of their occurrence, the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known. Here, we examine the formation of these cirrus "plumes" using a combination of satellite imagery, three-dimensional ground-based radar observations, assimilated atmospheric states from a state-of-the-art reanalysis, and idealized numerical simulations with explicitly resolved convection. Using data from ten recent cases (2013-Present), we find that all storms with above-anvil cirrus plumes reach altitudes 1 to 6 km above the tropopause. Thus, it is likely that these clouds represent the injection of cloud material into the lower stratosphere. Comparison of above-anvil cirrus plume cases with ten additional cases of observed tropopause-penetrating convection without plumes reveals that these clouds are associated with large vector differences between the motion of a storm and the environmental wind in the upper troposphere and lower stratosphere (UTLS), suggesting that gravity wave breaking and/or stretching of the tropopause-penetrating cloud are/is more prevalent in plume-producing storms. No relationship is found between above-anvil cirrus plume occurrence and the stability of the lower stratosphere (or tropopause structure) or the duration of stratospheric penetration. Idealized model simulations of tropopause-penetrating convection with small and large magnitudes of storm-relative wind in the UTLS are found to reproduce the established observational relationship and show that frequent gravity wave breaking is the primary mechanism responsible for above-anvil cirrus plume formation.

  6. 2-D traveling-wave patterns in binary fluid convection

    SciTech Connect

    Surko, C.M.; Porta, A.L.

    1996-12-31

    An overview is presented of recent experiments designed to study two-dimensional traveling-wave convection in binary fluid convection in a large aspect ratio container. Disordered patterns are observed when convection is initiated. As time proceeds, they evolve to more ordered patterns, consisting of several domains of traveling-waves separated by well-defined domain boundaries. The detailed character of the patterns depends sensitively on the Rayleigh number. Numerical techniques are described which were developed to provide a quantitative characterization of the traveling-wave patterns. Applications of complex demodulation techniques are also described, which make a detailed study of the structure and dynamics of the domain boundaries possible.

  7. Effects of complex radiative and convective environments on the thermal biology of the white-crowned sparrow (Zonotrichia leucophrys gambelii).

    PubMed

    Wolf, B O; Wooden, K M; Walsberg, G E

    2000-02-01

    in wind speed was equivalent to a decrease in chamber air temperature of 16 degrees C. Overall, shifting environmental conditions from a wind speed of 0.25 m s(-1) and irradiance of 936 W m(-2) to a wind speed of 2.0 m s(-1) with no short-wave radiation present was equivalent to decreasing chamber air temperature by approximately 20 degrees C. The sensitivity to changes in the convective environment, combined with the complex effects of changes in irradiance levels revealed by re-analyzing data published previously, significantly complicates the task of estimating the heat balance of animals in nature.

  8. Mesoscale/convective interaction

    NASA Technical Reports Server (NTRS)

    Haines, P. A.; Sun, W. Y.

    1988-01-01

    A novel cumulus parameterization scheme (CPS) has been developed in order to account for mesoscale/convective-scale interaction which considers both the mesoscale and convective scale mass and moisture budgets, under the assumption that the heating rate is a maximum for given environmental conditions. The basis of the CPS is a detailed, quasi-one-dimensional cloud model that calculates mass and moisture fluxes similar to those calculated by the Schlesinger (1978) three-dimensional model.

  9. Can complexity science inform physician leadership development?

    PubMed

    Grady, Colleen Marie

    2016-07-04

    Purpose The purpose of this paper is to describe research that examined physician leadership development using complexity science principles. Design/methodology/approach Intensive interviewing of 21 participants and document review provided data regarding physician leadership development in health-care organizations using five principles of complexity science (connectivity, interdependence, feedback, exploration-of-the-space-of-possibilities and co-evolution), which were grouped in three areas of inquiry (relationships between agents, patterns of behaviour and enabling functions). Findings Physician leaders are viewed as critical in the transformation of healthcare and in improving patient outcomes, and yet significant challenges exist that limit their development. Leadership in health care continues to be associated with traditional, linear models, which are incongruent with the behaviour of a complex system, such as health care. Physician leadership development remains a low priority for most health-care organizations, although physicians admit to being limited in their capacity to lead. This research was based on five principles of complexity science and used grounded theory methodology to understand how the behaviours of a complex system can provide data regarding leadership development for physicians. The study demonstrated that there is a strong association between physician leadership and patient outcomes and that organizations play a primary role in supporting the development of physician leaders. Findings indicate that a physician's relationship with their patient and their capacity for innovation can be extended as catalytic behaviours in a complex system. The findings also identified limiting factors that impact physicians who choose to lead, such as reimbursement models that do not place value on leadership and medical education that provides minimal opportunity for leadership skill development. Practical Implications This research provides practical

  10. Characterizing convective cold pools

    NASA Astrophysics Data System (ADS)

    Drager, Aryeh J.; van den Heever, Susan C.

    2017-06-01

    Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the density potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.

  11. Convective Ignition of Propellant Cylinders in a Developing Cross-Flow Field.

    DTIC Science & Technology

    1980-09-01

    ReD range of tests. 50 Typical photo-detector output signals. 135 a) M30 propellant under low oxygen content flow (90%N &10%0, U = 6.3 m/s). b) M26 ...Photographs showing convective ignition events ( M26 139 propellant, 1.63 MPa,1740 K,140 m/s, 50%N2&50%02, ReD = 55,000). 54 Ignition data showing decreasing...pressure (for double- based M26 propellant). 57 Statistical diagram of flame spreading tendencies as a 143 function of oxygen concentration and Reynolds

  12. Recent developments in complex metal oxide photoelectrodes

    NASA Astrophysics Data System (ADS)

    Abdi, Fatwa F.; Berglund, Sean P.

    2017-05-01

    Photoelectrochemical (PEC) water splitting, a process that directly produces hydrogen from water and sunlight using semiconductor materials, is an attractive form of renewable energy production. The hydrogen that is produced can be easily transported, stored, and utilized as a fuel without the emission of greenhouse gasses. However, many scientific and engineering challenges need to be overcome before PEC water splitting can be implemented on a large scale. One of the biggest challenges is the identification of suitable semiconductor materials to use in the construction of photoelectrodes. This topical review highlights a promising class of materials, complex metal oxides, which can be used as photoelectrodes for PEC water splitting. The advantages and limitations of complex metal oxides are first discussed, and strategies to overcome the limitations are outlined using the model case of bismuth vanadate (BiVO4), one of the highest performing complex metal oxide photoanodes reported to date. Building on the success story of BiVO4, we discuss pathways towards achieving even higher water splitting performance, including bandgap engineering as well as the development of alternative complex metal oxides with more appropriate bandgaps for obtaining high solar-to-hydrogen efficiency. Several classes of complex metal oxides (e.g. delafossites, tungstates, vanadates, spinels) are presented as promising candidates for photoelectrode materials. Finally, we conclude by summarizing the key properties of these complex metal oxides and providing an outlook towards expedited discovery of new and novel complex metal oxides for use as photoelectrodes.

  13. Supergranular Convection

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2015-12-01

    Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Here the opacity is so large that heat flux transport is mainly by convection rather than by photon diffusion. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection , Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni

  14. Preclinical evaluation of an O6-methylguanine-DNA methyltransferase-siRNA/liposome complex administered by convection-enhanced delivery to rat and porcine brains

    PubMed Central

    Tsujiuchi, Takashi; Natsume, Atsushi; Motomura, Kazuya; Kondo, Goro; Ranjit, Melissa; Hachisu, Rei; Sugimura, Itsuro; Tomita, Shinpei; Takehara, Isao; Woolley, Max; Barua, Neil U; Gill, Steven S; Bienemann, Alison S; Yamashita, Yoriko; Toyokuni, Shinya; Wakabayashi, Toshihiko

    2014-01-01

    The main determinant of glioblastoma (GBM) resistance to temozolomide (TMZ) is thought to be O6-methylguanine-DNA methyltransferase (MGMT), which is a DNA-repair enzyme that removes alkyl groups from the O6-position of guanine. Previously, we reported that a MGMT-siRNA/cationic liposome complex exerted a clear synergistic antitumor effect in combination with TMZ. Translation to a clinical setting might be desirable for reinforcing the efficacy of TMZ therapy for GBM. In this study, we aim to evaluate the safety of MGMT-siRNA/cationic liposome complexes and determine whether the convection-enhanced delivery of these complexes is suitable for clinical use by undertaking preclinical testing in laboratory animals. No significant adverse events were observed in rats receiving infusions of MGMT-siRNA/cationic liposome complex directly into the brain with or without TMZ administration. A pig which received the complex administered by CED also showed no evidence of neurological dysfunction or histological abnormalities. However, the complex did not appear to achieve effective distribution by CED in either the rat or the porcine brain tissue. Considering these results together, we concluded that insufficient distribution of cationic liposomes was achieved for tumor treatment by CED. PMID:24489997

  15. Population Dynamics and Convective Cloud Fields

    NASA Astrophysics Data System (ADS)

    Nober, F. J.; Graf, H.-F.

    2003-04-01

    A cumulus cloud field model has been coupled to an atmospheric general circulation model (AGCM). The results, which show a good performance of the model within the AGCM and a qualitative good agreement to observation concerning the statistical information of cloud fields are presented. While most of the current cumulus convection parameterisations are formulated as massflux schemes (determing the overall massflux of all cumulus clouds in one AGCM grid column) the presented cloud field model determines for each AGCM grid column, where convection takes place, an explicit spectrum of different clouds. Therefore the information about the actual cumulus convection state in a grid column is not restricted to an avereged massflux but includes the number of different cloud types which in principle are able to develope under the given vertical condition. The degree to which part each cloud type participates in the whole cloud field is determined by the cloud field model with respect to the special vertical state in the grid column. The choice of the cloud model to define the different cloud types is very flexible. Very simple cloud models are possible but also more complex ones that describe more realistic clouds (including dynamic and microphysical information) than simple massflux approaches do. The cloud field model takes into account the interaction between all non-convective processes calculated by the AGCM and (which makes the procedure self constistent) the cloud-cloud interaction between each cloud type and each other. The final calculation of the cloud field is done following an approach from population dynamics (Lotka-Volterra-Equation). The tests of the model in the ECHAM5 AGCM (running in single column mode) shows that the model produces reliable convective feedbacks (i.e. integral convective heating, convective transport, etc.). The additional information of the cloud field structure (power law behavior of cloud size distribution, cloud tops for each cloud type

  16. A modelling investigation into lake-breeze development and convection triggering in the Nam Co Lake basin, Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Gerken, Tobias; Biermann, Tobias; Babel, Wolfgang; Herzog, Michael; Ma, Yaoming; Foken, Thomas; Graf, Hans-F.

    2014-07-01

    This paper uses the cloud resolving Active Tracer High-resolution Atmospheric Model coupled to the interactive surface model Hybrid in order to investigate the diurnal development of a lake-breeze system at the Nam Co Lake on the Tibetan Plateau. Simulations with several background wind speeds are conducted, and the interaction of the lake breeze with topography and background wind in triggering moist and deep convection is studied. The model is able to adequately simulate the systems most important dynamical features such as turbulent surface fluxes and the development of a lake breeze for the different wind conditions. We identify two different mechanisms for convection triggering that are dependent on the direction of the background wind: triggering over topography, when the background wind and the lake breeze have the same flow direction, and triggering due to convergence between the lake-breeze front and the background wind. Our research also suggests that precipitation measurements at the centre of the basins on the Tibetan Plateau are not representative for the basin as a whole as precipitation is expected to occur mainly in the vicinity of the topography.

  17. Observations of Convective Development from Repeat Pass Radiometry during CalWaters 2015: Outlook for the TEMPEST Mission

    NASA Astrophysics Data System (ADS)

    Brown, S. T.

    2015-12-01

    The Temporal Experiment for Storms and Tropical Systems (TEMPEST), which was recently selected as a NASA Earth Ventures technology demonstration mission, uses a constellation of five CubeSats flying in formation to provide observations of developing precipitation with a temporal resolution of 5 minutes. The observations are made using small mm-wave radiometers with frequencies ranging from 90 to 183 GHz which are sensitive to the integrated ice water path above the precipitation layer in the storm. This paper describes TEMPEST like observations that were made with the High Altitude MMIC Sounding Radiometer (HAMSR) on the ER-2 during CalWaters 2015. HAMSR is a mm-wave airborne radiometer with 25 channels in three bands; 50, 118 and 183 GHz. During the campaign, a small isolated area of convection was identified by the ER-2 pilot and 5 overpasses of the area were made with about 5 minutes between each pass. The HAMSR data reveal two convective cells, one which was diminishing and one which was developing. The mm-wave channels near the 183 GHz water vapor line clearly show the change in the vertical extent of the storm with time, a proxy for vertical velocity. These data demonstrate the potential for TEMPEST like observations from an orbital vantage point. This paper will provide an overview of the measurements, an analysis of the observations and offer perspectives for the TEMPEST mission.

  18. Whole Mantle Thermo-Chemical Convection Models With Realistic Mineral Physics Naturally Develop Chemical Stratification

    NASA Astrophysics Data System (ADS)

    Tackley, P. J.; Nakagawa, T.; Deschamps, F.; Connolly, J. A.

    2007-12-01

    Starting with [Christensen and Yuen, 1985 JGR], many isochemical convection models have demonstrated the existence of "intermittent" or "partial" layering enforced by the ringwoodite to perovskite+magnesiowustite phase transition over a certain range of Clapeyron slope values, which has often been cited as a possible mechanism for reconciling conflicting evidences for whole-mantle and layered convection. Current mineral physics constraints indicate, however, that the likely value of the Clapeyron slope is too low to enforce this mode, although studies have shown that a viscosity increase at 660 km depth might account for much of the observed variation in slab dynamics without appealing to a phase transition. When chemical variations are additionally taken into account, the dynamical effect of phase transitions can again become important. Firstly the additive effect of the '660' phase transition and chemical buoyancy can combine to keep denser than average material in the lower mantle and less dense than average material in the upper mantle, the so-called filter effect first identified by Weinstein [1992 EPSL]. Secondly, the pyroxene-garnet components transform to perovskite at a higher pressure than olivine components, giving positive buoyancy to MORB and negative buoyancy to harzburgite in the depth range 660-720 km, which has been shown to cause local chemical stratification around 660 km depth. Thirdly, MORB is likely denser than average mantle in the deep mantle, and some fraction of it settles into a layer above the CMB. These effects are here demonstrated and quantified in 3-D spherical convection calculations in which the mineralogy is calculated self-consistently as a function of temperature, pressure and composition (expressed as the ratios of 5 oxides) using free energy minimization. Compositional variations arise self-consistently from melting. These build on the earlier studies of Xie and Tackley [2004 PEPI, JGR], Nakagawa and Tackley [2005 Gcubed; 2006

  19. Active control of convection

    SciTech Connect

    Bau, H.H.

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  20. Spatial distribution and frequency of precipitation during an extreme event: July 2006 mesoscale convective complexes and floods in southeastern Arizona

    NASA Astrophysics Data System (ADS)

    Griffiths, Peter G.; Magirl, Christopher S.; Webb, Robert H.; Pytlak, Erik; Troch, Peter A.; Lyon, Steve W.

    2009-07-01

    An extreme, multiday rainfall event over southeastern Arizona during 27-31 July 2006 caused record flooding and a historically unprecedented number of slope failures and debris flows in the Santa Catalina Mountains north of Tucson. An unusual synoptic weather pattern induced repeated nocturnal mesoscale convective systems over southeastern Arizona for five continuous days, generating multiday rainfall totals up to 360 mm. Analysis of point rainfall and weather radar data yielded storm totals for the southern Santa Catalina Mountains at 754 grid cells approximately 1 km × 1 km in size. Precipitation intensity for the 31 July storms was not unusual for typical monsoonal precipitation in this region (recurrence interval (RI) < 1 year), but multiday rainfall where slope failures occurred had RI > 50 years and individual grid cells had RI exceeding 1000 years. The 31 July storms caused the watersheds to be essentially saturated following 4 days of rainfall.

  1. Spatial distribution and frequency of precipitation during an extreme event: July 2006 mesoscale convective complexes and floods in southeastern Arizona

    USGS Publications Warehouse

    Griffiths, P.G.; Magirl, C.S.; Webb, R.H.; Pytlak, E.; Troch, Peter A.; Lyon, S.W.

    2009-01-01

    An extreme, multiday rainfall event over southeastern Arizona during 27-31 July 2006 caused record flooding and a historically unprecedented number of slope failures and debris flows in the Santa Catalina Mountains north of Tucson. An unusual synoptic weather pattern induced repeated nocturnal mesoscale convective systems over southeastern Arizona for five continuous days, generating multiday rainfall totals up to 360 mm. Analysis of point rainfall and weather radar data yielded storm totals for the southern Santa Catalina Mountains at 754 grid cells approximately 1 km ?? 1 km in size. Precipitation intensity for the 31 July storms was not unusual for typical monsoonal precipitation in this region (recurrence interval (RI) < 1 year), but multiday rainfall where slope failures occurred had RI > 50 years and individual grid cells had RI exceeding 1000 years. The 31 July storms caused the watersheds to be essentially saturated following 4 days of rainfall. Copyright 2009 by the American Geophysical Union.

  2. Mixed Convective Fully Developed Flow in a Vertical Channel in the Presence of Thermal Radiation and Viscous Dissipation

    NASA Astrophysics Data System (ADS)

    Prasad, K. V.; Mallikarjun, P.; Vaidya, H.

    2017-02-01

    The effect of thermal radiation and viscous dissipation on a combined free and forced convective flow in a vertical channel is investigated for a fully developed flow regime. Boussinesq and Roseseland approximations are considered in the modeling of the conduction radiation heat transfer with thermal boundary conditions (isothermal-thermal, isoflux-thermal, and isothermal-flux). The coupled nonlinear governing equations are also solved analytically using the Differential Transform Method (DTM) and regular perturbation method (PM). The results are analyzed graphically for various governing parameters such as the mixed convection parameter, radiation parameter, Brinkman number and perturbation parameter for equal and different wall temperatures. It is found that the viscous dissipation enhances the flow reversal in the case of a downward flow while it counters the flow in the case of an upward flow. A comparison of the Differential Transform Method (DTM) and regular perturbation method (PM) methods shows the versatility of the Differential Transform Method (DTM). The skin friction and the wall temperature gradient are presented for different values of the physical parameters and the salient features are analyzed.

  3. Development of charge structure in a short live convective cell observed by a 3D lightning mapper and a phased array radar

    NASA Astrophysics Data System (ADS)

    Yoshida, S.; Adachi, T.; Kusunoki, K.; Wu, T.; Ushio, T.; Yoshikawa, E.

    2015-12-01

    Thunderstorm observation has been conducted in Osaka, Japan, with a use of a 3D lightning mapper, called Broadband Observation network for Lightning and Thunderstorm (BOLT), and an X-band phased array radar (PAR). BOLT is a LF sensor network that receives LF emission associated with lightning discharges and locates LF radiation sources in 3D. PAR employs mechanical and electrical scans, respectively, in azimuthal and elevation direction, succeeding in quite high volume scan rate. In this presentation, we focus on lightning activity and charge structure in convective cells that lasted only short time (15 minutes or so). Thunderstorms that consisted of several convective cells developed near the radar site. Precipitation structure of a convective cell in the thunderstorm was clearly observed by PAR. A reflectivity core of the convective cell appeared at an altitude of 6 km at 2245 (JST). After that the core descended and reached the ground at 2256 (JST), resulting in heavy precipitation on surface. The echo top height (30dBZ) increased intermittently between 2245 (JST) and 2253 (JST) and it reached at the altitude of 12 km. The convective cell dissipated at 2300. Many intra-cloud (IC) flashes were initiated within the convective cell. Most IC flashes that were initiated in the convective cell occurred during the time when the echo top height increased, while a few IC flashes were initiated in the convective cell after the cease of the echo top vertical development. These facts indicate that strong updraft at upper levels (about 8 km or higher) plays an important role on thunderstorm electrification for IC flashes. Moreover, initiation altitudes of the IC flashes and the positive charge regions removed by the IC flashes increased, as the echo top height increased. This fact implies that the strong updraft at the upper levels blew up positively-charged ice pellets and negatively-charged graupel, and lifted IC flash initiation altitudes and positive charge regions

  4. Development of simulation computer complex specification

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The Training Simulation Computer Complex Study was one of three studies contracted in support of preparations for procurement of a shuttle mission simulator for shuttle crew training. The subject study was concerned with definition of the software loads to be imposed on the computer complex to be associated with the shuttle mission simulator and the development of procurement specifications based on the resulting computer requirements. These procurement specifications cover the computer hardware and system software as well as the data conversion equipment required to interface the computer to the simulator hardware. The development of the necessary hardware and software specifications required the execution of a number of related tasks which included, (1) simulation software sizing, (2) computer requirements definition, (3) data conversion equipment requirements definition, (4) system software requirements definition, (5) a simulation management plan, (6) a background survey, and (7) preparation of the specifications.

  5. Semi-convective layer formation

    NASA Astrophysics Data System (ADS)

    Zaussinger, F.; Kupka, F.; Egbers, Ch.; Neben, M.; Hücker, S.; Bahr, C.; Schmitt, M.

    2017-05-01

    Semi-convective mixing, as an example of double-diffusive convection, is of general importance in multi-component fluid mixing processes. In astrophysics it occurs when the mean molecular weight gradient caused by a mixture of light material on top of heavier one counteracts the convective instability caused by a temperature gradient. Direct numerical simulations of double-diffusive fluid flows in a realistic stellar or planetary parameter space are currently non-feasible. Hence, a model describing incompressible semi-convection was developed, which allows to investigate semi-convective layer formation. A detailed parameter study with varying Rayleigh number and stability parameter has been performed for the giant planet case. We conclude that semi-convective layering may not play that important role as suggested in earlier works for the planetary case.

  6. Cormorant: Development of a complex field

    SciTech Connect

    Stiles, J.H.; McKee, J.W.

    1986-01-01

    The Cormorant Field provides an example of the numerous changes which are required to the development plan for a large, complex field as the nature of its complexity becomes better known. Changes in the basic development and displacement pattern, the number and spacing of wells, and completion method have occurred as the structural, stratigraphic and diagenetic nature of the field has been uncovered. In addition, a better understanding of a key development constraint, the drilling reach, has allowed changes with significant cost savings. While a well thought out initial development plan was formulated for the field, close surveillance of geological results and field performance has been necessary to allow its almost continuous updating. This paper discusses studies and evaluations undertaken by Esso Exporation and Production U.K. to evaluate such changes. In addition to a discussion of each of the four fault blocks comprising the field, the following are addressed: (1) the role of detailed reservoir description work, (2) use of partial perforation techniques for waterflood control, and (3) the tailoring of reservoir monitoring to the specific problems of Cormorant. These studies were done to complement work done by the operator, Shell U.K. Exploration and Production, who prepared the base development plan and subsequent updates.

  7. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1994-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode.

  8. Convection towers

    DOEpatents

    Prueitt, M.L.

    1996-01-16

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water. 6 figs.

  9. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1995-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  10. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1996-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  11. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  12. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  13. GOES Infrared and Reflectance 0-1 hour Lightning Initiation Indicators: Development and Initial Testing within a Convective Nowcasting System

    NASA Astrophysics Data System (ADS)

    Mecikalski, J. R.; Harris, R.; MacKenzie, W.; Durkee, P. A.; Iskenderian, H.; Bickmeier, L.; Nielsen, K. E.

    2010-12-01

    Within cumulus cloud fields that develop in conditionally unstable air masses, only a fraction of the cumuli may eventually develop into deep convection. Identifying which of these convective clouds most likely to generate lightning often starts with little more than a qualitative visual satellite analysis. The goal of this study is to identify the observed satellite infrared (IR) signatures associated with growing cumulus clouds prior to the first lightning strike, so-called lightning initiation (LI). This study quantifies the behavior of ten Geostationary Operational Environmental Satellite (GOES-12) IR interest fields in the 1-hour in advance of LI. A total of 172 lightning-producing storms that occurred during the 2009 convective season are manually tracked and studied over four regions: Northern Alabama, Central Oklahoma, the Kennedy Space Center and Washington D.C. Four-dimensional and cloud-to-ground lightning array data provide a total cloud lightning picture (in-cloud, cloud-to-cloud, cloud-to-air, cloud-to-ground) and thus precise LI points for each storm in both time and space. Statistical significance tests are conducted on observed trends for each of the ten LI fields to determine the unique information each field provides in terms of behavior prior to LI. Eight out of ten LI fields exhibited useful information at least 15 min in advance of LI, with 35 min being the average. Statistical tests on these eight fields are compared for separate large geographical areas. IR temperature thresholds are then determined as an outcome, which may be valuable when implementing a LI prediction algorithm into real-time satellite-based systems. The key LI indicators from GOES IR data (as well as 3.9 μm reflectance) will be presented. Beginning in 2010, the feasibility of using the satellite-based LI indicators found in the above analysis to forecast first lightning will be assessed within the Federal Aviation Administration’s (FAA) CoSPA nowcasting system. The goal

  14. Giga-LES of Hector the Convector: How Shallow Convection over Island Developed into Very Deep Convection up to the Stratosphere

    NASA Astrophysics Data System (ADS)

    Dauhut, T.; Chaboureau, J. P.; Escobar, J.; Mascart, P. J.

    2016-12-01

    The hydration of the stratosphere by Hector the Convector, observed on 30 November 2005 over the Tiwi Islands, Australia, is investigated using a Giga Large-Eddy Simulation with a 100-m cubic mesh. Individual updrafts defined as 3D objects with vertical velocity above 10 m/s are identified. Among the 20,000 updrafts identified during the most intense phase, a dozen was more-than-4-km tall. The two tallest accounted for more than 90 % of the total vertical mass flux through the Tropical Tropopause Layer. Their locations were determined by low-level convergence lines first created by the sea breeze in the morning, on which popped up shallow convection, then enhanced by cold pools due to congestus and finally reinforced each other as they moved inland and intersected. The two tallest updrafts that overshot the stratosphere were contrasted with those occurring one hour earlier and later. They present larger width (up to 8 km), greater buoyancy (up to 0.1 m/s²), stronger vertical velocities (up to 50 m/s) and larger hydrometeor contents (more than 10 g/kg). They kept their core weakly diluted on their way to the stratosphere with an entrainment rate as low as 0.08 /km. Both the low-level convergence lines intensified by cold pools and the reduced mixing in the troposphere are found to be determinant for the transition from shallow to deep and from deep to very deep convection. This study was supported by the StratoClim project.

  15. Controlling Complex Systems and Developing Dynamic Technology

    NASA Astrophysics Data System (ADS)

    Avizienis, Audrius Victor

    In complex systems, control and understanding become intertwined. Following Ilya Prigogine, we define complex systems as having control parameters which mediate transitions between distinct modes of dynamical behavior. From this perspective, determining the nature of control parameters and demonstrating the associated dynamical phase transitions are practically equivalent and fundamental to engaging with complexity. In the first part of this work, a control parameter is determined for a non-equilibrium electrochemical system by studying a transition in the morphology of structures produced by an electroless deposition reaction. Specifically, changing the size of copper posts used as the substrate for growing metallic silver structures by the reduction of Ag+ from solution under diffusion-limited reaction conditions causes a dynamical phase transition in the crystal growth process. For Cu posts with edge lengths on the order of one micron, local forces promoting anisotropic growth predominate, and the reaction produces interconnected networks of Ag nanowires. As the post size is increased above 10 microns, the local interfacial growth reaction dynamics couple with the macroscopic diffusion field, leading to spatially propagating instabilities in the electrochemical potential which induce periodic branching during crystal growth, producing dendritic deposits. This result is interesting both as an example of control and understanding in a complex system, and as a useful combination of top-down lithography with bottom-up electrochemical self-assembly. The second part of this work focuses on the technological development of devices fabricated using this non-equilibrium electrochemical process, towards a goal of integrating a complex network as a dynamic functional component in a neuromorphic computing device. Self-assembled networks of silver nanowires were reacted with sulfur to produce interfacial "atomic switches": silver-silver sulfide junctions, which exhibit

  16. Experimental measurements and CFD simulation of convective boiling during subcooled developing flow of R-11 within vertical annulus

    NASA Astrophysics Data System (ADS)

    Bouaichaoui, Y.; Kibboua, R.; Matkovič, M.

    2015-05-01

    In this paper a convective flow boiling of refrigerant R-11 in a vertical annular channel has been investigated. Measurements were performed under various conditions of mass flux, heat flux, and inlet subcooling, which enabled to study the influence of different boundary conditions on the development of local flow parameters. Also, some measurements have been compared to the predictions by the three-dimensional two-fluid model of subcooled boiling flow carried out with the computer code ANSYS-CFX-13. Simulation results successfully predict the main experimental tendencies associated with the heat flux and Reynolds number variation. A sensitivity analysis of several modelling parameters on the radial distribution of flow quantities has highlighted the importance of correct description of the boiling boundary layer. In general a good quantitative and qualitative agreement with experimental data was obtained.

  17. Cormorant; Development of a complex field

    SciTech Connect

    Stiles, J.H. Jr.; McKee, J.W. )

    1991-12-01

    The development plan of Cormorant oil field exemplifies changes required as the nature of a large, complex field becomes better known. The number and locations of wells and the completion method have changed as the structural, stratigraphic, and diagnetic natures of the field became better known. A better understanding of a key development constraint-and drilling reach-has allowed changes to the development plan at significant cost savings. Close surveillance of geological results and field performance has been necessary to allow almost continuous updating. This paper discusses studies and evaluations undertaking by Eso E and P U.K. to evaluate such changes for each of the field's four fault blocks. These studies complemented work done by the operator, Shell U.K. E and P.

  18. Convective quasi-equilibrium

    NASA Astrophysics Data System (ADS)

    Yano, J.-I.; Plant, R. S.

    2012-12-01

    The concept of convective quasi-equilibrium (CQE) is a key ingredient in order to understand the role of deep moist convection in the atmosphere. It has been used as a guiding principle to develop almost all convective parameterizations and provides a basic theoretical framework for large-scale tropical dynamics. The CQE concept as originally proposed by Arakawa and Schubert (1974) is systematically reviewed from wider perspectives. Various interpretations and extensions of Arakawa and Schubert's CQE are considered both in terms of a thermodynamic analogy and as a dynamical balance. The thermodynamic interpretations can be more emphatically embraced as a homeostasis. The dynamic balance interpretations can be best understood by analogy with the slow manifold. Various criticisms of CQE can be avoided by taking the dynamic balance interpretation. Possible limits of CQE are also discussed, including the importance of triggering in many convective situations, as well as the possible self-organized criticality of tropical convection. However, the most intriguing aspect of the CQE concept is that in spite of many observational tests supporting and interpreting it in many different senses, it has never been established in a robust manner based on a systematic analysis of the cloud work function budget by observations as was originally defined.

  19. Theoretical scaling law for heat transfer by quasi-geostrophic convection

    NASA Astrophysics Data System (ADS)

    King, E. M.; Stellmach, S.; Aurnou, J. M.

    2011-12-01

    Convection is a ubiquitous process occurring, for example, in Earth's atmosphere, oceans, and liquid metal core, as well as on other planets and stars. Convective turbulence is responsible for many observed phenomena (e.g., weather, magnetic field generation), but the turbulent processes themselves are often poorly understood. An important consequence of turbulent convection is heat transport by fluid motions. Developing and testing theory for heat transport by turbulent convection probes our understanding of this complex system. We present a new theory for heat transport by geostrophic convection -- in which the Coriolis force plays a dominant role. Following the work by Malkus (1954), we use boundary layer stability arguments to develop a depth-independent scaling law for the Nusselt number as a function of Rayleigh and Ekman numbers: Nu ~ Ra3E4. The theory also reveals the importance of boundary layers in determining the dynamical regime of convection. We test the theory with data from numerical simulations and laboratory experiments of rotating Rayleigh-Bénard convection at low Ekman numbers E≥10-6. Improved heat transfer scaling laws permit better estimates of dissipation and available energy for convection, and therefore the time and length scales of convection systems can be better constrained.

  20. Quantifying the added value of convection-permitting climate simulations in complex terrain: a systematic evaluation of WRF over the Himalayas

    NASA Astrophysics Data System (ADS)

    Karki, Ramchandra; Hasson, Shabeh ul; Gerlitz, Lars; Schickhoff, Udo; Scholten, Thomas; Böhner, Jürgen

    2017-07-01

    Mesoscale dynamical refinements of global climate models or atmospheric reanalysis have shown their potential to resolve intricate atmospheric processes, their land surface interactions, and subsequently, realistic distribution of climatic fields in complex terrains. Given that such potential is yet to be explored within the central Himalayan region of Nepal, we investigate the skill of the Weather Research and Forecasting (WRF) model with different spatial resolutions in reproducing the spatial, seasonal, and diurnal characteristics of the near-surface air temperature and precipitation as well as the spatial shifts in the diurnal monsoonal precipitation peak over the Khumbu (Everest), Rolwaling, and adjacent southern areas. Therefore, the ERA-Interim (0.75°) reanalysis has been dynamically refined to 25, 5, and 1 km (D1, D2, and D3) for one complete hydrological year (October 2014-September 2015), using the one-way nested WRF model run with mild nudging and parameterized convection for the outer but explicitly resolved convection for the inner domains. Our results suggest that D3 realistically reproduces the monsoonal precipitation, as compared to its underestimation by D1 but overestimation by D2. All three resolutions, however, overestimate precipitation from the westerly disturbances, owing to simulating anomalously higher intensity of few intermittent events. Temperatures are generally reproduced well by all resolutions; however, winter and pre-monsoon seasons feature a high cold bias for high elevations while lower elevations show a simultaneous warm bias. Unlike higher resolutions, D1 fails to realistically reproduce the regional-scale nocturnal monsoonal peak precipitation observed in the Himalayan foothills and its diurnal shift towards high elevations, whereas D2 resolves these characteristics but exhibits a limited skill in reproducing such a peak on the river valley scale due to the limited representation of the narrow valleys at 5 km resolution

  1. Gravity wave initiated convection

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1990-01-01

    The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.

  2. Complex fold patterns developed by progressive deformation

    NASA Astrophysics Data System (ADS)

    Carreras, Jordi; Druguet, Elena

    2017-04-01

    Folds arise from shortening instabilities in rocks containing layers with contrasting viscosities or bearing mechanical anisotropies. A complete understanding of this fact requires a three-dimensional approach, because of the variable geometrical relations between strain and kinematic tensors and the surfaces subjected to folding. This is especially common in progressive non-coaxial flow, under which folds become unstable, leading to fold hinge curvature, axial surface curvature or both. The resulting complex fold patterns generated by progressive folding can be morphologically indistinguishable from interference patterns produced by the superposition of two fold systems, and a detailed 3-D analysis is needed to distinguish between them. This study is focused on complex fold shapes arisen from progressive single deformations. Examples can be grouped into: (i) non-cylindrical (or non-cylindroidal) folds and (ii) folds with non-planar axial surfaces (or non-plane folds). In both cases, hinge lines and axial surfaces can display up to a 180° curvature. Hinge line curvature leads to the development of sheath folds, while axial surface curvature leads to the development of polyclinal folds, being these cylindroidal if the hinges remain straight. The two end-member situations (sheath folds and polyclinal folds) are illustrated using examples from the Variscan Cap de Creus massif (Eastern Pyrenees). Fold Hinge rotation and development of sheath folds In simple shear zones, folds commonly nucleate with hinges at a high angle to the shear direction and progressively rotate towards parallelism with the shear/extension direction, giving rise to sheath folds. Axial surfaces also change in attitude with increasing strain, becoming parallel to the shear plane. Development of polyclinal folds with strongly curved axial surfaces A peculiar complex fold pattern consists of strongly curved axial surfaces but straight hinges. This folding type is opposed to sheath folds where axial

  3. Convection towers

    DOEpatents

    Prueitt, M.L.

    1994-02-08

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode. 5 figures.

  4. Subcritical convection in an internally heated layer

    NASA Astrophysics Data System (ADS)

    Xiang, Linyan; Zikanov, Oleg

    2017-06-01

    Thermal convection in a horizontal layer with uniform internal heating and stress-free constant-temperature boundaries is analyzed numerically. The work is motivated by the questions arising in the development of liquid metal batteries, in which convection is induced by the Joule heating of electrolyte. It is demonstrated that three-dimensional convection cells exist at subcritical Rayleigh numbers.

  5. Global tectonics from mantle convection models

    NASA Astrophysics Data System (ADS)

    Coltice, N.

    2015-12-01

    The motions of the surface of the Earth are described using the theory of Plate Tectonics. Despite the fact that this theory has shaped modern geosciences it has some limitations, and among them the impossibility to evaluate the forces at the origin of the surface displacements and deformations. Hence important questions remain difficult to solve like the origin of the sizes of plates, forces driving mountain building or supercontinent dispersal... Tremendous progresses have been made in the past 15 years in mantle convection modelling. Especially, modern convection codes can solve for motion equations with complex material properties. Since the early 2000's, the development of pseudo-plastic rheologies contributed to produce convection models with plate-like behaviour: plates naturally emerge and interact with the flow in a self-organized manner. Using such models in 3D spherical geometry (computed with StagYY - Tackley, 2008), I will show that important questions on the global tectonics of the planet can be addressed now: the distribution of seafloor ages, the distribution of plate area, the lifetime of small and large plates or modes of plate reorganizations. Tackley, P.J., Modellng compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Phys. Earth Planet. Inter, 171, 7-18 (2008).

  6. Spontaneous development of arcuate single-sided subduction in global 3-D mantle convection models with a free surface

    NASA Astrophysics Data System (ADS)

    Crameri, Fabio; Tackley, Paul J.

    2014-07-01

    We present temporally evolving 3-D global mantle convection models with single-sided subduction and a free surface in both 3-D Cartesian and fully spherical geometry. Special focus is given to the spontaneous development of three-dimensional structures at the surface and in the upper mantle. We find that an arcuate shape is the natural form for trenches and slabs. Cartesian models are used first to study the dynamic evolution of subduction zones, spreading ridges, and interconnected transform features. These experiments highlight the strong variation of spontaneously developing, arcuate slab curvature and subduction polarity along the trench strike. The spontaneous development of spreading ridges leads to lateral offsets between separated segments that are characterized by normal transform motion. Spherical models then allow insights into the evolution of plate tectonics on a sphere. Investigated are the spontaneous evolution of slab geometry, trench motion, and subduction-induced mantle flow. Two new dynamical features are discovered: "back-slab spiral flow" and "slab tunneling." 2014. American Geophysical Union. All Rights Reserved.

  7. Interactions Between Convective Storms and Their Environment

    NASA Technical Reports Server (NTRS)

    Maddox, R. A.; Hoxit, L. R.; Chappell, C. F.

    1979-01-01

    The ways in which intense convective storms interact with their environment are considered for a number of specific severe storm situations. A physical model of subcloud wind fields and vertical wind profiles was developed to explain the often observed intensification of convective storms that move along or across thermal boundaries. A number of special, unusually dense, data sets were used to substantiate features of the model. GOES imagery was used in conjunction with objectively analyzed surface wind data to develop a nowcast technique that might be used to identify specific storm cells likely to become tornadic. It was shown that circulations associated with organized meso-alpha and meso-beta scale storm complexes may, on occasion, strongly modify tropospheric thermodynamic patterns and flow fields.

  8. Formation and dynamics of hazardous convective weather events in Ukraine

    NASA Astrophysics Data System (ADS)

    Balabukh, Vera; Malytska, Liudmyla; Bazalieieva, Iuliana

    2013-04-01

    Atmospheric circulation change observed from the middle of the 70s of the twentieth century in the Northern Hemisphere resulted in changes of weather events formation conditions in different regions. The degree of influence of various factors on the formation of weather events also has changed. This eventually led to an increase in number and intensity of weather events and their variations in time and space. Destructions and damages associated with these events have increased recently and the biggest damages are mainly results of complex convective weather events: showers, hail, squall. Therefore, one of the main tasks of climatology is to study the mechanisms of change repeatability and intensity of these events. The paper considers the conditions of formation of hazardous convective weather phenomena (strong showers, hail, squalls, tornadoes) in Ukraine and their spatial and temporal variability during 1981 - 2010. Research of convection processes was based on daily radiosonde data for the warm season (May-September 1981 - 2010s), reanalysis ERA-Interim ECMWF data for 1989 - 2010 years , daily observations at 187 meteorological stations in Ukraine, as well as observations of the natural phenomena in other regions (different from the meteorological stations). Indices of atmospheric instability, the magnitude of the Convective Available Potential Energy (CAPE), the moisture, the height of the condensation and equilibrium level was used to quantify the intensity of convection. The criteria for the intensity of convection for Ukrainian territory were refined on the basis of these data. Features of the development of convection for various hazardous convective weather events were investigated and identified the necessary conditions for the occurrence of showers, hail, tornadoes and squall in Ukraine. Spatio-temporal variability of convection intensity in Ukraine, its regional characteristics and dynamics for the past 30 year was analyzed. Significant tendency to an

  9. CONVECTION REACTOR

    DOEpatents

    Hammond, R.P.; King, L.D.P.

    1960-03-22

    An homogeneous nuclear power reactor utilizing convection circulation of the liquid fuel is proposed. The reactor has an internal heat exchanger looated in the same pressure vessel as the critical assembly, thereby eliminating necessity for handling the hot liquid fuel outside the reactor pressure vessel during normal operation. The liquid fuel used in this reactor eliminates the necessity for extensive radiolytic gas rocombination apparatus, and the reactor is resiliently pressurized and, without any movable mechanical apparatus, automatically regulates itself to the condition of criticality during moderate variations in temperature snd pressure and shuts itself down as the pressure exceeds a predetermined safe operating value.

  10. Development of the communication complexity scale.

    PubMed

    Brady, Nancy C; Fleming, Kandace; Thiemann-Bourque, Kathy; Olswang, Lesley; Dowden, Patricia; Saunders, Muriel D; Marquis, Janet

    2012-02-01

    Accurate description of an individual's communication status is critical in both research and practice. Describing the communication status of individuals with severe intellectual and developmental disabilities is difficult because these individuals often communicate with presymbolic means that may not be readily recognized. Our goal was to design a communication scale and summary score for interpretation that could be applied across populations of children and adults with limited (often presymbolic) communication forms. The Communication Complexity Scale (CCS) was developed by a team of researchers and tested with 178 participants with varying levels of presymbolic and early symbolic communication skills. Correlations between standardized and informant measures were completed, and expert opinions were obtained regarding the CCS. CCS scores were within expected ranges for the populations studied, and interrater reliability was high. Comparison across other measures indicated significant correlations with standardized tests of language. Scores on informant report measures tended to place children at higher levels of communication. Expert opinions generally favored the development of the CCS. The scale appears to be useful for describing a given individual's level of presymbolic or early symbolic communication. Further research is needed to determine whether it is sensitive to developmental growth in communication.

  11. Development of the Communication Complexity Scale

    PubMed Central

    Brady, Nancy C.; Fleming, Kandace; Thiemann-Bourque, Kathy; Olswang, Lesley; Dowden, Patricia; Saunders, Muriel D.

    2011-01-01

    Accurate description of an individual's communication status is critical in both research and practice. Describing the communication status of individuals with severe intellectual and developmental disabilities is difficult because these individuals often communicate with presymbolic means that may not be readily recognized. Our goal was to design a communication scale and summary score for interpretation that could be applied across populations of children and adults with limited (often presymbolic) communication forms. Methods The Communication Complexity Scale (CCS) was developed by a team of researchers and tested with 178 participants with varying levels of presymbolic and early symbolic communication skills. Correlations between standardized and informant measures were completed, and expert opinions were obtained regarding the CCS. Results CCS scores were within expected ranges for the populations studied and inter-rater reliability was high. Comparison across other measures indicated significant correlations with standardized tests of language. Scores on informant report measures tended to place children at higher levels of communication. Expert opinions generally favored the development of the CCS. Clinical implications The scale appears to be useful for describing a given individual's level of presymbolic or early symbolic communication. Further research is needed to determine if it is sensitive to developmental growth in communication. PMID:22049404

  12. Shear heating in creeping faults changes the onset of convection

    NASA Astrophysics Data System (ADS)

    Tung, R.; Poulet, T.; Alevizos, S.; Veveakis, E.; Regenauer-Lieb, K.

    2017-10-01

    The interaction between mechanical deformation of creeping faults and fluid flow in porous media has an important influence on the heat and mass transfer processes in Earth sciences. Creeping faults can act as heat sources due to the effect of shear heating and as such could be expected to alter the conditions for hydrothermal convection. In this work, we provide a finite element-based numerical framework developed to resolve the problem of heat and mass transfer in the presence of creeping faults. This framework extends the analytical approach of the linear stability analysis (LSA) frequently used to determine the bifurcation criterion for onset of convection, allowing us to study compressible cases with the option of complex geometry and/or material inhomogeneities. We demonstrate the impact of creeping faults on the onset of convection and show that shear heating—expressed through its dimensionless group the Gruntfest number Gr—has exponential influence on the critical value of the Lewis number Le (inversely proportional to the Rayleigh number Ra) required for convection: Lec ˜ Lec0 eGr. In this expression, Lec0 is the critical value of Le in the absence of shear heating. This exponential scaling shows that shear heating increases the critical Lewis number and triggers hydrothermal convection at lower permeability than in situations without it. We also show that the effect of shear heating in a fault significantly alters the pattern of convection in and around the fault zone.

  13. Dynamics of convective scale interaction

    NASA Technical Reports Server (NTRS)

    Purdom, James F. W.; Sinclair, Peter C.

    1988-01-01

    Several of the mesoscale dynamic and thermodynamic aspects of convective scale interaction are examined. An explanation of how sounding data can be coupled with satellite observed cumulus development in the warm sector and the arc cloud line's time evolution to develop a short range forecast of expected convective intensity along an arc cloud line. The formative, mature and dissipating stages of the arc cloud line life cycle are discussed. Specific properties of convective scale interaction are presented and the relationship between arc cloud lines and tornado producing thunderstorms is considered.

  14. Dynamics of convective scale interaction

    NASA Technical Reports Server (NTRS)

    Purdom, James F. W.; Sinclair, Peter C.

    1988-01-01

    Several of the mesoscale dynamic and thermodynamic aspects of convective scale interaction are examined. An explanation of how sounding data can be coupled with satellite observed cumulus development in the warm sector and the arc cloud line's time evolution to develop a short range forecast of expected convective intensity along an arc cloud line. The formative, mature and dissipating stages of the arc cloud line life cycle are discussed. Specific properties of convective scale interaction are presented and the relationship between arc cloud lines and tornado producing thunderstorms is considered.

  15. Convective Weather Avoidance with Uncertain Weather Forecasts

    NASA Technical Reports Server (NTRS)

    Karahan, Sinan; Windhorst, Robert D.

    2009-01-01

    Convective weather events have a disruptive impact on air traffic both in terminal area and in en-route airspaces. In order to make sure that the national air transportation system is safe and efficient, it is essential to respond to convective weather events effectively. Traffic flow control initiatives in response to convective weather include ground delay, airborne delay, miles-in-trail restrictions as well as tactical and strategic rerouting. The rerouting initiatives can potentially increase traffic density and complexity in regions neighboring the convective weather activity. There is a need to perform rerouting in an intelligent and efficient way such that the disruptive effects of rerouting are minimized. An important area of research is to study the interaction of in-flight rerouting with traffic congestion or complexity and developing methods that quantitatively measure this interaction. Furthermore, it is necessary to find rerouting solutions that account for uncertainties in weather forecasts. These are important steps toward managing complexity during rerouting operations, and the paper is motivated by these research questions. An automated system is developed for rerouting air traffic in order to avoid convective weather regions during the 20- minute - 2-hour time horizon. Such a system is envisioned to work in concert with separation assurance (0 - 20-minute time horizon), and longer term air traffic management (2-hours and beyond) to provide a more comprehensive solution to complexity and safety management. In this study, weather is dynamic and uncertain; it is represented as regions of airspace that pilots are likely to avoid. Algorithms are implemented in an air traffic simulation environment to support the research study. The algorithms used are deterministic but periodically revise reroutes to account for weather forecast updates. In contrast to previous studies, in this study convective weather is represented as regions of airspace that pilots

  16. Enabling Automated Graph-based Search for the Identification and Characterization of Mesoscale Convective Complexes in Satellite Datasets through Integration with the Apache Open Climate Workbench

    NASA Astrophysics Data System (ADS)

    McGibbney, L. J.; Whitehall, K. D.; Mattmann, C. A.; Goodale, C. E.; Joyce, M.; Ramirez, P.; Zimdars, P.

    2014-12-01

    We detail how Apache Open Climate Workbench (OCW) (recently open sourced by NASA JPL) was adapted to facilitate an ongoing study of Mesoscale Convective Complexes (MCCs) in West Africa and their contributions within the weather-climate continuum as it relates to climate variability. More than 400 MCCs occur annually over various locations on the globe. In West Africa, approximately one-fifth of that total occur during the summer months (June-November) alone and are estimated to contribute more than 50% of the seasonal rainfall amounts. Furthermore, in general the non-discriminatory socio-economic geospatial distribution of these features correlates with currently and projected densely populated locations. As such, the convective nature of MCCs raises questions regarding their seasonal variability and frequency in current and future climates, amongst others. However, in spite of the formal observation criteria of these features in 1980, these questions have remained comprehensively unanswered because of the untimely and subjective methods for identifying and characterizing MCCs due to limitations data-handling limitations. The main outcome of this work therefore documents how a graph-based search algorithm was implemented on top of the OCW stack with the ultimate goal of improving fully automated end-to-end identification and characterization of MCCs in high resolution observational datasets. Apache OCW as an open source project was demonstrated from inception and we display how it was again utilized to advance understanding and knowledge within the above domain. The project was born out of refactored code donated by NASA JPL from the Earth science community's Regional Climate Model Evaluation System (RCMES), a joint project between the Joint Institute for Regional Earth System Science and Engineering (JIFRESSE), and a scientific collaboration between the University of California at Los Angeles (UCLA) and NASA JPL. The Apache OCW project was then integrated back

  17. Convection coefficients at building surfaces

    NASA Astrophysics Data System (ADS)

    Kammerud, R. C.; Altmayer, E.; Bauman, F. S.; Gadgil, A.; Bohn, M.

    1982-09-01

    Correlations relating the rate of heat transfer from the surfaces of rooms to the enclosed air are being developed, based on empirical and analytic examinations of convection in enclosures. The correlations express the heat transfer rate in terms of boundary conditions relating to room geometry and surface temperatures. Work to date indicates that simple convection coefficient calculation techniques can be developed, which significantly improve accuracy of heat transfer predictions in comparison with the standard calculations recommended by ASHRAE.

  18. Dynamics of Compressible Convection and Thermochemical Mantle Convection

    NASA Astrophysics Data System (ADS)

    Liu, Xi

    The Earth's long-wavelength geoid anomalies have long been used to constrain the dynamics and viscosity structure of the mantle in an isochemical, whole-mantle convection model. However, there is strong evidence that the seismically observed large low shear velocity provinces (LLSVPs) in the lowermost mantle are chemically distinct and denser than the ambient mantle. In this thesis, I investigated how chemically distinct and dense piles influence the geoid. I formulated dynamically self-consistent 3D spherical convection models with realistic mantle viscosity structure which reproduce Earth's dominantly spherical harmonic degree-2 convection. The models revealed a compensation effect of the chemically dense LLSVPs. Next, I formulated instantaneous flow models based on seismic tomography to compute the geoid and constrain mantle viscosity assuming thermochemical convection with the compensation effect. Thermochemical models reconcile the geoid observations. The viscosity structure inverted for thermochemical models is nearly identical to that of whole-mantle models, and both prefer weak transition zone. Our results have implications for mineral physics, seismic tomographic studies, and mantle convection modelling. Another part of this thesis describes analyses of the influence of mantle compressibility on thermal convection in an isoviscous and compressible fluid with infinite Prandtl number. A new formulation of the propagator matrix method is implemented to compute the critical Rayleigh number and the corresponding eigenfunctions for compressible convection. Heat flux and thermal boundary layer properties are quantified in numerical models and scaling laws are developed.

  19. Convective heater

    DOEpatents

    Thorogood, R.M.

    1983-12-27

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation. 14 figs.

  20. Convective heater

    DOEpatents

    Thorogood, Robert M.

    1983-01-01

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

  1. Convective heater

    DOEpatents

    Thorogood, Robert M.

    1986-01-01

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

  2. Comparisons of the Vertical Development of Deep Tropical Convection and Associated Lightning Activity on a Global Basis

    NASA Technical Reports Server (NTRS)

    Williams, E.; Lin, S.; Labrada, C.; Christian, H.; Goodman, S.; Boccippio, D.; Driscoll, K.

    1999-01-01

    Simultaneous radar (13.8 Ghz) and lightning (Lightning Imaging Sensor) observations from the NASA TRMM (Tropical Rainfall Measuring Mission) spacecraft afford a new opportunity to examine differences in tropical continental and oceanic convection on a global basis, The 250 meter vertical resolution of the radar data and the approximately 17 dBZ sensitivity are well suited to providing vertical profiles of radar reflectivity over the entire tropical belt. The reflectivity profile has been shown in numerous local ground-based studies to be a good indicator of both updraft velocity and electrical activity. The radar and lightning observations for multiple satellite orbits have been integrated to produce global CAPPI's for various altitudes. At 7 km altitude, where mixed phase microphysics is known to be active, the mean reflectivity in continental convection is 10-15 dB greater than the value in oceanic convection. These results provide a sound physical basis for the order-of-magnitude contrast in lightning counts between continental and oceanic convection. These observations still beg the question, however, about the contrast in updraft velocity in these distinct convective regimes.

  3. Comparisons of the Vertical Development of Deep Tropical Convection and Associated Lightning Activity on a Global Basis

    NASA Technical Reports Server (NTRS)

    Williams, E.; Lin, S.; Labrada, C.; Christian, H.; Goodman, S.; Boccippio, D.; Driscoll, K.

    1999-01-01

    Simultaneous radar (13.8 Ghz) and lightning (Lightning Imaging Sensor) observations from the NASA TRMM (Tropical Rainfall Measuring Mission) spacecraft afford a new opportunity to examine differences in tropical continental and oceanic convection on a global basis, The 250 meter vertical resolution of the radar data and the approximately 17 dBZ sensitivity are well suited to providing vertical profiles of radar reflectivity over the entire tropical belt. The reflectivity profile has been shown in numerous local ground-based studies to be a good indicator of both updraft velocity and electrical activity. The radar and lightning observations for multiple satellite orbits have been integrated to produce global CAPPI's for various altitudes. At 7 km altitude, where mixed phase microphysics is known to be active, the mean reflectivity in continental convection is 10-15 dB greater than the value in oceanic convection. These results provide a sound physical basis for the order-of-magnitude contrast in lightning counts between continental and oceanic convection. These observations still beg the question, however, about the contrast in updraft velocity in these distinct convective regimes.

  4. Heating-insensitive scale increase caused by convective precipitation

    NASA Astrophysics Data System (ADS)

    Haerter, Jan; Moseley, Christopher; Berg, Peter

    2017-04-01

    The origin of intense convective extremes and their unusual temperature dependence has recently challenged traditional thermodynamic arguments, based on the Clausius-Clapeyron relation. In a sequence of studies (Lenderink and v. Mejgaard, Nat Geosc, 2008; Berg, Haerter, Moseley, Nat Geosc, 2013; and Moseley, Hohenegger, Berg, Haerter, Nat Geosc, 2016) the argument of convective-type precipitation overcoming the 7%/K increase in extremes by dynamical, rather than thermodynamic, processes has been promoted. How can the role of dynamical processes be approached for precipitating convective cloud? One-phase, non-precipitating Rayleigh-Bénard convection is a classical problem in complex systems science. When a fluid between two horizontal plates is sufficiently heated from below, convective rolls spontaneously form. In shallow, non-precipitating atmospheric convection, rolls are also known to form under specific conditions, with horizontal scales roughly proportional to the boundary layer height. Here we explore within idealized large-eddy simulations, how the scale of convection is modified, when precipitation sets in and intensifies in the course of diurnal solar heating. Before onset of precipitation, Bénard cells with relatively constant diameter form, roughly on the scale of the atmospheric boundary layer. We find that the onset of precipitation then signals an approximately linear (in time) increase in horizontal scale. This scale increase progresses at a speed which is rather insensitive to changes in surface temperature or changes in the rate at which boundary conditions change, hinting at spatial characteristics, rather than temperature, as a possible control on spatial scales of convection. When exploring the depth of spatial correlations, we find that precipitation onset causes a sudden disruption of order and a subsequent complete disintegration of organization —until precipitation eventually ceases. Returning to the initial question of convective

  5. A Quantitative Investigation of Entrainment and Detrainment in Numerically Simulated Convective Clouds. Pt. 1; Model Development

    NASA Technical Reports Server (NTRS)

    Cohen, Charles

    1998-01-01

    A method is developed which uses numerical tracers to make accurate diagnoses of entraimnent and detrainment rates and of the properties of the entrained and detrained air in numerically simulated clouds. The numerical advection scheme is modified to make it nondispersive, as required by the use of the tracers. Tests of the new method are made, and an appropriate definition of clouds is selected. Distributions of mixing fractions in the model consistently show maximums at the end points, for nearly undilute environmental air or nearly undilute cloud air, with a uniform distribution between. The cumulonimbus clouds simulated here entrain air that had been substantially changed by the clouds, and detrained air that is not necessarily representative of the cloud air at the same level.

  6. Convection in ice I with non-Newtonian rheology: Application to the icy Galilean satellites

    NASA Astrophysics Data System (ADS)

    Barr, Amy Courtright

    2004-12-01

    Observations from the Galileo spacecraft suggest that the Jovian icy satellites Europa, Ganymede, and Callisto have liquid water oceans beneath their icy surfaces. The outer ice I shells of the satellites represent a barrier between their surfaces and their oceans and serve to decouple fluid motions in their deep interiors from their surfaces. Understanding heat and mass transport by convection within the outer ice I shells of the satellites is crucial to understanding their geophysical and astrobiological evolution. Recent laboratory experiments suggest that deformation in ice I is accommodated by several different creep mechanisms. Newtonian deformation creep accommodates strain in warm ice with small grain sizes. However, deformation in ice with larger grain sizes is controlled by grain-size-sensitive and dislocation creep, which are non-Newtonian. Previous studies of convection have not considered this complex rheological behavior. This thesis revisits basic geophysical questions regarding heat and mass transport in the ice I shells of the satellites using a composite Newtonian/ non-Newtonian rheology for ice I. The composite rheology is implemented in a numerical convection model developed for Earth's mantle to study the behavior of an ice I shell during the onset of convection and in the stagnant lid convection regime. The conditions required to trigger convection in a conductive ice I shell depend on the grain size of the ice, and the amplitude and wavelength of temperature perturbation issued to the ice shell. If convection occurs, the efficiency of heat and mass transport is dependent on the ice grain size as well. If convection occurs, fluid motions in the ice shells enhance the nutrient flux delivered to their oceans, and coupled with resurfacing events, may provide a sustainable biogeochemical cycle. The results of this thesis suggest that evolution of ice grain size in the satellites and the details of how tidal dissipation perturbs the ice shell to

  7. A nonoscillatory, characteristically convected, finite volume scheme for multidimensional convection problems

    NASA Technical Reports Server (NTRS)

    Yokota, Jeffrey W.; Huynh, Hung T.

    1989-01-01

    A new, nonoscillatory upwind scheme is developed for the multidimensional convection equation. The scheme consists of an upwind, nonoscillatory interpolation of data to the surfaces of an intermediate finite volume; a characteristic convection of surface data to a midpoint time level; and a conservative time integration based on the midpoint rule. This procedure results in a convection scheme capable of resolving discontinuities neither aligned with, nor convected along, grid lines.

  8. Characterizing convective cold pools: Characterizing Convective Cold Pools

    DOE PAGES

    Drager, Aryeh J.; van den Heever, Susan C.

    2017-05-09

    Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

  9. Modeling of heat explosion with convection.

    PubMed

    Belk, Michael; Volpert, Vitaly

    2004-06-01

    The work is devoted to numerical simulations of the interaction of heat explosion with natural convection. The model consists of the heat equation with a nonlinear source term describing heat production due to an exothermic chemical reaction coupled with the Navier-Stokes equations under the Boussinesq approximation. We show how complex regimes appear through successive bifurcations leading from a stable stationary temperature distribution without convection to a stationary symmetric convective solution, stationary asymmetric convection, periodic in time oscillations, and finally aperiodic oscillations. A simplified model problem is suggested. It describes the main features of solutions of the complete problem.

  10. Introductory Analysis of Benard-Marangoni Convection

    ERIC Educational Resources Information Center

    Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.

    2007-01-01

    We describe experiments on Benard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and…

  11. Introductory Analysis of Benard-Marangoni Convection

    ERIC Educational Resources Information Center

    Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.

    2007-01-01

    We describe experiments on Benard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and…

  12. Properties of semi-convection and convective overshooting for massive stars

    NASA Astrophysics Data System (ADS)

    Ding, C. Y.; Li, Y.

    2014-02-01

    The properties of semi-convection and core convective overshooting of stars with masses of 15 and 30 M⊙ are calculated in the present article. New methods are used to deal with semi-convection. Different entropy gradients are used when adopting the Schwarzschild and Ledoux methods, which are used to confine the convective boundary and calculate the turbulent quantities: {{partial } overline{s}}/{{partial } r}=-({c_p}/{H_P})(nabla -nabla _ad) when the Schwarzschild method is adopted and {{partial } overline{s}}/{{partial } r}=-({c_p}/{H_P})(nabla -nabla _ad-nabla _{μ }) when the Ledoux method is adopted. Core convective overshooting and semi-convection are treated as a whole and their development is found to present almost opposing tendencies: more intensive core convective overshooting leads to weaker semi-convection. The influence of different parameters and convection processing methods on the turbulent quantities is analysed in this article. Increasing the mixing-length parameter α leads to more turbulent dynamic energy in the convective core and prolongs the overshooting distance but depresses the development of semi-convection. Adoption of the Ledoux method leads to overshooting extending further and semi-convection development being suppressed.

  13. A review of the initiation of precipitating convection in the United Kingdom

    NASA Astrophysics Data System (ADS)

    Bennett, Lindsay J.; Browning, Keith A.; Blyth, Alan M.; Parker, Douglas J.; Clark, Peter A.

    2006-04-01

    Recent severe weather events have prompted the European scientific community to assess the current understanding of convective processes with a view to more detailed and accurate forecasting. The initial development of convective cells remains one of the least understood aspects and one in which limited research has taken place. The important processes can be split into three main areas: boundary-layer forcing, upper-level forcing and secondary generation. This paper is a review of the mechanisms responsible for the initiation of precipitating convection in the United Kingdom; i.e. why convective clouds form and develop into precipitating clouds in a particular location.The topography of the United Kingdom has a large influence on the initiation of convection. Boundary-layer forcings determine the specific location where convection is triggered within larger regions of potential instability. These latter regions are created by mesoscale or synoptic-scale features at a higher level such as dry intrusions and mesoscale vortices. Second-generation cells are those formed by the interaction of outflow from convective clouds with the surrounding environmental air. Large, long-lived thunderstorm complexes can develop when new cells are repeatedly triggered on one side of the system. Current and future field campaigns along with the development of high-resolution modelling will enable these processes to be investigated in more detail than has previously been achieved.

  14. Evaluation of Model Complexity and Parameter Estimation: Indirect Inversion of a Numerical Model of Heat Conduction and Convection Using Subsurface Temperatures in Peat

    NASA Astrophysics Data System (ADS)

    Christensen, W.; Kamai, T.; Fogg, G. E.

    2012-12-01

    The presence of metal piezometers (thermal conductivity 16.0 W m-1 K-1) in peat (thermal conductivity 0.5 W m-1 K-1) can significantly influence temperatures recorded in the subsurface. Radially symmetrical 2D numerical models of heat conduction and convection that use a transient specified temperature boundary condition (Dirichlet) and explicitly account for the difference in thermal properties differ from the commonly used 1D analytical solution by as much as 2°C at 0.15m below ground surface. Field data from temperature loggers located inside and outside piezometers show similar differences, supporting the use of the more complex numerical model. In order to better simulate field data, an energy balance approach is used to calculate the temperature along the upper boundary using hourly radiation and air temperature data, along with daily average wind velocity and cloud cover data. Normally distributed random noise is added to recorded field data to address potential natural variation between conditions at the instrument site and the field site (piezometer). Five influential parameters are considered: albedo, crop coefficient, hydraulic conductivity, thermal diffusivity, and surface water depth. Ten sets of these five parameters are generated from a uniform random distribution and constrained by values reported in the literature or measured in the field. The ten parameter sets and noise are used to generate synthetic subsurface data in the numerical model. The synthetic temperature data is offset by a constant value determined from a uniform random distribution to represent potential offset in instrument accuracy (+/- 0.1 °C). The original parameter values are satisfactorily recovered by indirect inversion of the noise-free model using UCODE. Comparison of the parameter estimates from the homogeneous numerical model (equivalent to the analytical model) and the numerical model that explicitly models the metal piezometer are compared. The same inversion scheme is

  15. Development and Testing of Coupled Land-surface, PBL and Shallow/Deep Convective Parameterizations within the MM5

    NASA Technical Reports Server (NTRS)

    Stauffer, David R.; Seaman, Nelson L.; Munoz, Ricardo C.

    2000-01-01

    The objective of this investigation was to study the role of shallow convection on the regional water cycle of the Mississippi and Little Washita Basins using a 3-D mesoscale model, the PSUINCAR MM5. The underlying premise of the project was that current modeling of regional-scale climate and moisture cycles over the continents is deficient without adequate treatment of shallow convection. It was hypothesized that an improved treatment of the regional water cycle can be achieved by using a 3-D mesoscale numerical model having a detailed land-surface parameterization, an advanced boundary-layer parameterization, and a more complete shallow convection parameterization than are available in most current models. The methodology was based on the application in the MM5 of new or recently improved parameterizations covering these three physical processes. Therefore, the work plan focused on integrating, improving, and testing these parameterizations in the MM5 and applying them to study water-cycle processes over the Southern Great Plains (SGP): (1) the Parameterization for Land-Atmosphere-Cloud Exchange (PLACE) described by Wetzel and Boone; (2) the 1.5-order turbulent kinetic energy (TKE)-predicting scheme of Shafran et al.; and (3) the hybrid-closure sub-grid shallow convection parameterization of Deng. Each of these schemes has been tested extensively through this study and the latter two have been improved significantly to extend their capabilities.

  16. Effects of carbon dioxide hydration kinetics and evaporative convection on pH profile development during interfacial mass transfer of ammonia and carbon dioxide

    NASA Astrophysics Data System (ADS)

    Hafner, Sasha D.; Sommer, Sven G.; Petersen, Valdemar; Markfoged, Rikke

    2017-04-01

    Interfacial mass transfer of {NH}_3 and {CO}_2 are important in processes as diverse as {NH}_3 emission from animal manure and gas scrubbing for removal of carbon dioxide. Predicting transfer rates is complicated by bidirectional interactions between solution pH and emission rates, which may be affected by physical, chemical, and biological processes. We studied the effects of {CO}_2 hydration kinetics and evaporative convection on the development of pH profiles in solutions undergoing simultaneous emission of {NH}_3 and {CO}_2. Profiles of pH were measured at a 0.1 mm resolution over 15 h, and interpreted using a reaction-transport model. Under high humidity, surface pH increased quickly (>0.2 units in 8 min) and an increase gradually extended to deeper depths. An increase in {CO}_2 hydration and carbonic acid dehydration rates by addition of carbonic anhydrase increased the elevation of surface pH and the depth to which an increase extended, due to an increase in {CO}_2 emission. Results show that unless carbonic anhydrase is present, the equilibrium approach typically used for modeling interfacial transport of {CO}_2 and {NH}_3 will be inaccurate. Evaporation and resulting convection greatly increased mass transfer rates below an apparent surface film about 1 mm thick. Emission or absorption of {CO}_2 can produce steep gradients in pH over small distances (<0.5 to >20 mm) in systems with and without convective mixing, and the resulting surface pH, in turn, strongly affects {NH}_3 transfer. Both convection and the rate of hydration/dehydration reactions are likely to affect pH profile development and rates of {NH}_3 and {CO}_2 transfer in many systems. Accurately predicting mass transfer rates for these systems will require an understanding of these processes in the systems.

  17. Effects of carbon dioxide hydration kinetics and evaporative convection on pH profile development during interfacial mass transfer of ammonia and carbon dioxide

    NASA Astrophysics Data System (ADS)

    Hafner, Sasha D.; Sommer, Sven G.; Petersen, Valdemar; Markfoged, Rikke

    2016-09-01

    Interfacial mass transfer of NH_3 and CO_2 are important in processes as diverse as NH_3 emission from animal manure and gas scrubbing for removal of carbon dioxide. Predicting transfer rates is complicated by bidirectional interactions between solution pH and emission rates, which may be affected by physical, chemical, and biological processes. We studied the effects of CO_2 hydration kinetics and evaporative convection on the development of pH profiles in solutions undergoing simultaneous emission of NH_3 and CO_2 . Profiles of pH were measured at a 0.1 mm resolution over 15 h, and interpreted using a reaction-transport model. Under high humidity, surface pH increased quickly (>0.2 units in 8 min) and an increase gradually extended to deeper depths. An increase in CO_2 hydration and carbonic acid dehydration rates by addition of carbonic anhydrase increased the elevation of surface pH and the depth to which an increase extended, due to an increase in CO_2 emission. Results show that unless carbonic anhydrase is present, the equilibrium approach typically used for modeling interfacial transport of CO_2 and NH_3 will be inaccurate. Evaporation and resulting convection greatly increased mass transfer rates below an apparent surface film about 1 mm thick. Emission or absorption of CO_2 can produce steep gradients in pH over small distances (<0.5 to >20 mm) in systems with and without convective mixing, and the resulting surface pH, in turn, strongly affects NH_3 transfer. Both convection and the rate of hydration/dehydration reactions are likely to affect pH profile development and rates of NH_3 and CO_2 transfer in many systems. Accurately predicting mass transfer rates for these systems will require an understanding of these processes in the systems.

  18. First steps toward a new class of statistical convection models

    NASA Astrophysics Data System (ADS)

    Bristow, W. A.

    2009-12-01

    The pioneering work of Gary Abel, Mervyn Freeman [2002, 2006], and Murray Parkinson [2006] have examined the complex nature of convection observed by SuperDARN. They have shown that the convection velocity is highly variable in both time and space, with spatial and temporal correlations without characteristic scales. Current statistical convection models do not account for any variability beyond that of the IMF time series with which they are driven. They do, however, produce a pattern of convection that seem to represent the average of the observations. This work presents the initial steps toward developing a new convection model that will account for the variable nature of velocity, while retaining the average behavior of current models. The presentation examines the statistics of the velocity fluctuations and random number generators that have the same distributions. The next steps are to to enforce some temporal and spatial correlations that will generate the convection patterns observed on average. Abel, G. A., M. P. Freeman, (2002) A statistical analysis of ionospheric velocity and magnetic field power spectra at the time of pulsed ionospheric flows. J. Geophys. Res. 107, 1470, doi:10/1029/2002JA009402 Abel, G. A., M. P. Freeman, and G. Chisham (2006) Spatial structure of ionospheric convection velocities in regions of open and closed magnetic field topology. Geophys. Res. Lett. 33, doi 10.1029/2006GL027919 Parkinson, M. L., (2006) Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity. Ann. Geophys., 24, 689-705

  19. Making Educational Development and Change Sustainable: Insights from Complexity Theory

    ERIC Educational Resources Information Center

    Mason, Mark

    2009-01-01

    This article considers the challenge of sustainable change and development in education from the perspective of complexity theory. Complexity theory's concept of emergence implies that, given a significant degree of complexity in a particular environment, new properties and behaviours emerge that are not necessarily contained in the essence of the…

  20. The Solar Convection Spectrum

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  1. The Solar Convection Spectrum

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  2. Thermal Vibrational Convection

    NASA Astrophysics Data System (ADS)

    Gershuni, G. Z.; Lyubimov, D. V.

    1998-08-01

    Recent increasing awareness of the ways in which vibrational effects can affect low-gravity experiments have renewed interest in the study of thermal vibrational convection across a wide range of fields. For example, in applications where vibrational effects are used to provide active control of heat and mass transfer, such as in heat exchangers, stirrers, mineral separators and crystal growth, a sound understanding of the fundamental theory is required. In Thermal Vibrational Convection, the authors present the theory of vibrational effects caused by a static gravity field, and of fluid flows which appear under vibration in fluid-filled cavities. The first part of the book discusses fluid-filled cavities where the fluid motion only appears in the presence of temperature non-uniformities, while the second considers those situations where the vibrational effects are caused by a non-uniform field. Throughout, the authors concentrate on consideration of high frequency vibrations, where averaging methods can be successfully applied in the study of the phenomena. Written by two of the pioneers in this field, Thermal Vibrational Convection will be of great interest to scientists and engineers working in the many areas that are concerned with vibration, and its effect on heat and mass transfer. These include hydrodynamics, hydro-mechanics, low gravity physics and mechanics, and geophysics. The rigorous approach adopted in presenting the theory of this fascinating and highly topical area will facilitate a greater understanding of the phenomena involved, and will lead to the development of more and better-designed experiments.

  3. Mechanisms of secondary convection within a Mei-Yu frontal mesoscale convective system in eastern China

    NASA Astrophysics Data System (ADS)

    Xu, Xin; Xue, Ming; Wang, Yuan; Huang, Hao

    2017-01-01

    The generation of secondary convection, following an earlier episode of convection, within a heavy-rain-producing mesoscale convective system (MCS) along a Mei-Yu front in eastern China on 6-8 July 2013 is studied based on convection-permitting Weather Research and Forecasting simulations. The initiation of the secondary convection is found to be directly linked to the downward development of a mesoscale convective vortex (MCV) spawn by the MCS. In the early and mature stage, the MCV center is located at the middle troposphere; it descends gradually with time as the parent MCS began to decay, with the associated convection transitioning from deep to shallow convection. The descent of the MCV occurs in response to the lowering of the maximum diabatic heating within the convective system, which increases positive potential vorticity down below. When the MCV reaches the lower troposphere, it becomes coupled with the prefrontal southwesterly low-level jet (LLJ). The confluence of the MCV rotational flow with the LLJ notably enhances the convergence on the southern flank of the MCV, where the secondary convection is triggered and swapped through the southeastern flank of the MCV. Unlike that found in the MCV of the U.S. Central Plains, the cold pool produced by the Mei-Yu frontal MCS is rather weak and shallow and appears to play only a minor role in promoting convection. The balanced isentropic lifting by the MCV circulation is also weak, although the MCV circulation does help localize the secondary convection.

  4. Mesoscale aspects of convective storms

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1981-01-01

    The structure, evolution and mechanisms of mesoscale convective disturbances are reviewed and observation techniques for "nowcasting" their nature are discussed. A generalized mesometeorological scale is given, classifying both low and high pressure systems. Mesoscale storms are shown often to induce strong winds, but their wind speeds are significantly less than those accompanied by submesoscale disturbances, such as tornadoes, downbursts, and microbursts. Mesoscale convective complexes, severe storm wakes, and flash floods are considered. The understanding of the evolution of supercells is essential for improving nowcasting capabilities and a very accurate combination of radar and satellite measurements is required.

  5. Developing Organizational Adaptability for Complex Environment

    ERIC Educational Resources Information Center

    Boylan, Steven A.; Turner, Kenneth A.

    2017-01-01

    Developing organizations capable of adapting requires leaders to set conditions. Setting conditions normally requires purposeful activities by the leadership to foster and develop leader and individual adaptability, supported by processes and activities that enable adaptive behaviors through the totality of the organization (Goldstein, Hazy, &…

  6. Development and validation of a new LBM-MRT hybrid model with enthalpy formulation for melting with natural convection

    NASA Astrophysics Data System (ADS)

    Miranda Fuentes, Johann; Kuznik, Frédéric; Johannes, Kévyn; Virgone, Joseph

    2014-01-01

    This article presents a new model to simulate melting with natural convection of a phase change material. For the phase change problem, the enthalpy formulation is used. Energy equation is solved by a finite difference method, whereas the fluid flow is solved by the multiple relaxation time (MRT) lattice Boltzmann method. The model is first verified and validated using the data from the literature. Then, the model is applied to a tall brick filled with a fatty acid eutectic mixture and the results are presented. The main results are (1) the spatial convergence rate is of second order, (2) the new model is validated against data from the literature and (3) the natural convection plays an important role in the melting process of the fatty acid mixture considered in our work.

  7. The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels

    NASA Astrophysics Data System (ADS)

    Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

    2012-06-01

    This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

  8. Limit of Predictability in Mantle Convection

    NASA Astrophysics Data System (ADS)

    Bello, L.; Coltice, N.; Rolf, T.; Tackley, P. J.

    2013-12-01

    Linking mantle convection models with Earth's tectonic history has received considerable attention in recent years: modeling the evolution of supercontinent cycles, predicting present-day mantle structure or improving plate reconstructions. Predictions of future supercontinents are currently being made based on seismic tomography images, plate motion history and mantle convection models, and methods of data assimilation for mantle flow are developing. However, so far there are no studies of the limit of predictability these models are facing. Indeed, given the chaotic nature of mantle convection, we can expect forecasts and hindcasts to have a limited range of predictability. We propose here to use an approach similar to those used in dynamic meteorology, and more recently for the geodynamo, to evaluate the predictability limit of mantle dynamics forecasts. Following the pioneering works in weather forecast (Lorenz 1965), we study the time evolution of twin experiments, started from two very close initial temperature fields and monitor the error growth. We extract a characteristic time of the system, known as the e-folding timescale, which will be used to estimate the predictability limit. The final predictability time will depend on the imposed initial error and the error tolerance in our model. We compute 3D spherical convection solutions using StagYY (Tackley, 2008). We first evaluate the influence of the Rayleigh number on the limit of predictability of isoviscous convection. Then, we investigate the effects of various rheologies, from the simplest (isoviscous mantle) to more complex ones (plate-like behavior and floating continents). We show that the e-folding time increases with the wavelength of the flow and reaches 10Myrs with plate-like behavior and continents. Such an e-folding time together with the uncertainties in mantle temperature distribution suggests prediction of mantle structure from an initial given state is limited to <50 Myrs. References: 1

  9. Research and development complex with remote access

    NASA Astrophysics Data System (ADS)

    Panfilov, Y. V.; Kolesnik, L. L.; Ryabov, V. T.; Sidorova, S. V.

    2017-07-01

    Vacuum modular tool for thin films vacuum deposition was considered. Deposition tool automatic control system built-in to the remote access. Methodological support for the preparation of laboratory works and virtual simulator for mastering the ability to work on the vacuum deposition tool were developed.

  10. Economical Development of Complex Computer Systems

    DTIC Science & Technology

    1992-08-15

    Davis, "New Projects: Beware of False Economies," Harvard Business Review , Number 2, March-April 1985, pp. 95-96. 9 Edward G. Krubasik, "Customize Your...Product Development," Harvard Business Review Number 6, November-December 1988, p. 49. 10 Edward B. Roberts and Marc H. Meyer, "Product Strategy and

  11. Predicting Vertical Motion within Convective Storms

    NASA Astrophysics Data System (ADS)

    van den Heever, S. C.

    2016-12-01

    Convective storms are both beneficial in the fresh water they supply and destructive in the life-threatening extreme weather they produce. They are found throughout the tropics and midlatitudes, vary in structure from isolated to highly organized systems, and are the sole source of precipitation in many regions of Earth. Convective updrafts and downdrafts plays a crucial role in cloud and precipitation formation, latent heating, water vapor transport, storm organization, and large-scale atmospheric circulations such as the Hadley and Walker cells. These processes, in turn, impact the strength and longevity of updrafts and downdrafts through complex, non-linear feedbacks. In spite of the significant influence of convective updrafts and downdrafts on the weather and climate system, accurately predicting vertical motion using numerical models remains challenging. In high-resolution cloud-resolving models where vertical motion is normally resolved, significant biases exist in the predicted profiles of updraft and downdraft velocities, at least for the limited cases where observational data have been available for model evaluation. It has been suggested that feedbacks between the vertical motion and microphysical processes may be one cause of these discrepancies, however, our understanding of these feedbacks remains limited. In this talk, the results of a small field campaign conducted over northeastern Colorado designed to observe storm vertical motion and cold pool characteristics within isolated and organized deep convective storms will be described. High frequency radiosonde, radar and drone measurements of a developing through mature supercell storm updraft and cold pool will be presented and compared with RAMS simulations of the same supercell storm. An analysis of the feedbacks between the storm dynamical and microphysical processes will be presented, and implications for regional and global modeling of severe storms will be discussed.

  12. Modelling of stellar convection

    NASA Astrophysics Data System (ADS)

    Kupka, Friedrich; Muthsam, Herbert J.

    2017-07-01

    The review considers the modelling process for stellar convection rather than specific astrophysical results. For achieving reasonable depth and length we deal with hydrodynamics only, omitting MHD. A historically oriented introduction offers first glimpses on the physics of stellar convection. Examination of its basic properties shows that two very different kinds of modelling keep being needed: low dimensional models (mixing length, Reynolds stress, etc.) and "full" 3D simulations. A list of affordable and not affordable tasks for the latter is given. Various low dimensional modelling approaches are put in a hierarchy and basic principles which they should respect are formulated. In 3D simulations of low Mach number convection the inclusion of then unimportant sound waves with their rapid time variation is numerically impossible. We describe a number of approaches where the Navier-Stokes equations are modified for their elimination (anelastic approximation, etc.). We then turn to working with the full Navier-Stokes equations and deal with numerical principles for faithful and efficient numerics. Spatial differentiation as well as time marching aspects are considered. A list of codes allows assessing the state of the art. An important recent development is the treatment of even the low Mach number problem without prior modification of the basic equation (obviating side effects) by specifically designed numerical methods. Finally, we review a number of important trends such as how to further develop low-dimensional models, how to use 3D models for that purpose, what effect recent hardware developments may have on 3D modelling, and others.

  13. Mimicking semi-convection by convective overshooting

    NASA Astrophysics Data System (ADS)

    Caloi, V.; Mazzitelli, I.

    1990-12-01

    This paper investigates the behavior of so called 'semiconvection' (described by Schwarzschild, 1970; Castellani et al., 1971), of stars burning He in a convective core but exibiting an apparent spontaneous capability to partially mix into the core the matter from outside the formal boundaries of the convective region. A simple numerical algorithm based on a small and ad hoc amount of convective overshooting is presented which, if properly tuned, can mimick the effect of semiconvection in the computation of those stellar evolutionary phases in which a convective helium burning core is present. Using this algorithm, the time-consuming numerical procedures involved in the evaluation of the correct chemical profiles at the boundaries of the formally convective He core can be avoided.

  14. Complex Interplays between Phytosterols and Plastid Development.

    PubMed

    Andrade, Paola; Caudepon, Daniel; Altabella, Teresa; Arró, Montserrat; Ferrer, Albert; Manzano, David

    2017-10-09

    Isoprenoids comprise the largest class of natural compounds and are found in all kinds of organisms. In plants, they participate in both primary and specialized metabolism, playing essential roles in nearly all aspects of growth and development. The enormous diversity of this family of compounds is extensively exploited for biotechnological and biomedical applications as biomaterials, biofuels or drugs. Despite their variety of structures, all isoprenoids derive from the common C5 precursor Isopentenil diphosphate (IPP). Plants synthesize IPP through two different metabolic pathways, the mevalonic acid (MVA) and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathways that operate in the cytosol-RE and plastids, respectively. MEP-derived isoprenoids include important compounds for chloroplast function and as such, knock-out mutant plants affected in different steps of this pathway display important alterations in plastid structure. These alterations often lead to albino phenotypes and lethality at seedling stage. MVA knock-out mutant plants show, on the contrary, lethal phenotypes already exhibited at the gametophyte or embryo developmental stage. However, the recent characterization of conditional knock-down mutant plants of Farnesyl diphosphate synthase (FPS), a central enzyme in cytosolic and mitochondrial isoprenoid biosynthesis, revealed an unexpected role of this pathway in chloroplast development and plastidial isoprenoid metabolism in post-embryonic stages. Upon FPS silencing, chloroplast structure is severely altered, together with a strong reduction in the levels of MEP pathway-derived major end products. This phenotype is associated to misregulation of genes involved in stress responses predominantly belonging to JA and Fe homeostasis pathways. Transcriptomic experiments and analysis of recent literature indicate that sterols are the cause of the observed alterations through an as yet undiscovered mechanism.

  15. Numerical modelling of thermal convection related to fracture permeability in Dinantian carbonate platform, Luttelgeest, the Netherlands

    NASA Astrophysics Data System (ADS)

    Lipsey, Lindsay; Pluymaekers, Maarten; van Wees, Jan-Diederik; Limberger, Jon; Cloetingh, Sierd

    2016-04-01

    The presence of convective fluid flow in permeable layers can create zones of anomalously high temperature which can be exploited for geothermal energy. Temperature measurements from the Luttelgeest-01 (LTG-01) well in the northern onshore region of the Netherlands indicate variations in the thermal regime that could be indicative of convection. This thermal anomaly coincides with a 600 m interval (4600 - 5200 m) of Dinantian carbonates showing signs of increased fracture permeability of ~60 mD. For the purpose of geothermal energy exploration, it is of interest to know whether or not convection can occur in a particular reservoir, where convection cells are likely to develop and the temperature enhancements in convective upwellings. Three-dimensional numerical simulations provide insight on possible flow and thermal structures within the fractured carbonate interval. The development and number of convection cells is very much a time dependent process. First longitudinal rolls fill the domain, increasing in width until ultimately transforming into a more complex polyhedral structure. The model relaxes into a steady-state five-cell convection pattern. Furthermore, geometric aspects of the carbonate platform itself likely control the shape and location of upwellings. Convective upwellings can create significant temperature enhancements relative to the conductive profile and in agreement with the observations in the Luttelgeest carbonate platform. This enhancement is critically dependent on the aquifer thickness and geothermal gradient. Given a gradient of 39 °C/km and an aquifer thickness of 600 m, a temperature of 203 °C can be obtained at a depth of 4600 m directly above upwelling zones. Contrarily, downwelling zones result in a temperature of 185 °C at the same depth. This demonstrates the strong spatial variability of thermal anomalies in convective fractures aquifers at large depth, which can have a strong effect on exploration opportunity and risk of

  16. Subgrid Scale Modeling in Solar Convection Simulations using the ASH Code

    NASA Technical Reports Server (NTRS)

    Young, Y.-N.; Miesch, M.; Mansour, N. N.

    2003-01-01

    The turbulent solar convection zone has remained one of the most challenging and important subjects in physics. Understanding the complex dynamics in the solar con- vection zone is crucial for gaining insight into the solar dynamo problem. Many solar observatories have generated revealing data with great details of large scale motions in the solar convection zone. For example, a strong di erential rotation is observed: the angular rotation is observed to be faster at the equator than near the poles not only near the solar surface, but also deep in the convection zone. On the other hand, due to the wide range of dynamical scales of turbulence in the solar convection zone, both theory and simulation have limited success. Thus, cutting edge solar models and numerical simulations of the solar convection zone have focused more narrowly on a few key features of the solar convection zone, such as the time-averaged di erential rotation. For example, Brun & Toomre (2002) report computational finding of differential rotation in an anelastic model for solar convection. A critical shortcoming in this model is that the viscous dissipation is based on application of mixing length theory to stellar dynamics with some ad hoc parameter tuning. The goal of our work is to implement the subgrid scale model developed at CTR into the solar simulation code and examine how the differential rotation will be a affected as a result. Specifically, we implement a Smagorinsky-Lilly subgrid scale model into the ASH (anelastic spherical harmonic) code developed over the years by various authors. This paper is organized as follows. In x2 we briefly formulate the anelastic system that describes the solar convection. In x3 we formulate the Smagorinsky-Lilly subgrid scale model for unstably stratifed convection. We then present some preliminary results in x4, where we also provide some conclusions and future directions.

  17. IT Complexity Revolution: Intelligent Tools for the Globalised World Development

    NASA Astrophysics Data System (ADS)

    Kirilyuk, Andrei; Ulieru, Mihaela

    Globalised-civilisation interaction intensity grows exponentially, involving all dimensions and regions of planetary environment. The resulting dynamics of critically high, exploding complexity urgently needs consistent understanding and efficient management. The new, provably universal concept of unreduced dynamic complexity of real interaction processes described here provides the former and can be used as a basis for the latter, in the form of “complexity revolution” in information systems controlling such “critically globalised” civilisation dynamics. We outline the relevant dynamic complexity properties and the ensuing principles of anticipated complexity transition in information and communication systems. We then emphasize key applications of unreduced complexity concept and complexity-driven IT to various aspects of post-industrial civilisation dynamics, including intelligent communication, context-aware information and control systems, reliable genetics, integral medicine, emergent engineering, efficient risk management at the new level of socio-economic development and resulting realistic sustainability.

  18. Solar Surface Magneto-Convection

    NASA Astrophysics Data System (ADS)

    Stein, Robert F.

    2012-12-01

    We review the properties of solar magneto-convection in the top half of the convection zones scale heights (from 20 Mm below the visible surface to the surface, and then through the photosphere to the temperature minimum). Convection is a highly non-linear and nonlocal process, so it is best studied by numerical simulations. We focus on simulations that include sufficient detailed physics so that their results can be quantitatively compared with observations. The solar surface is covered with magnetic features with spatial sizes ranging from unobservably small to hundreds of megameters. Three orders of magnitude more magnetic flux emerges in the quiet Sun than emerges in active regions. In this review we focus mainly on the properties of the quiet Sun magnetic field. The Sun's magnetic field is produced by dynamo action throughout the convection zone, primarily by stretching and twisting in the turbulent downflows. Diverging convective upflows and magnetic buoyancy carry magnetic flux toward the surface and sweep the field into the surrounding downflow lanes where the field is dragged downward. The result is a hierarchy of undulating magnetic Ω- and U-loops of different sizes. New magnetic flux first appears at the surface in a mixed polarity random pattern and then collects into isolated unipolar regions due to underlying larger scale magnetic structures. Rising magnetic structures are not coherent, but develop a filamentary structure. Emerging magnetic flux alters the convection properties, producing larger, darker granules. Strong field concentrations inhibit transverse plasma motions and, as a result, reduce convective heat transport toward the surface which cools. Being cooler, these magnetic field concentrations have a shorter scale height and become evacuated. The field becomes further compressed and can reach strengths in balance with the surrounding gas pressure. Because of their small internal density, photons escape from deeper in the atmosphere. Narrow

  19. Electrodynamic properties and height of atmospheric convective boundary layer

    NASA Astrophysics Data System (ADS)

    Anisimov, S. V.; Galichenko, S. V.; Mareev, E. A.

    2017-09-01

    We consider the relations between the mixed layer height and atmospheric electric parameters affected by convective mixing. Vertical turbulent transport of radon, its progeny and electrically charged particles is described under Lagrangian stochastic framework, which is the next step to develop a consistent model for the formation of electrical conditions in the atmospheric boundary layer. Using the data from detailed and complex measurements of vertical profiles of the temperature and turbulence statistics as input, we calculated non-stationary vertical profiles of radon and its daughter products concentrations, atmospheric electric conductivity and intensity of electric field in the convective boundary layer from the morning transition through early afternoon quasi-stationary conditions. These profiles demonstrate substantial variability due to the changing turbulent regime in the evolving boundary layer. We obtained quantitative estimates of the atmospheric electric field variability range essentially related to the sunrise and convection development. It is shown that the local change in the electrical conductivity is the only factor that can change the intensity of electric field at the earth's surface more than twice during the transition from night to day. The established relations between electric and turbulent parameters of the boundary layer indicate that the effect of sunrise is more pronounced in the case when development of convection is accompanied by an increase in aerosol concentration and, hence, a decrease in local conductivity.

  20. Parameterization of Cumulus Convective Cloud Systems in Mesoscale Forecast Models

    DTIC Science & Technology

    2013-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Parameterization of Cumulus Convective Cloud Systems in...parameterization of cumulus convective clouds in mesoscale numerical weather prediction models OBJECTIVES Conduct detailed studies of cloud ...microphysical processes in order to develop a unified parameterization of boundary layer stratocumulus and trade wind cumulus convective clouds . Develop

  1. Organised convection embedded in a large-scale flow

    NASA Astrophysics Data System (ADS)

    Naumann, Ann Kristin; Stevens, Bjorn; Hohenegger, Cathy

    2017-04-01

    In idealised simulations of radiative convective equilibrium, convection aggregates spontaneously from randomly distributed convective cells into organized mesoscale convection despite homogeneous boundary conditions. Although these simulations apply very idealised setups, the process of self-aggregation is thought to be relevant for the development of tropical convective systems. One feature that idealised simulations usually neglect is the occurrence of a large-scale background flow. In the tropics, organised convection is embedded in a large-scale circulation system, which advects convection in along-wind direction and alters near surface convergence in the convective areas. A large-scale flow also modifies the surface fluxes, which are expected to be enhanced upwind of the convective area if a large-scale flow is applied. Convective clusters that are embedded in a large-scale flow therefore experience an asymmetric component of the surface fluxes, which influences the development and the pathway of a convective cluster. In this study, we use numerical simulations with explicit convection and add a large-scale flow to the established setup of radiative convective equilibrium. We then analyse how aggregated convection evolves when being exposed to wind forcing. The simulations suggest that convective line structures are more prevalent if a large-scale flow is present and that convective clusters move considerably slower than advection by the large-scale flow would suggest. We also study the asymmetric component of convective aggregation due to enhanced surface fluxes, and discuss the pathway and speed of convective clusters as a function of the large-scale wind speed.

  2. A Study of Detrainment from Deep Convection

    NASA Astrophysics Data System (ADS)

    Glenn, I. B.; Krueger, S. K.

    2014-12-01

    Uncertainty in the results of Global Climate Model simulations has been attributed to errors and simplifications in how parameterizations of convection coarsely represent the processes of entrainment, detrainment, and mixing between convective clouds and their environment. Using simulations of convection we studied these processes at a resolution high enough to explicitly resolve them. Two of several recently developed analysis techniques that allow insight into these processes at their appropriate scale are an Eulerian method of directly measuring entrainment and detrainment, and a Lagrangian method that uses particle trajectories to map convective mass flux over height and a cloud variable of interest. The authors of the Eulerian technique used it to show that the dynamics of shells of cold, humid air that surround shallow convective updrafts have important effects on the properties of air entrained and detrained from the updrafts. There is some evidence for the existence of such shells around deep convective updrafts as well, and that detrainment is more important than entrainment in determining the ultimate effect of the deep convection on the large scale environment. We present results from analyzing a simulation of deep convection through the Eulerian method as well as using Lagrangian particle trajectories to illustrate the role of the shell in the process of detrainment and mixing between deep convection and its environment.

  3. Research Methodology on Language Development from a Complex Systems Perspective

    ERIC Educational Resources Information Center

    Larsen-Freeman, Diane; Cameron, Lynne

    2008-01-01

    Changes to research methodology motivated by the adoption of a complexity theory perspective on language development are considered. The dynamic, nonlinear, and open nature of complex systems, together with their tendency toward self-organization and interaction across levels and timescales, requires changes in traditional views of the functions…

  4. Research Methodology on Language Development from a Complex Systems Perspective

    ERIC Educational Resources Information Center

    Larsen-Freeman, Diane; Cameron, Lynne

    2008-01-01

    Changes to research methodology motivated by the adoption of a complexity theory perspective on language development are considered. The dynamic, nonlinear, and open nature of complex systems, together with their tendency toward self-organization and interaction across levels and timescales, requires changes in traditional views of the functions…

  5. Combining ground-based microwave radiometer and the AROME convective scale model through 1DVAR retrievals in complex terrain: an Alpine valley case study

    NASA Astrophysics Data System (ADS)

    Martinet, Pauline; Cimini, Domenico; De Angelis, Francesco; Canut, Guylaine; Unger, Vinciane; Guillot, Remi; Tzanos, Diane; Paci, Alexandre

    2017-09-01

    A RPG-HATPRO ground-based microwave radiometer (MWR) was operated in a deep Alpine valley during the Passy-2015 field campaign. This experiment aims to investigate how stable boundary layers during wintertime conditions drive the accumulation of pollutants. In order to understand the atmospheric processes in the valley, MWRs continuously provide vertical profiles of temperature and humidity at a high time frequency, providing valuable information to follow the evolution of the boundary layer. A one-dimensional variational (1DVAR) retrieval technique has been implemented during the field campaign to optimally combine an MWR and 1 h forecasts from the French convective scale model AROME. Retrievals were compared to radiosonde data launched at least every 3 h during two intensive observation periods (IOPs). An analysis of the AROME forecast errors during the IOPs has shown a large underestimation of the surface cooling during the strongest stable episode. MWR brightness temperatures were monitored against simulations from the radiative transfer model ARTS2 (Atmospheric Radiative Transfer Simulator) and radiosonde launched during the field campaign. Large errors were observed for most transparent channels (i.e., 51-52 GHz) affected by absorption model and calibration uncertainties while a good agreement was found for opaque channels (i.e., 54-58 GHz). Based on this monitoring, a bias correction of raw brightness temperature measurements was applied before the 1DVAR retrievals. 1DVAR retrievals were found to significantly improve the AROME forecasts up to 3 km but mainly below 1 km and to outperform usual statistical regressions above 1 km. With the present implementation, a root-mean-square error (RMSE) of 1 K through all the atmospheric profile was obtained with values within 0.5 K below 500 m in clear-sky conditions. The use of lower elevation angles (up to 5°) in the MWR scanning and the bias correction were found to improve the retrievals below 1000 m. MWR

  6. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Eisa, Gaber Faheem; Chandrasekhar, S.; Larrousse, Mark; Banan, Mohsen

    1988-01-01

    The influence was studied of convection during directional solidification on the resulting microstructure of eutectics, specifically lead/tin and manganese/bismuth. A theory was developed for the influence of convection on the microstructure of lamellar and fibrous eutectics, through the effect of convection on the concentration field in the melt in front of the growing eutectic. While the theory agrees with the experimental spin-up spin-down results, it predicts that the weak convection expected due to buoyancy will not produce a measurable change in eutectic microstructure. Thus, this theory does not explain the two fold decrease in MnBi fiber size and spacing observed when MnBi-Bi is solidified in space or on Earth with a magnetic field applied. Attention was turned to the morphology of the MnBi-Bi interface and to the generation of freezing rate fluctuations by convection. Decanting the melt during solidification of MnBi-Bi eutectic showed that the MnBi phase projects into the melt ahead of the Bi matrix. Temperature measurements in a Bi melt in the vertical Bridgman-Stockbarger configuration showed temperature variations of up to 25 C. Conclusions are drawn and discussed.

  7. Documentation Driven Development for Complex Real-Time Systems

    DTIC Science & Technology

    2004-12-01

    REPORT Documentation Driven Development for Complex Real-Time Systems 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: This paper presents a novel approach...5000 REPORT DOCUMENTATION PAGE b. ABSTRACT UU c. THIS PAGE UU 2. REPORT TYPE Old Reprint 17. LIMITATION OF ABSTRACT UU 15. NUMBER OF PAGES 5d...Prescribed by ANSI Std. Z39.18 - Documentation Driven Development for Complex Real-Time Systems Report Title ABSTRACT This paper presents a novel

  8. Tropical deep convective cloud morphology

    NASA Astrophysics Data System (ADS)

    Igel, Matthew R.

    A cloud-object partitioning algorithm is developed. It takes contiguous CloudSat cloudy regions and identifies various length scales of deep convective clouds from a tropical, oceanic subset of data. The methodology identifies a level above which anvil characteristics become important by analyzing the cloud object shape. Below this level in what is termed the pedestal region, convective cores are identified based on reflectivity maxima. Identifying these regions allows for the assessment of length scales of the anvil and pedestal of the deep convective clouds. Cloud objects are also appended with certain environmental quantities from the ECMWF reanalysis. Simple geospatial and temporal assessments show that the cloud object technique agrees with standard observations of local frequency of deep-convective cloudiness. Additionally, the nature of cloud volume scale populations is investigated. Deep convection is seen to exhibit power-law scaling. It is suggested that this scaling has implications for the continuous, scale invariant, and random nature of the physics controlling tropical deep convection and therefore on the potentially unphysical nature of contemporary convective parameterizations. Deep-convective clouds over tropical oceans play important roles in Earth's climate system. The response of tropical, deep convective clouds to sea surface temperatures (SSTs) is investigated using this new data set. Several previously proposed feedbacks are examined: the FAT hypothesis, the Iris hypothesis, and the Thermostat hypothesis. When the data are analyzed per cloud object, each hypothesis is broadly found to correctly predict cloud behavior in nature, although it appears that the FAT hypothesis needs a slight modification to allow for cooling cloud top temperatures with increasing SSTs. A new response that shows that the base temperature of deep convective anvils remains approximately constant with increasing SSTs is introduced. These cloud-climate feedbacks are

  9. Skylab M518 multipurpose furnace convection analysis

    NASA Technical Reports Server (NTRS)

    Bourgeois, S. V.; Spradley, L. W.

    1975-01-01

    An analysis was performed of the convection which existed on ground tests and during skylab processing of two experiments: vapor growth of IV-VI compounds growth of spherical crystals. A parallel analysis was also performed on Skylab experiment indium antimonide crystals because indium antimonide (InSb) was used and a free surface existed in the tellurium-doped Skylab III sample. In addition, brief analyses were also performed of the microsegregation in germanium experiment because the Skylab crystals indicated turbulent convection effects. Simple dimensional analysis calculations and a more accurate, but complex, convection computer model, were used in the analysis.

  10. Developing a Measurement for Task Complexity in Flight.

    PubMed

    Zheng, Yiyuan; Lu, Yanyu; Wang, Zhen; Huang, Dan; Fu, Shan

    2015-08-01

    Task complexity is regarded as an essential metric that is related to a pilot's performance and workload. Normally, pilots follow Standard Operating Procedures (SOPs) during a flight. In this study, we developed a measurement named Task Complexity in Flight (TCIF) to represent the task complexity in the SOPs. The TCIF measurement combined four complexity components into one index: actions logic complexity (ALC), actions size complexity (ASC), information control exchange complexity (ICEC), and control mode complexity (CMC).To verify the measurement, we calculated 11 tasks during the takeoff and landing phases from the SOPs, and invited 10 pilots to perform the same tasks in a flight simulator. After flight, the TCIF results were compared with two workload measurements: the Bedford scale and heart rate. The results of TCIF and the 4 components of the 11 tasks were calculated. Further, the TCIF results showed a significant correlation with the Bedford scores (R=0.851) and were also consistent with the difference in heart rate (R=0.816). Therefore, with the increased TCIF results, both the Bedford scale and the difference in heart rate increased. TCIF was proposed based on the flight operating conditions. Although additional studies of TCIF are necessary, the results of this study suggest this measurement could effectively indicate task complexity in flight, and could also be used to guide pilot training and task allocation on the flight deck.

  11. Shallow Convection along the Sea Breeze Front and its Interaction with Horizontal Convective Rolls and Convective Cells

    NASA Astrophysics Data System (ADS)

    Khan, B. A.; Stenchikov, G. L.; Abualnaja, Y.

    2014-12-01

    Shallow convection has been studied in the sea breeze frontal zone along the Arabian Red Sea coast. This convection is forced by thermal and dynamic instabilities and generally is capped below 500 hPa. The thermally induced sea breeze modifies the desert Planetary Boundary Layer (PBL) and propagates inland as a density current. The leading edge of the denser marine air rapidly moves inland undercutting the hot and dry desert air mass. The warm air lifts up along the sea breeze front (SBF). Despite large moisture flux from the sea, the shallow convection in SBF does not cause precipitation on the most part of the Arabian coastal plane. The main focus of this research is to study the vertical structure and extent of convective activity in SBF and to differentiate flow regimes that lead to dry and wet convection. The Weather Research and Forecasting Model (WRF) has been employed at a high spatial resolution of 500 m to investigate the thermodynamic structure of the atmospheric column along the SBF. We found that convection occurs during offshore and cross-shore mean wind conditions; precipitation in SBF frequently develops in the southern region of the Red Sea along the high terrain of Al-Sarawat Mountains range, while on most of the days convection is dry in the middle region and further north of the Red Sea. The coherent structures in the PBL, horizontal convective rolls (HCRs) and open convective cells (OCCs), play an important role shaping interaction of SBF with the desert boundary layer. The HCRs develop in the midmorning along the mean wind vector and interact with the SBF. Later in the afternoon HCRs evolve into OCCs. The convection is strongest, where the HCR and OCC updrafts overlap with SBF and is weakest in their downdraft regions.

  12. Cerebellar Development and Autism Spectrum Disorder in Tuberous Sclerosis Complex.

    PubMed

    Sundberg, Maria; Sahin, Mustafa

    2015-12-01

    Approximately 50% of patients with the genetic disease tuberous sclerosis complex present with autism spectrum disorder. Although a number of studies have investigated the link between autism and tuberous sclerosis complex, the etiology of autism spectrum disorder in these patients remains unclear. Abnormal cerebellar function during critical phases of development could disrupt functional processes in the brain, leading to development of autistic features. Accordingly, the authors review the potential role of cerebellar dysfunction in the pathogenesis of autism spectrum disorder in tuberous sclerosis complex. The authors also introduce conditional knockout mouse models of Tsc1 and Tsc2 that link cerebellar circuitry to the development of autistic-like features. Taken together, these preclinical and clinical investigations indicate the cerebellum has a profound regulatory role during development of social communication and repetitive behaviors. © The Author(s) 2015.

  13. Complex Instruction: Managing Professional Development and School Culture

    ERIC Educational Resources Information Center

    Pescarmona, Isabella

    2010-01-01

    Complex Instruction (CI) is a comprehensive programme relating to curriculum development and instructional methodology, using multiple ability tasks and status interventions as key concepts. In 2006, at the end of a teacher training course, a group of primary school teachers decided to develop and experiment with original CI teaching units in…

  14. Oscillatory thermocapillary convection

    NASA Technical Reports Server (NTRS)

    Mundrane, Michael R.; Zebib, Abdelfattah

    1994-01-01

    We study thermocapillary and buoyant thermocapillary convection in rectangular cavities with aspect ratio A = 4 and Pr = 0.015. Two separate problems are considered. The first is combined buoyant thermocapillary convection with a nondeforming interface. We establish neutral curves for transition to oscillatory convection in the Re-Gr plane. It is shown that while pure buoyant convection exhibits oscillatory behavior for Gr is greater than Gr(sub cr) (where Gr(sub cr) is defined for the pure buoyant problem), pure thermocapillary convection is steady within the range of parameters tested. In the second problem, we consider the influence of surface deformation on the pure thermocapillary problem. For the range of parameters considered, thermocapillary convection remained steady.

  15. Internal Wave Generation by Convection

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel Michael

    internal gravity wave spectrum, using the Lighthill theory of wave excitation by turbulence. We use a Green's function approach, in which we convolve a convective source term with the Green's function of different internal gravity waves. The remainder of the thesis is a circuitous attempt to verify these analytical predictions. I test the predictions of Chapter 2 via numerical simulation. The first step is to identify a code suitable for this study. I helped develop the Dedalus code framework to study internal wave generation by convection. Dedalus can solve many different partial differential equations using the pseudo-spectral numerical method. In Chapter 3, I demonstrate Dedalus' ability to solve different equations used to model convection in astrophysics. I consider both the propagation and damping of internal waves, and the properties of low Rayleigh number convective steady states, in six different equation sets used in the astrophysics literature. This shows that Dedalus can be used to solve the equations of interest. Next, in Chapter 4, I verify the high accuracy of Dedalus by comparing it to the popular astrophysics code Athena in a standard Kelvin-Helmholtz instability test problem. Dedalus performs admirably in comparison to Athena, and provides a high standard for other codes solving the fully compressible Navier-Stokes equations. Chapter 5 demonstrates that Dedalus can simulate convective adjacent to a stably stratified region, by studying convective mixing near carbon flames. The convective overshoot and mixing is well-resolved, and is able to generate internal waves. Confident in Dedalus' ability to study the problem at hand, Chapter 6 describes simulations inspired by water experiments of internal wave generation by convection. The experiments exploit water's unusual property that its density maximum is at 4°C, rather than at 0°C. We use a similar equation of state in Dedalus, and study internal gravity waves generation by convection in a water

  16. Spatial localization in rotating convection and magnetoconvection

    NASA Astrophysics Data System (ADS)

    Kao, H.-C.; Knobloch, E.

    2014-01-01

    Stationary spatially localized states are present in both rotating convection and magnetoconvection. In two-dimensional convection with stress-free boundary conditions, the formation of such states is due to the interaction between convection and a large scale mode: zonal velocity in rotating convection and magnetic potential in magnetoconvection. We develop a higher order theory, a nonlocal fifth order Ginzburg-Landau equation, to describe the effects of spatial modulation near a codimension-two point. Two different bifurcation scenarios are identified. Our results shed light on numerical studies of two-dimensional convective systems with stress-free boundary conditions. This paper is dedicated to Professor Helmut Brand on the occasion of his 60th birthday.

  17. Systematic multiscale models for deep convection on mesoscales

    NASA Astrophysics Data System (ADS)

    Klein, Rupert; Majda, Andrew J.

    2006-11-01

    This paper builds on recent developments of a unified asymptotic approach to meteorological modeling [ZAMM, 80: 765 777, 2000, SIAM Proc. App. Math. 116, 227 289, 2004], which was used successfully in the development of Systematic multiscale models for the tropics in Majda and Klein [J. Atmosph. Sci. 60: 393 408, 2003] and Majda and Biello [PNAS, 101: 4736 4741, 2004]. Biello and Majda [J. Atmosph. Sci. 62: 1694 1720, 2005]. Here we account for typical bulk microphysics parameterizations of moist processes within this framework. The key steps are careful nondimensionalization of the bulk microphysics equations and the choice of appropriate distinguished limits for the various nondimensional small parameters that appear. We are then in a position to study scale interactions in the atmosphere involving moist physics. We demonstrate this by developing two systematic multiscale models that are motivated by our interest in mesoscale organized convection. The emphasis here is on multiple length scales but common time scales. The first of these models describes the short-time evolution of slender, deep convective hot towers with horizontal scale ~ 1 km interacting with the linearized momentum balance on length and time scales of (10 km/3 min). We expect this model to describe how convective inhibition may be overcome near the surface, how the onset of deep convection triggers convective-scale gravity waves, and that it will also yield new insight into how such local convective events may conspire to create larger-scale strong storms. The second model addresses the next larger range of length and time scales (10 km, 100 km, and 20 min) and exhibits mathematical features that are strongly reminiscent of mesoscale organized convection. In both cases, the asymptotic analysis reveals how the stiffness of condensation/evaporation processes induces highly nonlinear dynamics. Besides providing new theoretical insights, the derived models may also serve as a theoretical devices

  18. Time-implicit hydrodynamical simulations of stellar interiors: Application to turbulent convection

    NASA Astrophysics Data System (ADS)

    Viallet, M.

    2012-12-01

    The talk described the first results on turbulent convection in the envelope of a red giant star obtained with the MUSIC code, a new multi-dimensional time-implicit code devoted to stellar interiors (Viallet, Baraffe & Walder, A&A, 2011). Currently, most of our physical understanding of stellar interiors and evolution largely relies on one-dimensional calculations. The description of complex physical processes like time-dependent turbulent convection, rotation or MHD processes mostly relies on simplified, phenomenological approaches, with a predictive power hampered by the use of several free parameters. These approaches have now reached their limits in the understanding of stellar structure and evolution. The development of multi-dimensional hydrodynamical simulations becomes crucial to progress in the field of stellar physics and to meet the enormous observational efforts aimed at producing data of unprecedented quality (COROT, Kepler GAIA). The MUSIC code solves the hydrodynamical equations in spherical geometry and is based on the finite volume method. The talk presented implicit large eddy simulations of the turbulent convection in a cold giant envelope both in 2D and 3D and covering 80% in radius of the stellar structure. The computational domain includes both the convective envelope and a significant fraction of the radiative zone, allowing for convective penetration. These simulations provide valuable insight to improve the description of turbulent convection in 1D models

  19. Development and Application of Agglomerated Multigrid Methods for Complex Geometries

    NASA Technical Reports Server (NTRS)

    Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.

    2010-01-01

    We report progress in the development of agglomerated multigrid techniques for fully un- structured grids in three dimensions, building upon two previous studies focused on efficiently solving a model diffusion equation. We demonstrate a robust fully-coarsened agglomerated multigrid technique for 3D complex geometries, incorporating the following key developments: consistent and stable coarse-grid discretizations, a hierarchical agglomeration scheme, and line-agglomeration/relaxation using prismatic-cell discretizations in the highly-stretched grid regions. A signi cant speed-up in computer time is demonstrated for a model diffusion problem, the Euler equations, and the Reynolds-averaged Navier-Stokes equations for 3D realistic complex geometries.

  20. Sensitivity of Orographic Moist Convection to Landscape Variability: A Study of the Buffalo Creek, Colorado, Flash Flood Case of 1996.

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Warner, Thomas T.; Manning, Kevin

    2001-11-01

    A number of numerical experiments with a high-resolution mesoscale model were conducted to study the convective rainfall event that caused the 1996 Buffalo Creek, Colorado, flash flood. Different surface conditions and treatments of land surface physics were utilized to assess the sensitivity of this orographic moist convection to local and regional landscape forcing.Given accurate large-scale synoptic conditions at the lateral boundaries, the mesoscale model with a convection-resolving grid shows reasonably good skill in simulating this convective event with a lead time of up to 12 h. Sensitivity experiments show that a primary reason for this success is the use of an advanced land surface model that provides time-varying soil-moisture fields. This land surface model plays an important role in capturing the complex interactions among the land surface, the PBL, cloud-modulated radiation, and precipitation. For the case simulated, such interactions contribute to the temporal and spatial distribution of surface heating at small scales, and the convective triggering and development.Tests show that the landscape variability at small and large scales significantly affects the location and intensity of the moist convection. For example, on timescales of 6 to 12 h, differences in initial soil moisture associated with irrigation in the plains affect the evolution of the convection near the Continental Divide. Also, the surface modification by a wildfire burn influences the path of the major convective event that caused the flash flood.A watershed-based quantitative-precipitation-forecast skill score is proposed and employed. The relative success with which this severe thunderstorm is simulated over complex terrain provides some hope that the careful treatment of land surface physics in convection-resolving models can perhaps provide some useful level of predictability.

  1. Three-dimensional Spherical Simulations of Solar Convection. I. Differential Rotation and Pattern Evolution Achieved with Laminar and Turbulent States

    NASA Astrophysics Data System (ADS)

    Miesch, Mark S.; Elliott, Julian R.; Toomre, Juri; Clune, Tom L.; Glatzmaier, Gary A.; Gilman, Peter A.

    2000-03-01

    Rotationally constrained convection possesses velocity correlations that transport momentum and drive mean flows such as differential rotation. The nature of this transport can be very complex in turbulent flow regimes, where large-scale, coherent vorticity structures and mean flows can be established by smaller scale turbulence through inverse cascades. The dynamics of the highly turbulent solar convection zone therefore may be quite different than in early global-scale numerical models, which were limited by computational resources to nearly laminar flows. Recent progress in high-performance computing technology and ongoing helioseismic investigations of the dynamics of the solar interior have motivated us to develop more sophisticated numerical models of global-scale solar convection. Here we report three-dimensional simulations of compressible, penetrative convection in rotating spherical shells in both laminar and turbulent parameter regimes. The convective structure in the laminar case is dominated by ``banana cells,'' but the turbulent case is much more complex, with an intricate, rapidly evolving downflow network in the upper convection zone and an intermittent, plume-dominated structure in the lower convection zone and overshoot region. Convective patterns generally propagate prograde at low latitudes and retrograde at high latitudes relative to the local rotation. The differential rotation profiles show some similarity with helioseismic determinations of the solar rotation but still exhibit significantly more cylindrical alignment. Strong, intermittent, vortical downflow lanes and plumes play an important dynamical role in turbulent flow regimes and are responsible for significant differences relative to laminar flows with regard to momentum and energy transport and to the structure of the overshoot region at the base of the convection zone.

  2. Development of Onboard Computer Complex for Russian Segment of ISS

    NASA Technical Reports Server (NTRS)

    Branets, V.; Brand, G.; Vlasov, R.; Graf, I.; Clubb, J.; Mikrin, E.; Samitov, R.

    1998-01-01

    Report present a description of the Onboard Computer Complex (CC) that was developed during the period of 1994-1998 for the Russian Segment of ISS. The system was developed in co-operation with NASA and ESA. ESA developed a new computation system under the RSC Energia Technical Assignment, called DMS-R. The CC also includes elements developed by Russian experts and organizations. A general architecture of the computer system and the characteristics of primary elements of this system are described. The system was integrated at RSC Energia with the participation of American and European specialists. The report contains information on software simulators, verification and de-bugging facilities witch were been developed for both stand-alone and integrated tests and verification. This CC serves as the basis for the Russian Segment Onboard Control Complex on ISS.

  3. Changing Characteristics of convective storms: Results from a continental-scale convection-permitting climate simulations

    NASA Astrophysics Data System (ADS)

    Prein, A. F.; Ikeda, K.; Liu, C.; Bullock, R.; Rasmussen, R.

    2016-12-01

    Convective storms are causing extremes such as flooding, landslides, and wind gusts and are related to the development of tornadoes and hail. Convective storms are also the dominant source of summer precipitation in most regions of the Contiguous United States. So far little is known about how convective storms might change due to global warming. This is mainly because of the coarse grid spacing of state-of-the-art climate models that are not able to resolve deep convection explicitly. Instead, coarse resolution models rely on convective parameterization schemes that are a major source of errors and uncertainties in climate change projections. Convection-permitting climate simulations, with grid-spacings smaller than 4 km, show significant improvements in the simulation of convective storms by representing deep convection explicitly. Here we use a pair of 13-year long current and future convection-permitting climate simulations that cover large parts of North America. We use the Method for Object-Based Diagnostic Evaluation (MODE) that incorporates the time dimension (MODE-TD) to analyze the model performance in reproducing storm features in the current climate and to investigate their potential future changes. We show that the model is able to accurately reproduce the main characteristics of convective storms in the present climate. The comparison with the future climate simulation shows that convective storms significantly increase in frequency, intensity, and size. Furthermore, they are projected to move slower which could result in a substantial increase in convective storm-related hazards such as flash floods, debris flows, and landslides. Some regions, such as the North Atlantic, might experience a regime shift that leads to significantly stronger storms that are unrepresented in the current climate.

  4. Convective Overshoot in Stellar Interior

    NASA Astrophysics Data System (ADS)

    Zhang, Q. S.

    2015-07-01

    In stellar interiors, the turbulent thermal convection transports matters and energy, and dominates the structure and evolution of stars. The convective overshoot, which results from the non-local convective transport from the convection zone to the radiative zone, is one of the most uncertain and difficult factors in stellar physics at present. The classical method for studying the convective overshoot is the non-local mixing-length theory (NMLT). However, the NMLT bases on phenomenological assumptions, and leads to contradictions, thus the NMLT was criticized in literature. At present, the helioseismic studies have shown that the NMLT cannot satisfy the helioseismic requirements, and have pointed out that only the turbulent convection models (TCMs) can be accepted. In the first part of this thesis, models and derivations of both the NMLT and the TCM were introduced. In the second part, i.e., the work part, the studies on the TCM (theoretical analysis and applications), and the development of a new model of the convective overshoot mixing were described in detail. In the work of theoretical analysis on the TCM, the approximate solution and the asymptotic solution were obtained based on some assumptions. The structure of the overshoot region was discussed. In a large space of the free parameters, the approximate/asymptotic solutions are in good agreement with the numerical results. We found an important result that the scale of the overshoot region in which the thermal energy transport is effective is 1 HK (HK is the scale height of turbulence kinetic energy), which does not depend on the free parameters of the TCM. We applied the TCM and a simple overshoot mixing model in three cases. In the solar case, it was found that the temperature gradient in the overshoot region is in agreement with the helioseismic requirements, and the profiles of the solar lithium abundance, sound speed, and density of the solar models are also improved. In the low-mass stars of open

  5. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schroter, J.; van Heerwaarden, C. C.; Krol, M.

    2011-12-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we quantify the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself are one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw tower in the Netherlands, and conclude that knowledge of the temperature and carbon dioxide vertical profiles in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  6. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schröter, J.; van Heerwaarden, C. C.; Krol, M. C.

    2012-03-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  7. Organic aerosol processing in tropical deep convective clouds: Development of a new model (CRM-ORG) and implications for sources of particle number

    NASA Astrophysics Data System (ADS)

    Murphy, B. N.; Julin, J.; Riipinen, I.; Ekman, A. M. L.

    2015-10-01

    The difficulty in assessing interactions between atmospheric particles and clouds is due in part to the chemical complexity of the particles and to the wide range of length and timescales of processes occurring simultaneously during a cloud event. The new Cloud-Resolving Model with Organics (CRM-ORG) addresses these interactions by explicitly predicting the formation, transport, uptake, and re-release of surrogate organic compounds consistent with the volatility basis set framework within a nonhydrostatic, three-dimensional cloud-resolving model. CRM-ORG incorporates photochemical production, explicit condensation/evaporation of organic and inorganic vapors, and a comprehensive set of four different mechanisms describing particle formation from organic vapors and sulfuric acid. We simulate two deep convective cloud events over the Amazon rain forest in March 1998 and compare modeled particle size distributions with airborne observations made during the time period. The model predictions agree well with the observations for Aitken mode particles in the convective outflow (10-14 km) but underpredict nucleation mode particles by a factor of 20. A strong in-cloud particle formation process from organic vapors alone is necessary to reproduce even relatively low ultrafine particle number concentrations (~1500 cm-3). Sensitivity tests with variable initial aerosol loading and initial vertical aerosol profile demonstrate the complexity of particle redistribution and net gain or loss in the cloud. In-cloud particle number concentrations could be enhanced by as much as a factor of 3 over the base case simulation in the cloud outflow but were never reduced by more than a factor of 2 lower than the base. Additional sensitivity cases emphasize the need for constrained estimates of surface tension and affinity of organic vapors to ice surfaces. When temperature-dependent organic surface tension is introduced to the new particle formation mechanisms, the number concentration of

  8. Convection and downbursts

    Treesearch

    Joseph J. Charney; Brian E. Potter

    2017-01-01

    Convection and downbursts are connected meteorological phenomena with the potential to affect fire behavior and thereby alter the evolution of a wildland fire. Meteorological phenomena related to convection and downbursts are often discussed in the context of fire behavior and smoke. The physical mechanisms that contribute to these phenomena are interrelated, but the...

  9. Understanding of Leaf Development-the Science of Complexity.

    PubMed

    Malinowski, Robert

    2013-06-25

    The leaf is the major organ involved in light perception and conversion of solar energy into organic carbon. In order to adapt to different natural habitats, plants have developed a variety of leaf forms, ranging from simple to compound, with various forms of dissection. Due to the enormous cellular complexity of leaves, understanding the mechanisms regulating development of these organs is difficult. In recent years there has been a dramatic increase in the use of technically advanced imaging techniques and computational modeling in studies of leaf development. Additionally, molecular tools for manipulation of morphogenesis were successfully used for in planta verification of developmental models. Results of these interdisciplinary studies show that global growth patterns influencing final leaf form are generated by cooperative action of genetic, biochemical, and biomechanical inputs. This review summarizes recent progress in integrative studies on leaf development and illustrates how intrinsic features of leaves (including their cellular complexity) influence the choice of experimental approach.

  10. Convective Available Potential Energy of World Ocean

    NASA Astrophysics Data System (ADS)

    Su, Z.; Ingersoll, A. P.; Thompson, A. F.

    2012-12-01

    Here, for the first time, we propose the concept of Ocean Convective Available Potential Energy (OCAPE), which is the maximum kinetic energy (KE) per unit seawater mass achievable by ocean convection. OCAPE occurs through a different mechanism from atmospheric CAPE, and involves the interplay of temperature and salinity on the equation of state of seawater. The thermobaric effect, which arises because the thermal coefficient of expansion increases with depth, is an important ingredient of OCAPE. We develop an accurate algorithm to calculate the OCAPE for a given temperature and salinity profile. We then validate our calculation of OCAPE by comparing it with the conversion of OCAPE to KE in a 2-D numerical model. We propose that OCAPE is an important energy source of ocean deep convection and contributes to deep water formation. OCAPE, like Atmospheric CAPE, can help predict deep convection and may also provide a useful constraint for modelling deep convection in ocean GCMs. We plot the global distribution of OCAPE using data from the World Ocean Atlas 2009 (WOA09) and see many important features. These include large values of OCAPE in the Labrador, Greenland, Weddell and Mediterranean Seas, which are consistent with our present observations and understanding, but also identify some new features like the OCAPE pattern in the Antarctic Circumpolar Current (ACC). We propose that the diagnosis of OCAPE can improve our understanding of global patterns of ocean convection and deep water formation as well as ocean stratification, the meridional overturning circulation and mixed layer processes. The background of this work is briefly introduced as below. Open-ocean deep convection can significantly modify water properties both at the ocean surface and throughout the water column (Gordon 1982). Open-ocean convection is also an important mechanism for Ocean Deep Water formation and the transport of heat, freshwater and nutrient (Marshall and Schott 1999). Open

  11. "Small Talk": Developing Fluency, Accuracy, and Complexity in Speaking

    ERIC Educational Resources Information Center

    Hunter, James

    2012-01-01

    A major issue that continues to challenge language teachers is how to ensure that learners develop accuracy and complexity in their speaking, as well as fluency. Teachers know that too much corrective feedback (CF) can make learners reluctant to speak, while not enough may allow their errors to become entrenched. Furthermore, there is controversy…

  12. Economic development and wage inequality: A complex system analysis

    PubMed Central

    Pugliese, Emanuele; Pietronero, Luciano

    2017-01-01

    Adapting methods from complex system analysis, this paper analyzes the features of the complex relationship between wage inequality and the development and industrialization of a country. Development is understood as a combination of a monetary index, GDP per capita, and a recently introduced measure of a country’s economic complexity: Fitness. Initially the paper looks at wage inequality on a global scale, over the time period 1990–2008. Our empirical results show that globally the movement of wage inequality along with the ongoing industrialization of countries has followed a longitudinally persistent pattern comparable to the one theorized by Kuznets in the fifties: countries with an average level of development suffer the highest levels of wage inequality. Next, the study narrows its focus on wage inequality within the United States. By using data on wages and employment in the approximately 3100 US counties over the time interval 1990–2014, it generalizes the Fitness-Complexity metric for geographic units and industrial sectors, and then investigates wage inequality between NAICS industries. The empirical time and scale dependencies are consistent with a relation between wage inequality and development driven by institutional factors comparing countries, and by change in the structural compositions of sectors in a homogeneous institutional environment, such as the counties of the United States. PMID:28926577

  13. Environmental Complexity and Central Nervous System Development and Function

    ERIC Educational Resources Information Center

    Lewis, Mark H.

    2004-01-01

    Environmental restriction or deprivation early in development can induce social, cognitive, affective, and motor abnormalities similar to those associated with autism. Conversely, rearing animals in larger, more complex environments results in enhanced brain structure and function, including increased brain weight, dendritic branching,…

  14. Economic development and wage inequality: A complex system analysis.

    PubMed

    Sbardella, Angelica; Pugliese, Emanuele; Pietronero, Luciano

    2017-01-01

    Adapting methods from complex system analysis, this paper analyzes the features of the complex relationship between wage inequality and the development and industrialization of a country. Development is understood as a combination of a monetary index, GDP per capita, and a recently introduced measure of a country's economic complexity: Fitness. Initially the paper looks at wage inequality on a global scale, over the time period 1990-2008. Our empirical results show that globally the movement of wage inequality along with the ongoing industrialization of countries has followed a longitudinally persistent pattern comparable to the one theorized by Kuznets in the fifties: countries with an average level of development suffer the highest levels of wage inequality. Next, the study narrows its focus on wage inequality within the United States. By using data on wages and employment in the approximately 3100 US counties over the time interval 1990-2014, it generalizes the Fitness-Complexity metric for geographic units and industrial sectors, and then investigates wage inequality between NAICS industries. The empirical time and scale dependencies are consistent with a relation between wage inequality and development driven by institutional factors comparing countries, and by change in the structural compositions of sectors in a homogeneous institutional environment, such as the counties of the United States.

  15. Distribution of the Pyruvate Dehydrogenase Complex in Developing Soybean Cotyledons

    USDA-ARS?s Scientific Manuscript database

    The somewhat surprising report that storage proteins and oil are non-uniformly distributed in the cotyledons of developing soybeans prompted us to determine the spatial distribution of the mitochondrial and plastidial forms of the pyruvate dehydrogenase complex (PDC). It has been proposed that pla...

  16. Development of Three-Dimensional Completion of Complex Objects

    ERIC Educational Resources Information Center

    Soska, Kasey C.; Johnson, Scott P.

    2013-01-01

    Three-dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. This study examined infants' 3D object completion when presented with more complex stimuli. Infants…

  17. Deictic Relational Complexity and the Development of Deception

    ERIC Educational Resources Information Center

    McHugh, Louise; Barnes-Holmes, Yvonne; Barnes-Holmes, Dermot; Stewart, Ian; Dymond, Simon

    2007-01-01

    An empirical investigation of age-related development of the ability to deceive was conducted from the perspective of Relational Frame Theory, which, unlike the traditional approach, Theory of Mind, has been used to analyze deception in terms of the complexity of the relational responding involved. A derived relational responding-based protocol…

  18. Development of Three-Dimensional Completion of Complex Objects

    ERIC Educational Resources Information Center

    Soska, Kasey C.; Johnson, Scott P.

    2013-01-01

    Three-dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. This study examined infants' 3D object completion when presented with more complex stimuli. Infants…

  19. Environmental Complexity and Central Nervous System Development and Function

    ERIC Educational Resources Information Center

    Lewis, Mark H.

    2004-01-01

    Environmental restriction or deprivation early in development can induce social, cognitive, affective, and motor abnormalities similar to those associated with autism. Conversely, rearing animals in larger, more complex environments results in enhanced brain structure and function, including increased brain weight, dendritic branching,…

  20. "Small Talk": Developing Fluency, Accuracy, and Complexity in Speaking

    ERIC Educational Resources Information Center

    Hunter, James

    2012-01-01

    A major issue that continues to challenge language teachers is how to ensure that learners develop accuracy and complexity in their speaking, as well as fluency. Teachers know that too much corrective feedback (CF) can make learners reluctant to speak, while not enough may allow their errors to become entrenched. Furthermore, there is controversy…

  1. Task Complexity, Learning Opportunities, and Korean EFL Learners' Question Development

    ERIC Educational Resources Information Center

    Kim, YouJin

    2012-01-01

    Building on the cognitive and interactive perspectives of task research, the cognition hypothesis states that increasing task complexity promotes greater interaction and feedback and thus facilitates second language (L2) development (Robinson, 2001b, 2007a). To date, very little research has explored this claim during learner-learner interactions…

  2. Development of Ga-67 Maltolate Complex as an Imaging Agent

    PubMed Central

    Fazaeli, Yousef; Jalilian, Amir Reza; Mohammadpour Amini, Mostafa; Majdabadi, Abbas; Rahiminejad, Ali; Bolourinovin, Fatemeh; Pouladi, Mehraban

    2012-01-01

    Due to the antitumor activity of Gallium MAL complex, as well as recent findings on new targeted biomolecules in malignant cells through this complex, the development of radiolabeled gallium complex for future imaging studies was targeted. Ga-67 labeled 3-hydroxy-2-methyl-4H-pyran-4-onate (Ga-67 MAL) was prepared using freshly prepared Ga-67 chloride and 3-hydroxy-2-methyl-4H-pyran-4-onate in a sodium salt form in 25 min at 40° C. The stability of the complex was checked in final formulation and human serum for 24 h followed by the administration in Swiss mice for biodistribution studies. The complex was prepared in high radiochemical purity (> 97% ITLC, > 98% HPLC) and specific activity of 13-14 GBq/mmol and was stable in the presence of serum for 48 h. The partition coefficient was calculated for the compound (log p = 0.40). A detailed comparative pharmacokinetic study was performed for Ga-67 cation and Ga-67-MAL. The complex is more rapidly washed out from the circulation through kidneys and liver compared to Ga-67 cation and can be an interesting tumor imaging agent due to the fact that the cold compound is undergoing clinical trials as a safe and potential therapeutic agent for cancer. PMID:24250502

  3. Regulation of flower development in Arabidopsis by SCF complexes.

    PubMed

    Ni, Weimin; Xie, Daoxin; Hobbie, Lawrence; Feng, Baomin; Zhao, Dazhong; Akkara, Joseph; Ma, Hong

    2004-04-01

    SCF complexes are the largest and best studied family of E3 ubiquitin protein ligases that facilitate the ubiquitylation of proteins targeted for degradation. The SCF core components Skp1, Cul1, and Rbx1 serve in multiple SCF complexes involving different substrate-specific F-box proteins that are involved in diverse processes including cell cycle and development. In Arabidopsis, mutations in the F-box gene UNUSUAL FLORAL ORGANS (UFO) result in a number of defects in flower development. However, functions of the core components Cul1 and Rbx1 in flower development are poorly understood. In this study we analyzed floral phenotypes caused by altering function of Cul1 or Rbx1, as well as the effects of mutations in ASK1 and ASK2. Plants homozygous for a point mutation in the AtCUL1 gene showed reduced floral organ number and several defects in each of the four whorls. Similarly, plants with reduced AtRbx1 expression due to RNA interference also exhibited floral morphological defects. In addition, compared to the ask1 mutant, plants homozygous for ask1 and heterozygous for ask2 displayed enhanced reduction of B function, as well as other novel defects of flower development, including carpelloid sepals and an inhibition of petal development. Genetic analyses demonstrate that AGAMOUS (AG) is required for the novel phenotypes observed in the first and second whorls. Furthermore, the genetic interaction between UFO and AtCUL1 supports the idea that UFO regulates multiple aspects of flower development as a part of SCF complexes. These results suggest that SCF complexes regulate several aspects of floral development in Arabidopsis.

  4. Real-time visualization of convective transportation of solid materials at nanoscale.

    PubMed

    Wang, Zumin; Gu, Lin; Jeurgens, Lars P H; Phillipp, Fritz; Mittemeijer, Eric J

    2012-12-12

    Convective transportation of materials in the solid state occurring in a prototype solid bilayer system of Al and Si with negligible mutual solubility has been directly imaged in real time at nanoscale using a valence energy-filtered transmission electron microscope. Such solid-state convection is driven by the stress gradient developing in the bilayer system due to the amorphous to crystalline phase transformation of the Si sublayer. The process is characterized by compression experienced in the Si phase crystallizing within the Al sublayer, as well as by the development of mushroom-shaped "plumes" of Al nanocrystals in the Si sublayer as a result of compressive stress relaxation and discrete, new nucleation of crystalline Al. The real-time, atomistic observation and the thus-obtained fundamental understanding of solid-state convection enable highly sophisticated applications of such a complex process in advanced fabrication and processing of nanomaterials and solid-state devices.

  5. Numerical Simulations of Texture Development and Associated Rheological Anisotropy in Regions of Complex Mantle Flow

    NASA Astrophysics Data System (ADS)

    Blackman, D. K.; Castelnau, O.; Becker, T. W.

    2008-12-01

    The aim of this study is to compare the predictions of different micromechanical approaches that have been employed recently to study mineral alignment during flow in the upper mantle. Computational capabilities are reaching a point where the potential rheological effects of such lattice-preferred orientation (LPO) can be considered as an integral part of determining the flow pattern and evolution. But, in order to have confidence in taking this next step, the detailed behavior of the different micromechanical models needs to be understood. An important consequence of LPO development is the subsequent anisotropy of the mechanical properties. Curiously, most published geophysical studies only address the elastic anisotropy, probably because of its link with the observed seismic anisotropy. The viscoplastic (or rheological) anisotropy has received much less attention, although it may have a notable influence on regional and global convective flow pattern, which in turn controls the LPO development. Micromechanical approaches aim at linking the rheological behaviour at the grain scale, associated with the activate deformation mechanisms (dislocation glide and climb, diffusion creep, "), with the overall rheology at the sample scale, including also other mechanisms such as recrystallization. This is achieved by an evaluation of the internal stress generated by the (strong) mechanical interaction between neighbour grains. All models proposed in the literature (kinematic model, finite strain model, tangent self-consistent model, lower bound model, ") make simplifying assumptions, since the mechanical problem is very complicated. One can distinguish between rather simple models that allow some freedom in deformation of individual grains, and more advanced techniques (and generally more accurate) that require a minimum number (=4) of independent slip systems (or directional deformation mechanisms) for the plastic strain to occur. In respect to this, unlike all other models

  6. Development of a complex of activity in the solar corona

    NASA Technical Reports Server (NTRS)

    Howard, R.; Svestka, Z.

    1977-01-01

    Using Skylab observations of soft solar X-rays, the development of a complex of activity in the solar corona during its whole lifetime of seven solar rotations is studied. The basic components of the activity complex were determined to be permanently interconnected through sets of magnetic field lines, which suggests similar connections also below the photosphere. The visibility of individual loops in these connections, however, was greatly variable and typically shorter than one day. Each brightening of a coronal loop in X-rays seems to be related to a variation in the photospheric magnetic field near its footprint.

  7. Developing a complex approach to health phenomena (step 1)

    NASA Astrophysics Data System (ADS)

    Cifuentes, Myriam Patricia

    Health is a complex object for science and operative levels, partly because there are many approaches defining it but not scientifically sufficient or operatively accepted. This is relevant for health understanding but also for decision making on health related problems. "Determinants of Health" as a widely accepted theoretical proposal, identifies as problematic the reductionist view of health as the disease opposite, attempting to develop it positively according to WHO's definition, proposing a set of factors determining health outcomes. Though this allows a larger comprehension of health causes and effects, still has insufficiently defined theoretical statements and unproved assumptions which difficult understanding and effective actions orientation. Complexity deductive modeling since the insufficiently formalized frameworks, implies incorporating unmanageable object assumptions or reducing health broadness. Taking profit of Bogotá government adherence to DH proposal leading a health information system development, was possible inductive modeling since a systemic massive database (690.000 registries). In this way, DH theoretical statements about health components connectedness were explored by classic statistic approach, and by learning Bayesian networks from data (data mining). First approach showed understanding difficulties. Second was advantageous in approximating within and between determinants relationship structure. However, though DH introduces a systemic approach in considering diverse interacting elements is not empirically satisfactory to exhibit all the meaning of health complexity, because just matches analytic fashioned constructs depending on data expression. A strong networked model developing health complexity, needs the orientation by theoretical constructs as human agency and organization, to explore and understand emergent patterns of health.

  8. Towards convection-resolving climate modeling

    NASA Astrophysics Data System (ADS)

    Schar, C.; Ban, N.; Fuhrer, O.; Keller, M.; Lapillonne, X.; Leutwyler, D.; Lüthi, D.; Schlemmer, L.; Schmidli, J.; Schulthess, T. C.

    2015-12-01

    Moist convection is a fundamental process in our climate system, but is usually parameterized in climate models. The underlying approximations introduce significant uncertainties and biases, and there is thus a general thrust towards the explicit representation of convection. For climate applications, convection-resolving simulations are still very expensive, but are increasingly becoming feasible. Here we present recent results pertaining to the development and exploitation of convection-resolving regional climate models. We discuss the potential and challenges of the approach, highlight validation using decade-long simulations, explore convection-resolving climate change scenarios, and provide an outlook on the use of next-generation supercomputing architectures. Detailed results will be presented using the COSMO model over two computational domains at a horizontal resolution of 2.2 km. The first covers an extended Alpine region from Northern Italy to Northern Germany. For this domain decade-long simulations have been conducted, driven by both reanalysis as well as CMIP5 model data. Results show that explicit convection leads to significant improvements in the representation of summer precipitation, and to substantial differences in climate projections in terms of precipitation statistics. The second domain covers European (with 1536x1536x60 grid points) and the respective simulations exploit heterogeneous many-core hardware architectures. Results demonstrate realistic mesoscale processes embedded in synoptic-scale features, such as line convection along cold frontal systems, or the triggering of moist convection by propagating cold-air pools. Currently a 10-year simulation using this set up is near completion. To efficiently use GPU-based high-performance computers, the model code underwent significant development, including a rewrite of the dynamical core in C++. It is argued that today's largest supercomputers would in principle be able to support - already

  9. Pubertal development shapes perception of complex facial expressions.

    PubMed

    Motta-Mena, Natalie V; Scherf, K Suzanne

    2017-07-01

    We previously hypothesized that pubertal development shapes the emergence of new components of face processing (Scherf et al., 2012; Garcia & Scherf, 2015). Here, we evaluate this hypothesis by investigating emerging perceptual sensitivity to complex versus basic facial expressions across pubertal development. We tested pre-pubescent children (6-8 years), age- and sex-matched adolescents in early and later stages of pubertal development (11-14 years), and sexually mature adults (18-24 years). Using a perceptual staircase procedure, participants made visual discriminations of both socially complex expressions (sexual interest, contempt) that are arguably relevant to emerging peer-oriented relationships of adolescence, and basic (happy, anger) expressions that are important even in early infancy. Only sensitivity to detect complex expressions improved as a function of pubertal development. The ability to perceive these expressions is adult-like by late puberty when adolescents become sexually mature. This pattern of results provides the first evidence that pubertal development specifically influences emerging affective components of face perception in adolescence. © 2016 John Wiley & Sons Ltd.

  10. Evaluation of conductive, radiative, chemical, and convective heat transfer in complex systems using a fast-running, implicit, lumped-capacitance formulation

    SciTech Connect

    Benjamin, A.S.; Beraun, R.; Brown, N.N.; Sherman, M.P.

    1995-05-01

    Accurate finite-element simulation of 3-D nonlinear heat transfer in complex systems may require meshes composed of tens of thousands of finite elements and hours of CPU time on today`s fastest computers. To treat applications in which thousands of calculations may be necessary such as for risk assessment or design of high-temperature manufacturing processes, methods are needed which can solve these problems far more efficiently and maintain an acceptably high degree of accuracy. For this purpose, we developed the Thermal Evaluation and Matching Program for Risk Applications (TEMPRA). The primary differentiator between TEMPRA and comparable codes is its numerical formulation, which is designed to be unconditionally stable even with very large time steps, to afford good accuracy even with relatively coarse meshing, and to facilitate benchmarking/calibration through the use of adjustable parameters. Analysis for a sample problem shows that TEMPRA can obtain temperature response solutions with errors of less than 10% using approximately 1/1000 of the computer time required by a typical finite element code.

  11. Core promoter recognition complex changes accompany liver development

    PubMed Central

    D’Alessio, Joseph A.; Ng, Raymond; Willenbring, Holger; Tjian, Robert

    2011-01-01

    Recent studies of several key developmental transitions have brought into question the long held view of the basal transcriptional apparatus as ubiquitous and invariant. In an effort to better understand the role of core promoter recognition and coactivator complex switching in cellular differentiation, we have examined changes in transcription factor IID (TFIID) and cofactor required for Sp1 activation/Mediator during mouse liver development. Here we show that the differentiation of fetal liver progenitors to adult hepatocytes involves a wholesale depletion of canonical cofactor required for Sp1 activation/Mediator and TFIID complexes at both the RNA and protein level, and that this alteration likely involves silencing of transcription factor promoters as well as protein degradation. It will be intriguing for future studies to determine if a novel and as yet unknown core promoter recognition complex takes the place of TFIID in adult hepatocytes and to uncover the mechanisms that down-regulate TFIID during this critical developmental transition. PMID:21368148

  12. Development of the modern theory of polymeric complex coacervation.

    PubMed

    Sing, Charles E

    2017-01-01

    Oppositely charged polymers can undergo the process of complex coacervation, which refers to a liquid-liquid phase separation driven by electrostatic attraction. These materials have demonstrated considerable promise as the basis for complex, self-assembled materials. In this review, we provide a broad overview of the theoretical tools used to understand the physical properties of polymeric coacervates. In particular, we discuss historic theories (Voorn-Overbeek, Random Phase Approximation), and then describe recent developments in the field (Field Theoretic, Counterion Release, Molecular Simulation, and Polymer Reference Interaction Site Model methods). We provide context for these methods, and map out the patchwork of theoretical models that are used to describe a diverse array of coacervate systems. We use this review of the literature to clarify a number of important theoretical challenges remaining in our physical understanding of complex coacervation.

  13. Magneto-convection.

    PubMed

    Stein, Robert F

    2012-07-13

    Convection is the transport of energy by bulk mass motions. Magnetic fields alter convection via the Lorentz force, while convection moves the fields via the curl(v×B) term in the induction equation. Recent ground-based and satellite telescopes have increased our knowledge of the solar magnetic fields on a wide range of spatial and temporal scales. Magneto-convection modelling has also greatly improved recently as computers become more powerful. Three-dimensional simulations with radiative transfer and non-ideal equations of state are being performed. Flux emergence from the convection zone through the visible surface (and into the chromosphere and corona) has been modelled. Local, convectively driven dynamo action has been studied. The alteration in the appearance of granules and the formation of pores and sunspots has been investigated. Magneto-convection calculations have improved our ability to interpret solar observations, especially the inversion of Stokes spectra to obtain the magnetic field and the use of helioseismology to determine the subsurface structure of the Sun.

  14. 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

    2017-06-01

    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.

  15. Development of the Neurochemical Architecture of the Central Complex

    PubMed Central

    Boyan, George S.; Liu, Yu

    2016-01-01

    The central complex represents one of the most conspicuous neuroarchitectures to be found in the insect brain and regulates a wide repertoire of behaviors including locomotion, stridulation, spatial orientation and spatial memory. In this review article, we show that in the grasshopper, a model insect system, the intricate wiring of the fan-shaped body (FB) begins early in embryogenesis when axons from the first progeny of four protocerebral stem cells (called W, X, Y, Z, respectively) in each brain hemisphere establish a set of tracts to the primary commissural system. Decussation of subsets of commissural neurons at stereotypic locations across the brain midline then establishes a columnar neuroarchitecture in the FB which is completed during embryogenesis. Examination of the expression patterns of various neurochemicals in the central complex including neuropeptides, a neurotransmitter and the gas nitric oxide (NO), show that these appear progressively and in a substance-specific manner during embryogenesis. Each neuroactive substance is expressed by neurons located at stereotypic locations in a given central complex lineage, confirming that the stem cells are biochemically multipotent. The organization of axons expressing the various neurochemicals within the central complex is topologically related to the location, and hence birthdate, of the neurons within the lineages. The neurochemical expression patterns within the FB are layered, and so reflect the temporal topology present in the lineages. This principle relates the neuroanatomical to the neurochemical architecture of the central complex and so may provide insights into the development of adaptive behaviors. PMID:27630548

  16. Electrodynamics of convection in the inner magnetosphere

    NASA Technical Reports Server (NTRS)

    Spiro, R. W.; Wolf, R. A.

    1984-01-01

    During the past ten years, substantial progress has been made in the development of quantitative models of convection in the magnetosphere and of the electrodynamic processes that couple that magnetosphere and ionosphere. Using a computational scheme first proposed by Vasyliunas, the convection models under consideration separate the three-dimensional problem of convection in the inner magnetosphere/ionosphere into a pair of two-dimensional problems coupled by Birkeland currents flowing between the two regions. The logic, development, and major results of the inner magnetosphere convection model are reviewed with emphasis on ionospheric and magnetospheric currents. A major theoretical result of the models has been the clarification of the relationship between the region 1/region 2 picture of field-aligned currents and the older partial ring current/tail current interruption picture of substorm dynamics.

  17. Insect Antimicrobial Peptide Complexes Prevent Resistance Development in Bacteria

    PubMed Central

    Chernysh, Sergey; Gordya, Natalia; Suborova, Tatyana

    2015-01-01

    In recent decades much attention has been paid to antimicrobial peptides (AMPs) as natural antibiotics, which are presumably protected from resistance development in bacteria. However, experimental evolution studies have revealed prompt resistance increase in bacteria to any individual AMP tested. Here we demonstrate that naturally occurring compounds containing insect AMP complexes have clear advantage over individual peptide and small molecule antibiotics in respect of drug resistance development. As a model we have used the compounds isolated from bacteria challenged maggots of Calliphoridae flies. The compound isolated from blow fly Calliphora vicina was found to contain three distinct families of cell membrane disrupting/permeabilizing peptides (defensins, cecropins and diptericins), one family of proline rich peptides and several unknown antimicrobial substances. Resistance changes under long term selective pressure of the compound and reference antibiotics cefotaxime, meropenem and polymyxin B were tested using Escherichia coli, Klebsiella pneumonia and Acinetobacter baumannii clinical strains. All the strains readily developed resistance to the reference antibiotics, while no signs of resistance growth to the compound were registered. Similar results were obtained with the compounds isolated from 3 other fly species. The experiments revealed that natural compounds containing insect AMP complexes, in contrast to individual AMP and small molecule antibiotics, are well protected from resistance development in bacteria. Further progress in the research of natural AMP complexes may provide novel solutions to the drug resistance problem. PMID:26177023

  18. Managing Programmatic Risk for Complex Space System Developments

    NASA Technical Reports Server (NTRS)

    Panetta, Peter V.; Hastings, Daniel; Brumfield, Mark (Technical Monitor)

    2001-01-01

    Risk management strategies have become a recent important research topic to many aerospace organizations as they prepare to develop the revolutionary complex space systems of the future. Future multi-disciplinary complex space systems will make it absolutely essential for organizations to practice a rigorous, comprehensive risk management process, emphasizing thorough systems engineering principles to succeed. Project managers must possess strong leadership skills to direct high quality, cross-disciplinary teams for successfully developing revolutionary space systems that are ever increasing in complexity. Proactive efforts to reduce or eliminate risk throughout a project's lifecycle ideally must be practiced by all technical members in the organization. This paper discusses some of the risk management perspectives that were collected from senior managers and project managers of aerospace and aeronautical organizations by the use of interviews and surveys. Some of the programmatic risks which drive the success or failure of projects are revealed. Key findings lead to a number of insights for organizations to consider for proactively approaching the risks which face current and future complex space systems projects.

  19. Developing the laminar MHD forced convection flow of water/FMWNT carbon nanotubes in a microchannel imposed the uniform heat flux

    NASA Astrophysics Data System (ADS)

    Karimipour, Arash; Taghipour, Abdolmajid; Malvandi, Amir

    2016-12-01

    This paper aims to investigate magnetic field and slip effects on developing laminar forced convection of nanofluids in the microchannels. A novel mixture of water and FMWNT carbon nanotubes is used as the working fluid. To do this, fluid flow and heat transfer through a microchannel is simulated by a computer code in FORTRAN language. The mixture of FMWNT carbon nanotubes suspended in water is considered as the nanofluid. Slip velocity is supposed as the hydrodynamic boundary condition while the microchannel's lower wall is insulated and the top wall is under the effect of a constant heat flux. Moreover, the flow field is subjected to a magnetic field with a constant strength. The results are presented as the velocity, temperature and Nusselt number profiles. It is observed that nanofluid composed of water and carbon nanotubes (FMWNT) can work well to increase the heat transfer rate along the microchannel walls. Furthermore, it is indicated that imposing the magnetic field is very effective at the thermally developing region. In contrast, the magnetic field effect at fully developed region is insignificant, especially at low values of Reynolds number.

  20. Subcooled forced convection boiling of trichlorotrifluoroethane

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Panian, D. J.

    1972-01-01

    Experimental heat-transfer data were obtained for the forced-convection boiling of trichlorotrifluoroethane (R-113 or Freon-113) in a vertical annular test annular test section. The 97 data points obtained covered heat transfer by forced convection, local boiling, and fully-developed boiling. Correlating methods were obtained which accurately predicted the heat flux as a function of wall superheat (boiling curve) over the range of parameters studied.

  1. The Study on Complex Project Management in Developing Countries

    NASA Astrophysics Data System (ADS)

    Yanwen, Wang

    Different factors that can influence project performance have been identified, classified based on their nature, and discussed. Due to the inherent complexity and various problems encountered in implementing infrastructure project in developing countries, the project manager must appreciate the project environment, maintain flexibility, and be competent to analyze the nature of associated problems and their adverse effects on the success of the project, and address these promptly.

  2. PROPAGATION OF GRAVITY WAVES IN A CONVECTIVE LAYER

    SciTech Connect

    Onofri, M.; Vecchio, A.; Veltri, P.; De Masi, G.

    2012-02-10

    We perform numerical simulations of gravity mode propagation in a convective layer to investigate the observed association between small spatial scales and low frequencies in the photospheric velocity fields. According to the linear theory, when the fluid layer is convectively unstable, gravity modes are evanescent waves. However, in simple two-dimensional numerical settings, we find that when the equilibrium structure is modified by coherent large-scale convective motions, the waves injected at the bottom of the layer are no longer evanescent. In this situation, gravity waves can be detected at the surface of the layer. In our simplified model the injected wave's frequency remains unchanged, but its amplitude has a spatial modulation determined by the convective structure. This result may explain some analyses done with the proper orthogonal decomposition method of the solar surface velocity field even though solar convection is far more complex than the convection model considered here.

  3. The development of complex tooth shape in reptiles

    PubMed Central

    Zahradnicek, Oldrich; Buchtova, Marcela; Dosedelova, Hana; Tucker, Abigail S.

    2014-01-01

    Reptiles have a diverse array of tooth shapes, from simple unicuspid to complex multicuspid teeth, reflecting functional adaptation to a variety of diets and eating styles. In addition to cusps, often complex longitudinal labial and lingual enamel crests are widespread and contribute to the final shape of reptile teeth. The simplest shaped unicuspid teeth have been found in piscivorous or carnivorous ancestors of recent diapsid reptiles and they are also present in some extant carnivores such as crocodiles and snakes. However, the ancestral tooth shape for squamate reptiles is thought to be bicuspid, indicating an insectivorous diet. The development of bicuspid teeth in lizards has recently been published, indicating that the mechanisms used to create cusps and crests are very distinct from those that shape cusps in mammals. Here, we introduce the large variety of tooth shapes found in lizards and compare the morphology and development of bicuspid, tricuspid, and pentacuspid teeth, with the aim of understanding how such tooth shapes are generated. Next, we discuss whether the processes used to form such morphologies are conserved between divergent lizards and whether the underlying mechanisms share similarities with those of mammals. In particular, we will focus on the complex teeth of the chameleon, gecko, varanus, and anole lizards using SEM and histology to compare the tooth crown morphology and embryonic development. PMID:24611053

  4. The development of complex tooth shape in reptiles.

    PubMed

    Zahradnicek, Oldrich; Buchtova, Marcela; Dosedelova, Hana; Tucker, Abigail S

    2014-01-01

    Reptiles have a diverse array of tooth shapes, from simple unicuspid to complex multicuspid teeth, reflecting functional adaptation to a variety of diets and eating styles. In addition to cusps, often complex longitudinal labial and lingual enamel crests are widespread and contribute to the final shape of reptile teeth. The simplest shaped unicuspid teeth have been found in piscivorous or carnivorous ancestors of recent diapsid reptiles and they are also present in some extant carnivores such as crocodiles and snakes. However, the ancestral tooth shape for squamate reptiles is thought to be bicuspid, indicating an insectivorous diet. The development of bicuspid teeth in lizards has recently been published, indicating that the mechanisms used to create cusps and crests are very distinct from those that shape cusps in mammals. Here, we introduce the large variety of tooth shapes found in lizards and compare the morphology and development of bicuspid, tricuspid, and pentacuspid teeth, with the aim of understanding how such tooth shapes are generated. Next, we discuss whether the processes used to form such morphologies are conserved between divergent lizards and whether the underlying mechanisms share similarities with those of mammals. In particular, we will focus on the complex teeth of the chameleon, gecko, varanus, and anole lizards using SEM and histology to compare the tooth crown morphology and embryonic development.

  5. Pcr by Thermal Convection

    NASA Astrophysics Data System (ADS)

    Braun, Dieter

    The Polymerase Chain Reaction (PCR) allows for highly sensitive and specific amplification of DNA. It is the backbone of many genetic experiments and tests. Recently, three labs independently uncovered a novel and simple way to perform a PCR reaction. Instead of repetitive heating and cooling, a temperature gradient across the reaction vessel drives thermal convection. By convection, the reaction liquid circulates between hot and cold regions of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates into twice the amount in the cold region. The amplification progresses exponentially as the convection moves on. We review the characteristics of the different approaches and show the benefits and prospects of the method.

  6. Effects of Deep Convection on Atmospheric Chemistry

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth E.

    2007-01-01

    This presentation will trace the important research developments of the last 20+ years in defining the roles of deep convection in tropospheric chemistry. The role of deep convection in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep convection have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep convection occurring over polluted continental regions would cause downstream enhancements in photochemical ozone production in the middle and upper troposphere due to the vertical redistribution of ozone precursors. Particularly large post-convective enhancements of ozone production were estimated for convection occurring over regions of pollution from biomass burning and urban areas. These estimates were verified by measurements taken downstream of biomass burning regions of South America. Models also indicate that convective transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that convective downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep convection are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in convective outflow, and the potential fix stratosphere-troposphere exchange in thunderstorm anvils. The remainder of the talk will focus on production of NO by lightning, its subsequent transport within convective clouds . and its effects on downwind ozone production. Recent applications of cloud/chemistry model simulations combined with anvil NO and lightning flash observations in estimating NO Introduction per flash will be described. These cloud-resolving case-study simulations of convective transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning

  7. Effects of Deep Convection on Atmospheric Chemistry

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth E.

    2007-01-01

    This presentation will trace the important research developments of the last 20+ years in defining the roles of deep convection in tropospheric chemistry. The role of deep convection in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep convection have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep convection occurring over polluted continental regions would cause downstream enhancements in photochemical ozone production in the middle and upper troposphere due to the vertical redistribution of ozone precursors. Particularly large post-convective enhancements of ozone production were estimated for convection occurring over regions of pollution from biomass burning and urban areas. These estimates were verified by measurements taken downstream of biomass burning regions of South America. Models also indicate that convective transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that convective downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep convection are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in convective outflow, and the potential fix stratosphere-troposphere exchange in thunderstorm anvils. The remainder of the talk will focus on production of NO by lightning, its subsequent transport within convective clouds . and its effects on downwind ozone production. Recent applications of cloud/chemistry model simulations combined with anvil NO and lightning flash observations in estimating NO Introduction per flash will be described. These cloud-resolving case-study simulations of convective transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning

  8. Development of a two-dimensional zonally averaged statistical-dynamical model. Part I. The parameterization of moist convection and its role in the general circulation

    SciTech Connect

    Yao, M.S.; Stone, P.H.

    1987-01-01

    The moist convection parameterization used in the GISS 3-D GCM is adapted for use in a two-dimensional (2-D) zonally averaged statistical-dynamical model. Experiments with different versions of the parameterization show that its impact on the general circulation in the 2-D model does not parallel its impact in the 3-D model unless the effect of zonal variations is parameterized in the moist convection calculations. A parameterization of the variations in moist static energy is introduced in which the temperature variations are calculated from baroclinic stability theory, and the relative humidity is assumed to be constant. Inclusion of the zonal variations of moist static energy in the 2-D moist convection parameterization allows just a fraction of a latitude circle to be unstable and enhances the amount of deep convection. This leads to a 2-D simulation of the general circulation very similar to that in the 3-D model. The experiments show that the general circulation is sensitive to the parameterized amount of deep convection in the subsident branch of the Hadley cell. The more there is, the weaker are the Hadley cell circulations and the westerly jets. The experiments also confirm the effects of momentum mixing associated with moist convection found by earlier investigators and, in addition, show that the momentum mixing weakens the Ferrel cell. An experiment in which the moist convection was removed while the hydrological cycle was retained and the eddy forcing was held fixed shows that moist convection by itself stabilizes the tropics, reduces the Hadley circulation, and reduces the maximum speeds in the westerly jets.

  9. Development of a two-dimensional zonally averaged statistical-dynamical model. I - The parameterization of moist convection and its role in the general circulation

    NASA Technical Reports Server (NTRS)

    Yao, Mao-Sung; Stone, Peter H.

    1987-01-01

    The moist convection parameterization used in the GISS 3-D GCM is adapted for use in a two-dimensional (2-D) zonally averaged statistical-dynamical model. Experiments with different versions of the parameterization show that its impact on the general circulation in the 2-D model does not parallel its impact in the 3-D model unless the effect of zonal variations is parameterized in the moist convection calculations. A parameterization of the variations in moist static energy is introduced in which the temperature variations are calculated from baroclinic stability theory, and the relative humidity is assumed to be constant. Inclusion of the zonal variations of moist static energy in the 2-D moist convection parameterization allows just a fraction of a latitude circle to be unstable and enhances the amount of deep convection. This leads to a 2-D simulation of the general circulation very similar to that in the 3-D model. The experiments show that the general circulation is sensitive to the parameterized amount of deep convection in the subsident branch of the Hadley cell. The more there is, the weaker are the Hadley cell circulations and the westerly jets. The experiments also confirm the effects of momentum mixing associated with moist convection found by earlier investigators and, in addition, show that the momentum mixing weakens the Ferrel cell. An experiment in which the moist convection was removed while the hydrological cycle was retained and the eddy forcing was held fixed shows that moist convection by itself stabilizes the tropics, reduces the Hadley circulation, and reduces the maximum speeds in the westerly jets.

  10. The relationship between force and focal complex development

    PubMed Central

    Galbraith, Catherine G.; Yamada, Kenneth M.; Sheetz, Michael P.

    2002-01-01

    To adhere and migrate, cells must be capable of applying cytoskeletal force to the extracellular matrix (ECM) through integrin receptors. However, it is unclear if connections between integrins and the ECM are immediately capable of transducing cytoskeletal contraction into migration force, or whether engagement of force transmission requires maturation of the adhesion. Here, we show that initial integrin–ECM adhesions become capable of exerting migration force with the recruitment of vinculin, a marker for focal complexes, which are precursors of focal adhesions. We are able to induce the development of focal complexes by the application of mechanical force to fibronectin receptors from inside or outside the cell, and we are able to extend focal complex formation to vitronectin receptors by the removal of c-Src. These results indicate that cells use mechanical force as a signal to strengthen initial integrin–ECM adhesions into focal complexes and regulate the amount of migration force applied to individual adhesions at localized regions of the advancing lamella. PMID:12446745

  11. Cb-TRAM: Tracking and monitoring severe convection from onset over rapid development to mature phase using multi-channel Meteosat-8 SEVIRI data

    NASA Astrophysics Data System (ADS)

    Zinner, T.; Mannstein, H.; Tafferner, A.

    2008-10-01

    Cb-TRAM is a new fully automated tracking and nowcasting algorithm. Intense convective cells are detected, tracked and discriminated with respect to onset, rapid development, and mature phase. The detection is based on Meteosat-8 SEVIRI (Spinning Enhanced Visible and Infra-Red Imager) data from the broad band high resolution visible, infra-red 6.2 µm (water vapour), and the infra-red 10.8 µm channels. In addition, tropopause temperature data from ECMWF operational model analyses is utilised as an adaptive detection criterion. The tracking is based on geographical overlap between current detections and first guess patterns of cells predicted from preceeding time steps. The first guess patterns as well as short range forecast extrapolations are obtained with the aid of a new image matching algorithm providing complete fields of approximate differential cloud motion. Based on these motion vector fields interpolation and extrapolation of satellite data are obtained which allow to generate synthetic intermediate data fields between two known fields as well as nowcasts of motion and development of detected areas. Examples of the application of Cb-TRAM and a comparison to precipitation radar and lightning data as independent data sources demonstrate the capabilities of the new technique.

  12. Convective Radio Occultations Final Campaign Summary

    SciTech Connect

    Biondi, R.

    2016-03-01

    Deep convective systems are destructive weather phenomena that annually cause many deaths and injuries as well as much damage, thereby accounting for major economic losses in several countries. The number and intensity of such phenomena have increased over the last decades in some areas of the globe. Damage is mostly caused by strong winds and heavy rain parameters that are strongly connected to the structure of the particular storm. Convection over land is usually stronger and deeper than over the ocean and some convective systems, known as supercells, also develop tornadoes through processes that remain mostly unclear. The intensity forecast and monitoring of convective systems is one of the major challenges for meteorology because in situ measurements during extreme events are too sparse or unreliable and most ongoing satellite missions do not provide suitable time/space coverage.

  13. [Development and Validation of a Screening Instrument for Complex PTSD].

    PubMed

    Dorr, Florence; Firus, Christian; Kramer, Rolf; Bengel, Jürgen

    2016-11-01

    Chronic interpersonal traumata systematically result in psychological impairments referred to as complex post-traumatic stress disorder (cPTSD or DESNOS). This diagnosis will be newly established in the ICD-11 system. However, there is need for diagnostic instruments to assess cPTSD. The aim was to develop a screening form to identify patients at risk for cPTSD. The Screening for complex PTSD (SkPTBS) tests a) experience of potential traumatic events, b) related influential features and risk factors, and c) symptoms of cPTSD. 325 patients (mean age 51.5±8.7 years; 62.1% female) filled out the screening instrument at the beginning of their inpatient psychotherapy. The primary criterion for testing SkPTBS validity was the diagnosis of complex PTSD at the end of the inpatient treatment. The proportion of patients with cPTSD was 8.9% (n=29). SkPTBS items were selective, and the scale showed very good reliability (α=0.91). Factor analysis revealed a one-dimensional structure. SkPTBS total values predicted having cPTSD diagnosis and were correlated with global symptom severity (SCL-90-R) and depressive symptoms (BDI-II). There is evidence for high clinical utility of SkPTBS. A revised version was developed. © Georg Thieme Verlag KG Stuttgart · New York.

  14. The Development and Study of Surface Bound Ruthenium Organometallic Complexes

    NASA Astrophysics Data System (ADS)

    Abbott, Geoffrey Reuben

    The focus of this project has been on the use of mono-diimine ruthenium organometallic complexes, of the general structure [H(Ru)(CO)(L)2(L') 2][PF6] (L=PPh3, DPPENE and L'=Bpy, DcBpy, MBpyC, Phen, AminoPhen) bound to surfaces as luminescent probes. Both biological and inorganic/organic hybrid surfaces have been studied. The complexes were characterized both bound and unbound using standard analytical techniques such as NMR, IR and X-ray crystallography, as well as through several photophysical methods as well. Initially the study focused on how the photophyscial properties of the complexes were affected by incorporation into biological membranes. It was found that by conjugating the probes to a more rigid cholesterol moiety that luminescence was conserved, compared to conjugation with a far more flexible lipid moiety, where luminescence was either lost or reduced. Both the cholesterol and lipid conjugates were able to insert into a lipid membrane, and in the more rigid environment some of the lipid conjugates regained some of their luminescence, but often blue shifted and reduced, depending on the conjugation site. Silica Polyamine Composites (SPCs) were a hybrid material developed in the Rosenberg Lab as useful metal separation materials, that could be easily modified, and had several benefits over current commercially available polymers, or inorganic materials. These SPCs also provided an opportunity for the development of a heterogeneous platform for luminescent complexes as either catalysts or sensors. Upon binding of the luminescent Ru complexes to the surface no loss, or major change in luminescence was seen, however, when bound to the rigid surface a significant increase in excited state lifetime was measured. It is likely that through binding and interacting with the surface that the complexes lost non-radiative decay pathways, resulting in the increase in lifetime, however, these interactions do not seem to affect the energy level of the MLCT band in a

  15. EFFECTS OF PENETRATIVE CONVECTION ON SOLAR DYNAMO

    SciTech Connect

    Masada, Youhei; Yamada, Kohei; Kageyama, Akira

    2013-11-20

    Spherical solar dynamo simulations are performed. A self-consistent, fully compressible magnetohydrodynamic system with a stably stratified layer below the convective envelope is numerically solved with a newly developed simulation code based on the Yin-Yang grid. The effects of penetrative convection are studied by comparing two models with and without the stable layer. The differential rotation profile in both models is reasonably solar-like with equatorial acceleration. When considering the penetrative convection, a tachocline-like shear layer is developed and maintained beneath the convection zone without assuming any forcing. While the turbulent magnetic field becomes predominant in the region where the convective motion is vigorous, mean-field components are preferentially organized in the region where the convective motion is less vigorous. Particularly in the stable layer, the strong, large-scale field with a dipole symmetry is spontaneously built up. The polarity reversal of the mean-field component takes place globally and synchronously throughout the system regardless of the presence of the stable layer. Our results suggest that the stably stratified layer is a key component for organizing the large-scale strong magnetic field, but is not essential for the polarity reversal.

  16. Vorticity imbalance and stability in relation to convection

    NASA Technical Reports Server (NTRS)

    Read, W. L.; Scoggins, J. R.

    1977-01-01

    A complete synoptic-scale vorticity budget was related to convection storm development in the eastern two-thirds of the United States. The 3-h sounding interval permitted a study of time changes of the vorticity budget in areas of convective storms. Results of analyses revealed significant changes in values of terms in the vorticity equation at different stages of squall line development. Average budgets for all areas of convection indicate systematic imbalance in the terms in the vorticity equation. This imbalance resulted primarily from sub-grid scale processes. Potential instability in the lower troposphere was analyzed in relation to the development of convective activity. Instability was related to areas of convection; however, instability alone was inadequate for forecast purposes. Combinations of stability and terms in the vorticity equation in the form of indices succeeded in depicting areas of convection better than any one item separately.

  17. Development of a complex orientation program for multidisciplinary training.

    PubMed

    Hemingway, Maureen; Morrissey, Lisa

    2013-06-01

    Providing complex orientation and multidisciplinary training for perioperative personnel of a newly constructed health care facility with new surgical suites proved both challenging and valuable to nurse leaders. Despite the need for such training, a program to teach groups across all disciplines regarding technological advances specific to the OR and to orient them to a new facility did not exist previously. To address this, we developed a multiphase educational initiative that involved orientation, technology training, and multidisciplinary simulation. The project required extensive planning, high-level collaboration, and use of the hospital's information technology systems, all while staff members continued to provide care for patients undergoing surgically complex procedures. The successful implementation of this program ensured that staff members were proficient in new OR technology and oriented to the new facility before occupancy began. Copyright © 2013 AORN, Inc. Published by Elsevier Inc. All rights reserved.

  18. Convective Draft Structure and Transport Over the Amazonian Rain Forest

    NASA Astrophysics Data System (ADS)

    Scala, John Richard

    1990-01-01

    Field observations acquired during two expeditions to the Amazon rain forest of Brazil (ABLE-2A, ABLE-2B), and two-dimensional moist cloud model simulations are used to determine: (1) the vertical structure of convective up- and downdrafts, (2) the major levels of entrainment and detrainment, and (3) the role of temperature and moisture in convective scale transport over the continental tropics. The thermodynamic and kinematic structure of the convective troposphere is obtained from aircraft surveys flown during the dry season and a surface-based network triangle designed for wet season multi-instrumental sampling. Dry season deep convection develops in an environment marked by a mid-tropospheric minimum in equivalent potential temperature. The available supply of cool, dry air supports penetrating downdrafts which feed propagating gust fronts at the surface. Model results indicate the existence of organized cloud fields characterized by multiple updraft cores. The upward vertical transport of air from the subcloud layer to a broad anvil is accomplished without extensive mid-level detrainment. Undilute cores are required to perform the vertical exchange in the presence of mid-tropospheric heat and moisture sinks. Marked moisture gradients are absent in the well -mixed environment of the wet season. Model predicted column heating budgets suggest the evaporation of rainwater into a rear inflow is insufficient to sustain strong downdrafts or an extensive surface cool pool. Complex mid-tropospheric circulations, particularly the existence of a rotor, account for the observed redistribution of a conservative tracer. Undilute transport of boundary layer air to the upper troposphere is markedly reduced by multiple levels of detrainment. In one case, greater than 50% of the air transported to the anvil region originated at or above 6 km rather than directly from the boundary layer. The vertical distribution of boundary layer aerosols in the presence of convection is

  19. Impact assessment procedures for sustainable development: A complexity theory perspective

    SciTech Connect

    Nooteboom, Sibout

    2007-10-15

    The author assumes that effective Impact Assessment procedures should somehow contribute to sustainable development. There is no widely agreed framework for evaluating such effectiveness. The author suggests that complexity theories may offer criteria. The relevant question is 'do Impact Assessment Procedures contribute to the 'requisite variety' of a social system for it to deal with changing circumstances?' Requisite variety theoretically relates to the capability of a system to deal with changes in its environment. The author reconstructs how thinking about achieving sustainable development has developed in a sequence of discourses in The Netherlands since the 1970s. Each new discourse built on the previous ones, and is supposed to have added to 'requisite variety'. The author asserts that Impact Assessment procedures may be a necessary component in such sequences and derives possible criteria for effectiveness.

  20. Aircraft stress sequence development: A complex engineering process made simple

    NASA Technical Reports Server (NTRS)

    Schrader, K. H.; Butts, D. G.; Sparks, W. A.

    1994-01-01

    Development of stress sequences for critical aircraft structure requires flight measured usage data, known aircraft loads, and established relationships between aircraft flight loads and structural stresses. Resulting cycle-by-cycle stress sequences can be directly usable for crack growth analysis and coupon spectra tests. Often, an expert in loads and spectra development manipulates the usage data into a typical sequence of representative flight conditions for which loads and stresses are calculated. For a fighter/trainer type aircraft, this effort is repeated many times for each of the fatigue critical locations (FCL) resulting in expenditure of numerous engineering hours. The Aircraft Stress Sequence Computer Program (ACSTRSEQ), developed by Southwest Research Institute under contract to San Antonio Air Logistics Center, presents a unique approach for making complex technical computations in a simple, easy to use method. The program is written in Microsoft Visual Basic for the Microsoft Windows environment.

  1. Conditions of the Asthenosphere Layer Appearance during Upper-Mantle Convection

    NASA Astrophysics Data System (ADS)

    Sharapov, V. N.; Perepechko, Y. V.; Sorokin, K.

    2012-12-01

    The upper mantle parameters responsible to the asthenosphere appearance during convection have been studied. Many geophysical models of the earth mantle have a continuous layer of a partially melted upper-mantle material under the lithosphere plate. From the period of the early earth this structure is possible only if there is the upper-mantle convection due to 660 km depth phase transition. The previous research considered hydrodynamic conditions of the general mantle convective systems taking into account phase boundaries within the upper mantle. In this work, based on numerical modeling, we discuss thermodynamic conditions of the asthenosphere layer evolution under a homogeneous lithospheric plate. Convection in the upper mantle is modeled using the Boussinesq approximation provided spatially distributed phase transitions within the upper mantle. The problem was solved using the control volume method, which provides integral conservation laws. The results of modeling show that the convective instability is possible when the temperature at the mantle boundary is Tb~1410÷1450°C. Decompression melting of the upper mantle rocks take place if Tb>1650°C. The starting temperatures at the lower boundary of the upper mantle are 1700÷1950°C result in the appearance of the asthenosphere layer existing for 30÷100 Ma. In this case the development of complex, separated asthenosphere zones with additional convective cells is typical. Further evolution results in decay of the melting elements and their final disappearance. The initial phase of the evolution of the asthenosphere zones lasts for about 30÷100 Ma. The second, longer phase of decompression melting contains periodical melting elements with the sizes coextensive to lava sheets of intraplate volcanoes. If Tb>1950°C, the evolution of the asthenosphere is different: after the decay of large asthenosphere zones we observe a reconstruction of convective cells; in this case spatial 'wandering' of varying melting

  2. A vortex flow intensified by thermal convection

    NASA Astrophysics Data System (ADS)

    Makhmalbaf, M. H.; Liu, Tianshu; Merati, Parviz

    2017-01-01

    This paper describes a thermal-convection-intensified vortex flow within a rotating cylinder with a counter-rotating heated disk located below. This flow tends to mimic certain aspects of the intriguing flow structure of the great red spot in Jupiter by using a simple laboratory setup. Particle image velocimetry measurements reveal the counter-rotating torus vortices in the lower and upper domains and the complex mixing-layer features in the transitional domain between them. In particular, it is found that the vortex structures are significantly intensified by the thermal convection from the heated disk.

  3. Convection and retro-convection enhanced delivery: some theoretical considerations related to drug targeting.

    PubMed

    Motion, J P Michael; Huynh, Grace H; Szoka, Francis C; Siegel, Ronald A

    2011-03-01

    Delivery of drugs and macromolecules into the brain is a challenging problem, due in part to the blood-brain barrier. In this article, we focus on the possibilities and limitations of two infusion techniques devised to bypass the blood-brain barrier: convection enhanced delivery (CED) and retro-convection enhanced delivery (R-CED). CED infuses fluid directly into the interstitial space of brain or tumor, whereas R-CED removes fluid from the interstitial space, which results in the transfer of drugs from the vascular compartment into the brain or tumor. Both techniques have shown promising results for the delivery of drugs into large volumes of tissue. Theoretical approaches of varying complexity have been developed to better understand and predict brain interstitial pressures and drug distribution for these techniques. These theoretical models of flow and diffusion can only be solved explicitly in simple geometries, and spherical symmetry is usually assumed for CED, while axial symmetry has been assumed for R-CED. This perspective summarizes features of these models and provides physical arguments and numerical simulations to support the notion that spherical symmetry is a reasonable approximation for modeling CED and R-CED. We also explore the potential of multi-catheter arrays for delivering and compartmentalizing drugs using CED and R-CED.

  4. Added value of convection-permitting reanalyses

    NASA Astrophysics Data System (ADS)

    Wahl, S.; Keller, J. D.; Ohlwein, C.; Hense, A.; Friederichs, P.; Crewell, S.

    2016-12-01

    Atmospheric reanalyses are a state-of-the-art tool to generate consistent and realistic state estimates of the atmospheric system. They are used for validation of meteorological and hydrological models, climate monitoring, and renewable energy applications, amongst others. Current reanalyses are mainly global, while regional reanalyses are emerging for North America, the polar region, and most recently for Europe. Due to the horizontal resolution used, deep convection is still parameterized even in the regional reanalyses. However, convective parameterization is a major source of errors and uncertainties in atmospheric models. Therefore, it is expected that convection permitting reanalysis systems are able to adequately simulate the mechanisms leading to high-impact weather, notably heavy precipitation and winds related to deep moist convection. A novel convective-scale regional reanalysis system for Central Europe (COSMO-REA2) has been developed by the Hans-Ertel Center for Weather Research - Climate Monitoring Branch. The system is based on the COSMO model and uses a nudging scheme for the assimilation of observational data. In addition, radar-derived rain rates are assimilated through a latent heat nudging scheme. With a horizontal grid-spacing of 2 km, the model parameterization for deep moist convective processes is turned off. As we expect the largest benefit of the convection-permitting system for precipitation, the evaluation focuses on this essential climate variable (ECV). Furthermore, precipitation is crucial for climate monitoring purposes, e.g., in the form of extreme precipitation which is an major cause of severe damages and societal costs in Europe. This study illustrates the added value of the convective-scale reanalysis compared to coarser gridded regional European and global reanalyses.

  5. Convection and Mixing in Classical Novae Precursors

    NASA Astrophysics Data System (ADS)

    Dursi, L. J.; Calder, A. C.; Alexakis, A.; Truran, J. W.; Zingale, M.; Times, F. X.; Ricker, P. M.; Fryxell, B.; Olson, K.; Rosner, R.; MacNeice, P.

    2002-06-01

    To explain observed abundances from classical nova outbursts, and to help explain their energetics, nova models must incorporate a mechanism that will dredge up the heavier white dwarf material into the lighter accreted atmosphere. One proposed mechanism relies on the fluid motions from an early convective phase to do the mixing. We present recent work investigating two aspects of this mechanism. We examine results from two-dimensional simulations of classical nova precursor models that demonstrate the beginning of a convective phase during the `simmering' of a nova precursor. We use a new hydrostatic equilibrium hydrodynamics module recently developed for the adaptive-mesh code FLASH. The two-dimensional models are based on the one-dimensional models of Ami Glasner (Glasner et al. 1997), and were evolved with FLASH from a pre-convective state to the onset of convection. The onset of convection induces a velocity field near the C,O/H,He interface, which can then cause mixing through interactions with gravity waves. We show results from simulations of these wind-wave interactions, and estimate whether the `wind' caused by the convection could induce sufficient dredge-up to power a classical novae. This research has been supported by the US. Department of Energy under grant no. B341495 to the ASCI Flash Center at the University of Chicago

  6. Modeling deep convection in the Greenland Sea

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.; Mellor, G. L.; Kantha, L. H.

    1992-01-01

    The development of deep convective events in the high-latitude ocean is studied using a three-dimensional, coupled ice-ocean model. Oceanic mixing is described according to the level 2.5 turbulence closure scheme in which convection occurs in a continuous way, i.e., convective adjustment is not invoked. The model is forced by strong winds and surface cooling. Strong upwelling at the multilyear ice edge and consequent entrainment of warm Atlantic waters into the mixed layer is produced by winds parallel to the ice edge. Concomitant cooling drives deep convection and produces chimneylike structures. Inclusion of a barotropic mean flow over topography to the model provides important preconditioning and selects the location of deep convection. The most efficient preconditioning occurs at locations where the flow ascends a slope. In a stratified environment similar to the Greenland Sea with a 12 m/s wind the model simulations show that localized deep convection takes place after about 10 days to depths of 1000 m.

  7. Plasmodia express two threonine-peptidase complexes during asexual development.

    PubMed

    Mordmüller, Benjamin; Fendel, Rolf; Kreidenweiss, Andrea; Gille, Christoph; Hurwitz, Robert; Metzger, Wolfram G; Kun, Jürgen F J; Lamkemeyer, Tobias; Nordheim, Alfred; Kremsner, Peter G

    2006-07-01

    Threonine-peptidases of the T1-family are multi-subunit complexes with broad substrate specificity. In eukaryotes, at least 14 genes encode subunits of the prototypic T1 threonine-peptidase, the proteasome. The proteasome determines the turnover of most proteins and thereby plays a fundamental role in diverse processes such as protein quality control, signal transduction, and cell cycle regulation. While eukaryotes and archaea possess a proteasome, bacteria generally express a second member of the T1-family, the proteasomal predecessor ClpQ/hslV that has a similar structure but is encoded by only one gene. The plasmodial genome is an exception because it encodes proteasomal subunits as well as a ClpQ/hslV-orthologe (Plasmodium falciparum-hslV; PfhslV). Structure, expression, and function of both types of peptidase-complex in P. falciparum are presently unknown. Our aim was to analyze both the coding sequences and derived proteins of both peptidase-complexes because highly specific and potent inhibitors can be designed against this class of enzymes. The proteasome was found expressed throughout the cell cycle, whereas PfhslV was detectable in schizonts and merozoites only. Treatment of P. falciparum with the threonine-peptidase inhibitor epoxomicin blocked two of three catalytically active proteasome subunits. This led to the accumulation of ubiquitinated proteins and, finally, to parasite death. In conclusion, we provide the first functional analysis of plasmodial threonine-peptidase-complexes and identify a lead compound for the development of a novel class of antimalarial drugs.

  8. Supergranulation, a convective phenomenon

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2015-08-01

    Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection ,Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2004, MNRAS, 347, 1279-12814) Paniveni , U., Krishan, V., Singh, J

  9. Anomalously weak solar convection.

    PubMed

    Hanasoge, Shravan M; Duvall, Thomas L; Sreenivasan, Katepalli R

    2012-07-24

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical-harmonic degree ℓ. Within the wavenumber band ℓ < 60, convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers ℓ < 60, with Rossby numbers smaller than approximately 10(-2) at r/R([symbol: see text]) = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  10. Anomalously Weak Solar Convection

    NASA Technical Reports Server (NTRS)

    Hanasoge, Shravan M.; Duvall, Thomas L.; Sreenivasan, Katepalli R.

    2012-01-01

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical- harmonic degree l..Within the wavenumber band l < 60, convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers l < 60, with Rossby numbers smaller than approximately 10(exp -2) at r/R-solar = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  11. Phenomenology of turbulent convection

    NASA Astrophysics Data System (ADS)

    Verma, Mahendra; Chatterjee, Anando; Kumar, Abhishek; Samtaney, Ravi

    2016-11-01

    We simulate Rayleigh-Bénard convection (RBC) in which a fluid is confined between two thermally conducting plates. We report results from direct numerical simulation (DNS) of RBC turbulence on 40963 grid, the highest resolution hitherto reported, on 65536 cores of Cray XC40, Shaheen II, at KAUST. The non-dimensional parameters of our simulation are: the Rayleigh number Ra = 1 . 1 ×1011 (the highest ever for a pseudo-spectral simulation) and Prandtl number of unity. We present energy flux diagnostics of shell-to-shell (in wave number space) transfer. Furthermore, noting that convective flows are anisotropic due to buoyancy, we quantify anisotropy by subdividing each wavenumber shell into rings and quantify ring energy spectrum. An outstanding question in convective turbulence is the wavenumber scaling of the energy spectrum. Our pseudo-spectral simulations of turbulent thermal convection coupled with novel energy transfer diagnostics have provided a definitive answer to this question. We conclude that convective turbulence exhibits behavior similar to fluid turbulence, that is, Kolmogorov's k - 5 / 3 spectrum with forward and local energy transfers, along with a nearly isotropic energy distribution. The supercomputer Shaheen at KAUST was utilized for the simulations.

  12. Observing convective aggregation

    NASA Astrophysics Data System (ADS)

    Holloway, Christopher; Wing, Allison; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan; Turner, David; Zuidema, Paquita

    2017-04-01

    Convective self-aggregation 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 a 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.

  13. Convection in White Dwarfs

    NASA Astrophysics Data System (ADS)

    Provencal, Judith L.; Shipman, H.; Dalessio, J.; M, M.

    2012-01-01

    Convection is one of the largest sources of theoretical uncertainty in our understanding of stellar physics. Current studies of convective energy transport are based on the mixing length theory. Originally intended to depict turbulent flows in engineering situations, MLT enjoys moderate success in describing stellar convection. However, problems arising from MLT's incompleteness are apparent in studies ranging from determinations of the ages of massive stars, to understanding the structure F and early A stars, to predicting the pulsation periods of solar stars, to understanding the atmosphere of Titan. As an example for white dwarfs, Bergeron et al. (1995) show that model parameters such as flux, line profiles, energy distribution, color indices, and equivalent widths are extremely sensitive to the assumed MLT parameterization. The authors find systematic uncertainties ranging from 25% for effective temperatures to 11% for mass and radius. The WET is engaged in a long term project to empirically determine the physical properties of convection in the atmospheres of pulsating white dwarfs. The technique, outlined by Montgomery et al. (2010), uses information from nonlinear (non-sinusoidal) pulse shapes of the target star to empirically probe the physical properties of its convection zone. Approximately two thirds of all white dwarfs show nonlinear characteristics in their light curves. We present current results from WET targets in 2008-2011.

  14. Convection in containerless processing.

    PubMed

    Hyers, Robert W; Matson, Douglas M; Kelton, Kenneth F; Rogers, Jan R

    2004-11-01

    Different containerless processing techniques have different strengths and weaknesses. Applying more than one technique allows various parts of a problem to be solved separately. For two research projects, one on phase selection in steels and the other on nucleation and growth of quasicrystals, a combination of experiments using electrostatic levitation (ESL) and electromagnetic levitation (EML) is appropriate. In both experiments, convection is an important variable. The convective conditions achievable with each method are compared for two very different materials: a low-viscosity, high-temperature stainless steel, and a high-viscosity, low-temperature quasicrystal-forming alloy. It is clear that the techniques are complementary when convection is a parameter to be explored in the experiments. For a number of reasons, including the sample size, temperature, and reactivity, direct measurement of the convective velocity is not feasible. Therefore, we must rely on computation techniques to estimate convection in these experiments. These models are an essential part of almost any microgravity investigation. The methods employed and results obtained for the projects levitation observation of dendrite evolution in steel ternary alloy rapid solidification (LODESTARS) and quasicrystalline undercooled alloys for space investigation (QUASI) are explained.

  15. Dissecting a complex neurosurgical illustration: step-by-step development.

    PubMed

    Suk, Ian

    2011-12-01

    Modern computer graphics software has enabled the medical illustrator to render very complex anatomy by composing many different layers of drawings simultaneously. This and the author's capacity to take an "editorial" approach to compress several chronological events into a single, comprehensive two-dimensional illustration are analyzed in a step-by-step process. Through a series of images, the article provides a visual synopsis of the development of an illustration for an extensive clinical case: total sacrectomy performed through an all-posterior approach. Originally given as a slide presentation at the American Association of Neurological Surgeons Theodore Kurze Lecture in April 2011, the article provides some detailed notes on the techniques the author used to develop a comprehensive neurosurgical illustration.

  16. Prospects of the complex development of highly parameter geothermal brines

    NASA Astrophysics Data System (ADS)

    Alkhasov, A. B.; Alkhasova, D. A.; Ramazanov, A. Sh.; Kasparova, M. A.

    2015-06-01

    The high efficiency of complex processing of high-temperature hydrothermal brines with utilization of heat energy in a binary geothermal power plant and subsequent extraction of solved chemical compounds is shown. Promising technological schemes are given, where electric power, which is generated in the binary geothermal power plant, is used in a block to recover chemistry components. The technology for integrated processing of geothermal brines of the chloride-sodium-calcium type is developed, which provides the manufacture not only of marketable products but also of practically overall reagents of processed water that are necessary to realize the technology. Priority areas for development are indicated, and the preliminary estimates for a Berikey geothermal deposit are given. It is shown that only established resources of thermal brines of the Berikey deposit make it possible to produce more than 2000 t of lithium carbonate and, thereby, to completely provide Russian industry requirements for it.

  17. Electrical imaging and fluid modeling of convective fingering in a shallow water-table aquifer

    NASA Astrophysics Data System (ADS)

    Dam, Remke L.; Eustice, Brian P.; Hyndman, David W.; Wood, Warren W.; Simmons, Craig T.

    2014-02-01

    Unstable density-driven flow can lead to enhanced solute transport in groundwater. Only recently has the complex fingering pattern associated with free convection been documented in field settings. Electrical resistivity (ER) tomography has been used to capture a snapshot of convective instabilities at a single point in time, but a thorough transient analysis is still lacking in the literature. We present the results of a 2 year experimental study at a shallow aquifer in the United Arab Emirates that was designed to specifically explore the transient nature of free convection. ER tomography data documented the presence of convective fingers following a significant rainfall event. We demonstrate that the complex fingering pattern had completely disappeared a year after the rainfall event. The observation is supported by an analysis of the aquifer halite budget and hydrodynamic modeling of the transient character of the fingering instabilities. Modeling results show that the transient dynamics of the gravitational instabilities (their initial development, infiltration into the underlying lower-density groundwater, and subsequent decay) are in agreement with the timing observed in the time-lapse ER measurements. All experimental observations and modeling results are consistent with the hypothesis that a dense brine that infiltrated into the aquifer from a surficial source was the cause of free convection at this site, and that the finite nature of the dense brine source and dispersive mixing led to the decay of instabilities with time. This study highlights the importance of the transience of free convection phenomena and suggests that these processes are more rapid than was previously understood.

  18. Development of the nuclear weapons complex EP architecture

    SciTech Connect

    Murray, C.; Halbleib, L.

    1996-07-01

    The Nuclear Weapons Guidance Team is an interagency committee led by Earl Whiteman, DOE that chartered the generation of EP40100, Concurrent Qualification and its successor EP401099, Concurrent Engineering and Qualification. As this new philosophy of concurrent operations has evolved and as implementation has been initiated, conflicts and insufficiencies in the remaining Engineering Procedures (EPs) have become more apparent. At the Guidance Team meeting in November 1995, this issue was explored and several approaches were considered. It was concluded at this meeting, that a smaller set of interagency EPs described in a hierarchical system could provide the necessary interagency direction to support complex-wide implementation. This set consolidates many existing EP processes where consistency and commonality are critical to success of the extended enterprise. The Guidance Team subsequently chartered an interagency team to initiate development activity associated with the envisioned new EP set. This team had participation from seven Nuclear Weapons Complex (NWC) sites as well as DOE/AL and DP-14 (team members are acknowledged later in this report). Per the Guidance Team, this team, referred to as the Architecture Subcommittee, was to map out and define an EP Architecture for the interagency EPs, make recommendations regarding a more agile process for EP approval and suggest an aggressive timeline to develop the combined EPs. The Architecture Subcommittee was asked to brief their output at the February Guidance Team meeting. This SAND report documents the results of the Architecture Subcommittee`s recommendations.

  19. A framework for implementing systems engineering development of complex systems

    NASA Astrophysics Data System (ADS)

    Brunson, Karl Leonard

    The Department of Defense and the aerospace industry are responsible for decades of successful implementation of systems engineering process models used for the development of complex systems. The process models implemented throughout acquisition life cycles have proven to be comprehensive and flexible, and hence are designed to reduce acquisition schedule variability and the inherent risks of life-cycle cost overruns. While implementing the appropriate process model is important, various process models do not evaluate and quantify potential technical, manufacturing, scheduling and cost risks that may impact acquisition activities throughout the acquisition life cycle of the complex system. A potential way to effectively manage these risks with the appropriate process model is through the incorporation of the Synthesized Framework , the proposed method developed in this dissertation. With the described Synthesized Framework (SF), process models and risk drivers can be analyzed using this comprehensive approach, which implements qualitative and quantitative risk analysis techniques through Monte Carlo simulation. The result is a repeatable, inherent, risk-driven commitment process that can stabilize and synchronize both systems engineering and acquisition processes.

  20. Natural convection: Fundamentals and applications

    NASA Astrophysics Data System (ADS)

    Kakac, S.; Aung, W.; Viskanta, R.

    Among the topics discussed are: stability solutions for laminar external boundary region flows; natural convection in plane layers and cavities with volumetric energy sources; and turbulence modelling equations. Consideration is also given to: natural convection in enclosures containing tube bundles; natural limiting behaviors in porous media cavity flows; numerical solutions in laminar and turbulent natural convection; and heat transfer in the critical region of binary mixtures. Additional topics discussed include: natural convective cooling of electronic equipment; natural convection suppression in solar collectors; and laser induced buoyancy and forced convection in vertical tubes.

  1. [Development, health-industrial complex and industrial policy].

    PubMed

    Gadelha, Carlos Augusto Grabois

    2006-08-01

    This paper puts health questions within the context of national development and industrial policy. It follows the idea of structuralist, Marxist and Schumpeterian approaches, in which industry and innovations form determining factors for the dynamism in capitalist economies and relative positions within the world economy. All countries that have developed and started to compete under better conditions with advanced countries have had an association between strong industry and an endogenous knowledge, learning and innovation base. However, in the field of health, this vision presents problems because business interests move according to the economic logic of profit rather than to meet health needs. The notion of the health-industrial complex is an attempt to provide a theoretical reference that enables linkage between two distinct types of logic: health and economic development. This study has sought to show, on the basis of foreign trade data, how disregard for the logic of health policy development has led to a situation of economic vulnerability in this sector, which may limit the objectives of universality, equality and comprehensiveness. Within this context, a cognitive and political break with these antagonistic visions that put health needs on one side and industrial needs on the other is proposed. A country that aims to reach a condition of development and independence requires strong innovative industries and an inclusive and universal health system, at the same time.

  2. Developing a theoretical framework for complex community-based interventions.

    PubMed

    Angeles, Ricardo N; Dolovich, Lisa; Kaczorowski, Janusz; Thabane, Lehana

    2014-01-01

    Applying existing theories to research, in the form of a theoretical framework, is necessary to advance knowledge from what is already known toward the next steps to be taken. This article proposes a guide on how to develop a theoretical framework for complex community-based interventions using the Cardiovascular Health Awareness Program as an example. Developing a theoretical framework starts with identifying the intervention's essential elements. Subsequent steps include the following: (a) identifying and defining the different variables (independent, dependent, mediating/intervening, moderating, and control); (b) postulating mechanisms how the independent variables will lead to the dependent variables; (c) identifying existing theoretical models supporting the theoretical framework under development; (d) scripting the theoretical framework into a figure or sets of statements as a series of hypotheses, if/then logic statements, or a visual model; (e) content and face validation of the theoretical framework; and (f) revising the theoretical framework. In our example, we combined the "diffusion of innovation theory" and the "health belief model" to develop our framework. Using the Cardiovascular Health Awareness Program as the model, we demonstrated a stepwise process of developing a theoretical framework. The challenges encountered are described, and an overview of the strategies employed to overcome these challenges is presented.

  3. Resurfacing of Uranus' Moon Miranda by Convection: Understanding the Influence of Core Size on Convection Geometry

    NASA Astrophysics Data System (ADS)

    Hammond, N. P.; Barr, A. C.

    2014-12-01

    Miranda is a small icy moon of Uranus. Three remarkable regions of intense deformation, called coronae, are visible in southern hemisphere of Miranda. Coronae are ~200 km wide, and are surrounded by concentric, sub-parrallel lineations, that have been interpreted as extensional tectonic and volcanic landforms. Here we test the hypothesis coronae formed as a result of convection in Miranda's ice mantle during an episode of tidal heating. Using numerical models of spherical convection, we show that if Miranda's surface is weak, sluggish lid convection can occur, which simultaneously generates the concentric deformation patterns observed in the coronae, the inferred thermal gradient predicted by models of flexure, and the approximate number of plumes necessary to form the coronae. We have tested the influence of core size on convection geometry. For basal Rayleigh numbers between 10^5 and 10^8, and for effective viscosity contrasts less than 10^4, we found that low-order convection patterns only remain stable for core radii less than half the satellite radius. This suggests that low-order convection patterns may be more likely to develop in planets and satellites with small cores, however we find that the distribution of tidal heating within icy satellites also strongly influences convection geometry.

  4. Geothermal reservoirs in hydrothermal convection systems

    SciTech Connect

    Sorey, M.L.

    1982-01-01

    Geothermal reservoirs commonly exist in hydrothermal convection systems involving fluid circulation downward in areas of recharge and upwards in areas of discharge. Because such reservoirs are not isolated from their surroundings, the nature of thermal and hydrologic connections with the rest of the system may have significant effects on the natural state of the reservoir and on its response to development. Conditions observed at numerous developed and undeveloped geothermal fields are discussed with respect to a basic model of the discharge portion of an active hydrothermal convection system. Effects of reservoir development on surficial discharge of thermal fluid are also delineated.

  5. Magnetospheric convection at Uranus

    NASA Technical Reports Server (NTRS)

    Selesnick, R. S.

    1987-01-01

    The unusual configuration of the Uranian magnetosphere leads to differences in the relative effects of solar wind induced magnetospheric convection and plasma corotation from those at the other planets. At the present epoch the orientation of the rotation axis of Uranus with respect to the solar wind flow direction leads to a decoupling of the convective and corotational flows, allowing plasma from the tail to move unimpeded through the inner magnetosphere. As Uranus progresses in its orbit around the sun, corotation plays a gradually more important role and the plasma residence times within the magnetosphere increase. When the rotation axis finally becomes perpendicular to the solar wind flow, corotation is dominant.

  6. Development and Infectious Disease in Hosts with Complex Life Cycles

    PubMed Central

    Searle, Catherine L.; Xie, Gisselle Yang; Blaustein, Andrew R.

    2013-01-01

    Metamorphosis is often characterized by profound changes in morphology and physiology that can affect the dynamics of species interactions. For example, the interaction between a pathogen and its host may differ depending on the life stage of the host or pathogen. One pathogen that infects hosts with complex life cycles is the emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis (Bd). We sought to determine how conditions at the larval stage can affect variation in development and patterns of Bd infection across amphibian life stages. We used outdoor experimental mesocosms to simulate natural pond habitats and manipulated the presence of Bd, the larval density, and the number of host species in larvae of two co-occurring amphibian species (Rana cascadae and Pseudacris regilla). We found that infection differed between species throughout development; P. regilla consistently had higher infection severity compared to R. cascadae. Additionally, while up to 100% of larvae were infected, only 18.2% of R. cascadae and 81.5% of P. regilla were infected after metamorphosis. This indicates that amphibians have the ability to recover from Bd infection as they undergo metamorphosis. Higher larval densities in P. regilla led to a shorter larval period, and individuals with a shorter larval period had lower infection severity. This led to a trend where P. regilla larvae reared at high densities tended to have lower infection prevalence after metamorphosis. We also found that exposure to Bd increased larval mortality and prolonged the larval period in P. regilla, indicating that P. regilla are susceptible to the negative effects of Bd as larvae. This study demonstrates that host density, species composition, and pathogen exposure may all interact to influence development and infection in hosts with complex life cycles. PMID:23565288

  7. Development and infectious disease in hosts with complex life cycles.

    PubMed

    Searle, Catherine L; Xie, Gisselle Yang; Blaustein, Andrew R

    2013-01-01

    Metamorphosis is often characterized by profound changes in morphology and physiology that can affect the dynamics of species interactions. For example, the interaction between a pathogen and its host may differ depending on the life stage of the host or pathogen. One pathogen that infects hosts with complex life cycles is the emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis (Bd). We sought to determine how conditions at the larval stage can affect variation in development and patterns of Bd infection across amphibian life stages. We used outdoor experimental mesocosms to simulate natural pond habitats and manipulated the presence of Bd, the larval density, and the number of host species in larvae of two co-occurring amphibian species (Rana cascadae and Pseudacris regilla). We found that infection differed between species throughout development; P. regilla consistently had higher infection severity compared to R. cascadae. Additionally, while up to 100% of larvae were infected, only 18.2% of R. cascadae and 81.5% of P. regilla were infected after metamorphosis. This indicates that amphibians have the ability to recover from Bd infection as they undergo metamorphosis. Higher larval densities in P. regilla led to a shorter larval period, and individuals with a shorter larval period had lower infection severity. This led to a trend where P. regilla larvae reared at high densities tended to have lower infection prevalence after metamorphosis. We also found that exposure to Bd increased larval mortality and prolonged the larval period in P. regilla, indicating that P. regilla are susceptible to the negative effects of Bd as larvae. This study demonstrates that host density, species composition, and pathogen exposure may all interact to influence development and infection in hosts with complex life cycles.

  8. Arabidopsis flower development--of protein complexes, targets, and transport.

    PubMed

    Becker, Annette; Ehlers, Katrin

    2016-03-01

    Tremendous progress has been achieved over the past 25 years or more of research on the molecular mechanisms of floral organ identity, patterning, and development. While collections of floral homeotic mutants of Antirrhinum majus laid the foundation already at the beginning of the previous century, it was the genetic analysis of these mutants in A. majus and Arabidopsis thaliana that led to the development of the ABC model of floral organ identity more than 20 years ago. This intuitive model kick-started research focused on the genetic mechanisms regulating flower development, using mainly A. thaliana as a model plant. In recent years, interactions among floral homeotic proteins have been elucidated, and their direct and indirect target genes are known to a large extent. Here, we provide an overview over the advances in understanding the molecular mechanism orchestrating A. thaliana flower development. We focus on floral homeotic protein complexes, their target genes, evidence for their transport in floral primordia, and how these new results advance our view on the processes downstream of floral organ identity, such as organ boundary formation or floral organ patterning.

  9. Health informatics to optimize complex laboratory developed test configurations.

    PubMed

    Afzal, Uzma; Mahmood, Tariq; Anwar, Masood; Shaikh, Zubair

    2016-11-14

    Configuration of complex Laboratory Developed Tests (LDTs) is a time-consuming and complicated task, potentially leading to inconsistent LDTs in which features constraints remain unresolved and important features could remain unselected. Our objective is to address these issues by presenting an automated, health informatics solution which autonomously optimizes feature selection in complex LDTs through Particle Swarm Optimization (PSO). The optimization goal is to minimize inconsistencies and configuration time, and maximize the number of selected features. We implemented our technology in a local, secondary-care hospital in Pakistan which configures LDT for a local epidemic disease. First, a list of inconsistent LDT configurations is generated. This is used to initially estimate optimal PSO parameters, which are then used for optimization process. Results show that PSO is able to minimize 91% inconsistencies between 9 and 11 seconds. The number of selected critical features also increases by 100% in the optimized LDT configuration. We present a novel and the first application of computational optimization to solve LDT configuration issues.

  10. The different influence of the residual layer on the development of the summer convective boundary layer in two deserts in northwest China

    NASA Astrophysics Data System (ADS)

    Lin, Zhao; Bo, Han; Shihua, Lv; Lijuan, Wen; Xianhong, Meng; Zhaoguo, Li

    2016-12-01

    The development of the atmospheric boundary layer is closely connected with the exchange of momentum, heat, and mass near the Earth's surface, especially for a convective boundary layer (CBL). Besides being modulated by the buoyancy flux near the Earth's surface, some studies point out that a neutrally stratified residual layer is also crucial for the appearance of a deep CBL. To verify the importance of the residual layer, the CBLs over two deserts in northwest China (Badan Jaran and Taklimakan) were investigated. The summer CBL mean depth over the Taklimakan Desert is shallower than that over the Badan Jaran Desert, even when the sensible heat flux of the former is stronger. Meanwhile, the climatological mean residual layer in the Badan Jaran Desert is much deeper and neutrally stratified in summer. Moreover, we found a significant and negative correlation between the lapse rate of the residual layer and the CBL depth over the Badan Jaran Desert. The different lapse rates of the residual layer in the two regions are partly connected with the advection heating from large-scale atmospheric circulation. The advection heating tends to reduce the temperature difference in the 700 to 500-hPa layer over the Badan Jaran Desert, and it increases the stability in the same atmospheric layer over the Taklimakan Desert. The advection due to climatological mean atmospheric circulation is more effective at modulating the lapse rate of the residual layer than from varied circulation. Also, the interannual variation of planetary boundary layer (PBL) height over two deserts was found to covary with the wave train.

  11. Reelin and its complex involvement in brain development and function.

    PubMed

    Lakatosova, Silvia; Ostatnikova, Daniela

    2012-09-01

    Reelin is a neuroprotein with crucial role during neurodevelopment and also in postnatal period. It regulates neuronal migration and positioning in developing neocortex and cerebellar cortex. Postnatally it participates in regulation of dendritic and axonal growth, synaptogenesis, neurotransmission and it contribute to synaptic plasticity necessary for learning and memory functions. Role of Reelin seems to be rather complex, profound research gradually uncovers its further functions. Deficits of Reelin were detected in neuropsychiatric disorders such as schizophrenia, bipolar disorder and autism. Pathogenesis of these disorders is far from being clearly understood. Reelin contribution to these diseases seems to be vital, since genetic variants of Reelin were associated with these diseases and often influence symptom severity. Reelin is a promising candidate molecule with potential future use in diagnostics and therapy, however further detailed research is essential. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Developing microRNA therapeutics: approaching the unique complexities.

    PubMed

    Jackson, Aimee L; Levin, Arthur A

    2012-08-01

    MicroRNAs are endogenous small non-coding RNAs that regulate gene expression by interfering with translation or stability of target transcripts. The importance of microRNAs for maintaining biological functions is illustrated by the fact that microRNAs are exploited in nature to regulate phenotypes, and by the diverse disease phenotypes that result when microRNAs are mutated or improperly expressed. Disease-associated microRNAs might therefore represent a new class of therapeutic targets. With the recent demonstration that inhibition of miR-122 reduces viral load in hepatitis C patients, microRNA modulators are no longer merely theoretical, but rather, have become strong candidate therapeutics. The complexity of microRNA biology offers a novel mechanism of action for therapeutic intervention but also poses unique challenges for the development of therapeutic modulators as drugs.

  13. Curcumin complexation with cyclodextrins by the autoclave process: Method development and characterization of complex formation.

    PubMed

    Hagbani, Turki Al; Nazzal, Sami

    2017-03-30

    One approach to enhance curcumin (CUR) aqueous solubility is to use cyclodextrins (CDs) to form inclusion complexes where CUR is encapsulated as a guest molecule within the internal cavity of the water-soluble CD. Several methods have been reported for the complexation of CUR with CDs. Limited information, however, is available on the use of the autoclave process (AU) in complex formation. The aims of this work were therefore to (1) investigate and evaluate the AU cycle as a complex formation method to enhance CUR solubility; (2) compare the efficacy of the AU process with the freeze-drying (FD) and evaporation (EV) processes in complex formation; and (3) confirm CUR stability by characterizing CUR:CD complexes by NMR, Raman spectroscopy, DSC, and XRD. Significant differences were found in the saturation solubility of CUR from its complexes with CD when prepared by the three complexation methods. The AU yielded a complex with expected chemical and physical fingerprints for a CUR:CD inclusion complex that maintained the chemical integrity and stability of CUR and provided the highest solubility of CUR in water. Physical and chemical characterizations of the AU complexes confirmed the encapsulated of CUR inside the CD cavity and the transformation of the crystalline CUR:CD inclusion complex to an amorphous form. It was concluded that the autoclave process with its short processing time could be used as an alternate and efficient methods for drug:CD complexation. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. The complexity of childhood development: variability in perspective.

    PubMed

    Vereijken, Beatrix

    2010-12-01

    The complexity of childhood development is exemplified in the variability of development that is seen across tasks and individuals. Furthermore, variability in performance is omnipresent within individuals across repetitions of a task and across individuals performing the same task. Previously, this variability was thought to reflect error of measurement or error of execution. On this account, variability reflects noise that should be filtered or averaged out of the data in order to reveal the "true" underlying characteristics of the performance. Although errors of measurement and execution indeed contribute to variability in movements, research in the last 2 decades has revealed characteristics of variability that are far more interesting than just noise. These characteristics can be deeply informative about underlying control processes and point to directions for clinical practice. This perspective article reviews different ways of characterizing variability, illustrates changes in variability as a result of development and learning, and discusses different theoretical perspectives on the role of variability that give clues about how to understand changes in variability and how to deal with variability in clinical settings.

  15. Combined buoyancy-thermocapillary convection

    NASA Technical Reports Server (NTRS)

    Homsy, G. M.

    1990-01-01

    Combined buoyancy-thermocapillary convection was studied in 2D and 3D. Fluid motion caused by thermally induced tension gradients on the free surface of a fluid is termed thermocapillary convection. It is well-known that in containerless processing of materials in space, thermocapillary convection is a dominant mechanism of fluid flow. Welding and crystal growth processes are terrestrial applications where thermocapillary convection has direct relevance.

  16. Convection dominated problems

    NASA Technical Reports Server (NTRS)

    Peraire, J.; Morgan, K.; Zienkiewicz, O. C.

    1986-01-01

    The paper surveys the last ten years of activity of the INME Swansea, dealing with problems of convection dominated flow. The basic explicit/implicit characteristic Galerkin process and its application to adaptive mesh refinement used in the solution of realistic problems is focused on.

  17. Improving Convection and Cloud Parameterization Using ARM Observations and NCAR Community Atmosphere Model CAM5

    SciTech Connect

    Zhang, Guang J.

    2016-11-07

    The fundamental scientific objectives of our research are to use ARM observations and the NCAR CAM5 to understand the large-scale control on convection, and to develop improved convection and cloud parameterizations for use in GCMs.

  18. Anomalously weak solar convection

    PubMed Central

    Hanasoge, Shravan M.; Duvall, Thomas L.

    2012-01-01

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical-harmonic degree ℓ. Within the wavenumber band ℓ < 60, convective velocities are 20–100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers ℓ < 60, with Rossby numbers smaller than approximately 10-2 at r/R⊙ = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient. PMID:22665774

  19. Mixed convection flow of nanofluid in a square enclosure with an intruded rectangular fin

    SciTech Connect

    Cong, Ran; Zhou, Xuanyu; De Souza Machado, Bruno; Das, Prodip K.

    2016-07-12

    Mixed convection flow in enclosures has been a subject of interest for many years due to their ever increasing applications in solar collectors, electronic cooling, lubrication technologies, food processing, and nuclear reactors. In comparison, little effort has been given to the problem of mixed convection in enclosures filled with nanofluids, while the addition of nanoparticles in a fluid base to alter specific material properties is considered a feasible solution for many heat transfer problems. Mixed convection of nanofluids is a challenging problem as the addition of nanoparticles changes the fluid’s thermo-physical properties as well as due to the complex interactions among inertia, viscous, and buoyancy forces. In this study, a two-dimensional steady-state numerical model has been developed to investigate mixed convection flow of nanofluids in a square enclosure with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the Constructal design. The model has been developed using ANSYS-FLUENT for various fin geometries. Flow fields, temperature fields, and heat transfer rates are examined for different values of Rayleigh and Reynolds numbers for several geometries of the fin with the aim of maximizing the heat transfer from the fin to the surrounding flow. Outcome of this study provides important insight into the heat transfer behavior of nanofluids, which will help in developing novel geometries with enhanced and controlled heat transfer for solar collectors and electronic devices.

  20. Mixed convection flow of nanofluid in a square enclosure with an intruded rectangular fin

    NASA Astrophysics Data System (ADS)

    Cong, Ran; Zhou, Xuanyu; De Souza Machado, Bruno; Das, Prodip K.

    2016-07-01

    Mixed convection flow in enclosures has been a subject of interest for many years due to their ever increasing applications in solar collectors, electronic cooling, lubrication technologies, food processing, and nuclear reactors. In comparison, little effort has been given to the problem of mixed convection in enclosures filled with nanofluids, while the addition of nanoparticles in a fluid base to alter specific material properties is considered a feasible solution for many heat transfer problems. Mixed convection of nanofluids is a challenging problem as the addition of nanoparticles changes the fluid's thermo-physical properties as well as due to the complex interactions among inertia, viscous, and buoyancy forces. In this study, a two-dimensional steady-state numerical model has been developed to investigate mixed convection flow of nanofluids in a square enclosure with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the Constructal design. The model has been developed using ANSYS-FLUENT for various fin geometries. Flow fields, temperature fields, and heat transfer rates are examined for different values of Rayleigh and Reynolds numbers for several geometries of the fin with the aim of maximizing the heat transfer from the fin to the surrounding flow. Outcome of this study provides important insight into the heat transfer behavior of nanofluids, which will help in developing novel geometries with enhanced and controlled heat transfer for solar collectors and electronic devices.

  1. Stability Impact on Wake Development in Moderately Complex Terrain

    NASA Astrophysics Data System (ADS)

    Infield, D.; Zorzi, G.

    2017-05-01

    This paper uses a year of SCADA data from Whitelee Wind Farm near Glasgow to investigate wind turbine wake development in moderately complex terrain. Atmospheric stability measurements in terms of Richardson number from a met mast at an adjoining site have been obtained and used to assess the impact of stability on wake development. Considerable filtering of these data has been undertaken to ensure that all turbines are working normally and are well aligned with the wind direction. A group of six wind turbines, more or less in a line, have been selected for analysis, and winds within a 2 degree direction sector about this line are used to ensure, as far as possible, that all the turbines investigated are fully immersed in the wake/s of the upstream turbine/s. Results show how the terrain effects combine with the wake effects, with both being of comparable importance for the site in question. Comparison has been made with results from two commercial CFD codes for neutral stability, and reasonable agreement is demonstrated. Richardson number has been plotted against wind shear and turbulence intensity at a met mast on the wind farm that for the selected wind direction is not in the wake of any turbines. Good correlations are found indicating that the Richardson numbers obtained are reliable. The filtered data used for wake analysis were split according to Richardson number into two groups representing slightly stable to neutral, and unstable conditions. Very little difference in wake development is apparent. A greater difference can be observed when the data are separated simply by turbulence intensity, suggesting that, although turbulence intensity is correlated with stability, of the two it is the parameter that most directly impacts on wake development through mixing of ambient and wake flows.

  2. Heavy rain forecasts in mesoscale convective system in July 2016 in Belarus

    NASA Astrophysics Data System (ADS)

    Lapo, Palina; Barodka, Siarhei; Krasouski, Aliaksandr

    2017-04-01

    During the last decade, the frequency of severe weather phenomena, such as heavy precipitation, hail and squalls, over Europe is observed to increase, which is attributed to climate change in the region. Such hazardous weather events over the territory of Belarus every year, having significant economic and social effects. Of special interest for further studies are mesoscale convective systems, which can be described as long-lived cloud complexes including groups of cumulonimbus clouds and squall lines. Passage of such systems is accompanied with intense thunderstorms, showers and squally wind. In this study, we investigate a case of Mesoscale Convective System (MCS) passage over the territory of Belarus, which occurred 13 July 2016. During this Mesoscale Convective Complex passage, heavy precipitation (up to 43 mm), squally winds and intense thunderstorms have been observed. Another feature of this MCS was the hook-shaped weather radar signature known as a "hook echo", seen on the Doppler weather radar Minsk-2. Tornadoes and powerful mesocyclones are often characterized by the presence of a hook echo on radar. Also we have performed simulations of the convective complex passage with the WRF-ARW mesoscale atmospheric modelling system using 6 different microphysics parameterizations. Our main objectives are to study the conditions of this Mesoscale Convective Systems (MCSs) development, to consider the microphysical structure of clouds in the MCS, and to identify which microphysics package provides the best forecast of precipitation for this case of MCS in terms of its geographical distribution and precipitation amount in towns and cities where highest levels of precipitation have been observed. We present analysis of microphysical structure of this MCS along with evaluation of precipitation forecasts obtained with different microphysics parametrizations as compared to real observational data. In particular, we may note that results of almost all microphysics

  3. Granular convection and its application to asteroidal resurfacing timescale

    NASA Astrophysics Data System (ADS)

    Yamada, Tomoya; Ando, Kosuke; Morota, Tomokatsu; Katsuragi, Hiroaki

    2016-04-01

    A model for the asteroid resurfacing resulting from regolith convection is built to estimate its timescale. The regolith convection by impact-induced global seismic shaking could be a possible reason for regolith migration and resultant segregated terrain which were found on the asteroids Itokawa [1]. Some recent studies [2, 3] experimentally investigated the convective velocity of the vibrated granular bed to discuss the feasibility of regolith convection under the microgravity condition such as small asteroids. These studies found that the granular convective velocity is almost proportional to the gravitational acceleration [2, 3]. Namely, the granular (regolith) convective velocity would be very low under the microgravity condition. Therefore, the timescale of resurfacing by regolith convection would become very long. In order to examine the feasibility of the resurfacing by regolith convection on asteroids, its timescale have to be compared with the surface age or the lifetime of asteroids. In this study, we aim at developing a model of asteroid resurfacing process induced by regolith convection. The model allows us to estimate the resurfacing timescale for various-sized asteroids covered with regolith. In the model, regolith convection is driven by the impact-induced global seismic shaking. The model consists of three phases, (i) Impact phase: An impactor intermittently collides with a target asteroid [4], (ii) Vibration phase: The collision results in a global seismic shaking [5], (iii) Convection phase: The global seismic shaking induces the regolith convection on the asteroid [3]. For the feasibility assessment of the resurfacing process driven by regolith convection, we estimate the regolith-convection-based resurfacing timescale T as a function of the size of a target asteroid Da. According to the estimated result, the resurfacing time scale is 40 Myr for the Itokawa-sized asteroid, and this value is shorter than the mean collisional lifetime of Itokawa

  4. Recent development of glacier complex Adygine and resulting risks

    NASA Astrophysics Data System (ADS)

    Falatkova, Kristyna; Sobr, Miroslav; Engel, Zbynek; Jansky, Bohumir

    2015-04-01

    Recent development of glacier complex Adygine and resulting risks Falátková, K., Šobr, M., Engel, Z., Janský, B. Charles University in Prague, Faculty of Science, Prague, Czech republic Glacier complex Adygine (3,400-4,200 m asl) is situated on the northern flank of the Kyrgyz Range, Tien Shan, Kyrgyzstan. The valley downstream is part of National Park Ala Archa, which is popular with tourists, and is heading towards the country's capital - Bishkek. At the study site there is a glacier which is observed since 1960's. The glacier has been monitored by satellite imagery and in last 10 years by on-site geodetic measurement as well. Due to glacier shrinkage several glacial lakes of different genetic types (moraine-dammed, moraine- and rock-dammed, termokarst) have appeared at the site. Nowadays, the lakes are situated on three levels in front of the glacier's terminus and form a cascade, they are also hydrologically connected. The lakes were subjected to detailed bathymetric measurement and some parts of the dams were surveyed by geophysical methods. Especially the newest lakes in proximity of the terminus has been undergoing dynamic changes and may pose a threat in the near future. The risks arising together with changing climatic conditions and retreat of the glacier are associated with mainly three of the lakes. The largest one with area of 3.2 ha is dammed by a rock step overlaid by a moraine. Geophysical research of the dam revealed buried ice and seepage channels in its western part. It is the capacity of these subsurface channels, which are draining the lake throughout the year that represents a weak point in terms of dam stability. The second lake, a termokarst one, is a similar case but drained solely by subsurface channels. Very steep slopes of the lake basin are covered with loose material which could slide down and block the drainage channels. The lake would then fill all the basin (approx. 50,000 m3) very quickly as it is supplied with water from the

  5. Aiding and opposing mechanisms of mixed convection in a shear- and buoyancy-driven cavity

    SciTech Connect

    Aydin, O.

    1999-10-01

    Combined forced and natural (mixed) convection in which neither the forced nor the natural convection effects are dominant and both modes are in a comparable level arise in many natural and technological processes. The present study was conducted to numerically investigate the transport mechanism of laminar combined convection in a shear- and buoyancy-driven cavity. The focus was on the interaction of the forced convection induced by the moving wall with the natural convection induced by the buoyancy. Two orientations of thermal boundary conditions at the cavity walls are considered in order to simulate the aiding and opposing buoyancy mechanisms. Velocity and temperature distributions of the flow are carried out through a stream function-vorticity transformation with a finite difference scheme. Parametric studies of the effect of the mixed convection parameter, GR/RE{sup 2}, on the fluid flow and heat transfer have been performed. Calculations cover Re=100, Pr=0.71 and Gr/Re{sup 2} the range of 0.01--100. Three different regimes are observed with increasing Fr/Re{sup 2}. Forced convection (with negligible natural convection), mixed convection (comparable forced and natural convection) and natural convection (with negligible forced convection). The code developed was carefully tested for the two limiting cases, the pure forced convection and the pure natural convection, for which experimental and numerical data are available.

  6. A stochastic scale-aware parameterization of shallow cumulus convection across the convective gray zone

    NASA Astrophysics Data System (ADS)

    Sakradzija, Mirjana; Seifert, Axel; Dipankar, Anurag

    2016-06-01

    The parameterization of shallow cumuli across a range of model grid resolutions of kilometre-scales faces at least three major difficulties: (1) closure assumptions of conventional parameterization schemes are no longer valid, (2) stochastic fluctuations become substantial and increase with grid resolution, and (3) convective circulations that emerge on the model grids are under-resolved and grid-scale dependent. Here we develop a stochastic parameterization of shallow cumulus clouds to address the first two points, and we study how this stochastic parameterization interacts with the under-resolved convective circulations in a convective case over the ocean. We couple a stochastic model based on a canonical ensemble of shallow cumuli to the Eddy-Diffusivity Mass-Flux parameterization in the icosahedral nonhydrostatic (ICON) model. The moist-convective area fraction is perturbed by subsampling the distribution of subgrid convective states. These stochastic perturbations represent scale-dependent fluctuations around the quasi-equilibrium state of a shallow cumulus ensemble. The stochastic parameterization reproduces the average and higher order statistics of the shallow cumulus case adequately and converges to the reference statistics with increasing model resolution. The interaction of parameterizations with model dynamics, which is usually not considered when parameterizations are developed, causes a significant influence on convection in the gray zone. The stochastic parameterization interacts strongly with the model dynamics, which changes the regime and energetics of the convective flows compared to the deterministic simulations. As a result of this interaction, the emergence of convective circulations in combination with the stochastic parameterization can even be beneficial on the high-resolution model grids.

  7. Thermocapillary Convection in Liquid Droplets

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The purpose of this video is to understand the effects of surface tension on fluid convection. The fluid system chosen is the liquid sessile droplet to show the importance in single crystal growth, the spray drying and cooling of metal, and the advance droplet radiators of the space stations radiators. A cross sectional representation of a hemispherical liquid droplet under ideal conditions is used to show internal fluid motion. A direct simulation of buoyancy-dominant convection and surface tension-dominant convection is graphically displayed. The clear differences between two mechanisms of fluid transport, thermocapillary convection, and bouncy dominant convection is illustrated.

  8. Mantle convection and the state of the earth's interior

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.; Gurnis, Michael

    1987-01-01

    During 1983 to 1986 emphasis in the study of mantle convection shifted away from fluid mechanical analysis of simple systems with uniform material properties and simple geometries, toward analysis of the effects of more complicated, presumably more realistic models. The important processes related to mantle convection are considered. The developments in seismology are discussed.

  9. Mantle convection and the state of the Earth's interior

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1987-01-01

    During 1983 to 1986 emphasis in the study of mantle convection shifted away from fluid mechanical analysis of simple systems with uniform material properties and simple geometries, toward analysis of the effects of more complicated, presumably more realistic models. The important processes related to mantle convection are considered. The developments in seismology are discussed.

  10. Mantle convection and the state of the earth's interior

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.; Gurnis, Michael

    1987-01-01

    During 1983 to 1986 emphasis in the study of mantle convection shifted away from fluid mechanical analysis of simple systems with uniform material properties and simple geometries, toward analysis of the effects of more complicated, presumably more realistic models. The important processes related to mantle convection are considered. The developments in seismology are discussed.

  11. A 'fast' model of the solar convection zone

    NASA Astrophysics Data System (ADS)

    Belvedere, G.; Paterno, L.; Roxburgh, I. W.

    1980-11-01

    A model of solar convection zone incorporates the mixing-length theory in the method developed by Faulkner (1965) which accurately represents the superadiabatic layers. Interpolation formulas which save computer time, and are sufficiently accurate to limit discrepancies in pressure distribution and density through the convection zone, are used; the computer programs are 20 times faster than the programs of Baker and Temesvary (1966).

  12. Convection Heat Transfer in Three-Dimensional Turbulent Separated/Reattached Flow

    SciTech Connect

    Bassem F. Armaly

    2007-10-31

    The measurements and the simulation of convective heat transfer in separated flow have been a challenge to researchers for many years. Measurements have been limited to two-dimensional flow and simulations failed to predict accurately turbulent heat transfer in the separated and reattached flow region (prediction are higher than measurements by more than 50%). A coordinated experimental and numerical effort has been initiated under this grant for examining the momentum and thermal transport in three-dimensional separated and reattached flow in an effort to provide new measurements that can be used for benchmarking and for improving the simulation capabilities of 3-D convection in separated/reattached flow regime. High-resolution and non-invasive measurements techniques are developed and employed in this study to quantify the magnitude and the behavior of the three velocity components and the resulting convective heat transfer. In addition, simulation capabilities are developed and employed for improving the simulation of 3-D convective separated/reattached flow. Such basic measurements and simulation capabilities are needed for improving the design and performance evaluation of complex (3-D) heat exchanging equipment. Three-dimensional (3-D) convective air flow adjacent to backward-facing step in rectangular channel is selected for the experimental component of this study. This geometry is simple but it exhibits all the complexities that appear in any other separated/reattached flow, thus making the results generated in this study applicable to any other separated and reattached flow. Boundary conditions, inflow, outflow, and wall thermal treatment in this geometry can be well measured and controlled. The geometry can be constructed with optical access for non-intrusive measurements of the flow and thermal fields. A three-component laser Doppler velocimeter (LDV) is employed to measure simultaneously the three-velocity components and their turbulent fluctuations

  13. Heterogeneous nanofluids: natural convection heat transfer enhancement

    PubMed Central

    2011-01-01

    Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755

  14. Stochastic models for convective momentum transport.

    PubMed

    Majda, Andrew J; Stechmann, Samuel N

    2008-11-18

    The improved parameterization of unresolved features of tropical convection is a central challenge in current computer models for long-range ensemble forecasting of weather and short-term climate change. Observations, theory, and detailed smaller-scale numerical simulations suggest that convective momentum transport (CMT) from the unresolved scales to the resolved scales is one of the major deficiencies in contemporary computer models. Here, a combination of mathematical and physical reasoning is utilized to build simple stochastic models that capture the significant intermittent upscale transports of CMT on the large scales due to organized unresolved convection from squall lines. Properties of the stochastic model for CMT are developed below in a test column model environment for the large-scale variables. The effects of CMT from the stochastic model on a large-scale convectively coupled wave in an idealized setting are presented below as a nontrivial test problem. Here, the upscale transports from stochastic effects are significant and even generate a large-scale mean flow which can interact with the convectively coupled wave.

  15. Diagnosing convective instability using VAS data

    NASA Technical Reports Server (NTRS)

    Petersen, R. A.; Uccellini, L. W.; Chesters, D.; Mostek, A.; Keyser, D.

    1983-01-01

    The utility of combining visible and various infrared images from the VAS to produce a forecasting tool, that can be available on a near real time basis, to predict severe weather development is shown. Areas where dry air in the midtroposphere overlays substantial moisture at low levels are used to diagnose mesoscale regions that have the potential for being convectively unstable before the onset of severe convection. Specifically, 6.7 micron water vapor imagery, used for isolating regions of substantial midlevel dryness, are combined with images of low level clouds or with split-window low level moisture images to delineate regions that have the potential for convective instability. In areas where scattered low level clouds are present, computer generated, color image combinations are used to isolate those warm, low level clouds that are in potential convectively unstable environments from clouds that exist under a deeply moist atmosphere. In clear regions, the split window technique is used for delineating areas of substantial boundary layer moisture. These images are again computer overlayed by the midlevel dryness to produce a color coded image of potential convective instability.

  16. Nonlinear anelastic modal theory for solar convection

    NASA Technical Reports Server (NTRS)

    Latour, J.; Toomre, J.; Zahn, J.-P.

    1983-01-01

    Solar envelope models are developed using single-mode anelastic equations as a description of turbulent convection which provide estimates for the variation with depth of the largest convective cellular flows, with horizontal sizes comparable to the total depth of the convection zone. These models can be used to describe compressible motions occurring over many density scale heights. Single-mode anelastic solutions are obtained for a solar envelope whose mean stratification is nearly adiabatic over most of its vertical extent because of the enthalpy flux explicitly carried by the big cell, while a subgrid scale representation of turbulent heat transport is incorporated into the treatment near the surface. It is shown that the single-mode equations allow two solutions for the same horizontal wavelength which are distinguished by the sense of the vertical velocity at the center of the three-dimensional cell. It is found that the upward directed flow experiences large pressure effects which can modify the density fluctuations so that the sense of the buoyancy force is changed, with buoyancy braking actually achieved near the top of the convection zone. It is suggested that such dynamical processes may explain why the amplitudes of flows related to the largest scales of convection are so weak in the solar atmosphere.

  17. A microphysical pathway analysis to investigate aerosol effects on convective clouds

    NASA Astrophysics Data System (ADS)

    Heikenfeld, Max; White, Bethan; Labbouz, Laurent; Stier, Philip

    2017-04-01

    The impact of aerosols on ice- and mixed-phase processes in convective clouds remains highly uncertain, which has strong implications for estimates of the role of aerosol-cloud interactions in the climate system. The wide range of interacting microphysical processes are still poorly understood and generally not resolved in global climate models. To understand and visualise these processes and to conduct a detailed pathway analysis, we have added diagnostic output of all individual process rates for number and mass mixing ratios to two commonly-used cloud microphysics schemes (Thompson and Morrison) in WRF. This allows us to investigate the response of individual processes to changes in aerosol conditions and the propagation of perturbations throughout the development of convective clouds. Aerosol effects on cloud microphysics could strongly depend on the representation of these interactions in the model. We use different model complexities with regard to aerosol-cloud interactions ranging from simulations with different levels of fixed cloud droplet number concentration (CDNC) as a proxy for aerosol, to prognostic CDNC with fixed modal aerosol distributions. Furthermore, we have implemented the HAM aerosol model in WRF-chem to also perform simulations with a fully interactive aerosol scheme. We employ a hierarchy of simulation types to understand the evolution of cloud microphysical perturbations in atmospheric convection. Idealised supercell simulations are chosen to present and test the analysis methods for a strongly confined and well-studied case. We then extend the analysis to large case study simulations of tropical convection over the Amazon rainforest. For both cases we apply our analyses to individually tracked convective cells. Our results show the impact of model uncertainties on the understanding of aerosol-convection interactions and have implications for improving process representation in models.

  18. Basic Theory Behind Parameterizing Atmospheric Convection

    NASA Astrophysics Data System (ADS)

    Plant, R. S.; Fuchs, Z.; Yano, J. I.

    2014-04-01

    Last fall, a network of the European Cooperation in Science and Technology (COST), called "Basic Concepts for Convection Parameterization in Weather Forecast and Climate Models" (COST Action ES0905; see http://w3.cost.esf.org/index.php?id=205&action_number=ES0905), organized a 10-day training course on atmospheric convection and its parameterization. The aim of the workshop, held on the island of Brac, Croatia, was to help young scientists develop an in-depth understanding of the core theory underpinning convection parameterizations. The speakers also sought to impart an appreciation of the various approximations, compromises, and ansatz necessary to translate theory into operational practice for numerical models.

  19. Can the ionosphere regulate magnetospheric convection?

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.; Kennel, C. F.

    1972-01-01

    Following a southward shift of the interplanetary magnetic field, which implies enhanced reconnection at the nose of the magnetosphere, the magnetopause shrinks from its Chapman-Ferraro equilibrium position. If the convective return of magnetic flux to the magnetopause equalled the reconnection rate, the magnetopause would not shrink. Consequently, there is a delay in the development of magnetospheric convection following the onset of reconnection, which is ascribed to line tying by the polar cusp ionosphere. A simple model relates the dayside magnetopause displacement to the currents feeding the polar cap ionosphere, from which the ionospheric electric field, and consequently, the flux return rate, may be estimated as a function of magnetopause displacement. Flux conservation arguments then permit an estimate of the time scale on which convection increases, which is not inconsistent with that of the substorm growth phase.

  20. Solutal Convection in a Magnetic Fluid

    NASA Technical Reports Server (NTRS)

    Leslie, Fred; Ramachandran, N.

    2003-01-01

    A theoretical and experimental study is presented on the stability of solutal convection of a magnetized fluid in the presence of a magnetic field. The total force on the fluid is derived and equilibrium positions are computed establishing the field necessary to counter fluid buoyancy. The requirements for stability are developed and compared with experiments with a paramagnetic fluid. The experiments are in good agreement not only with the theoretical predictions for equilibrium but also verify the stability theory which predicts both horizontal and vertical stability. Analogous to results for levitation, the theory indicates that solutal convection in paramagnetic fluids cannot be completely stabilized while that in diamagnetic liquid are possible.

  1. Natural convective mixing flows

    NASA Astrophysics Data System (ADS)

    Ramos, Eduardo; de La Cruz, Luis; del Castillo, Luis

    1998-11-01

    Natural convective mixing flows. Eduardo Ramos and Luis M. de La Cruz, National University of Mexico and Luis Del Castillo San Luis Potosi University. The possibility of mixing a fluid with a natural convective flow is analysed by solving numerically the mass, momentum and energy equations in a cubic container. Two opposite vertical walls of the container are assumed to have temperatures that oscillate as functions of time. The phase of the oscillations is chosen in such a way that alternating corrotating vortices are formed in the cavity. The mixing efficiency of this kind of flow is examined with a Lagrangian tracking technique. This work was partially financed by CONACyT-Mexico project number GE0044

  2. Oxygen abundance and convection

    NASA Astrophysics Data System (ADS)

    Van't Veer, C.; Cayrel, R.

    The triplet IR lines of O I near 777 nm are computed with the Kurucz's code, modified to accept several convection models. The program has been run with the MLT algorithm, with l/H = 1.25 and 0.5, and with the Canuto-Mazzitelli and Canuto-Goldman-Mazzitelli approaches, on a metal-poor turnoff-star model atmosphere with Teff=6200 K, log g = 4.3, [Fe/H]= -1.5. The results show that the differences in equivalent widths for the 4 cases do not exceed 2 per cent (0.3 mA). The convection treatment is therefore not an issue for the oxygen abundance derived from the permitted lines.

  3. Convective initiation in the vicinity of the subtropical Andes

    NASA Astrophysics Data System (ADS)

    Rasmussen, K. L.; Houze, R.

    2014-12-01

    Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. An investigation of the most intense storms for 11 years of TRMM Precipitation Radar (PR) data shows a tendency for squall lines to initiate and develop in this region with the canonical leading convective line/trailing stratiform structure. The synoptic environment and structures of the extreme convection and MCSs in subtropical South America are similar to those found in other regions of the world, especially the United States. In subtropical South America, however, the topographical influence on the convective initiation and maintenance of the MCSs is unique. A capping inversion in the lee of the Andes is important in preventing premature triggering. The Andes and other mountainous terrain of Argentina focus deep convective initiation in a narrow region. Subsequent to initiation, the convection often evolves into propagating mesoscale convective systems similar to those seen over the Great Plains of the U. S. and produces damaging tornadoes, hail, and floods across a wide agricultural region. Numerical simulations conducted with the NCAR Weather Research and Forecasting (WRF) Model extend the observational analysis and provide an objective evaluation of storm initiation, terrain effects, and development mechanisms. The simulated mesoscale systems closely resemble the storm structures seen by the TRMM Precipitation Radar as well as the overall shape and character of the storms shown in GOES satellite data. A sensitivity experiment with different configurations of topography, including both decreasing and increasing the height of the Andes Mountains, provides insight into the significant influence of orography in focusing convective initiation in this region. Lee cyclogenesis and a strong low-level jet are modulated by the height of the Andes Mountains and directly affect the character

  4. Application of Ground Based Microwave Radiometry for Characterizing Tropical Convection

    NASA Astrophysics Data System (ADS)

    Renju, R.; Raju, C. S.

    2016-12-01

    The characterization of the microphysical and thermodynamical properties of convective events over the tropical coastal station Thiruvananthapuram (TVM, 8.5o N 76.9oE) has been carried out by utilizing multiyear Microwave Radiometer Profiler (MRP) observations. The analyses have been extended to develop a methodology to identify convective events, based on the radiometric brightness temperature (Tb) differences, at 30 GHz and 22.5 GHz channels and are compared using reflectivity and rainfall intensity deduced from concurrent and collocated disdrometer measurements. In all 84 such convections were identified using the above methodology over the station for a period of years, 2010-2013; both during pre- and post- Indian summer monsoon months and further evaluated by computing their stability indices. The occurrence of convection over this coastal station peaks in the afternoon and early morning hours with genesis, respectively, over the land and the sea. The number of occurrence of convective events are less during monsoon deficit year whereas strong and more during heavy monsoon rainfall year. These findings are further evaluated with the percentage occurrence of fractional convective clouds derived from microwave payload SAPHIR observations on Megha-Tropique satellite. Based on the analyses the frequency of occurrence of convection can be related to the monsoonal rainfall obtaining over the region. The analyses also indicate that the microwave radiometric brightness temperature of humidity channels depicts the type of convection and respond two hours prior to the occurrence of rainfall. In addition to that the multi-angle observations of microwave radiometer profiler have been utilized to study the propagation of convective systems. This study and the methodology developed for identifying convection have significance in microwave (Ka- and W-band) satellite propagation characterization since convection and precipitation are the major hindrance to satellite

  5. 78 FR 58316 - Complex Issues in Developing Medical Devices for Pediatric Patients Affected by Rare Diseases...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-23

    ... HUMAN SERVICES Food and Drug Administration Complex Issues in Developing Medical Devices for Pediatric... (FDA) is announcing the following public workshop entitled ``Complex Issues in Developing Medical... ``Complex Issues in Developing Drug and Biological Products for Rare Diseases.'' The purpose of the...

  6. Relating mantle convection, epeirogeny and gravity anomalies

    NASA Astrophysics Data System (ADS)

    Colli, Lorenzo; Ghelichkhan, Siavash; Bunge, Hans-Peter

    2017-04-01

    Spatial variations of crustal thickness and density are the primary cause for most of Earth's topography. Indeed, short- to mid-wavelength topography and gravity anomalies can be explained with a relatively simple model that combines isostatic compensation and elastic support by the lithosphere. As the wavelength increases, however, sub-lithospheric mass anomalies play an increasingly important role, both directly and through the convective stresses that they excite: these convective stresses deform the surface, generating what is called dynamic topography, and complicate the relationship between internal mass anomalies, surface topography and the resulting gravity anomalies. Here we show that this complexity can only be captured by global, self-gravitating, viscously stratified Earth models. Moreover, sub-lithospheric mass anomalies are advected by global mantle convection — unlike near-surface mass anomalies, which stay frozen in the crust and lithosphere. Dynamic topography thus changes in time, causing epeirogenic movements. For this reason, the pattern, timing and amplitudes of past epeirogenic movements are primary geologic observables that can help constrain global mantle convection models.

  7. Balanced dynamics and convection in the tropical troposphere

    NASA Astrophysics Data System (ADS)

    Raymond, David; Fuchs, Željka; Gjorgjievska, Saška; Sessions, Sharon

    2015-09-01

    This paper presents a conceptual picture of balanced tropical tropospheric dynamics inspired by recent observations. The most important factor differentiating the tropics from middle and higher latitudes is the absence of baroclinic instability; upward motion occurs primarily via deep convective processes. Thus, convection forms an integral part of large-scale tropical motions. Since convection itself is small-scale and chaotic in detail, predictability lies in uncovering the hidden hands that guide the average behavior of convection. Two appear, balanced dynamics and thermodynamic constraints. Contrary to conventional expectations, balanced dynamics plays a crucial role in the tropical atmosphere. However, due to the smallness of the Coriolis parameter there, nonlinear balance is more important in the tropics than at higher latitudes. Three thermodynamic constraints appear to play an important role in governing the average behavior of convection outside of the cores of tropical storms. First, convection is subject to control via a lower tropospheric buoyancy quasi-equilibrium process, wherein destabilization of the lower troposphere by nonconvective processes is balanced by convective stabilization. Second, the production of precipitation is extraordinarily sensitive to the saturation fraction of the troposphere. Third, "moisture quasi-equilibrium" governs the saturation fraction, with moister atmospheres being associated with smaller moist convective instability. The moist convective instability is governed by the balanced thermodynamic response to the pattern of potential vorticity, which in turn is slowly modified by convective and radiative heating. The intricate dance between these dynamic and thermodynamic processes leads to complex behavior of the tropical atmosphere in ways that we are just beginning to understand.

  8. Rossby numbers of fully convective and partially convective stars

    NASA Astrophysics Data System (ADS)

    Landin, Natália R.; Mendes, Luiz T. S.

    2017-10-01

    In this work, we investigate the stellar magnetic activity in the theoretical point of view, through the use of stellar structure and evolution models. We present theoretical values of convective turnover times and Rossby numbers for low-mass stars, calculated with the ATON stellar structure and evolution code. We concentrate our analysis on fully convective and partially convective stars motivated by recent observations of X-ray emission of slowly rotating fully convective stars, which suggest that the presence of a tachocline is not a central key for magnetic fields generation. We investigate the behavior of the convective turnover time evolution, as well as its radial profile inside the star. A discussion about the location where the convective turnover time is calculated in the stellar interior is also addressed. Our theoretical results are compared to observational data from low-mass stars.

  9. Temperature-driven groundwater convection in cold climates

    NASA Astrophysics Data System (ADS)

    Engström, Maria; Nordell, Bo

    2016-08-01

    The aim was to study density-driven groundwater flow and analyse groundwater mixing because of seasonal changes in groundwater temperature. Here, density-driven convection in groundwater was studied by numerical simulations in a subarctic climate, i.e. where the water temperature was <4 °C. The effects of soil permeability and groundwater temperature (i.e. viscosity and density) were determined. The influence of impermeable obstacles in otherwise homogeneous ground was also studied. An initial disturbance in the form of a horizontal groundwater flow was necessary to start the convection. Transient solutions describe the development of convective cells in the groundwater and it took 22 days before fully developed convection patterns were formed. The thermal convection reached a maximum depth of 1.0 m in soil of low permeability (2.71 · 10-9 m2). At groundwater temperature close to its density maximum (4 °C), the physical size (in m) of the convection cells was reduced. Small stones or frost lenses in the ground slightly affect the convective flow, while larger obstacles change the size and shape of the convection cells. Performed simulations show that "seasonal groundwater turnover" occurs. This knowledge may be useful in the prevention of nutrient leakage to underlying groundwater from soils, especially in agricultural areas where no natural vertical groundwater flow is evident. An application in northern Sweden is discussed.

  10. A Wildfire-relevant climatology of the convective environment of the United States

    Treesearch

    Brian E. Potter; Matthew A. Anaya

    2015-01-01

    Convective instability can influence the behaviour of large wildfires. Because wildfires modify the temperature and moisture of air in their plumes, instability calculations using ambient conditions may not accurately represent convective potential for some fire plumes. This study used the North American Regional Reanalysis to develop a climatology of the convective...

  11. A New And Fundamental View Of Organized Tropical Convection

    NASA Astrophysics Data System (ADS)

    Webster, P. J.; Toma, V. E.

    2012-12-01

    During the last decade, a paradigm has emerged to explain the existence of tropical organized convection. Based on the projection of spatial and temporal patterns of observed convection onto dispersion relationships of equatorially trapped very shallow modes (h=10-30 m, where h is the equivalent depth of a shallow fluid) the convectively coupled equatorial mode (CCEM) theory has developed. However, there is an incompleteness and some inconsistencies in the theory that need to be addressed. Whereas the horizontal structure of these shallow modes appears similar to that observed, the vertical structure consistent with small h requires a high vertical wave number. This is not observed. Second, basic scaling of the tropics, as initially undertaken by Charney in the 1960s suggests an extremely stable vertical structure, far more stable than equivalent scales at higher latitudes. In fact, at the scales of observed organized convection in the tropics (about 106m) the atmosphere is essentially barotropic to high approximation resulting in almost complete lack of communication between the upper and lower troposphere. The CCEM theory suggests that the observed modes are consistent with existing convection but there is no explanation of how the convection forms and organizes in this very stable tropical environment. It is also noted that there are discrete genesis regions of organized convection formation within the tropics and that organized convection does not occur indiscriminately. Based on these factors we propose that organized convection occurs through regional instabilities of the basic state in which vortex tube stretching overcomes the inherent stability restriction. The instabilities determine the spatial and temporal scales of the convective phenomena. We provide examples of instabilities. Further, in certain regions, influences from higher latitudes may be important. In the end, CCEMs appears as a result and not an explanation or a cause of organized convection.

  12. The influence of convection parameterisations under alternate climate conditions

    NASA Astrophysics Data System (ADS)

    Rybka, Harald; Tost, Holger

    2013-04-01

    In the last decades several convection parameterisations have been developed to consider the impact of small-scale unresolved processes in Earth System Models associated with convective clouds. Global model simulations, which have been performed under current climate conditions with different convection schemes, significantly differ among each other in the simulated precipitation patterns due to the parameterisation assumptions and formulations, e.g. the simplified treatment of the cloud microphysics. Additionally, the simulated transport of short-lived trace gases strongly depends on the chosen convection parameterisation due to the differences in the vertical redistribution of mass. Furthermore, other meteorological parameters like the temperature or the specific humidity show substantial differences in convectively active regions. This study presents uncertainties of climate change scenarios caused by different convection parameterisations. For this analysis two experiments (reference simulation with a CO2 concentration of 348 ppm; 2xCO2-simulation with a CO2 concentration of 696 ppm) are calculated with the ECHAM/MESSy atmospheric chemistry (EMAC) model applying four different convection schemes (Tiedtke, ECMWF, Emanuel and Zhang-McFarlane - Hack) and two resolutions (T42 and T63), respectively. The results indicate that the equilibrium climate sensitivity is independent of the chosen convection parameterisation. However, the regional temperature increase, induced by a doubling of the carbon dioxide concentration, demonstrates differences of up to a few Kelvin at the surface as well as in the UTLS for the ITCZ region depending on the selected convection parameterisation. The interaction between cloud and convection parameterisations results in a large disagreement of precipitation patterns. Although every 2xCO2 -experiment simulates an increase in global mean precipitation rates, the change of regional precipitation patterns differ widely. Finally, analysing

  13. Free convection in the Matian atmosphere

    NASA Technical Reports Server (NTRS)

    Clow, G. D.; Haberle, R. M.

    1990-01-01

    The 'free convective' regime for the Martian atmospheric boundary layer (ABL) was investigated. This state occurs when the mean windspeed at the top of the ABL drops below some critical value U(sub c) and positive buoyant forces are present. Such forces can arise either from vertical temperature or water vapor gradients across the atmospheric surface layer. During free convection, buoyant forces drive narrow plumes that ascend to the inversion height with a return circulation consisting of broad slower-moving downdraughts. Horizontal pressure, temperature, windspeed, and water vapor fluctuations resulting form this circulation pattern can be quite large adjacent to the ground (within the surface layer). The local turbulent fluctuations cause non-zero mean surface stresses, sensible heat fluxes, and latent heat fluxes, even when the mean regional windspeed is zero. Although motions above the surface layer are insensitive to the nature of the surface, the sensible and latent heat fluxes are primarily controlled by processes within the interfacial sublayer immediately adjacent to the ground during free convection. Thus the distinction between aerodynamically smooth and rough airflow within the interfacial sublayer is more important than for the more typical situation where the mean regional windspeed is greater than U(sub c). Buoyant forces associated with water vapor gradients are particularly large on Mars at low pressures and high temperatures when the surface relative humidity is 100 percent, enhancing the likelihood of free convection under these conditions. On this basis, Ingersol postulated the evaporative heat losses from an icy surface on Mars at 237 K and current pressures would exceed the available net radiative flux at the surface, thus prohibiting ice from melting at low atmospheric pressures. Schumann has developed equations describing the horizontal fluctuations and mean vertical gradients occurring during free convection. Schumann's model was

  14. Complexity.

    PubMed

    Gómez-Hernández, J Jaime

    2006-01-01

    It is difficult to define complexity in modeling. Complexity is often associated with uncertainty since modeling uncertainty is an intrinsically difficult task. However, modeling uncertainty does not require, necessarily, complex models, in the sense of a model requiring an unmanageable number of degrees of freedom to characterize the aquifer. The relationship between complexity, uncertainty, heterogeneity, and stochastic modeling is not simple. Aquifer models should be able to quantify the uncertainty of their predictions, which can be done using stochastic models that produce heterogeneous realizations of aquifer parameters. This is the type of complexity addressed in this article.

  15. Peculiarities of convection and oil maturation in 3D porous medium structure.

    NASA Astrophysics Data System (ADS)

    Yurie Khachay, Professor; Mindubaev, Mansur

    2017-04-01

    An important estimation of oil source thickness productivity is to study the thermal influences of magmatic intrusions on the maturation of the organic matter. The heterogeneity of permeability distribution of the reservoir rock and respectively the convection structure provide temperature heterogeneity and different degree of maturity for the oil source material. A numerical algorithm for solving the problem of developed convection in two-dimensional and three-dimensional models of the porous medium, which consists of a system of Darcy equations, heat conduction with convection term and the continuity equation, is developed. Because of the effective values of the coefficients of thermal conductivity, heat capacity, viscosity and permeability of the medium depend from the temperature; the system of equations is nonlinear. For solution we used the dimensionless system of coordinates. For numerical solution we used the longitudinal cross-implicit scheme. The coordinates step for the 3D model had been used constant and equal to H/20, where H=1- dimensionless thickness of porous medium layer. As it is shown from the variants of numerical solution, by the stationary regime of developed convection because of the temperature heterogeneous distribution in the sedimentary reservoir the formation of oil source matter different degree of maturity is possible. That result is very significant for estimation of reservoirs oil-bearing The work was fulfilled by supporting of the Fund of UB RAS, project 1518532. Reference 1. Yurie Khachay and Mansur Mindubaev, 2016, Effect of convective transport in porous media on the conductions of organic matter maturation and generation of hydrocarbons in trap rocks complexes, Energy Procedia. 74 pp.79-83.

  16. Lattice Boltzmann model for nonlinear convection-diffusion equations.

    PubMed

    Shi, Baochang; Guo, Zhaoli

    2009-01-01

    A lattice Boltzmann model for convection-diffusion equation with nonlinear convection and isotropic-diffusion terms is proposed through selecting equilibrium distribution function properly. The model can be applied to the common real and complex-valued nonlinear evolutionary equations, such as the nonlinear Schrödinger equation, complex Ginzburg-Landau equation, Burgers-Fisher equation, nonlinear heat conduction equation, and sine-Gordon equation, by using a real and complex-valued distribution function and relaxation time. Detailed simulations of these equations are performed, and it is found that the numerical results agree well with the analytical solutions and the numerical solutions reported in previous studies.

  17. Correlations for laminar mixed convection flows on vertical, inclined, and horizontal flat plates

    NASA Astrophysics Data System (ADS)

    Chen, T. S.; Armaly, B. F.; Ramachandran, N.

    1986-11-01

    Local Nusselt numbers for laminar mixed convection flows along isothermal vertical, inclined, and horizontal flat plates are presented for the entire mixed convection regime for a wide range of Prandtl numbers. Simple correlation equations for the local and average mixed convection Nusselt numbers are developed, which are found to agree well with the numerically predicted values and available experimental data for both buoyancy assisting and opposing flow conditions. The threshold values of significant buoyancy effects on forced convection and forced flow effects on free convection, as well as the maximum increase in the local mixed convection Nusselt number from the respective pure convection limits, are also presented for all flow configurations. It is found that the buoyancy or forced flow effect can increase the surface heat transfer rate from pure forced or pure free convection by about 20 percent.

  18. MITT writer and MITT writer advanced development: Developing authoring and training systems for complex technical domains

    NASA Technical Reports Server (NTRS)

    Wiederholt, Bradley J.; Browning, Elica J.; Norton, Jeffrey E.; Johnson, William B.

    1991-01-01

    MITT Writer is a software system for developing computer based training for complex technical domains. A training system produced by MITT Writer allows a student to learn and practice troubleshooting and diagnostic skills. The MITT (Microcomputer Intelligence for Technical Training) architecture is a reasonable approach to simulation based diagnostic training. MITT delivers training on available computing equipment, delivers challenging training and simulation scenarios, and has economical development and maintenance costs. A 15 month effort was undertaken in which the MITT Writer system was developed. A workshop was also conducted to train instructors in how to use MITT Writer. Earlier versions were used to develop an Intelligent Tutoring System for troubleshooting the Minuteman Missile Message Processing System.

  19. Dielectrophoretic Rayleigh-Bénard convection under microgravity conditions.

    PubMed

    Yoshikawa, H N; Tadie Fogaing, M; Crumeyrolle, O; Mutabazi, I

    2013-04-01

    Thermal convection in a dielectric fluid layer between two parallel plates subjected to an alternating electric field and a temperature gradient is investigated under microgravity conditions. A thermoelectric coupling resulting from the thermal variation of the electric permittivity of the fluid produces the dielectrophoretic (DEP) body force, which can be regarded as thermal buoyancy due to an effective gravity. This electric gravity can destabilize a stationary conductive state of the fluid to develop convection. The similarity of the DEP thermal convection with the Rayleigh-Bénard (RB) convection is examined by considering its behavior in detail by a linear stability theory and a two-dimensional direct numerical simulation. The results are analyzed from an energetic viewpoint and in the framework of the Ginzburg-Landau (GL) equation. The stabilizing effects of a thermoelectric feedback make the critical parameters different from those in the RB instability. The nonuniformity of the electric gravity arising from the finite variation of permittivity also affects the critical parameters. The characteristic constants of the GL equation are comparable with those for the RB convection. The heat transfer in the DEP convection is weaker than in the RB convection as a consequence of the feedback that impedes the convection.

  20. Reverse Polar Cap convection and effects on PC indices

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2017-04-01

    The convection of magnetospheric and ionospheric plasma across the polar caps relates to properties of the solar wind, primarily the velocity (Vsw) and the sign and magnitude of the Z-component, Bz, of the Interplanetary Magnetic Field (IMF). When Bz is negative (southward) or just small in magnitude, then the convection across the polar cap is antisunward with return flows in the morning and evening sectors of the auroral oval. When IMF Bz is strong and positive (northward) then strong sunward convection may develop in the central polar cap with return flows poleward of the usual auroral oval (NBZ conditions). In addition to depending on the strength of IMF Bz, the magnitude of the reverse convection relates to the ionospheric conditions varying with local time, season and solar cycle, and also to the geomagnetic field configuration. The ionospheric convection creates oppositely directed currents that generate the magnetic variations reflected in the Polar Cap (PC) indices. The immediate effect of reverse convection is to give negative values of the PC index. However, inclusion of reverse convection events in the data base used to derive the index coefficients has adverse consequences for the quality of the PC index. The presentation shall illustrate the properties of reverse polar cap convection and discuss the differing effects on the Northern (PCN) and Southern (PCS) indices.

  1. Assembly of Photosynthetic Antenna Protein / Pigments Complexes from Algae and Plants for Development of Nanobiodevices

    DTIC Science & Technology

    2012-07-10

    Assembly of Photosynthetic Antenna Protein / Pigments Complexes from Algae and Plants for Development of Nanobiodevices Key...Assembly of Photosynthetic Antenna Protein / Pigments Complexes from Algae and Plants for Development of Nanobiodevices 5a. CONTRACT NUMBER...unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT This is the report of a project to use photosynthetic antenna pigment complexes from algae and plants as

  2. Double-diffusive inner core convective translation

    NASA Astrophysics Data System (ADS)

    Deguen, Renaud; Alboussière, Thierry; Labrosse, Stéphane

    2016-04-01

    The hemispherical asymmetry of the inner core has been interpreted as resulting form a high-viscosity mode of inner core convection, consisting in a translation of the inner core. With melting on one hemisphere and crystallization on the other one, inner core translation would impose a strongly asymmetric buoyancy flux at the bottom of the outer core, with likely strong implications for the dynamics of the outer core and the geodynamo. The main requirement for convective instability in the inner core is an adverse radial density gradient. While older estimates of the inner core thermal conductivity favored a superadiabatic temperature gradient and the existence of thermal convection, the much higher values recently proposed makes thermal convection very unlikely. Compositional convection might be a viable alternative to thermal convection: an unstable compositional gradient may arise in the inner core either because the light elements present in the core are predicted to become increasingly incompatible as the inner core grows (Gubbins et al. 2013), or because of a possibly positive feedback of the development of the F-layer on inner core convection. Though the magnitude of the destabilizing effect of the compositional field is predicted to be similar to or smaller than the stabilizing effect of the thermal field, the huge difference between thermal and chemical diffusivities implies that double-diffusive instabilities can still arise even if the net density decreases upward. We propose here a theoretical and numerical study of double diffusive convection in the inner core that demonstrate that a translation mode can indeed exist if the compositional field is destabilizing, even if the temperature profile is subadiabatic, and irrespectively of the relative magnitude of the destabilizing compositional gradient and stabilizing temperature field. The predicted inner core translation rate is similar to the mean inner core growth rate, which is more consistent with

  3. Finite Element Modeling of Magnetically-Damped Convection during Solidification

    NASA Technical Reports Server (NTRS)

    deGroh, H. C.; Li, B. Q.; Lu, X.

    1998-01-01

    A fully 3-D, transient finite element model is developed to represent the magnetic damping effects on complex fluid flow, heat transfer and electromagnetic field distributions in a Sn- 35.5%Pb melt undergoing unidirectional solidification. The model is developed based on our in- house finite element code for the fluid flow, heat transfer and electromagnetic field calculations. The numerical model is tested against numerical and experimental results for water as reported in literature. Various numerical simulations are carried out for the melt convection and temperature distribution with and without the presence of a transverse magnetic field. Numerical results show that magnetic damping can be effectively applied to stabilize melt flow, reduce turbulence and flow levels in the melt and over a certain threshold value a higher magnetic field resulted in a greater reduction in velocity. Also, for the study of melt flow instability, a long enough running time is needed to ensure the final fluid flow recirculation pattern. Moreover, numerical results suggest that there seems to exist a threshold value of applied magnetic field, above which magnetic damping becomes possible and below which the 0 convection in the melt is actually enhanced.

  4. Plasma convection in Neptune's magnetosphere

    NASA Technical Reports Server (NTRS)

    Selesnick, R. S.

    1990-01-01

    The magnetosphere of Neptune changes its magnetic configuration continuously as the planet rotates, leading to a strong modulation of the convection electric field. Even though the corotation speed is considerably larger, the modulation causes the small convection speed to have a cumulative effect, much like the acceleration of particles in a cyclotron. A model calculation shows that plasma on one side of the planet convects out of the magnetosphere in a few planetary rotations, while on the other side it convects slowly planetward. The observation of nitrogen ions from a Triton plasma torus may provide a critical test of the model.

  5. Education: DNA replication using microscale natural convection.

    PubMed

    Priye, Aashish; Hassan, Yassin A; Ugaz, Victor M

    2012-12-07

    There is a need for innovative educational experiences that unify and reinforce fundamental principles at the interface between the physical, chemical, and life sciences. These experiences empower and excite students by helping them recognize how interdisciplinary knowledge can be applied to develop new products and technologies that benefit society. Microfluidics offers an incredibly versatile tool to address this need. Here we describe our efforts to create innovative hands-on activities that introduce chemical engineering students to molecular biology by challenging them to harness microscale natural convection phenomena to perform DNA replication via the polymerase chain reaction (PCR). Experimentally, we have constructed convective PCR stations incorporating a simple design for loading and mounting cylindrical microfluidic reactors between independently controlled thermal plates. A portable motion analysis microscope enables flow patterns inside the convective reactors to be directly visualized using fluorescent bead tracers. We have also developed a hands-on computational fluid dynamics (CFD) exercise based on modeling microscale thermal convection to identify optimal geometries for DNA replication. A cognitive assessment reveals that these activities strongly impact student learning in a positive way.

  6. Zoned mantle convection.

    PubMed

    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  7. Bidispersive-inclined convection

    PubMed Central

    Mulone, Giuseppe; Straughan, Brian

    2016-01-01

    A model is presented for thermal convection in an inclined layer of porous material when the medium has a bidispersive structure. Thus, there are the usual macropores which are full of a fluid, but there are also a system of micropores full of the same fluid. The model we employ is a modification of the one proposed by Nield & Kuznetsov (2006 Int. J. Heat Mass Transf. 49, 3068–3074. (doi:10.1016/j.ijheatmasstransfer.2006.02.008)), although we consider a single temperature field only. PMID:27616934

  8. Bidispersive-inclined convection

    NASA Astrophysics Data System (ADS)

    Falsaperla, Paolo; Mulone, Giuseppe; Straughan, Brian

    2016-08-01

    A model is presented for thermal convection in an inclined layer of porous material when the medium has a bidispersive structure. Thus, there are the usual macropores which are full of a fluid, but there are also a system of micropores full of the same fluid. The model we employ is a modification of the one proposed by Nield & Kuznetsov (2006 Int. J. Heat Mass Transf. 49, 3068-3074. (doi:10.1016/j.ijheatmasstransfer.2006.02.008)), although we consider a single temperature field only.

  9. Modes of tilting during extensional core complex development.

    PubMed

    Coleman, D S; Walker, J D

    1994-01-14

    Crustal extension and formation of the Mineral Mountains core complex, Utah, involved tilting of the Mineral Mountains batholith and associated faults during hanging wall and footwall deformation. The batholith was folded in the hanging wall of the Beaver Valley fault between 11 and 9 million years ago yielding about 45 degrees of tilt. Subsequently, the batholith was unroofed along the Cave Canyon detachment fault, and the batholith and fault were tilted approximately 40 degrees during footwall uplift. Recognition of deformed dikes beneath the detachment fault establishes the importance of footwall tilt during formation of extensional core complexes and demonstrates that footwall rebound can be an important process during extension.

  10. The link between extreme precipitation and convective organization in a warming climate: Global radiative-convective equilibrium simulations

    NASA Astrophysics Data System (ADS)

    Pendergrass, Angeline G.; Reed, Kevin A.; Medeiros, Brian

    2016-11-01

    The rate of increase of extreme precipitation in response to global warming varies dramatically across climate model simulations, particularly over the tropics, for reasons that have yet to be established. Here we propose one potential mechanism: changing organization of convection with climate. We analyze a set of simulations with the Community Atmosphere Model version 5 with an idealized global radiative-convective equilibrium configuration forced by fixed sea surface temperatures varying in 2° increments from 285 to 307 K. In these simulations, convective organization varies from semiorganized in cold simulations, disorganized in warm simulations, and abruptly becomes highly organized at just over 300 K. The change in extreme precipitation with warming also varies across these simulations, including a large increase at the transition from disorganized to organized convection. We develop an extreme precipitation-focused metric for convective organization and use this to explore their connection.

  11. 3D features of delayed thermal convection in fault zones: consequences for deep fluid processes in the Tiberias Basin, Jordan Rift Valley

    NASA Astrophysics Data System (ADS)

    Magri, Fabien; Möller, Sebastian; Inbar, Nimrod; Siebert, Christian; Möller, Peter; Rosenthal, Eliyahu; Kühn, Michael

    2015-04-01

    It has been shown that thermal convection in faults can also occur for subcritical Rayleigh conditions. This type of convection develops after a certain period and is referred to as "delayed convection" (Murphy, 1979). The delay in the onset is due to the heat exchange between the damage zone and the surrounding units that adds a thermal buffer along the fault walls. Few numerical studies investigated delayed thermal convection in fractured zones, despite it has the potential to transport energy and minerals over large spatial scales (Tournier, 2000). Here 3D numerical simulations of thermally driven flow in faults are presented in order to investigate the impact of delayed convection on deep fluid processes at basin-scale. The Tiberias Basin (TB), in the Jordan Rift Valley, serves as study area. The TB is characterized by upsurge of deep-seated hot waters along the faulted shores of Lake Tiberias and high temperature gradient that can locally reach 46 °C/km, as in the Lower Yarmouk Gorge (LYG). 3D simulations show that buoyant flow ascend in permeable faults which hydraulic conductivity is estimated to vary between 30 m/yr and 140 m/yr. Delayed convection starts respectively at 46 and 200 kyrs and generate temperature anomalies in agreement with observations. It turned out that delayed convective cells are transient. Cellular patterns that initially develop in permeable units surrounding the faults can trigger convection also within the fault plane. The combination of these two convective modes lead to helicoidal-like flow patterns. This complex flow can explain the location of springs along different fault traces of the TB. Besides being of importance for understanding the hydrogeological processes of the TB (Magri et al., 2015), the presented simulations provide a scenario illustrating fault-induced 3D cells that could develop in any geothermal system. References Magri, F., Inbar, N., Siebert, C., Rosenthal, E., Guttman, J., Möller, P., 2015. Transient

  12. A Cognitive Complexity Metric Applied to Cognitive Development

    ERIC Educational Resources Information Center

    Andrews, Glenda; Halford, Graeme S.

    2002-01-01

    Two experiments tested predictions from a theory in which processing load depends on relational complexity (RC), the number of variables related in a single decision. Tasks from six domains (transitivity, hierarchical classification, class inclusion, cardinality, relative-clause sentence comprehension, and hypothesis testing) were administered to…

  13. A Cognitive Complexity Metric Applied to Cognitive Development

    ERIC Educational Resources Information Center

    Andrews, Glenda; Halford, Graeme S.

    2002-01-01

    Two experiments tested predictions from a theory in which processing load depends on relational complexity (RC), the number of variables related in a single decision. Tasks from six domains (transitivity, hierarchical classification, class inclusion, cardinality, relative-clause sentence comprehension, and hypothesis testing) were administered to…

  14. Language Development: Syntactical Complexity of Reservation Sioux Indian Children.

    ERIC Educational Resources Information Center

    Iverson, Dorothy

    The purpose of this study was to describe the syntactical complexity of the level of English which is easily understood and freely used by a selected group of bilingual Sioux Indian children. The study was designed to determine a basis for a lack of language fluency as a contributing factor in the cross-over phenomenon of these Indian children in…

  15. Gravity Waves Generated by Convection: A New Idealized Model Tool and Direct Validation with Satellite Observations

    NASA Astrophysics Data System (ADS)

    Alexander, M. Joan; Stephan, Claudia

    2015-04-01

    In climate models, gravity waves remain too poorly resolved to be directly modelled. Instead, simplified parameterizations are used to include gravity wave effects on model winds. A few climate models link some of the parameterized waves to convective sources, providing a mechanism for feedback between changes in convection and gravity wave-driven changes in circulation in the tropics and above high-latitude storms. These convective wave parameterizations are based on limited case studies with cloud-resolving models, but they are poorly constrained by observational validation, and tuning parameters have large uncertainties. Our new work distills results from complex, full-physics cloud-resolving model studies to essential variables for gravity wave generation. We use the Weather Research Forecast (WRF) model to study relationships between precipitation, latent heating/cooling and other cloud properties to the spectrum of gravity wave momentum flux above midlatitude storm systems. Results show the gravity wave spectrum is surprisingly insensitive to the representation of microphysics in WRF. This is good news for use of these models for gravity wave parameterization development since microphysical properties are a key uncertainty. We further use the full-physics cloud-resolving model as a tool to directly link observed precipitation variability to gravity wave generation. We show that waves in an idealized model forced with radar-observed precipitation can quantitatively reproduce instantaneous satellite-observed features of the gravity wave field above storms, which is a powerful validation of our understanding of waves generated by convection. The idealized model directly links observations of surface precipitation to observed waves in the stratosphere, and the simplicity of the model permits deep/large-area domains for studies of wave-mean flow interactions. This unique validated model tool permits quantitative studies of gravity wave driving of regional

  16. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of + or - 15 percent.

  17. Parameterization of convective clouds, mesoscale convective systems, and convective-generated cirrus

    SciTech Connect

    Cotton, W.R.

    1992-03-03

    A level 2.5w deep convection updraft/downdraft parameterization scheme has been refined and tested against 3D simulations of sea-breeze generated convection over S. Florida. Cases for explicit simulation of MCSs in mid-latitudes and tropics have been encouraging. After a few refinements in those cases, fine resolution explicit simualtions of deep convection and mesoscale, stratiform clouds will be begun.

  18. Improving representation of convective transport for scale-aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott; Dong, Xiquan; Zhang, Guang J.; Chen, Qian; Kollias, Pavlos; Ghan, Steven J.

    2015-04-01

    The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Ze in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.

  19. Improving representation of convective transport for scale-aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics

    SciTech Connect

    Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott; Dong, Xiquan; Zhang, Guang J; Qian, Chen; Kollias, Pavlos; Ghan, Steven

    2015-04-27

    The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) themodel tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Ze in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes

  20. Megacrystals track magma convection between reservoir and surface

    NASA Astrophysics Data System (ADS)

    Moussallam, Yves; Oppenheimer, Clive; Scaillet, Bruno; Buisman, Iris; Kimball, Christine; Dunbar, Nelia; Burgisser, Alain; Ian Schipper, C.; Andújar, Joan; Kyle, Philip

    2015-03-01

    Active volcanoes are typically fed by magmatic reservoirs situated within the upper crust. The development of thermal and/or compositional gradients in such magma chambers may lead to vigorous convection as inferred from theoretical models and evidence for magma mixing recorded in volcanic rocks. Bi-directional flow is also inferred to prevail in the conduits of numerous persistently-active volcanoes based on observed gas and thermal emissions at the surface, as well as experiments with analogue models. However, more direct evidence for such exchange flows has hitherto been lacking. Here, we analyse the remarkable oscillatory zoning of anorthoclase feldspar megacrystals erupted from the lava lake of Erebus volcano, Antarctica. A comprehensive approach, combining phase equilibria, solubility experiments and melt inclusion and textural analyses shows that the chemical profiles are best explained as a result of multiple episodes of magma transport between a deeper reservoir and the lava lake at the surface. Individual crystals have repeatedly travelled up-and-down the plumbing system, over distances of up to several kilometers, presumably as a consequence of entrainment in the bulk magma flow. Our findings thus corroborate the model of bi-directional flow in magmatic conduits. They also imply contrasting flow regimes in reservoir and conduit, with vigorous convection in the former (regular convective cycles of ∼150 days at a speed of ∼0.5 mm s-1) and more complex cycles of exchange flow and re-entrainment in the latter. We estimate that typical, 1-cm-wide crystals should be at least 14 years old, and can record several (from 1 to 3) complete cycles between the reservoir and the lava lake via the conduit. This persistent recycling of phonolitic magma is likely sustained by CO2 fluxing, suggesting that accumulation of mafic magma in the lower crust is volumetrically more significant than that of evolved magma within the edifice.

  1. Using the Convective Cloud Field Model (CCFM) to investigate aerosol-convection interactions in ECHAM6-HAM

    NASA Astrophysics Data System (ADS)

    Kipling, Zak; Stier, Philip; Wagner, Till

    2014-05-01

    Convection plays an important role in the climate system through its effects on radiation, precipitation, large-scale dynamics and vertical transport of aerosols and trace gases. The effects of aerosols on the development of convective cloud and precipitation are a source of considerable uncertainty in current climate modelling. Most current global climate models use 'mass-flux' convection schemes, which represent the ensemble of convective clouds in a GCM column by a single 'mean' updraught. In addition to over-simplifying the representation of such clouds, this presents particular problems in the context of aerosol-convection interactions: firstly because the relationship between aerosol and the droplet size distribution depends on the vertical velocity distribution, about which little or no information is available, and secondly because the effects of convective transport and scavenging may vary nonlinearly over the ensemble (e.g. between precipitating and non-precipitating clouds and due to different loadings). The Convective Cloud Field Model (CCFM) addresses these limitations by simulating a spectrum of updraughts with different cross-sectional areas within each GCM column, based on the quasi-equilibrium approach of Arakawa and Schubert. For each cloud type, an entraining Lagrangian parcel model is initiated by perturbations at the surface, allowing a realistic vertical velocity to develop by cloud base so that detailed size-resolved microphysics can be represented within the cloud above. These different cloud types interact via competition for resolved-scale convective available potential energy (CAPE). Transport of water, aerosol and other tracers is calculated separately for each cloud type, allowing for different entrainment and scavenging behaviours. By using CCFM embedded within the ECHAM6-HAM aerosol-climate model, we show how this approach can both improve the distribution of convective precipitation events compared to a typical mass-flux scheme, and

  2. The role of habitat complexity in community development is mediated by resource availability.

    PubMed

    Smith, Rachel S; Johnston, Emma L; Clark, Graeme F

    2014-01-01

    Habitat complexity strongly affects the structure and dynamics of ecological communities, with increased complexity often leading to greater species diversity and abundance. However, habitat complexity changes as communities develop, and some species alter their environment to themselves provide habitat for other species. Most experimental studies manipulate basal substrate complexity, and while the importance of complexity likely changes during community development, few studies have examined the temporal dynamics of this variable. We used two experiments to quantify the importance of basal substrate complexity to sessile marine invertebrate community development through space and time. First, we compared effects of substrate complexity at 70 sites across ten estuaries. Sites differed in recruitment and community development rates, and after three months provided spatial variation in community development stage. Second, we tested for effects of substrate complexity at multiple times at a single site. In both experiments, complexity affected marine sessile invertebrate community composition in the early stages of community development when resource availability was high. Effects of complexity diminished through time as the amount of available space (the primary limiting resource) declined. Our work suggests the presence of a bare-space threshold, at which structural complexity of the basal substrate is overwhelmed by secondary biotic complexity. This threshold will be met at different times depending on local recruitment and growth rates and is likely to vary with productivity gradients.

  3. The Role of Habitat Complexity in Community Development Is Mediated by Resource Availability

    PubMed Central

    Smith, Rachel S.; Johnston, Emma L.; Clark, Graeme F.

    2014-01-01

    Habitat complexity strongly affects the structure and dynamics of ecological communities, with increased complexity often leading to greater species diversity and abundance. However, habitat complexity changes as communities develop, and some species alter their environment to themselves provide habitat for other species. Most experimental studies manipulate basal substrate complexity, and while the importance of complexity likely changes during community development, few studies have examined the temporal dynamics of this variable. We used two experiments to quantify the importance of basal substrate complexity to sessile marine invertebrate community development through space and time. First, we compared effects of substrate complexity at 70 sites across ten estuaries. Sites differed in recruitment and community development rates, and after three months provided spatial variation in community development stage. Second, we tested for effects of substrate complexity at multiple times at a single site. In both experiments, complexity affected marine sessile invertebrate community composition in the early stages of community development when resource availability was high. Effects of complexity diminished through time as the amount of available space (the primary limiting resource) declined. Our work suggests the presence of a bare-space threshold, at which structural complexity of the basal substrate is overwhelmed by secondary biotic complexity. This threshold will be met at different times depending on local recruitment and growth rates and is likely to vary with productivity gradients. PMID:25054325

  4. Boundary-modulated Thermal Convection Model in the Mantle

    NASA Astrophysics Data System (ADS)

    Kurita, K.; Kumagai, I.

    2008-12-01

    is a good example of the consequence of mutual interactions between convective flow and the heterogeneity in boundary. We propose this is a basic framework of the mantle dynamics which can reconcile apparent discrepancy between observed seismic signatures and corresponding convective motion. As a conclusion we would like to emphasize the analog experiments is a useful tool for developing/breeding new ideas.

  5. Active control of convection

    NASA Astrophysics Data System (ADS)

    Singer, Jonathan; Bau, Haim H.

    1991-12-01

    It is demonstrated theoretically that active (feedback) control can be used to alter the characteristics of thermal convection in a toroidal, vertical loop heated from below and cooled from above. As the temperature difference between the heated and cooled sections of the loop increases, the flow in the uncontrolled loop changes from no motion to steady, time-independent motion to temporally oscillatory, chaotic motion. With the use of a feedback controller effecting small perturbations in the boundary conditions, one can maintain the no-motion state at significantly higher temperature differences than the critical one corresponding to the onset of convection in the uncontrolled system. Alternatively, one can maintain steady, time-independent flow under conditions in which the flow would otherwise be chaotic. That is, the controller can be used to suppress chaos. Likewise, it is possible to stabilize periodic nonstable orbits that exist in the chaotic regime of the uncontrolled system. Finally, the controller also can be used to induce chaos in otherwise laminar (fully predictable), nonchaotic flow.

  6. Large Eddy Simulations of Severe Convection Induced Turbulence

    NASA Technical Reports Server (NTRS)

    Ahmad, Nash'at; Proctor, Fred

    2011-01-01

    Convective storms can pose a serious risk to aviation operations since they are often accompanied by turbulence, heavy rain, hail, icing, lightning, strong winds, and poor visibility. They can cause major delays in air traffic due to the re-routing of flights, and by disrupting operations at the airports in the vicinity of the storm system. In this study, the Terminal Area Simulation System is used to simulate five different convective events ranging from a mesoscale convective complex to isolated storms. The occurrence of convection induced turbulence is analyzed from these simulations. The validation of model results with the radar data and other observations is reported and an aircraft-centric turbulence hazard metric calculated for each case is discussed. The turbulence analysis showed that large pockets of significant turbulence hazard can be found in regions of low radar reflectivity. Moderate and severe turbulence was often found in building cumulus turrets and overshooting tops.

  7. Spatial symmetry breaking in rapidly rotating convective spherical shells

    NASA Technical Reports Server (NTRS)

    Zhang, Keke; Schubert, Gerald

    1995-01-01

    Many problems in geophysical and astrophysical convection systems are characterized by fast rotation and spherical shell geometry. The combined effects of Coriolis forces and spherical shell geometry produce a unique spatial symmetry for the convection pattern in a rapidly rotating spherical shell. In this paper, we first discuss the general spatial symmetries for rotating spherical shell convection. A special model, a spherical shell heated from below, is then used to illustrate how and when the spatial symmetries are broken. Symmetry breaking occurs via a sequence of spatial transitions from the primary conducting state to the complex multiple-layered columnar structure. It is argued that, because of the dominant effects of rotation, the sequence of spatial transitions identified from this particular model is likely to be generally valid. Applications of the spatial symmetry breaking to planetary convection problems are also discussed.

  8. 3D Numerical Modeling of Thermal Convection in Multiple Fractures

    NASA Astrophysics Data System (ADS)

    Patterson, J. W.; Driesner, T.; Matthai, S.

    2016-12-01

    Thermal convection of water in the subsurface alters the thermal profile with depth by moving less dense, hotter water closer to the surface. This has many implications for geothermal exploitation and is well understood in porous media as well as single, planar faults or fractures. However, relatively little research has been done on thermal convection in multiple fractures. This scenario typifies enhanced geothermal systems (EGS), in which fluid transport is nearly exclusively within fractures. This research seeks to understand the fundamental behavior of thermal convection in fractured media using the Complex Systems Modeling Platform (CSMP++), a finite-element/finite-volume simulation platform. 3D models with unstructured meshes were created to investigate convection patterns formed in single, multiple parallel, and multiple intersecting fractures within a rock unit bounded above and below by impermeable rock. Fractures are modeled discretely as lower dimensional surfaces, and the full temperature and pressure dependencies of water properties are included. We show that thermal convection cells within a fracture can influence the behavior of cells in neighboring, unconnected fractures, within a certain distance. This may result in large-scale, particularly oriented thermal anomalies in both parallel fractures and multiple, intersecting fracture sets. It can also induce convection in otherwise non-convective fractures. As fracture spacing decreases, temperature patterns are increasingly similar to those in porous and permeable media. This research lays the groundwork for further investigation of thermal convection in geologically realistic fracture networks, and could aid in the interpretation of temperature patterns and fracture networks observed in EGS fields. We also show that the Rayleigh stability criteria for fracture convection may not be applicable to parallel fractures with spacing below a certain value nor to intersecting fractures.

  9. Volcanic Development of the Rockeskyller Kopf Complex, West Eifel, Germany

    NASA Astrophysics Data System (ADS)

    Woodland, A. B.; Shaw, C. S.; Trenholm, N. D.

    2006-05-01

    The West Eifel volcanic field comprises at least 240 volcanic edifices that formed over the last 700 ka. Although the most recent eruption is dated at 10,000 years BP, geophysical evidence suggests the field is not yet extinct. Assessing the hazard potential for the region requires understanding of the time scales of volcanism in the field, particularly since many centers exhibit a multi-stage history. We are undertaking a detailed study of Rockeskyller Kopf, one of the best exposed and most complete volcanic complex in the West Eifel. To date, about 200m of tephra stratigraphy have been logged and sampled. This composite volcano, dated at 500±100 ka, consists of 6 distinct centers separated in both space and time. Each center reveals a history ranging from 1 to more than 100 individual eruptive events. Tephra deposits of the earliest eruptive phase are distinct from all others as expressed by a large country rock component and a significant quantity of clinopyroxenite and mantle-derived xenoliths. This package is strongly eroded with numerous local cut-and-fill channels and has a distinct angular unconformity with the overlying units. Phase 2 deposits are generally more scoriaceous and less phreatomagmatic. These deposits are also truncated by erosional surfaces. Phase 3 units are preserved only locally in a paleotopographic low and have a renewed phreatomagmatic character, containing a high crustal xenolith component. One thin layer even contains rounded quartz pebbles. Deposits of the fourth eruptive phase unconformably overlie those of phase 3. One massive layer is distinctive in containing glass-coated crustal xenoliths. The fifth phase produced a small cinder cone containing discrete lapilli layers that records changes from strombolian to phreatomagmatic activity, reflecting waxing and waning of the water table. The last (6th) eruptive phase was more passive, yielding locally thick (>20m) degassed lava flows. A basal welded ash horizon is locally preserved

  10. A neural network model for the automatic detection and forecast of convective cells based on meteosat second generation data

    NASA Astrophysics Data System (ADS)

    Puca, S.; de Leonibus, L.; Zauli, F.; Rosci, P.; Musmanno, L.

    The Mesoscale Convective Systems (MCSs) are often correlated with heavy rainfall, thunderstorms and hail showers, frequently causing significant damages. The most intensive weather activities occur during the maturing stage of the development, which can be found in the case of a multi-cell storm in the centre of the convective complex systems. These convective systems may occur in several different unstable air mass; in a cold air mass behind a polar cold front, in the frontal zone of a polar front and in warm air ahead of a polar warm front. To understand the meteorological situation and apply the best conceptual model, the knowledge of the convective cluster is often not enough. In many cases the forecasters need to know the distribution of the convective cells in the cloudy cluster. A model, running in operational mode at the Italian Air Force Meteorological Service (UGM/CNMCA), for the automatic detection and forecast of the convective cells, is here proposed. The application relays on the Meteosat Second Generation infrared (IR) windows (10.8 μ m, 7.3 μ m) and the two water vapour (WV) channels (6.2 μ m and 7.3 μ m), giving as output the detection of the convective cells and their evolution for the next 15 and 30 minutes. The format of the output of the product is the last IR (10.8 μ m) image where the detected cells, their development and their tracking are represented. This multispectral method, based on a variable threshold method during the detection phase and a neural network algorithm during the forecast phase, allowed us to define a model able to detect the convective cells present in a convective cluster, plot their distribution and forecast the evolution of them for the next 15 and 30 minutes with a good efficiency. For analysing the performance of the model with the Meteosat Second Generation data, different error functions have been evaluated for various meteorological cloud contexts (i.e. high layer and cirrus clouds). Some methods for

  11. Spherical-shell boundaries for two-dimensional compressible convection in a star

    NASA Astrophysics Data System (ADS)

    Pratt, J.; Baraffe, I.; Goffrey, T.; Geroux, C.; Viallet, M.; Folini, D.; Constantino, T.; Popov, M.; Walder, R.

    2016-10-01

    Context. Studies of stellar convection typically use a spherical-shell geometry. The radial extent of the shell and the boundary conditions applied are based on the model of the star investigated. We study the impact of different two-dimensional spherical shells on compressible convection. Realistic profiles for density and temperature from an established one-dimensional stellar evolution code are used to produce a model of a large stellar convection zone representative of a young low-mass star, like our sun at 106 years of age. Aims: We analyze how the radial extent of the spherical shell changes the convective dynamics that result in the deep interior of the young sun model, far from the surface. In the near-surface layers, simple small-scale convection develops from the profiles of temperature and density. A central radiative zone below the convection zone provides a lower boundary on the convection zone. The inclusion of either of these physically distinct layers in the spherical shell can potentially affect the characteristics of deep convection. Methods: We perform hydrodynamic implicit large eddy simulations of compressible convection using the MUltidimensional Stellar Implicit Code (MUSIC). Because MUSIC has been designed to use realistic stellar models produced from one-dimensional stellar evolution calculations, MUSIC simulations are capable of seamlessly modeling a whole star. Simulations in two-dimensional spherical shells that have different radial extents are performed over tens or even hundreds of convective turnover times, permitting the collection of well-converged statistics. Results: To measure the impact of the spherical-shell geometry and our treatment of boundaries, we evaluate basic statistics of the convective turnover time, the convective velocity, and the overshooting layer. These quantities are selected for their relevance to one-dimensional stellar evolution calculations, so that our results are focused toward studies exploiting the so

  12. Testing particle filters on convective scale dynamics

    NASA Astrophysics Data System (ADS)

    Haslehner, Mylene; Craig, George. C.; Janjic, Tijana

    2014-05-01

    Particle filters have been developed in recent years to deal with highly nonlinear dynamics and non Gaussian error statistics that also characterize data assimilation on convective scales. In this work we explore the use of the efficient particle filter (P.v. Leeuwen, 2011) for convective scale data assimilation application. The method is tested in idealized setting, on two stochastic models. The models were designed to reproduce some of the properties of convection, for example the rapid development and decay of convective clouds. The first model is a simple one-dimensional, discrete state birth-death model of clouds (Craig and Würsch, 2012). For this model, the efficient particle filter that includes nudging the variables shows significant improvement compared to Ensemble Kalman Filter and Sequential Importance Resampling (SIR) particle filter. The success of the combination of nudging and resampling, measured as RMS error with respect to the 'true state', is proportional to the nudging intensity. Significantly, even a very weak nudging intensity brings notable improvement over SIR. The second model is a modified version of a stochastic shallow water model (Würsch and Craig 2013), which contains more realistic dynamical characteristics of convective scale phenomena. Using the efficient particle filter and different combination of observations of the three field variables (wind, water 'height' and rain) allows the particle filter to be evaluated in comparison to a regime where only nudging is used. Sensitivity to the properties of the model error covariance is also considered. Finally, criteria are identified under which the efficient particle filter outperforms nudging alone. References: Craig, G. C. and M. Würsch, 2012: The impact of localization and observation averaging for convective-scale data assimilation in a simple stochastic model. Q. J. R. Meteorol. Soc.,139, 515-523. Van Leeuwen, P. J., 2011: Efficient non-linear data assimilation in geophysical

  13. Convective dynamos for rotating stars

    NASA Technical Reports Server (NTRS)

    Gilman, P. A.

    1981-01-01

    Global dynamo theory is applied to the problem of why some stars have field reversing dynamos, and others do not. It is argued that convectively driven dynamos are the most likely source of magnetic fields in stars that have convection zones.

  14. Modeling ocean deep convection

    NASA Astrophysics Data System (ADS)

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

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

  15. Stratiform and Convective Rain Discrimination from Microwave Radiometer Observations

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Cadeddu, M.; Short, D. A.; Weinman, J. A.; Schols, J. L.; Haferman, J.

    1997-01-01

    A criterion based on the SSM/I observations is developed to discriminate rain into convective and stratiform types. This criterion depends on the microwave polarization properties of the flat melting snow particles that fall slowly in the stratiform clouds. Utilizing this criterion and some spatial and temporal characteristics of hydrometeors in TOGA-COARE area revealed by ship borne radars, we have developed an algorithm to retrieve convective and stratiform rain rate from SSM/I data.

  16. Stratiform and Convective Rain Discrimination from Microwave Radiometer Observations

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Cadeddu, M.; Short, D. A.; Weinman, J. A.; Schols, J. L.; Haferman, J.

    1997-01-01

    A criterion based on the SSM/I observations is developed to discriminate rain into convective and stratiform types. This criterion depends on the microwave polarization properties of the flat melting snow particles that fall slowly in the stratiform clouds. Utilizing this criterion and some spatial and temporal characteristics of hydrometeors in TOGA-COARE area revealed by ship borne radars, we have developed an algorithm to retrieve convective and stratiform rain rate from SSM/I data.

  17. Three Dimensional Radiative Transfer In Tropical Deep Convective Clouds.

    NASA Astrophysics Data System (ADS)

    di Giuseppe, F.

    In this study the focus is on the interaction between short-wave radiation with a field of tropical deep convective events generated using a 3D cloud resolving model (CRM) to assess the significance of 3D radiative transport (3DRT). It is not currently un- derstood what magnitude of error is involved when a two stream approximation is used to describe the radiative transfer through such a cloud field. It seems likely that deep convective clouds could be the most complex to represent, and that the error in neglecting horizontal transport could be relevant in these cases. The field here con- sidered has an extention of roughly 90x90 km, approximately equivalent to the grid box dimension of many global models. The 3DRT results are compared both with the calculations obtained by an Independent Pixel Approximation (IPA) approch and by the Plane Parallel radiative scheme (PP) implemented in ECMWF's Forecast model. The differences between the three calculations are used to assess both problems in current GCM's representation of radiative heating and inaccuracies in the dynamical response of CRM simulations due to the Independent Column Approximation (ICA). The understanding of the mechanisms involved in the main 3DRT/1D differences is the starting point for the future attempt to develop a parameterization procedure.

  18. Convection and lunar thermal history

    NASA Technical Reports Server (NTRS)

    Cassen, P.; Reynolds, R. T.; Graziani, F.; Summers, A.; Mcnellis, J.; Blalock, L.

    1979-01-01

    The effects of solid interior convection on the thermal history of the moon are examined. Convective models of lunar evolution are calculated to demonstrate the influence of various viscosities, radioactive heat source distributions and initial temperature profiles and tested by means of a thermal history simulation code. Results indicate that solid convection does not necessarily produce a quasi-steady thermal balance between heat sources and surface losses. The state of the lithosphere is found to be sensitive to the efficiency of heat source redistribution, while that of the convecting interior depends primarily on rheology. Interior viscosities of 10 to the 21st to 10 to the 22nd cm/sec are obtained, along with a central temperature above 1100 C. It is suggested that mare flooding could have been the result of magma production by pressure release melting in the upwelling region of convection cells.

  19. Interactions Between Solidification and Compositional Convection in Alloys

    NASA Technical Reports Server (NTRS)

    Davis, S. H.; Worster, M. G.; Chiareli, A. O. P.; Anderson, D. M.; Schultze, T. P.

    1998-01-01

    This project combined theoretical and experimental ground-based studies of the interactions between convection and solidification of binary melts. Particular attention was focused on the alteration of the composition and microstructure of castings caused by convective flows through the interstices of mushy layers. Two different mechanisms causing convection were investigated. (i) Compositional, buoyancy driven convection is known to cause chimneys and freckles in directionally cast alloys on Earth. The analytical studies provide quantitative criteria for the formation of chimneys that can be used to assess the expediency of producing alloys in Space. (ii) Flow of the melt is also driven by the contraction (expansion) that typically occurs during change of phase. Such convection will occur even in the absence of gravity, and may indeed be the primary cause of macrosegregation during the production of alloys in Space. The studies will employed asymptotic methods in order to determine conditions for the stability of various states of solidifying systems. Further, simple macroscopic models of complete systems were developed and solved. These analytical studies were augmented by laboratory experiments using aqueous solutions, in which the convective flows could be easily observed and the effects of convection could be readily measured. These y experiments guided the development of the theoretical models and provided data against which the predictions of the models can be tested.

  20. The Convective and Orographically Induced Precipitation Study (COPS): The Scientific Strategy, the Field Phase, and Research Highlights

    SciTech Connect

    Wulfmeyer, Volker; Behrendt, Andreas; Kottmeir, Christoph; Corsmeier, Ulrich; Barthlott, Christian; Craig, George C.; Hagen, Martin; Althausen, Dietrich; Aoshima, Fumiko; Arpagaus, Marco; Bauer, Hans-Stefan; Bennett, Lindsay; Blyth, Alan; Brandau, Christine; Champollion, Cedric; Crewell, Susanne; Dick, Galina; di Girolamo, Paolo; Dorninger, Manfred; Dufournet, Yann; Eigenmann, Rafael; Engelmann, Ronny; Flamant, C.; Foken, Thomas; Gorgas, Theresa; Grzeschik, Matthias; Handwerker, Jan; Hauck, Christian; Holler, Hartmut; Junkermann, W.; Kalthoff, Norbert; Kiemle, Christoph; Klink, Stefan; Konig, Marianne; Krauss, Liane; Long, Charles N.; Madonna, Fabio; Mobbs, S.; Neininger, Bruno; Pal, Sandip; Peters, Gerhard; Pigeon, Gregoire; Richard, Evelyne; Rotach, Mathias W.; Russchenberg, Herman; Schwitalla, Thomas; Smith, Victoria; Steinacker, Reinhold; Trentman, Jorg; Turner, David D.; van Baelen, Joel; Vogt, Siegfried; Volkert, Hans; Weckwerth, Tammy; Wernli, Heini; Wieser, Andreas; Wirth, Martin

    2011-02-24

    Within the frame of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. The COPS field phase was performed from 01 June - 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges Mountains, the Rhine valley and the Black Forest Mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase up to their decay. 18 Intensive Operation Periods (IOPs) with 34 operation days and 8 additional Special Observation Periods (SOPs) were performed providing a comprehensive data set covering different forcing conditions. In this paper an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Some highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS provided new insight in key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of QPF by the assimilation of new observations, and in the performance of ensembles of convection permitting models in complex terrain.

  1. Heat Transfer and Convective Structure of Evaporating Films under Pressure-Modulated Conditions

    NASA Astrophysics Data System (ADS)

    Gonzalez, Juan Carlos

    This work examines the fluid mechanical and heat transfer characteristics of evaporating films under cyclical superheat conditions. This research was motivated by the need to further understand the instability drivers in films undergoing unsteady and cyclical evaporation. The superheat was controlled modulating the system pressure. An isolated test cell allowed the films to evaporate into their own vapor without non-condensable present. A non-intrusive thickness measurement technique was used to yield dynamic heat flux measurements. A double pass schlieren system was employed to capture convective structures. System temperature and pressure measurements completed the diagnostics. The primary conclusions are briefly summarized as follows: • The evolution of thermal profile within evaporating films has a strong impact on the development of convective structure and heat transfer. In some cases convective structure appears within the film under pressure-modulated conditions even when the evaporation intervals are sufficiently short that conduction is expected to be the only heat transfer mode within the film. • Convective structure appears to persist in many cases even after evaporation is stopped. • Stopping the evaporation for short time intervals appears to have a negligible effect on the temperature profile in the film based on the subsequent evaporation behavior. • Complex, multi-wavelength convective structure behavior can be induced through cyclical superheating of the films. • A modest gain in short-term heat flux is achievable under some pressure-modulated conditions. • Surface instabilities of quasi-steady evaporating films do not lead to an increase in the evaporation rate. • Reduced gravity tests were seriously compromised by unsteady g-levels and g-jitter.

  2. Realistic numerical simulations of solar convection: emerging flux, pores, and Stokes spectra

    NASA Astrophysics Data System (ADS)

    Georgobiani, D.; Stein, R.; Nordlund, A.

    2012-12-01

    We report on magneto-convection simulations of magnetic flux emerging through the upper layers of the solar convection zone into the photosphere. Simulations by Georgobiani, Stein and Nordlund start from minimally structured, uniform, untwisted horizontal field advected into the computational domain by supergranule scale inflows at 20 Mm depth. At the opposite extreme, simulations by Cheung (2007, 2008, 2011) start with a coherent flux tube inserted into or forced into the bottom of the computational domain. Several robust results have emerged from the comparison of results from these two very different initial states. First, rising magnetic flux gets deformed into undulating, serpentine shapes by the influence of the convective up- and down-flows. The flux develops fine structure and appears at the surface first as a "pepper and salt" pattern of mixed polarity. Where magnetic flux approaches the surface, granules become darker and elongated in the direction of the field. Subsequently, the underlying large scale magnetic structures make the field collect into unipolar regions. Magneto-convection produces a complex, small-scale magnetic field topology, whatever the initial state. A heirarchy of magnetic loops corresponding to the different scales of convective motions are produced. Vertical vortex tubes form at intergranule lane vertices which can lead to tornado-like magnetic fields in the photosphere. Gradients in field strength and velocity produce asymmetric Stokes spectra. Where emerging Omega loops leave behind nearly vertical legs, long lived pores can spontaneously form. The field in the pores first becomes concentrated and evacuated near the surface and the evacuated flux concentration then extends downward.

  3. Complexity, Chaos, and Nonlinear Dynamics: A New Perspective on Career Development Theory

    ERIC Educational Resources Information Center

    Bloch, Deborah P.

    2005-01-01

    The author presents a theory of career development drawing on nonlinear dynamics and chaos and complexity theories. Career is presented as a complex adaptive entity, a fractal of the human entity. Characteristics of complex adaptive entities, including (a) autopiesis, or self-regeneration; (b) open exchange; (c) participation in networks; (d)…

  4. Complexity, Chaos, and Nonlinear Dynamics: A New Perspective on Career Development Theory

    ERIC Educational Resources Information Center

    Bloch, Deborah P.

    2005-01-01

    The author presents a theory of career development drawing on nonlinear dynamics and chaos and complexity theories. Career is presented as a complex adaptive entity, a fractal of the human entity. Characteristics of complex adaptive entities, including (a) autopiesis, or self-regeneration; (b) open exchange; (c) participation in networks; (d)…

  5. A Cross-Linguistic Perspective on Syntactic Complexity in L2 Development: Syntactic Elaboration and Diversity

    ERIC Educational Resources Information Center

    De Clercq, Bastien; Housen, Alex

    2017-01-01

    Syntactic and linguistic complexity have been studied extensively in applied linguistics as indicators of linguistic performance, development, and proficiency. Recent publications have equally highlighted the reductionist approach taken to syntactic complexity measurement, which often focuses on one or two measures representing complexity at the…

  6. Temperature-Driven Convection

    NASA Astrophysics Data System (ADS)

    Bohan, Richard J.; Vandegrift, Guy

    2003-02-01

    Warm air aloft is stable. This explains the lack of strong winds in a warm front and how nighttime radiative cooling can lead to motionless air that can trap smog. The stability of stratospheric air can be attributed to the fact that it is heated from above as ultraviolet radiation strikes the ozone layer. On the other hand, fluid heated from below is unstable and can lead to Bernard convection cells. This explains the generally turbulent nature of the troposphere, which receives a significant fraction of its heat directly from the Earth's warmer surface. The instability of cold fluid aloft explains the violent nature of a cold front, as well as the motion of Earth's magma, which is driven by radioactive heating deep within the Earth's mantle. This paper describes how both effects can be demonstrated using four standard beakers, ice, and a bit of food coloring.

  7. CFD simulation of the effect of particle size on the nanofluids convective heat transfer in the developed region in a circular tube.

    PubMed

    Davarnejad, Reza; Barati, Sara; Kooshki, Maryam

    2013-12-01

    The CFD simulation of heat transfer characteristics of a nanofluid in a circular tube under constant heat flux was considered using Fluent software (version 6.3.26) in the laminar flow. Al2O3 nanoparticles in water with concentrations of 0.5%, 1.0%, 1.5%, 2% and 2.5% were used in this simulation. All of the thermo-physical properties of nanofluids were assumed to be temperature independent. Two particle sizes with average size of 20 and 50 nm were used in this research. It was concluded that heat transfer coefficient increased by increasing the Reynolds number and the concentration of nanoparticles. The maximum convective heat transfer coefficient was observed at the highest concentration of nano-particles in water (2.5%). Furthermore, the two nanofluids showed higher heat transfer than the base fluid (water) although the nanofluid with particles size of 20 nm had the highest heat transfer coefficient.

  8. Some Consequences of Thermosolutal Convection: The Grain Structure of Castings

    NASA Technical Reports Server (NTRS)

    Hansen, G.; Hellawell, A.; Lu, S. Z.; Steube, R. S.

    1996-01-01

    The essential principles of thermosolutal convection are outlined, and how convection provides a transport mechanism between the mushy region of a casting and the open bulk liquid is illustrated. The convective flow patterns which develop assist in heat exchange and macroscopic solute segregation during solidification; they also provide a mechanism for the transport of dendritic fragments from the mushy region into the bulk liquid. Surviving fragments become nuclei for equiaxed grains and so lead to blocking of the parental columnar, dendritic growth front from which they originated. The physical steps in such a sequence are considered and some experimental data are provided to support the argument.

  9. Convection surrounding mesoscale ionospheric flow channels

    NASA Astrophysics Data System (ADS)

    Rinne, Y.; Moen, J.; Baker, J. B. H.; Carlson, H. C.

    2011-05-01

    We evaluate data from the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and Defense Meteorological Satellite Program (DMSP) spacecraft coupled with data from the Super Dual Auroral Radar Network (SuperDARN) polar cap convection patterns in order to study how the ionospheric convection evolves around a sequence of transient, mesoscale flow channel events in the duskside of the cusp inflow region. On a northwestward convection background for the interplanetary magnetic field (IMF) BY positive and BZ negative, a sequence of three eastward flow channels formed over the course of 1 hour in response to three sharp IMF rotations to IMF BY negative and IMF BZ positive. The first and third channels, due to IMF BY negative periods of ˜13 min and >30 min, respectively, develop in a similar manner: they span the entire ESR field of view and widen poleward with increasing time elapsed since their first appearance until the IMF rotates back. The convection patterns are consistent with the line-of-sight data from the ESR and DMSP within a 10 min adaption time. The flow lines form a twin-vortex flow, with the observed channel being the twin vortices' center flow. The fitting algorithm was pushed to its limits in terms of spatial resolution in this study. During portions of the channel events, the suggested twin-cell flow is not in agreement with our physical interpretation of the flow channels being reconnection events because cell closure is suggested across an anticipated nonreconnecting open-closed boundary. For these segments, we present simulated patterns which have been arrived at by a combination of looking at the raw data and examining the fitted convection patterns.

  10. Observing Complex Systems Thinking in the Zone of Proximal Development

    ERIC Educational Resources Information Center

    Danish, Joshua; Saleh, Asmalina; Andrade, Alejandro; Bryan, Branden

    2017-01-01

    Our paper builds on the construct of the zone of proximal development (ZPD) (Vygotsky in Mind in society: the development of higher psychological processes, Harvard University Press, Cambridge, 1978) to analyze the relationship between students' answers and the help they receive as they construct them. We report on a secondary analysis of…

  11. Complexities of Organization Dynamics and Development: Leaders and Managers

    ERIC Educational Resources Information Center

    Nderu-Boddington, Eulalee

    2008-01-01

    This article shows the theoretical framework for understanding organizational dynamics and development - the change theory and subordinate relationships within contemporary organizations. The emphasis is on power strategies and the relationship to organizational dynamics and development. The integrative process broadens the understanding of…

  12. Scale-free convection theory

    NASA Astrophysics Data System (ADS)

    Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.

    2015-08-01

    Convection is one of the fundamental mechanism to transport energy, e.g., in planetology, oceanography as well as in astrophysics where stellar structure customarily described by the mixing-length theory, which makes use of the mixing-length scale parameter to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height of the star, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun.No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in literature are hampered by this basic uncertainty.In a recent paper (Pasetto et al 2014) we presented the first fully analytical scale-free theory of convection that does not require the mixing-length parameter. Our self-consistent analytical formulation of convection determines all the properties of convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium (being it a either a star, an ocean, a primordial planet). The new theory of convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism.We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory in astrophysical environment are compared with those from the standard mixing-length paradigm in stars with

  13. Scale-free convection theory

    NASA Astrophysics Data System (ADS)

    Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.

    Convection is one of the fundamental mechanisms to transport energy, e.g., in planetology, oceanography, as well as in astrophysics where stellar structure is customarily described by the mixing-length theory, which makes use of the mixing-length scale parameter to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height of the star, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun. No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in the literature are hampered by this basic uncertainty. In a recent paper (Pasetto et al. 2014) we presented the first fully analytical scale-free theory of convection that does not require the mixing-length parameter. Our self-consistent analytical formulation of convection determines all the properties of convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium (be it a star, an ocean, or a primordial planet). The new theory of convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism. We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory in astrophysical environment are compared with those from the standard mixing-length paradigm in stars with

  14. Renal development: a complex process dependent on inductive interaction.

    PubMed

    Upadhyay, Kiran K; Silverstein, Douglas M

    2014-01-01

    Renal development begins in-utero and continues throughout childhood. Almost one-third of all developmental anomalies include structural or functional abnormalities of the urinary tract. There are three main phases of in-utero renal development: Pronephros, Mesonephros and Metanephros. Within three weeks of gestation, paired pronephri appear. A series of tubules called nephrotomes fuse with the pronephric duct. The pronephros elongates and induces the nearby mesoderm, forming the mesonephric (Woffian) duct. The metanephros is the precursor of the mature kidney that originates from the ureteric bud and the metanephric mesoderm (blastema) by 5 weeks of gestation. The interaction between these two components is a reciprocal process, resulting in the formation of a mature kidney. The ureteric bud forms the major and minor calyces, and the collecting tubules while the metanephrogenic blastema develops into the renal tubules and glomeruli. In humans, all of the nephrons are formed by 32 to 36 weeks of gestation. Simultaneously, the lower urinary tract develops from the vesico urethral canal, ureteric bud and mesonephric duct. In utero, ureters deliver urine from the kidney to the bladder, thereby creating amniotic fluid. Transcription factors, extracellular matrix glycoproteins, signaling molecules and receptors are the key players in normal renal development. Many medications (e.g., aminoglycosides, cyclooxygenase inhibitors, substances that affect the renin-angiotensin aldosterone system) also impact renal development by altering the expression of growth factors, matrix regulators or receptors. Thus, tight regulation and coordinated processes are crucial for normal renal development.

  15. New Developments in Understanding the Complexity of Human Speech Production.

    PubMed

    Simonyan, Kristina; Ackermann, Hermann; Chang, Edward F; Greenlee, Jeremy D

    2016-11-09

    Speech is one of the most unique features of human communication. Our ability to articulate our thoughts by means of speech production depends critically on the integrity of the motor cortex. Long thought to be a low-order brain region, exciting work in the past years is overturning this notion. Here, we highlight some of major experimental advances in speech motor control research and discuss the emerging findings about the complexity of speech motocortical organization and its large-scale networks. This review summarizes the talks presented at a symposium at the Annual Meeting of the Society of Neuroscience; it does not represent a comprehensive review of contemporary literature in the broader field of speech motor control. Copyright © 2016 the authors 0270-6474/16/3611440-09$15.00/0.

  16. New Developments in Understanding the Complexity of Human Speech Production

    PubMed Central

    Ackermann, Hermann; Chang, Edward F.; Greenlee, Jeremy D.

    2016-01-01

    Speech is one of the most unique features of human communication. Our ability to articulate our thoughts by means of speech production depends critically on the integrity of the motor cortex. Long thought to be a low-order brain region, exciting work in the past years is overturning this notion. Here, we highlight some of major experimental advances in speech motor control research and discuss the emerging findings about the complexity of speech motocortical organization and its large-scale networks. This review summarizes the talks presented at a symposium at the Annual Meeting of the Society of Neuroscience; it does not represent a comprehensive review of contemporary literature in the broader field of speech motor control. PMID:27911747

  17. A coarse grained stochastic particle interacting system for tropical convection

    NASA Astrophysics Data System (ADS)

    Khouider, B.

    2012-12-01

    Climate models (GCMs) fail to represent adequately the variability associated with organized convection in the tropics. This deficiency is believed to hinder medium and long range weather forecasts, over weeks to months. GCMs use very complex sub-grid models, known as cumulus parameterizations, to represent the effects of clouds and convection as well as other unresolved processes. Cumulus parameterizations are intrinsically deterministic and are typically based on the quasi-equilibrium theory, which assumes that convection instantaneously consumes the atmospheric instability produced by radiation. In this talk, I will discuss a stochastic model for organized tropical convection based on a particle interacting system defined on a microscopic lattice. An order parameter is assumed to take the values 0,1,2,3 at a any given lattice site according to whether it is a clear site or it is occupied by a cloud of a one of the three types: congestus, deep, or stratiform, following intuitive rules motivated by recent satellite observations and various field campaigns conducted over the Indian Ocean and Western Pacific. The microscopic Markov process is coarse-grained systematically to obtain a multidimensional birth-death process with immigration, following earlier work done by Katsoulakis, Majda, and Vlachos (JCP 2003) for the case of the Ising model where the order parameter takes the values 0 and 1. The coarse grained birth-death process is a stochastic model, intermediate between the microscopic lattice model and the deterministic mean field limit, that is used to represent the sub-grid scale variability of the underlying physical process (here the cloud cover) with a negligible computational overhead and yet permits both local interactions between lattice sites and two-way interactions between the cloud cover and the large-scale climate dynamics. The new systematic coarse-graining, developed here for the multivalued order parameter, provides a unifying framework

  18. Task structure complexity and goal neglect in typically developing children.

    PubMed

    Roberts, Gareth; Anderson, Mike

    2014-04-01

    Goal neglect is a failure to enact task requirements despite being able to accurately report them. In this study, we introduce a new child-appropriate experimental paradigm to measure goal neglect in children between 7 and 11 years of age and test the hypothesis that the complexity of an action plan, not real-time trial demands, increases goal neglect. A total of 66 children (Mage=9.50 years) were administered a Feature Match task. Half of the children were given four rules for matching, and half were given three rules for matching. After practice, the four-rules group was told to ignore the additional rule, and both groups completed an identical three-rules task. The results showed that the extra rule increased goal neglect and its correlation with fluid intelligence. Although intermittent trial errors were correlated with fluid intelligence for both groups, only in the four-rules group were systematic rule failures (i.e., goal neglect) correlated with fluid intelligence. Task performance improved with chronological age; however, when controlling for the influence of fluid intelligence, the relationship between age and task performance was effectively removed. This suggests that a child's current level of fluid intelligence (and not age) determines task performance. We suggest that the relationship among goal neglect, complex task instructions, and fluid intelligence is linked to the mental preparation for future events, that is, mentally compiling verbal instructions into a set of activated goal representations in working memory that represent what is to be done and under what circumstances.

  19. New layer thickness parameterization of diffusive convection in the ocean

    NASA Astrophysics Data System (ADS)

    Zhou, Sheng-Qi; Lu, Yuan-Zheng; Song, Xue-Long; Fer, Ilker

    2016-03-01

    In the present study, a new parameterization is proposed to describe the convecting layer thickness in diffusive convection. By using in situ observational data of diffusive convection in the lakes and oceans, a wide range of stratification and buoyancy flux is obtained, where the buoyancy frequency N varies between 10-4 and 0.1 s-1 and the heat-related buoyancy flux qT varies between 10-12 and 10-7 m2 s-3. We construct an intrinsic thickness scale, H0 =[qT3 / (κTN8) ] 1 / 4, here κT is the thermal diffusivity. H0 is suggested to be the scale of an energy-containing eddy and it can be alternatively represented as H0 = ηRebPr1/4, here η is the dissipation length scale, Reb is the buoyant Reynolds number, and Pr is the Prandtl number. It is found that the convective layer thickness H is directly linked to the stability ratio Rρ and H0 with the form of H ∼ (Rρ - 1)2H0. The layer thickness can be explained by the convective instability mechanism. To each convective layer, its thickness H reaches a stable value when its thermal boundary layer develops to be a new convecting layer.

  20. Quasi-three-dimensional simulations of deep convection

    SciTech Connect

    Hertenstein, R.F.A.; Cotton, W.R.; Weissbluth, M.J.

    1991-01-01

    Simulations of deep convection along the Florida sea-breeze front have previously been carried out in two dimensions using the Colorado State University Regional Atmospheric Modeling System. These experiments were in good agreement with observations, capturing the propagation of the sea-breeze fronts and the associated convection as well as the eventual collision of the two sea-breeze fronts from opposite shores, leading to more fully developed deep convection. We have extended this simulation by adding enough points in the third dimension to capture the three-dimensional convective cells. We have two goals with this work. First we will use this experiment as a step towards fully three-dimensional simulations of Mesoscale Convective Systems in which interactive-grid nests are used to explicitly simulate convective processes. A second goal is to use the results of these simulations as a synthetic data set. We can then run simulations of the same case using a convective parameterization scheme, compare the results of the parameterization run to the synthetic data set, and use diagnostic analyses to refine the parameterization scheme. 2 refs.

  1. Quasi-three-dimensional simulations of deep convection

    SciTech Connect

    Hertenstein, R.F.A.; Cotton, W.R.; Weissbluth, M.J.

    1991-12-31

    Simulations of deep convection along the Florida sea-breeze front have previously been carried out in two dimensions using the Colorado State University Regional Atmospheric Modeling System. These experiments were in good agreement with observations, capturing the propagation of the sea-breeze fronts and the associated convection as well as the eventual collision of the two sea-breeze fronts from opposite shores, leading to more fully developed deep convection. We have extended this simulation by adding enough points in the third dimension to capture the three-dimensional convective cells. We have two goals with this work. First we will use this experiment as a step towards fully three-dimensional simulations of Mesoscale Convective Systems in which interactive-grid nests are used to explicitly simulate convective processes. A second goal is to use the results of these simulations as a synthetic data set. We can then run simulations of the same case using a convective parameterization scheme, compare the results of the parameterization run to the synthetic data set, and use diagnostic analyses to refine the parameterization scheme. 2 refs.

  2. The influence of convective activity on the vorticity budget

    NASA Technical Reports Server (NTRS)

    Townsend, T. L.; Scoggins, J. R.

    1983-01-01

    The influence of convective activity on the vorticity budget was determined during the AVE VII and AVE-SESAME I periods. This was accomplished by evaluating each term in the expanded vorticity equation with twisting and tilting and friction representing the residual of all other terms. Convective areas were delineated by use of radar summary charts. The influence of convective activity was established by analyzing contoured fields of each term as well as numerical values and profiles of the various terms in convective and nonconvective areas. Vertical motion was computed by the kinematic method, and all computations were performed over the central United States using a grid spacing of 158 km. The results show that, in convective areas in particular, the residual is of comparable magnitude to the horizontal advection and divergence terms, and therefore, cannot be neglected. In convective areas, the residual term represents a sink of vorticity below 500 mb and a strong source near 300 mb. In nonconvective areas, the residual was small in magnitude at all levels, but tended to be negative (vorticity sink) at 300 mb. The local change term, over convective areas, tended to be balanced by the residual term, and appeared to be a good indicator of development (vorticity becoming more cyclonic). Finally, the shape of the vertical profiles of the term in the budget equation agreed with those found by other investigators for easterly waves, but the terms were one order of magnitude larger than those for easterly waves.

  3. Convective cloud fields in the Atlantic sector of the Arctic: Satellite and ground-based observations

    NASA Astrophysics Data System (ADS)

    Esau, I. N.; Chernokulsky, A. V.

    2015-12-01

    Convective cloudiness in the Atlantic sector of the Arctic is considered as an atmospheric spatially self-organized convective field. Convective cloud development is usually studied as a local process reflecting the convective instability of the turbulent planetary boundary layer over a heated surface. The convective cloudiness has a different dynamical structure in high latitudes. Cloud development follows cold-air outbreaks into the areas with a relatively warm surface. As a result, the physical and morphological characteristics of clouds, such as the type of convective cloud, and their geographical localization are interrelated. It has been shown that marginal sea ice and coastal zones are the most frequently occupied by Cu hum, Cu med convective clouds, which are organized in convective rolls. Simultaneously, the open water marine areas are occupied by Cu cong, Cb, which are organized in convective cells. An intercomparison of cloud statistics using satellite data ISCCP and ground-based observations has revealed an inconsistency in the cloudiness trends in these data sources: convective cloudiness decreases in ISCCP data and increases in the groundbased observation data. In general, according to the stated hypothesis, the retreat of the sea-ice boundary may lead to an increase in the amount of convective clouds.

  4. Effects of Moist Convection on Hurricane Predictability

    NASA Technical Reports Server (NTRS)

    Zhang, Fuqing; Sippel, Jason A.

    2008-01-01

    This study exemplifies inherent uncertainties in deterministic prediction of hurricane formation and intensity. Such uncertainties could ultimately limit the predictability of hurricanes at all time scales. In particular, this study highlights the predictability limit due to the effects on moist convection of initial-condition errors with amplitudes far smaller than those of any observation or analysis system. Not only can small and arguably unobservable differences in the initial conditions result in different routes to tropical cyclogenesis, but they can also determine whether or not a tropical disturbance will significantly develop. The details of how the initial vortex is built can depend on chaotic interactions of mesoscale features, such as cold pools from moist convection, whose timing and placement may significantly vary with minute initial differences. Inherent uncertainties in hurricane forecasts illustrate the need for developing advanced ensemble prediction systems to provide event-dependent probabilistic forecasts and risk assessment.

  5. Leo Kadanoff's legacy for turbulent thermal convection

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef

    Rayleigh-Benard (RB) convection -- the buoyancy-driven flow of a fluid heated from below and cooled from above -- is a classical problem in fluid dynamics. It played a crucial role in the development of stability theory in hydrodynamics (Rayleigh, Chandrasekhar) and had been paradigmatic in pattern formation and in the study of spatial-temporal chaos (Ahlers, Libchaber, and many other). It was Leo Kadanoff and his associates in Chicago who, in the 1980s and 1990s, propagated the RB system as paradigmatic for the physics of fully developed turbulence and contributed tremendously to today's understanding of thermally driven turbulence. He and his experimental coworkers (Libchaber et al.) revealed the importance of the thermal plumes and the large-scale wind, and elucidated the interplay between thermal boundary layers and bulk. His scaling analysis laid the basis for our present understanding of turbulent convection, which I will review in this talk, highlighting Leo's trailblazing contributions. Kadanoff session.

  6. Energy analysis of convectively induced wind perturbations

    NASA Technical Reports Server (NTRS)

    Fuelberg, Henry E.; Buechler, Dennis E.

    1989-01-01

    Budgets of divergent and rotational components of kinetic energy (KD and KR) are examined for four upper level wind speed maxima that develop during the fourth Atmospheric Variability Experiment (AVE IV) and the first AVE-Severe Environmental Storms and Mesoscale Experiment (AVE-SESAME I). A similar budget analysis is performed for a low-level jet stream during AVE-SESAME I. The energetics of the four upper level speed maxima is found to have several similarities. The dominant source of KD is cross-contour flow by the divergent wind, and KD provides a major source of KR via a conversion process. Conversion from available potential energy provides an additional source of KR in three of the cases. Horizontal maps reveal that the conversions involving KD are maximized in regions poleward of the convection. Low-level jet development during AVE-SESAME I appears to be assisted by convective activity to the west.

  7. Effects of Moist Convection on Hurricane Predictability

    NASA Technical Reports Server (NTRS)

    Zhang, Fuqing; Sippel, Jason A.

    2008-01-01

    This study exemplifies inherent uncertainties in deterministic prediction of hurricane formation and intensity. Such uncertainties could ultimately limit the predictability of hurricanes at all time scales. In particular, this study highlights the predictability limit due to the effects on moist convection of initial-condition errors with amplitudes far smaller than those of any observation or analysis system. Not only can small and arguably unobservable differences in the initial conditions result in different routes to tropical cyclogenesis, but they can also determine whether or not a tropical disturbance will significantly develop. The details of how the initial vortex is built can depend on chaotic interactions of mesoscale features, such as cold pools from moist convection, whose timing and placement may significantly vary with minute initial differences. Inherent uncertainties in hurricane forecasts illustrate the need for developing advanced ensemble prediction systems to provide event-dependent probabilistic forecasts and risk assessment.

  8. Effects of natural convection on thermal explosion in a closed vessel.

    PubMed

    Liu, Ting-Yueh; Campbell, Alasdair N; Cardoso, Silvana S S; Hayhurst, Allan N

    2008-09-28

    A new way of ascertaining whether or not a reacting mixture will explode uses just three timescales: that for chemical reaction to heat up the fluid containing the reactants and products, the timescale for heat conduction out of the reactor, and the timescale for natural convection in the fluid. This approach is developed for an nth order chemical reaction, A --> B occurring exothermically in a spherical, batch reactor without significant consumption of A. The three timescales are expressed in terms of the physical and chemical parameters of the system. Numerical simulations are performed for laminar natural convection occurring; also, a theoretical relation is developed for turbulent flow. These theoretical and numerical results agree well with previous experimental measurements for the decomposition of azomethane in the gas phase. The new theory developed here is compared with Frank-Kamenetskii's classical criterion for explosion. This new treatment has the advantage of separating the two effects inhibiting explosion, viz. heat removal by thermal conduction and by natural convection. Also, the approach is easily generalised to more complex reactions and flow systems.

  9. Convection in Type 2 supernovae

    SciTech Connect

    Miller, Douglas Scott

    1993-10-15

    Results are presented here from several two dimensional numerical calculations of events in Type II supernovae. A new 2-D hydrodynamics and neutrino transport code has been used to compute the effect on the supernova explosion mechanism of convection between the neutrinosphere and the shock. This convection is referred to as exterior convection to distinguish it from convection beneath the neutrinosphere. The model equations and initial and boundary conditions are presented along with the simulation results. The 2-D code was used to compute an exterior convective velocity to compare with the convective model of the Mayle and Wilson 1-D code. Results are presented from several runs with varying sizes of initial perturbation, as well as a case with no initial perturbation but including the effects of rotation. The M&W code does not produce an explosion using the 2-D convective velocity. Exterior convection enhances the outward propagation of the shock, but not enough to ensure a successful explosion. Analytic estimates of the growth rate of the neutron finger instability axe presented. It is shown that this instability can occur beneath the neutrinosphere of the proto-neutron star in a supernova explosion with a growth time of ~ 3 microseconds. The behavior of the high entropy bubble that forms between the shock and the neutrinosphere in one dimensional calculations of supernova is investigated. It has been speculated that this bubble is a site for γ-process generation of heavy elements. Two dimensional calculations are presented of the time evolution of the hot bubble and the surrounding stellar material. Unlike one dimensional calculations, the 2D code fails to achieve high entropies in the bubble. When run in a spherically symmetric mode the 2-D code reaches entropies of ~ 200. When convection is allowed, the bubble reaches ~60 then the bubble begins to move upward into the cooler, denser material above it.

  10. TURBULENT CONVECTION MODEL IN THE OVERSHOOTING REGION. II. THEORETICAL ANALYSIS

    SciTech Connect

    Zhang, Q. S.; Li, Y. E-mail: ly@ynao.ac.cn

    2012-05-01

    Turbulent convection models (TCMs) are thought to be good tools to deal with the convective overshooting in the stellar interior. However, they are too complex to be applied to calculations of stellar structure and evolution. In order to understand the physical processes of the convective overshooting and to simplify the application of TCMs, a semi-analytic solution is necessary. We obtain the approximate solution and asymptotic solution of the TCM in the overshooting region, and find some important properties of the convective overshooting. (1) The overshooting region can be partitioned into three parts: a thin region just outside the convective boundary with high efficiency of turbulent heat transfer, a power-law dissipation region of turbulent kinetic energy in the middle, and a thermal dissipation area with rapidly decreasing turbulent kinetic energy. The decaying indices of the turbulent correlations k, u{sub r}'T'-bar, and T'T'-bar are only determined by the parameters of the TCM, and there is an equilibrium value of the anisotropic degree {omega}. (2) The overshooting length of the turbulent heat flux u{sub r}'T'-bar is about 1H{sub k} (H{sub k} = |dr/dln k|). (3) The value of the turbulent kinetic energy at the convective boundary k{sub C} can be estimated by a method called the maximum of diffusion. Turbulent correlations in the overshooting region can be estimated by using k{sub C} and exponentially decreasing functions with the decaying indices.

  11. AN ANALYTIC RADIATIVE-CONVECTIVE MODEL FOR PLANETARY ATMOSPHERES

    SciTech Connect

    Robinson, Tyler D.; Catling, David C.

    2012-09-20

    We present an analytic one-dimensional radiative-convective model of the thermal structure of planetary atmospheres. Our model assumes that thermal radiative transfer is gray and can be represented by the two-stream approximation. Model atmospheres are assumed to be in hydrostatic equilibrium, with a power-law scaling between the atmospheric pressure and the gray thermal optical depth. The convective portions of our models are taken to follow adiabats that account for condensation of volatiles through a scaling parameter to the dry adiabat. By combining these assumptions, we produce simple, analytic expressions that allow calculations of the atmospheric-pressure-temperature profile, as well as expressions for the profiles of thermal radiative flux and convective flux. We explore the general behaviors of our model. These investigations encompass (1) worlds where atmospheric attenuation of sunlight is weak, which we show tend to have relatively high radiative-convective boundaries; (2) worlds with some attenuation of sunlight throughout the atmosphere, which we show can produce either shallow or deep radiative-convective boundaries, depending on the strength of sunlight attenuation; and (3) strongly irradiated giant planets (including hot Jupiters), where we explore the conditions under which these worlds acquire detached convective regions in their mid-tropospheres. Finally, we validate our model and demonstrate its utility through comparisons to the average observed thermal structure of Venus, Jupiter, and Titan, and by comparing computed flux profiles to more complex models.

  12. On global gravity anomalies and two-scale mantle convection

    NASA Technical Reports Server (NTRS)

    Marsh, B. D.; Marsh, J. G.

    1976-01-01

    The two-scale model of mantle convection developed by Richter and Parsons (1975) predicts that if the depth of the convective layer is about 600 km, then for a plate moving at 10 cm/yr, longitudinal convective rolls will be produced in about 50 million years, and the strike of these rolls indicates the direction of motion of the plate relative to the upper mantle. The paper tests these predictions by examining a new global free air gravity model complete to the 30th degree and order. The free air gravity map developed shows a series of linear positive and negative anomalies (with transverse wavelengths of about 2000 km) spanning the Pacific Ocean, crossing the Pacific rise and striking parallel to the Hawaiian seamounts. It is suggested that the pattern of these anomalies may indicate the presence of longitudinal convective rolls beneath the Pacific plates, a result which tends to support the predictions of Richter and Parsons.

  13. Hindered Convection of Macromolecules in Hydrogels

    PubMed Central

    Kosto, Kimberly B.; Deen, William M.

    2005-01-01

    Hindered convection of macromolecules in gels was studied by measuring the sieving coefficient (Θ) of narrow fractions of Ficoll (Stokes-Einstein radius, rs = 2.7–5.9 nm) in agarose and agarose-dextran membranes, along with the Darcy permeability (κ). To provide a wide range of κ, varying amounts of dextran (volume fractions ≤ 0.011) were covalently attached to agarose gels with volume fractions of 0.040 or 0.080. As expected, Θ decreased with increasing rs or with increasing concentrations of either agarose or dextran. For each molecular size, Θ plotted as a function of κ fell on a single curve for all gel compositions studied. The dependence of Θ on κ and rs was predicted well by a hydrodynamic theory based on flow normal to the axes of equally spaced, parallel fibers. Values of the convective hindrance factor (Kc, the ratio of solute to fluid velocity), calculated from Θ and previous equilibrium partitioning data, were unexpectedly large; although Kc ≤ 1.1 in the fiber theory, its apparent value ranged generally from 1.5 to 3. This seemingly anomalous result was explained on the basis of membrane heterogeneity. Convective hindrances in the synthetic gels were quite similar to those in glomerular basement membrane, when compared on the basis of similar solid volume fractions and values of κ. Overall, the results suggest that convective hindrances can be predicted fairly well from a knowledge of κ, even in synthetic or biological gels of complex composition. PMID:15516521

  14. Developing shape analysis tools to assist complex spatial decision making

    SciTech Connect

    Mackey, H.E.; Ehler, G.B.; Cowen, D.

    1996-05-31

    The objective of this research was to develop and implement a shape identification measure within a geographic information system, specifically one that incorporates analytical modeling for site location planning. The application that was developed incorporated a location model within a raster-based GIS, which helped address critical performance issues for the decision support system. Binary matrices, which approximate the object`s geometrical form, are passed over the grided data structure and allow identification of irregular and regularly shaped objects. Lastly, the issue of shape rotation is addressed and is resolved by constructing unique matrices corresponding to the object`s orientation

  15. Exact finite elements for conduction and convection

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.

    1981-01-01

    An appproach for developing exact one dimensional conduction-convection finite elements is presented. Exact interpolation functions are derived based on solutions to the governing differential equations by employing a nodeless parameter. Exact interpolation functions are presented for combined heat transfer in several solids of different shapes, and for combined heat transfer in a flow passage. Numerical results demonstrate that exact one dimensional elements offer advantages over elements based on approximate interpolation functions. Previously announced in STAR as N81-31507

  16. Exact finite elements for conduction and convection

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.

    1981-01-01

    An appproach for developing exact one dimensional conduction-convection finite elements is presented. Exact interpolation functions are derived based on solutions to the governing differential equations by employing a nodeless parameter. Exact interpolation functions are presented for combined heat transfer in several solids of different shapes, and for combined heat transfer in a flow passage. Numerical results demonstrate that exact one dimensional elements offer advantages over elements based on approximate interpolation functions. Previously announced in STAR as N81-31507

  17. Exact finite elements for conduction and convection

    NASA Technical Reports Server (NTRS)

    Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.

    1981-01-01

    An approach for developing exact one dimensional conduction-convection finite elements is presented. Exact interpolation functions are derived based on solutions to the governing differential equations by employing a nodeless parameter. Exact interpolation functions are presented for combined heat transfer in several solids of different shapes, and for combined heat transfer in a flow passage. Numerical results demonstrate that exact one dimensional elements offer advantages over elements based on approximate interpolation functions.

  18. Dynamic Development of Complexity and Accuracy: A Case Study in Second Language Academic Writing

    ERIC Educational Resources Information Center

    Rosmawati

    2014-01-01

    This paper reports on the development of complexity and accuracy in English as a Second Language (ESL) academic writing. Although research into complexity and accuracy development in second language (L2) writing has been well established, few studies have assumed the multidimensionality of these two constructs (Norris & Ortega, 2009) or…

  19. The Development of Second Language Writing Complexity in Groups and Individuals: A Longitudinal Learner Corpus Study

    ERIC Educational Resources Information Center

    Vyatkina, Nina

    2012-01-01

    This study explores the development of multiple dimensions of linguistic complexity in the writing of beginning learners of German both as a group and as individuals. The data come from an annotated, longitudinal learner corpus. The development of lexicogrammatical complexity is explored at 2 intersections: (a) between cross-sectional trendlines…

  20. The Development of Second Language Writing Complexity in Groups and Individuals: A Longitudinal Learner Corpus Study

    ERIC Educational Resources Information Center

    Vyatkina, Nina

    2012-01-01

    This study explores the development of multiple dimensions of linguistic complexity in the writing of beginning learners of German both as a group and as individuals. The data come from an annotated, longitudinal learner corpus. The development of lexicogrammatical complexity is explored at 2 intersections: (a) between cross-sectional trendlines…

  1. Dynamic Development of Complexity and Accuracy: A Case Study in Second Language Academic Writing

    ERIC Educational Resources Information Center

    Rosmawati

    2014-01-01

    This paper reports on the development of complexity and accuracy in English as a Second Language (ESL) academic writing. Although research into complexity and accuracy development in second language (L2) writing has been well established, few studies have assumed the multidimensionality of these two constructs (Norris & Ortega, 2009) or…

  2. Gravity Waves and Convection in Colorado during July 1983.

    NASA Astrophysics Data System (ADS)

    Einaudi, F.; Clark, W. L.; Green, J. L.; Vanzandt, T. E.; Fua, D.

    1987-06-01

    In order to gain insight into the complex dynamics of a convective system interacting with a gravity wave train, we have carried out an experiment in northeast Colorado during July and August, 1983, utilizing data from several program areas in NOAA. Pressure data from the PROFS mesonetwork of microbarograph stations were combined with velocity profiles from the Wave Propagation Laboratory UHF wind profiler (ST) radar at Stapleton Airport in Denver and convective cell location data from the NWS Limon weather radar. Several events were clearly visible in the microbarograph data, from which four (called Events A, B, C and D) in late July were selected for further study. These events differed from each other in fundamental ways.In each event the waves represent oscillations of a substantial depth of the troposphere and seem to appear and disappear together with the convective cells. In Events A and B the waves have a critical level and are probably unstable modes generated by wind shear in the jet stream, from which they extract energy. We suggest that the convective cells cause the selection of some modes over others in a system that is initially dynamically unstable. In Event A the wave appears to be locked together with the convective cells, which move at the same velocity as the phase velocity of the wave. The wave and the cells seem to grow and evolve synergetically. In Event B the wave and convective cells commence at about the same time, but the cell velocities are quite different from the wave phase velocity. The cell velocities vary substantially over the time of the event and appear to be controlled by the local winds.In the Events C and D, the waves move faster than the maximum wind in the jet and at least twice as fast as the convective cells. It is suggested that these are nonsingular neutral modes whose excitation depends on a number of mechanisms, such as vertical convective motions and acceleration in the jet flow.

  3. Deep convection in the Arctic: The evaluation of results from an OGCM with a new convection parameterization

    SciTech Connect

    Paluszkiewicz, T.; Hibler, L.F.; Romea, R.D.

    1995-01-01

    The current generation of ocean general circulation models (OGCMS) uses a convective adjustment scheme to remove static instabilities and to parameterize shallow and deep convection. In simulations used to examine climate-related scenarios, investigators found that in the Arctic regions, the OGCM simulations did not produce a realistic vertical density structure, did not create the correct quantity of deep water, and did not use a time-scale of adjustment that is in agreement with tracer ages or observations. A possible weakness of the models is that the convective adjustment scheme does not represent the process of deep convection adequately. Consequently, a penetrative plume mixing scheme has been developed to parameterize the process of deep open-ocean convection in OGCMS. This new deep convection parameterization was incorporated into the Semtner and Chervin (1988) OGCM. The modified model (with the new parameterization) was run in a simplified Nordic Seas test basin: under a cyclonic wind stress and cooling, stratification of the basin-scale gyre is eroded and deep mixing occurs in the center of the gyre. In contrast, in the OGCM experiment that uses the standard convective adjustment algorithm, mixing is delayed and is wide-spread over the gyre.

  4. Convective vigour and heat flow in chemically differentiated systems

    NASA Astrophysics Data System (ADS)

    van Thienen, P.

    2007-05-01

    Parametric models of planets used to study their thermal evolution are generally based on scaling laws for purely thermal convection. However, planetary mantles may be chemically highly differentiated due to partial melting, which may form thick layers of depleted and dehydrated melting residue (e.g. continental roots). This results in inhomogeneity of density, which affects the driving force of convection, and viscosity (through the water content), which directly influences the dynamics of the system. This work investigates the applicability of scaling laws developed for purely thermally convecting systems to chemically differentiated systems representative of planetary mantles. The effects of depletion related buoyancy and melting related dehydration, and particularly the stratified convection patterns which may result from these, are considered. Two different strategies are applied to this end. First, a large number of numerical thermochemical convection experiments are performed, of which the dynamics and heat flow characteristics are studied. Secondly, theoretical approximations are developed from existing scaling laws to describe the heat flow of chemically stratified systems with separately convecting layers. These are tested using numerical simulations. The results show that the presence of a chemical stratification in the mantle may significantly alter heat flow patterns relative to a purely thermally convecting system by either influencing the thickness of the thermal boundary layer or dividing the convecting part of the system in vertically separate cells. This is consistent with recent petrological findings. Although the chemical stratification may be inherently instable against remixing, the present results suggest that the timescales of remixing may be much larger than those of thermal equilibration. Therefore, it is important to consider chemical stratification in thermal evolution models. For present-day Earth conditions and realistic rheological

  5. Stochastic parameterization of moist convection estimated from LES data

    NASA Astrophysics Data System (ADS)

    Dorrestijn, J.; Crommelin, D.; Biello, J. A.; Böing, S.; Siebesma, P.; Jonker, H. J.

    2012-12-01

    We report on the development of a methodology for stochastic parameterization of moist convection in General Circulation Models (GCMs), using the data-driven approach proposed by (1). We use data from convection-resolving Large-Eddy Simulation (LES) to estimate stochastic processes that represent convection. These stochastic processes take the form of Markov chains that are conditioned on the resolved scale state of the atmosphere. They mimic, in a computationally inexpensive manner, the convective behaviour observed in the LES. We explore cases of shallow and deep convection. In the first case we use LES data of shallow cumulus convection (2). The Markov chains switch between different vertical flux profiles of turbulent heat and moisture. We show that our model is able to reproduce the correct variability of the fluxes, i.e. close to the variability that is observed in the LES data. In the second case we use LES data of the development of deep convection (3). Here the Markov chains switch between different cloud types, similar to the multicloud model of Khouider et al. 2010 (4). Each Markov chain represents the cloud type (convective state) on small horizontal domain (in our case, 150 x 150 meter^2). By grouping these small domains in large blocks that match the size of a GCM grid box, the parameterization can be employed for GCM grid boxes of different sizes. The fractions of the various cloud types in these large blocks determine the total convective transport in each block. We show that the the evolution of the cloud fractions is well captured. We also demonstrate that nearest-neighbor coupling of the Markov chains improves the variability of the stochastically generated cloud fractions. Such spatially coupled Markov chains are equivalent to stochastic cellular automata. References: (1) Crommelin, D. & Vanden Eijnden, E. 2008 Subgrid-Scale Parametrization with Conditional Markov Chains. J. Atmos. Sci. 65, 2661--2675. (2) Dorrestijn, J., Crommelin, D

  6. A theory of nonlocal mixing-length convection. I - The moment formalism. [in stellar interior

    NASA Technical Reports Server (NTRS)

    Grossman, Scott A.; Narayan, Ramesh; Arnett, David

    1993-01-01

    A flexible and potentially powerful theory of convection, based on the mixing length picture, is developed to make unbiased self-consistent predictions about overshooting and other complicated phenomena in convection. The basic formalism is set up, and the method's power is demonstrated by showing that a simplified version of the theory reproduces all the standard results of local convection. The second-order equations of the theory are considered in the limit of a steady state and vanishing third moments, and it is shown that they reproduce all the standard results of local mixing-length convection. There is a particular value of the superadiabatic gradient, below which the only possible steady state of a fluid is nonconvecting. Above this critical value, a fluid is convectively unstable. Two distinct regimes of convection, which are identified as efficient and inefficient convection, are determined.

  7. A theory of nonlocal mixing-length convection. I - The moment formalism. [in stellar interior

    NASA Technical Reports Server (NTRS)

    Grossman, Scott A.; Narayan, Ramesh; Arnett, David

    1993-01-01

    A flexible and potentially powerful theory of convection, based on the mixing length picture, is developed to make unbiased self-consistent predictions about overshooting and other complicated phenomena in convection. The basic formalism is set up, and the method's power is demonstrated by showing that a simplified version of the theory reproduces all the standard results of local convection. The second-order equations of the theory are considered in the limit of a steady state and vanishing third moments, and it is shown that they reproduce all the standard results of local mixing-length convection. There is a particular value of the superadiabatic gradient, below which the only possible steady state of a fluid is nonconvecting. Above this critical value, a fluid is convectively unstable. Two distinct regimes of convection, which are identified as efficient and inefficient convection, are determined.

  8. Multicellular natural convection of a low Prandlt number fluid between horizontal concentric cylinders

    SciTech Connect

    Joosik Yoo; Jun Young Choi; Moonuhn Kim . Dept. of Mechanical Engineering)

    1994-01-01

    Two-dimensional natural convection of a fluid of low Prandtl number (Pr = 0.02) in an annulus between two concentric horizontal cylinders is numerically investigated in a wide range of gap widths. For low Grashof numbers, a steady unicellular convection is obtained. Above a transition Grashof number that depends on the gap width, a steady bicellular flow occurs. With further increase of the Grashof number, steady or time-periodic multicellular convection occurs, and finally, complex unsteady convective flow appears. A plot is presented that predicts the type of flow patterns for various combination of gap widths and Grashof numbers.

  9. Coupled radiative convective equilibrium simulations with explicit and parameterized convection

    NASA Astrophysics Data System (ADS)

    Hohenegger, Cathy; Stevens, Bjorn

    2016-09-01

    Radiative convective equilibrium has been applied in past studies to various models given its simplicity and analogy to the tropical climate. At convection-permitting resolution, the focus has been on the organization of convection that appears when using fixed sea surface temperature (SST). Here the SST is allowed to freely respond to the surface energy. The goals are to examine and understand the resulting transient behavior, equilibrium state, and perturbations thereof, as well as to compare these results to a simulation integrated with parameterized cloud and convection. Analysis shows that the coupling between the SST and the net surface energy acts to delay the onset of self-aggregation and may prevent it, in our case, for a slab ocean of less than 1 m. This is so because SST gradients tend to oppose the shallow low-level circulation that is associated with the self-aggregation of convection. Furthermore, the occurrence of self-aggregation is found to be necessary for reaching an equilibrium state and avoiding a greenhouse-like climate. In analogy to the present climate, the self-aggregation generates the dry and clear subtropics that allow the system to efficiently cool. In contrast, strong shortwave cloud radiative effects, much stronger than at convection-permitting resolution, prevent the simulation with parameterized cloud and convection to fall into a greenhouse state. The convection-permitting simulations also suggest that cloud feedbacks, as arising when perturbing the equilibrium state, may be very different, and in our case less negative, than what emerges from general circulation models.

  10. Developing integrated methods to address complex resource and environmental issues

    USGS Publications Warehouse

    Smith, Kathleen S.; Phillips, Jeffrey D.; McCafferty, Anne E.; Clark, Roger N.

    2016-02-08

    IntroductionThis circular provides an overview of selected activities that were conducted within the U.S. Geological Survey (USGS) Integrated Methods Development Project, an interdisciplinary project designed to develop new tools and conduct innovative research requiring integration of geologic, geophysical, geochemical, and remote-sensing expertise. The project was supported by the USGS Mineral Resources Program, and its products and acquired capabilities have broad applications to missions throughout the USGS and beyond.In addressing challenges associated with understanding the location, quantity, and quality of mineral resources, and in investigating the potential environmental consequences of resource development, a number of field and laboratory capabilities and interpretative methodologies evolved from the project that have applications to traditional resource studies as well as to studies related to ecosystem health, human health, disaster and hazard assessment, and planetary science. New or improved tools and research findings developed within the project have been applied to other projects and activities. Specifically, geophysical equipment and techniques have been applied to a variety of traditional and nontraditional mineral- and energy-resource studies, military applications, environmental investigations, and applied research activities that involve climate change, mapping techniques, and monitoring capabilities. Diverse applied geochemistry activities provide a process-level understanding of the mobility, chemical speciation, and bioavailability of elements, particularly metals and metalloids, in a variety of environmental settings. Imaging spectroscopy capabilities maintained and developed within the project have been applied to traditional resource studies as well as to studies related to ecosystem health, human health, disaster assessment, and planetary science. Brief descriptions of capabilities and laboratory facilities and summaries of some

  11. Forced convection in the wakes of sliding bubbles

    NASA Astrophysics Data System (ADS)

    Meehan, O'Reilly; Donnelly, B.; Persoons, T.; Nolan, K.; Murray, D. B.

    2016-09-01

    Both vapour and gas bubbles are known to significantly increase heat transfer rates between a heated surface and the surrounding fluid, even with no phase change. However, the complex wake structures means that the surface cooling is not fully understood. The current study uses high speed infra-red thermography to measure the surface temperature and convective heat flux enhancement associated with an air bubble sliding under an inclined surface, with a particular focus on the wake. Enhancement levels of 6 times natural convection levels are observed, along with cooling patterns consistent with a possible hairpin vortex structure interacting with the thermal boundary layer. Local regions of suppressed convective heat transfer highlight the complexity of the bubble wake in two-phase applications.

  12. Convection Effects in Three-dimensional Dendritic Growth

    NASA Technical Reports Server (NTRS)

    Lu, Yili; Beckermann, C.; Karma, A.

    2003-01-01

    A phase-field model is developed to simulate free dendritic growth coupled with fluid flow for a pure material in three dimensions. The preliminary results presented here illustrate the strong influence of convection on the three-dimensional (3D) dendrite growth morphology. The detailed knowledge of the flow and temperature fields in the melt around the dendrite from the simulations allows for a detailed understanding of the convection effects on dendritic growth.

  13. Modelling crystal growth: Convection in an asymmetrically heated ampoule

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.; Rosenberger, Franz; Pulicani, J. P.; Krukowski, S.; Ouazzani, Jalil

    1990-01-01

    The objective was to develop and implement a numerical method capable of solving the nonlinear partial differential equations governing heat, mass, and momentum transfer in a 3-D cylindrical geometry in order to examine the character of convection in an asymmetrically heated cylindrical ampoule. The details of the numerical method, including verification tests involving comparison with results obtained from other methods, are presented. The results of the study of 3-D convection in an asymmetrically heated cylinder are described.

  14. A System for Measurement of Convection Aboard Space Station

    NASA Technical Reports Server (NTRS)

    Bogatyrev, Gennady P.; Gorbunov, Aleksei V; Putin, Gennady F.; Ivanov, Alexander I.; Nikitin, Sergei A.; Polezhaev, Vadim I.

    1996-01-01

    A simple device for direct measurement of buoyancy driven fluid flows in a low-gravity environment is proposed. A system connecting spacecraft accelerometers data and results of thermal convection in enclosure measurements and numerical simulations is developed. This system will permit also to evaluate the low frequency microacceleration component. The goal of the paper is to present objectives and current results of ground-based experimental and numerical modeling of this convection detector.

  15. Exergetic simulation of a combined infrared-convective drying process

    NASA Astrophysics Data System (ADS)

    Aghbashlo, Mortaza

    2016-04-01

    Optimal design and performance of a combined infrared-convective drying system with respect to the energy issue is extremely put through the application of advanced engineering analyses. This article proposes a theoretical approach for exergy analysis of the combined infrared-convective drying process using a simple heat and mass transfer model. The applicability of the developed model to actual drying processes was proved using an illustrative example for a typical food.

  16. Atmospheric convective velocities and the Fourier phase spectrum

    NASA Technical Reports Server (NTRS)

    Cliff, W. C.

    1974-01-01

    The relationship between convective velocity and the Fourier phase spectrum of the cross correlation is developed. By examining the convective velocity as a function of frequency, one may determine if Taylor's conversion from time statistics to space statistics is valid. It is felt that the high shear regions of the atmospheric boundary layer need to be explored to determine the validity of the use of Taylor's hypothesis for this region.

  17. Dusty (complex) plasmas: recent developments, advances, and unsolved problems

    NASA Astrophysics Data System (ADS)

    Popel, Sergey

    The area of dusty (complex) plasma research is a vibrant subfield of plasma physics that be-longs to frontier research in physical sciences. This area is intrinsically interdisciplinary and encompasses astrophysics, planetary science, atmospheric science, magnetic fusion energy sci-ence, and various applied technologies. The research in dusty plasma started after two major discoveries in very different areas: (1) the discovery by the Voyager 2 spacecraft in 1980 of the radial spokes in Saturn's B ring, and (2) the discovery of the early 80's growth of contaminating dust particles in plasma processing. Dusty plasmas are ubiquitous in the universe; examples are proto-planetary and solar nebulae, molecular clouds, supernovae explosions, interplanetary medium, circumsolar rings, and asteroids. Within the solar system, we have planetary rings (e.g., Saturn and Jupiter), Martian atmosphere, cometary tails and comae, dust clouds on the Moon, etc. Close to the Earth, there are noctilucent clouds and polar mesospheric summer echoes, which are clouds of tiny (charged) ice particles that are formed in the summer polar mesosphere at the altitudes of about 82-95 km. Dust and dusty plasmas are also found in the vicinity of artificial satellites and space stations. Dust also turns out to be common in labo-ratory plasmas, such as in the processing of semiconductors and in tokamaks. In processing plasmas, dust particles are actually grown in the discharge from the reactive gases used to form the plasmas. An example of the relevance of industrial dusty plasmas is the growth of silicon microcrystals for improved solar cells in the future. In fact, nanostructured polymorphous sili-con films provide solar cells with high and time stable efficiency. These nano-materials can also be used for the fabrication of ultra-large-scale integration circuits, display devices, single elec-tron devices, light emitting diodes, laser diodes, and others. In microelectronic industries, dust has to be

  18. Structural development of the western Makran Accretionary Complex, Offshore Iran

    NASA Astrophysics Data System (ADS)

    Burberry, C. M.; Jackson, C. A.

    2013-12-01

    The Makran Accretionary Complex (MAC), which straddles the southern offshore regions of Iran and Pakistan, is a fold-thrust system bound by the Murray Ridge and Ornach Nal Fault to the east, and the Minab Fault System (MFS) to the west. It is c. 1000 km wide and the frontal c. 125 km of the system is submerged beneath the Gulf of Oman. Relatively little is known about this system, despite the fact that constitutes a large portion of the Central Tethyan Orogen and is one of the largest accretionary complexes in the world. We use offshore 2D seismic reflection data to investigate the structural style and evolution of the Iranian segment of the MAC. The MAC is divided into two morphologically distinct domains: (i) a northern domain (Domain 1), which is located landward of a prominant break-in-slope on the seabed and is characterised by a series of normal fault-bound sub-basins that are approximately 50 km wide, and which contain numerous, unconformity-bound seismic units; and (ii) a southern domain (Domain 2), which is located basinward of the prominent seabed slope break, and is characterised by alternating ridges and troughs. Seismic data indicate that these structures are laterally continuous (over 100 km long) north-dipping thrust faults, which are overlain by south-verging, non-cylindrical, fault-propagation folds. Towards the western end of the study area, immediately offshore of the prominent onshore trace of the MFS, there is no single structure that can be reliably interpreted as the offshore extension of the MFS. Instead, a series of oblique-slip faults with thrust and strike-slip components are identified, spanning a zone that is c. 40 km wide. In the north and close to the coastline, the faults are dominantly strike-slip, whereas further south, closer to the deformation front, the thrust-sense component is more important. Irrespective of their slip sense, faults in this zone have a similar N-S strike to the onshore trace of the MFS. In addition, the basin

  19. The Phenix ultimate natural convection test

    SciTech Connect

    Gauthe, P.; Pialla, D.; Tenchine, D.; Vasile, A.; Rochwerger, D.

    2012-07-01

    The French sodium cooled fast reactor Phenix was shut down in 2009 after 35 years of operation. Before decommissioning, a final set of tests were performed by the CEA during 9 months. Several topics were involved such as thermal hydraulics, core physics and fuel behaviour. Among these ultimate experiments, two thermal hydraulic tests were performed: an asymmetrical test consisting in a trip of one secondary pump and a natural convection test in the primary circuit. Recognizing the unique opportunity offered by these Phenix ultimate tests, IAEA decided in 2007 to launch a Coordinated Research Project (CRP) devoted to benchmarking analyses with system codes on the Phenix natural convection test. One objective of the natural convection test in Phenix reactor is the assessment of the CATHARE system code for safety studies on future and advanced sodium cooled fast reactors. The aim of this paper is to describe this test, which was performed on June 22-23, 2009, and the associated benchmark specifications for the CRP work. The paper reminds briefly the Phenix reactor with the main physical parameters and the instrumentation used during the natural convection test. After that, the test scenario is described: - initial state at a power of 120 MWth, - test beginning resulting from a manual dry out of the two steam generators, - manual scram, - manual trip on the three primary pumps without back-up by pony motors, - setting and development of natural convection in the primary circuit, in a first phase without significant heat sink in the secondary circuits and in a second phase with significant heat sink in the secondary circuits, by opening the casing of steam generators to create an efficient heat sink, by air natural circulation in the steam generators casing. The benchmark case ends after this second phase, which corresponds to the experimental test duration of nearly 7 hours. The paper presents also the benchmark specifications data supplied by the CEA to all

  20. Convection, nucleosynthesis, and core collapse

    NASA Technical Reports Server (NTRS)

    Bazan, Grant; Arnett, David

    1994-01-01

    We use a piecewise parabolic method hydrodynamics code (PROMETHEUS) to study convective burning in two dimensions in an oxygen shell prior to core collapse. Significant mixing beyond convective boundaries determined by mixing-length theory brings fuel (C-12) into the convective regon, causing hot spots of nuclear burning. Plumes dominate the velocity structure. Finite perturbations arise in a region in which O-16 will be explosively burned to Ni-56 when the star explodes; the resulting instabilities and mixing are likely to distribute Ni-56 throughout the supernova envelope. Inhomogeneities in Y(sub e) may be large enough to affect core collapse and will affect explosive nucleosynthesis. The nature of convective burning is dramatically different from that assumed in one-dimensional simulations; quantitative estimates of nucleosynthetic yields, core masses, and the approach to core collapse will be affected.

  1. Realistic Solar Surface Convection Simulations

    NASA Technical Reports Server (NTRS)

    Stein, Robert F.; Nordlund, Ake

    2000-01-01

    We perform essentially parameter free simulations with realistic physics of convection near the solar surface. We summarize the physics that is included and compare the simulation results with observations. Excellent agreement is obtained for the depth of the convection zone, the p-mode frequencies, the p-mode excitation rate, the distribution of the emergent continuum intensity, and the profiles of weak photospheric lines. We describe how solar convection is nonlocal. It is driven from a thin surface thermal boundary layer where radiative cooling produces low entropy gas which forms the cores of the downdrafts in which most of the buoyancy work occurs. We show that turbulence and vorticity are mostly confined to the intergranular lanes and underlying downdrafts. Finally, we illustrate our current work on magneto-convection.

  2. Convection and chaos in fluids

    SciTech Connect

    Bhattacharjee, J.

    1987-01-01

    This book describes some of the progress made in understanding the phenomena of various hydrodynamic instabilities for the past 30 years. Among them the exact results for the onset of Rayleigh-Benard convection are discussed. Approximate techniques like the amplitude equations and few-mode truncations are treated at length. The reviews of the routes to chaos in dynamical systems and the characteristics of the chaotic state are also discussed here. Finally, certain features of the Taylor Couette instability and the effect of parametric modulation on hydrodynamic instabilities are also included. This book also discusses the results at all stages of experiments. Contents: Onset of Convection: Rayleigh-Benard Geometry for Simple Fluids; Amplitude Equations; Few-Mode Truncation: Lorentz Model; Characteristics of Chaotic Behavior, Routes to Chaos; On Experiments; Thermohaline Systems; Onset of Convection; Binary Liquids; Nonlinear Effects; Taylor-Couette flow; Magnetohydrodynamic Convection; Modulated Systems.

  3. Dissolution test development for complex veterinary dosage forms: oral boluses.

    PubMed

    Fahmy, Raafat; Marnane, Bill; Bensley, Dennis; Hollenbeck, R Gary

    2002-01-01

    Fundamental aspects of electrolyte chemistry were used to design an appropriate dissolution medium with the capacity to maintain sink conditions throughout the test. Dissolution of various bolus dosage forms was studied using USP Apparatus II at various stirring speeds. Complete dissolution of each drug in the designed medium was achieved, and there is evidence that such a dissolution test could be discriminating. This review details the development of potentially discriminating in vitro dissolution tests for veterinary boluses using USP Apparatus II and examines the potential role of such testing during product quality assessments, in the evaluation of postapproval manufacturing changes and for the establishment of the generic equivalence of veterinary products.

  4. Parameterization of precipitating shallow convection

    NASA Astrophysics Data System (ADS)

    Seifert, Axel

    2015-04-01

    Shallow convective clouds play a decisive role in many regimes of the atmosphere. They are abundant in the trade wind regions and essential for the radiation budget in the sub-tropics. They are also an integral part of the diurnal cycle of convection over land leading to the formation of deeper modes of convection later on. Errors in the representation of these small and seemingly unimportant clouds can lead to misforecasts in many situations. Especially for high-resolution NWP models at 1-3 km grid spacing which explicitly simulate deeper modes of convection, the parameterization of the sub-grid shallow convection is an important issue. Large-eddy simulations (LES) can provide the data to study shallow convective clouds and their interaction with the boundary layer in great detail. In contrast to observation, simulations provide a complete and consistent dataset, which may not be perfectly realistic due to the necessary simplifications, but nevertheless enables us to study many aspects of those clouds in a self-consistent way. Today's supercomputing capabilities make it possible to use domain sizes that not only span several NWP grid boxes, but also allow for mesoscale self-organization of the cloud field, which is an essential behavior of precipitating shallow convection. By coarse-graining the LES data to the grid of an NWP model, the sub-grid fluctuations caused by shallow convective clouds can be analyzed explicitly. These fluctuations can then be parameterized in terms of a PDF-based closure. The necessary choices for such schemes like the shape of the PDF, the number of predicted moments, etc., will be discussed. For example, it is shown that a universal three-parameter distribution of total water may exist at scales of O(1 km) but not at O(10 km). In a next step the variance budgets of moisture and temperature in the cloud-topped boundary layer are studied. What is the role and magnitude of the microphysical correlation terms in these equations, which

  5. Big Data, Global Development, and Complex Social Systems

    NASA Astrophysics Data System (ADS)

    Eagle, Nathan

    2010-03-01

    Petabytes of data about human movements, transactions, and communication patterns are continuously being generated by everyday technologies such as mobile phones and credit cards. This unprecedented volume of information facilitates a novel set of research questions applicable to a wide range of development issues. In collaboration with the mobile phone, internet, and credit card industries, my colleagues and I are aggregating and analyzing behavioral data from over 250 million people from North and South America, Europe, Asia and Africa. I will discuss a selection of projects arising from these collaborations that involve inferring behavioral dynamics on a broad spectrum of scales; from risky behavior in a group of MIT freshman to population-level behavioral signatures, including cholera outbreaks in Rwanda and wealth in the UK. Access to the movement patterns of the majority of mobile phones in East Africa also facilitates realistic models of disease transmission as well as slum formations. This vast volume of data requires new analytical tools - we are developing a range of large-scale network analysis and machine learning algorithms that we hope will provide deeper insight into human behavior. However, ultimately our goal is to determine how we can use these insights to actively improve the lives of the billions of people who generate this data and the societies in which they live.

  6. Convective heat flow probe

    DOEpatents

    Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

    1985-01-01

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

  7. Convective heat flow probe

    DOEpatents

    Dunn, J.C.; Hardee, H.C.; Striker, R.P.

    1984-01-09

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packet-type seals are provided along the probe above and below the heater pads.

  8. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.

    1994-01-01

    The primary motivation for this research was to determine the cause for space processing altering the microstructure of some eutectics, especially the MnBi-Bi eutectic. Four primary hypotheses were to be tested under this current grant: (1) A fibrous microstructure is much more sensitive to convection than a lamellar microstructure, which was assumed in our prior theoretical treatment. (2) An interface with one phase projecting out into the melt is much more sensitive to convection than a planar interface, which was assumed in our prior theoretical treatment. (3) The Soret effect is much more important in the absence of convection and has a sufficiently large influence on microstructure that its action can explain the flight results. (4) The microstructure is much more sensitive to convection when the composition of the bulk melt is off eutectic. These hypotheses were tested. It was concluded that none of these can explain the Grumman flight results. Experiments also were performed on the influence of current pulses on MnBi-Bi microstructure. A thorough review was made of all experimental results on the influence of convection on the fiber spacing in rod eutectics, including results from solidification in space or at high gravity, and use of mechanical stirring or a magnetic field. Contradictory results were noted. The predictions of models for convective influences were compared with the experimental results. Vigorous mechanical stirring appears to coarsen the microstructure by altering the concentration field in front of the freezing interface. Gentle convection is believed to alter the microstructure of a fibrous eutectic only when it causes a fluctuating freezing rate with a system for which the kinetics of fiber branching differs from that for fiber termination. These fluctuations may cause the microstructure to coarsen or to become finer, depending on the relative kinetics of these processes. The microstructure of lamellar eutectics is less sensitive to

  9. Utilizing transmembrane convection to enhance solute sampling and delivery by microdialysis: theory and in vitro validation

    PubMed Central

    Bungay, Peter M.; Wang, Tianli; Yang, Hua; Elmquist, William F.

    2009-01-01

    Microdialysis is a well-developed membrane-based tool relying on diffusion to sample diffusible constituents of complex media, such as biological tissue. The objective of this research is to expand the utility of microdialysis by combining transmembrane convection with diffusion to enhance solute exchange between microdialysis probes and the surrounding medium. We have developed a mathematical model to describe probe performance and performed validation experiments utilizing tracer solutes and commercially available probes with 100-kDa molecular weight cutoff membranes. Diffusive and fluid permeabilities of the probe membranes are evaluated for probes immersed in well-stirred bathing media in vitro. Transmembrane convection alters the solute extraction fraction, i.e., the fractional loss of a solute from the probe perfusate during delivery and the fractional gain by the perfusate during sampling. The extraction fraction change depends upon the magnitude and direction (inward or outward) of fluid movement across the membrane. However, for solutes with zero reflection coefficients, equality is maintained between these delivery and sampling extraction fractions. This equality is a prerequisite for probe calibration approaches that rely on analyte delivery from the perfusate. Thus, we have provided the theoretical and experimental basis for exploiting convection in a quantitative manner to enhance solute delivery and sampling in microdialysis applications. PMID:20161534

  10. Studies of heat source driven natural convection

    NASA Technical Reports Server (NTRS)

    Kulacki, F. A.; Nagle, M. E.; Cassen, P.

    1974-01-01

    Natural convection energy transport in a horizontal layer of internally heated fluid with a zero heat flux lower boundary, and an isothermal upper boundary, has been studied. Quantitative information on the time-mean temperature distribution and the fluctuating component of temperature about the mean temperature in steady turbulent convection are obtained from a small thermocouple inserted into the layer through the upper bounding plate. Data are also presented on the development of temperature at several vertical positions when the layer is subject to both a sudden increase and to a sudden decrease in power input. For changes of power input from zero to a value corresponding to a Rayleigh number much greater than the critical linear stability theory value, a slight hysteresis in temperature profiles near the upper boundary is observed between the heat-up and cool-down modes.

  11. Eye formation in rotating convection

    NASA Astrophysics Data System (ADS)

    Oruba, L.; Davidson, P. A.; Dormy, E.

    2017-02-01

    We consider rotating convection in a shallow, cylindrical domain. We examine the conditions under which the resulting vortex develops an eye at its core; that is, a region where the poloidal flow reverses and the angular momentum is low. For simplicity, we restrict ourselves to steady, axisymmetric flows in a Boussinesq fluid. Our numerical experiments show that, in such systems, an eye forms as a passive response to the development of a so-called eyewall, a conical annulus of intense, negative azimuthal vorticity that can form near the axis and separates the eye from the primary vortex. We also observe that the vorticity in the eyewall comes from the lower boundary layer, and relies on the fact the poloidal flow strips negative vorticity out of the boundary layer and carries it up into the fluid above as it turns upward near the axis. This process is effective only if the Reynolds number is sufficiently high for the advection of vorticity to dominate over diffusion. Finally we observe that, in the vicinity of the eye and the eyewall, the buoyancy and Coriolis forces are negligible, and so although these forces are crucial to driving and shaping the primary vortex, they play no direct role in eye formation in a Boussinesq fluid.

  12. Gravitational effects on structure development in quenched complex fluids.

    PubMed

    Badalassi, V E; Ceniceros, H D; Banerjee, S

    2004-11-01

    When binary liquid mixtures are cooled rapidly from a homogeneous phase into a two-phase system, domains of the two equilibrium phases form and grow (coarsen) with time. In the absence of an external forcing due to gravity or an imposed shear flow, a dynamic scaling regime emerges in which the domain morphology is statistically self-similar at different times with a length-scale that grows with time. In the presence of gravity, however, multiple length scales develop, with the system coarsening more rapidly in the direction of the force. The late-time behavior of such a system is characterized in this study by the calculation of anisotropic growth laws. Gravitation effects significantly affect scaling laws, even with small density mismatch, and the growth mechanism has some similarities to the sedimentation process. However, very few numerical studies have been made of such effects; this is one of the first.

  13. Complex Challenges in the Less-Developed World

    NASA Astrophysics Data System (ADS)

    Webster, P. J.

    2016-12-01

    The developing world faces special challenges in a changing climate. The immediate impacts of possible increased precipitation, more frequent and severe hazard events and sea-level rise are compounded by lack of resources and, often, rapidly growing populations. We examine the concept that the society that learns to deal with hazards in the current climate will be best placed to deal with possibly more frequent and more intense hazards in the future. We use as an example the conundrum facing Bangladesh where global sea-level rise is exaggerated by delta subsidence of river sediment. Sedimentation is expected to increase with increased river flow. We explore how authorities may deal with these multifaceted threats and how they need to carefully thread a strategy that leads to solutions and not exaggerations of the problem.

  14. The roles of dry convection, cloud-radiation feedback processes and the influence of recent improvements in the parameterization of convection in the GLA GCM

    NASA Technical Reports Server (NTRS)

    Sud, Y.; Molod, A.

    1988-01-01

    The Goddard Laboratory for Atmospheres GCM is used to study the sensitivity of the simulated July circulation to modifications in the parameterization of dry and moist convection, evaporation from falling raindrops, and cloud-radiation interaction. It is shown that the Arakawa-Schubert (1974) cumulus parameterization and a more realistic dry convective mixing calculation yielded a better intertropical convergence zone over North Africa than the previous convection scheme. It is found that the physical mechanism for the improvement was the upward mixing of PBL moisture by vigorous dry convective mixing. A modified rain-evaporation parameterization which accounts for raindrop size distribution, the atmospheric relative humidity, and a typical spatial rainfall intensity distribution for convective rain was developed and implemented. This scheme led to major improvements in the monthly mean vertical profiles of relative humidity and temperature, convective and large-scale cloudiness, rainfall distributions, and mean relative humidity in the PBL.

  15. Isentropic Analysis of Convective Motions

    NASA Technical Reports Server (NTRS)

    Pauluis, Olivier M.; Mrowiec, Agnieszka A.

    2013-01-01

    This paper analyzes the convective mass transport by sorting air parcels in terms of their equivalent potential temperature to determine an isentropic streamfunction. By averaging the vertical mass flux at a constant value of the equivalent potential temperature, one can compute an isentropic mass transport that filters out reversible oscillatory motions such as gravity waves. This novel approach emphasizes the fact that the vertical energy and entropy transports by convection are due to the combination of ascending air parcels with high energy and entropy and subsiding air parcels with lower energy and entropy. Such conditional averaging can be extended to other dynamic and thermodynamic variables such as vertical velocity, temperature, or relative humidity to obtain a comprehensive description of convective motions. It is also shown how this approach can be used to determine the mean diabatic tendencies from the three-dimensional dynamic and thermodynamic fields. A two-stream approximation that partitions the isentropic circulation into a mean updraft and a mean downdraft is also introduced. This offers a straightforward way to identify the mean properties of rising and subsiding air parcels. The results from the two-stream approximation are compared with two other definitions of the cloud mass flux. It is argued that the isentropic analysis offers a robust definition of the convective mass transport that is not tainted by the need to arbitrarily distinguish between convection and its environment, and that separates the irreversible convective overturning fromoscillations associated with gravity waves.

  16. Feedback Control of Marangoni-BÉnard Convection

    NASA Astrophysics Data System (ADS)

    Bau, Haim

    1998-11-01

    It is demonstrated theoretically that control strategies, similar to the ones previously developed by Tang & Bau (Tang, J., & Bau, H. H., 1994, Proceedings Royal Society A, 447, 587-607.) (Tang, J., & Bau, H. H., 1998, J. Fluid Mechanics, 363, 153-171.) (Tang, J., & Bau, H. H., 1998, Physics of Fluids, 10, 1597-1610.) for postponing the transition from the conduction to the motion state in Rayleigh-Bénard convection, can also be used to delay the transition from the no-motion state to convection in the Marangoni-Bénard problem of an infinite fluid layer with a deformable surface and heating from below. For relatively small and moderate controller gains, the critical Marangoni number for the onset of convection increases monotonically as the controller gain increases and the principle of exchange of stability is preserved. Large controller gains induce oscillatory convection.

  17. Convection-enhanced delivery to the central nervous system.

    PubMed

    Lonser, Russell R; Sarntinoranont, Malisa; Morrison, Paul F; Oldfield, Edward H

    2015-03-01

    Convection-enhanced delivery (CED) is a bulk flow-driven process. Its properties permit direct, homogeneous, targeted perfusion of CNS regions with putative therapeutics while bypassing the blood-brain barrier. Development of surrogate imaging tracers that are co-infused during drug delivery now permit accurate, noninvasive real-time tracking of convective infusate flow in nervous system tissues. The potential advantages of CED in the CNS over other currently available drug delivery techniques, including systemic delivery, intrathecal and/or intraventricular distribution, and polymer implantation, have led to its application in research studies and clinical trials. The authors review the biophysical principles of convective flow and the technology, properties, and clinical applications of convective delivery in the CNS.

  18. The development and application of composite complexity models and a relative complexity metric in a software maintenance environment

    NASA Technical Reports Server (NTRS)

    Hops, J. M.; Sherif, J. S.

    1994-01-01

    A great deal of effort is now being devoted to the study, analysis, prediction, and minimization of software maintenance expected cost, long before software is delivered to users or customers. It has been estimated that, on the average, the effort spent on software maintenance is as costly as the effort spent on all other software costs. Software design methods should be the starting point to aid in alleviating the problems of software maintenance complexity and high costs. Two aspects of maintenance deserve attention: (1) protocols for locating and rectifying defects, and for ensuring that noe new defects are introduced in the development phase of the software process; and (2) protocols for modification, enhancement, and upgrading. This article focuses primarily on the second aspect, the development of protocols to help increase the quality and reduce the costs associated with modifications, enhancements, and upgrades of existing software. This study developed parsimonious models and a relative complexity metric for complexity measurement of software that were used to rank the modules in the system relative to one another. Some success was achieved in using the models and the relative metric to identify maintenance-prone modules.

  19. Convection wave studies over land and sea

    NASA Technical Reports Server (NTRS)

    Kuettner, Joachim; Grossmann, Robert

    1991-01-01

    Preliminary results of recent case studies conducted over land and sea are given. Two dimensional convection (roll vortex/cloudstreet) and three dimensional convection in the underlying boundary layer are dealt with. Vertical momentum flux profiles and time series of important parameters and vertical soundings taken in the experiment area are shown. The three cases described show that convection waves occur over land and over ocean, over three dimensional convection and over two dimensional convection.

  20. Observation of deep convection initiation from shallow convection environment

    NASA Astrophysics Data System (ADS)

    Lothon, Marie; Couvreux, Fleur; Guichard, Françoise; Campistron, Bernard; Chong, Michel; Rio, Catherine; Williams, Earle

    2010-05-01

    In the afternoon of 10 July 2006, deep convective cells initiated right in the field of view of the Massachusetts Institute Technology (MIT) C-band Doppler radar. This radar, with its 3D exploration at 10 min temporal resolution and 250 m radial resolution, allows us to track the deep convective cells and also provides clear air observations of the boundary layer structure prior to deep convection initiation. Several other observational platforms were operating then which allow us to thoroughly analyse this case: Vertically pointing aerosol lidar, W-band radar and ceilometer from the ARM Mobile Facility, along with radiosoundings and surface measurements enable us to describe the environment, from before their initiation to after the propagation of of one propagating cell that generated a circular gust front very nicely caught by the MIT radar. The systems considered here differ from the mesoscale convective systems which are often associated with African Easterly Waves, increasing CAPE and decreasing CIN. The former have smaller size, and initiate more locally, but there are numerous and still play a large role in the atmospheric circulation and scalar transport. Though, they remain a challenge to model. (See the presentation by Guichard et al. in the same session, for a model set up based on the same case, with joint single-column model and Large Eddy Simulation, which aims at better understanding and improving the parametrisation of deep convection initiation.) Based on the analysis of the observations mentioned above, we consider here the possible sources of deep convection initiation that day, which showed a typical boundary-layer growth in semi-arid environment, with isolated deep convective events.

  1. Control of the taeniosis/cysticercosis complex: future developments.

    PubMed

    Flisser, Ana; Rodríguez-Canul, Rossanna; Willingham, Arve Lee

    2006-07-31

    Cysticercosis is due to the establishment of the larval stage of the zoonotic cestode parasite Taenia solium. The infection causes substantial human morbidity and mortality, particularly in several Latin American countries and parts of Africa and Asia, as well as economic losses in pig husban dry due to condemnation of infected pork meat. The life cycle of T. solium includes human beings as definitive hosts and pigs as intermediate hosts. Cysticercosis is acquired by the ingestion of eggs released by human tapeworm carriers, who become infected after ingesting pork meat contaminated with cysticerci. Taenia solium transmission has been associated with poverty, lack of sanitary services and practices of rearing backyard pigs with free access to the areas that villagers use as toilets, as well as cultural behaviour. Nonetheless, due to the recent increase of migration and tourism, industrial countries are also reporting cases of human cysticercosis. There are many epidemiological studies that have been conducted mainly in Latin American countries that have evaluated intervention measures for control of cysticercosis including the development and testing of vaccines. Furthermore, the involvement of international agencies and institutions, such as the World Health Organization, the Food and Agriculture Organization and the International Livestock Research Institute, as well as the commitment of policymakers, scientists and field workers, are key means for the sustainable control and, hopefully, eradication of T. solium infections.

  2. Development of a knowledge management system for complex domains.

    PubMed

    Perott, André; Schader, Nils; Bruder, Ralph; Leonhardt, Jörg

    2012-01-01

    Deutsche Flugsicherung GmbH, the German Air Navigation Service Provider, follows a systematic approach, called HERA, for investigating incidents. The HERA analysis shows a distinctive occurrence of incidents in German air traffic control in which the visual perception of information plays a key role. The reasons can be partially traced back to workstation design, where basic ergonomic rules and principles are not sufficiently followed by the designers in some cases. In cooperation with the Institute of Ergonomics in Darmstadt the DFS investigated possible approaches that may support designers to implement ergonomic systems. None of the currently available tools were found to be able to meet the identified user requirements holistically. Therefore it was suggested to develop an enhanced software tool called Design Process Guide. The name Design Process Guide indicates that this tool exceeds the classic functions of currently available Knowledge Management Systems. It offers "design element" based access, shows processual and content related topics, and shows the implications of certain design decisions. Furthermore, it serves as documentation, detailing why a designer made to a decision under a particular set of conditions.

  3. Development of a complex intervention to improve health literacy skills

    PubMed Central

    Austvoll-Dahlgren, Astrid; Danielsen, Stein; Opheim, Elin; Bjørndal, Arild; Reinar, Liv Merete; Flottorp, Signe; Oxman, Andrew David; Helseth, Sølvi

    2013-01-01

    Background Providing insight into the developmental processes involved in building interventions is an important way to ensure methodological transparency and inform future research efforts. The objective of this study was to describe the development of a web portal designed to improve health literacy skills among the public. Methods The web portal was tailored to address three key barriers to obtaining information, using the conceptual frameworks of shared decision-making and evidence-based practice and based on explicit criteria for selecting the content and form of the intervention. Results The web portal targeted the general public and took the form of structured sets of tools. Content included: an introduction to research methods, help on how to find evidence-based health information efficiently based on the steps of evidence-based practice, an introduction to critical appraisal, information about patient participation rights in decision-making, and a decision aid for consultations. Conclusions The web portal was designed in a systematic and transparent way and address key barriers to obtaining and acting upon reliable health information. The web portal provides open access to the tools and can be used independently by health care users, or during consultations with health professionals. PMID:24251890

  4. Magnetic fields in non-convective regions of stars.

    PubMed

    Braithwaite, Jonathan; Spruit, Henk C

    2017-02-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them; the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and their observational effects are examined. We look at possible dynamo mechanisms that run on differential rotation rather than convection. Finally, we turn to neutron stars with a discussion of the possible origins for their magnetic fields.

  5. Magnetic fields in non-convective regions of stars

    PubMed Central

    Braithwaite, Jonathan

    2017-01-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them; the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and their observational effects are examined. We look at possible dynamo mechanisms that run on differential rotation rather than convection. Finally, we turn to neutron stars with a discussion of the possible origins for their magnetic fields. PMID:28386410

  6. Magnetic fields in non-convective regions of stars

    NASA Astrophysics Data System (ADS)

    Braithwaite, Jonathan; Spruit, Henk C.

    2017-02-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them; the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and their observational effects are examined. We look at possible dynamo mechanisms that run on differential rotation rather than convection. Finally, we turn to neutron stars with a discussion of the possible origins for their magnetic fields.

  7. Precursors to Language Development in Typically and Atypically Developing Infants and Toddlers: The Importance of Embracing Complexity

    ERIC Educational Resources Information Center

    D'Souza, Dean; D'Souza, Hana; Karmiloff-Smith, Annette

    2017-01-01

    In order to understand how language abilities emerge in typically and atypically developing infants and toddlers, it is important to embrace complexity in development. In this paper, we describe evidence that early language development is an experience-dependent process, shaped by diverse, interconnected, interdependent developmental mechanisms,…

  8. Examining the Roles of Deep Convective Detrainment in a Warming Environment

    NASA Astrophysics Data System (ADS)

    Storer, R. L.; Stephens, G. L.; van den Heever, S.

    2016-12-01

    Deep convection has been shown through modeling and observations to play a crucial role in circulations at many scales, and thus it is important to understand how convection may be affected by a changing climate. Detrainment from deep convective updrafts moistens the troposphere, promoting the development of future clouds, both convective and stratiform. This moistening is an important source of cirrus clouds, and the radiative effect of these clouds plays a critical role in the energy budget of the atmosphere. On the global or synoptic scale, links can be traced between deep convective clouds and large scale patterns of cloudiness (e.g. the Hadley Cell or the Madden-Julian oscillation); while on a more local scale, organized convection sets up low- and mid-level convection through circulations involving updrafts, downdrafts, detrainment, and cold pool forcing. Our goal is to investigate the role of deep convective detrainment in a warming environment within the framework of radiative-convective equilibrium (RCE). We have completed three-dimensional cloud resolving model simulations of the tropical atmosphere in RCE at three different sea surface temperatures to examine the behavior of convection. As sea surface temperature increases, convection becomes deeper and stronger, with larger values of both updrafts and downdrafts. These stronger convective storms have greater amounts of ice and precipitation, and the water budgets are more active overall, leading to larger amounts of condensate being detrained out to the surroundings. We will describe links between convective detrainment and processes on various scales. Sub-grid processes (namely microphysics) are inextricably linked to storm dynamics and the characteristics of detrained ice. On a cloud scale, we will examine the storm characteristics as they relate to convective strength, and the link between detrainment and precipitation efficiency. We will attempt to elucidate the effects of increased detrainment on

  9. Scaling evaluation of the effect of surface characteristics on potential for deep convection over uniform terrain

    NASA Technical Reports Server (NTRS)

    Segal, M.; Arritt, R. W.; Clark, C.; Rabin, R.; Brown, J.

    1995-01-01

    The effect of surface characteristics on the daytime change in the potential for development of deep convection resulting from surface flux of heat and moisture is evaluated by conceptual, scaling, and numerical modeling approaches. It is shown that deep convection depends significantly on the Bowen ratio; for smaller Bowen ratio, the thermodynamic potential for deep convection increases. The elevation and the intensity of the capping stable layer have an opposing impact on deep convection: increasing moisture accumulation through evapotranspiration was supportive but was counteracted by the enhancement of dry entrainment. Based on an approximnate treatment of the effect of cloudiness on solar irradiance, it was found that development of fair weather cumulus has a secondary effect on deep convection potential. Observational and operational aspects of the influence of surface conditions on evapotranspiration and development of deep convection are presented.

  10. The Complex Trauma Questionnaire (ComplexTQ): development and preliminary psychometric properties of an instrument for measuring early relational trauma

    PubMed Central

    Maggiora Vergano, Carola; Lauriola, Marco; Speranza, Anna M.

    2015-01-01

    Research on the etiology of adult psychopathology and its relationship with childhood trauma has focused primarily on specific forms of maltreatment. This study developed an instrument for the